JP3128335B2 - Pattern formation method - Google Patents

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 a semiconductor device.

[0002]

2. Description of the Related Art Microfabrication techniques including lithography are employed in the process of manufacturing various electronic components including semiconductor integrated circuits such as LSIs. This technique is specifically implemented as the following process. 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 region of the resist film, a baking, a developing process, and a rinsing process are performed to selectively remove or leave the exposed region of the resist film to form a desired resist pattern. Form. Subsequently, the substrate surface (metal oxide film, metal film, etc.) is etched using the resist pattern as an etching-resistant mask, so that lines, spaces,
And a contact hole and the like are formed.

[0003] In recent years, in order to achieve high-density integration in accordance with high-density of electronic parts, ultra-fine resist patterns are required in the above-described technology. 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 excellent resist contrast. As the chemically amplified resist, specifically, a compound capable of generating an acid upon exposure (hereinafter referred to as a photoacid generator)
And a photosensitive composition containing a compound having a hydrophobic group decomposable 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. Among them, the former is a positive resist in which the second component generates a hydrophilic group by the action of the generated acid in the exposed region, and the exposed region is solubilized in a developing solution. On the other hand, the latter is a negative resist in which the exposed region is insolubilized in a developer because the crosslinking agent crosslinks the polymer by the action of the generated acid in the exposed region to increase the molecular weight. In these resists, since the photoacid generator functions as a catalyst, it can act on other components in a small amount and contribute to the formation of a fine pattern.

However, when a chemically amplified resist is used to form a pattern in accordance with the above-described conventional process, the amount of acid generated from the photoacid generator in the exposed region of the resist film is very small, so that the surrounding environment, especially the underlying The substrate is susceptible to the influence of the substrate, and a fine pattern cannot be stably formed. That is, impurities inevitably present on the substrate before the formation of the resist film diffuse in the resist film, or adsorb the acid generated from the photoacid generator at the interface with the substrate to deactivate the acid. As a result, the change in solubility of the resist film is alienated, 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 a conventional process. In the figure, the cross section of the resist pattern 22 formed on the substrate 21 has a footing, and lines and spaces having a desired width are not resolved. This is presumed to be due to the following reasons.

Generally, in a chemically amplified positive resist, a hydrophilic group is generated in the exposed region in the presence of a strong acid. However, in the exposed region, basic impurities such as amines inevitably present on the substrate inactivate the acid,
The generation of a hydrophilic group is suppressed, and the solubility in a developer becomes insufficient. Therefore, since the exposed region of the resist remains without being dissolved to some extent during the development process, particularly near the interface with the substrate, the cross-section is skirted as shown in FIG. 2 and the line and space having the desired width are formed. Not resolved.

In a negative chemically amplified resist,
The crosslinking reaction of the polymer proceeds by the weak acid in the exposed area. However, under the influence of acidic impurities inevitably present on the substrate, the cross-linking reaction further proceeds 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 the development is larger near the interface with the substrate, the cross-section is skirted as shown in FIG. 2, and the 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.
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 high-resolution pattern having a rectangular cross section and reduced influence of an underlying substrate.

[0009]

According to the pattern forming method of the present invention , the carbon content on the substrate is 20% by weight.
100% by weight of protective film from 50 to 10,000 on
Forming a range of angstroms, on the passivation layer, (a) a compound which generates an acid upon exposure (photo acid generator), and having a hydrophobic group capable of decomposing by an acid, a hydrophilic group after decomposition Or a photosensitive composition comprising (b) a compound capable of generating an acid upon exposure (photoacid generator), a polymer, and a crosslinking agent capable of crosslinking the polymer by the action of an acid Forming a resin film whose main component is an object, selectively exposing a predetermined area of the resin film, baking the exposed resin film at a predetermined temperature, Developing the resin film to selectively remove or leave exposed areas of the resin film.

According to the method of the present invention, the carbon content between the substrate and the resin film (resist film) is from 20% by weight to 10% by weight.
By interposing a protective film having a thickness of 50 to 10000 ° at 0% by weight , diffusion and influence of basic impurities and / or acidic impurities unavoidably present on the substrate into the resin film are reduced. The protective film also prevents the acid generated from the photoacid generator in the exposed region of the resin film from being adsorbed and diffused toward the substrate. Therefore,
In the exposed area of the resin film, the acid generated from the photoacid generator is
It works efficiently without deactivating other components of the photosensitive composition (chemically-amplified resist), and the change in the solubility of the photosensitive composition in a developing solution proceeds appropriately. In this way, a resist pattern having a rectangular 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 step is prevented. Therefore, there is no need to perform the process of promoting adhesion to the substrate surface, which has been performed before the formation of the resist film, and the pattern formation process is simplified. Less than,
One example of the pattern forming method of the present invention will be described in detail with reference to FIGS. First, a protective film 12 containing carbon as one component is formed on a substrate 11 (FIG. 1A).

The protective film containing carbon and the method of forming the carbon 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 carbon fine particles in a matrix made of a polymer material and applying the resultant.

