JP7602730B2 - Radiation-sensitive resin composition and method for forming resist pattern using same - Google Patents

Description

The present invention relates to a radiation-sensitive resin composition, a method for forming a resist pattern using the same, and a compound that can be used as a photoacid generator.

Photolithography techniques using resist compositions are used to form fine circuits in semiconductor elements. In a typical procedure, for example, a coating of the resist composition is exposed to radiation through a mask pattern to generate an acid, which is then catalyzed by a reaction that creates a difference in the solubility of the resin in alkaline or organic developers between exposed and unexposed areas, forming a resist pattern on a substrate.

The photolithography technology described above promotes finer patterns by using short-wavelength radiation such as ArF excimer lasers, and further by using liquid immersion lithography, in which exposure is performed with the space between the lens of the exposure device and the resist film filled with a liquid medium. Lithography using even shorter-wavelength radiation such as electron beams, X-rays, and EUV (extreme ultraviolet) is also being considered as a next-generation technology.

As exposure technology advances, attempts are being made to improve the sensitivity and resolution of photoacid generators, which are a major component of resist compositions. As a resist composition with pattern resolution on the micron to submicron level, a photosensitive composition has been proposed that contains a hydroxystyrene polymer with high plasma etching resistance and a photoacid generator in which the carbon bonded to a sulfonic acid group is a secondary or tertiary carbon (Patent Document 1).

In addition, in the ArF generation, resins having a less absorbent alicyclic structure as a protecting group are used instead of hydroxystyrene-based polymers. However, the photoacid generators used in combination with the above-mentioned hydroxystyrene-based polymers do not have sufficient acid strength to proceed with the deprotection of resins having an alicyclic structure. Therefore, photoacid generators in which the proximal carbon of the sulfonic acid group is substituted with fluorine have been put into practical use as photoacid generators that provide acids with sufficient acid strength for deprotection (Patent Document 2).

Japanese Patent Application Publication No. 10-10715 JP 2002-214774 A

In recent years, as resist patterns have become finer, there has been a demand for further improvements in the above resolution, and further improvements in resist performance, including sensitivity in the exposure process and line width roughness (LWR) performance, which indicates the variation in line width of the resist pattern, are also required. In particular, there is a demand for the above LWR performance to be achieved in parallel with high sensitivity. Furthermore, next-generation exposure technologies such as electron beam exposure also require resist performance that is equal to or better than the above. However, conventional radiation-sensitive resin compositions have not been able to achieve all of the properties at a sufficient level.

In light of these circumstances, the present invention aims to provide a radiation-sensitive resin composition that can exhibit excellent sensitivity, resolution and LWR performance at sufficient levels, even when next-generation exposure technology is applied, a method for forming a resist pattern using the same, and a sulfonium salt compound or photoacid generator that can be used therein.

As a result of extensive research into solving this problem, the inventors discovered that the above objective can be achieved by using a radiation-sensitive acid generator with a specific structure, and thus completed the present invention.

（式中、
Ｒ^ｆ１、及び、Ｒ^ｆ２は、それぞれ独立して、電子求引性基であって、
Ｒ^１、及び、Ｒ^２は、それぞれ独立して、有機基又は水酸基であって、
ｎは、０～２の整数であって、
ｌ１は、０～５＋２ｎの整数であって、ｌ１が２～５＋２ｎの場合には、複数のＲ^ｆ１は、一部又は全部が同一又は異なり、
ｍ１は、０～６の整数であって、ｍ１が２～６の場合には、複数のＲ^ｆ２は、一部又は全部が同一又は異なり、
ｐ１は、０～５＋２ｎの整数であって、ｐ１が２～５＋２ｎの場合には、複数のＲ^１は、一部又は全部が同一又は異なり、
ｑ１は、０～６の整数であって、ｑ１が２～６の場合には、複数のＲ^２は、一部又は全部が同一又は異なり、
ｌ１＋ｐ１は、０～５＋２ｎであって、
ｍ１＋ｑ１は、０～６であって、
ｌ１、又は、ｍ１の少なくとも１つは、１以上の整数であって、
Ｚ_１ ^－は、アニオンである。） That is, the present invention provides
The present invention relates to a radiation-sensitive resin composition comprising a sulfonium salt compound represented by the following formula (1), a resin containing a structural unit having an acid-dissociable group, and a solvent.

(Wherein,
R ^f1 and R ^f2 each independently represent an electron-withdrawing group,
R ¹ and R ² each independently represent an organic group or a hydroxyl group;
n is an integer from 0 to 2,
l1 is an integer of 0 to 5+2n, and when l1 is an integer of 2 to 5+2n, a plurality of R ^f1s are partly or entirely the same or different;
m1 is an integer of 0 to 6, and when m1 is an integer of 2 to 6, a plurality of R ^f2 are partly or entirely the same or different;
p1 is an integer of 0 to 5+2n, and when p1 is an integer of 2 to 5+2n, a plurality of R ^1's are partly or entirely the same or different;
q1 is an integer of 0 to 6, and when q1 is an integer of 2 to 6, some or all of the R ^2's are the same or different;
l1+p1 is 0 to 5+2n,
m1+q1 is 0 to 6,
At least one of l1 or m1 is an integer of 1 or more,
Z ₁ ^- is an anion.

The radiation-sensitive resin composition of the present invention contains a sulfonium salt compound represented by the above formula (1), a resin containing a structural unit having an acid-dissociable group, and a solvent, and therefore is capable of exhibiting excellent levels of sensitivity and LWR performance in the exposure process.

（式中、
Ｒ^ｆ３、及び、Ｒ^ｆ４は、それぞれ独立して、電子求引性基であって、
Ｒ^３、及び、Ｒ^４は、それぞれ独立して、有機基又は水酸基であって、
ｌ２は、０～５の整数であって、ｌ２が２～５の場合には、複数のＲ^ｆ３は、一部又は全部が同一又は異なり、
ｍ２は、０～６の整数であって、ｍ２が２～６の場合には、複数のＲ^ｆ４は、一部又は全部が同一又は異なり、
ｐ２は、０～５の整数であって、ｐ２が２～５の場合には、複数のＲ^３は、一部又は全部が同一又は異なり、
ｑ２は、０～６の整数であって、ｑ２が２～６の場合には、複数のＲ^４は、一部又は全部が同一又は異なり、
ｌ２＋ｐ２は、０～５であって、
ｍ２＋ｑ２は、０～６であって、
ｌ２、又は、ｍ２の少なくとも１つは、１以上の整数であって、
Ｚ_２ ^－は、アニオンである。）
上記構成を有することにより、より確実にレジスト諸性能が向上したものとすることができる。 In the radiation-sensitive resin composition of the present invention, the sulfonium salt compound is preferably represented by the following general formula (2):

(Wherein,
R ^f3 and R ^f4 each independently represent an electron-withdrawing group,
R ³ and R ⁴ each independently represent an organic group or a hydroxyl group;
l2 is an integer of 0 to 5, and when l2 is an integer of 2 to 5, a plurality of R ^f3 are partly or entirely the same or different;
m2 is an integer of 0 to 6, and when m2 is an integer of 2 to 6, a plurality of R ^f4s are partly or entirely the same or different;
p2 is an integer of 0 to 5, and when p2 is an integer of 2 to 5, some or all of the R ^3's are the same or different;
q2 is an integer of 0 to 6, and when q2 is an integer of 2 to 6, some or all of the R ^4s are the same or different;
l2+p2 is 0 to 5,
m2+q2 is 0 to 6,
At least one of l2 or m2 is an integer of 1 or more,
Z ₂ ^- is an anion.
By having the above-mentioned constitution, various resist properties can be improved more reliably.

（式中、
Ｒ^ｆ５、及び、Ｒ^ｆ６は、それぞれ独立して、電子求引性基であって、
Ｒ^５、及び、Ｒ^６は、それぞれ独立して、有機基又は水酸基であって、
ｌ３は、０～７の整数であって、ｌ３が２～７の場合には、複数のＲ^ｆ５は、一部又は全部が同一又は異なり、
ｍ３は、０～６の整数であって、ｍ３が２～６の場合には、複数のＲ^ｆ６は、一部又は全部が同一又は異なり、
ｐ３は、０～７の整数であって、ｐ３が２～７の場合には、複数のＲ^５は、一部又は全部が同一又は異なり、
ｑ３は、０～６の整数であって、ｑ３が２～６の場合には、複数のＲ^６は、一部又は全部が同一又は異なり、
ｌ３＋ｐ３は、０～７であって、
ｍ３＋ｑ３は、０～６であって、
ｌ３、又は、ｍ３の少なくとも１つは、１以上の整数であって、
Ｚ_３ ^－は、アニオンである。）
上記構成を有することにより、より確実にレジスト諸性能が向上したものとすることができる。 In the radiation-sensitive resin composition of the present invention, another preferred example of the sulfonium salt compound is one represented by the following general formula (3).

(Wherein,
R ^f5 and R ^f6 each independently represent an electron-withdrawing group,
R ⁵ and R ⁶ each independently represent an organic group or a hydroxyl group;
l3 is an integer of 0 to 7, and when l3 is an integer of 2 to 7, a plurality of R ^f5s are partly or entirely the same or different;
m3 is an integer of 0 to 6, and when m3 is an integer of 2 to 6, a plurality of R ^f6 are partly or entirely the same or different;
p3 is an integer of 0 to 7, and when p3 is an integer of 2 to 7, some or all of the R ^5s are the same or different;
q3 is an integer of 0 to 6, and when q3 is an integer of 2 to 6, some or all of the R ^6s are the same or different;
l3+p3 is 0 to 7,
m3+q3 is 0 to 6,
At least one of l3 or m3 is an integer of 1 or more,
Z ₃ ^- is an anion.
By having the above-mentioned constitution, various resist properties can be improved more reliably.

In the radiation-sensitive resin composition of the present invention, the R ^f3 is preferably located at the para position relative to the thienyl cation bond. By having the above-mentioned structure, various resist properties can be improved more reliably.

In the radiation-sensitive resin composition of the present invention, the electron-withdrawing group preferably contains at least one alkyl group having 1 to 6 carbon atoms in which some or all of the hydrogen atoms have been substituted with halogen atoms, a halogen atom, an alkylsulfonyl group, a cyano group, or an arylsulfonyl group. By having the above-mentioned structure, various resist performances can be improved more reliably.

In addition, in the radiation-sensitive resin composition of the present invention, the halogen atom is preferably a fluorine atom. By having the above-mentioned structure, various resist properties can be more reliably improved.

In the radiation-sensitive resin composition of the present invention, the organic group preferably contains an optionally substituted alkyl group, hydroxyalkyl group, ester group , aldehyde group, ketone group, acetal group, ketal group, ether group, amide group, cycloalkyl group, or phenyl group. By having the above-mentioned structure, various resist performances can be improved more reliably.

In addition, in the radiation-sensitive resin composition of the present invention, the anion preferably has an acid anion moiety. By having the above-mentioned structure, various resist properties can be more reliably improved.

In addition, in the radiation-sensitive resin composition of the present invention, the acid anion moiety is preferably a sulfonate anion moiety, a carboxylate anion moiety, or a chloride ion moiety. By having the above-mentioned structure, various resist performances can be more reliably improved.

In addition, in the radiation-sensitive resin composition of the present invention, the content of the sulfonium salt compound is preferably 0.5 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the resin. By having the above-mentioned configuration, the resist performance can be more reliably improved.

On the other hand, the present invention is
A step (1) of forming a resist film from the radiation-sensitive resin composition;
The present invention relates to a method for forming a resist pattern, comprising: a step (2) of exposing the resist film to light; and a step (3) of developing the exposed resist film.

The method for forming a resist pattern of the present invention includes a step of forming a resist film by, for example, directly or indirectly applying a radiation-sensitive resin composition containing a sulfonium salt compound represented by the following formula (1), a resin containing a structural unit having an acid-dissociable group, and a solvent onto a substrate, thereby making it possible to achieve excellent levels of both sensitivity in the exposure step and line width roughness (LWR) performance, which indicates the variation in line width of the resist pattern.

In addition, in the resist pattern forming method of the present invention, it is preferable that the radiation used in the exposure step is ArF, extreme ultraviolet (EUV), X-rays, or electron beam (EB). By having the above configuration, the resist performance can be more reliably improved.

The present invention also relates to a method for processing a substrate, further comprising a step (4-1) of forming a pattern on a substrate using the resist pattern formed by the above method as a mask.

The present invention also relates to a method for producing a metal film pattern, which further includes a step (4-2) of forming a metal film using the resist pattern formed by the above method as a mask.

The substrate processing method and metal film pattern manufacturing method of the present invention include a step of forming a resist film, for example, by directly or indirectly applying a radiation-sensitive resin composition containing a sulfonium salt compound represented by the above-mentioned formula (1) below, a resin containing a structural unit having an acid-dissociable group, and a solvent onto a substrate, thereby making it possible to process high-quality substrate patterns and metal film patterns, respectively.

（式中、
Ｒ^ｆ１、及び、Ｒ^ｆ２は、それぞれ独立して、電子求引性基であって、
Ｒ^１、及び、Ｒ^２は、それぞれ独立して、有機基又は水酸基であって、
ｎは、０～２の整数であって、
ｌ１は、０～５＋２ｎの整数であって、ｌ１が２～５＋２ｎの場合には、複数のＲ^ｆ１は、一部又は全部が同一又は異なり、
ｍ１は、０～６の整数であって、ｍ１が２～６の場合には、複数のＲ^ｆ２は、一部又は全部が同一又は異なり、
ｐ１は、０～５＋２ｎの整数であって、ｐ１が２～５＋２ｎの場合には、複数のＲ^１は、一部又は全部が同一又は異なり、
ｑ１は、０～６の整数であって、ｑ１が２～６の場合には、複数のＲ^２は、一部又は全部が同一又は異なり、
ｌ１＋ｐ１は、０～５＋２ｎであって、
ｍ１＋ｑ１は、０～６であって、
ｌ１、又は、ｍ１の少なくとも１つは、１以上の整数であって、
Ｚ_１ ^－は、アニオンである。） On the other hand, the present invention is
The present invention relates to a sulfonium salt compound represented by the following formula (1).

