JPH06348036A - Method for forming resist pattern - Google Patents

Abstract

(57) [Summary] [Structure] In contrast-enhanced photolithography, a contrast-enhancement film is formed by using an aryl nitrone compound represented by the following formula (1), and exposure is performed by reduction projection with a coherent factor δ of 0.65 to 0.85. It is performed by an exposure machine. [Chemical 1] (In the formula, R ¹ , R ² and R ³ are the same or different alkyl groups, aryl groups or hydrogen atoms, and R ^{4 to} R ⁸ are the same or different alkyl groups, hydrogen atoms or —COO.
R (R is a hydrogen atom or an alkyl group), but at least one of R ^{4 to} R ⁸ is —COOR. X is R ⁹ O-
Is an alkoxy group represented by, R ¹⁰ R ¹¹ is a dialkylamino group represented by N— or a hydrogen atom, R ⁹ is an alkyl group, and R ¹⁰ and R ¹¹ are the same or different alkyl groups. n has a value of 0, 1 or 2. According to the method for forming a resist pattern of the present invention, a resist profile can be formed with good rectangularity and a resist pattern with an excellent focus margin can be formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to contrast enhanced photolithography (CEL: Contrast Enh).
The present invention relates to a method of forming a resist pattern on a substrate such as a silicon wafer by an enhancement lithography process.

[0002]

2. Description of the Related Art The use of lithographic techniques in the manufacture of semiconductor integrated circuits is well known. In such a lithographic process, a photoresist film is provided on a silicon wafer substrate to be etched, and the photoresist on the substrate is exposed to light having a constant wavelength through a mask on which a processing pattern is drawn. In a positive type resist in which a resist pattern is formed in a portion irradiated with light, the photoresist that undergoes a photochemical reaction due to the light transmitted through the mask is converted into a compound containing a carboxyl group that is soluble in an alkaline developer,
Next, the photoresist compound is dissolved by developing with contact with an alkaline aqueous solution, whereby a resist pattern to which the mask pattern is transferred can be formed. Then, etching is performed along the resist pattern to process the substrate.

More specifically, in the photolithography process using such a photoresist, a photoresist is spin-coated on a silicon wafer treated with hexamethyldisilazane (HMDS) or the like to form a uniform film having a predetermined thickness. After formation, the silicon wafer is heated (prebaked). After that, after patterning exposure through a photomask, post exposure bake (P
A patterning profile is formed by steps such as EB), development with a developing solution, and rinsing with pure water.

However, in recent years, miniaturization of integrated circuits
As the degree of integration increases, a lithography technique for transferring a very fine pattern to a resist is required. Therefore, a technique for transferring a fine pattern to a resist with good rectangularity and an accurate size is desired. In addition, as the number of layers of integrated circuits has increased, a focus margin that allows accurate patterning even in large steps has been required.
Further, when manufacturing 64 MDRAM (64 megabit dynamic random access memory), it is necessary to pattern a minimum line width of 0.35 μm with a focus margin of 1.5 μm or more.

As one of techniques for extending the focus margin, there is a method of providing a contrast enhancing film on a photoresist film, which is known as contrast enhancing photolithography (CEL). This contrast enhancing film is disclosed in European Patent Publications 361,627, 355,934.
And U.S. Pat. No. 4,702,996, a substance that fades by light, containing a photobleaching compound such as an aryl nitrone and a polymeric binder.

The contrast enhancing film is prepared by dissolving a photobleaching substance or the like in a solvent to prepare a contrast enhancing agent.
Although a uniform film is formed on the photoresist by a coating method such as spin coating, when the solvent that dissolves the photobleaching substance dissolves the photoresist to some extent,
At the interface between the contrast enhancing film and the photoresist film, these films intermix with each other,
In some cases, it may not be possible to form a contrast enhancing film by spin coating directly on the resist because it adversely affects the profile of the photoresist after development. In such a case, there is a gap between the resist film and the contrast enhancing film. It is also practiced to form a water-soluble barrier film such as polyvinyl alcohol.

Even in the CEL process as described above,
Due to recent demands for resist patterns, there is a demand for a method of making a resist pattern as rectangular as possible, increasing a focus margin, and improving resolution at a step portion.

