JPH1130868A - Pattern forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of forming patterns having good dimensional reproducibility between substrate regardless of the storage time from resist coating application to electron beam writing. SOLUTION: This pattern forming method includes a stage for wiring the patterns on a positive type chemical amplification type resist film applied on a substrate by irradiation of the film with an accelerated electron beam, a stage for heat treating the resist film after the electron beam writing and a stage for subjecting the resist film after the heat treatment described above to development processing by a developer and selectively dissolving away the exposed parts of the resist film. The resist film described above is subjected to the heat treatment within three hours before writing by the electron beam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a pattern using a chemically amplified resist used for fine processing in a process of manufacturing a semiconductor device or the like.

[0002]

2. Description of the Related Art Microfabrication technology using photolithography has been employed in the manufacturing process of electronic components such as LSIs. That is, first, a resist solution is applied on a substrate or the like to form a resist film, and then the obtained resist film is passed through a predetermined mask.
Alternatively, after pattern light exposure is performed by directly scanning the beam, a resist pattern is formed by performing development processing with an alkali developing solution or the like. Subsequently, by exposing the exposed substrate or the like using this resist pattern as an etching resistant mask, fine lines and openings are formed, and finally the resist pattern is removed.

The resist used for such fine processing includes, for example, a resist (chemically amplified resist) disclosed in Japanese Patent Application Laid-Open No. 63-27829.

[0004] The chemically amplified resist is a composition containing an alkali-soluble resin, a dissolution inhibitor, and an acid generator. In this composition, the solubility in an alkali developer is suppressed by a dissolution inhibiting component in an unexposed state,
When exposure is performed by irradiating ultraviolet rays, X-rays, or high-energy electron beams, the acid generator is decomposed to generate an acid, and the acid is decomposed by the baking treatment. As a result, the exposed portion exhibits alkali solubility, and is developed with an alkali developer to form a positive resist pattern.

As described above, in the pattern formation using an acid-catalyzed positive resist, a very small amount of acid is generated by exposure, and a dissolution inhibitor is decomposed by a thermal decomposition reaction using the acid as a catalyst to expose the resist film. The pattern is obtained by increasing the dissolution rate of the developer in the developing solution. Since the acid generated by exposure is very small, it is easily affected by the environment.It is easily neutralized by a small amount of a basic substance present in the atmosphere or a hygroscopic substance on the substrate surface, and loses its catalytic function. . As a result, shape irregularities such as a hardly-solubilized layer on the surface and grooving occurred, and the resolution, pattern shape and reproducibility of dimensions were impaired.

The advantage of a chemically amplified resist is that sensitivity can be obtained with a small amount of exposure. What is particularly remarkable in the photoresist process is that the basic substance diffused into the resist film from the resist surface layer by the time until the post-exposure baking treatment inactivates the acid, and a hardly soluble layer is formed on the resist film surface layer. is there. In this case, the cross section of the pattern obtained after development has a so-called T-TOP shape.

[0007] Various measures have been taken to avoid such inconveniences. For example, the interval from exposure to baking is shortened as much as possible, a protective film is formed on the resist film, and a slight amount of a basic substance is added as a resist composition to reduce the influence of diffusion from the atmosphere.
In the photoresist process, a stepper or the like in which the steps from coating to development are inlined is usually used as an exposure apparatus. For this reason, the inconveniences described above can be avoided if the interval between processes is relatively short, and if the emphasis is particularly placed on the time until post-exposure baking or environmental control, which is particularly sensitive.

[0008] However, unlike a photoresist process in which coating, exposure, baking, and even a developing device are inlined, in the case of electron beam lithography, inlining is delayed from the viewpoint of productivity, and each process has been delayed. At present, the elapsed time is not fixed.

