JPH0635206A - Formation of pattern - Google Patents

Abstract

PURPOSE:To lessen the influence of a ground surface substrate in the process for forming fine patterns by a chemical amplification type resist and to stably form the patterns of a high resolution. CONSTITUTION:A protective film 12 contg. carbon as one component is formed on a substrate 11 and a resist film 13 consisting of the chemical amplification type resist of a positive type or a negative type is formed on this protective film 12. The prescribed regions 14 of the resist film 13 are then selectively exposed and are further, the resist film is baked at a prescribed temp. The resist film 13 after the baking is subjected to development processing to selectively remove the exposed regions 14 or to allow these regions to remain, by which the resist patterns 16 of a positive type or the resist patterns 17 of a negative type are formed.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In the manufacturing process of various electronic components such as semiconductor integrated circuits such as LSI, fine processing technology including lithography is adopted. This technique is specifically implemented as the following processes. That is,
First, a resist film is formed on a substrate having various metal oxide films or metal films formed on the surface of a silicon single crystal wafer or the like. Next, after selectively exposing a predetermined area of the resist film, baking, development processing, and rinsing processing are performed to selectively remove or leave the exposed area of the resist film to form a desired resist pattern. Form. Subsequently, by using this resist pattern as an etching resistant mask, the surface of the substrate (metal oxide film, metal film, etc.) is etched to obtain lines, spaces,
And a contact hole and the like are formed.

In recent years, in order to achieve high-density integration accompanying the higher density of electronic components, the above-mentioned technique requires ultra-fine resist patterns. In response to such a demand, a chemically amplified resist using an acid as a catalyst has been proposed as a material capable of obtaining an excellent resist contrast. As this chemically amplified resist, specifically, a compound that generates an acid upon exposure (hereinafter referred to as a photoacid generator)
And a photosensitive composition containing a compound having a hydrophobic group capable of decomposing by an acid and generating a hydrophilic group after decomposition, and a compound generating an acid upon exposure, a polymer, and a crosslinking agent A photosensitive composition may be mentioned. Of these, the former is a positive resist in which the second component forms a hydrophilic group in the exposed area due to the action of the generated acid, and the exposed area is solubilized in the developing solution. On the other hand, the latter is a negative resist in which the exposed region becomes insoluble in the developing solution because the crosslinking agent crosslinks the polymer and increases its molecular weight in the exposed region by the action of the generated acid. In these resists, the photo-acid generator functions as a catalyst, so that it acts on a small amount of other components and can contribute to the formation of a fine pattern.

However, when a chemically amplified resist is used to form a pattern according to the above-described conventional process, the amount of acid generated by the photo-acid generator in the exposed area of the resist film is very small, so that the surrounding environment, especially the base, is reduced. It is easily affected by the substrate, and a fine pattern cannot be stably formed. That is, impurities that are unavoidably present on the substrate before forming the resist film diffuse in the resist film, or adsorb the acid generated from the photo-acid generator at the interface with the substrate to deactivate the acid. As a result, the change in the solubility of the resist film is excluded, and the shape of the formed pattern is impaired.

FIG. 2 shows a specific example of the cross-sectional shape of a pattern formed using a chemically amplified resist according to the conventional process. In the figure, the cross section of the resist pattern 22 formed on the substrate 21 has a hem, and lines and spaces having a desired width are not resolved. It is estimated that this is due to the following reasons.

Generally, in a positive type chemically amplified resist, a hydrophilic group is generated in the exposed area in the presence of a strong acid. However, in the exposed area, basic impurities such as amines inevitably present on the substrate deactivate the acid,
Generation of hydrophilic groups is suppressed, resulting in insufficient solubility in a developing solution. Therefore, the exposed region of the resist remains in the vicinity of the interface with the substrate, particularly in the vicinity of the interface, without being dissolved to some extent during the development process, so that a hem is formed in the cross section as shown in FIG. Not resolved.