(Wherein,
R ^f1 and R ^f2 each independently represent an electron-withdrawing group,
R ¹ and R ² each independently represent an organic group or a hydroxyl group;
n is an integer from 0 to 2,
l1 is an integer of 0 to 5+2n, and when l1 is an integer of 2 to 5+2n, a plurality of R ^f1s are partly or entirely the same or different;
m1 is an integer of 0 to 6, and when m1 is an integer of 2 to 6, a plurality of R ^f2 are partly or entirely the same or different;
p1 is an integer of 0 to 5+2n, and when p1 is an integer of 2 to 5+2n, a plurality of R ^1's are partly or entirely the same or different;
q1 is an integer of 0 to 6, and when q1 is an integer of 2 to 6, some or all of the R ^2's are the same or different;
l1+p1 is 0 to 5+2n,
m1+q1 is 0 to 6,
At least one of l1 or m1 is an integer of 1 or more,
Z ₁ ^- is an anion.

The sulfonium salt compound of the present invention is a sulfonium salt compound represented by the above formula (1), and therefore, for example, when a radiation-sensitive resin composition containing this is used, it is possible to achieve excellent levels of sensitivity and LWR performance in the exposure process.

（式中、
Ｒ^ｆ３、及び、Ｒ^ｆ４は、それぞれ独立して、電子求引性基であって、
Ｒ^３、及び、Ｒ^４は、それぞれ独立して、有機基又は水酸基であって、
ｌ２は、０～５の整数であって、ｌ２が２～５の場合には、複数のＲ^ｆ３は、一部又は全部が同一又は異なり、
ｍ２は、０～６の整数であって、ｍ２が２～６の場合には、複数のＲ^ｆ４は、一部又は全部が同一又は異なり、
ｐ２は、０～５の整数であって、ｐ２が２～５の場合には、複数のＲ^３は、一部又は全部が同一又は異なり、
ｑ２は、０～６の整数であって、ｑ２が２～６の場合には、複数のＲ^４は、一部又は全部が同一又は異なり、
ｌ２＋ｐ２は、０～５であって、
ｍ２＋ｑ２は、０～６であって、
ｌ２、又は、ｍ２の少なくとも１つは、１以上の整数であって、
Ｚ_２ ^－は、アニオンである。）
上記構成を有することにより、より確実にレジスト諸性能が向上したものとすることができる。 In the sulfonium salt compound of the present invention, the sulfonium salt compound represented by the following general formula (2) can be given as a preferred example.

(Wherein,
R ^f3 and R ^f4 each independently represent an electron-withdrawing group,
R ³ and R ⁴ each independently represent an organic group or a hydroxyl group;
l2 is an integer of 0 to 5, and when l2 is an integer of 2 to 5, a plurality of R ^f3 are partly or entirely the same or different;
m2 is an integer of 0 to 6, and when m2 is an integer of 2 to 6, a plurality of R ^f4s are partly or entirely the same or different;
p2 is an integer of 0 to 5, and when p2 is an integer of 2 to 5, some or all of the R ^3's are the same or different;
q2 is an integer of 0 to 6, and when q2 is an integer of 2 to 6, some or all of the R ^4s are the same or different;
l2+p2 is 0 to 5,
m2+q2 is 0 to 6,
At least one of l2 or m2 is an integer of 1 or more,
Z ₂ ^- is an anion.
By having the above-mentioned constitution, various resist properties can be improved more reliably.

（式中、
Ｒ^ｆ５、及び、Ｒ^ｆ６は、それぞれ独立して、電子求引性基であって、
Ｒ^５、及び、Ｒ^６は、それぞれ独立して、有機基又は水酸基であって、
ｌ３は、０～７の整数であって、ｌ３が２～７の場合には、複数のＲ^ｆ５は、一部又は全部が同一又は異なり、
ｍ３は、０～６の整数であって、ｍ３が２～６の場合には、複数のＲ^ｆ６は、一部又は全部が同一又は異なり、
ｐ３は、０～７の整数であって、ｐ３が２～７の場合には、複数のＲ^５は、一部又は全部が同一又は異なり、
ｑ３は、０～６の整数であって、ｑ３が２～６の場合には、複数のＲ^６は、一部又は全部が同一又は異なり、
ｌ３＋ｐ３は、０～７であって、
ｍ３＋ｑ３は、０～６であって、
ｌ３、又は、ｍ３の少なくとも１つは、１以上の整数であって、
Ｚ_３ ^－は、アニオンである。）
上記構成を有することにより、より確実にレジスト諸性能が向上したものとすることができる。 In addition, in the sulfonium salt compound of the present invention, the sulfonium salt compound represented by the following general formula (3) can be given as another preferred example.

(Wherein,
R ^f5 and R ^f6 each independently represent an electron-withdrawing group,
R ⁵ and R ⁶ each independently represent an organic group or a hydroxyl group;
l3 is an integer of 0 to 7, and when l3 is an integer of 2 to 7, a plurality of R ^f5s are partly or entirely the same or different;
m3 is an integer of 0 to 6, and when m3 is an integer of 2 to 6, a plurality of R ^f6 are partly or entirely the same or different;
p3 is an integer of 0 to 7, and when p3 is an integer of 2 to 7, some or all of the R ^5s are the same or different;
q3 is an integer of 0 to 6, and when q3 is an integer of 2 to 6, some or all of the R ^6s are the same or different;
l3+p3 is 0 to 7,
m3+q3 is 0 to 6,
At least one of l3 or m3 is an integer of 1 or more,
Z ₃ ^- is an anion.
By having the above-mentioned constitution, various resist properties can be improved more reliably.

In addition, in the sulfonium salt compound of the present invention, the above-mentioned ^Rf3 is preferably located at the para-position relative to the thienyl cation bond. By having the above-mentioned structure, various resist properties can be improved more reliably.

In addition, in the sulfonium salt compound of the present invention, the electron-withdrawing group preferably contains at least one alkyl group having 1 to 6 carbon atoms in which some or all of the hydrogen atoms are substituted with fluorine atoms, a halogen atom, an alkylsulfonyl group, or an arylsulfonyl group. By having the above-mentioned configuration, various resist performances can be improved more reliably.

The present invention also relates to a photoacid generator comprising the sulfonium salt compound described above.

Since the photoacid generator of the present invention is a sulfonium salt compound as described above, for example, when a radiation-sensitive resin composition containing this is used, it is possible to achieve excellent levels of sensitivity and LWR performance in the exposure process.

The following describes in detail the embodiments of the present invention, but the present invention is not limited to these embodiments.

（式中、
Ｒ^ｆ１、及び、Ｒ^ｆ２は、それぞれ独立して、電子求引性基であって、
Ｒ^１、及び、Ｒ^２は、それぞれ独立して、有機基又は水酸基であって、
ｎは、０～２の整数であって、
ｌ１は、０～５＋２ｎの整数であって、ｌ１が２～５＋２ｎの場合には、複数のＲ^ｆ１は、一部又は全部が同一又は異なり、
ｍ１は、０～６の整数であって、ｍ１が２～６の場合には、複数のＲ^ｆ２は、一部又は全部が同一又は異なり、
ｐ１は、０～５＋２ｎの整数であって、ｐ１が２～５＋２ｎの場合には、複数のＲ^１は、一部又は全部が同一又は異なり、
ｑ１は、０～６の整数であって、ｑ１が２～６の場合には、複数のＲ^２は、一部又は全部が同一又は異なり、
ｌ１＋ｐ１は、０～５＋２ｎであって、
ｍ１＋ｑ１は、０～６であって、
ｌ１、又は、ｍ１の少なくとも１つは、１以上の整数であって、
Ｚ_１ ^－は、アニオンである。） <Radiation-sensitive resin composition>
The radiation-sensitive resin composition of the present invention contains a sulfonium salt compound represented by the following formula (1), a resin containing a structural unit having an acid-dissociable group, and a solvent.

(Wherein,
R ^f1 and R ^f2 each independently represent an electron-withdrawing group,
R ¹ and R ² each independently represent an organic group or a hydroxyl group;
n is an integer from 0 to 2,
l1 is an integer of 0 to 5+2n, and when l1 is an integer of 2 to 5+2n, a plurality of R ^f1s are partly or entirely the same or different;
m1 is an integer of 0 to 6, and when m1 is an integer of 2 to 6, a plurality of R ^f2 are partly or entirely the same or different;
p1 is an integer of 0 to 5+2n, and when p1 is an integer of 2 to 5+2n, a plurality of R ^1's are partly or entirely the same or different;
q1 is an integer of 0 to 6, and when q1 is an integer of 2 to 6, some or all of the R ^2's are the same or different;
l1+p1 is 0 to 5+2n,
m1+q1 is 0 to 6,
At least one of l1 or m1 is an integer of 1 or more,
Z ₁ ^- is an anion.

The composition may contain other optional ingredients as long as they do not impair the effect of the present invention.

(Resin Containing a Structural Unit Having an Acid-Dissociable Group)
The resin containing a structural unit having an acid dissociable group in the present invention (hereinafter, also referred to as resin (A)) is, for example, an assembly of polymers having a structural unit (a1) having a phenolic hydroxyl group and a structural unit (a2) having an acid dissociable group containing a cyclic structure (hereinafter, this resin is also referred to as a "base resin").

Resin (A), which is the base resin, may have structural units other than the structural unit (a1) and the structural unit (a2). Each structural unit is described below.

[Structural unit (a1)]
The structural unit (a1) is a structural unit containing a phenolic hydroxyl group. The resin (A) can adjust the solubility in the developer more appropriately by having the structural unit (a1) and other structural units as necessary, and as a result, the LWR performance of the radiation-sensitive resin composition can be further improved. In addition, when KrF excimer laser light, EUV, electron beam, etc. are used as the radiation to be irradiated in the exposure step in the resist pattern forming method, the structural unit (a1) of the resin (A) contributes to improving the etching resistance and the difference in developer solubility (dissolution contrast) between the exposed and unexposed parts. In particular, it can be suitably applied to pattern formation using exposure to radiation with a wavelength of 50 nm or less, such as electron beam or EUV.

In addition, in the radiation-sensitive resin composition of the present invention, the above structural unit (a1) may be a structural unit derived from hydroxystyrene.

In the present invention, the structural unit derived from hydroxystyrene includes a structural unit that can be generated as a result of a bond-forming reaction such as addition polymerization of the carbon-carbon double bond of hydroxystyrene, and its equivalents. The structural unit that can be generated as a result of a bond-forming reaction such as addition polymerization of the carbon-carbon double bond of hydroxystyrene includes a structural unit in which the carbon-carbon double bond becomes a single bond as a result of a bond-forming reaction such as addition polymerization. In addition, as long as the structural unit becomes a single bond, it may be a structural unit formed by a method other than polymerization reaction of hydroxystyrene as a monomer, regardless of the synthesis method. For example, there can be mentioned a repeating structure of hydroxyphenyl units obtained by polymerizing a hydroxystyrene monomer protected by an alkali hydrolyzable group in the resin (A) and then hydrolyzing it, and a repeating structure obtained by polymerizing the hydroxystyrene monomer as it is.

Examples of the structural unit (a1) include a structural unit represented by the following formula (af):

In the above formula (af), R ^AF1 is a hydrogen atom or a methyl group. L ^AF is a single bond, -COO-, -O-, or -CONH-. R ^AF2 is a monovalent organic group having 1 to 20 carbon atoms. n _f1 is an integer of 0 to 3. When _{n f1} is 2 or 3, multiple R ^AF2 may be the same or different. n _f2 is an integer of 1 to 3. However, n _f1 +n _f2 is 5 or less. n _af is an integer of 0 to 2.

From the viewpoint of copolymerizability of the monomer that gives the structural unit (a1), R ^AF1 is preferably a hydrogen atom.

L ^AF is preferably a single bond or --COO--.

The organic group in resin (A) refers to a group containing at least one carbon atom.

Examples of the monovalent organic group having 1 to 20 carbon atoms represented by R ^AF2 include monovalent hydrocarbon groups having 1 to 20 carbon atoms, groups containing a divalent heteroatom-containing group between the carbon atoms of this hydrocarbon group or at the bond-side terminal, and groups in which some or all of the hydrogen atoms in the group and the hydrocarbon group have been substituted with monovalent heteroatom-containing groups.

Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by R ^AF2 include:
Alkyl groups such as a methyl group, an ethyl group, a propyl group, and a butyl group;
alkenyl groups such as ethenyl, propenyl, and butenyl;
Chain hydrocarbon groups such as alkynyl groups, e.g., ethynyl, propynyl, butynyl, etc.;
cycloalkyl groups such as a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, a cyclooctyl group, a norbornyl group, and an adamantyl group;
alicyclic hydrocarbon groups such as cycloalkenyl groups, such as a cyclopropenyl group, a cyclopentenyl group, a cyclohexenyl group, and a norbornenyl group;
Aryl groups such as a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and an anthryl group;
Examples include aromatic hydrocarbon groups such as aralkyl groups, eg, benzyl group, phenethyl group, and naphthylmethyl group.

R ^AF2 is preferably a chain hydrocarbon group or a cycloalkyl group, more preferably an alkyl group or a cycloalkyl group, and further preferably a methyl group, an ethyl group, a propyl group, a cyclopentyl group, a cyclohexyl group, a cyclooctyl group or an adamantyl group.

