JPH09171951A - Formation of resist pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a resist pattern excellent in adhesion to a substrate. SOLUTION: The surface of a substrate is treated with a surfactant containing fluorine atoms and coated with a resist to form a resist film. The resist film is then subjected to pattern exposure and developed using a developer. Since the substrate is subjected to surface treatment, difference between the polarity on the surface of the substrate and the polarity on the surface of the resist film formed thereon is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a resist pattern used for fine processing of semiconductor devices.

[0002]

2. Description of the Related Art In recent years, as the degree of integration of semiconductor integrated circuits such as LSI has increased, it has become essential to form fine patterns. A fine pattern is formed on a substrate such as a semiconductor wafer by a lithography technique using a resist, and with the miniaturization of the pattern, improving the adhesion between the substrate and the resist film has become an important issue. It was For example, if the adhesiveness between the substrate and the resist film is poor, peeling of the pattern and flow of the pattern occur during development. In order to solve such problems,
Generally, hexamethyldisilazane treatment (OAP treatment)
Applying the process called as to the substrate before resist coating,
It is widely practiced to improve the adhesion between the resist pattern and the substrate.

Although it is clear that the OAP treatment enhances the adhesion between the substrate and the resist film,
The degree of surface treatment such as treatment time is ambiguous based on experience. Therefore, the optimum processing time according to the type of resist applied on the substrate has to be decided after trial and error.

It has also been found that, depending on the substrate on which the resist pattern is formed, a new problem will occur in the subsequent steps even if no pattern flow is observed during pattern development. For example, when a resist pattern is formed on a chrome mask used as a semiconductor mask or the like, pattern flow does not occur during development. However, when selectively patterning the chrome film by wet etching using this resist pattern as an etching mask, the etching should proceed isotropically at the edges of the resist pattern and undercut should not occur, and should not be etched. The chrome layer dissolves. Therefore, after the resist is peeled off, the corners of the chrome layer are rounded, which makes it difficult to accurately transfer the resist pattern to the chrome film. This is because the adhesiveness between the resist pattern and the substrate is not sufficient, and the etching solution permeates into the interface between the pattern and the substrate.

When the etching solution penetrates in this way and side etching occurs in the chromium film pattern, the shape of the chromium film corresponding to the end of the pattern cannot be formed as designed. In particular, it becomes difficult to accurately transfer a pattern such as an ultrafine line or a minute contact hole formed on the resist pattern onto the chromium film. Anomalies in the chrome shape cause large deviations from the design dimensions, and regions with different transmittances are formed, so they must be avoided as much as possible in the semiconductor mask manufacturing process.

It is generally known that it is effective to bake the resist pattern before etching in order to prevent the etching solution from penetrating the resist-chromium substrate interface. However, this baking process is not perfect, and does not necessarily solve the problem for all resist types applied.

Moreover, hexamethyldisilazane treatment, which is known as an effective means for improving the adhesion between the resist pattern and the substrate, is also effective for chromium substrates.
Almost no effect. As described above, it is extremely difficult at present to suppress the permeation of the etching solution into the interface due to the insufficient adhesion between the resist pattern and the chromium substrate.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and provides a resist pattern forming method capable of forming a resist pattern having excellent adhesion to a substrate. The purpose is to do.

[0009]

In order to solve the above problems, the present invention provides a step of treating the surface of a substrate with a surface treatment agent containing a fluorine atom, and applying a resist on the treated substrate. Forming a resist film, performing a pattern exposure on the resist film, and developing the resist film after the exposure with a developing solution. Provided is a resist pattern forming method characterized in that a difference in polarity between the surface and the surface of a resist film formed on this substrate is suppressed.

Hereinafter, the present invention will be described in detail. In the resist pattern forming method of the present invention, prior to forming a resist film on a substrate, a surface treatment agent containing a fluorine atom is used so that the polarity of the substrate surface becomes approximately the same as the polarity of the resist film surface. To control.

The surface treatment agent used in the present invention is
At least one of the compound represented by the general formula (1) and the compound represented by the general formula (2) shown below is preferable.

[0012]

Embedded image (In the general formula (1), R ¹ is a methyl group or a methoxy group, m is an integer of 1 or more, and n is an integer of 0 or more.)