Further, in the negative chemically amplified resist,
In the exposed region, the weak acid promotes the crosslinking reaction of the polymer. However, due to the influence of acidic impurities unavoidably present on the substrate, the crosslinking reaction further progresses particularly near the interface between the resist film and the substrate, and the solubility in the developing solution is excessively suppressed. Therefore, in the exposed region of the resist, the residual amount after development is larger in the vicinity of the interface with the substrate, the bottom is generated in the cross section as shown in FIG. 2, and lines and spaces having a desired width are not resolved.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and the problems are as follows.
It is an object of the present invention to provide a method for forming a fine pattern using a chemically amplified resist, which is capable of stably forming a pattern having a rectangular cross section and a high resolution in which the influence of a base substrate is reduced.

[0009]

The pattern forming method of the present invention comprises the steps of forming a protective film containing carbon as one component on a substrate, and (a) exposing the protective film to an acid. Photosensitive composition containing a compound (photo-acid generator) which is generated, and a compound having a hydrophobic group which can be decomposed by an acid and which produces a hydrophilic group after decomposition, or (b) a compound which generates an acid by exposure. (Photo acid generator), polymer,
And a step of forming a resin film containing a photosensitive composition containing a crosslinking agent capable of crosslinking the polymer by the action of an acid as a main component, and a step of selectively exposing a predetermined region of the resin film, The method comprises the steps of baking the resin film after exposure at a predetermined temperature, and developing the resin film after baking to selectively remove or leave the exposed region of the resin film.

According to the method of the present invention, since the protective film containing carbon as one component is interposed between the substrate and the resin film (resist film), the basicity unavoidably present on the substrate. Diffusion and influence of impurities and / or acidic impurities on the resin film are reduced. The protective film also prevents the acid generated from the photo-acid generator in the exposed region of the resin film from being adsorbed and diffused to the substrate side. Therefore, in the exposed area of the resin film, the acid generated from the photo-acid generator works efficiently against other components of the photosensitive composition (chemically amplified resist) without deactivation, and the acid against the developer Solubility changes appropriately. Thus, a resist pattern having a rectangular cross section and high resolution can be formed.

Further, in the method of the present invention, by using the protective film containing carbon, the adhesion of the resin film to the substrate (protective film) is improved and peeling of the film in the developing process is prevented. Therefore, it is not necessary to perform the adhesion promoting treatment on the substrate surface, which has been conventionally performed before the resist film formation, and the pattern formation process is simplified. Less than,
An example of the pattern forming method of the present invention will be described in detail with reference to FIGS. First, the protective film 12 containing carbon as one component is formed on the substrate 11 (shown in FIG. 1A).

The protective film containing carbon and the method of forming the protective film are not particularly limited. For example, a carbon film formed by a sputtering method or a CVD method,
Examples thereof include a carbon fine particle-containing film formed by dispersing fine carbon particles in a matrix made of a polymer material and applying the dispersion.

The carbon content in the protective film can be preferably set in the range of about 20% by weight to 100% by weight. If it is less than 20% by weight, it becomes difficult to sufficiently prevent the influence of impurities from the underlying substrate, and the adhesion between the resist film and the protective film containing carbon is deteriorated. Further, in the subsequent pattern forming step, the etching resistance of the protective film may be reduced, and as a result, the etching accuracy of the underlying substrate may be reduced.

The thickness of the protective film is preferably
Approximately 50 to 10,000 angstroms (hereinafter referred to as A)
Can be set to a range of. If the film thickness is less than 50 A, it may be difficult to sufficiently prevent the influence of impurities from the underlying substrate. If it exceeds 10,000 A, it may be difficult to etch the protective film containing carbon with good dimensional accuracy.

On the other hand, as the substrate used in the present invention,
There is no particular limitation as long as it can be used as a semiconductor substrate, a circuit board, or the like. Specific examples include SiO ₂ film and BP
Examples of the substrate include an oxide film such as an SG film, a metal film such as Al, Cu and Mo, a nitride film such as titanium nitride and silicon nitride, and the like.

