JPH11233404A - Method for forming photo-resist pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent, substantially, deactivation of acid even when acid is neutralized which is generated at a resist surface part during or at resist/ substrate interface part when coating. SOLUTION: A chemical amplification type negative resist film 2 is coated on a substrate 1, then a solvent 4 of propyleneglycolmonomethyletheracetate(PGMEA) is sprayed on the substrate 1, so that the distribution of solvent concentration is larger at a resist surface part than at a resist/substrate interface part in the coated resist film 2, and after it is supplied to the resist film 2, resist film 2 is exposed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a photoresist (hereinafter simply referred to as "resist") pattern, and more particularly to a method of forming a resist pattern used for manufacturing a semiconductor device and a mask for manufacturing the semiconductor device. About the method.

[0002]

2. Description of the Related Art The integration degree of LSIs (Large Scale Integrated Circuits), which are representative of semiconductor devices, has been dramatically increased as higher functionality and higher performance are required. Along with this, microfabrication technology for manufacturing LSIs has rapidly advanced. Such fine processing technology depends on a so-called lithography technology, and the limit of fine processing is determined by the pattern accuracy of a resist pattern formed on a substrate such as a semiconductor substrate.

[0003] Among LSIs, DRAM (Dynamic Random Access), which is a kind of memory element with a remarkably high integration, is particularly high.
Memory), for example, a memory having a large capacity of 256 Mb (megabit) is being developed. However, it is necessary to form a fine pattern wiring having a width of about 0.25 μm in such a memory element. For forming a pattern, a higher level of pattern accuracy is required.

In order to form such a highly accurate resist pattern, the material of the resist is a major problem. Conventional novolak-based resists are generally used for this kind of purpose, but it has become clear that it is difficult to cope with applications requiring high pattern accuracy as described above. Has developed and widely used a resist called a chemically amplified type.

[0005] A chemically amplified resist is composed of, for example, a cresol novolak resin or the like as a base resin and, in the case of a negative resist, a crosslinking agent and an acid generator added thereto. An acid (H ⁺ ) is generated from the acid generator by performing exposure treatment by irradiating an electromagnetic wave. Then, by performing a heat treatment (baking) after the exposure treatment, the crosslinking agent causes a crosslinking reaction between the base resins using the acid as a catalyst to increase the molecular weight (to reduce the number of molecules to 3).
Dimensional network structure). As a result, the exposed area of the resist becomes insoluble in the developing solution, so that a negative resist pattern is formed. Further, an acid is generated at the time of the cross-linking reaction, which acts to cause the next cross-linking reaction, so that the reaction proceeds with a small amount of exposure, so that there is an effect that a highly sensitive resist pattern can be formed.

On the other hand, in the case of the same resist as the positive type, the resist is constituted by adding a dissolution inhibitor and an acid generator to a base resin. The acid generated from the generator breaks the bond of the dissolution inhibitor bound to the base resin. As a result, the exposed area of the resist becomes soluble in the developing solution, so that a positive resist pattern is formed. Also in this case, an acid is generated during the cleavage reaction of the dissolution inhibitor, so that a highly sensitive resist pattern can be formed as in the case of the negative type.
As described above, by using a chemically amplified resist, it is possible to form a resist pattern with high pattern accuracy, and it is possible to obtain effects such as high resolution, high sensitivity, and high dry etching resistance.

FIG. 4 shows a conventional method of forming a resist pattern using a chemically amplified resist (negative type in this example). FIGS. 4A to 4D are process diagrams. First, as shown in FIG. 1A, a chemically amplified resist 22 is applied on a substrate 21 made of a semiconductor substrate or the like by spin coating (spin coating). Next, as shown in FIG. 2B, the solvent in the applied resist 22 is evaporated, the efficiency of the photochemical reaction by exposure is increased, and the resist 2 is removed.
Pre-baking (heat treatment) of the resist 22 is performed for the purpose of improving the adhesiveness between the substrate 2 and the substrate 21.

Next, as shown in FIG. 1C, an exposure process is performed by irradiating the resist 22 with an electron beam 23 using an electron beam exposure apparatus. As a result, acid is generated in the exposed region 22a of the resist 22 irradiated with the electron beam 23. Next, as shown in FIG. 2D, post bake (heat treatment (Post Exposure Bake)) is performed to promote a crosslinking reaction in the exposed region 22a of the resist 22. Next, by performing a developing process, patterning is performed to form a resist pattern.

