JP3453365B2 - Pattern formation method by photoengraving - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern forming method by photolithography, and more particularly to a pattern forming method for accurately transferring a pattern to a chemically amplified resist.

[0002]

2. Description of the Related Art FIG. 2 is a diagram for explaining the flow of a conventional pattern forming method by photolithography. In the conventional pattern forming method, as shown in FIG. 2A, the resist 12 is first applied onto the substrate 10. Next, FIG.
As shown in (B), the resist 12 is formed using the mask 14.
Is exposed. After that, a developing process is performed to form a desired pattern on the resist 12 as shown in FIG.

In recent years, in order to form a fine pattern with high precision, in the exposure process shown in FIG.
A halftone mask is used. FIG. 3 is a diagram for explaining the structure of the halftone mask 16. More specifically, FIG. 3A shows the halftone mask 16
3B is a plan view of FIG. 3B, and FIG. 3B is a cross-sectional view obtained by cutting the halftone mask 16 along the line AA shown in FIG.

The halftone mask 16 has a light-shielding portion 18 shielded by a chrome film, a light-transmitting portion 20 for passing exposure light, and a shifter 22 formed at the boundary between the light-transmitting portion 20 and the light-shielding portion 18. Is equipped with. The light shielding portion 18 is a portion where transmission of exposure light is completely blocked.
The light-transmitting portion 20 corresponds to a transfer pattern formed on the halftone mask 16 and is a portion that transmits exposure light with a transmittance of 100%. The shifter 22 is a portion that transmits the exposure light with a predetermined transmittance (usually 4 to 6%).

If a shifter having the above characteristics is formed around the transparent portion 20, the intensity of the light in the area corresponding to the transfer pattern can be increased by the light interference effect. Therefore, the halftone mask is effective in accurately transferring the pattern when the transfer pattern is fine and sufficient light intensity cannot be obtained only by the light transmitting portion 20.

[0006]

The effect of increasing the light intensity at the portion corresponding to the transfer pattern by utilizing the interference of light, that is, the halftone effect is improved by increasing the transmittance of the exposure light in the shifter 22. Can be made.
However, when the transmittance of the shifter 22 is increased, the light intensity of the portion corresponding to the transfer pattern is increased and the resist 1
The intensity of the light reaching the portion of 2 covered with the shifter 22 also increases.

For this reason, if the transmittance of the shifter is increased,
The resist 12 may be exposed to light in a region directly below the shifter 22 that should not be exposed to light, and dimples may appear on the surface of the resist 12 after the development process. As described above, the conventional pattern forming method has a problem that the halftone effect cannot be enhanced without generating dimples in the resist 12.

The present invention has been made to solve the above problems, and an object thereof is to provide a pattern forming method for ensuring a high halftone effect without causing dimples in a resist. To do.

[0009]

The invention according to claim 1 is
A pattern forming method by photoengraving, which includes a coating step of coating a chemically amplified resist on a substrate and a shifter area.
An exposure step of exposing the resist using a halftone mask having a transmittance of more than 6% and not more than 20% in a region, a developing step of developing the resist, and coating on the substrate before the developing step. And a neutralizing step of exposing the resist to an atmosphere controlled to have a basic ion concentration of 1 ppb or more and 10 ppb or less .

The invention according to claim 2 is the pattern forming method according to claim 1, wherein in the neutralizing step, the basic ion concentration of the substrate coated with the resist is controlled within a predetermined range. It is done by going through the booth.

The invention according to claim 3 is the pattern forming method according to claim 2, wherein the basic ions are supplied into the booth so that the basic ion concentration in the booth is within a predetermined range. It is characterized by including a management process.

A fourth aspect of the present invention is the pattern forming method according to the third aspect, characterized by including a depressurizing step of setting the booth in a depressurized atmosphere.

A fifth aspect of the present invention is the pattern forming method according to any one of the first to fourth aspects, wherein the neutralizing step exposes the resist to the atmosphere before the exposing step. It is characterized by including one neutralization step.

The invention according to claim 6 is the pattern forming method according to any one of claims 1 to 5, wherein in the neutralizing step, the resist is exposed to the atmosphere after the exposing step. It is characterized by including a neutralization step.

[0015]

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. It should be noted that elements common to each drawing are denoted by the same reference numerals, and redundant description will be omitted.

Embodiment 1. FIG. 1 is a diagram for explaining the flow of the pattern forming method according to the first embodiment of the present invention. In the pattern forming method of this embodiment, first, as shown in FIG.
As shown in (A), a chemically amplified resist 12 is applied onto the substrate 10.