Next, a solution containing the photosensitive composition (a) or (b) as a main component is applied onto the protective film 12, and preferably prebaked at a predetermined temperature,
A resin film, that is, a resist film 13 is formed (FIG. 1B).
(Shown).

Composition (a) used in this step
Corresponds to a positive chemically amplified resist, and the composition (b) corresponds to a negative chemically amplified resist. As a specific example of the composition (a) which is the positive resist, the hydroxyl group of poly (p-hydroxy-α-methylstyrene) disclosed in US Pat. No. 4,491,628 is tert.
Examples thereof include a polymer blocked with a butoxycarbonylmethyl group, a composition containing an onium salt as a photoacid generator, and a composition containing an alkali-soluble polymer in addition to the above two components. A specific example of the negative resist composition (b) is solid.
State Technology Vol. 32 (9) (198
9) pp. 105-112 (J. Lingnau, R. Dammel,
J. Theis et al.), A composition containing an s-triazine derivative as a photo-acid generator, a melamine derivative as a cross-linking agent, and a novolac resin as a polymer, and XP-89131 (commercial product). Name:
Shipley company). In addition, if necessary, on the resist film, for the purpose of blocking the influence from the outside,
An antireflection film or various protective films can also be formed.

Next, a predetermined region 14 of the resist film 13 is selectively exposed (arrow) (see FIG. 1C). At this time, the photoacid generator generates an acid in the exposed area 14. In the figure, 15 corresponds to an unexposed area.

This exposure step is performed, for example, by using a mercury lamp g.
Line (wavelength 436 nm), i-line (the same 365 nm), Dee
pUV light (near 250 nm), KrF excimer laser light (near 248 nm), ArF excimer laser light (near 19)
3 nm), electron beam, X-ray, ion beam, etc.
It is performed by exposing the resist film 13 through a mask having a desired pattern shape or by directly irradiating the resist film 13 while scanning the beam.

Further, the resist film 13 after exposure is baked at a predetermined temperature to promote the reaction by the acid generated by the exposure to form a latent image in the exposed region 14 of the resist film (not shown). ). That is, when the resist film 13 contains the composition (a) as a main component, the exposed area 1
In 4, the compound having a hydrophobic group that can be decomposed by the acid using the acid as a catalyst produces a hydrophilic group by the decomposition of the hydrophobic group. On the other hand, when the resist film 13 contains the composition (b) as a main component, in the exposed area 14, the acid acts as a catalyst, the crosslinking agent crosslinks the polymer, and the molecular weight increases.
After the baking, the surface of the resist film may be treated with a Si compound to selectively adsorb the Si compound.

In the above exposure and baking steps, the protective film 12 prevents the influence and diffusion of impurities from the substrate 11 to the resist film 13 as described above,
It also functions to prevent the acid generated in the exposed region 14 in the resist film 13 from adsorbing and diffusing on the substrate 11 side.

Subsequently, the resist film 1 after the baking treatment
3 is developed using an organic solvent, a developing solution such as an alkaline aqueous solution, or a reactive gas. In this development process, when the resist film 13 contains the composition (a) as a main component, the exposed region 14 is selectively dissolved and removed in the developing solution or the reactive gas to form the positive resist pattern 16. (FIG. 1D). On the other hand, when the resist film 13 contains the composition (b) as the main component, the unexposed region 15 is selectively dissolved and removed in the developing solution or the reactive gas, and the exposed region 14 remains and the negative type A resist pattern 17 is formed (shown in FIG. 1E). still,
The developer and gas used here can be appropriately selected depending on the type of the photosensitive composition applied, that is, the type of resist material.

Then, the resist pattern 16 or 17 is formed.
The protective film 12 is selectively removed by using the as a mask to form a protective film pattern 18 or 19 (shown in FIG. 1F or 1G). This step can be performed by, for example, a reactive ion etching method (RIE) using a gas containing oxygen.

In the pattern forming method of the present invention as described above, after the protective film containing carbon as one component is formed and before the resist film is formed, various treatments are applied to the surface of the protective film. The function of the protective film as described above can be further enhanced, the cross-sectional shape of the formed pattern can be improved, and the resolution can be further improved.