Particularly, in a mask manufacturing process using an electron beam, there is even a situation where a mask coated with a resist is already shipped, and the period from coating to exposure varies from several days to one month. is there. It is generally considered that about three days elapse before the mask blanks coated with the resist arrive from the manufacturer. Thus, in the case where the period from application to exposure is long, in the case of a chemically amplified resist, contamination from the storage atmosphere of the coated substrate is also sufficient to reduce the sensitivity with the resist, and between the substrates having different storage times. This has led to a decrease in dimensional reproducibility of the resist pattern.

[0010]

As described above, when a pattern is formed by electron beam lithography using a chemically amplified resist, after a resist film is formed on a substrate, it is necessary to store the resist film for a storage time until the lithography. In addition, since the stability of the resist characteristics is reduced, and the degree of the reduction varies depending on the length of the elapsed time, it has been difficult to form a resist pattern having desired dimensions between different substrates with good reproducibility.

Accordingly, the present invention provides a pattern forming method using a positive chemically amplified resist which can form a pattern with good dimensional reproducibility between substrates regardless of the storage time from resist coating to electron beam drawing. The purpose is to provide.

[0012]

In order to solve the above-mentioned problems, the present invention provides a method of drawing a pattern by irradiating a positive chemically amplified resist film coated on a substrate with an accelerated electron beam. Heating the resist film after the electron beam writing, developing the resist film after the heat treatment with a developer, and selectively dissolving and removing exposed portions of the resist film; And performing a heat treatment on the resist film within 3 hours before drawing by the electron beam.

Hereinafter, the present invention will be described in more detail. The chemically amplified resist used in the resist pattern forming method of the present invention includes, for example, a dissolution inhibitor, an organic compound for adjusting contrast, a compound that generates an acid by irradiation with actinic radiation (hereinafter, referred to as an acid generator), and It is a photosensitive composition containing a stabilizer.

The dissolution inhibitor is a compound having an alkali-soluble group that is decomposed by the catalytic action of an acid. Here, as the inhibitory group which is easily decomposed by an acid, for example, t-butyl ester, isopropyl ester, ethyl ester, esters such as methyl ester, tetrahydropyranyl ether, ethoxyethyl ether, ethers such as tetrahydrofuranyl ether, Acetals, alkoxycarbonates such as t-butoxycarbonate, methoxycarbonate and ethoxycarbonate, and silyl ethers such as trimethylsilyl ether and triethylsilyl ether can be exemplified. Specifically, examples of the dissolution inhibitor include the following compounds.

[0015]

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These dissolution inhibitors may be used in combination of two or more in order to maintain the dissolution rate and the properties as a resist. The dissolution inhibitor as described above, so that the content of the dissolution inhibiting group is in the range of 5 to 90 mol% with respect to the polar group imparting alkali solubility.
It is desired to adjust the blending amount. If the proportion of the dissolution inhibiting group is less than 5 mol%, the contrast between the exposed and unexposed parts cannot be obtained, while if it exceeds 90 mol%,
There is a possibility that the adhesion of the resist film to the substrate may be impaired.

The organic compound for adjusting contrast is a compound having alkali solubility, and examples thereof include polyhydroxystyrene, novolak phenols, and copolymers of hydroxystyrene and acrylic acid derivatives or styrene derivatives.

The compounding amount of the organic compound for adjusting the contrast can be appropriately determined according to the dissolution rate in a developing solution, the resist contrast and the like. As the acid generator,
For example, onium salt compounds such as sulfonyl and iodonium, and sulfonyl esters are used. More specifically, examples of the acid generator include the following compounds.

[0019]

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In the photosensitive composition used in the present invention, the amount of the acid generator is preferably 0.1 to 30 parts by weight, more preferably 0.3 to 15 parts by weight, based on the whole composition. Part or less. When the amount of the acid generator is less than 0.1 part by weight, it is difficult to form a resist pattern with high sensitivity. On the other hand, when the amount exceeds 30 parts by weight, the mechanical strength of the resist film is increased. This is because there is a risk that such factors will be impaired.

