KR980012107A - Method of forming resist pattern - Google Patents

Abstract

The present invention provides a step of forming a positive resist film on a substrate to form a positive resist pattern which improves the performance of the resist by inhibiting the formation of the surface poorly soluble layer of the resist film and improving the affinity of the resist film surface to the developer. (A), patterning by irradiating the active film to the resist film (B), the active surface is used for patterning and absorbed by the resist film at a predetermined exposure amount of the film thickness is hardly reduced after development A method of forming a resist pattern, comprising the step (C) of exposing to a light beam different from the line and the step (D) of irradiating for patterning and exposing the entire surface and then developing (D).

Description

Method of forming resist pattern

The present invention relates to a method of forming a positive resist pattern in a positive semiconductor manufacturing process.

The positive resist pattern is usually formed by the following method. First, a positive resist is applied on a substrate such as a silicon wafer to form a resist film, and then the resist film is irradiated with active rays such as light beams or X-rays through a mask or scanning active rays such as electron beams or ion beams. Alkali development using increased solubility of the irradiated portion in alkali removes only the irradiated portion to obtain a final pattern.

Known methods of forming a resist pattern can adversely affect the resolution of a resist by generating a poorly soluble layer on the surface of the resist film. In positive resists comprising a quinone diazide photosensitive agent and a novolak resin, for example, when the resist film is thin or the reflectance of the substrate is high, especially when heat treatment is performed after light irradiation, the surface poorly soluble layer lowers the resolution. Let's do it. In a chemically amplified positive resist using a photoacid generator, amines present in air deactivate the acid and form a surface poorly soluble layer. As is well known, this reduces the resolution, significantly changes the performance of the resist depending on the time from irradiation to post-exposure heat treatment (this is commonly referred to as the time-delay effect), and only the surface portion of the T-shaped unfolded. Generate a profile.

Defects often occur in patterns even after alkali development. This defect phenomenon is usually considered to be caused by bubbles generated when the developer is applied to the resist film and by micro bubbles due to the gas dissolved in the developer. The smaller the contact angle of the developer on the resist surface, the less development defects (see The Porseedings of the 43rd Applied Physics Joint Conference, 1996 Spring-Term, 27p-ZW-7 and 27p-ZW-9).

As such, one of the objects of the present invention is to solve various problems caused by such a phenomenon, namely, a resolution degradation, a profile deterioration, and a time-delay effect, by preventing the formation of the surface hardening layer of the resist film.

It is still another object of the present invention to reduce the development defect by improving the surface affinity of the resist film for the developer and suppressing the generation of fine bubbles.

The inventors of the present invention have completed the present invention as a result of earnest research to achieve the above object.

The present invention provides a method of forming a positive resist film on a substrate (A), irradiating active lines for patterning the resist film (B), and absorbing the resist film over the entire surface of the resist film and using in step (B). Exposing a light beam that is different from the active line to a predetermined exposure dose that does not substantially cause a film thickness reduction after development, and then performing development after performing steps (B) and (C). A method of forming a resist pattern is provided.

In the present invention, a positive resist film is formed on a substrate using a known method, and the resist film is irradiated with active lines for patterning. In the case of the positive resist which can be used in the present invention, the portion irradiated with active lines is dissolved in the developer and removed by the development treatment, and the portion not irradiated remains as a pattern. Examples of positive resists that are available include quinone diazide sulfonates of phenolic hydroxy group containing compounds or alkali soluble resins such as novolak resins, such as quinone diazide sulfonates of phenolic hydroxy group containing compounds or aromatic amides of quinone diazide sulfonic acids. Quinone diazide type positive resist; And chemically amplified positive resists, which include alkali-soluble resins and acid generators having groups that can be removed by the action of an acid, and may further contain additives such as dissolution inhibitors and sensitizers. Typically, a resist solution is prepared by dissolving the above-mentioned components in an organic solvent, and then applying the resist solution thus prepared to a substrate such as a silicon wafer, and then drying the applied resist solution to form a resist film. Patterning is carried out by irradiating the thus formed resist film with radiation such as near or medium ultraviolet rays, far ultraviolet rays or X-rays through a mask having a predetermined pattern or by scanning a beam such as an electron beam or an ion beam.