Examples of the divalent heteroatom-containing group include -O-, -CO-, -CO-O-, -S-, -CS-, -SO ₂ -, -NR'-, and groups formed by combining two or more of these, where R' is a hydrogen atom or a monovalent hydrocarbon group.

Examples of the monovalent heteroatom-containing group include halogen atoms such as fluorine, chlorine, bromine, and iodine atoms, hydroxyl groups, carboxyl groups, cyano groups, amino groups, and sulfanyl groups (-SH).

Among these, monovalent chain hydrocarbon groups are preferred, alkyl groups are more preferred, and methyl groups are even more preferred.

The above n _f1 is preferably an integer of 0 to 2, more preferably 0 or 1, and even more preferably 0.

The above _nf2 is preferably 1 or 2, and more preferably 1.

The above n _af is preferably 0 or 1, and more preferably 0.

The structural unit (a1) is preferably a structural unit represented by the following formulas (a1-1) to (a1-6), etc.

In the above formulas (a1-1) to (a1-6), R ^AF1 is the same as in the above formula (af).

Among these, structural units (a1-1) and (a1-2) are preferred, with (a1-1) being more preferred.

Regarding the structural unit (a1) in resin (A), the lower limit of the content of structural unit (a1) is preferably 10 mol%, more preferably 15 mol%, even more preferably 20 mol%, and particularly preferably 25 mol%, based on the total structural units constituting resin (A). The upper limit of the above content is preferably 90 mol%, more preferably 80 mol%, even more preferably 70 mol%, and particularly preferably 60 mol%. By setting the content of structural unit (a1) within the above range, the radiation-sensitive resin composition can further improve the LWR performance, etc.

When attempting to directly radically polymerize a monomer having a phenolic hydroxyl group such as hydroxystyrene, the polymerization may be inhibited by the influence of the phenolic hydroxyl group. In this case, it is preferable to polymerize the monomer in a state in which the phenolic hydroxyl group is protected by a protecting group such as an alkali dissociable group, and then to obtain the structural unit (a1) by deprotection through hydrolysis. The structural unit that gives the structural unit (a1) upon hydrolysis is preferably represented by the following formula (4).

In the above formula (4), R ¹¹ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R ¹² is a monovalent hydrocarbon group or alkoxy group having 1 to 20 carbon atoms. Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms for R ¹² include monovalent hydrocarbon groups having 1 to 20 carbon atoms. Examples of the alkoxy group include a methoxy group, an ethoxy group, and a tert-butoxy group.

As the above R ¹² , an alkyl group or an alkoxy group is preferable, and among them, a methyl group or a tert-butoxy group is more preferable.

[Structural unit (a2)]
The structural unit (a2) is a structural unit containing an acid dissociable group having a cyclic structure. The structural unit (a2) is not particularly limited as long as it contains an acid dissociable group having a cyclic structure, and examples thereof include a structural unit having a tertiary alkyl ester moiety, a structural unit having a structure in which a hydrogen atom of a phenolic hydroxyl group is substituted with a tertiary alkyl group, and a structural unit having an acetal bond. From the viewpoint of improving the pattern formability of the radiation-sensitive resin composition, a structural unit represented by the following formula (5) (hereinafter also referred to as "structural unit (a2-1)") is preferred.

In the present invention, the term "acid dissociable group" refers to a group that replaces a hydrogen atom in a carboxy group, a phenolic hydroxyl group, an alcoholic hydroxyl group, a sulfo group, or the like, and dissociates under the action of an acid. The radiation-sensitive resin composition has excellent pattern formability because the resin has the structural unit (a2).

In the above formula (5), R ⁷ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R ⁸ is a hydrogen atom, or a monovalent hydrocarbon group having 1 to 20 carbon atoms. R ⁹ and R ¹⁰ are each independently a monovalent linear hydrocarbon group having 1 to 10 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a divalent alicyclic group having 3 to 20 carbon atoms constituted by combining these groups together with the carbon atoms to which they are bonded. Note that, among R ⁸ to R ¹⁰ , a single one or a plurality of them are combined with each other to form at least one or more cyclic structures. L ¹ represents a single bond or a divalent linking group. However, when L ¹ is a divalent linking group, the structure on the side chain terminal side is -COO-.

From the viewpoint of copolymerizability of the monomer that gives the structural unit (a2-1), R ⁷ is preferably a hydrogen atom or a methyl group, and more preferably a methyl group.

Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by ^R8 include a chain hydrocarbon group having 1 to 10 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, and a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms.

Examples of the chain hydrocarbon group having 1 to 10 carbon atoms represented by R ⁸ to R ¹⁰ include linear or branched saturated hydrocarbon groups having 1 to 10 carbon atoms, and linear or branched unsaturated hydrocarbon groups having 1 to 10 carbon atoms.

Examples of the alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by R ⁸ to R ¹⁰ include monocyclic or polycyclic saturated hydrocarbon groups, and monocyclic or polycyclic unsaturated hydrocarbon groups. Preferred examples of the monocyclic saturated hydrocarbon group include cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups. Preferred examples of the polycyclic cycloalkyl group include bridged alicyclic hydrocarbon groups such as norbornyl, adamantyl, tricyclodecyl, and tetracyclododecyl groups. The bridged alicyclic hydrocarbon group refers to a polycyclic alicyclic hydrocarbon group in which two carbon atoms that are not adjacent to each other among the carbon atoms constituting the alicyclic ring are bonded by a bond chain containing one or more carbon atoms.

Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms represented by ^R8 include aryl groups such as a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and an anthryl group; and aralkyl groups such as a benzyl group, a phenethyl group, and a naphthylmethyl group.

The above R ⁸ is preferably a linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms, or an alicyclic hydrocarbon group having 3 to 20 carbon atoms.

When any two or more of the above R ⁸ to R ¹⁰ are combined with each other to form at least one or more cyclic structures, the divalent alicyclic group having 3 to 20 carbon atoms constituted by combining the chain hydrocarbon groups or alicyclic hydrocarbon groups with each other together with the carbon atoms to which they are bonded is not particularly limited as long as it is a group in which two hydrogen atoms are removed from the same carbon atom constituting a carbon ring of a monocyclic or polycyclic alicyclic hydrocarbon having the above carbon number. It may be either a monocyclic hydrocarbon group or a polycyclic hydrocarbon group, and the polycyclic hydrocarbon group may be either a bridged alicyclic hydrocarbon group or a condensed alicyclic hydrocarbon group, or it may be either a saturated hydrocarbon group or an unsaturated hydrocarbon group. The condensed alicyclic hydrocarbon group refers to a polycyclic alicyclic hydrocarbon group constituted in such a way that a plurality of alicyclic rings share a side (a bond between two adjacent carbon atoms).

Among the monocyclic alicyclic hydrocarbon groups, preferred saturated hydrocarbon groups include cyclopentanediyl, cyclohexanediyl, cycloheptanediyl, and cyclooctanediyl groups, while preferred unsaturated hydrocarbon groups include cyclopentenediyl, cyclohexenediyl, cycloheptenediyl, cyclooctenediyl, and cyclodecenediyl groups. Preferred polycyclic alicyclic hydrocarbon groups include bridged alicyclic saturated hydrocarbon groups, such as bicyclo[2.2.1]heptane-2,2-diyl (norbornane-2,2-diyl), bicyclo[2.2.2]octane-2,2-diyl, and tricyclo[3.3.1.1 ^3,7 ]decane-2,2-diyl (adamantane-2,2-diyl).

Examples of the divalent linking group represented by ^L1 include an alkanediyl group, a cycloalkanediyl group, an alkenediyl group, ^* -R ^LA O-, ^* -R ^LB COO-, etc. (* represents a bond on the oxygen side.) Some or all of the hydrogen atoms in these groups may be substituted with halogen atoms such as fluorine atoms or chlorine atoms, cyano groups, etc.

The alkanediyl group is preferably an alkanediyl group having 1 to 8 carbon atoms.

Examples of the cycloalkanediyl group include monocyclic cycloalkanediyl groups such as cyclopentanediyl and cyclohexanediyl groups; and polycyclic cycloalkanediyl groups such as norbornanediyl and adamantanediyl groups. The cycloalkanediyl group is preferably a cycloalkanediyl group having 5 to 12 carbon atoms.

Examples of the alkenediyl group include an ethenediyl group, a propenediyl group, and a butenediyl group. The alkenediyl group is preferably an alkenediyl group having 2 to 6 carbon atoms.

Examples of R ^LA in the above ^* -R ^LA O- include the above alkanediyl group, cycloalkanediyl group, alkenediyl group, etc. Examples of R ^LB in the above ^* -R ^LB COO- include the above alkanediyl group, cycloalkanediyl group, alkenediyl group, arenediyl group, etc. Examples of arenediyl groups include phenylene group, tolylene group, naphthylene group, etc. Examples of the arenediyl group include arenediyl groups having 6 to 15 carbon atoms.

Among these, it is preferable that ^R8 is an alkyl group having 1 to 4 carbon atoms, and the alicyclic structure formed by combining ^R9 and ^R10 together with the carbon atoms to which they are bonded is a polycyclic or monocyclic cycloalkane structure. It is preferable that ^L1 is a single bond or ^{* -RLAO-} . ^RLA is preferably an alkanediyl group.

Examples of the structural unit (a2-1) include structural units represented by the following formulas (2-1) to (2-4) (hereinafter also referred to as "structural units (a2-1-1) to (a2-1-4)").

In the above formulas (a2-1-1) to (a2-1-4), R ⁷ to R ¹⁰ are the same as those in the above formula (5). i and j each independently represent an integer of 1 to 4.

i and j are preferably 1. R ⁸ to R ¹⁰ are preferably a methyl group, an ethyl group, or an isopropyl group.

As the structural unit (a2-1), among these, the structural unit (a2-1-1) and the structural unit (a2-1-2) are preferred, a structural unit having a cyclopentane structure and a structural unit having an adamantane structure are more preferred, a structural unit derived from 1-alkylcyclopentyl (meth)acrylate and a structural unit derived from 2-alkyladamantyl (meth)acrylate are even more preferred, and a structural unit derived from 1-methylcyclohexyl (meth)acrylate and a structural unit derived from 2-ethyladamantyl (meth)acrylate are particularly preferred.

Resin (A) may contain one or a combination of two or more types of structural unit (a2).

The lower limit of the content of the structural unit (a2) is preferably 10 mol%, more preferably 15 mol%, even more preferably 20 mol%, and particularly preferably 30 mol%, based on all structural units constituting the base resin (A). The upper limit of the above content is preferably 90 mol%, more preferably 80 mol%, even more preferably 75 mol%, and particularly preferably 70 mol%. By setting the content of the structural unit (a2) within the above range, the pattern formability of the radiation-sensitive resin composition can be further improved.

[Structural unit (a3)]
The structural unit (a3) is a structural unit containing a lactone structure, a cyclic carbonate structure, a sultone structure, or a combination thereof. When the resin (A) further contains the structural unit (a3) in addition to the structural unit (a1) and the structural unit (a2), the polarity can be moderate. As a result, the radiation-sensitive resin composition can form a resist pattern that is finer and has excellent rectangular cross-sectional shape as a chemically amplified resist material. Here, the lactone structure refers to a structure having one ring (lactone ring) containing a group represented by -O-C(O)-. In addition, the cyclic carbonate structure refers to a structure having one ring (cyclic carbonate ring) containing a group represented by -O-C(O)-O-. The sultone structure refers to a structure having one ring (sultone ring) containing a group represented by -O-S(O) ₂ -.

Examples of structural unit (a3) include structural units represented by the following formula:

In the above formula, R ^AL is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

From the viewpoint of copolymerizability of the monomer that gives the structural unit (a3), R ^AL is preferably a hydrogen atom or a methyl group, and more preferably a methyl group.

As the structural unit (a3), among these, a structural unit containing a norbornane lactone structure, a structural unit containing an oxanorbornane lactone structure, a structural unit containing a gamma-butyrolactone structure, a structural unit containing an ethylene carbonate structure, and a structural unit containing a norbornane sultone structure are preferred, and a structural unit derived from norbornane lactone-yl (meth)acrylate, a structural unit derived from oxanorbornane lactone-yl (meth)acrylate, a structural unit derived from cyano-substituted norbornane lactone-yl (meth)acrylate, a structural unit derived from norbornane lactone-yl oxycarbonylmethyl (meth)acrylate, a structural unit derived from butyrolactone-3-yl (meth)acrylate, a butyrolactone ... More preferred are a structural unit derived from norbornane sultone-4-yl (meth)acrylate, a structural unit derived from 3,5-dimethylbutyrolactone-3-yl (meth)acrylate, a structural unit derived from 4,5-dimethylbutyrolactone-4-yl (meth)acrylate, a structural unit derived from 1-(butyrolactone-3-yl)cyclohexan-1-yl (meth)acrylate, a structural unit derived from ethylene carbonate-ylmethyl (meth)acrylate, a structural unit derived from cyclohexene carbonate-ylmethyl (meth)acrylate, a structural unit derived from norbornane sultone-yl (meth)acrylate, and a structural unit derived from norbornane sultone-yloxycarbonylmethyl (meth)acrylate.

When resin (A) has structural unit (a3), the lower limit of the content ratio of structural unit (a3) relative to all structural units constituting resin (A) is preferably 1 mol%, more preferably 10 mol%, even more preferably 20 mol%, and particularly preferably 25 mol%. On the other hand, the upper limit of the content ratio is preferably 70 mol%, more preferably 65 mol%, even more preferably 60 mol%, and particularly preferably 55 mol%. By setting the content ratio within the above range, the adhesion of the resist pattern formed from the radiation-sensitive resin composition to the substrate can be further improved.

