JP2002328476A - Method for forming pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a resist pattern having a preferable profile in any resist pattern forming region even when a dense pattern forming region and a sparse pattern forming region are both present on one substrate. SOLUTION: In the method for patterning a chemically amplifying type resist by using an antireflection film containing a photoacid producing agent as a base layer, the antireflection film in the region where a sparse pattern is to be formed is preliminarily subjected to alkali treatment. This suppresses partial trailing or production of an undercut part due to the dense or sparse state of the pattern and realizes high accuracy resist patterning without depending on the density of the pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a pattern in a photolithography process in a semiconductor manufacturing process.

[0002]

2. Description of the Related Art Along with miniaturization of a semiconductor integrated circuit, a photolithography process required in a manufacturing process thereof includes:
It has become necessary to adopt conditions according to the fine level of the pattern.

For example, an exposure light source used for exposing a resist material has been changed from a conventional i-line (wavelength 365 nm) to a shorter wavelength KrF excimer laser (wavelength 248 nm). From a novolak type resist, a chemically amplified type resist has mainly been adopted.

A chemically amplified resist is composed of a resin having a dissolution inhibiting group introduced therein and a photoacid generator (PAG).
or), and by the action of this photoacid generator, an acid is generated inside the resist by the light energy received during exposure. This acid is baked after exposure (PEB).
Bake) diffuses into the resist and acts as a catalyst on the dissolution inhibiting group to dissociate it from the resin, rendering the resist soluble in developer. Due to such amplifying action by the acid, the chemically amplified resist shows high sensitivity.

[0005] Further, since the chemically amplified resist has high transparency, in exposure using light, absorption of the exposure wavelength is small, and light intensity does not decrease in the depth direction. Therefore,
A pattern with high verticality and high resolution can be obtained on the pattern side wall.

However, on the other hand, due to this high transparency, the pattern is easily affected by the reflection of the exposure light from the underlayer, and the pattern is easily deformed by the reflected light.

Therefore, when a chemically amplified resist is used, an antireflection film is usually formed as a base layer below the resist to suppress the influence of reflection of exposure light. This anti-reflection film includes a coating type organic anti-reflection film, sputtering, C
An inorganic antireflection film formed by VD, coating method, or the like is being studied.

However, when an organic anti-reflection film or an inorganic anti-reflection film is used as a base layer of a chemically amplified resist, when patterning is performed, a dense line pattern in which a plurality of line patterns are regularly arranged. It has been pointed out that a resist pattern has a footing in a pattern forming region.

[0009] To solve the problem of tailing of the pattern,
For example, as the anti-reflection film, the one containing a photoacid generator is used, and the chemical bond at the interface between the chemically amplified resist and the anti-reflection film is easily separated, thereby preventing the footing of the pattern. .

In the case where a dense resist pattern in which a plurality of line patterns are regularly arranged at a predetermined pitch is formed by eliminating the footing of the pattern, the pattern can be formed with a wider margin.

[0011]

However, the patterns to be formed are not uniformly formed on the substrate at the same density. In many cases, a dense pattern formation region where a plurality of line patterns are regularly arranged and a sparse pattern formation region where a line pattern exists alone are mixed on the same substrate. The difference in pattern density affects the degree of footing when a resist pattern is formed due to the influence of the optical proximity effect and the like. In general, a dense pattern formation region is more likely to be skirted than a sparse pattern region.

FIG. 4A is a plan view showing an example of forming a resist pattern when a dense pattern formation region and a sparse pattern formation region are mixed on the same substrate. FIG. 4B is a cross-sectional view of the resist pattern taken along a cutting line AA ′ in FIG.

As shown in FIG. 4B, an antireflection film 1 containing a photoacid generator is formed as a base layer of a chemically amplified resist on a substrate 10 on which a thin film to be patterned is formed.
When the resist pattern is adjusted so that the bottom of the resist pattern in the dense pattern formation region 170B where a plurality of line patterns are regularly arranged is eliminated, the undercut is formed in the isolated line pattern formation region 170A. Enters, and the pattern falls easily.