[0013] The content of carbon in the protective film can be preferably set in a range of about 20% to 100% by weight. If the content is less than 20% by weight, it is 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 reduced. 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 10000 angstroms (hereinafter referred to as A)
Can be set in the 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 high dimensional accuracy.

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

Next, a solution containing the above-mentioned photosensitive composition (a) or (b) as a main component is applied on the protective film 12, and is preferably subjected to a pre-bake treatment at a predetermined temperature.
A resin film, that is, a resist film 13 is formed (FIG. 1B)
Illustrated).

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, a hydroxyl group of poly (p-hydroxy-α-methylstyrene) disclosed in U.S. Pat.
-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. Further, as a specific example of the composition (b) which is the negative resist, a solid resist
State Technology Vol. 32 (9) (198
9) described on pages 105 to 112 (J. Lingnau, R. Dammel,
J. Theis et al.) Include a composition containing an s-triazine derivative as a photoacid generator, a melamine derivative as a cross-linking agent, and a novolak resin as a polymer, and further, XP-89131 (commercially available) Name:
Shipley). Incidentally, if necessary, on this resist film, for the purpose of blocking the influence from the outside world,
An antireflection film or various protective films can also be formed.

Next, predetermined regions 14 of the resist film 13 are selectively exposed (arrows) (FIG. 1C). At this time, in the exposed region 14, the photoacid generator generates an acid. Note that, in the figure, reference numeral 15 corresponds to an unexposed area.

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

Further, the resist film 13 after the exposure is baked at a predetermined temperature, so that a reaction by the acid generated by the exposure proceeds to form a latent image on the exposed region 14 of the resist film (not shown). ). That is, when the resist film 13 mainly contains the composition (a), the exposed region 1
In 4, the compound having a hydrophobic group that can be decomposed by an acid is used as a catalyst to generate a hydrophilic group by 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 region 14, the acid serves as a catalyst, and the crosslinking agent crosslinks the polymer to increase the molecular weight.
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-described 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.
Further, it functions to prevent adsorption and diffusion of the acid generated in the exposed region 14 in the resist film 13 to the substrate 11 side.

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

Subsequently, the resist pattern 16 or 17
Is used as a mask to selectively remove the protective film 12 to form a protective film pattern 18 or 19 (FIG. 1F or 1G). This step can be performed, for example, by reactive ion etching (RIE) using a gas containing oxygen.

In the pattern forming method of the present invention as described above, after forming the protective film containing carbon as one component, before forming the resist film, the surface of the protective film is subjected to various treatments. Thus, 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 carbon-containing protective film includes, for example, introducing fluorine atoms to the surface of the protective film, annealing the protective film at a high temperature (about 300 to 1200 ° C.), and acid-protecting the protective film. 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 processes can be performed singly or in combination of two or more by appropriately setting conditions.

Ultrafine processing can be performed by selectively etching the underlying substrate using the resist pattern and the protective film pattern formed by the method of the present invention as an etching resistant mask.

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 section of the protective film pattern serving as a mask is very small, the etching accuracy of the underlying substrate can be further improved.

[0028]

The present invention will be described below in more detail 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 thickness of 1000 A was formed on a silicon nitride film having a thickness of 6000 A by a sputtering method. Next, a part of the hydroxyl group of poly (p-vinylphenol) was placed on this carbon film.
A solution of a polymer which is blocked by a tert-butoxycarbonylmethyl group and a solution of a positive chemically amplified resist containing triphenylsulfonium triflate is applied and dried on a hot plate at 90 ° C. for 90 seconds to form a resist having a thickness of 1 μm. A film was formed. Next, the resist film was exposed to light (exposure amount: 20 mJ / cm ²⁾ by a reduction projection exposure machine using a KrF excimer laser through a mask having a predetermined pattern on the resist film. ) Was done. Subsequently, the exposed resist film was baked on a hot plate at 90 ° C. for 90 seconds. Next, the resist film was added to an aqueous solution of 2.38% by weight of tetramethylammonium hydroxide for 9 hours.
By immersing for 0 second and developing, and further washing with water,
A resist pattern was formed. In the above process,
The resist film did not peel off during the developing process even if the conventional adhesion promoting treatment 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 was formed.

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

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

Further, 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, fine processing of the silicon nitride film could be performed with higher dimensional accuracy. did it.

Example 2 A resist pattern was formed in the same manner and under the same conditions as in Example 1, except that a 6000 A-thick BPSG film was used instead 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 high-precision 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 diameter 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 high-precision pattern having a rectangular cross section was formed.

Example 4 Instead of the positive resist, a negative chemically amplified resist XP was used.
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 becomes 0.2
5 μm, indicating that a high-precision pattern having a rectangular cross section was formed.