Next, the substrate 10 is the first substrate shown in FIG.
It is carried into the booth 30. To the first booth 30, a basic substance supply mechanism and a depressurization mechanism (not shown) are connected. In the atmosphere in the first booth 30, basic substances such as ammonia are appropriately supplied by the basic substance supply mechanism so that the basic ion concentration (ammonia concentration and other basic ion concentration) becomes a predetermined concentration. Specifically, the concentration is controlled so as to fall within the range of 1 to 10 ppb, more preferably within the range of 1 to 5 ppb.

Further, the inside of the first booth 30 is kept at a reduced pressure atmosphere lower than the atmospheric pressure by the pressure reducing mechanism. When the inside of the first booth 30 is under the reduced pressure atmosphere in this way, ammonia and other basic ions in the first booth 30 do not leak out of the first booth 30, and they adversely affect other processes. It can be surely prevented.

After passing through the first booth 30, the substrate 10 is subjected to an exposure process as shown in FIG. In the exposure process, the resist 1 is formed using the halftone mask 32.
2 is irradiated with exposure light. The halftone mask 32 used in this embodiment has substantially the same structure as the conventional halftone mask 16 shown in FIG. However, the halftone mask 32 in the present embodiment is formed so that the region of the shifter 22 exhibits a larger transmittance than that of the conventional halftone mask 16. In particular,
In the conventional halftone mask 16, the transmittance of the shifter 22 is normally set to 4 to 6%, whereas in the present embodiment, a desired range is 4 to 20% for the region of the shifter 22. The transmittance is given.

After the exposure process is completed, the substrate 10 is formed as shown in FIG.
It is carried into the second booth 34 shown in (D). Similar to the case of the first booth 30, the second booth 34 is connected with a basic substance supply mechanism and a decompression mechanism (not shown). Then, the atmosphere in the second booth 34 has a basic ion concentration (ammonia concentration and other basic ion concentrations) of a predetermined concentration by the basic substance supply mechanism appropriately supplying a basic substance such as ammonia. Specifically, the concentration is controlled to be within the range of 1 to 10 ppb, and more preferably within the range of 1 to 5 ppb.

Further, the inside of the second booth 34 has a reduced pressure atmosphere lower than the atmospheric pressure by the pressure reducing mechanism. When the inside of the second booth 34 is under a reduced pressure atmosphere in this way, ammonia and other basic ions in the second booth 34 do not leak out of the second booth 34, and they adversely affect other processes. It can be surely prevented.

After passing through the second booth 34, the substrate 10 is subjected to a developing process as shown in FIG. The resist 12 is patterned in a predetermined pattern by being processed in this developing process.

As described above, in this embodiment, the halftone mask 32 is used in the exposure process. Further, the halftone mask 32 is formed so that the shifter (corresponding to a portion indicated by reference numeral 22 in FIG. 3) transmits the exposure light with a relatively large transmittance (4 to 20%). . Therefore, according to the pattern forming method of the present embodiment, even if the transfer pattern is fine, the portion corresponding to the transfer pattern on the resist 12 (hereinafter, referred to as “pattern corresponding portion”) is exposed with sufficient intensity. It can be irradiated with light.

However, when the halftone mask 32 in which the shifter has a large transmittance is used, a portion of the resist 12 that should not be exposed to light, more specifically, a portion located immediately below the shifter (hereinafter, referred to as " The exposure light affects the shifter-corresponding portion ”to some extent. Therefore, the halftone mask 32 has a problem that dimples are easily generated in the shifter corresponding portion of the resist 12.

By the way, the chemically amplified resist 12 used in the present embodiment is activated by generating an acid when irradiated with light. Then, when the developing process is performed, the activated portion is removed, so that the resist 1
2 is patterned.

As described above, in this embodiment, the substrate 10 coated with the resist 12 is exposed to the atmosphere having a predetermined basic ion concentration prior to the developing process. More specifically, the substrate 10 is exposed to the atmosphere in which the basic ion concentration is controlled to a predetermined value inside the first booth 30 before the exposure step, and immediately after the exposure step, the second Inside the booth 34, the atmosphere in which the basic ion concentration is controlled to a predetermined value is exposed.

According to the above process using the first booth 30, basic ions such as ammonia can be attached or mixed in the vicinity of the surface of the resist 12 before the exposure step. These basic ions can neutralize the acid generated in the shifter-corresponding portion of the resist 12 during the exposure step and suppress the activation of that portion.

Further, according to the above processing using the second booth 34, basic ions such as ammonia can be attached or mixed in the vicinity of the surface of the resist 12 immediately after the exposure step. These basic ions neutralize the acid generated in the shifter corresponding portion of the resist 12 during the exposure step and activate the resist 12 in that portion.
Can be deactivated.

