JPH0693122B2 - Highly sensitive radiation resist - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to an α-cyanoacrylic acid ester represented by the general formula (I) and a monomer of the general formula (II), which have excellent sensitivity characteristics and resolution to radiation. The purpose of the present invention is to provide a resist which can be applied to, for example, a large-scale integrated circuit of, for example, 16 megabit DRAM or later by using a resist containing as a main component.

<Prior art> For semiconductor integrated circuits, techniques such as electron beam direct writing and X-ray lithography have been developed as lithography techniques at the level of 0.5 μm or less, which is the limit of optical exposure. Development is also in an urgent stage.

In these resist materials, a negative resist that undergoes a cross-linking reaction upon irradiation with radiation to become insoluble in a developer, and the main agent polymer of the resist causes a main chain splitting reaction to reduce the molecular weight, and thus becomes easily soluble in a developer. There is a positive resist in which only the irradiation region is removed.

The characteristics of the negative resist are high sensitivity and excellent etching resistance, but low resolution.

On the other hand, the feature of the positive resist is that it has a high resolution but is inferior to the negative resist in sensitivity and etching resistance.

Recently, the speed of high integration of large-scale integrated circuits has been further accelerated, and the mainstream of radiation-sensitive resist is shifting to positive type resist.

However, although this positive resist is characterized by high resolution, it has major weaknesses in sensitivity and dry etching resistance, and this drawback has not yet been solved.

<Problems to be Solved by the Invention> Polymethylmethacrylate (PMMA) is a typical base polymer for positive resist, but its excellent resolution (0.3 to 0.5 μm) is extremely unbalanced and low sensitivity ( Because of 5 × 10 ⁵ C / cm ² ), as a practical resist, improvement efforts are concentrated on improving the sensitivity, and many proposals have been made.

In order to improve the sensitivity of the resist, the introduction of electron withdrawing groups such as Cl, Br, F, S, O and N can be considered. For example, polyhexafluorobutyl methacrylate, polytrichloroethyl methacrylate, polytrifluoroethyl α-chloroacrylate, polybutene-1 sulfone and the like have been proposed, but most of them are not only insufficient in sensitivity but also have poor adhesion. However, instability in process control such as dimensional stability and storage stability has not been resolved, and the reality is that it is far from a full-scale resist.

Therefore, an object of the present invention is to provide a radiation-sensitive resist having a higher resolution and a higher sensitivity for a large-scale integrated circuit of 16 megabit DRAM or later, which has high resolution and high sensitivity.

<Means for Solving the Problems> The invention according to claim 1 is made to achieve the above object. (In the formula, R is an alkyl group excluding C _{1 to} C ₅ , a cycloalkyl group, and a halogenated alkyl group), a homopolymer of α-cyanoacrylic acid ester, or a copolymer of two or more kinds of this monomer group. A polymer, or this group of monomers, (However, X in the formula is CH ₃ , Cl, F, Br, I, COOR, N
O ₂ and Y are H and COOR, and R is a high-sensitivity radiation-sensitive resist whose main component is a copolymer consisting of one or more kinds of monomers represented by alkyl groups and halogenated alkyl groups). .

<Operation> According to the present invention, R constituting the ester group represented by the general formula (I) is an alkyl group excluding C _{1 to} C ₅ , a cycloalkyl group,
Conventionally, a resist formed by forming a polymer or copolymer containing α-cyanoacrylic acid ester as a halogenated alkyl group as a basic constitutional unit, or a copolymer with a monomer represented by the general formula (II) has been conventionally used. It has high resolution and high sensitivity as compared with the above resist.

<Examples> Hereinafter, the present invention will be described in detail based on Examples.