However, if the time from the above-described exposure processing to post-bake (reservation time) becomes long, that is, if post-bake is not performed immediately after the exposure processing, the resist surface or the resist / substrate interface may not be used. In addition, the generated acid reacts with an alkaline substance such as ammonia in the atmosphere to be neutralized, and so-called acid deactivation occurs. For this reason, when a development process is performed thereafter, a resist pattern with high pattern accuracy cannot be obtained due to the influence of acid deactivation.

FIG. 5 shows the inconvenience when acid deactivation occurs on the surface of the resist. FIG. 5A shows the result of development processing of the resist. FIG.
(B) shows the result of developing the resist in the case of the positive type. In the former case, the cross-linking reaction does not proceed on the resist surface portion, so that the resist pattern 24 has a shoulder shape lower than an ideal resist pattern. On the other hand, in the latter case, since the cleavage reaction of the dissolution inhibitor does not proceed, a T-top having a protruding eaves on the resist surface portion is more likely to be formed than in an ideal resist pattern.
This results in a resist pattern 25 having a shape. On the other hand, when acid deactivation occurs at the resist / substrate interface,
In the negative type, constriction occurs at the interface, and the resist pattern after the development processing has an inverted tapered shape. On the other hand, in the positive type, since the pattern becomes thick at the interface, the resist pattern after the development processing has a tapered shape.

As described above, the chemically amplified resist can form a resist pattern with high pattern accuracy, but has a drawback that it is easily affected by the conditions of the surrounding atmosphere to be used.

[0012] A method of forming a resist pattern using a chemically amplified resist designed to make up for such a disadvantage is as follows.
For example, it is disclosed in Japanese Patent Application Laid-Open No. 4-281456. FIG. 6 is a process chart showing a method of forming a resist pattern described in the publication in the order of steps. First, as shown in FIG. 1A, a spin coating method is performed on a substrate 31.
A chemically amplified resist 32 is applied. Next, as shown in FIG. 2B, an oxygen blocking thin film 33 made of a polymer thin film or the like is formed on the resist 32. The oxygen blocking thin film 33 is formed immediately after the application of the resist 32. Next, as shown in FIG. 4C, an exposure process is performed by irradiating the resist 32 with an electron beam 34 through the oxygen blocking thin film 33 to form an exposure region 32a. Next, as shown in FIG. 3D, a resist pattern 35 is formed by performing a developing process. As described above, in the prior art described in the publication, the oxygen blocking thin film 33 is formed on the resist 32.
Is formed, the acid generator in the resist 32 is prevented from deteriorating during the storage time from the application of the resist 32 to the exposure processing, and the storage of the resist 32 applied on the substrate 31 is prevented. We are trying to extend the period.

[0013]

However, according to the prior art described in the above publication, an oxygen-blocking thin film is formed on a resist to merely block contact between the resist and oxygen, thereby preventing deactivation of acid. There is a problem that it is difficult to do. That is, the deactivation of the acid is such that the generated acid reacts with an alkaline substance such as ammonia in the atmosphere and is neutralized and disappears at the resist surface portion or at the resist / substrate interface portion during the withdrawal time. Because it ’s a phenomenon,
It cannot be prevented simply by blocking oxygen.

The present invention has been made in view of the above circumstances, and even if the acid generated at the resist surface portion or at the resist / substrate interface during the leaving time is neutralized, the acid is substantially removed. It is an object of the present invention to provide a method for forming a resist pattern using a chemically amplified resist that can prevent deactivation.

[0015]

According to a first aspect of the present invention, a chemically amplified photoresist applied on a chemically amplified substrate coated on a substrate is developed after exposure treatment. According to a method of forming a photoresist pattern to be patterned, a photoresist coating step of coating the photoresist on the substrate to form a photoresist film; A solvent supply step of supplying a solvent to the photoresist film formed on the substrate so that the photoresist surface area is larger than at the substrate interface, and an exposure step of exposing the photoresist film. Is characterized by including

The invention according to a second aspect of the present invention relates to a method of forming a photoresist pattern in which a chemically amplified photoresist applied on a substrate is exposed to light, developed and patterned. In the resist film,
A solvent supply step of previously supplying a solvent onto the substrate so that the solvent concentration distribution is greater at the photoresist / substrate interface than at the photoresist surface, and so as to cover the solvent on the substrate. A photoresist application step of applying the photoresist to the photoresist film to form a photoresist film, and an exposure step of exposing the photoresist film to light.