On the contrary, an isolated line pattern forming area 17
At 0A, when the conditions of the underlayer and the baking conditions of the resist are adjusted so as not to cause undercut, the pattern is likely to be skirted in the dense pattern formation region 170B where a plurality of line patterns are arranged.

Further, the step of forming only the pattern in the sparse pattern forming area 170A and the step of forming only the pattern in the dense pattern forming area 170B are performed in separate steps, respectively. However, not only the number of steps is increased, but also a step is formed on the processed surface, and problems such as uneven coating of the photoresist and a decrease in the depth of focus when forming the remaining divided pattern arise.

In view of the above-mentioned problems, an object of the present invention is to provide a method for forming a good resist pattern in any pattern forming region when a dense pattern forming region and a sparse pattern forming region are mixed on the same substrate. The present invention provides a provided pattern forming method.

[0017]

A first feature of the pattern forming method of the present invention is that a first film is formed on a thin film to be patterned.
Forming an antireflection film having an antireflection function with respect to the exposure wavelength of the resist, selectively alkali-treating the antireflection film surface, and forming a first resist film on the antireflection film surface after the alkali treatment. And a step of coating.

According to the first aspect of the present invention, before coating the first resist film, the surface of the anti-reflection film is subjected to a selective alkali treatment in advance, so that the resist is developed after the resist is developed. Can be adjusted.
Therefore, by selecting the density of the pattern formed for each region and the presence or absence of the alkali treatment, it is possible to adjust the resist pattern shape optimally.

A second feature of the pattern forming method of the present invention is that, in the pattern forming method having the first feature, the anti-reflection film is an anti-reflection film containing a photoacid generator. Forming a sparse pattern of the first resist on the alkali-treated area, and forming a dense pattern of the first resist on the non-alkali-treated area of the antireflection film. That is.

According to the second feature of the present invention, when the antireflection film has a photoacid generator, the generated acid is neutralized by the alkali in the alkali-treated region, and Suppress the effect. Therefore, when patterning the first resist formed thereon, it is possible to form a pattern in which undercut does not easily occur. Conversely, on a region that has not been subjected to the alkali treatment, the bond generated at the interface between the antireflection film and the resist is broken by the generated acid, and the occurrence of tailing of the resist pattern can be prevented. Therefore, by forming a sparse pattern on a region that has been subjected to alkali treatment and forming a dense pattern on a region that has not been subjected to alkali treatment, a good resist pattern can be formed in accordance with the pattern density.

According to a third feature of the pattern forming method of the present invention, in the above first or second feature, the step of selectively treating the surface of the antireflection film with an alkali comprises applying a second resist on the antireflection film. A coating step; a step of selectively exposing the second resist; a step of developing the exposed resist; and a step of alkali-treating the exposed surface of the antireflection film exposed by the development. .

According to the third feature of the present invention, the alkali-treated region can be specified by using the second resist patterning step. Therefore, the range of the alkali treatment region can be selected with high accuracy.

A fourth feature of the pattern forming method of the present invention is that, in the above-mentioned third feature, the step of alkali-treating the exposed surface of the antireflection film is performed in the same step as the developing step.

According to the fourth aspect of the present invention, the alkali treatment and the development step can be performed in the same step, so that the load on the steps involved in the alkali treatment can be reduced.

Further, most of the commercially available developers use an aqueous alkaline solution, so that this step can be easily carried out.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In a pattern forming method according to the present embodiment, in a method for patterning a chemically amplified resist using an antireflection film containing a photoacid generator as a base layer, a region where a sparse pattern is to be formed is formed. It is characterized in that an alkali treatment is performed on the antireflection film in advance. According to this method, the occurrence of partial skirting or undercut of the pattern due to the pattern density is suppressed, and highly accurate resist patterning can be performed regardless of the pattern density.

Hereinafter, a more specific description will be given with reference to the drawings.