[0013]

Embedded image (In the general formula (2), R ² is a methyl group or a chlorine atom, p is an integer of 1 or more, and q is an integer of 0 or more.) As a compound represented by such a general formula , For example, CF ₃ C ₂ H ₄ SiCl ₃ , CF ₃ C ₂ H
₄ Si (OMe) ₃ , CF ₃ (CF ₂ ) ₅ C ₂ H ₄ Si
Cl ₃ , CF ₃ (CF ₂ ) ₅ C ₂ H ₄ Si (OMe)
₃ , CF ₃ (CF ₂ ) ₇ C ₂ H ₄ SiCl ₃ , CF ₃
(CF ₂ ) ₇ C ₂ H ₄ Si (OMe) ₃ , CF ₃ (CF
₂ ) ₇ C ₂ H ₄ SiMeCl ₂ , and CF ₃ (CF
₂ ) ₇ C ₂ H ₄ SiMe (OMe) _{2 and the} like. However, Me in the chemical formula here represents a methyl group, and the same applies to the following.

In the present invention, such a compound can be used as a vapor of a stock solution or an alcohol solution such as methanol for surface treatment of a substrate. When using the vapor of the stock solution, this stock solution and the substrate in a closed container,
For example, the surface treatment can be carried out by leaving it for 10 minutes or longer, preferably 30 minutes or longer. By heating the substrate after the surface treatment at 60 ° C. or higher and 200 ° C. or lower, the effect of the surface treatment is increased. Here, the reason why the processing temperature is set to 60 ° C. or higher and 200 ° C. or lower is that if the temperature is lower than 60 ° C., the effect is small, and if the temperature exceeds 200 ° C., the resist pattern may be peeled off. The temperature of this treatment can be appropriately selected according to the treated substrate, the surface treatment agent, and the like. For example, a chromium oxide substrate is CF ₃ (CF ₂ ) ₇ C ₂ H ₄ SiMe.
When treated with (OMe) ₂ , it is 5-10 at 100 ° C.
By heating for about a minute, the effect of surface treatment can be significantly increased.

On the other hand, when the surface treatment agent is used as an alcohol solution, the substrate surface can be treated by immersing the substrate in this solution. As the alcohol, propanol, ethanol, etc. may be used. The substrate after immersion may be dried in an oven or the like, but in this case, it is necessary to take care to avoid adhesion of dust or the like on the substrate.

The substrate used in the resist pattern forming method of the present invention is a mask blank in which chromium or chromium oxide is vapor-deposited on quartz, and after forming a resist pattern, this pattern is used as an etching mask to wet a substrate or the like. All substrates that include the step of performing etching can be mentioned.

In order to determine the polarity of the substrate surface after the surface treatment, it is effective to measure the contact angle between the substrate and pure water with a surface contact angle meter. In the present invention, if the contact angle between the surface of the substrate and pure water after the surface treatment becomes excessively large and the substrate becomes completely hydrophobic, it becomes difficult to apply the resist solution having polarity.

Therefore, the contact angle of pure water with respect to the substrate after the surface treatment is preferably within ± 40 ° of the contact angle of pure water with respect to the resist film formed on the substrate, and more preferably within ± 30 ° C. .

On the substrate thus surface-treated,
The method of forming the resist pattern will be described below. The resist that can be used in the method of the present invention is not limited as long as it has a composition that can be patterned by visible light, ultraviolet light, or electron beam, pattern exposure such as X-ray, but the resist pattern forming method of the present invention is In particular, it is particularly effective when a hydrophobic resist is used. Moreover, these resists can be used by selecting a positive type or a negative type according to the purpose.

Specifically, as a positive resist, a resist containing an alkali-soluble compound as a base polymer and a quinonediazide compound as a photosensitizer; a PMM in which a part of the polymer constituting the resist is decomposed by actinic radiation
A, a resist having a polyacrylate skeleton such as EBR-9; and a chemically amplified positive resist. Examples of negative resists include isoprene-based resists using azide-based compounds as photosensitizers, phenolic resin-based resists, and chemically amplified resists using melamine derivatives as curing agents. It is not limited to.

Such a resist is dissolved in an organic solvent, coated on the surface-treated substrate with, for example, a spin coater, and dried by heating to form a resist film. The heating temperature and time can be appropriately selected according to the type of resist, the organic solvent used, and the like. For example, in the case of a chemically amplified resist, it is preferable to perform heating at 90 to 130 ° C. for about 1 to 5 minutes.

Subsequently, pattern exposure is performed on the resist film. As an exposure light source, ultraviolet rays such as g rays and i rays, K
A deep UV light of an rF or ArF excimer laser, an electron beam, an X-ray, or the like can be used, and a method of performing selective exposure through a predetermined mask pattern, or a method of drawing with pattern data without using a mask Either of them is selected according to the light source.

Next, if necessary, the exposed resist film is heat-treated (baked) by using a hot plate, an oven, or infrared irradiation. The baking temperature can be appropriately selected according to the type of resist. For example, in the case of a chemically amplified resist, the baking temperature is about 50-
It is preferably in the range of 130 ° C.

