JPH10333341A - Forming method of resist pattern and production of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a pattern of a size smaller than the resolution limit of an aligner by expanding the resist pattern after the pattern is formed in a photoresist. SOLUTION: A resist film 26 is exposed and developed to form a resist pattern 28, and then the whole surface of the resist pattern 28 is exposed. Then the semiconductor substrate 10 is introduced into a vacuum chamber, which is evacuated. Then as the semiconductor substrate 10 is held at 150 to 180 deg.C, an acetyl chloride gas is introduced into the chamber to carry out the reaction of the resist pattern 28 and the acetyl chloride gas. On the resist pattern 28, the chemical reaction proceeds to increase the volume, which reduces the size of the punched pattern to form a contact hole. Then the expanded resist pattern is used as a mask to etch the interlayer insulating film 24 so as to form a contact hole which exposes source-drain diffusing layers 20, 22. Thus, the aperture diameter of the contact hole can be reduced smaller than the resolution limit of an aligner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a resist pattern, and more particularly, to a method for forming a resist pattern for forming a pattern below the resolution limit of an exposure apparatus and a method for manufacturing a semiconductor device.

[0002]

2. Description of the Related Art With the expansion of functions required for semiconductor devices, demands for the degree of integration are increasing.
For this reason, fine processing technology for realizing a semiconductor integrated circuit having a finer pattern has been sought. Conventionally, miniaturization of semiconductor devices has been achieved with the progress of lithography technology. In order to improve the resolution in lithography, it is necessary to increase the numerical aperture NA of the projection lens or shorten the wavelength of light. The resolution can be improved by any of these,
Since the decrease in the depth of focus due to the increase in the numerical aperture NA is more remarkable than when the exposure wavelength is shortened, the numerical aperture N is required to perform highly accurate exposure on a substrate having a step.
It is not desirable to increase A unnecessarily. Therefore, conventionally, miniaturization of a semiconductor device has been realized mainly by shortening an exposure wavelength.

Against this background, lithography has progressed in tandem with the development of resist materials, and the light source of an exposure apparatus has been changed from g-line to i-line of mercury, and further to laser light such as a KrF excimer laser. Wavelength shift is progressing.

[0004]

However, in the case of a KrF excimer laser having a wavelength of 248 nm, for example, even if a pattern is formed using a chemically amplified high-sensitivity resist, the hole pattern is currently formed at a resolution of about 0.24 μm. It is considered to be the limit, and there is a concern that the life as a mass production technology will not be long even if an excimer laser process requiring a huge investment is introduced.

For this reason, if a technique for forming a resist pattern below the resolution limit of the exposure apparatus is established, the application generation of the exposure apparatus can be expanded, and the equipment investment can be reduced, but it is still effective. No means have been found yet. It is an object of the present invention to provide a resist pattern forming method for forming a resist pattern having a resolution equal to or less than the resolution limit of an exposure apparatus in an optical lithography technique using a chemically amplified resist.

Another object of the present invention is to provide a method of manufacturing a semiconductor device having a pattern that is equal to or less than the resolution limit of an exposure apparatus.

[0007]

The object of the present invention is to expose a photoresist film having an acid generator that generates an acid upon irradiation with light and a unit structure in which a protective group is dissociated by the acid,
An exposure step of generating the acid in the photoresist film, dissociating the protective group with the acid, the unit structure in which the protective group is dissociated, and a substance that reacts with the unit structure in which the protective group is dissociated. A reaction step of increasing the volume of the photoresist film by reacting with a fluid containing the resist film.