FIGS. 1A to 1E are process diagrams showing a manufacturing process of the pattern forming method according to the present embodiment.

First, as shown in FIG. 1A, a photoacid generator is formed on the surface of a substrate 10 on which a conductive thin film, a semiconductor thin film or an insulator thin film (not shown) to be patterned is formed. Is coated using a spinner or the like. This anti-reflection film 20
It has an anti-reflection function with respect to the exposure wavelength of the chemically amplified resist, for example, a base resin that absorbs the exposure wavelength of the chemically amplified resist, such as a novolak resin or polyimide, and generates an acid upon receiving the exposure wavelength A photoacid generator such as triphenylsulfonium salt. In addition,
The photoacid generator is 0.1 wt% to 30 wt.
% by weight. The thickness of the antireflection film 20 is
For example, about 0.05 μm to 0.3 μm, preferably 0.1 μm to 0.3 μm.
It is about 1 μm.

Subsequently, baking is performed using a hot plate or the like to make the antireflection film 20 insoluble in the resist solvent.

Further, a positive type resist 30 is coated on the anti-reflection film 20, and
Prebake is performed to evaporate the solvent in the solvent. The positive resist 30 is desirably a resist having a wavelength sensitivity different from that of the chemically amplified resist. For example, a positive resist for i-line is used. Specifically, commercially available IX series manufactured by Nippon Synthetic Rubber Co., for example, IX410 can be used.

Next, as shown in FIG. 1B, in a later step, preliminary exposure is performed through a photomask 40 having an opening in a region where a sparse pattern is to be formed. Positive resist 3
When an i-line resist is used as 0, i-line is used as an exposure light source. Thus, the exposed portion 30A of the positive resist 30 is exposed. At this time, it is desirable that the antireflection film 20 serving as a base layer is not exposed to light.

Subsequently, as shown in FIG. 1C, the positive resist 30 is developed with a developing solution containing an aqueous alkaline solution. The exposed portion 30A dissolves in the developer. Along with this,
The surface of the antireflection film 20 is selectively exposed, and the exposed surface is alkali-treated with a developing solution to become an alkali-treated region 50.

As a developer used at this time, a commercially available developer for a general i-line positive resist can be used. Specifically, for example, a developer AD-10 manufactured by Tama Chemical Co., Ltd. or the like can be used.

As the developing conditions, general conditions may be used.
For example, the developer can be developed by dropping the developer on a substrate at a temperature of about 23 ° C. and spin-coating the solution with a spinner. Of course, the development can also be performed by immersing the substrate in the developer or spraying the developer on the substrate. After the development, the developer remaining on the substrate is washed away with pure water.

Thereafter, only the remaining positive resist 30 is removed using an organic solvent which does not modify the surface of the antireflection film 20 such as ethyl lactate or propylene glycol monomethyl ether which is also used as a resist solvent. As shown in FIG. 1D, the antireflection film 20 having the alkali treatment region 50 remains on the substrate surface.

The selective alkali treatment of the antireflection film 20 can be performed in an independent step. However, as described above, the development of the resist 30 using a commercially available developer containing an aqueous alkali solution is performed. If you perform alkali treatment at the same time,
It is preferable because the selective alkali treatment on the antireflection film 20 can be performed in a process with a small load.

Thereafter, a chemically amplified resist 60 is coated on the anti-reflection film 20, and the resist is patterned using a normal chemically amplified resist. As the positive chemically amplified resist 60, for example, a JSR-V series resist manufactured by Nippon Synthetic Rubber Co., Ltd. can be used. After coating this resist, pre-baking is performed to form a resist film having a thickness of about 0.1 μm. Subsequently, the chemical amplification type resist 60 is pattern-exposed through a photomask by reduction projection exposure or scanning exposure using a KrF excimer laser as a light source.
At this time, a sparse pattern such as a single line pattern is formed on the alkali-treated region 50 of the antireflection film 20, and a dense pattern in which a plurality of line patterns are regularly arranged is formed in other regions. To form

Thereafter, development is performed using a developing solution for the chemically amplified resist 60. After that, using the obtained resist pattern as a mask, RIE (Reactive Ion Etchi
ng) and the like to etch a thin film or the like to be patterned. By removing the remaining resist film after the etching, a desired thin film pattern can be formed on the substrate.