As described above, according to the pattern forming method of this embodiment, even though the shifter of the halftone mask 32 shows a large transmittance, the development is performed in a state where the shifter corresponding portion of the resist 12 is sufficiently deactivated. The process can start. Therefore, according to the pattern forming method of the present embodiment, it is possible to effectively solve the problem that dimples are generated in the shifter-corresponding portion after the developing step.

The above process using the first booth 30 or the above process using the second booth 34 is performed by the resist 12
Basic ions are also attached or mixed in the vicinity of the surface of the portion corresponding to the pattern. Therefore, on the surface of the pattern-corresponding portion of the resist 12, a hardly soluble layer which is difficult to be removed by the developing process is formed.

However, in this embodiment, the basic ion concentrations in the first booth 30 and the second booth 34 are controlled within the range of 1 ppb to 10 ppb, and more preferably within the range of 1 ppb to 5 ppb, as described above. . With such a basic ion concentration, it is possible to sufficiently deactivate the resist 12 in the shifter-corresponding portion and to sufficiently suppress the generation of the hardly soluble layer in the pattern-corresponding portion. Therefore, according to the pattern forming method of the present embodiment, a fine transfer pattern can be accurately patterned on the resist 12.

By the way, in the above-described embodiment, the basic ion is attached or mixed in the vicinity of the surface of the resist 12 by passing the substrate 10 through the first booth 30 and the second booth 32. The invention is not limited to this. For example, basic ions may be attached or mixed in the vicinity of the surface of the resist 12 by spraying a predetermined concentration of ammonia gas or the like on the surface of the resist 12.

Further, in the above-described embodiment, the step of supplying the basic ions to the surface of the resist 12 is performed twice before and after the exposure step, but it is not always necessary to use these in combination. . That is, the step of supplying the basic ions to the surface of the resist 12 may be performed once before the exposure step or only once after the exposure step.

Further, in the above-described embodiment, the first booth 30 and the second booth 34 are kept in a reduced pressure atmosphere, but the present invention is not limited to this. That is, the first booth 30 and the second booth 34
May be kept in a normal pressure atmosphere or may be kept in a pressurized atmosphere.

Further, in the above-described embodiment, the basic ion concentration in the first booth 30 and the second booth 34 are increased.
However, the present invention is not limited to this, and these concentrations may be different from each other as necessary.

[0037]

As described above, according to the present invention, the shifter-corresponding portion on the resist which is activated by using the halftone mask can be deactivated prior to the developing step. Therefore, according to the present invention, a fine transfer pattern can be accurately patterned on the resist while preventing the occurrence of dimples in the shifter corresponding portion.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a flow of a pattern forming method according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining the flow of a conventional pattern forming method.

3A and 3B are a plan view and a cross-sectional view for explaining the structure of a halftone mask.

[Explanation of symbols]

10 substrates 12 Resist 16; 32 Halftone mask 18 shaded area 20 Translucent part 22 shifters 30 First booth 34 Second booth

Continuation of front page (51) Int.Cl. ⁷ identification code FI H01L 21/027 H01L 21/30 568 (56) Reference JP-A-9-274313 (JP, A) JP-A-6-83073 (JP, A ) JP-A-4-14058 (JP, A) JP-A-6-273944 (JP, A) JP-A-10-198048 (JP, A) JP-A-11-231553 (JP, A) JP-A-9- 292719 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03F ^7/ 00-7/42

Claims (6)

(57) [Claims] 1. A pattern forming method by photoengraving, which comprises a step of applying a chemically amplified resist on a substrate and a transmittance of 6% to 20% in a shifter region.
An exposing step of exposing the resist using a halftone mask having, a developing step of developing the resist, and a resist having a basic ion concentration of 1 ppb or more before the developing step. A neutralization step of exposing to a controlled atmosphere of 10 ppb or less , and a pattern forming method comprising: 2. The neutralization step is carried out by passing the substrate coated with the resist through a booth in which the basic ion concentration is controlled within a predetermined range. Pattern formation method. 3. The pattern forming method according to claim 2, further comprising a management step of supplying basic ions into the booth so that the basic ion concentration in the booth is within a predetermined range. 4. The pattern forming method according to claim 3, further comprising a depressurizing step of making the booth a depressurized atmosphere. 5. The pattern formation according to claim 1, wherein the neutralization step includes a first neutralization step of exposing the resist to the atmosphere before the exposure step. Method. 6. The pattern forming method according to claim 1, wherein the neutralizing step includes a second neutralizing step of exposing the resist to the atmosphere after the exposing step. .