The surface treatment of the protective film containing carbon includes, for example, introducing fluorine atoms into the surface of the protective film, annealing the protective film at a high temperature (about 300 to 1200 ° C.), and acidifying the protective film. And treatment with a solution and / or a basic solution, exposing the protective film to an acidic atmosphere and / or a basic atmosphere, and forming a second protective film made of an inorganic material on the protective film. . These treatments can be carried out by appropriately setting conditions or by combining two or more kinds.

By using the resist pattern and the protective film pattern formed by the method of the present invention as an etching resistant mask, the underlying substrate is selectively etched, whereby ultrafine processing can be performed.

In such a substrate etching process, only the resist pattern may be removed in advance and the protective film pattern may be used alone as an etching resistant mask.
In this case, since the aspect ratio of each cross section of the protective film pattern serving as a mask is very small, the etching accuracy of the base substrate can be further improved.

[0028]

The present invention will be described in more detail below with reference to examples. These examples are described for the purpose of facilitating the understanding of the present invention, and do not limit the present invention.

Example 1 A carbon film having a film thickness of 1000 A was formed on a silicon nitride film having a film thickness of 6000 A by a sputtering method. Then, on this carbon film, some of the hydroxyl groups of poly (p-vinylphenol) were
A positive chemically amplified resist solution containing a polymer blocked with tert-butoxycarbonylmethyl group and triphenylsulfonium triflate is applied and dried on a hot plate at 90 ° C. for 90 seconds to give a resist with a film thickness of 1 μm. A film was formed. Next, a reduction projection exposure machine using a KrF excimer laser is used to expose the resist film through a mask having a predetermined pattern (exposure amount: 20 mJ / cm ² ) Was done. Then, the resist film after exposure was baked on a hot plate at 90 ° C. for 90 seconds. Then, the resist film was immersed in an aqueous tetramethylammonium hydroxide solution having a concentration of 2.38% by weight.
By immersing it for 0 seconds, developing it, and washing it with water,
A resist pattern was formed. In the above process,
No peeling of the resist film occurred during the development process even if the conventional adhesion promoting process was not performed on the surface of the carbon film before applying the resist solution.

The pattern thus obtained was observed with a scanning electron microscope. As a result, it was found that the line width was 0.25 μm and a highly precise pattern having a rectangular cross section was formed.

Following the above process, a line width of 0.25
When the underlying carbon film was etched by RIE using oxygen gas using the resist pattern of μm as a mask, the carbon film pattern could be formed with excellent dimensional accuracy.

Further, when the underlying silicon nitride film is etched by RIE using a fluorine-based gas such as CF ₄ with the resist pattern and the carbon film pattern as a mask, the film is finely processed with excellent dimensional accuracy. I was able to.

Prior to the etching of the silicon nitride film, the resist pattern was removed, and the etching was performed using only the carbon film pattern as a mask. As a result, the silicon nitride film could be finely processed with higher dimensional accuracy. did it.

Example 2 A resist pattern was formed according to the same method and conditions as in Example 1 except that a 6000 A thick BPSG film was used in place of the silicon nitride film. The obtained pattern was observed with a scanning electron microscope. As a result, it was found that the line width was 0.25 μm and a highly precise pattern having a rectangular cross section was formed.

Example 3 Instead of forming a carbon film on a silicon nitride film by a sputtering method, a polymer solution containing 40% by weight of carbon fine particles having a particle size of 17 nm was applied on the silicon nitride film to form a carbon-containing film. A resist pattern was formed according to the same method and conditions as in Example 1 except that the resist pattern was formed. The obtained pattern was observed with a scanning electron microscope. As a result, it was found that the line width was 0.25 μm and a highly precise pattern having a rectangular cross section was formed.

Example 4 Instead of the positive type resist, a negative type chemically amplified resist XP
According to the same method and conditions as in Example 1 except that -89131 (trade name: manufactured by Shipley) was used.
A resist pattern was formed. The obtained pattern was observed with a scanning electron microscope. As a result, the line width is 0.2
It was 5 μm, and it was found that a highly precise pattern having a rectangular cross section was formed.