Another object of the present invention is to form a photoresist film by applying an acid generator that generates an acid upon irradiation with light and a photoresist having a unit structure in which a protective group is dissociated by the acid onto a workpiece. Forming a photoresist film, exposing and developing the photoresist film to pattern the photoresist film into a predetermined pattern, exposing the patterned photoresist film to light, An exposure step of generating the acid in the film, dissociating the protecting group by the acid, the unit structure in which the protecting group is dissociated, and a fluid containing a substance that reacts with the unit structure in which the protecting group is dissociated. Reacting to change the dimensions of the patterned photoresist film. Also achieved by preparative pattern forming method. By forming the resist pattern in this manner, the resist pattern after patterning can be expanded. Accordingly, when forming a punched pattern such as a contact hole, a resist pattern having an opening having a size smaller than that obtained by normal patterning can be formed. This makes it possible to form a resist pattern that is not more than the resolution limit of the exposure apparatus.

In the above-mentioned method for forming a resist pattern, the unit structure has a phenolic hydroxyl group,
It is preferable that the photoresist film increases in volume due to the reaction between the phenolic hydroxyl group and the fluid. In the above-described method for forming a resist pattern, the substance that reacts with the unit structure in which the protective group has been dissociated is a carboxylic acid represented by R—CO—X (where R is an organic group and X is a halogen element). Desirably, it is a halide.

[0010] In the resist pattern formation method, the substance which reacts with the unit structure where the protecting group is dissociated, R-SO _N -X (where, R represents an organic group, X is a halogen element, N is the It is preferably a substance represented by (an integer of 0 to 2). Further, the object is to form a resist pattern forming step of forming a photoresist film having a predetermined pattern on the object to be processed by the above-mentioned resist pattern forming method, and the object to be processed using the photoresist film as a mask. And a patterning step of processing the semiconductor device into the predetermined pattern. By manufacturing the semiconductor device in this manner, the object to be processed can be processed into a pattern that is equal to or less than the resolution limit of the exposure apparatus.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the principle of the present invention will be described. A chemically amplified resist has a unit structure that generates an acid upon irradiation with light, and a unit structure where a protecting group is dissociated by an acid catalyst, and generates an acid by a photoreaction, and dissociates the protecting group with the acid. Refers to the photoresist used. For example, a photoresist having polyhydroxystyrene having a t-butoxycarbonyl group as a protecting group and an acid generator is also one of the chemically amplified resists.

For example, in the case of a chemically amplified resist having a polyhydroxystyrene having a t-butoxycarbonyl group as a protecting group and an acid generator, the proton acid (H ⁺ ) generated by light irradiation has

[0013]

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The reaction takes place to produce a soluble phenolic hydroxyl group from which the protecting group has been dissociated. When this photoresist is developed using a predetermined developing solution, the phenolic hydroxyl group from which the protecting group has been dissociated dissolves in the developing solution. On the other hand, since the protective group is not dissociated in the region where the light irradiation has not been performed, it is not dissolved by the developer. Therefore, by irradiating the photoresist with light in a predetermined pattern, the photoresist functions as a positive photoresist.

The inventor of the present invention has conducted intensive studies on such a chemically amplified resist. As a result, instead of developing the exposed photoresist with a developing solution, the exposed photoresist is exposed to a predetermined reactive gas atmosphere, thereby protecting the photoresist. It has been newly found that a chemical reaction occurs between a phenolic hydroxyl group from which is dissociated and a reactive gas to cause a chemical reaction, resulting in an increase in the volume of a chemically amplified resist.

For example, when the above-mentioned chemically amplified resist having polyhydroxystyrene having a t-butoxycarbonyl group as a protecting group and an acid generator is used, exposure to acetyl chloride gas (CH ₃ COCl) after light irradiation. Between the phenolic hydroxyl group, whose protective group has been dissociated by light irradiation, and acetyl chloride gas.

[0017]

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The following chemical reaction occurs and the volume of the photoresist increases. Such a chemical reaction accompanied by an increase in volume is also observed in other chemically amplified resists. For example,

[0019]

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[0020] and (where the organic group such as R ₁ is _{CH 3, C 2 H 5,} C 3 H 7, R 2 is CH _3, C ₂ H _5, an organic group such as C ₃ H _7, Ph) Table Reaction type,

[0021]

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(Where R is H, CH ₃ , C ₂ H ₅ , C
_A similar chemical reaction occurred in a chemically amplified resist having a reaction mode represented by an organic group such as ₃ H ₇ and Ph). The reactive gas is reacted with the phenolic hydroxyl group dissociated protecting group, for example, applying a carboxylic acid halide represented by the general formula R-CO-X, the formula R-SO _N -X compound Can be.