The stabilizer compounded in the photosensitive composition used in the present invention is a basic compound for reducing the influence of deactivation due to adsorption of the basic composition in the environment on the resist properties. As the basic compound, a compound that does not impair the original resist sensitivity can be used. Specifically, pyridine derivatives such as t-butylpyridine, benzylpyridine, and pyridinium salts, and aniline derivatives that are aromatic amines For example, N-methylaniline,
N-ethylaniline, N ′, N-dimethylaniline, diphenylaniline, N-methyldiphenylaniline, indene, and the like.

The amount of such a stabilizer is preferably from 0.1 to 50 mol%, more preferably from 1 to 15 mol%, based on the acid generator. 0.1mol
When the amount is less than 50%, it is difficult to sufficiently obtain the effect of the stabilizer. On the contrary, when the amount exceeds 50% by mole, the inherent sensitivity of the resist may be significantly reduced.

The photosensitive composition (positive chemically amplified resist) used in the present invention is prepared by dissolving a dissolution inhibitor, an organic compound for adjusting contrast, an acid generator and a stabilizer in an organic solvent. It can be prepared by filtration.

Examples of the organic solvent include ketone solvents such as cyclohexanone, acetone, ethyl methyl ketone and methyl isobutyl ketone; cellosolve solvents such as methyl cellosolve, methyl cellosolve acetate, ethyl cellosolve acetate and butyl cellosolve acetate; acetic acid Ethyl, butyl acetate, isoamyl acetate,
ester solvents such as γ-butyrolactone and methyl 3-methoxypropionate; glycol solvents such as propylene glycol monomethyl ether acetate; nitrogen-containing solvents such as dimethyl sulfoxide, hexamethylphosphoric triamide dimethylformamide, and N-methylpyrrolidone; In order to improve the solubility, a mixed solvent to which dimethyl sulfoxide, dimethylformaldehyde, N-methylpyrrolidinone and the like are added can be used.
Further, propionic acid derivatives such as methyl methyl propionate, lactic acid esters such as ethyl lactate, PGMEA (propylene glycol monoethyl acetate), and the like have low toxicity and can be preferably used. In the present invention,
Such solvents can be used alone or in combination of two or more. Further, isopropyl alcohol, ethyl alcohol, methyl alcohol, butyl alcohol, n-
Aliphatic alcohols such as butyl alcohol, s-butyl alcohol, t-butyl alcohol, and isobutyl alcohol, and aromatic solvents such as toluene and xylene may be contained.

In the method for forming a resist pattern according to the present invention, first, a varnish of a resist dissolved in an organic solvent as described above is applied on a predetermined substrate by a spin coating method, a dipping method or the like. Preferably 70 to
After drying at 120 ° C., a resist film is formed. The substrate used herein is, for example, a silicon wafer; a blank mask; a III-V compound semiconductor wafer such as GaAs or AlGaAs; a chromium or chromium oxide deposition mask; an aluminum deposition substrate; an IBPSG coated substrate; a PSG coated substrate; A carbon film sputtered substrate or the like can be used.

In the pattern forming method of the present invention, the above-described application of the resist and drying by heating for removing the solvent are not necessarily essential steps, and a resist film previously formed on a substrate or the like is prepared. May be. That is, it is also possible to obtain a resist-coated mask having an indefinite time after the formation of the resist film from a blank maker and form a resist pattern by the method of the present invention.

An electron beam is directly scanned on the surface of a resist film formed on a substrate or the like to draw a pattern on the resist film. In the present invention, the resist film is formed within three hours before the electron beam drawing. Then, a heat treatment is performed. If the interval from the end of the heat treatment to the drawing of the electron beam exceeds 3 hours, the inert substance is again adsorbed, so that it is difficult to obtain the effects of the present invention. The interval between the heat treatment and the electron beam drawing is more preferably 30 or less.

The conditions of the heat treatment are preferably a temperature and a time at which the glass transition temperature (T _g ) of the resist is higher and the decomposition rate of the dissolution inhibiting group in the resist film is 5 mol% or less. Below the glass transition temperature of the resist,
It becomes difficult to desorb the adsorbed material. On the other hand, if the decomposition rate of the dissolution inhibiting group in the resist film exceeds 5 mol%, dissolution may occur in the unexposed portion of the resist film after exposure.