[0008]

Means and Actions for Solving the Problems The inventors of the present invention have conducted diligent studies to meet the above demands, and as a result, a step of forming a water-insoluble resist film on a substrate such as a silicon wafer. A step of forming a contrast enhancing film with a contrast enhancing agent containing the aryl nitrone compound represented by the formula (1), a step of prebaking the resist film before or after the formation of the contrast enhancing film, the resist film and the contrast enhancing film An exposure step of exposing, a step of post-exposure baking after the exposure, a step of removing the contrast enhancing film after the baking, or a step of removing the contrast enhancing film after the exposing and post-exposing the resist film, and a resist Method for forming resist pattern including developing film, and silicon A step of forming a water-insoluble resist film on a substrate such as an air, a step of pre-baking the resist film, a step of forming a barrier film with a water-soluble polymer compound on the resist film after the baking, the following formula on the barrier film A step of forming a contrast enhancing film with a contrast enhancing agent containing the aryl nitrone compound represented by (1), an exposure step of exposing the resist film, the barrier film and the contrast enhancing film, and a post exposure bake after the exposure. A resist including a step of removing the contrast enhancing film and the barrier film after the baking or a step of removing the contrast enhancing film and the barrier film after the exposure and post-exposure baking the resist film, and a step of developing the resist film In the pattern forming method, the above exposure is performed with coherent Data is 0.65
It was found that it is effective to use a reduction projection exposure machine of 0.85.

[0009]

[Chemical 2] (In the formula, R ¹ , R ² and R ³ are the same or different alkyl groups, aryl groups or hydrogen atoms, and R ^{4 to} R ⁸ are the same or different alkyl groups, hydrogen atoms or —COO.
R (R is a hydrogen atom or an alkyl group), but at least one of R ^{4 to} R ⁸ is —COOR. X is R ⁹ O-
Is an alkoxy group represented by, R ¹⁰ R ¹¹ is a dialkylamino group represented by N— or a hydrogen atom, R ⁹ is an alkyl group, and R ¹⁰ and R ¹¹ are the same or different alkyl groups. n has a value of 0, 1 or 2. )

That is, as the exposure machine, a reduction projection exposure machine (stepper) has been generally used conventionally. The coherent factor σ is the ratio of the numerical aperture NA _c of the illumination optical system lens and the numerical aperture NA ₀ of the reduction lens, and is a value obtained from the following equation (2).

Σ = NA _c / NA ₀ (2)

One of the values representing the performance of the reduction projection lens is M
TF (Modulation Transfer Fu)
If the σ value is small and the σ value is small, the MTF at the best focus is large, that is, the contrast of the light passing through the mask on the wafer is large. On the other hand, when the σ value is large, MT at best focus
F is small, that is, the contrast of the light passing through the mask on the wafer is small. However, the larger the σ value, the smaller the decrease in the light contrast at the position away from the best focus.

Conventionally, a stepper has a σ value of 0.5.
Although ˜0.6 has been used, when the σ is larger than that, the present inventor has found that the focus depth increasing effect by the CEL is remarkable. That is, in patterning using a CEL having a line-and-space pattern of 0.30 to 0.40 μm or a hole pattern, which is close to the limit of i-line lithography, σ is 0.65 to 0.8.
By setting it to 5, there is a focus depth expansion effect of 20 to 80% as compared with the case where σ is 0.50 to 0.60, and when σ is set to 0.65 to 0.85,
The depth of focus is improved by 40 to 80% in CEL as compared with the case of a single layer of a resist film without forming a contrast enhancing film, and the line and width of 0.40 to 0.50 μm is also obtained in g-line lithography. In the patterning using the CEL of the space pattern or the hole pattern, by setting σ to 0.65 to 0.85, it is possible to obtain 2 more than when σ is 0.50 to 0.60.
There is an effect of increasing the depth of focus of 0 to 100%, and when σ is set to 0.65 to 0.85, the contrast enhancement film is not formed and the CEL is 50% compared to that of a single resist film. It was found that the depth of focus is improved by 80%, and therefore, when the above contrast enhancer is used and the σ value of the exposure machine is set to 0.65 to 0.85, the effect of increasing the depth of focus is remarkable. They have found the present invention and made the present invention.