Comparative Example A positive type polymer containing triphenylsulfonium triflate and a polymer obtained by blocking a part of hydroxyl groups of poly (p-vinylphenol) with a tert-butoxycarbonylmethyl group on a BPSG film having a film thickness of 6000A. Apply a chemically amplified resist solution and apply 90 on a hot plate.
It was dried at 90 ° C. for 90 seconds to form a resist film having a film thickness of 1 μm. Next, a reduction projection exposure machine using a KrF excimer laser is used to expose the resist film through a mask having a predetermined pattern (exposure amount: 20 mJ / cm ² ) Was done. Then, the resist film after exposure was baked on a hot plate at 90 ° C. for 90 seconds. Next, the resist film is immersed in a tetramethylammonium hydroxide aqueous solution having a concentration of 2.38% by weight for 90 seconds to develop the resist film,
By further washing with water, a resist pattern was formed.

The pattern thus obtained was observed with a scanning electron microscope. As a result, it was found that the line width was 0.6 μm, and a pattern with a skirt was formed at the bottom, that is, near the interface with the substrate, as shown in FIG.

Example 5 A carbon film having a film thickness of 1000 A was formed on a silicon nitride film having a film thickness of 6000 A by a sputtering method. The substrate was then placed in a pre-evacuated reaction vessel. In this container, add CF ₄
Gas and O ₂ gas at 100 cc and 50 per minute, respectively
It is sent at a flow rate of cc, and a frequency of 2.
A 45 GHz microwave was applied to introduce fluorine atoms into the surface of the carbon film.

Subsequently, on this carbon film, a positive type chemical amplification containing a polymer obtained by blocking a part of hydroxyl groups of poly (p-vinylphenol) with a tert-butoxycarbonylmethyl group and triphenylsulfonium triflate. A mold resist solution was applied and dried on a hot plate at 90 ° C. for 90 seconds to form a resist film having a film thickness of 1 μm. Next, a reduction projection exposure machine using a KrF excimer laser is used to expose the resist film through a mask having a predetermined pattern (exposure amount: 20 mJ / cm ² )
I went. Then, the resist film after exposure was baked on a hot plate at 90 ° C. for 90 seconds. Next, the resist film was immersed in an aqueous tetramethylammonium hydroxide solution having a concentration of 2.38% by weight for 90 seconds for development treatment, and further washed with water to form a resist pattern. In the above process, the resist film was not peeled off during the development process even if the conventional adhesion promoting process was not performed on the surface of the carbon film before applying the resist solution.

The pattern thus obtained was observed with a scanning electron microscope. As a result, it was found that the line width was 0.25 μm and a high-precision pattern having a rectangular cross section as shown in FIG. 1D was formed.

Example 6 A carbon film having a film thickness of 400 A was formed on the BPSG film having a film thickness of 10,000 A by a sputtering method. Next, this carbon film was annealed at 400 ° C. for 5 minutes in an argon gas atmosphere.

Then, a resist film is formed, exposure, baking, and development are performed in accordance with the same method and conditions as in Example 5 except that a specific exposure mask is used to form a resist pattern. (Hole pattern) was formed. The obtained pattern was observed with a scanning electron microscope. As a result, it was found that the hole diameter was 0.3 μm and a high-precision pattern having a rectangular cross section as shown in FIG. 1D was formed.

In this embodiment, the carbon film was formed by sputtering and then annealed. However, by heating the substrate at a high temperature while forming the carbon film by sputtering,
It can also be annealed.

Example 7 A carbon film having a film thickness of 400 A was formed on the BPSG film having a film thickness of 10,000 A by a sputtering method. Next, this carbon film was treated in a hydrochloric acid aqueous solution having a concentration of 5% by weight for 10 minutes and then washed with pure water. Further, after treated with an aqueous solution of tetramethylammonium hydroxide having a concentration of 2.38% by weight for 5 minutes, it was washed again with pure water.