[Structural unit (a4)]
Resin (A) may appropriately have a structural unit (also referred to as structural unit (a4)) other than the above structural units (a1) to (a3). Examples of the structural unit (a4) include structural units having a fluorine atom, an alcoholic hydroxyl group, a carboxy group, a cyano group, a nitro group, a sulfonamide group, and the like. Among these, a structural unit having a fluorine atom, a structural unit having an alcoholic hydroxyl group, and a structural unit having a carboxy group are preferred, and a structural unit having a fluorine atom and a structural unit having an alcoholic hydroxyl group are more preferred.

When the resin (A) has the structural unit (a4), the lower limit of the content ratio of the structural unit (a4) relative to all structural units constituting the resin (A) is preferably 1 mol%, more preferably 20 mol%, and even more preferably 40 mol%. On the other hand, the upper limit of the above content ratio is preferably 80 mol%, more preferably 75 mol%, and even more preferably 70 mol%. By setting the content ratio of the other structural units within the above range, the solubility of the resin (A) in the developer can be made more appropriate. If the content ratio of the other structural units exceeds the above upper limit, the pattern formability may be reduced.

In addition, in the resin (A) of the present invention, for example, (a) a repeating structure of hydroxyphenyl units obtained by polymerizing a hydroxystyrene monomer protected with an alkali hydrolyzable group and then hydrolyzing it, and (b) a repeating structure obtained by polymerizing a hydroxystyrene monomer as is, can both correspond to the above structural unit (a1). In addition, (c) a repeating structure obtained by polymerizing a hydroxystyrene monomer protected with an acid dissociable group can correspond to the above structural unit (a2) if the acid dissociable group is an "acid dissociable group containing a cyclic structure", and can correspond to the above structural unit (a4), which is a structural unit other than the above structural units (a1) to (a3), if the structure is a hydroxystyrene in which the hydroxyl group is protected by another acid dissociable group that does not contain a cyclic structure.

The content of resin (A) is preferably 70% by mass or more, more preferably 75% by mass or more, and even more preferably 80% by mass or more, of the total solid content of the radiation-sensitive resin composition. Here, "solid content" refers to all components contained in the radiation-sensitive resin composition excluding the solvent.

(Method of synthesizing resin (A))
The resin (A) serving as the base resin can be synthesized, for example, by carrying out a polymerization reaction of monomers which give the respective structural units in an appropriate solvent using a radical polymerization initiator or the like.

Examples of the radical polymerization initiator include azo radical initiators such as azobisisobutyronitrile (AIBN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and dimethyl 2,2'-azobisisobutyrate; and peroxide radical initiators such as benzoyl peroxide, t-butyl hydroperoxide, and cumene hydroperoxide. Among these, AIBN and dimethyl 2,2'-azobisisobutyrate are preferred, and AIBN is more preferred. These radical initiators can be used alone or in combination of two or more.

Examples of the solvents used in the polymerization reaction include alkanes such as n-pentane, n-hexane, n-heptane, n-octane, n-nonane, and n-decane; cycloalkanes such as cyclohexane, cycloheptane, cyclooctane, decalin, and norbornane; aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and cumene; halogenated hydrocarbons such as chlorobutanes, bromohexanes, dichloroethanes, hexamethylene dibromide, and chlorobenzene; saturated carboxylic acid esters such as ethyl acetate, n-butyl acetate, i-butyl acetate, and methyl propionate; ketones such as acetone, methyl ethyl ketone, 4-methyl-2-pentanone, and 2-heptanone; ethers such as tetrahydrofuran, dimethoxyethanes, and diethoxyethanes; and alcohols such as methanol, ethanol, 1-propanol, 2-propanol, and 4-methyl-2-pentanol. The solvents used in these polymerization reactions may be used alone or in combination of two or more.

The reaction temperature in the above polymerization reaction is usually 40°C to 150°C, preferably 50°C to 120°C. The reaction time is usually 1 hour to 48 hours, preferably 1 hour to 24 hours.

The molecular weight of the base resin (A) is not particularly limited, but the weight average molecular weight (Mw) calculated based on polystyrene standards by gel permeation chromatography (GPC) is preferably 1,000 to 50,000, more preferably 2,000 to 30,000, even more preferably 3,000 to 15,000, and particularly preferably 4,000 to 12,000. If the Mw of resin (A) is less than the lower limit, the heat resistance of the resulting resist film may decrease. If the Mw of resin (A) exceeds the upper limit, the developability of the resist film may decrease.

The ratio (Mw/Mn) of Mw to the polystyrene equivalent number average molecular weight (Mn) of the base resin (A) by GPC is usually 1 or more and 5 or less, preferably 1 or more and 3 or less, and more preferably 1 or more and 2 or less.

The Mw and Mn of the resin in this specification are values measured using gel permeation chromatography (GPC) under the following conditions.
GPC columns: 2 G2000HXL, 1 G3000HXL, 1 G4000HXL (all manufactured by Tosoh)
Column temperature: 40°C
Elution solvent: tetrahydrofuran Flow rate: 1.0 mL/min Sample concentration: 1.0% by mass
Sample injection volume: 100 μL
Detector: Differential refractometer Standard material: Monodisperse polystyrene

The content of resin (A) is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 85% by mass or more, based on the total solids content of the radiation-sensitive resin composition.

(Other resins)
The radiation-sensitive resin composition of the present embodiment may contain, as another resin, a resin having a higher mass content of fluorine atoms than the base resin (hereinafter, also referred to as a "high-fluorine content resin"). When the radiation-sensitive resin composition contains a high-fluorine content resin, the high-fluorine content resin can be unevenly distributed in the surface layer of the resist film relative to the base resin, and as a result, the state of the resist film surface and the component distribution in the resist film can be controlled to a desired state.

As the high fluorine content resin, for example, it is preferable that, in addition to the structural unit (a1) and the structural unit (a2) in the above-mentioned base resin, it also has a structural unit represented by the following formula (6) (hereinafter also referred to as "structural unit (a5)"):

In the above formula (6), R ¹³ is a hydrogen atom, a methyl group or a trifluoromethyl group. G is a single bond, an oxygen atom, a sulfur atom, -COO-, -SO ₂ ONH-, -CONH- or -OCONH-. R ¹⁴ is a monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms or a monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms.

From the viewpoint of copolymerizability of the monomer that gives the structural unit (a5), R ¹³ is preferably a hydrogen atom or a methyl group, and more preferably a methyl group.

From the viewpoint of copolymerizability of the monomer that gives the structural unit (a5), G ^L is preferably a single bond or --COO--, and more preferably --COO--.

Examples of the monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms represented by R ¹⁴ include linear or branched alkyl groups having 1 to 20 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms.

Examples of the monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by R ¹⁴ include monocyclic or polycyclic hydrocarbon groups having 3 to 20 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms.

R ¹⁴ is preferably a fluorinated chain hydrocarbon group, more preferably a fluorinated alkyl group, and further preferably a 2,2,2-trifluoroethyl group, a 1,1,1,3,3,3-hexafluoropropyl group or a 5,5,5-trifluoro-1,1-diethylpentyl group.

When the high fluorine content resin has the structural unit (a5), the lower limit of the content of the structural unit (a5) is preferably 10 mol%, more preferably 15 mol%, even more preferably 20 mol%, and particularly preferably 25 mol%, based on the total structural units constituting the high fluorine content resin. The upper limit of the content is preferably 60 mol%, more preferably 50 mol%, and even more preferably 40 mol%. By setting the content of the structural unit (a5) within the above range, the mass content of fluorine atoms in the high fluorine content resin can be more appropriately adjusted, and the uneven distribution of the fluorine atoms in the surface layer of the resist film can be further promoted.

The high fluorine content resin may have a fluorine atom-containing structural unit represented by the following formula (f-1) (hereinafter also referred to as structural unit (a6)) in addition to the structural unit (a5). By having the structural unit (f-1), the high fluorine content resin has improved solubility in an alkaline developer, and the occurrence of development defects can be suppressed.

The structural unit (a6) is roughly classified into two types: (x) a structural unit having an alkali-soluble group, and (y) a structural unit having a group that dissociates under the action of an alkali to increase the solubility in an alkali developer (hereinafter, also simply referred to as "alkali dissociable group"). In common to both (x) and (y), in the above formula (f-2), R ^C is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R ^D is a single bond, a (s+1)-valent hydrocarbon group having 1 to 20 carbon atoms, a structure in which an oxygen atom, a sulfur atom, -NR ^dd -, a carbonyl group, -COO-, or -CONH- is bonded to the end of the hydrocarbon group on the R ^E side, or a structure in which some of the hydrogen atoms of the hydrocarbon group are substituted with an organic group having a hetero atom. R ^dd is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. s is an integer from 1 to 3.

When the structural unit (a6) has an alkali-soluble group (x), R ^F is a hydrogen atom, and A ¹ is an oxygen atom, -COO-* or -SO ₂ O-*. * indicates the site bonding to R ^{F. W 1} is a single bond, a hydrocarbon group having 1 to 20 carbon atoms, or a divalent fluorinated hydrocarbon group. When ^{A 1} is an oxygen atom, W ¹ is a fluorinated hydrocarbon group having a fluorine atom or a fluoroalkyl group on the carbon atom to which A ¹ is bonded. R ^E is a single bond or a divalent organic group having 1 to 20 carbon atoms. When s is 2 or 3, a plurality of R ^{E s} , W ^{1 s} , A ^{1 s} and R ^{F s} may be the same or different. When the structural unit (a6) has an alkali-soluble group (x), it is possible to increase affinity for an alkaline developer and suppress development defects. (x) As the structural unit (a6) having an alkali-soluble group, it is particularly preferable that A ¹ is an oxygen atom and W ¹ is a 1,1,1,3,3,3-hexafluoro-2,2-methanediyl group.

When the structural unit (a6) has an alkali dissociable group (y), ^RF is a monovalent organic group having 1 to 30 carbon atoms, and A ¹ is an oxygen atom, -NR ^aa -, -COO-* or -SO ₂ O-*. R ^aa is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. * indicates the site bonding to ^RF . ^{W 1} is a single bond or a divalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. R ^E is a single bond or a divalent organic group having 1 to 20 carbon atoms. When ^{A 1} is -COO-* or -SO ₂ O-*, W ¹ or ^RF has a fluorine atom on the carbon atom bonding to A ¹ or on the carbon atom adjacent thereto. When A ¹ is an oxygen atom, W ¹ and R ^E are single bonds, R ^D is a structure in which a carbonyl group is bonded to the end of a hydrocarbon group having 1 to 20 carbon atoms on the R ^E side, and R ^F is an organic group having a fluorine atom. When s is 2 or 3, the multiple R ^{E s} , W ^{1 s} , A ^{1 s} , and R ^{F s} may be the same or different. When the structural unit (a6) has an alkali dissociable group (y), the surface of the resist film changes from hydrophobic to hydrophilic in the alkali development step. As a result, the affinity to the developer is significantly increased, and development defects can be more efficiently suppressed. As the structural unit (a6) having an alkali dissociable group (y), it is particularly preferable that A ¹ is -COO-*, and R ^F or W ¹ or both of them have a fluorine atom.

From the viewpoint of copolymerizability of the monomer that gives the structural unit (a6), R 3 ^C is preferably a hydrogen atom or a methyl group, and more preferably a methyl group.

When R 3 ^E is a divalent organic group, it is preferably a group having a lactone structure, more preferably a group having a polycyclic lactone structure, and even more preferably a group having a norbornane lactone structure.

When the high-fluorine content resin has the structural unit (a6), the lower limit of the content of the structural unit (a6) is preferably 10 mol%, more preferably 20 mol%, even more preferably 30 mol%, and particularly preferably 35 mol%, based on all structural units constituting the high-fluorine content resin. The upper limit of the above content is preferably 90 mol%, more preferably 75 mol%, and even more preferably 60 mol%. By setting the content of the structural unit (a6) within the above range, the water repellency of the resist film during immersion exposure can be further improved.

The lower limit of the Mw of the high fluorine content resin is preferably 1,000, more preferably 2,000, even more preferably 3,000, and particularly preferably 5,000. The upper limit of the Mw is preferably 50,000, more preferably 30,000, even more preferably 20,000, and particularly preferably 15,000.

The lower limit of Mw/Mn of the high fluorine content resin is usually 1, and more preferably 1.1. The upper limit of the above Mw/Mn is usually 5, and is preferably 3, more preferably 2, and even more preferably 1.7.

The lower limit of the content of the high fluorine content resin is preferably 0.1% by mass, more preferably 0.5% by mass, even more preferably 1% by mass, and even more preferably 1.5% by mass, based on the total solid content in the radiation-sensitive resin composition. The upper limit of the content is preferably 20% by mass, more preferably 15% by mass, even more preferably 10% by mass, and particularly preferably 7% by mass.

The lower limit of the content of the high fluorine content resin is preferably 0.1 parts by mass, more preferably 0.5 parts by mass, even more preferably 1 part by mass, and particularly preferably 1.5 parts by mass, relative to 100 parts by mass of the base resin. The upper limit of the content is preferably 15 parts by mass, more preferably 10 parts by mass, even more preferably 8 parts by mass, and particularly preferably 5 parts by mass.

By setting the content of the high fluorine content resin within the above range, the high fluorine content resin can be more effectively distributed on the surface layer of the resist film, and as a result, the water repellency of the surface of the resist film during immersion exposure can be further improved. The radiation-sensitive resin composition may contain one or more types of high fluorine content resins.

(Method of synthesizing high fluorine content resin)
The high fluorine content resin can be synthesized by the same method as the above-mentioned method for synthesizing the base resin.