In order to heat the resist film within 3 hours before exposure, an electron beam lithography apparatus having a heating means for heating the resist film immediately before exposure in air or vacuum is used. You may. That is, an electron gun that generates an electron beam, an electron lens system that shapes the electron beam, an electron lens barrel that includes a projection lens that projects the electron beam onto a resist-coated substrate, and transports and mounts the resist-coated substrate. An electron beam lithography apparatus having a stage and further having a heating means for subjecting a resist film to heat treatment immediately before exposure in air or vacuum.

If an exposure apparatus having such a baking device is used, workability is greatly improved. The resist film after the electron beam drawing is appropriately subjected to baking treatment at 150 ° C. or less by heating on a hot plate or in an oven, or by irradiating infrared rays. Thereafter, the resist film is developed by an immersion method, a spray method, a paddle method, or the like, and the resist film in the exposed portion is selectively dissolved and removed in an alkaline solution to form a desired resist pattern. Specific examples of the alkali solution that can be used here include an organic alkali aqueous solution such as an aqueous solution of tetramethylammonium hydroxide and choline, and an inorganic alkali solution such as potassium hydroxide, sodium hydroxide, sodium carbonate, sodium silicate, and sodium metasilicate. An aqueous solution, and a solution obtained by adding an alcohol, a surfactant, and the like to the aqueous solution are exemplified. Here, the concentration of the alkaline solution is preferably 15 mol% or less from the viewpoint of ensuring a sufficient difference in dissolution rate between the exposed part and the unexposed part.

In the present invention, the resist film is subjected to heat treatment immediately before electron beam writing on the resist film formed on the substrate or the like. Regardless, it has become possible to restore the reduction in the sensitivity of the resist and to improve the dimensional reproducibility between the substrates.

The sensitivity of the chemically amplified resist depends on the amount of acid generated by exposure and its diffusion. After the resist is coated on the substrate, during storage until exposure, volatile substances inside the resist film or acid deactivators from the storage atmosphere will be absorbed and desorbed, which is expected to cause a change in sensitivity. Is done.

The present inventors supposed the following two causes as a cause of lowering the sensitivity of the resist by lengthening the storage time after coating. The first cause is a decrease in the diffusion efficiency of the acid catalyst due to a change in the amount of the residual solvent, and the second cause is a decrease in the acid catalyst reaction due to adsorption of a deactivated substance during storage. As a result of intensive studies based on these, the present inventors found that 110 ° C.
By performing the above baking before exposure, the amount of residual solvent is settled to the minimum amount, and baking at a temperature of T _g or more of the resist reduces the free volume and the effect of reducing the absorption amount of the deactivated material. I found that there is. Further, the effect of removing the absorbing substance can be expected by the heat of baking.

Thus, the method of the present invention is such that by subjecting the resist film to heat treatment immediately before electron beam writing, all factors that cause a decrease in the sensitivity of the resist can be removed and the sensitivity of the resist coating film can be restored. Reached.

The pattern forming method of the present invention in which a heat treatment is performed immediately before drawing is a method which can be generally applied to a chemically amplified resist in which sensitivity is lowered by adsorption of a deactivated substance from the environment, and has high versatility. it is conceivable that.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples of the present invention. First, 60 parts by weight of a dissolution inhibitor having a structure represented by the following chemical formula,
A resist was obtained by dissolving 35 parts by weight of a polyhydroxystyrene for contrast adjustment, 5 parts by weight of an acid generator, and a stabilizer in methoxymethylpropionic acid. In addition, the compounding quantity of the stabilizer was 8 mol% with respect to the acid generator.

[0037]

Embedded image (Example 1) The obtained resist was applied on a 5-inch mask substrate by a spin coater to a thickness of 0.5 μm,
Was performed for 5 minutes to remove the solvent.