Subsequently, a resist film is formed, exposure, baking, and development are performed according to the same method and conditions as in Example 5 except that a specific exposure mask is used, and a resist pattern is formed. (Hole pattern) was formed. The obtained pattern was observed with a scanning electron microscope. As a result, it was found that the hole diameter was 0.3 μm and a high-precision pattern having a rectangular cross section as shown in FIG. 1D was formed.

Although the treatment with the acidic solution and the treatment with the basic solution are used in combination in this embodiment, practically, only one of these treatments has sufficient effect.

Example 8 On a WSi film having a film thickness of 2000 A, a film thickness of 8 was formed by a CVD method.
A carbon film of 00A was formed. Then, this carbon film is replaced with 5
After being exposed to a chlorine-based gas atmosphere at 0 ° C. for 3 minutes, it was washed with pure water for 5 minutes.

Subsequently, a resist film is formed, exposure, baking, and development are performed according to the same method and conditions as in Example 5 except that a specific exposure mask is used, and a resist pattern is formed. (Hole pattern) was formed. The obtained pattern was observed with a scanning electron microscope. As a result, it was found that the hole diameter was 0.3 μm and a high-precision pattern having a rectangular cross section as shown in FIG. 1D was formed.

Example 9 An Al film having a film thickness of 4000 A and a film thickness of 4 were formed by a sputtering method.
A carbon film of 00A was formed. Further, 50 A of amorphous silicon was deposited on this carbon film by a sputtering method.

Subsequently, a resist film is formed, exposure, baking, and development are performed in accordance with the same method and conditions as in Example 5 except that a specific mask for exposure is used. (Hole pattern) was formed. The obtained pattern was observed with a scanning electron microscope. As a result, it was found that the hole diameter was 0.3 μm and a high-precision pattern having a rectangular cross section as shown in FIG. 1D was formed.

After depositing amorphous silicon on the carbon film, annealing at a higher temperature can reduce the influence of reflected light from the underlying Al film on the resist film in the subsequent resist pattern forming step. It was possible. From this, it is suggested that the method of the present invention can form a highly accurate pattern by performing the surface treatment of the carbon film even when the resist pattern is formed on the high reflectance substrate such as the Al film. .

[0053]

As described in detail above, according to the present invention,
In the pattern formation using the chemically amplified resist, the influence of the underlying substrate can be reduced, and a pattern having a rectangular cross section and high resolution can be stably formed.
Furthermore, using such a high-resolution pattern as a mask,
By etching the base substrate, ultrafine processing with extremely excellent dimensional accuracy is realized.

[Brief description of drawings]

1A to 1G are sectional views showing an example of a pattern forming method according to the present invention in the order of steps.

FIG. 2 is a sectional view showing the shape of a pattern formed by a conventional method.

[Explanation of symbols]

11, 21 ... Substrate, 12 ... Protective film, 13 ... Resist film,
14 ... Exposed area, 15 ... Unexposed area, 16, 17, 22
... resist pattern, 18,19 ... protective film pattern

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location G03F 7/11 503 H01L 21/027 (72) Inventor Takahiro Ikeda Toshiba Komukai Toshiba, Kawasaki City, Kanagawa Prefecture Town No. 1 Toshiba Corporation Research Institute

Claims (1)

[Claims] 1. A step of forming a protective film containing carbon as one component on a substrate, and (a) a compound capable of generating an acid upon exposure and a hydrophobic group decomposable by the acid, on the protective film. A photosensitive composition containing a compound that produces a hydrophilic group after decomposition, or (b) a photosensitive composition containing a compound that generates an acid upon exposure, a polymer, and a crosslinking agent that can crosslink the polymer by the action of the acid. Composition, a step of forming a resin film containing as a main component, a step of selectively exposing a predetermined region of the resin film, a step of baking the exposed resin film at a predetermined temperature, And a step of developing the resin film after baking to selectively remove or leave the exposed region of the resin film.