Here, R is CH ₃ , C ₂ H ₅ , C ₃ H ₇ , C ₄
An alkyl group or an aryl group such as H ₉ or a derivative thereof, X is a halogen such as Cl or Br, and N is 0 to
It is an integer of 2. For example, when a phenolic hydroxyl group in which a protecting group is dissociated reacts with a carboxylic acid halide represented by the general formula R-CO-Cl,

[0024]

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The chemical reaction shown by the above occurs, and the volume of the photoresist increases. On the other hand, when a compound protecting group represented by dissociated phenolic hydroxyl group and the general formula R-SO _N -Cl are reacted

[0026]

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The chemical reaction represented by the formula (1) occurs, and the volume of the photoresist increases. As a unit structure (acid generator) that generates an acid by light irradiation, for example, an oxaazole derivative, an s-triazine derivative, an iodonium salt, a sulfonium salt, a disulfone derivative, an imidosulfonate derivative, or a diazonium salt can be used. is there. However, it is not limited to these.

Next, a method for forming a resist pattern and a method for manufacturing a semiconductor device according to one embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a process chart showing a method for forming a resist pattern according to the present embodiment, FIGS. 2 and 3 are process sectional views showing a method for manufacturing a semiconductor device according to the present embodiment,
FIG. 4 is a graph showing a change in the diameter of the contact hole due to expansion of the resist pattern, and FIG. 5 is a process chart showing a method for forming a resist pattern according to a modification of the present embodiment.

The resist pattern forming method according to the present embodiment utilizes the above-described volume expansion of the photoresist, increases the volume of the resist pattern after forming the resist pattern, and patterns the underlying substrate using the expanded resist pattern as a mask. And forming a hole pattern smaller than the resolution limit of the exposure apparatus.

That is, the resist pattern forming method according to the present embodiment forms a resist pattern in the same manner as a normal resist pattern forming method using a chemically amplified resist (steps S11 to S16), and then exposes the entire surface of the wafer. Then, an acid for dissociating the protecting group is generated (step S17), the protecting group is dissociated by the acid thus generated, and the phenolic hydroxyl group from which the protecting group has been dissociated reacts with a predetermined reaction gas. The resist pattern is expanded (step S18).

Hereinafter, each step will be described in detail. First, a chemically amplified resist is applied on a processing target such as a semiconductor wafer by a spin coating method or the like (step S11). Next, a pre-bake for removing the solvent in the chemically amplified resist is performed (step S1).
2).

Subsequently, the photoresist is exposed through a mask having a predetermined pattern such as a reticle (step S13). As a result, an exposed region and an unexposed region are generated on the photoresist, and in the exposed region, protonic acid (H ⁺ ) is generated from the acid generator by a photoreaction. Thereafter, a predetermined heat treatment is performed to dissociate the protecting group for the phenolic hydroxyl group with the acid generated by the photoreaction (step S14). This reaction occurs only in the region where the protonic acid is present, ie, the exposed region.

Next, the photoresist is developed with a predetermined developing solution (step S15). Since the phenolic hydroxyl group from which the protecting group has been dissociated becomes alkali-soluble, the photoresist in the exposed region is removed by developing with an aqueous alkali solution. Subsequently, post-baking is performed to remove the developing solution and fix the photoresist (step S16).

The above steps S11 to S1
No. 6 is no different from a normal resist pattern forming method using a chemically amplified resist. In steps S14 to S16, the properties of the photoresist in the unexposed areas do not chemically change. Thereafter, the resist pattern patterned on the object to be processed is entirely exposed (step S17). At this time, in the region not exposed in step S13, that is, in the remaining resist pattern, protonic acid is generated from the acid generator by a photoreaction.