According to a third aspect of the present invention, there is provided a method of forming a photoresist pattern according to the first or second aspect.
The method is characterized by including a post-bake step of performing a heat treatment on the photoresist film after the exposure step.

According to a fourth aspect of the present invention, there is provided a method of forming a photoresist pattern according to the first or third aspect,
The supply of the solvent into the photoresist film in the solvent supply step is performed by injecting the solvent toward the surface of the photoresist film applied on the substrate.

The invention according to claim 5 relates to a method for forming a photoresist pattern according to claim 1 or 3,
The supply of the solvent into the photoresist film in the solvent supply step is performed by exposing the substrate coated with the photoresist film to an atmosphere of a gaseous solvent.

According to a sixth aspect of the present invention, there is provided a method of forming a photoresist pattern according to any one of the first to fifth aspects, wherein the chemically amplified photoresist is a starting species for chemical amplification. It is characterized by comprising a photoacid generator for generating hydrogen ions.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. The description will be specifically made using an embodiment. First Embodiment FIG. 1 shows a method for forming a resist pattern according to a first embodiment of the present invention, and FIGS. 1A to 1F are process diagrams showing the same method in the order of steps. Hereinafter, the same forming method will be described in the order of steps. First, as shown in FIG. 1A, a chemical composition comprising a cresol novolak resin as a base resin, a cross-linking agent and an acid generator added thereto by a spin coating method on a substrate 1 made of a semiconductor substrate or the like. Spinner coated with a negative resist of amplification type, the film thickness is about 0.7μ
An m-th resist film 2 is formed. Next, as shown in FIG. 2B, with the substrate 1 after the formation of the resist film 2 set on, for example, a hot plate, the temperature of the resist film 2 is about 95 ° C. and the time is about 120 seconds. Pre-bake.

Next, as shown in FIG. 1C, approximately 5 ml of a solvent 4 made of, for example, propylene glycol monomethyl ether acetate (PGMEA) is sprayed in a mist form from a nozzle and supplied to the resist film 2. Thereby, the distribution of the solvent concentration in the resist film 2 is made larger at the resist surface portion than at the resist / substrate interface portion. Also, the distribution of the solvent concentration at this time is:
It is predicted in advance that the acid will be deactivated during the withdrawal time from the exposure processing to the post-bake, and the distribution of the acid in the resist film 2 is made uniform at the end of the post-bake.

Next, as shown in FIG. 1D, an exposure process is performed by irradiating the resist film 2 with an electron beam 3 using an electron beam exposure apparatus. The conditions for electron beam exposure are as follows:
kV, current density approximately 10 A / cm ² , exposure amount approximately 24 μ
C / cm ² was performed. As a result, acid is generated in the exposed region 2a of the resist film 2 irradiated with the electron beam 3.

Next, as shown in FIG. 1E, in order to promote a crosslinking reaction in the exposed area 2a of the resist film 2, the temperature is set to about 105 ° C. and the time is set to about 120 seconds.
Post bake of the resist film 2 is performed. During the withdrawal time from the exposure processing to the post-baking, the acid generated by the exposure processing reacts with an alkaline substance such as ammonia in the atmosphere to neutralize the surface of the resist film 2. However, as described above, this phenomenon is predicted in advance, and the distribution of the solvent concentration on the surface portion of the resist film 2 is increased, so that the neutralized acid is supplemented by the solvent having the large concentration distribution. You will be Therefore, deactivation of the acid is prevented. As a result, the distribution of the acid in the resist film 2 becomes uniform at the end of the post-baking. Next, as shown in FIG. 1F, the substrate 1 is immersed in, for example, an alkaline solution to perform a development process, and an unexposed region of the resist is dissolved and removed to form a negative resist pattern 5. . As a result, 0.25 μmL / S (Line and Space)
A pattern was obtained. Therefore, the resist pattern 24 having a shoulder shape as shown in FIG. 5A is prevented.

Thus, according to the configuration of this embodiment,
After applying the chemically amplified negative resist film 2 on the substrate 1, the solvent concentration distribution in the resist film 2 is larger at the resist surface than at the resist / substrate interface. So as to supply the solvent 4,
Since the exposure treatment of the resist film 2 is performed, even if the acid generated by the exposure treatment reacts with the alkaline substance such as ammonia in the atmosphere and is neutralized on the surface portion of the resist film 2 during the leaving time. The neutralized acid is supplemented by a solvent having a large concentration distribution.
Therefore, since the deactivation of the acid can be prevented, the resist pattern 5 with high pattern accuracy can be formed.