（式中、
Ｒ^ｆ１、及び、Ｒ^ｆ２は、それぞれ独立して、電子求引性基であって、
Ｒ^１、及び、Ｒ^２は、それぞれ独立して、有機基又は水酸基であって、
ｎは、０～２の整数であって、
ｌ１は、０～５＋２ｎの整数であって、ｌ１が２～５＋２ｎの場合には、複数のＲ^ｆ１は、一部又は全部が同一又は異なり、
ｍ１は、０～６の整数であって、ｍ１が２～６の場合には、複数のＲ^ｆ２は、一部又は全部が同一又は異なり、
ｐ１は、０～５＋２ｎの整数であって、ｐ１が２～５＋２ｎの場合には、複数のＲ^１は、一部又は全部が同一又は異なり、
ｑ１は、０～６の整数であって、ｑ１が２～６の場合には、複数のＲ^２は、一部又は全部が同一又は異なり、
ｌ１＋ｐ１は、０～５＋２ｎであって、
ｍ１＋ｑ１は、０～６であって、
ｌ１、又は、ｍ１の少なくとも１つは、１以上の整数であって、
Ｚ_１ ^－は、アニオンである。） (Sulfonium salt compounds)
The sulfonium salt compound in the present invention is represented by the following formula (1).

(Wherein,
R ^f1 and R ^f2 each independently represent an electron-withdrawing group,
R ¹ and R ² each independently represent an organic group or a hydroxyl group;
n is an integer from 0 to 2,
l1 is an integer of 0 to 5+2n, and when l1 is an integer of 2 to 5+2n, a plurality of R ^f1s are partly or entirely the same or different;
m1 is an integer of 0 to 6, and when m1 is an integer of 2 to 6, a plurality of R ^f2 are partly or entirely the same or different;
p1 is an integer of 0 to 5+2n, and when p1 is an integer of 2 to 5+2n, a plurality of R ^1's are partly or entirely the same or different;
q1 is an integer of 0 to 6, and when q1 is an integer of 2 to 6, some or all of the R ^2's are the same or different;
l1+p1 is 0 to 5+2n,
m1+q1 is 0 to 6,
At least one of l1 or m1 is an integer of 1 or more,
Z ₁ ^- is an anion.

In the above formula (1), R ^f1 and R ^f2 each independently represent an electron-withdrawing group.

The electron-withdrawing group preferably contains at least one alkyl group having 1 to 6 carbon atoms in which some or all of the hydrogen atoms are substituted with halogen atoms, a halogen atom, an alkylsulfonyl group, or an arylsulfonyl group. When multiple groups are present, they may be used alone or in combination of two or more.

Examples of the alkyl group having 1 to 6 carbon atoms in which some or all of the hydrogen atoms are substituted with halogen atoms include methyl groups, ethyl groups, propyl groups, etc. in which some or all of the hydrogen atoms are substituted with halogen atoms.

Furthermore, a preferred example of the above halogen atom is a fluorine atom.

The alkylsulfonyl group is a group having a structure represented by -SO ₂ ^-Rs , where ^Rs can be an alkyl group or a cycloalkyl group. More specific examples include a methyl group, an ethyl group, a propyl group, a butyl group, a cyclopentyl group, a cyclohexyl group, a cyclooctyl group, a norbornyl group, an adamantyl group, a tetrahydrofuranyl group, or a tetrahydropyranyl group. When multiple groups are present, they may be used alone or in combination of two or more.

The arylsulfonyl group is a group having a structure represented by -SO ₂ -Ar ^s , where Ar ^s can be an aryl group or a heteroaryl group. More specific examples include a phenyl group, a naphthyl group, a pyrenyl group, a furyl group, a pyridinyl group, a carbazolyl group, etc. When a plurality of groups are present, they may be used alone or in combination of two or more.

Moreover, the above R ¹ and R ² each independently represent an organic group or a hydroxyl group.

Examples of the organic group R ¹ and R ² include an alkyl group, a hydroxyalkyl group, a cyano group, an ester group, an aldehyde group, a ketone group, an acetal group, a ketal group, an ether group, an amide group, a cycloalkyl group, or a phenyl group, which may be substituted. When a plurality of groups are present, they may be used alone or in combination of two or more.

Furthermore, n is an integer from 0 to 2.

Furthermore, the above l1 is an integer of 0 to 5+2n, and when l1 is an integer of 2 to 5+2n, some or all of the multiple R ^f1s are the same or different.

Moreover, the above m1 is an integer of 0 to 6, and when m1 is an integer of 2 to 6, some or all of the multiple R ^f2 are the same or different.

Furthermore, the above p1 is an integer of 0 to 5+2n, and when p1 is an integer of 2 to 5+2n, some or all of the multiple R ^1s are the same or different.

Furthermore, the above q1 is an integer of 0 to 6, and when q1 is an integer of 2 to 6, some or all of the multiple R ^2s are the same or different.

Also, the above l1+p1 is between 0 and 5+2n.

Also, m1+q1 is 0 to 6.

Furthermore, at least one of l1 or m1 is an integer greater than or equal to 1.

Z ₁ ⁻ is an anion. As the anion, anions used in known photoacid generators can be appropriately used.

In addition, a preferred example of the above anion is one having an acid anion moiety.

The acid anion moiety is preferably a sulfonate anion moiety, a carboxylate anion moiety, or a chloride ion moiety. As the sulfonate anion moiety, the carboxylate anion moiety, or the chloride ion moiety, a sulfonate anion moiety, a carboxylate anion moiety, or a chloride ion moiety used in a known photoacid generator can be appropriately used.

Examples of the anion having the sulfonate anion moiety include the following anions. These may be used alone or in combination of two or more.

Examples of the anion having the carboxylate anion moiety include the following anions. These may be used alone or in combination of two or more.

An example of the anion having the chloride ion moiety is Cl 2 ^- .

（式中、
Ｒ^ｆ３、及び、Ｒ^ｆ４は、それぞれ独立して、電子求引性基であって、
Ｒ^３、及び、Ｒ^４は、それぞれ独立して、有機基又は水酸基であって、
ｌ２は、０～５の整数であって、ｌ２が２～５の場合には、複数のＲ^ｆ３は、一部又は全部が同一又は異なり、
ｍ２は、０～６の整数であって、ｍ２が２～６の場合には、複数のＲ^ｆ４は、一部又は全部が同一又は異なり、
ｐ２は、０～５の整数であって、ｐ２が２～５の場合には、複数のＲ^３は、一部又は全部が同一又は異なり、
ｑ２は、０～６の整数であって、ｑ２が２～６の場合には、複数のＲ^４は、一部又は全部が同一又は異なり、
ｌ２＋ｐ２は、０～５であって、
ｍ２＋ｑ２は、０～６であって、
ｌ２、又は、ｍ２の少なくとも１つは、１以上の整数であって、
Ｚ_２ ^－は、アニオンである。） In the radiation-sensitive resin composition of the present invention, the sulfonium salt compound is preferably represented by the following general formula (2):

(Wherein,
R ^f3 and R ^f4 each independently represent an electron-withdrawing group,
R ³ and R ⁴ each independently represent an organic group or a hydroxyl group;
l2 is an integer of 0 to 5, and when l2 is an integer of 2 to 5, a plurality of R ^f3 are partly or entirely the same or different;
m2 is an integer of 0 to 6, and when m2 is an integer of 2 to 6, a plurality of R ^f4s are partly or entirely the same or different;
p2 is an integer of 0 to 5, and when p2 is an integer of 2 to 5, some or all of the R ^3's are the same or different;
q2 is an integer of 0 to 6, and when q2 is an integer of 2 to 6, some or all of the R ^4s are the same or different;
l2+p2 is 0 to 5,
m2+q2 is 0 to 6,
At least one of l2 or m2 is an integer of 1 or more,
Z ₂ ^- is an anion.

In the above formula (2), R ^f3 and R ^f4 each independently represent an electron-withdrawing group, and the electron-withdrawing group is the same as in the above formula (1).

R ³ and R ⁴ each independently represent an organic group or a hydroxyl group, and the organic group or hydroxyl group is the same as in the case of formula (1).

Furthermore, l2 is an integer of 0 to 5, and when l2 is an integer of 2 to 5, some or all of the multiple R ^f3s are the same or different.

Furthermore, m2 is an integer of 0 to 6, and when m2 is an integer of 2 to 6, some or all of the multiple R ^f4s are the same or different.

Furthermore, p2 is an integer of 0 to 5, and when p2 is an integer of 2 to 5, some or all of the multiple R ^3s are the same or different.

Furthermore, q2 is an integer of 0 to 6, and when q2 is an integer of 2 to 6, some or all of the multiple R ^4s are the same or different.

Also, l2+p2 is between 0 and 5.

Also, m2+q2 is 0 to 6.

Furthermore, at least one of l2 or m2 is an integer greater than or equal to 1.

Z ₂ ^- is an anion, and the anion is the same as in the case of formula (1).

Examples of the cation of the sulfonium salt compound represented by the above general formula (2) include the following cations. These may be used alone or in combination of two or more.

In the present invention, the case where ^Rf3 is at the para position relative to the thienyl cation bond can be mentioned as a preferred example. By having the above-mentioned structure, various resist properties can be improved more reliably.

（式中、
Ｒ^ｆ５、及び、Ｒ^ｆ６は、それぞれ独立して、電子求引性基であって、
Ｒ^５、及び、Ｒ^６は、それぞれ独立して、有機基又は水酸基であって、
ｌ３は、０～７の整数であって、ｌ３が２～７の場合には、複数のＲ^ｆ５は、一部又は全部が同一又は異なり、
ｍ３は、０～６の整数であって、ｍ３が２～６の場合には、複数のＲ^ｆ６は、一部又は全部が同一又は異なり、
ｐ３は、０～７の整数であって、ｐ３が２～７の場合には、複数のＲ^５は、一部又は全部が同一又は異なり、
ｑ３は、０～６の整数であって、ｑ３が２～６の場合には、複数のＲ^６は、一部又は全部が同一又は異なり、
ｌ３＋ｐ３は、０～７であって、
ｍ３＋ｑ３は、０～６であって、
ｌ３、又は、ｍ３の少なくとも１つは、１以上の整数であって、
Ｚ_３ ^－は、アニオンである。） In the radiation-sensitive resin composition of the present invention, another preferred example of the sulfonium salt compound is one represented by the following general formula (3).

(Wherein,
R ^f5 and R ^f6 each independently represent an electron-withdrawing group,
R ⁵ and R ⁶ each independently represent an organic group or a hydroxyl group;
l3 is an integer of 0 to 7, and when l3 is an integer of 2 to 7, a plurality of R ^f5s are partly or entirely the same or different;
m3 is an integer of 0 to 6, and when m3 is an integer of 2 to 6, a plurality of R ^f6 are partly or entirely the same or different;
p3 is an integer of 0 to 7, and when p3 is an integer of 2 to 7, some or all of the R ^5s are the same or different;
q3 is an integer of 0 to 6, and when q3 is an integer of 2 to 6, some or all of the R ^6s are the same or different;
l3+p3 is 0 to 7,
m3+q3 is 0 to 6,
At least one of l3 or m3 is an integer of 1 or more,
Z ₃ ^- is an anion.

In the formula (3), R ^f5 and R ^f6 each independently represent an electron-withdrawing group, and the electron-withdrawing group is the same as in the formula (1).

R ⁵ and R ⁶ each independently represent an organic group or a hydroxyl group. The organic group or hydroxyl group is the same as in the case of formula (1).

l3 is an integer of 0 to 7, and when l3 is an integer of 2 to 7, some or all of the multiple R ^f5s are the same or different.

Furthermore, m3 is an integer of 0 to 6, and when m3 is an integer of 2 to 6, some or all of the multiple R ^f6 are the same or different.

Furthermore, p3 is an integer of 0 to 7, and when p3 is an integer of 2 to 7, some or all of the multiple R ^5s are the same or different.

Furthermore, q3 is an integer of 0 to 6, and when q3 is an integer of 2 to 6, some or all of the multiple R ^6s are the same or different.

Also, l3 + p3 is between 0 and 7.

Also, m3+q3 is 0 to 6.

Furthermore, at least one of l3 or m3 is an integer greater than or equal to 1.

Z ₃ ^- is an anion, and the anion is the same as in the case of formula (1).

Examples of the cation of the sulfonium salt compound represented by the above general formula (3) include the following cations. These may be used alone or in combination of two or more.

In addition, in the radiation-sensitive resin composition of the present invention, other photoacid generators different from the above-mentioned sulfonium salt compounds may be used in appropriate combination. As the other photoacid generators, known photoacid generators can be used as appropriate.

In the present invention, the lower limit of the blending amount of the sulfonium salt compound (the total amount when multiple types are used) relative to 100 parts by mass of the radiation-sensitive resin composition is preferably 0.05 parts by mass, more preferably 0.1 parts by mass, and may be 1 part by mass or 2 parts by mass. On the other hand, the upper limit of the blending amount is preferably 100 parts by mass, more preferably 50 parts by mass, and may be 30 parts by mass, 20 parts by mass, or 10 parts by mass.

If the blend amount is less than the lower limit, the sensitivity may decrease. Conversely, if the blend amount or content ratio exceeds the upper limit, it may be difficult to form a resist film or the rectangularity of the cross-sectional shape of the resist pattern may decrease.

(solvent)
The radiation-sensitive resin composition contains a solvent. The solvent is not particularly limited as long as it is capable of dissolving or dispersing at least the resin, the radiation-sensitive acid generator, and the acid diffusion controller, which is optionally contained.

Examples of solvents include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

Examples of alcohol-based solvents include:
Monoalcohol solvents having 1 to 18 carbon atoms, such as isopropanol, 4-methyl-2-pentanol, 3-methoxybutanol, n-hexanol, 2-ethylhexanol, furfuryl alcohol, cyclohexanol, 3,3,5-trimethylcyclohexanol, and diacetone alcohol;
Polyhydric alcohol solvents having 2 to 18 carbon atoms, such as ethylene glycol, 1,2-propylene glycol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, and tripropylene glycol;
Examples of the polyhydric alcohol partially etherified solvents include those obtained by etherifying some of the hydroxy groups of the above polyhydric alcohol solvents.