FIG. 2A is a plan view showing an example of a chemically amplified resist pattern obtained in the present embodiment.
FIG. 2B is a cross-sectional view taken along a cutting line AA ′ in FIG. As shown in the figure, a single line pattern 6 is provided on the alkali-treated region 50 of the antireflection film 20.
A sparse pattern such as 0A is formed, and in other areas,
A plurality of line patterns 60B form a dense pattern arranged regularly. For example, in a dense pattern area,
A line and space pattern of about 0.13 μm can be formed.

In general, in the dense pattern formation region, the bottom of the resist pattern is apt to occur, but the antireflection film 20 is exposed on the antireflection film 20 other than the alkali treatment region 50 when the chemically amplified resist 60 is exposed. Since an acid is generated inside, the chemical bond at the interface between the antireflection film 20 and the chemically amplified resist 60 is easily broken, and the pattern obtained by development is a pattern without tailing.

On the other hand, in a sparse pattern formation region, pattern collapse due to an undercut of a resist pattern generally tends to occur, but in a sparse pattern on an alkali treatment region 50, an acid generated in the antireflection film 20 is formed by alkali treatment. Since the alkali component remaining in the film is neutralized, the tailing is likely to occur at the interface between the antireflection film 20 and the chemically amplified resist 60. Therefore, undercut of the resist pattern is suppressed, and pattern collapse can be prevented.

Therefore, as shown in FIG. 2B, in a dense pattern forming region in which a plurality of regular line patterns are arranged, it is possible to form a sharp cross-sectional pattern with a wide margin without tailing. In addition, in a sparse line pattern formation region where a single line pattern is formed, a stable cross-sectional pattern in which pattern collapse or the like does not easily occur can be formed.

As a result, an optimum resist pattern can be formed in both the sparse pattern formation region and the dense pattern formation region formed on the same substrate, and the yield in the process can be improved.

In the above-described embodiment, the developing solution for the i-line resist is used as the alkali solution used for the alkali treatment of the anti-reflection film. Any alkaline aqueous solution containing potassium hydroxide, sodium hydroxide, ammonia or the like can be used.

In the above-described embodiment, either a negative type resist or a positive type resist may be used for resist patterning used when only a predetermined region of the antireflection film 20 is subjected to alkali treatment. Similarly, for a chemically amplified resist, either a negative type or a positive type can be used.

In the patterning for specifying the alkali-treated region on the antireflection film 20, the photomask used is determined by referring to the design pattern of the photomask used for patterning the final thin film. The opening pattern may be formed according to the degree of density. For example, in advance, the relationship between the pattern density and the occurrence of undercut in the chemically amplified resist after development is experimentally determined, the value of the pattern density at which undercut occurs is specified, and this pattern density is used as a boundary value. In regions where the pattern density is lower than this, an opening pattern for alkali treatment may be formed in the antireflection film. For example, in the case of the above-described embodiment, at least a region where the distance between adjacent lines is 0.3 μm to 0.5 μm or more is treated as a region having a low pattern density, and alkali treatment is performed.

As described above, at the time of manufacturing a photomask, at the same time as designing a pattern to be actually formed on a thin film,
It is preferable to design a pattern for alkali treatment according to this.

FIG. 3 shows an organic anti-reflection film used in the present embodiment and an inorganic SOG (Spin On Anti-Reflection Film) which has recently been considered to be used as an anti-reflection film for a chemically amplified resist.
5 is a graph showing the effect of alkali treatment on a (Glass) film. Here, the alkali treatment is a treatment in which a developing solution of an i-line resist is coated on each reflective film with a spinner or the like and then washed with pure water. The graph of FIG. 3 shows the change in the contact angle of pure water on each antireflection film before and after the alkali treatment.