Next, the resist pattern formed on the object is exposed to a predetermined reactive gas atmosphere at a predetermined temperature (step S18). The predetermined temperature is used to react the acid generated by the photoreaction with the photoresist resin to dissociate the protective group, and to expose to the reactive gas, the phenolic hydroxyl group from which the protective group has been dissociated. This is for increasing the volume of the photoresist by reacting with the reactive gas. When the volume of the photoresist increases in this manner, in a punched pattern such as a hole pattern, the pattern is narrowed by the expansion of the photoresist, and as a result, a resist pattern smaller than the resolution limit of the exposure apparatus is formed.

Thereafter, by patterning the object using the resist pattern as a mask, the object can be processed below the resolution limit of the exposure apparatus. Next, an example in which the method for forming a resist pattern according to the present embodiment is applied to a method for manufacturing a semiconductor device will be described.

First, the main surface of the semiconductor substrate 10 is locally oxidized to form an element isolation film 12. Next, the gate insulating film 1 is formed in the device region defined by the device isolation film 12.
4. The gate electrode 16 is formed. Subsequently, the gate electrode 1
6 is used as a mask to perform ion implantation, and LDD (LightlyD
oped drain) to form a low concentration region.

Thereafter, a side wall 18 is formed on the side wall of the gate electrode 16. Next, ion implantation is performed using the side wall 18 and the gate electrode 16 as a mask,
A high-concentration region having a DD structure is formed. Thus, the source / drain diffusion layers 20 and 22 having the LDD structure are formed. Subsequently, on the MOS transistor thus formed,
An interlayer insulating film 24 covering the MOS transistor is formed.

Next, the resist film 26 applied on the interlayer insulating film 24 is exposed to a predetermined pattern in the same manner as the resist pattern forming method shown in steps S11 to S14 in FIG. 2 (a)). For example, using the above-described chemically amplified resist having polyhydroxystyrene having a t-butoxycarbonyl group as a protecting group and an acid generator, the source / drain diffusion layer 20 is exposed by an exposure apparatus using a KrF excimer laser as a light source.
The pattern of the contact hole opened on the substrate 22 is exposed.

Subsequently, in the same manner as the resist pattern forming method shown in steps S15 to S17 in FIG. 1, the exposed resist film 26 is developed to form a resist pattern 28, and thereafter, the resist pattern 28 is entirely exposed ( FIG. 2 (b). Thereafter, the semiconductor substrate 10 on which the resist pattern 28 is formed is introduced into a vacuum chamber (not shown), and the pressure is reduced to about 1 Torr.

Next, the semiconductor substrate 10 is placed at 150 to 180
While maintaining the temperature at 50 ° C.,
An acetyl chloride gas of about Torr is introduced to cause the resist pattern 28 to react with the acetyl chloride gas. As a result, the reaction represented by the chemical formula 1 occurs in the resist pattern 28, the volume increases, and the size of the punched pattern for forming the contact hole decreases (FIG. 2C).

Subsequently, the interlayer insulating film 24 is etched by using the resist pattern 30 expanded as described above as a mask to form contact holes 32 and 34 exposing the source / drain diffusion layers 20 and 22 (FIG. 3A). ). Thereafter, a predetermined wiring layer 36 is deposited on the entire surface (FIG. 3).
(B)). The wiring layer 36 has contact holes 32 and 34
Are connected to the source / drain diffusion layers 20 and 22 via the gate.

Next, the wiring layer 36 is processed into a desired pattern (FIG. 3C). By manufacturing the semiconductor device in this manner, the opening diameter of the contact holes 32 and 34 can be reduced to the resolution limit of the exposure device or less, which is extremely effective in achieving high integration of the semiconductor device. . FIG. 4 is a graph showing a change in the diameter of the contact hole accompanying expansion of the resist pattern. In the figure, the symbol ◆
When a contact hole is formed by the usual method of manufacturing a semiconductor device in which a resist pattern is formed only by steps S11 to S16 of FIG.
The case where the contact hole is formed by the method for manufacturing the semiconductor device according to the present embodiment in which the resist pattern is expanded by 1 to S18 is shown.