Examples of ether solvents include:
Dialkyl ether solvents such as diethyl ether, dipropyl ether, and dibutyl ether;
Cyclic ether solvents such as tetrahydrofuran and tetrahydropyran;
Aromatic ring-containing ether solvents, such as diphenyl ether and anisole (methyl phenyl ether);
Examples of the polyhydric alcohol solvent include polyhydric alcohol ether solvents obtained by etherifying the hydroxyl groups of the above-mentioned polyhydric alcohol solvents.

Examples of the ketone solvent include chain ketone solvents such as acetone, butanone, and methyl-iso-butyl ketone:
Cyclic ketone solvents such as cyclopentanone, cyclohexanone, methylcyclohexanone, etc.:
Examples include 2,4-pentanedione, acetonylacetone, and acetophenone.

Examples of the amide solvent include cyclic amide solvents such as N,N'-dimethylimidazolidinone and N-methylpyrrolidone;
Examples of the solvent include chain amide solvents such as N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, and N-methylpropionamide.

Examples of ester-based solvents include:
Monocarboxylate solvents such as n-butyl acetate and ethyl lactate;
polyhydric alcohol partial ether acetate solvents, such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate;
Lactone solvents such as γ-butyrolactone and valerolactone;
Carbonate solvents such as diethyl carbonate, ethylene carbonate, and propylene carbonate;
Examples of the polyvalent carboxylic acid diester solvents include propylene glycol diacetate, methoxytriglycol acetate, diethyl oxalate, ethyl acetoacetate, ethyl lactate, and diethyl phthalate.

Examples of the hydrocarbon solvent include:
Aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane;
Examples of the solvent include aromatic hydrocarbon solvents such as benzene, toluene, di-iso-propylbenzene, and n-amylnaphthalene.

Among these, ester-based solvents and ketone-based solvents are preferred, polyhydric alcohol partial ether acetate-based solvents, cyclic ketone-based solvents, and lactone-based solvents are more preferred, and propylene glycol monomethyl ether acetate, cyclohexanone, and gamma-butyrolactone are even more preferred.

The radiation-sensitive resin composition may contain one or more of the above solvents.

(Other optional ingredients)
The radiation-sensitive resin composition may contain other optional components in addition to the above components. Examples of the other optional components include an acid diffusion controller, a crosslinking agent, a localization promoter, a surfactant, an alicyclic skeleton-containing compound, a sensitizer, etc. These other optional components may be used alone or in combination of two or more.

(Acid Diffusion Controller)
The radiation-sensitive resin composition may contain an acid diffusion controller as necessary. The acid diffusion controller controls the diffusion phenomenon in the resist film of the acid generated from the radiation-sensitive acid generator by exposure, and suppresses undesirable chemical reactions in the non-exposed region. In addition, the storage stability of the obtained radiation-sensitive resin composition is improved. Furthermore, the resolution of the resist pattern is further improved, and the change in line width of the resist pattern due to the fluctuation of the delay time from exposure to development can be suppressed, and a radiation-sensitive resin composition with excellent process stability can be obtained.

Examples of acid diffusion control agents include compounds represented by the following formula (7) (hereinafter also referred to as "nitrogen-containing compound (I)"), compounds having two nitrogen atoms in the same molecule (hereinafter also referred to as "nitrogen-containing compound (II)"), compounds having three nitrogen atoms (hereinafter also referred to as "nitrogen-containing compound (III)"), amide group-containing compounds, urea compounds, and nitrogen-containing heterocyclic compounds.

In the above formula (7), R ²² , R ²³ and R ²⁴ each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted aralkyl group.

Examples of the nitrogen-containing compound (I) include monoalkylamines such as n-hexylamine; dialkylamines such as di-n-butylamine; trialkylamines such as triethylamine; and aromatic amines such as aniline.

Examples of nitrogen-containing compounds (II) include ethylenediamine, N,N,N',N'-tetramethylethylenediamine, etc.

Examples of the nitrogen-containing compound (III) include polyamine compounds such as polyethyleneimine and polyallylamine; polymers such as dimethylaminoethylacrylamide; and the like.

Examples of amide group-containing compounds include formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, propionamide, benzamide, pyrrolidone, and N-methylpyrrolidone.

Examples of urea compounds include urea, methylurea, 1,1-dimethylurea, 1,3-dimethylurea, 1,1,3,3-tetramethylurea, 1,3-diphenylurea, tributylthiourea, etc.

Examples of nitrogen-containing heterocyclic compounds include pyridines such as pyridine and 2-methylpyridine; morpholines such as N-propylmorpholine and N-(undecylcarbonyloxyethyl)morpholine; pyrazine, pyrazole, etc.

In addition, a compound having an acid dissociable group can also be used as the nitrogen-containing organic compound. Examples of such nitrogen-containing organic compounds having an acid dissociable group include N-t-butoxycarbonylpiperidine, N-t-butoxycarbonylimidazole, N-t-butoxycarbonylbenzimidazole, N-t-butoxycarbonyl-2-phenylbenzimidazole, N-(t-butoxycarbonyl)di-n-octylamine, N-(t-butoxycarbonyl)diethanolamine, N-(t-butoxycarbonyl)dicyclohexylamine, N-(t-butoxycarbonyl)diphenylamine, N-t-butoxycarbonyl-4-hydroxypiperidine, and N-t-amyloxycarbonyl-4-hydroxypiperidine.

In addition, a radiation-sensitive weak acid generator that generates a weak acid upon exposure to light can also be suitably used as the acid diffusion control agent. The acid generated by the radiation-sensitive weak acid generator is an acid that does not induce dissociation of the acid-dissociable group in the resin when heated at 110°C for 60 seconds. In this specification, an acid that induces dissociation of an acid-dissociable group means that an acid dissociates an acid-dissociable group contained in the resin when heated at 110°C for 60 seconds.

Examples of radiation-sensitive weak acid generators include onium salt compounds that decompose upon exposure to light and lose their ability to control acid diffusion. Examples of onium salt compounds include sulfonium salt compounds represented by the following formula (8-1) and iodonium salt compounds represented by the following formula (8-2).

In the above formulas (8-1) and (8-2), J ⁺ is a sulfonium cation, and U ⁺ is an iodonium cation. Examples of the sulfonium cation represented by J ⁺ include sulfonium cations represented by the following formulas (1-1-a) and (1-1-b) as well as sulfonium cations represented by the following formula (X-1). Examples of the iodonium cation represented by U+ include iodonium cations represented by the above formula (1-1-c) as well as iodonium cations represented by the following formula (X-2). E- and Q- are each independently an anion represented by OH-, Rα-COO-, or Rα-SO3-. Rα is an alkyl group, an aryl group, or an aralkyl group. A hydrogen atom in the aromatic ring of the aryl group or aralkyl group represented by Rα may be substituted with a hydroxy group, a fluorine atom-substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms.

In the above formula (X-1), R ^c1 , R ^c2 and R ^c3 are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms.

In the above formula (X-2), R ^e1 and R ^e2 each independently represent a halogen atom, a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms. k8 and k9 each independently represent an integer of 0 to 4.

Examples of the substituents that may replace the hydrogen atoms of the above groups include halogen atoms such as fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms, hydroxyl groups, carboxyl groups, cyano groups, nitro groups, alkyl groups (when replacing hydrogen atoms of cycloalkyl groups or aromatic hydrocarbon groups), aryl groups (when replacing hydrogen atoms of alkyl groups), alkoxy groups, alkoxycarbonyl groups, alkoxycarbonyloxy groups, acyl groups, and acyloxy groups. Among these, hydroxyl groups, alkoxy groups, alkoxycarbonyl groups, alkoxycarbonyloxy groups, acyl groups, and acyloxy groups are preferred, and alkoxy groups and alkoxycarbonyl groups are more preferred.

Examples of the radiation-sensitive weak acid generator include compounds represented by the following formula. However, whether or not dissociation of an acid-dissociable group is induced is relatively determined by factors such as the structure of the acid-dissociable group whose dissociation is induced, and not all of the compounds listed below necessarily fall under the category of radiation-sensitive weak acid generators.

Of the above radiation-sensitive weak acid generators, sulfonium salts are preferred, triarylsulfonium salts are more preferred, and triphenylsulfonium salicylate and triphenylsulfonium 10-camphorsulfonate are even more preferred.

The lower limit of the content of the acid diffusion control agent is preferably 3 parts by mass, more preferably 4 parts by mass, and even more preferably 5 parts by mass, per 100 parts by mass of the total of the radiation-sensitive acid generators. The upper limit of the content is preferably 150 parts by mass, more preferably 120 parts by mass, and even more preferably 110 parts by mass.

By setting the content of the acid diffusion control agent within the above range, the lithography performance of the radiation-sensitive resin composition can be further improved. The radiation-sensitive resin composition may contain one or more types of acid diffusion control agents.

(Crosslinking Agent)
The crosslinking agent is a compound having two or more functional groups, which (1) induces a crosslinking reaction in the polymer component by an acid catalysis in the baking step after the floodwise exposure step, and (1) increases the molecular weight of the polymer component, thereby decreasing the solubility of the patternwise exposed area in a developer. Examples of the functional group include a (meth)acryloyl group, a hydroxymethyl group, an alkoxymethyl group, an epoxy group, and a vinyl ether group.

(Uneven distribution promoter)
The uneven distribution promoter has the effect of making the high fluorine content resin unevenly distributed on the resist film surface more efficiently. By incorporating this uneven distribution promoter into the radiation-sensitive resin composition, the amount of the high fluorine content resin added can be reduced compared to the conventional case. Therefore, while maintaining the lithography performance of the radiation-sensitive resin composition, it is possible to further suppress the elution of components from the resist film into the immersion medium, and perform immersion exposure at a higher speed by high-speed scanning, thereby improving the hydrophobicity of the resist film surface, which suppresses immersion-induced defects such as watermark defects. Examples of the uneven distribution promoter that can be used include low-molecular compounds having a relative dielectric constant of 30 to 200 and a boiling point of 100° C. or higher at 1 atmospheric pressure. Specific examples of such compounds include lactone compounds, carbonate compounds, nitrile compounds, polyhydric alcohols, and the like.

Examples of the lactone compounds include gamma-butyrolactone, valerolactone, mevalonic lactone, and norbornane lactone.

Examples of the above carbonate compounds include propylene carbonate, ethylene carbonate, butylene carbonate, vinylene carbonate, etc.

Examples of the above nitrile compounds include succinonitrile, etc.

Examples of polyhydric alcohols include glycerin.

The lower limit of the content of the uneven distribution promoter is preferably 10 parts by mass, more preferably 15 parts by mass, even more preferably 20 parts by mass, and even more preferably 25 parts by mass, relative to 100 parts by mass of the total amount of resin in the radiation-sensitive resin composition. The upper limit of the content is preferably 300 parts by mass, more preferably 200 parts by mass, even more preferably 100 parts by mass, and particularly preferably 80 parts by mass. The radiation-sensitive resin composition may contain one or more types of uneven distribution promoters.

(Surfactant)
The surfactant has the effect of improving the coating property, striation, developability, etc. Examples of the surfactant include nonionic surfactants such as polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene n-octylphenyl ether, polyoxyethylene n-nonylphenyl ether, polyethylene glycol dilaurate, and polyethylene glycol distearate; Examples of surfactants include EFTOP EF301, EF303, and EF352 (manufactured by Tochem Products), Megafac F171 and F173 (manufactured by DIC), Fluorad FC430 and FC431 (manufactured by Sumitomo 3M), Asahiguard AG710, Surflon S-382, SC-101, SC-102, SC-103, SC-104, SC-105, and SC-106 (manufactured by Asahi Glass Co., Ltd.). The content of the surfactant in the radiation-sensitive resin composition is usually 2 parts by mass or less based on 100 parts by mass of the resin.

(Alicyclic skeleton-containing compound)
The alicyclic skeleton-containing compound exhibits the effect of improving dry etching resistance, pattern shape, adhesion to a substrate, and the like.

Examples of the alicyclic skeleton-containing compound include
Adamantane derivatives such as 1-adamantanecarboxylic acid, 2-adamantanone, and t-butyl 1-adamantanecarboxylate;
Deoxycholic acid esters such as t-butyl deoxycholate, t-butoxycarbonylmethyl deoxycholate, and 2-ethoxyethyl deoxycholate;
Lithocholic acid esters such as t-butyl lithocholic acid, t-butoxycarbonylmethyl lithocholic acid, and 2-ethoxyethyl lithocholic acid;
Examples include 3-[2-hydroxy-2,2-bis(trifluoromethyl)ethyl]tetracyclo[4.4.0.1(2,5).1(7,10)]dodecane, 2-hydroxy-9-methoxycarbonyl-5-oxo-4-oxa-tricyclo[4.2.1.0(3,7)]nonane, etc. The content of the alicyclic skeleton-containing compound in the radiation-sensitive resin composition is usually 5 parts by mass or less based on 100 parts by mass of the resin.

(Sensitizer)
The sensitizer acts to increase the amount of acid generated from the radiation-sensitive acid generator or the like, and exerts the effect of improving the "apparent sensitivity" of the radiation-sensitive resin composition.

Examples of sensitizers include carbazoles, acetophenones, benzophenones, naphthalenes, phenols, biacetyl, eosin, rose bengal, pyrenes, anthracenes, and phenothiazines. These sensitizers may be used alone or in combination of two or more. The content of the sensitizer in the radiation-sensitive resin composition is usually 2 parts by mass or less per 100 parts by mass of the resin.

<Photoacid Generator>
The photoacid generator of the present invention contains the above-mentioned sulfonium salt compound.