In addition to the conventional irradiation steps mentioned above for patterning, the method of the present invention has a step of exposing the entire surface of the resist film to light beams at an exposure dose that does not substantially reduce the film thickness after development. This step allows the light beam to act only on the surface portion of the resist film, thereby solving the problem of surface poorly soluble layer and microbubble generation. The light beam used to expose the entire surface of the resist film needs to be different from the active line used for patterning and need to be absorbed by the resist film.

When light beams such as ultraviolet light are used for patterning, the absorbance of the resist film for the light beam used for exposure of the entire surface needs to be higher than the absorbance of the resist film for the light beam used for patterning. For example, when a g-ray or i-ray resist containing a quinone diazide type photosensitive agent is used, it is necessary to use an optical beam having a wavelength of 300 nm or less for exposure of the entire surface, which is a resist for an optical beam having a wavelength of 300 nm or less. This is because the absorbance of the film is higher than the absorbance of g line or i line. Examples of available light sources of light include a 254 nm mercury lamp line, a 248 nm KrF excimer register beam, a 222 nm KrCl excimer lamp, a 193 nm ArF excimer laser beam, a 172 nm Xe ₂ excimer lamp, a 146 nm Kr ₂ excimer lamp, a 126 nm Ar ₂ excimer lamp and deuterium lamp. When using chemically amplified resists exposed to KrF excimer laser beams for patterning, it is necessary to use light beams having a wavelength of 230 nm or less for exposure of the entire surface. Light use Examples of possible light sources include KrCl excimer lamp of 222nm, of 193nm ArF excimer laser beam, a mercury lamp line of 172nm Xe ₂ excimer lamp of 185nm, of 146nm Ar ₂ excimer lamp, Ar ₂ excimer light of 126nm, a deuterium lamp, Ultraviolet light filtered by an interference filter is included so that the maximum absorption (λ max) is 230 nm or less. When a chemically amplified resist exposed to an ArF excimer laser beam is used, the light source for exposure of the entire surface is selected from, for example, an optical beam having a wavelength of 185 nm or less in consideration of absorption of the resin. Examples of available light sources include mercury lamp lines of 185 nm, Xe ₂ excimer lamps of 172 nm, Kr ₂ excimer lamps of 146 nm, Ar ₂ excimer lamps of 126 nm and deuterium lamps.

On the other hand, when scanning rays such as electron beams or electromagnetic waves of far short wavelength such as X-rays are used for patterning, light beams absorbed by the resist film can be used for exposure of the entire surface. Thus, in this case it is possible to use a light source for exposure of the entire surface mentioned above.

It is preferable that the light beam used for exposure of the whole surface has an absorbance of 1.5 or more, more preferably 2 or more, per 1 mu m of the thickness of the resist film. Experiments have shown that "Sumi-Resist PFI-38", a positive resist for exposure to i-rays containing a quinone diazide compound and a novolak resin as a photosensitizer (manufactured by Sumitomo Chemical Co., Ltd.) The resist film with a thickness of 0.4 mu m obtained from has a absorbance of 0.8 for a KrF excimer laser beam having a wavelength of 248 nm (this value corresponds to an absorbance of 2.0 per 1 mu m of the thickness of the resist film). As another example, a 0.7 μm thick resist film obtained from a chemically amplified positive resist containing poly (p-vinylphenol) as a resin and exposed to KrF excimer laser beams has an absorbance for an ArF excimer laser beam having a wavelength of 193 nm. Is 2.5 (this value corresponds to an absorbance of 3.6 per 1 탆 thickness of the resist film).

In the process of exposing the entire surface to the light beam, the exposure dose should be set such that virtually no reduction in thickness is caused after development. "After development, virtually no reduction in film thickness is caused" means that there is no significant difference between the film thickness of the developed pattern after exposure of the entire surface and the film thickness of the developed pattern without exposure of the entire surface and the former shape is It is equivalent to or more than shape. In the case of a quinone diazide positive resist, the difference in film thickness is preferably 10 kPa or less. On the other hand, in the case of a chemically amplified positive resist, since the effect of performance is hardly affected until the thickness difference of 15 kPa, it is preferable that the film thickness difference is usually 200 kPa or less, in some cases 50 kPa or less. In the process of exposing the entire surface to the light beam, the exposure amount is set so that the phenomenon that the surface poorly soluble layer is formed is virtually eliminated. The sufficient exposure amount depends on the type of positive resist and the irradiation conditions for patterning and can be determined by simple preliminary experiments.

The effect of the invention can be achieved when the irradiation for patterning and the exposure of the entire surface are carried out in this order or in the reverse order.