As shown in the figure, the sample (◆) without the treatment with acetyl chloride gas has a contact hole diameter of about 360 nm, while the sample (■) without the treatment with acetyl chloride gas has a contact hole diameter of about 360 nm. Was about 280 nm, and the size could be reduced by about 80 nm. Therefore, even in the case of a KrF excimer laser exposure apparatus which is currently expected to have a resolution limit of about 0.24 μm, about 0.2 μm is expected in view of the same reduction.
It is thought that a contact hole of about 16 μm can be opened, and it can be used as a mass production technology one generation ahead.

As is clear from FIG. 4, the sample (■) treated with the acetyl chloride gas has a smaller variation in the contact hole diameter than the sample (◆) not treated with the acetyl chloride gas. Has become. It is considered that this is because the resist pattern 28 is leveled by the heat treatment during the treatment with the acetyl chloride gas, and the variation is reduced. Therefore, performing the above-described process of expanding the resist pattern is effective not only in reducing the pattern size but also in reducing variations in the size.

As described above, according to this embodiment, in the photolithography technique using the chemically amplified resist,
Since the resist pattern is expanded after patterning the photoresist, it is possible to form a resist pattern that forms a resist pattern below the resolution limit of the exposure apparatus. Further, by patterning the underlying substrate as a processing target using the resist pattern formed as described above as a mask, a semiconductor device having a pattern below the resolution limit of the exposure apparatus can be manufactured.

The present invention is not limited to the above embodiment, and various modifications are possible. For example, in the method for forming a resist pattern shown in FIG. 1, the post-baking step (step S16) is performed after the developing step (step S15).
It may be performed after 18). That is, as shown in FIG. 5, a resist coating step (step S21), a pre-bake step (step S22), and an exposure step (step S2)
3), a post-exposure baking step (step S24), a development step (step S25), and a whole-surface exposure step (step S2)
6), a reaction step (Step S27), and a post-bake step (Step S28). Also in this case, the processing can be performed under the same conditions as the resist pattern forming method shown in FIG.

Further, in the above-described embodiment, a method of manufacturing a semiconductor device in which the above-described method of forming a resist pattern is applied to the opening of a contact hole has been described. However, the present invention is not limited to the step of opening a contact hole, but is applicable to various manufacturing steps. Can be. In consideration of the reduction in device size, it is particularly effective to apply the present invention to the formation of a punched pattern such as a contact hole. However, the present invention is not limited to the punched pattern and may be applied to the formation of a remaining pattern.

[0049]

As described above, according to the present invention, a photoresist film having an acid generator that generates an acid upon irradiation with light and a unit structure in which a protective group is dissociated by the acid is exposed to light. An exposure step of generating an acid in the photoresist film by reacting a unit structure in which the protecting group is dissociated with the acid and a fluid containing a substance that reacts with the unit structure in which the protecting group is dissociated. Since the resist pattern is formed by the reaction step of increasing the volume of the resist, a resist pattern having a resolution equal to or less than the resolution limit of the exposure apparatus can be formed.

Further, an acid generator that generates an acid upon irradiation with light and a photoresist having a unit structure in which a protective group is dissociated by the acid are applied on a workpiece to form a photoresist film. A patterning step of processing the photoresist film into a predetermined pattern by exposing and developing the photoresist film; and an exposing step of exposing the patterned photoresist film to generate an acid in the photoresist film. And dissociating the protecting group by an acid, and reacting a unit structure in which the protecting group is dissociated with a fluid containing a substance that reacts with the unit structure in which the protecting group is dissociated, thereby changing the dimensions of the patterned photoresist film. Expanding the resist pattern after patterning by forming a resist pattern in the reaction step It can be. Accordingly, when forming a punched pattern such as a contact hole, a resist pattern having an opening having a size smaller than that obtained by normal patterning can be formed. This makes it possible to form a resist pattern that is not more than the resolution limit of the exposure apparatus.