Since the photoacid generator of the present invention is a sulfonium salt compound as described above, for example, when a radiation-sensitive resin composition containing this is used, it is possible to achieve excellent levels of sensitivity and LWR performance in the exposure process.

In addition, in the photoacid generator of the present invention, it is preferable that the above anion has a sulfonate anion moiety.

<Method for preparing radiation-sensitive resin composition>
The radiation-sensitive resin composition of the present invention can be prepared, for example, by mixing a resin, a radiation-sensitive acid generator, and if necessary, an acid diffusion controller, a high fluorine content resin, and a solvent in a predetermined ratio. After mixing, the radiation-sensitive resin composition is preferably filtered, for example, through a filter having a pore size of about 0.05 μm. The solid content concentration of the radiation-sensitive resin composition is usually 0.1% by mass to 50% by mass, preferably 0.5% by mass to 30% by mass, and more preferably 1% by mass to 20% by mass.

In addition, known methods can be used as appropriate to prepare the above-mentioned radiation-sensitive resin composition.

<Method of forming a resist pattern>
The method for forming a resist pattern according to the present invention comprises the steps of:
A step (1) of forming a resist film from the radiation-sensitive resin composition (hereinafter also referred to as a "resist film forming step");
The method includes a step (2) of exposing the resist film to light (hereinafter also referred to as an "exposure step"), and a step (3) of developing the exposed resist film (hereinafter also referred to as a "development step").

According to the above-mentioned resist pattern forming method, since the above-mentioned radiation-sensitive resin composition is used, it is possible to form a resist pattern that can exhibit excellent levels of sensitivity and LWR performance in the exposure process. Each step will be described below.

[Resist film forming process]
In this step (the above step (1)), a resist film is formed from the above radiation-sensitive resin composition. An example of the above step (1) is a step of directly or indirectly applying the above radiation-sensitive resin composition onto a substrate to form a resist film.

The substrate on which the resist film is formed may be, for example, a silicon wafer, silicon dioxide, or a wafer coated with aluminum. In addition, an organic or inorganic anti-reflective film disclosed in, for example, JP-B-6-12452 or JP-A-59-93448 may be formed on the substrate. Examples of the coating method include spin coating, casting coating, and roll coating. After coating, pre-baking (PB) may be performed as necessary to volatilize the solvent in the coating film. The PB temperature is usually 60°C to 140°C, and preferably 80°C to 120°C. The PB time is usually 5 seconds to 600 seconds, and preferably 10 seconds to 300 seconds. The thickness of the resist film formed is preferably 10 nm to 1,000 nm, and more preferably 10 nm to 500 nm.

When performing immersion exposure, regardless of the presence or absence of a water-repellent polymer additive such as the high fluorine content resin in the radiation-sensitive resin composition, a protective film for immersion that is insoluble in the immersion liquid may be provided on the resist film formed above in order to avoid direct contact between the immersion liquid and the resist film. As the protective film for immersion, either a solvent-peelable protective film that is peeled off with a solvent before the development step (see, for example, JP-A-2006-227632) or a developer-peelable protective film that is peeled off simultaneously with development in the development step (see, for example, WO2005-069076 and WO2006-035790) may be used. However, from the viewpoint of throughput, it is preferable to use a developer-peelable protective film for immersion.

In addition, when the next step, the exposure step, is carried out using radiation having a wavelength of 50 nm or less, it is preferable to use a resin having the above structural unit (a1) and structural unit (a2) as the base resin in the above composition.

[Exposure process]
In this step (step (2) above), the resist film formed in the resist film forming step (1) above is irradiated with radiation through a photomask (or, in some cases, through an immersion medium such as water) to expose the resist film. Examples of radiation used for exposure include electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, EUV (extreme ultraviolet light), X-rays, and gamma rays; charged particle beams such as electron beams and alpha rays, depending on the line width of the target pattern. Among these, far ultraviolet light, electron beams, and EUV are preferred, ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV are more preferred, and electron beams and EUV with a wavelength of 50 nm or less, which are positioned as next-generation exposure technologies, are even more preferred.

When the exposure is performed by immersion exposure, the immersion liquid used can be, for example, water, a fluorine-based inert liquid, etc. It is preferable that the immersion liquid is transparent to the exposure wavelength and has a temperature coefficient of refractive index as small as possible so as to minimize distortion of the optical image projected onto the film. However, especially when the exposure light source is an ArF excimer laser light (wavelength 193 nm), water is preferable from the viewpoints of ease of availability and ease of handling in addition to the above. When water is used, a small proportion of an additive that reduces the surface tension of water and increases the surfactant power may be added. It is preferable that this additive does not dissolve the resist film on the wafer and has a negligible effect on the optical coating on the lower surface of the lens. Distilled water is preferable as the water to be used.

After the above exposure, it is preferable to perform a post-exposure bake (PEB) to promote dissociation of acid-dissociable groups in the resin, etc., by the acid generated from the radiation-sensitive acid generator upon exposure in the exposed parts of the resist film. This PEB creates a difference in solubility in the developer between the exposed and unexposed parts. The PEB temperature is usually 50°C to 180°C, with 80°C to 130°C being preferred. The PEB time is usually 5 seconds to 600 seconds, with 10 seconds to 300 seconds being preferred.

[Development process]
In this step (step (3) above), the resist film exposed in the exposure step (2) above is developed. This allows a desired resist pattern to be formed. After development, the resist film is generally washed with a rinse liquid such as water or alcohol, and then dried.

In the case of alkaline development, examples of the developer used in the above development include an alkaline aqueous solution in which at least one of the following alkaline compounds is dissolved: sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, aqueous ammonia, ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, methyldiethylamine, ethyldimethylamine, triethanolamine, tetramethylammonium hydroxide (TMAH), pyrrole, piperidine, choline, 1,8-diazabicyclo-[5.4.0]-7-undecene, 1,5-diazabicyclo-[4.3.0]-5-nonene, etc. Among these, a TMAH aqueous solution is preferred, and a 2.38% by mass TMAH aqueous solution is more preferred.

In the case of organic solvent development, examples of the organic solvent include hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, and alcohol solvents, or solvents containing organic solvents. Examples of the organic solvent include one or more of the solvents listed as the solvents for the radiation-sensitive resin composition described above. Among these, ester solvents and ketone solvents are preferred. As the ester solvent, acetate ester solvents are preferred, and n-butyl acetate and amyl acetate are more preferred. As the ketone solvent, chain ketones are preferred, and 2-heptanone is more preferred. The content of the organic solvent in the developer is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 99% by mass or more. Examples of components other than the organic solvent in the developer include water and silicone oil.

Examples of development methods include the dip method, in which the substrate is immersed in a tank filled with developer for a certain period of time; the puddle method, in which developer is piled up on the substrate surface by surface tension and allowed to stand for a certain period of time to develop the substrate; the spray method, in which developer is sprayed onto the substrate surface; and the dynamic dispense method, in which developer is continuously dispensed by scanning a developer dispensing nozzle at a constant speed over a substrate rotating at a constant speed.

<Substrate processing method, metal film pattern manufacturing method>
The method for processing a substrate according to the present invention includes the steps of:
The method further includes a step (4-1) of forming a pattern on a substrate using the resist pattern formed by the above method as a mask.

Further, the method for producing a metal film pattern according to the present invention comprises the steps of:
Furthermore, the method includes a step (4-2) of forming a metal film using the resist pattern formed by the above method as a mask.

The above-mentioned substrate processing method and the above-mentioned metal film pattern manufacturing method use the above-mentioned radiation-sensitive resin composition, making it possible to process high-quality substrate patterns and metal film patterns, respectively.

The above step (4-1) is a step of forming a pattern on a substrate using the resist pattern formed by the above method as a mask. Examples of methods for forming a pattern on a substrate using a resist pattern as a mask include a method of forming a resist pattern on a substrate and then forming a pattern on the substrate by a method such as dry etching in the areas where there is no resist, and a method of forming a resist pattern and then depositing substrate components by CVD or the like in the areas where there is no resist, or depositing metal by a method such as electroless plating to form part or all of the substrate.

The above-mentioned step (4-2) is a step of forming a metal film using the resist pattern formed by the above-mentioned method as a mask. Examples of methods for forming a metal film using a resist pattern as a mask include a method of forming a metal film by depositing metal by a method such as electroless plating on the parts where there is no resist, and a method of forming a resist pattern on a metal film and removing the metal film from the parts where there is no resist by a method such as dry etching to form a metal film.

Next, the present invention will be specifically described with reference to examples, but the present invention is not limited to the following examples. The measurement methods for various physical properties are shown below.

[Measurement of weight average molecular weight (Mw), number average molecular weight (Mn) and dispersity (Mw/Mn)]
The Mw and Mn of the polymers used in the examples were measured by gel permeation chromatography (GPC) using Tosoh GPC columns (G2000HXL: 2 columns, G3000HXL: 1 column, and G4000HXL: 1 column) under the following analytical conditions: flow rate: 1.0 mL/min, elution solvent: tetrahydrofuran, sample concentration: 1.0 mass%, sample injection amount: 100 μL, column temperature: 40° C., detector: differential refractometer, with monodisperse polystyrene as the standard. The dispersity (Mw/Mn) was calculated from the measurement results of Mw and Mn.

<Synthesis of Acid Generator [Z]>
[Synthesis Example 1: Synthesis of Acid Generator (Z-1)]
According to the following reaction scheme, an acid generator (Z-1) was synthesized.

The salt represented by formula (Z-p) (12 mmol), 2-methylbenzo[b]thiophene (10 mmol), and copper(II) benzoate (1.0 mmol) were mixed in a reaction vessel and stirred at 135°C for 1 hour. After cooling to room temperature, methylene chloride and distilled water were added for extraction and the organic layer was separated. The resulting organic layer was dried over sodium sulfate, the solvent was removed, and the mixture was purified by column chromatography to obtain compound (Z-c1a). In formula (Z-p), Tf represents a trifluoromethanesulfonyl group.

Compound (Z-c1a) (5.0 mmol) was dissolved in methanol (20 mL) and passed through QAE Sephadex (R) A-25 chloride foam (1.0 g) washed with methanol to concentrate the resulting solution to obtain compound (Z-c1b). Next, methylene chloride (25 mL) and distilled water (25 mL) were added to compound (Z-c1b) and the salt represented by (Z-a1) (5.0 mmol). After stirring for 1 hour, the organic layer was separated and dried over sodium sulfate. The solvent was distilled off to obtain compound (Z-1).

[Synthesis Examples 2 to 8: Synthesis of Compounds (Z-2) to (Z-8)]
By appropriately selecting precursors and selecting the same formulation as in Example 1, acid generators [C] represented by the following formulae (Z-2) to (Z-8) were synthesized.

<[D] Synthesis of Acid Diffusion Controller>
[Synthesis Examples 9 to 14: Synthesis of Compounds (D-1) to (D-6)]
By appropriately selecting precursors and selecting the same formulation as in Example 1, acid diffusion controllers [D] represented by the following formulae (D-1) to (D-6) were synthesized.

<Synthesis of Polymer [A]>
The monomers used in the synthesis of each polymer in each of the Examples and Comparative Examples are shown below.

M-2 and M-3 were used as compounds having a protecting group, and M-1, M-4, M-5, M-6, and M-7 were used as compounds having a polar group. In the following synthesis examples, unless otherwise specified, parts by mass refer to a value when the total mass of the monomers used is taken as 100 parts by mass, and mol % refers to a value when the total number of moles of the monomers used is taken as 100 mol %.

[Synthesis Example 15: Synthesis of Polymer (A-1)]
The compound (M-1) and the compound (M-2) as monomers were dissolved in propylene glycol monomethyl ether (200 parts by mass) so that the molar ratio was 45/55. To this, 2,2'-azobis(methyl isobutyrate) (12 mol%) was added as an initiator to prepare a monomer solution. Meanwhile, propylene glycol monomethyl ether (100 parts by mass relative to the total monomer amount) was added to an empty reaction vessel and heated to 85°C while stirring. Next, the monomer solution prepared above was dropped over 3 hours, and then heated at 85°C for another 3 hours, and the polymerization reaction was carried out for a total of 6 hours. After the polymerization reaction was completed, the polymerization solution was cooled to room temperature. The polymerization solution was dropped into n-hexane (1,000 parts by mass) to coagulate and purify the polymer. Propylene glycol monomethyl ether (150 parts by mass) was added again to the above polymer. Further, methanol (150 parts by mass), triethylamine (1.5 molar equivalents relative to the amount of compound (M-1) used) and water (1.5 molar equivalents relative to the amount of compound (M-1) used) were added, and the hydrolysis reaction was carried out for 8 hours while refluxing at the boiling point. After completion of the reaction, the solvent and triethylamine were distilled off under reduced pressure, and the obtained polymer was dissolved in acetone (150 parts by mass). This was dropped into water (2,000 parts by mass) to coagulate, and the resulting white powder was separated by filtration. The mixture was dried at 50° C. for 17 hours to obtain a white powdery polymer (A-1) in good yield.

[Synthesis Examples 16 to 17: Synthesis of Polymer (A-2) and Polymer (A-3)]
Polymer (A-2) and polymer (A-3) were synthesized by carrying out the same operations as in Synthesis Example 15 using appropriately selected monomers.

[Synthesis Example 18: Synthesis of Polymer (A-4)]
The compounds (M-2), (M-5) and (M-6) as monomers were dissolved in 2-butanone (200 parts by mass) so that the molar ratio was 50/40/10. Azobisisobutyronitrile (5 mol%) was added as an initiator to prepare a monomer solution. Meanwhile, 2-butanone (100 parts by mass) was placed in an empty reaction vessel, and the mixture was purged with nitrogen for 30 minutes. The reaction vessel was heated to 80°C, and the monomer solution was dropped over 3 hours while stirring. The start of the dropwise addition was set as the start time of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After the polymerization reaction was completed, the polymerization solution was cooled with water to 30°C or less. The cooled polymerization solution was poured into methanol (2,000 parts by mass), and the precipitated white powder was filtered off. The white powder was washed twice with methanol, filtered off, and dried at 50°C for 17 hours to obtain a white powdery polymer (A-4) in good yield.