When heat treatment is performed after light irradiation, it is generally carried out after irradiation for patterning or after irradiation for patterning and exposure of the entire surface. In the case of using a quinone diazide type resist, irradiation (1) for patterning, exposure (2) of the entire surface, and heat treatment after light irradiation (3) are carried out from (1) → (2) → (3), (2) → (1) → (3) or (1) → (3) → (2), and (1) → (2) → (3) or (2) → (1) → (3 Is preferred.

In the case of using a chemically amplified resist, the order of (1) → (3) → (2) is preferred.

After irradiation for patterning and exposure of the entire surface, development is carried out according to known methods to obtain a positive pattern. Alkaline aqueous solution is normally used for image development. Examples of the available developer include an aqueous solution of tetramethylammonium hydroxide and an aqueous solution of 2-hydroxyethyltrimethylammonium hydroxide.

EXAMPLE

The present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. In the following description,% and parts refer to% by weight and parts by weight, unless otherwise specified.

Example 1

A positive resist for exposure to i-rays containing a quinone diazide compound as a photosensitizer and a novolak resin ("Sumi-Resist PFI-38" manufactured by Sumitomo Chemical Co., Ltd.) was 0.75 탆 thick on a silicon wafer. Apply with Pre-bake is performed at 90 ° C. for 60 seconds on a direct hot plate. The wafer coated with the resist film is then exposed to an i-line stepper ("NSR 2005 i9C" manufactured by Nikon Corp., NA = 0.57, sigma = 0.60) to form a line and space pattern. The entire surface of the resist film is then exposed to the KrF excimer laser beam (248 nm) emitted by KrF excimer stepper ('NSR 1755 EX8A' manufactured by Nikon Corp.) at the exposure doses specified in Table 1. A post-exposure bake is carried out on a proxy plate hot plate at 110 ° C. for 60 seconds, followed by a paddle development for 60 seconds with a 2.38% aqueous solution of tetramethylammonium hydroxide.

The wafer after development is observed with a scanning electron microscope to evaluate the resolution and the profile. The resolution is expressed by the minimum size of the line and space pattern to be separated without decreasing the film thickness with an exposure table (patterned exposure amount shown in Table 1) in which the line and space pattern of 0.40 mu m is 1: 1. The profile is judged as the cross-sectional shape of the line and space pattern of 0.40 mu m at the same exposure dose. The film thickness of the pattern developed after exposure of the entire surface and the pattern developed without exposure of the entire surface was measured by an optical film thickness meter ("Lambda A" manufactured by Dainippon Screen MFG. Co., Ltd.) The difference is indicated by the film thickness reduction amount. The measurement results are shown in Table 1.

TABLE 1

As shown in Table 1, the resist patterns (Experimental Examples 1 and 2) developed by exposing the entire surface to the extent that a reduction in film thickness after the development was virtually not caused have a rectangular profile and improved resolution.

Example 2

(1) Preparation of Resist

The chemically amplified positive resist comprises 13.5 parts of tert-butoxycarbonyl methyl etherified poly (p-vinylphenol) with 33% of the hydroxide groups as the resin and N- (10-camphorsulol as the acid generator. To a solvent containing 5 parts of propylene glycol monomethyl ether acetate and 13.2 parts of ethyl lactate were added a mixture of 1.0 part of polyvinyloxy) succinimide, 0.27 parts of 2-hydroxycarbazole as a sensitizer and 0.054 parts of p-isopropylaniline as an additive. Prepare by dissolving.

(2) Formation of resist film and evaluation thereof

A chemically amplified positive resist is applied to the silicon wafer at a thickness of 0.70 mu m. Preheat for 60 seconds at 90 ° C. on a direct hot plate. The wafer coated with the resist film is exposed to a KrF excimer stepper (manufactured by Nikon Corporation, NSR 1755 EX8A ″) to form lines and space patterns. After each of the periods specified in Table 2, the post-exposure heat treatment is performed for 60 seconds at 100 ° C. on the direct hot plate. Immediately after the post-exposure heat treatment, the entire surface of the resist film is exposed to the radiation of a 500W deep UV lamp (product of Ushio Kagashi K.K.) that has previously been passed through a filter having a center wavelength of 227.5 nm and a half width of 16.1 nm. Let's do it. Immediately after exposing the entire surface, paddle development is carried out for 60 seconds in a 2.38% aqueous solution of tetramethylammonium hydroxide.