In the present invention, in addition to the electron withdrawing group CN, Cl, F, Br
A general formula (I) having (In the formula, R is an alkyl group excluding C _{1 to} C ₅ , a cycloalkyl group, and a halogenated alkyl group), a homopolymer of α-cyanoacrylic acid ester, or a copolymer of two or more kinds of this monomer group. A polymer, or a group of these monomers, and the general formula (II); (However, X in the formula is CH ₃ , Cl, F, Br, I, COOR, N
O ₂ and Y are H and COOR, and R is an alkyl group and a halogenated alkyl group). Has a high sensitivity characteristic, that is, the electron beam sensitivity is 5 × 10
^{Since it is 7} C / cm ² or more, and the radiation dose of about 1/100 is sufficient compared to the PMMA sensitivity of 5 × 10 ⁵ C / cm ² , the productivity is about 100 times and the line width is further increased. Since it has a practical resolution of 0.5 μm or less, it is suitable as a resist for large-scale integrated circuits after 16 megabit DRAM.

In the above α-cyanoacrylic acid ester of the general formula (I), R in the formula is an alkyl group excluding C _{1 to} C ₅ , a cycloalkyl group or a halogenated alkyl group, and specifically α-
Cyanoacrylate n-hexyl, α-cyanoacrylate cyclohexyl, α-cyanoacrylate cycloheptyl, α-cyanoacrylate n-octyl, α-cyanoacrylate 2-ethylhexyl, α-cyanoacrylate trifluoroethyl, α -Hexafluorobutyl cyanoacrylate and the like.

On the other hand, the monomer group represented by the general formula (II) is specifically nitroethylene, diethyl methylenemalonate, trifluoroethyl methacrylate, hexafluorobutyl methacrylate, α-chloroacrylic acid trifluoroethyl or the like.

These monomers may be those obtained by a usual synthesis method, and the anion synthesis inhibitor may remain mixed. The homopolymer consisting of the above, and the molecular weight of the copolymer are both usually 20000 to 2000000, preferably 20000 to 100000.
0 is used.

Further, specific examples of the present invention will be described. The invention is not limited to these examples.

And the Example 1 anionic polymerization inhibitor (SO ₂ 50ppm) α- cyanoacrylic acid cyclohexyl 0.5 mol / 800 ml acetone solution containing introduced into the flask. While sufficiently stirring the inside of the system, 5 × 10 ⁴ of the anionic polymerization initiator (aniline) was added at room temperature.
While maintaining the temperature in the system at room temperature, a mol / 100 ml acetone solution was gradually added and reacted.

The obtained polymer was taken out of the system, purified by reprecipitation method, and then its molecular weight was measured by gel permeation chromatography (GPC) -light scattering method. 476000, the polymerization rate is 96.4%
Met.

A 5% by weight solution of this polymer in cyclohexanone was prepared and coated on a silicon oxide layer having a thickness of 0.5 μm by a spin coating method to obtain a polymer (resist) film having a thickness of 0.54 μm. This was heat-treated (pre-baked) at 140 ° C. for 30 minutes, and then the polymer (resist) film surface was irradiated with an electron beam having an accelerating voltage of 10 KV 5 × 10 ⁷ C / cm ² according to a predetermined pattern. Subsequently, this was taken out into the air, developed by immersing it in a 1: 2 developer of cyclohexanone and methyl isobutyl ketone at 25 ° C. for 3 minutes, rinsed with isopropyl alcohol and dried. Then, heat treatment (post-baking) was performed at 140 ° C. for 30 minutes.

When the polymer (resist) film treated as described above was observed by a scanning electron microscope (SEM), the polymer (resist) film in the electron beam irradiation region was completely removed, and the silicon oxide layer It was confirmed that the adhesion between the polymer and the polymer (resist) film was also good.

When this was etched with a reactive ion etching device (RIE), a linear sharp pattern of 0.3 μm was confirmed by SEM.

On the other hand, the electron beam sensitivity of the PMMA resist used for comparison was 5 × 10 ⁵ C / cm ^2, which was 1/100 of that of Example 1, and the resolution was the same as that of Example 1 (accelerating voltage 10 KV). , 0.5μ
m and the resolution of Example 1 were not reached.