After that, the resist film which has undergone the above steps is developed by a dipping method or the like. The developer used here can be appropriately selected according to each resist. For example, in the case of a chemically amplified resist, an inorganic or organic alkaline aqueous solution, an organic solvent or the like can be used.

The developed substrate and resist film are appropriately rinsed with water or the like, and then dried to obtain a desired pattern. If necessary, this resist pattern may be subjected to heat treatment at about 140 ° C. for about 3 to 5 minutes.

Using the resist pattern formed as described above as an etching mask, the substrate is immersed in, for example, an acidic etching solution to perform wet etching, and this resist pattern is accurately transferred to the member to be etched. be able to.

This is considered as follows. In the resist pattern forming method of the present invention, by subjecting the substrate before coating the resist to a surface treatment agent containing a fluorine atom, the polarity of the substrate surface is changed to a resist film formed on the substrate. It is adjusted to the same level as the surface polarity. Therefore, the adhesion between the substrate and the resist pattern formed on the substrate can be significantly increased.

That is, using the resist pattern formed by the method of the present invention as an etching mask,
When patterning a chrome film etc. by wet etching, it is possible to prevent the etching solution from penetrating the interface between the resist pattern and the member to be etched, and transfer the desired pattern to the member to be etched accurately. Becomes Therefore, the method of the present invention can provide a resist pattern capable of forming an ultrafine pattern on a chromium film or the like with extremely high accuracy.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below by showing Examples and Comparative Examples of the present invention. Example 1 First, as a surface treatment agent, CF ₃ C ₂ H _{4 was used.}
Using an undiluted solution of Si (OMe) ₃ , a 5-inch chromium mask substrate was left for a predetermined time in a container containing this surface treatment agent for surface treatment. The processing time was set to two types, 10 minutes and 30 minutes. Furthermore, for some, the surface-treated substrate was baked in a baker at 100 ° C for 10
Heat treatment was performed for 4 minutes to prepare four types of substrates.

For comparison, a substrate not subjected to surface treatment and four types of substrates subjected to hexamethyldisilazane treatment under the same conditions as described above were prepared. The contact angle of pure water with respect to the substrate surface thus obtained was measured, and the obtained results are summarized in Table 1 below.

[0031]

[Table 1]

As shown in Table 1, the contact angle between the substrate not surface-treated and pure water is only 18 °,
When the surface treatment of the substrate is performed with a surface treatment agent containing a fluorine atom, the contact angle between the substrate and pure water is 2 after 10 minutes.
It became 5 °, and after 30 minutes, it became as large as 30 °. By subjecting these substrates to heat treatment after surface treatment, the contact angle with pure water is further increased, reaching a maximum of 62 °.

On the other hand, when the hexamethyldisilazane treatment is performed, the contact angle between the substrate and pure water is 25 ° at the maximum.
This value does not increase even after the heat treatment.
That is, the contact angle between the substrate and pure water can be increased by treating the substrate surface with the surface treatment agent containing a fluorine atom.

A resist pattern was formed on the thus surface-treated substrate by the following procedure. First, a resin 58w in which the hydroxyl group of polyvinylphenol having a molecular weight (Mw = 31000) is protected with 30% tert-butyl acetate group
t%, 35 wt% of polyvinylphenol having a molecular weight (Mw = 9600), and 7 wt% of triphenylsulfonium triflate as a photoacid generator were dissolved in methyl 3-methoxypropionate as a solvent to obtain a resist solution. . In this resist, the acid generated by irradiation with light, X-rays or high-energy electron beams decomposes the tertiary butyl acetate group, which is a dissolution inhibiting group, and the exposed part becomes soluble in an alkaline solution to form a pattern. Is a positive type chemically amplified resist in which is formed.

This resist solution was applied to each surface-treated substrate with a spinner to a film thickness of 0.5 μm, and 100
The resist film was formed by baking at 5 ° C. for 5 minutes. Then, a high energy electron beam (accelerating voltage 15 keV) having a beam diameter of 0.25 μm was scanned under the condition of 4 μC / cm ² to draw a line-and-space pattern and a contact hole on the resist film. Then, 6
After performing post-exposure heating (PEB) at 0 ° C. for 5 minutes, it was developed with a tetramethylammonium hydroxide (TMAH) aqueous solution (2.38 wt%) to form a resist pattern. In addition to the obtained resist pattern, 140
Post bake was performed at 5 ° C. for 5 minutes.