In recent years, the σ variable type has become the mainstream of commercially available steppers, and even in the conventional σ fixed type stepper, it is relatively easy to change σ to 0.65 by replacing the illumination system lens. It can be set to ~ 0.85.

The present invention will be described in more detail below. The first resist pattern forming method of the present invention is a method of forming a resist pattern on a substrate such as a silicon wafer, in which a water-insoluble resist film is formed on the substrate. A step of forming a contrast enhancing film on the resist film with a contrast enhancing agent containing the aryl nitrone compound represented by the formula (1), a step of prebaking the resist film before or after the formation of the contrast enhancing film,
An exposure step in which the resist film and the contrast enhancing film are exposed by a reduction projection exposure machine having a coherent factor of 0.65 to 0.85, post exposure baking is performed after the exposure, and the contrast enhancing film is removed after the baking. After the step or the above exposure, the contrast enhancing film is removed,
It includes a step of post-exposure baking the resist film and a step of developing the resist film.
A second resist pattern forming method of the present invention is a method of forming a resist pattern on a substrate such as a silicon wafer, wherein a step of forming a water-insoluble resist film on the substrate, a step of pre-baking the resist film, and a step of baking the resist film. A step of forming a barrier film on the resist film with a water-soluble polymer compound, a step of forming a contrast enhancing film on the barrier film with a contrast enhancing agent containing the aryl nitrone compound represented by the above formula (1), An exposure step in which the resist film, barrier film, and contrast enhancing film are exposed by a reduction projection exposure machine having a coherent fiction of 0.65 to 0.85, post exposure baking is performed after the exposure, and contrast enhancement is performed after the baking. The step of removing the film and the barrier film, or after the above exposure, the contrast enhancing film and the barrier film. Yer film is removed, is intended to include a step of developing the resist film a step of post-exposure baking, and the resist film.

The resist pattern forming method of the present invention is typically used when forming a resist pattern on a silicon wafer, but the method is not limited to this.

When the method of the present invention is applied to a silicon wafer, a pretreatment such as HMDS prime treatment can be first performed according to a conventional method.

Next, in the method of the present invention, a resist agent is applied onto the substrate such as the silicon wafer by means such as spin coating to form a resist film. In this case, the resist agent may be a known one, and any one can be used as long as it can form a water-insoluble resist film, but particularly a positive resist composed of a cresol novolac resin and a naphthoquinone diazide sulfonyl ester compound can be used. preferable.
Although the thickness of the resist film is appropriately selected, it is usually 0.
It is 6 to 20 μm.

In the present invention, a contrast enhancing film is formed on this resist film directly or via a barrier film. For forming the contrast enhancing film, an aryl soluble in an alkali aqueous solution represented by the following formula (1) is used. A contrast enhancing agent containing nitrone is used.

[0020]

[Chemical 3]

Here, R ¹ , R ² and R in the above formula (1) are
³ is an alkyl group, an aryl group or a hydrogen atom. As the alkyl group, for example, those having 1 to 8 carbon atoms such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, sec-butyl group, tert-butyl group and cyclohexyl group are preferable, Of these, a methyl group, an ethyl group, a propyl group, and a butyl group are more preferably used.
As the aryl group, those having 6 to 15 carbon atoms such as phenyl group, substituted phenyl group, naphthyl group, and substituted naphthyl group are preferable, and among them, phenyl group, methylphenyl group, and ethylphenyl group are more preferably used.
R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ are the same or different alkyl groups, hydrogen atoms or —COOR (R is a hydrogen atom or an alkyl group). In this case, the alkyl group is R
Examples thereof are the same as those exemplified for ¹ , R ² and R ³ . At least one of R ^{4 to} R ⁸ is —COO.
R. X is an alkoxy group represented by R ⁹ O-, R ¹⁰
R ¹¹ is a dialkylamino group represented by N- or a hydrogen atom, R ⁹ is an alkyl group, and R ¹⁰ and R ¹¹ are the same or different alkyl groups. Examples of the alkyl group in this case also include the same groups as those exemplified for R ¹ , R ² and R ³ . In addition, n has a value of 0, 1 or 2,
It is preferably 0 or 1.