Example 2 A 0.3 mol / 400 ml acetone solution of trifluoroethyl α-cyanoacrylate containing 50 ppm of an anionic polymerization inhibitor (SO ₂ ) and 0.2% of n-heptyl α-cyanoacrylate.
Mol / 400 ml acetone solution was introduced into the flask.

While sufficiently stirring the inside of the system, a 5 × 10 ⁴ mol / 100 ml acetone solution of an anionic polymerization initiator (diethylamine) was gradually added and allowed to react while keeping the temperature in the system at room temperature. The obtained copolymer was taken out of the system and purified by the reprecipitation method. The molecular weight of this was measured by gel permeation chromatography (GPC) -light scattering method. As a result, the molecular weight was 535,000 and the polymerization rate was 96.7%.

A 5 wt% cyclohexanone solution of this copolymer was prepared,
It was applied on a 0.5 μm thick thermally oxidized silicon layer by a spin coating method to obtain a copolymer (resist) film having a thickness of 0.53 μm. As in Example 1, this was prebaked and then the acceleration voltage was applied.
Electron beam of 10KV 4 × 10 ⁷ C / cm ² according to the predetermined pattern,
The surface of the copolymer (resist) film was irradiated. Subsequently, this was taken out into the atmosphere and subjected to development, rinsing and post-baking as in Example 1, and then the copolymer (resist) film was observed by SEM. It was confirmed that the copolymer (resist) film in the electron beam irradiation region was completely removed, and the adhesion between the silicon oxide layer and the copolymer (resist) film was good.

As a result of etching by RIE, a linear sharp pattern of 0.4 μm was confirmed by SEM.

Example 3 A copolymer of hexafluorobutyl α-cyanoacrylate and cyclohexyl α-cyanoacrylate in a molar ratio of 6: 4 was obtained by an anionic polymerization method in the same manner as in Example 2. This is gel permeation chromatography (GPC)
-Measurement of its molecular weight by the light scattering method showed that it had a molecular weight of 648,000 and a polymerization rate of 96.3%.

A 5 wt% cyclohexanone solution of this copolymer was prepared,
It was applied on a thermally oxidized silicon layer having a thickness of 0.5 μm by a spin coating method to obtain a copolymer (resist) film having a thickness of 0.61 μm. After pre-baking, electron beam irradiation, development, rinsing and post-baking in the same manner as in Example 2, the copolymer (resist) film was observed by SEM. It was confirmed that the copolymer (resist) film in the electron beam irradiation region was completely removed, and the adhesion between the silicon oxide layer and the copolymer (resist) film was good.

As a result of etching by RIE, a linear sharp pattern of 0.4 μm was confirmed by SEM.

Example 4 10 parts of trifluoroethyl α-cyanoacrylate, 5 parts of trifluoroethyl methacrylate, 3 parts of acetic acid and 0.1 part of azobisisobutyronitrile were subjected to sealed tube polymerization in nitrogen. The obtained copolymer was purified by the reprecipitation method. The molecular weight of this was measured by gel permeation chromatography (GPC) -light scattering method.
At 00, the polymerization rate was 95.1%.

A 5 wt% cyclohexanone solution of this copolymer was prepared,
By a spin coating method, a thermal oxidation silicon layer having a thickness of 0.5 μm was coated to obtain a copolymer (resist) film having a thickness of 0.47 μm. This was heat-treated (prebaked) at 130 ° C. for 30 minutes, and then the copolymer (resist) film surface was irradiated with an electron beam having an accelerating voltage of 10 KV 4 × 10 ⁷ C / cm ² according to a predetermined pattern.
Then, after developing, rinsing, and post-baking the same as in Example 2, the copolymer (resist) film was observed by SEM. The copolymer (resist) film in the electron beam irradiation region was completely removed. A clear positive image was confirmed.

As a result of etching by RIE, a linear and sharp pattern of 0.5 μm was confirmed by SEM.