COMPARATIVE EXAMPLE On a 6000 A-thick BPSG film, a positive type containing a polymer obtained by partially blocking hydroxyl groups of poly (p-vinylphenol) with tert-butoxycarbonylmethyl group and triphenylsulfonium triflate Apply a solution of chemically amplified resist and place on a hot plate for 90
After drying at 90 ° C. for 90 seconds, a 1 μm-thick resist film was formed. Next, the resist film was exposed to light (exposure amount: 20 mJ / cm ²⁾ by a reduction projection exposure machine using a KrF excimer laser through a mask having a predetermined pattern on the resist film. ) Was done. Subsequently, the exposed resist film was baked on a hot plate at 90 ° C. for 90 seconds. Next, the resist film is immersed in a 2.38% by weight aqueous solution of tetramethylammonium hydroxide for 90 seconds for development processing,
Further, by 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 thickness of 1000 A was formed on a silicon nitride film having a thickness of 6000 A by a sputtering method. The substrate was then placed in a pre-evacuated reaction vessel. In this container, CF ₄
Gas and O ₂ gas at 100 cc / min and 50 cc / min, respectively.
cc and sent to the discharge tube inside the vessel at a frequency of 2.
A microwave of 45 GHz 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 tert-butoxycarbonylmethyl group and triphenylsulfonium triflate. A solution of a mold resist was applied and dried on a hot plate at 90 ° C. for 90 seconds to form a resist film having a thickness of 1 μm. Next, the resist film was exposed to light (exposure amount: 20 mJ / cm ²⁾ by a reduction projection exposure machine using a KrF excimer laser through a mask having a predetermined pattern on the resist film. )
Was done. Subsequently, the exposed resist film was baked on a hot plate at 90 ° C. for 90 seconds. Next, the resist film was immersed in a 2.38% by weight aqueous solution of tetramethylammonium hydroxide for 90 seconds, developed, and further washed with water to form a resist pattern. In the above process, the resist film did not peel off during the developing process even if the conventional adhesion promoting treatment 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 thickness of 400 A was formed on a BPSG film having a thickness of 10,000 A by a sputtering method. Next, the carbon film was annealed at 400 ° C. for 5 minutes in an argon gas atmosphere.

Subsequently, a resist film is formed, exposed to light, baked, and developed according to the same method and conditions as in Example 5, except that a specific mask is used for the exposure. (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, annealing is performed after forming a carbon film by the sputtering method. However, by heating the substrate at a high temperature while forming the carbon film by the sputtering method,
Annealing can also be performed.

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

Subsequently, a resist film is formed, exposed to light, baked, and developed according to the same method and conditions as in Example 5, except that a specific mask is used as an exposure mask. (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 treatment with the acidic solution and the treatment with the basic solution are used in combination. However, in practice, only one of these treatments can provide a sufficient effect.

Example 8 A WSi film having a thickness of 2000 A was formed on a WSi film having a thickness of 8
A carbon film of 00A was formed. Next, this carbon film was
After being exposed to a chlorine-based gas atmosphere at 0 ° C. for 3 minutes, a water washing treatment was performed using pure water for 5 minutes.

Subsequently, a resist film is formed, exposed to light, baked, and developed according to the same method and conditions as in Example 5 except that a specific mask is used as an exposure mask. (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.

Embodiment 9 A film having a film thickness of 4 was formed on an Al film having a thickness of 4000 A by sputtering.
A carbon film of 00A was formed. Further, 50 A of amorphous silicon was deposited on the carbon film by a sputtering method.

Subsequently, a resist film is formed, exposed to light, baked, and developed according to the same method and conditions as in Example 5, except that a specific mask is used for the exposure. (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 the amorphous silicon is deposited on the carbon film, annealing is performed at a higher temperature to reduce the influence of the reflected light from the underlying Al film on the resist film in the subsequent resist pattern forming step. It was possible. This suggests that, in the method of the present invention, by performing the surface treatment of the carbon film, a high-precision pattern can be formed even when a resist pattern is formed on a high-reflectance substrate such as an 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 high-resolution pattern having a rectangular cross section can be formed stably.
Furthermore, using such a high-resolution pattern as a mask,
By performing etching of the base substrate, ultrafine processing with extremely excellent dimensional accuracy is realized.

[Brief description of the drawings]

1A to 1G are cross-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 (72) Inventor Takahiro Ikeda 1 Toshiba-cho, Komukai, Koyuki-ku, Kawasaki-shi, Kanagawa Prefecture (56) References JP-A-3-139650 (JP, A) JP-A-1- 155625 (JP, A) JP-A-58-212136 (JP, A) JP-A-59-31025 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03F 7/11 G03F 7 / 038 G03F 7/039 H01L 21/027

Claims (1)

(57) [Claims] 1. The method according to claim 1 , wherein the content of carbon on the substrate is 20% by weight.
100% by weight of protective film from 50 to 10,000 on
A step of forming in the range of gstrom ; and (a) a photosensitizer containing, on the protective film, a compound having an acid generating by exposure and a compound having a hydrophobic group decomposable by the acid and generating a hydrophilic group after decomposition. (B) a photosensitive composition comprising: a compound capable of generating an acid upon exposure to light; a polymer; and a crosslinking agent capable of crosslinking the polymer by the action of the acid. Selectively exposing a predetermined region of the resin film; baking the exposed resin film at a predetermined temperature; developing the baked resin film to expose the resin film; Selectively removing or leaving the removed region.