The method of the present invention uses a contrast enhancer containing the aryl nitrone represented by the above formula (1). In this case, the composition of the contrast enhancer is represented by the above formula (1). 1 to 30% (by weight, the same applies hereinafter) of the contrast enhancing agent
It is preferable to use water or an organic solvent as the balance, preferably 1 to 15%, but in order to increase spin coatability, polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, polyvinylpyrrolidone, polyethylene oxide, amylose, dextran, It is optional to add 0.5 to 30%, preferably 1 to 10% of a water-soluble polymer having an average degree of polymerization of about 2000 to 12000, such as cellulose and pullulan.

When the aryl nitrone compound is dissolved in water, tris (hydroxymethyl) aminomethane, pyridine, triethylamine, tetramethylammonium hydroxide solution, tetraethylammonium hydroxide solution, trimethylethanolammonium hydroxide solution, tetrahydroxyammonium hydroxide is used. Butyl ammonium solution, 2,2 ', 2 "-
Nitroethanol, 1,5-diazabicyclo [4.3.
0] non-5-ene, 1,4-diazabicyclo [2,2]
2,2] octane, 1,8-diazabicyclo [5.4.
0] an organic base such as undec-7-ene is added in an amount of 0.5 to 3
It is optional to add 0%, preferably 1 to 10%, or 0.0001 to 50%, preferably 0.03 to 1% of a surfactant, as long as the effects of the present invention are not impaired.

When the contrast enhancing agent is applied, an appropriate method such as spin coating can be adopted, and the thickness of the contrast enhancing film can be arbitrarily selected, but is usually 0.1 to 1 μm. Is preferred.

Since such a contrast enhancer is soluble in an alkaline aqueous solution, it is possible to apply the resist enhancer to a substrate such as a silicon wafer, and subsequently apply the contrast enhancer by a method such as spin coating. The film does not necessarily have to be formed. Then, pre-baking is carried out according to a conventional method, but this pre-baking can also be carried out after applying the resist agent and then applying the contrast enhancing agent. The conditions for prebaking can be appropriately selected, but are usually 70 to 110 ° C. and 40 to 12 ° C.
The condition of 0 second can be set.

Next, exposure is carried out according to a conventional method, but since the contrast enhancing film is formed in the present invention, the resist profile can be made more rectangular. The exposure conditions can be selected according to the type and thickness of the resist film, but in the present invention, the coherence factor is not 0.5 to 0.6 as in the conventional case as described above. , 0.65 to 0.85 reduction projection exposure machine (stepper) is used, and the above-mentioned object of the present invention is effectively achieved.

Next, in the present invention, post-exposure bake is performed before removing the contrast enhancing film (and barrier film) or post-exposure baking after removing the contrast enhancing film (and barrier film). When post-exposure baking is performed without removing the contrast enhancing film, this can remove the photosensitizer without causing intermixing between the contrast enhancing film and the resist film and reduce the waviness caused by the standing wave. it can.

The conditions of this post-exposure bake can be known conditions, but usually 80 to 130.
It is preferable to set the temperature at 40 ° C. for 40 to 120 seconds. Further, the contrast enhancing film (and the barrier film) can be removed by washing with pure water, for example.

After the post-exposure bake and the removal of the contrast enhancing film (and the barrier film), development is carried out with a developing solution, or the removal and development of the contrast enhancing film (and the barrier film) is carried out using an alkaline developing solution. Can be done at the same time. Finally, a resist pattern can be obtained by rinsing with pure water.

In the resist pattern forming method of the present invention, when a barrier film of a water-soluble polymer compound is formed between the resist film and the contrast enhancing film, the water-soluble polymer compound may be polyvinyl alcohol or polyacryl. Acid, polymethacrylic acid, polyvinylpyrrolidone,
Polyethylene oxide, amylose, dextran,
Cellulose, pullulan and the like can be used.

When the water-soluble polymer compound is applied, an appropriate method such as spin coating can be adopted, and the thickness of this barrier film can be arbitrarily selected, but usually 0.00
The thickness is preferably 5 to 5 μm.

[0032]

According to the method of forming a resist pattern of the present invention, a resist profile can be formed with good rectangularity and a resist pattern having an excellent focus margin can be formed.

[0033]

EXAMPLES Hereinafter, the present invention will be specifically shown by showing Examples and Comparative Examples, but the present invention is not limited to the following Examples. In the following examples, parts are parts by weight.