In the antireflection film used in this embodiment,
By performing the alkali treatment, the contact angle of pure water is greatly reduced, and the wettability is increased by the alkali treatment. This supports the fact that, as already described, the acid generated in the antireflection film by the alkali treatment is neutralized, and the condition is liable to cause the trailing of the droplet.
In addition, if the conditions for irradiating exposure light and generating acid are set as follows:
The presence or absence of the alkali treatment is expected to make a more significant difference.

On the other hand, in the case of the SOG film, unlike the case of the organic antireflection film containing the photoacid generator, the contact angle of the water droplet was rather increased by performing the alkali treatment. In other words, this suggests that the resist pattern does not have a tail in the alkali-treated region. That is, at least the presence or absence of alkali treatment indicates that the degree of footing of the resist pattern can be adjusted. still,
By adjusting the time and temperature of the alkali treatment, it is possible to design these conditions to more optimal conditions. Therefore, when the SOG film is used, the alkali treatment is not performed in a region where a sparse pattern is formed, but the alkali treatment is performed in a region where a dense pattern is formed.
The pattern tailing can be suppressed, which can be used to improve the resist pattern.

Further, in the above-described embodiment, when forming a thin film pattern, a chemically amplified resist which requires an antireflection film is used. In the case of a resist used as a base film, the degree of footing of the resist pattern can be adjusted by similarly performing an alkali treatment on the surface of the antireflection film.

As described above, the pattern forming method of the present invention has been described with reference to the present embodiment. However, the present embodiment is not limited to the description, and various improvements and substitutions are possible. This is obvious to those skilled in the art.

[0054]

As described above, according to the pattern forming method of the present invention, when a dense pattern and a sparse pattern are mixed on the same substrate, alkali treatment on the antireflection film is selectively performed. Thereby, a good resist pattern corresponding to the density of each pattern can be formed.

[Brief description of the drawings]

FIG. 1 is a process chart showing a pattern forming method according to an embodiment.

FIGS. 2A and 2B are a plan view and a cross-sectional view of a resist pattern formed by the pattern forming method according to the present embodiment. FIGS.

FIG. 3 shows a contact angle of pure water when an alkali treatment is performed on the antireflection film and the SOG film according to the present embodiment.

FIG. 4 is a plan view and a cross-sectional view of a resist pattern produced by a conventional pattern forming method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Substrate 20 Antireflection film 30 Resist 40 Photomask 50 Alkali processing area 70 Resist pattern

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H025 AA03 AA04 AB16 AC04 AC08 AD03 BE00 BE10 BG00 DA34 FA17 5F046 HA07 JA04 JA22 LA01 LA14 LA18 PA03 PA07 PA19

Claims (5)

[Claims] A step of forming an anti-reflection film having an anti-reflection function with respect to an exposure wavelength of a first resist on a thin film to be patterned; and a step of selectively subjecting the anti-reflection film surface to an alkali treatment. Coating the surface of the antireflection film after the alkali treatment with the first resist film. 2. The anti-reflection film is an anti-reflection film containing a photoacid generator. Further, on the region of the anti-reflection film which has been subjected to alkali treatment by exposure and development, the first resist is Forming a sparse pattern, and forming a dense pattern of the first resist on a region of the antireflection film that has not been subjected to alkali treatment. Forming method. 3. The step of selectively alkali-treating the surface of the anti-reflection film, the step of coating a second resist on the anti-reflection film, and the step of selectively exposing the second resist. The pattern forming method according to claim 1, further comprising: developing the resist after the exposure; and performing an alkali treatment on an exposed surface of the antireflection film exposed by the development. . 4. The step of treating the exposed surface of the antireflection film with an alkali using an alkali developing solution used in the step of developing.
4. The pattern forming method according to claim 3, wherein the step is performed in the same step as the step of developing. 5. The method according to claim 1, wherein the first resist is a chemically amplified resist.
The pattern forming method according to the above item.