The resist film having been baked at 100 ° C. was stored in a storage box for a predetermined time, and baked at 120 ° C. for 90 seconds immediately before exposure. The time from the end of baking to the start of exposure was 3 hours.

The substrate after the heat treatment is processed by an electron beam drawing apparatus.
A punch pattern of 1 μm was drawn at 4 μC / cm ² . Then, after baking after exposure for 3 minutes at 60 ° C., 2.
The exposed portion of the resist film was selectively dissolved and removed by developing with a 38% aqueous solution of tetramethylammonium hydroxide to form a positive resist pattern.

The pattern size of the obtained design size of 1 μm was measured, and the results are shown in Table 1 below with respect to the storage time in the storage box. Comparative Example 1 Same as Example 1 except that the resist film after baking at 100 ° C. for removing the solvent was stored in a plastic storage box for a predetermined time and was not subjected to the heat treatment immediately before exposure. The resist pattern was formed by the method described in (1).

The obtained pattern size having a design size of 1 μm was measured, and is shown in Table 2 below with respect to the storage time in the storage box. (Comparative Example 2) Subsequent to baking at 100 ° C. for removing the solvent, the resist film was baked at 120 ° C. for 90 seconds, stored in a plastic storage box for a predetermined time, and then exposed. A resist pattern was formed in the same manner as in Example 1 except for the above. The resulting pattern dimensions of the designed dimensions of 1 μm were measured and summarized in Table 3 below for the storage time in the storage box.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

As shown in Table 1, when baking was performed immediately before exposure (Example 1), the dimensional variation remained at 0.108 μm even after being left for 504 hours.
In the normal mask manufacturing process, the time for which the mask coated with the resist is left is about 3 days to 3 weeks. If the dimensional variation is within the above-mentioned range within such a leaving time, it is sufficiently acceptable, and it can be seen that the change in the sensitivity of the resist is improved by the method of the present invention.

On the other hand, when the baking treatment before the exposure was not performed (Comparative Example 1), as shown in Table 2, the fluctuation of 0.148 μm occurred even after being left for 168 hours. In the case where the treatment was performed continuously after the application and in the pre-bake (Comparative Example 2), as shown in Table 3, there was a remarkable fluctuation of 0.201 μm or more even after being left for 168 hours. As described above, by performing baking on the resist film immediately before exposure, the width of dimensional variation was reduced, and dimensional reproducibility between substrates was improved.

[0047]

As described in detail above, according to the present invention,
Provided is a pattern forming method capable of reducing a decrease in resist sensitivity due to a lapse of time from resist coating to exposure and improving reproducibility of an obtained pattern dimension. By using the method of the present invention in which a resist film immediately before exposure is subjected to a baking process, even when using a coated mask purchased from a blank maker, a dimensional variation between substrates is suppressed to form a resist pattern with good reproducibility. It is possible to do. INDUSTRIAL APPLICABILITY The present invention is effective in improving the reproducibility of microfabrication of electronic components using a chemically amplified resist, and its industrial value is large.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Makoto Nakase 1st, Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba R & D Center (72) Inventor Hiroto Yasue Komukai, Sai-ku, Kawasaki-shi, Kanagawa No. 1 Toshiba Town Co., Ltd.Toshiba R & D Center (72) Inventor Hideaki Sakurai No. 1 Komukai Toshiba Town, Koyuki-ku, Kawasaki City, Kanagawa Prefecture Co., Ltd. No. 1, Komukai Toshiba-cho, Sachi-ku Inside Toshiba R & D Center

Claims (1)

[Claims] 1. A step of irradiating an accelerated electron beam to a positive chemically amplified resist film applied on a substrate to draw a pattern, and a step of heating the resist film after drawing the electron beam. And a step of developing the resist film after the heat treatment with a developing solution to selectively dissolve and remove exposed portions of the resist film, wherein the process is performed within 3 hours before drawing with the electron beam. A pattern forming method, wherein a heat treatment is performed on the resist film.