[Examples 1 to 3] 4.5 parts of aryl nitrone represented by the following formula (3), chemical formula (HOCH ₂ ) ₃ CN
2.0 parts of tris (hydroxymethyl) aminomethane represented by H ₂ , a copolymer of 60% polyvinylpyrrolidone and 40% polyacrylic acid (trade name Luvisc
3.5 parts of olVA-64) was well dissolved in 90 parts of pure water to prepare a contrast enhancer.

[0035]

[Chemical 4]

Photoresist (T manufactured by Tokyo Ohka Kogyo Co., Ltd.)
HMRip3000) on a 6 inch silicon wafer first at 300 rpm for 3 seconds and then 5000r.
Spin coating was performed for 20 seconds at pm, and prebaking was performed at a temperature of 90 ° C. for 90 seconds to form a resist film having a film thickness of 0.86 μm. Then, the above-mentioned contrast enhancing agent is first added to 300
Spin coating was performed at rpm for 3 seconds and then at 4000 rpm for 30 seconds to form a contrast enhancing film having a thickness of 0.18 μm.

In the i-line stepper with NA _c , NA ₀ and σ set to the values shown in Table 1, the line-space spacing is 0.3.
A pattern of 5 μm and a hole pattern of 0.4 μm in diameter are exposed, and then post exposure bake is performed at a temperature of 110 ° C. for 90 seconds, and then the contrast enhancing film is peeled off at 1000 rpm for 20 seconds while discharging pure water onto the wafer. After that, static paddle development was performed with a developer NMD-W (manufactured by Tokyo Ohka Kogyo Co., Ltd.) at 23 ° C. for 60 seconds,
A pure water rinse was performed.

[Comparative Examples 1 to 5] A resist film having a film thickness of 0.86 μm was formed in the same manner as in Example 1, and NA _c , NA ₀ ,
An i-line stepper with σ set to the value shown in Table 1 was used to expose a pattern having a space between lines of 0.35 μm and a hole pattern having a diameter of 0.4 μm.
Post-exposure bake is performed at 0 ° C. for 90 seconds, and the developer is NMD-W (manufactured by Tokyo Ohka Kogyo Co., Ltd.) at 23 ° C. for 60 seconds.
A stationary paddle development was performed for 2 seconds, and a pure water rinse was performed.

[Comparative Examples 6 and 7] In the same manner as in Example 1,
A resist film having a film thickness of 0.86 μm is formed, a contrast enhancing film having a film thickness of 0.18 μm is formed on this resist film, and NA _c , NA ₀ , and σ are set to the values shown in Table 1 for i-line stepper. Then, a pattern in which the distance between the line and the space was 0.35 μm and a hole pattern having a diameter of 0.4 μm were exposed, and thereafter, the same operations as in Example 1 were performed up to the pure water rinsing.

Examples 4 to 6 4.5 parts of aryl nitrone represented by the following formula (4) and polyvinylpyrrolidone 60
% And 40% polyacrylic acid copolymer polymer (trade name: Luviskol VA-64) (4.5 parts) was sufficiently dissolved in a mixed solvent of 45 parts of ethylbenzene and 45 parts of 2-heptanol to prepare a contrast enhancer.

[0041]

[Chemical 5]

Photoresist (T manufactured by Tokyo Ohka Kogyo Co., Ltd.)
SMR-V50) was spin-coated on a 6-inch silicon wafer at 300 rpm for 3 seconds and then at 5000 rpm for 20 seconds, and prebaked at 90 ° C. for 90 seconds to form a resist film having a thickness of 1.08 μm. Then, a 5% aqueous solution of polyvinyl alcohol having a saponification degree of 78% and a polymerization degree of 300 is first added at 500 rpm for 3 seconds.
After that, spin coating is performed at 4000 rpm for 30 seconds to form a barrier film having a thickness of 0.10 μm, and the above contrast enhancing agent is first spin coated at 500 rpm for 3 seconds and then at 4000 rpm for 30 seconds to obtain a thickness of 0.22 μm. The contrast enhancement film of No. 1 was formed.