Second Embodiment As a method of forming a resist pattern according to a second embodiment of the present invention, an example using a chemically amplified positive resist will be described in the order of steps. First, according to the process of FIG. 1 (a), a chemically amplified type comprising a cresol novolak resin as a base resin and a dissolution inhibitor and an acid generator added thereto by a spin coating method on the substrate 1. A positive resist is spinner-coated to form a resist film 2A having a thickness of about 0.7 μm. Next, a resist film 2 is formed according to the process shown in FIG.
Pre-baking of the resist film 2A is performed at a temperature of about 90 ° C. and for a time of about 120 seconds while the substrate 1 after the formation of A is set on, for example, a hot plate.

Next, as shown in FIG. 2, the resist film 2A
The formed substrate 1 is exposed to a bath 6 filled with PGMEA gasified as a solvent and held for 60 seconds. Thus, the distribution of the solvent concentration in the resist film 2A is made larger at the resist surface portion than at the resist film / substrate interface portion.

Next, according to the process shown in FIG. 1D, an exposure process is performed by irradiating the resist film 2A with an electron beam 3 using an electron beam exposure apparatus. The conditions of electron beam exposure are as follows: acceleration voltage is about 50 kV, current density is about 10 A / cm ² , and exposure amount is about 2
The test was performed at 3 μC / cm ² . Next, the resist film 2A is post-baked under the conditions of a temperature of about 100 ° C. and a time of about 120 seconds according to the process of FIG. Next, in accordance with the step shown in FIG. 3F, the substrate 1 is immersed in, for example, an alkaline solution and then subjected to a development process to dissolve and remove the exposed region of the resist, thereby forming a positive resist pattern. .

As described above, even with the configuration of this example using a positive resist, substantially the same effects as described in the first embodiment using a negative resist can be obtained.

Third Embodiment FIG. 3 shows a method of forming a resist pattern according to a third embodiment of the present invention. FIGS. 3A and 3C are process diagrams showing the same method in the order of steps. . The configuration of the method for forming a resist pattern according to the third embodiment is significantly different from that according to the first embodiment in that the solvent concentration distribution in the resist film is smaller at the resist / substrate interface than at the resist surface. The point is that the solvent is supplied onto the substrate so that is larger. That is, first, as shown in FIG. 1A, for example, BPSG (Boron Phosphoro)
(us Silicate Glass), a substrate 1 on which an interlayer insulating film 7 having a thickness of about 0.5 μm is formed by the CVD method, and about 5 ml of PGMEA is formed on the substrate 1 by a nozzle.
Is sprayed in the form of a mist.

Next, as shown in FIG. 2B, a chemically amplified negative resist film 2 is spin-coated to form a resist film 2 having a thickness of about 0.7 μm. Thus, the distribution of the solvent concentration in the resist film 2 is made larger at the resist / substrate interface than at the resist surface. Also, the distribution of the solvent concentration at this time is:
It is predicted in advance that the acid will be deactivated during the withdrawal time from the exposure processing to the post-bake, and the distribution of the acid in the resist film 2 is made uniform at the end of the post-bake.

Next, as shown in FIG. 2C, the resist film 2 is pre-baked under the conditions of a temperature of about 95 ° C. and a time of about 120 seconds. In the following, after performing the exposure processing under the conditions including the exposure amount of about 25 μC / cm ² according to the step of FIG. 1D, the steps according to the steps of FIGS. Then, a resist pattern 5 is formed on the substrate 1 on which the interlayer insulating film 7 has been formed. As a result, a 0.25 μmL / S pattern was obtained. Therefore, the resist pattern 25 having the shape with the shoulder dropped as shown in FIG. 5B is prevented.

As described above, according to the structure of this example, the distribution of the solvent concentration in the resist film formed in a later step is larger at the interface between the resist and the substrate than at the surface of the resist. After supplying the solvent 4 onto the substrate 1, a chemically amplified negative resist film 2 is applied on the substrate 1 so as to cover the solvent 4, and the resist film 2 is exposed. Therefore, even if the acid generated by the exposure treatment at the resist / substrate interface during the leaving time is neutralized by reacting with an alkaline substance such as ammonia in the atmosphere, the neutralized acid has a concentration equal to that of the acid. Is compensated by a solvent having a large distribution of Therefore, since the deactivation of the acid can be prevented, the resist pattern 5 with high pattern accuracy can be formed.

Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and there may be changes in the design without departing from the gist of the present invention. Is also included in the present invention. For example, the temperature, time, processing conditions, and the like shown in each step are merely examples, and can be changed as needed. The object on which a resist pattern is to be formed is not limited to a semiconductor substrate, but can be applied to an insulating substrate such as a glass substrate, a ceramic substrate, or a plastic substrate.

The base resin is not limited to cresol novolak resin. Further, the base chemical amplification type resist is not limited to a resist using an acid (H ⁺ ) as a catalyst. Also in the third embodiment, the supply of the solvent can be performed by exposing the substrate before the resist film is applied to an atmosphere of a gaseous solvent.

[0036]

As described above, according to the method for forming a resist pattern of the present invention, the distribution of the solvent concentration in the photoresist film is smaller at the photoresist surface than at the photoresist / substrate interface. The exposure time of the resist was increased by supplying the solvent so that the surface area of the photoresist became larger or at the interface between the photoresist and the substrate than at the surface of the photoresist. Acid deactivation at the surface of the resist or at the interface between the resist and the substrate can be prevented. That is, even if the acid generated by the exposure treatment is neutralized by reacting with an alkaline substance such as ammonia in the atmosphere at the surface portion of the resist or at the interface between the resist and the substrate, the neutralized acid is not removed. Since a solvent having a large concentration distribution makes up for it, a resist pattern with high pattern accuracy can be formed.

[Brief description of the drawings]

FIGS. 1A to 1F show a method of forming a resist pattern according to a first embodiment of the present invention, and FIGS.

FIG. 2 is an explanatory view used for describing a method of forming a resist pattern according to a second embodiment of the present invention.

FIGS. 3A to 3C show a method of forming a resist pattern according to a third embodiment of the present invention, and FIGS.

FIGS. 4A to 4D show a conventional method of forming a resist pattern, and FIGS.

FIGS. 5A and 5B show a conventional method for forming a resist pattern, and FIGS.

FIGS. 6A to 6D show a conventional method for forming a resist pattern, and FIGS. 6A to 6D are process diagrams.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Chemical amplification type resist (negative type) 2A Chemical amplification type resist (positive type) 2a Exposure area 3 Electron beam 4 Solvent 5 Resist pattern 6 Tank filled with gaseous solvent 7 Interlayer insulating film

Continued on the front page (51) Int.Cl. ⁶ Identification code FI G03F 7/38 511 G03F 7/38 511

Claims (6)

[Claims] 1. A method of forming a photoresist pattern in which a chemically amplified photoresist applied on a substrate is exposed to light, developed and patterned to form a photoresist pattern, wherein the photoresist is applied to the substrate to form a photoresist film. A photoresist coating step to be formed, wherein the distribution of the solvent concentration in the photoresist film is larger at the photoresist surface portion than at the photoresist / substrate interface portion. A method for forming a photoresist pattern, comprising: a solvent supply step of supplying a solvent to a photoresist film; and an exposure step of exposing the photoresist film to light. 2. A method of forming a photoresist pattern in which a chemically amplified photoresist applied on a substrate is developed and patterned after exposure treatment, wherein a solvent concentration in a photoresist film formed in a subsequent step is reduced. Is larger at the photoresist / substrate interface than at the photoresist surface,
A solvent supply step of previously supplying a solvent onto the substrate; a photoresist coating step of coating the photoresist on the substrate so as to cover the solvent to form a photoresist film; and exposing the photoresist film to light. A method of forming a photoresist pattern, comprising: 3. The method for forming a photoresist pattern according to claim 1, further comprising a post-bake step of performing a heat treatment on the photoresist film after the exposing step. 4. The method according to claim 1, wherein the supply of the solvent into the photoresist film in the solvent supply step is performed by injecting the solvent toward the surface of the photoresist film applied on the substrate. The method for forming a photoresist pattern according to claim 1. 5. The method according to claim 1, wherein the supply of the solvent into the photoresist film in the solvent supply step is performed by exposing the substrate coated with the photoresist film to an atmosphere of a gaseous solvent. Or the method of forming a photoresist pattern according to 3. 6. The chemical amplification type photoresist according to claim 1, further comprising a photoacid generator for generating hydrogen ions serving as chemical amplification starting species. Method of forming a photoresist pattern.