After development, the wafer is observed with a scanning electron microscope and the resolution and profile are evaluated. The resolution is represented by the minimum size of the line and space pattern, which is separated without reducing the film thickness using exposure (patterned exposure shown in Table 2) in which the 0.40 μm line and space pattern is in a 1: 1 ratio. A profile is represented by the cross-sectional shape of the line and space pattern of 0.40 micrometer in the same exposure, and is evaluated by the following 3 grades.

◎: T-shaped profile does not appear virtually.

: T-shaped profile is not visible.

X: T-type profile is clear.

After exposing the entire surface, the film thickness of the developed pattern and the film thickness of the developed pattern without exposing the entire surface are measured in the same manner as in Example 1, and the difference in film thickness is given as a decrease in film thickness. The measurement results are shown in Table 2.

TABLE 2

In Experimental Example 12, the resolution of the 3 μm line and space pattern does not appear even at an exposure dose of 200 mJ / cm 2 for the time delay effect.

As shown in Table 2, the resist pattern (Experimental Examples 6 to 9) after the whole surface exposure showed a good profile, and a decrease in the resolution was shown even when 25 minutes had elapsed after the patterned exposure.

Example 3

(1) Preparation of Resist A

The chemically amplified positive resist comprises 13.5 parts of tert-butoxycarbonyl methyl etherified poly (p-vinylphenol) with 33% of the hydroxide groups as the resin and N- (10-camphorsulol as the acid generator. A mixture of 1.0 part of polyvinyloxy) succinimide, 0.27 parts of 2-hydroxycarbazole as a sensitizer and 0.02 parts of 2,6-diisopropylaniline as an additive, contains 52.8 parts of propylene glycol monomethyl ether acetate and 13.2 parts of ethyl lactate It is prepared by dissolving in a solvent.

(2) Preparation of Resist B

The chemically amplified positive resist comprises 13.5 parts of a poly (p-vinylphenol) tert-butoxycarbonylated with 40% of the hydroxide groups as the resin and N- (10-camphorsulfonyloxy) as the acid generator. A mixture of 1.0 parts of succinimide, 0.27 parts of 2-hydroxycarbazole as a sensitizer and 0.02 parts of 2,6-diisopropylaniline as an additive was added with 43.7 parts of 2-heptopone; It is prepared by dissolving in a solvent containing 2.3 parts of butyrolactone.

(3) Formation of resist film and evaluation thereof

The prepared resist A and resist B were each applied on a silicon wafer at a thickness of 0.72 mu m. Preheat for 60 seconds at 90 ° C. on a direct hot plate. The wafer coated with the resist film is exposed to a KrF excimer stepper (NSR 1755 EX8A ″, manufactured by Nikon Corporation) to form lines and space patterns. After each of the periods specified in Table 3, the post-exposure heat treatment is performed for 60 seconds at 100 ° C. on the direct hot plate. Immediately after the post-exposure heat treatment, the entire surface of the resist film was subjected to 172 nm Xe ₂ excimer lamp (Ushio Kagushi, Ltd., "UER 20-172") or 222 nm KrCl excimer lamp (Ushio Kagushi, Ltd., "UER 20". -222 "). Immediately after exposing the entire surface, paddle development is carried out for 60 seconds in an aqueous solution of 2.38% of tetramethylammonium hydroxide.

After development, the wafer is observed with a scanning electron microscope and the resolution and profile are evaluated. The resolution is represented by the minimum size of the line and space pattern, which is separated without reducing the film thickness using exposure (patterned exposure shown in Table 3) in which the line and space pattern of 0.35 占 퐉 is 1: 1. A profile is shown by the cross-sectional shape of the 0.35 micrometer line and space pattern in the same exposure, and is evaluated using the same reference | standard as Example 2. After exposing the entire surface, the film thickness of the developed pattern and the film thickness of the developed pattern without exposing the entire surface are measured in the same manner as in Example 1, and the difference in film thickness is given as a decrease in film thickness. The measurement results are shown in Table 3.

TABLE 3

As shown in Table 3, the resist patterns developed after exposing the entire surface (Experimental Examples 13 to 15) exhibited a good profile and no degradation in resolution even after 20 minutes after patterned exposure.