[Synthesis Example 19: Synthesis of Polymer (B-1)]
The compound (M-2) and the compound (M-7) as monomers were dissolved in 2-butanone (100 parts by mass) so that the molar ratio was 70/30. Azobisisobutyronitrile (5 mol%) was added as an initiator to prepare a monomer solution. Meanwhile, 2-butanone (50 parts by mass) was placed in an empty reaction vessel, and the mixture was purged with nitrogen for 30 minutes. The reaction vessel was heated to 80°C, and the monomer solution was added dropwise over 3 hours while stirring. The start of the dropwise addition was set as the start time of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After the polymerization reaction was completed, the polymerization solution was cooled with water to 30°C or less. The reaction solution was transferred to a separatory funnel, and then the reaction solution was uniformly diluted with hexane (150 parts by mass), and methanol (600 parts by mass) and water (30 parts by mass) were added and mixed. After standing for 30 minutes, the lower layer was recovered and the solvent was replaced with propylene glycol monomethyl ether acetate to obtain a propylene glycol monomethyl ether acetate solution containing polymer (B-1).

The amount of each structural unit used, as well as the Mw and Mw/Mn values of the resulting polymer are shown in Table 1. Note that in the table below, "-" indicates that the corresponding component was not used.

<Preparation of Radiation-Sensitive Resin Composition>
The other acid generators [CZ], other acid diffusion controllers [CD], and solvents [E] used in the preparation of the radiation-sensitive resin compositions of the following Examples and Comparative Examples are shown below.

[[CZ] Other Acid Generators]
[CZ] As other acid generators, the compounds represented by (CZ-1) and (CZ-2) were used.

[[CD] Other Acid Diffusion Control Agents]
[CD] As other acid diffusion controllers, the compounds represented by (CD-1) to (CD-3) were used.

[E] Solvent
E-1: Propylene glycol monomethyl ether acetate E-2: Propylene glycol monomethyl ether E-3: Cyclohexanone

Example 1
A radiation-sensitive resin composition (R-1) was prepared by blending 100 parts by mass of [A] polymer (A-1), 20 parts by mass of [Z] acid generator (Z-1), 50 mol% of [D] acid diffusion inhibitor (D-1) relative to (Z-1), and [E] organic solvents (E-1) and (E-2).

[Examples 2 to 15 and Comparative Examples 1 and 2]
Radiation-sensitive resin compositions (R-2) to (R-15) and (CR-1) to (CR-2) were prepared in the same manner as in Example 1, except that the types and amounts of each component shown in Table 2 below were used.

<Formation of Resist Pattern (1)> (EUV Exposure, Alkaline Development)
Each of the radiation-sensitive resin compositions prepared above was applied to the surface of a 12-inch silicon wafer on which a 20-nm-thick underlayer film (AL412 (Brewer Science)) was formed, using a spin coater (CLEAN TRACK ACT12, Tokyo Electron). After performing SB (soft bake) at 100°C for 60 seconds, the wafer was cooled at 23°C for 30 seconds to form a resist film with a thickness of 30 nm. Next, the resist film was irradiated with EUV light using an EUV exposure machine (model "NXE3300", ASML, NA = 0.33, illumination conditions: Conventional s = 0.89). The resist film was subjected to PEB (post exposure bake) at 100°C for 60 seconds. Then, the resist was developed using a 2.38 wt % aqueous solution of TMAH at 23° C. for 30 seconds to form a positive type 26 nm half pitch line and space pattern.

<Evaluation>
The resist patterns thus formed were measured according to the following methods to evaluate the LWR performance and process window of each radiation-sensitive resin composition. A scanning electron microscope (CG-5000, manufactured by Hitachi High-Technologies Corporation) was used to measure the length of the resist patterns. The evaluation results are shown in Table 3 below.

[sensitivity]
In forming the resist pattern, the exposure dose required to form a 26 nm half-pitch line and space pattern was determined as the optimum exposure dose, and this optimum exposure dose was determined as the sensitivity (mJ/ ^cm2 ). Sensitivity was determined as "good" when it was 60 mJ/cm2 or ^less , and "poor" when it exceeded 60 mJ/ ^cm2 .

[LWR performance]
The resist pattern was observed from above using the scanning electron microscope. The line width was measured at 50 arbitrary points, and the 3 sigma value was calculated from the distribution of the measured values, which was used as the LWR performance. The smaller the value, the better the LWR performance. The LWR performance was judged to be good when it was 4.0 nm or less, and poor when it was over 4.0 nm.

[Resolution]
At the above-mentioned optimum exposure dose, the dimension of the smallest resist pattern resolved when the size of the mask pattern forming the line and space (1L/1S) was changed was measured, and this measured value was taken as the resolution (nm). The smaller the value of the resolution, the better it is. The resolution can be evaluated as good when it is 20 nm or less, and as poor when it exceeds 20 nm.

As shown in Table 3, the radiation-sensitive resin compositions of the Examples all had better sensitivity, LWR performance, and resolution than the radiation-sensitive resin compositions of the Comparative Examples. As shown above, the radiation-sensitive resin compositions of the Examples of the present invention were found to have excellent sensitivity and LWR performance even in the case of EuV exposure.

[Examples 16 to 17 and Comparative Example 3]
Radiation-sensitive resin compositions (R-16) to (R-17) and (CR-3) were prepared in the same manner as in Example 1, except that the types and amounts of each component shown in Table 4 below were used.

<Formation of Resist Pattern (2)> (ArF Exposure, Alkaline Development)
A composition for forming a lower anti-reflective coating ("ARC66" manufactured by Brewer Science) was applied to the surface of a 12-inch silicon wafer using a spin coater ("CLEAN TRACK ACT12" manufactured by Tokyo Electron Co., Ltd.), and then heated at 205°C for 60 seconds to form a lower anti-reflective coating having an average thickness of 105 nm. Each of the radiation-sensitive resin compositions prepared above was applied onto this lower anti-reflective coating using the spin coater, and SB was performed at 90°C for 60 seconds. Thereafter, the coating was cooled at 23°C for 30 seconds to form a resist film having an average thickness of 90 nm. Next, this resist film was exposed through a 40 nm line and space (1L1S) mask pattern using an ArF excimer laser immersion exposure device ("NSR-S610C" manufactured by NIKON Corporation) under optical conditions of NA=1.3 and dipole (sigma 0.977/0.782). After the exposure, PEB was carried out for 60 seconds at 90° C. Thereafter, alkaline development was carried out using a 2.38 mass % TMAH aqueous solution as an alkaline developer, followed by washing with water and drying to form a positive resist pattern.

<Evaluation>
The LWR performance and resolution of each radiation-sensitive resin composition were evaluated by measuring each of the resist patterns formed as described above according to the following methods. Note that a scanning electron microscope ("CG-4100" manufactured by Hitachi High-Technologies Corporation) was used to measure the length of the resist patterns. The evaluation results are shown in Table 5 below.

[sensitivity]
In forming the resist pattern, the exposure dose required to form a 40 nm half-pitch line and space pattern was determined as the optimum exposure dose, and this optimum exposure dose was determined as the sensitivity (mJ/ ^cm2 ). Sensitivity was determined as "good" when it was 30 mJ/cm2 or ^less , and "poor" when it exceeded 30 mJ/ ^cm2 .

[LWR performance]
The resist pattern was observed from above using the scanning electron microscope. The line width was measured at 50 arbitrary points, and the 3 sigma value was calculated from the distribution of the measured values, which was used as the LWR performance. The smaller the value, the better the LWR performance. The LWR performance can be evaluated as good when it is 4.9 nm or less, and as poor when it exceeds 4.9 nm.

[Resolution]
At the above-mentioned optimum exposure dose, the dimension of the smallest resist pattern resolved when the size of the mask pattern forming the line and space (1L/1S) was changed was measured, and this measured value was taken as the resolution (nm). The smaller the value of the resolution, the better it is. The resolution can be evaluated as good when it is 36 nm or less, and as poor when it exceeds 36 nm.

As shown in Table 5, the radiation-sensitive resin compositions of the Examples all had better sensitivity, LWR performance, and resolution than the radiation-sensitive resin compositions of the Comparative Examples. Thus, it was found that the radiation-sensitive resin compositions of the Examples of the present invention had excellent sensitivity and LWR performance even in the case of ArF exposure.

As described above, the radiation-sensitive resin composition and resist pattern forming method of the present invention can achieve better performance than ever before in terms of sensitivity and LWR performance when radiation having a wavelength of 250 nm or less, such as EUV light, electron beam, ion beam, KrF excimer laser light, ArF excimer laser light, etc., is used as pattern exposure light. The radiation-sensitive resin composition and resist pattern forming method of the present invention can be suitably used in photoresist processes that will become even more fine in the future.

Claims (12)

A radiation-sensitive resin composition comprising a sulfonium salt compound represented by the following formula (1), a resin containing a structural unit having an acid-dissociable group, and a solvent:

(Wherein,
R ^f1 and R ^f2 each independently represent an alkyl group having 1 to 6 carbon atoms in which some or all of the hydrogen atoms have been substituted with halogen atoms, a halogen atom, an alkylsulfonyl group, a cyano group, or an arylsulfonyl group;
R ¹ is independently an organic group or a hydroxyl group;
^R2 is independently an alkyl group,
n is 0,
l1 is an integer of 0 to 5+2n, and when l1 is an integer of 2 to 5+2n, a plurality of R ^f1s are partly or entirely the same or different;
m1 is an integer of 0 to 6, and when m1 is an integer of 2 to 6, a plurality of R ^f2 are partly or entirely the same or different;
p1 is an integer of 0 to 5+2n, and when p1 is an integer of 2 to 5+2n, a plurality of R ^1's are partly or entirely the same or different;
q1 is an integer of 1 to 6, and when q1 is an integer of 2 to 6, some or all of the R ^2's are the same or different;
l1+p1 is 0 to 5+2n,
m1+q1 is 0 to 6,
At least one of l1 or m1 is an integer of 1 or more,
Z ₁ ^- is an anion.
However, this does not include the cases where the sulfonium salt compound is any of the following , and where the sulfonium salt compound is a salt represented by formula (I) .

[In formula (I),
R ¹ , R ² and R ³ each independently represent a halogen atom, a fluorinated alkyl group having 1 to 6 carbon atoms, or a hydrocarbon group having 1 to 18 carbon atoms, and --CH ₂ -- contained in the hydrocarbon group may be replaced by --O-- or --CO--.
m1 represents an integer of 0 to 4, and when m1 is 2 or more, the multiple R ^1s may be the same or different.
m2 represents an integer of 0 to 4, and when m2 is 2 or more, the multiple R ^2's may be the same or different.
m3 represents an integer of 0 to 2, and when m3 is 2, the two R ³ may be the same or different. The radiation-sensitive resin composition according to claim 1 , wherein the sulfonium salt compound is represented by the following general formula (2):

(Wherein,
R ^f3 and R ^f4 each independently represent an alkyl group having 1 to 6 carbon atoms in which some or all of the hydrogen atoms are substituted with halogen atoms, a halogen atom, an alkylsulfonyl group, a cyano group, or an arylsulfonyl group;
^R3 is independently an organic group or a hydroxyl group;
^R4 is independently an alkyl group,
l2 is an integer of 0 to 5, and when l2 is an integer of 2 to 5, a plurality of R ^f3 are partly or entirely the same or different;
m2 is an integer of 0 to 6, and when m2 is an integer of 2 to 6, a plurality of R ^f4s are partly or entirely the same or different;
p2 is an integer of 0 to 5, and when p2 is an integer of 2 to 5, some or all of the R ^3's are the same or different;
q2 is an integer of 1 to 6, and when q2 is an integer of 2 to 6, some or all of the R ^4s are the same or different;
l2+p2 is 0 to 5,
m2+q2 is 0 to 6,
At least one of l2 or m2 is an integer of 1 or more,
Z ₂ ^- is an anion. The radiation-sensitive resin composition according to claim 2 , wherein R ^f3 is located at a para position relative to the thienyl cation binding site. The radiation-sensitive resin composition according to any one of claims 1 to 3, wherein the halogen atom is a fluorine atom. The radiation-sensitive resin composition according to any one of claims 1 to 4, wherein the organic group includes an alkyl group, a hydroxyalkyl group, a cyano group, an ester group, an aldehyde group, a ketone group, an acetal group, a ketal group, an ether group, an amide group, a cycloalkyl group, or a phenyl group, which may be substituted. The radiation-sensitive resin composition according to any one of claims 1 to 5, wherein the anion has an acid anion moiety. The radiation-sensitive resin composition according to claim 6, wherein the acid anion moiety is a sulfonate anion moiety, a carboxylate anion moiety, or a chloride ion moiety. The radiation-sensitive resin composition according to any one of claims 1 to 7, wherein the content of the sulfonium salt compound is 0.5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the resin. A step (1) of forming a resist film from the radiation-sensitive resin composition according to any one of claims 1 to 9;
A method for forming a resist pattern comprising: a step (2) of exposing the resist film; and a step (3) of developing the exposed resist film. The method for forming a resist pattern according to claim 9, wherein the radiation used in the exposure step is ArF, extreme ultraviolet (EUV), X-rays, or electron beam (EB). A method for processing a substrate, comprising a step (4-1) of forming a pattern on a substrate using a resist pattern formed by the method according to claim 9 or 10 as a mask. A method for producing a metal film pattern, comprising the step (4-2) of forming a metal film using the resist pattern formed by the method according to claim 9 or 10 as a mask.