A resist pattern was formed on the untreated substrate and the OAP-treated substrate in the same manner as described above. Using the obtained resist pattern as an etching mask, the chromium film was selectively etched with an cerium ammonium nitrate etching solution, and the resist pattern was transferred to this chromium mask to obtain a sample.

For each sample, the interface between the resist pattern and the chromium film was observed with a scanning electron microscope to measure the penetration distance of the etching solution from the end of the pattern.
The results obtained are summarized in Table 2 below.

[0038]

[Table 2]

As shown in Table 2 above, when the chromium film is wet-etched by using the resist pattern formed on the substrate not subjected to the surface treatment as an etching mask, the resist pattern and the chromium film are separated from each other. The penetration of the etching solution into the interface reaches 0.35 μm. On the other hand, when the resist pattern formed by the method of the present invention is used as the etching mask, the penetration of the etching solution into the interface is 0.20 μm.
Can be suppressed.

On the other hand, in the case of the OAP-treated substrate, the penetration of the etching solution into the interface between the resist pattern and the chromium film has not been improved much as compared with the case of the untreated substrate. It can only be suppressed to 30 μm.

Further, in order to investigate the effect of the hexamethyldisilazane treatment, the same chromium mask as described above was treated for a long time of 48 hours, and then a resist pattern was formed in the same manner as described above. Next, when the chromium substrate was wet-etched using this resist pattern as an etching mask and the interface between the resist pattern and the chromium substrate was observed, the etching solution permeation into the interface was treated with hexamethyldisilazane for 30 minutes. It was equivalent to the case. As described above, the hexamethyldisilazane treatment cannot sufficiently enhance the adhesion between the substrate and the resist pattern even if the treatment time is extended.

Therefore, it has been clarified that the treatment of the substrate with the surface treatment agent containing a fluorine atom has a far superior effect to the case of the hexamethyldisilazane treatment.

The contact angle of pure water with respect to the resist film formed of the chemically amplified electron beam resist used in this example was 75 °. As shown in Table 1 above, by treating the substrate surface with a surface treatment agent containing a fluorine atom, the contact angle between the substrate surface and pure water is changed to the contact angle between this resist film and pure water. You can get closer. Then, it is clear from the results of Table 2 above that penetration of the etching solution into the interface between the resist pattern formed on the substrate having such a contact angle and the substrate is significantly suppressed. (Example 2) As a surface treatment agent, CF ₃ (CH ₂ ) ₇ C was used.
_{Using a 2} H ₄ SiMe (OMe) ₂ stock solution, a 5-inch chrome mask substrate was left for a predetermined time in a container containing this surface treatment agent to perform surface treatment on the substrate. The processing time was two types, 10 minutes and 30 minutes. Further, for some of the substrates, the surface-treated substrates were heat-treated in a baker at 100 ° C. for 10 minutes to prepare four types of substrates.

For comparison, a substrate not subjected to surface treatment and four types of substrates subjected to hexamethyldisilazane treatment under the same conditions as described above were prepared. The contact angle of pure water with respect to the substrate surface thus obtained was measured, and the obtained results are summarized in Table 3 below.

[0045]

[Table 3]

As shown in Table 3, the contact angle between the substrate not surface-treated and pure water is only 18 °,
When the surface treatment of the substrate is performed with a surface treatment agent containing a fluorine atom, the contact angle between the substrate and pure water is 3 after 10 minutes.
It becomes 0 °, and after 30 minutes, it has increased to 40 °. By subjecting these substrates to heat treatment after surface treatment, the contact angle with pure water is significantly increased, reaching 90 ° at the maximum.

On the other hand, when the hexamethyldisilazane treatment is performed, the contact angle between the substrate and pure water is 25 ° at the maximum.
This value does not increase even after the heat treatment.
That is, it is understood that the contact angle between the substrate and pure water can be increased by treating the substrate surface with the surface treatment agent containing a fluorine atom.

A resist pattern was formed on the thus surface-treated substrate by the same procedure using the same chemically amplified resist as in Example 1 described above, and the untreated substrate and OAP treatment were performed. A resist pattern was similarly formed on the applied substrate.

Using the obtained resist pattern as an etching mask, the chrome film was selectively etched with a cerium ammonium nitrate etching solution,
A resist pattern was transferred to this chrome mask to obtain a sample.

For each sample, the interface between the resist pattern and the chromium film was observed with a scanning electron microscope to measure the penetration distance of the etching solution from the end of the pattern.
The results obtained are summarized in Table 4 below.