Example 4

A positive resist exposed to i-line (Sumitomo Chemical Co., Ltd. product, "Thermite-resist PFI-38") is applied to a silicon wafer at a thickness of 1.065 mu m. Preheat treatment is carried out at 90 ° C. for 60 seconds on a direct hot plate. The wafer coated with the resist film is exposed to an i-line stepper (product of "NSR 2005 i9C", NA = 0.57 by Nikon Corporation) to form a line and space pattern. The entire surface of the resist film is exposed to radiation of a 172 nm Xe ₂ excimer lamp (product of Ushio Corporation, "UER 20-172"). To reduce the irradiation, the wafer is placed at a distance of 7.5 mm from the irradiation window of the excimer lamp. After post-exposure heat treatment at 110 ° C. for 60 seconds on a direct hot plate, paddle development is carried out for 60 seconds in a 2.38% aqueous solution of tetramethylammonium hydroxide.

After development, the wafer is observed with a scanning electron microscope and the resolution and profile are evaluated. The resolution is represented by the minimum size of the line and space pattern, which is separated without reducing the film thickness using an exposure (patterned exposure shown in Table 4) in which the line and space pattern of 0.35 탆 is 1: 1. The profile is represented by the cross-sectional shape of a 0.35 µm line and space pattern in the same exposure. After exposing the entire surface, the contact angle with the developer on the resist film is also measured. The measurement results are shown in Table 4.

TABLE 4

As shown in Table 4, the resist pattern (Experimental Example 20) developed by exposing the entire surface to the extent that the reduction in film thickness after development is virtually not caused, while the resolution or profile is not degraded, Reduce the contact angle This effectively reduces development defects caused by fine bubbles and the like.

Example 5

Resist A prepared in Example 3 (1) was applied on a silicon wafer to a thickness of 0.96 mu m. Preheat for 60 seconds at 90 ° C. on a direct hot plate. A wafer coated with a resist film is exposed to an electron beam from an electron beam exposure apparatus ("ELS-3300", manufactured by ELIONIX CORPORATION) to form a pattern of 80 탆 x 60 탆. Exposure of the electron beam is varied step by step at an acceleration voltage of 25 kV. After the period specified in Table 5 has elapsed, the post-exposure heat treatment is performed at 100 ° C. for 90 seconds on a direct hot plate. Immediately after the post-exposure heat treatment, the entire surface of the resist film is exposed to radiation of a 172 nm Xe ₂ excimer lamp (product of Ushio Corporation, "UER 20-172") with the wafer in close contact with the irradiation window. The illuminance of the lamp is 5 mW / cm 2. Immediately after exposing the entire surface, it is developed for 60 seconds in an aqueous solution of 2.38% of tetramethylammonium hydroxide.

After development, the wafer is observed with a scanning electron microscope and the missing sensitivity (Eth) is measured. After exposing the entire surface, the film thickness of the developed pattern and the film thickness of the developed pattern without exposing the entire surface are measured in the same manner as in Example 1, and the difference in film thickness is given as a decrease in film thickness. The measurement results are shown in Table 5.

TABLE 5

As shown in Table 5, when the resist film is exposed to the patterned electron beam, the entire surface is exposed to effectively reduce the decrease in sensitivity even after a long period of time after irradiation.

As mentioned above, the method of the present invention reduces the formation of the surface poorly soluble layer of the resist pattern and improves the affinity of the resist film for the developer, thereby reducing development defects due to fine bubbles. Therefore, the resist pattern formed by the method of the present invention is excellent in performance.

Claims (7)

Forming a positive resist film on a substrate (A), irradiating an active line to the resist film and patterning it (B), by the resist film at a predetermined exposure amount at which the film thickness is hardly reduced after development of the entire surface of the resist film A resist pattern comprising the steps of (C) absorbing and exposing to a light beam different from the active line used in step (B); and performing step (D) after performing steps (B) and (C). Formation method. The method of claim 1, wherein the light beam used to expose the entire surface has an absorbance of at least 1.5 per 1 μm thickness of the resist film. 2. The absorbance of a resist film according to claim 1, wherein the active line used for patterning is a light beam, and the light beam used for exposing the entire surface is higher than the absorbance of the resist film at a wavelength of the light beam used for patterning. A method having a wavelength representing. The method of claim 3, wherein the positive resist comprises a quinone diazide photosensitive agent and an alkali soluble resin. The method of claim 1 wherein the positive resist comprises an alkali soluble resin and an acid generator. The method of claim 1, wherein the active line used for patterning is an electron beam or X-ray. The method of claim 1, wherein the entire surface is exposed after irradiating and patterning active lines. ※ Note: The disclosure is based on the initial application.