Example 5 Anionic polymerization initiator (diethylamine 5 × 10 ⁴ mol)
Acetone / toluene mixed solution 700 ml containing is introduced into the flask, and while thoroughly stirring the system, diethyl methylene malonate (0.3 mol) containing 50 ppm each of the polymerization inhibitor (SO ₂ ) and cyclohexyl α-cyanoacrylate.
200 ml of an acetone / toluene mixed solution containing 0.2 mol was gradually added to the temperature of the system at room temperature for reaction.
The obtained copolymer was purified by the reprecipitation method. The molecular weight of this was measured by gel permeation chromatography (GPC) -light scattering method.
At 601000, the degree of polymerization was 96.7%.

A 5 wt% cyclohexanone solution of this copolymer was prepared,
It was applied onto a 0.5 μm thick thermally oxidized silicon layer by a spin coating method to obtain a copolymer (resist) film with a thickness of 0.59 μm. Pre-baking, electron beam irradiation, development, rinsing, and post-baking were performed in the same manner as in Example 1, and as a result of etching by RIE, a linear sharp pattern of 0.5 μm was confirmed by SEM.

Example 6 Obtained by sealing tube polymerization of 10 parts of 2-ethylhexyl α-cyanoacrylate, 5 parts of trifluoroethyl α-chloroacrylate, 3 parts of acetic acid, and 0.1 parts of azobisisobutyronitrile in a sealed tube in nitrogen. The copolymer was purified by the reprecipitation method. This is gel permeation chromatography (GPC)-
When the molecular weight was measured by a light scattering method, the molecular weight was 352000 and the polymerization rate was 94.6%.

A 5 wt% cyclohexanone solution of this copolymer was prepared,
It was applied on a thermally oxidized silicon layer having a thickness of 0.5 μm by a spin coating method to obtain a copolymer (resist) film having a thickness of 0.61 μm. Pre-baking, electron beam irradiation, development, rinsing, and post-baking were performed in the same manner as in Example 1, and as a result of etching by RIE, a linear sharp pattern of 0.4 μm was confirmed by SEM.

Example 7 0.4 mol of α-cyanoacrylate n-heptyl and nitroethylene each containing 50 ppm of an anionic polymerization inhibitor (SO ₂ ).
Mix 0.1 mol into 800 ml of acetone, and mix well with 5 × anionic polymerization initiator (thiourea) at room temperature.
A 10 ⁴ mol / 100 ml acetone solution was kept at room temperature at room temperature and gradually added to react.

The obtained copolymer was taken out of the system and purified by the reprecipitation method. Then, its molecular weight was measured by gel permeation chromatography (GPC) -light scattering method. Is 491000 and its polymerization rate is 97.1.
%Met.

A 5 wt% cyclohexanone solution of this copolymer was prepared,
It was applied on a silicon oxide layer having a thickness of 0.5 μm by a spin coating method to obtain a copolymer (resist) film having a thickness of 0.53 μm. Pre-baking, electron beam irradiation, development, rinsing, and post-baking were performed in the same manner as in Example 1, and as a result of etching by RIE, a linear sharp pattern of 0.4 μm was confirmed by SEM.

<Effect> According to the present invention, it is about 1/100 of that of the conventional PMMA resist.
It is a highly sensitive resist that requires only a small amount of radiation dose, and can maintain a high resolution of a line width of 0.5 μm or less. For example, it is effective for X-ray lithography when manufacturing large-scale integrated circuits of semiconductors after 16 megabit DRAM. The excellent image characteristics not only make it possible to greatly improve the processing accuracy and design a circuit with a wide latitude, but also the excellent sensitivity characteristics have a great effect on high productivity and cost reduction.

Claims (1)

[Claims] 1. (In the formula, R is an alkyl group excluding C _{1 to} C ₅ , a cycloalkyl group, and a halogenated alkyl group), a homopolymer of α-cyanoacrylic acid ester, or a copolymer of two or more kinds of this monomer group. A polymer, or this group of monomers, (However, X in the formula is CH ₃ , Cl, F, Br, I, COOR, N
O ₂ and Y are H and COOR, and R is an alkyl group and a halogenated alkyl group), which is a high-sensitivity radiation-sensitive resist containing as a main component a copolymer composed of one or more kinds of monomers.