In the g-line stepper with NA _c , NA ₀ and σ set to the values shown in Table 1, the line-space spacing is 0.4.
After exposing a 0 μm pattern and a 0.45 μm diameter hole pattern, the contrast enhancing film and the barrier film were peeled off at 1000 rpm for 20 seconds while discharging pure water onto the wafer, and then post-exposure was performed at 110 ° C. for 90 seconds. Jour Bake, then Developer NMD-W
(Tokyo Ohka Kogyo Co., Ltd.), static paddle development was performed at 23 ° C. for 60 seconds, and rinsed with pure water.

[Comparative Examples 8 to 12] In the same manner as in Example 4, a resist film having a film thickness of 1.08 μm was formed, and NA _c ,
A g-line stepper having NA ₀ and σ set to the values shown in Table 1 was used to expose a pattern with a space between lines of 0.40 μm and a hole pattern with a diameter of 0.45 μm, and then post-exposure at a temperature of 110 ° C. for 90 seconds. Durbake, 23 with developer NMD-W (manufactured by Tokyo Ohka Kogyo Co., Ltd.)
Static paddle development was performed at 60 ° C. for 60 seconds, and a pure water rinse was performed.

Comparative Examples 13 and 14 In the same manner as in Example 4, a resist film having a film thickness of 1.08 μm was formed, and a barrier film having a film thickness of 0.10 μm was formed on the resist film.
Further, a contrast enhancing film having a film thickness of 0.22 μm was further formed thereon, and NA _c , NA ₀ and σ were set to values shown in Table 1 g
Line stepper provides 0.40μ between line and space
The m pattern and the hole pattern having a diameter of 0.45 μm were exposed, and thereafter, the operations up to pure water rinsing were performed in the same manner as in Example 4.

The cross-sectional profiles of the resist patterns obtained in these examples and comparative examples were observed. In the line-and-space pattern, the focus depth is such that there is no film loss in the pattern and a rectangular profile with separated spaces is obtained, and in the hole pattern, the focus depth is such that a profile with holes at the bottom is obtained. It shows in Table 1.

[0047]

[Table 1]

Claims (2)

[Claims] 1. A method of forming a resist pattern on a substrate such as a silicon wafer, the step of forming a water-insoluble resist film on the substrate, the following formula (1) being formed on the resist film.
A step of forming a contrast enhancing film with a contrast enhancing agent containing an aryl nitrone compound represented by
A step of pre-baking the resist film before or after the formation of the contrast enhancing film, the resist film and the contrast enhancing film having a coherent factor of 0.65 to 0.
An exposure step of exposing light with a reduction projection exposure machine of 85;
A step of post-exposure bake after the exposure and a step of removing the contrast enhancing film after the bake, or a step of removing the contrast enhancing film after the exposure and post-exposure baking the resist film, and a step of developing the resist film A method for forming a resist pattern, comprising: [Chemical 1] (In the formula, R ¹ , R ² and R ³ are the same or different alkyl groups, aryl groups or hydrogen atoms, and R ^{4 to} R ⁸ are the same or different alkyl groups, hydrogen atoms or —COO.
R (R is a hydrogen atom or an alkyl group), but at least one of R ^{4 to} R ⁸ is —COOR. X is R ⁹ O-
Is an alkoxy group represented by, R ¹⁰ R ¹¹ is a dialkylamino group represented by N— or a hydrogen atom, R ⁹ is an alkyl group, and R ¹⁰ and R ¹¹ are the same or different alkyl groups. n has a value of 0, 1 or 2. ) 2. A method of forming a resist pattern on a substrate such as a silicon wafer, the step of forming a water-insoluble resist film on the substrate, the step of prebaking the resist film, and the water-soluble polymer on the resist film after the baking. A step of forming a barrier film with a compound, a step of forming a contrast enhancing film on the barrier film with a contrast enhancing agent containing the aryl nitrone compound represented by the formula (1), the resist film, the barrier film and the contrast enhancing The coherent fictor is 0.65-0.85 through the membrane.
Exposure step by a reduction projection exposure machine, post-exposure bake after the exposure, the step of removing the contrast enhancing film and the barrier film after the baking or removing the contrast enhancing film and the barrier film after the exposure,
A method of forming a resist pattern, comprising the steps of post-exposure baking the resist film and developing the resist film.