[0051]

[Table 4]

As shown in Table 4 above, when the chromium film is wet-etched using the resist pattern formed on the substrate not subjected to the surface treatment as an etching mask, the resist pattern and the chromium film are not separated from each other. The penetration of the etching solution into the interface reaches 0.35 μm. On the other hand, when the resist pattern formed by the method of the present invention is used as an etching mask, the penetration of the etching solution into the interface is 0.10 μm.
Can be suppressed.

On the other hand, in the case of the OAP-treated substrate, the penetration of the etching solution into the interface between the resist pattern and the chromium film has not been improved much as compared with the case of the untreated substrate. It can only be suppressed to 30 μm.

The contact angle between the resist film used in this example and pure water was 75 °, as in Example 1. It is shown in Table 3 above that the contact angle between the substrate and pure water reaches 90 ° by treatment with the surface treatment agent containing a fluorine atom. Is over. However, with a resist pattern formed on a substrate having a large contact angle with pure water,
It is shown in Table 4 that the penetration of the etching solution into the interface with the substrate is suppressed to only 0.10 μm.

Therefore, even if the contact angle between the surface of the substrate and the pure water is larger than the contact angle between the resist film and the pure water to some extent, the etching solution does not soak into the interface between the resist pattern and the substrate. It became clear that the suppressing effect was obtained.

That is, by treating the substrate surface with a surface treatment agent containing a fluorine atom, the polarity of the substrate surface is
Since the polarity of the resist film surface can be approximated, the adhesiveness between the substrate and the resist pattern was significantly increased. Therefore, it becomes possible to suppress the infiltration of the etching liquid into the interface between the substrate and the resist pattern during wet etching using the obtained resist pattern as an etching mask. (Example 3) As a surface treatment agent, CF ₃ C ₂ H ₄ Si was used.
Using a 2 wt% methanol solution of (OMe) ₃ , a 5-inch chromium substrate was immersed in this solution for 30 seconds, and then heat-treated in an oven at 200 ° C. for 10 minutes. When the surface contact angle of the substrate obtained by such a treatment with pure water was measured and it was 55 ° to 70 °, there was some unevenness in the treatment on the substrate surface, but it could be confirmed that the surface treatment was performed. It was

A resist pattern was formed on the obtained substrate by the same procedure using the same chemically amplified resist as in Example 1 described above. Using this resist pattern as an etching mask, the chrome mask was etched with a cerium ammonium nitrate etching solution. After the etching, the interface between the resist pattern and the chromium film was observed with a scanning electron microscope. As a result, the amount of the etching solution soaked into the interface between the resist pattern and the chromium film was 0.20.
μm. Since the amount of penetration into the interface between the resist pattern on the substrate not subjected to surface treatment and the chromium film is 0.35 μm, the surface treatment with this surface treatment agent improves the adhesion between the resist pattern and the chromium substrate, It is clear that the penetration of the etching solution was suppressed.

[0058]

As described above, according to the present invention,
It is possible to form a resist pattern having significantly improved adhesion to a substrate, particularly a chrome mask substrate for producing a reticle.

Therefore, when the chromium substrate is selectively patterned by wet etching using the resist pattern formed by the method of the present invention as an etching mask, the etching solution is immersed in the interface between the resist pattern and the chromium substrate. Since the entrapment is suppressed, the resist pattern can be accurately transferred to the chrome substrate.

Therefore, the pattern forming method is
It is extremely useful for producing reticles in the manufacturing process of semiconductor devices and the like, and its industrial value is enormous.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shin Nakase 1 Komukai Toshiba-cho, Kouki-ku, Kawasaki-shi, Kanagawa Incorporated Toshiba Research and Development Center

Claims (3)

[Claims] 1. A step of treating the surface of a substrate with a surface treatment agent containing a fluorine atom, a step of applying a resist on the treated substrate to form a resist film, and pattern exposing the resist film. And a step of developing the resist film after the exposure with a developing solution. By the surface treatment of the substrate, a difference in polarity between the substrate surface and the resist film surface formed on the substrate is suppressed. A resist pattern forming method characterized by being suppressed. 2. The resist pattern according to claim 1, wherein the contact angle of pure water with respect to the surface of the substrate after the treatment is within ± 40 ° of the contact angle of pure water with respect to the surface of the resist film formed on the substrate. Forming method. 3. The surface treating agent containing a fluorine atom is at least one compound represented by the following general formula (1) and a compound represented by the following general formula (2). Resist pattern forming method. Embedded image (In the general formula (1), R ¹ is a methyl group or a methoxy group, m is an integer of 1 or more, and n is an integer of 0 or more.) (In the general formula (2), R ² is a methyl group or a chlorine atom, p is an integer of 1 or more, and q is an integer of 0 or more.)