In the above-described method for forming a resist pattern, a photoresist having a phenolic hydroxyl group in its unit structure is used, and the volume of the photoresist pattern can be increased by reacting the phenolic hydroxyl group with a fluid. In the above resist pattern forming method, the carboxylic acid halide represented by R—CO—X (where R is an organic group and X is a halogen element) is used as the substance that reacts with the unit structure in which the protective group has been dissociated. Can be applied.

[0052] In the above resist pattern forming method, a substance protecting group reacts with dissociated unit structure, R-SO _N -X (where, R represents an organic group, X is a halogen element, N is the 0 (An integer of 2) can be applied. Further, by the above-described resist pattern forming method, a resist pattern forming step of forming a photoresist film having a predetermined pattern on the workpiece,
The patterning step of processing the object to be processed into a predetermined pattern using the photoresist film as a mask makes it possible to process the object to be processed into a pattern equal to or less than the resolution limit of the exposure apparatus. it can.

[Brief description of the drawings]

FIG. 1 is a process chart showing a resist pattern forming method according to an embodiment of the present invention.

FIG. 2 is a process cross-sectional view (part 1) illustrating the method for manufacturing a semiconductor device according to one embodiment of the present invention;

FIG. 3 is a process sectional view (part 2) illustrating the method for manufacturing the semiconductor device according to the embodiment of the present invention;

FIG. 4 is a graph showing a change in a contact hole diameter due to expansion of a resist pattern.

FIG. 5 is a process chart showing a resist pattern forming method according to a modification of one embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 semiconductor substrate 12 element isolation film 14 gate insulating film 16 gate electrode 18 sidewall 20 source / drain diffusion layer 22 source / drain diffusion layer 24 interlayer insulating film 26 resist film 28 resist pattern 30 ... expanded resist pattern 32 ... contact hole 34 ... contact hole 36 ... wiring layer

Claims (6)

[Claims] An acid generator that generates an acid upon irradiation with light,
Exposing a photoresist film having a unit structure in which a protective group is dissociated by the acid to generate an acid in the photoresist film; and dissociating the protective group by the acid, thereby dissociating the protective group. A reaction step of increasing the volume of the photoresist film by reacting the unit structure with a fluid containing a substance that reacts with the unit structure in which the protecting group has been dissociated. Forming method. 2. An acid generator that generates an acid upon irradiation with light,
A photoresist having a unit structure in which a protective group is dissociated by the acid is applied on a workpiece, a photoresist film forming step of forming a photoresist film, and the photoresist film is exposed and developed,
A patterning step of processing the photoresist film into a predetermined pattern; an exposure step of exposing the patterned photoresist film to generate the acid in the photoresist film; and dissociating the protecting group with the acid. A reaction step of changing the dimensions of the patterned photoresist film by reacting the unit structure in which the protecting group is dissociated with a fluid containing a substance that reacts with the unit structure in which the protecting group is dissociated. A method for forming a resist pattern, comprising: 3. The resist pattern forming method according to claim 1, wherein the unit structure has a phenolic hydroxyl group, and the photoresist film has a volume by reacting the phenolic hydroxyl group with the fluid. The method of forming a resist pattern, wherein the number of resist patterns increases. 4. The method of forming a resist pattern according to claim 1, wherein the substance that reacts with the unit structure from which the protective group has been dissociated is R-CO-X (where R is A method of forming a resist pattern, comprising a carboxylic acid halide represented by an organic group and X is a halogen element). 5. A resist pattern forming method according to any one of claims 1 to 3, wherein the substance which reacts with the unit structure where the protecting group is dissociated, R-SO _N -X (Here, R Is an organic group, X is a halogen element, and N is an integer of 0 to 2). 6. A method for forming a resist pattern according to claim 1 on an object to be processed.
A resist pattern forming step of forming a photoresist film having a predetermined pattern; and a patterning step of processing the object to be processed into the predetermined pattern using the photoresist film as a mask. Production method.