JPS62129849A - Stabilizing method for positive type photoresist pattern - Google Patents

Abstract

PURPOSE:To obtain the titled pattern having a high thermal strength and having a less tendency for generating a crinkling on a surface of the pattern and having a high reproducibility by effecting the thermal processing and the UV ray radiation processing of the resist pattern after developing it, in order, respectively. CONSTITUTION:The resist pattern is formed on a substrate and then the obtd. resist pattern is heated at a temperature which does not generate a deformation of the resist pattern. The processing temp. is usually 80-120 deg.C. As mentioned above, the resist pattern is heated followed by radiating the UV ray to the whole surface of the pattern. The UV ray radiation may be carried out immediately after the heat processing or may be carried out after cooling it to a room temperature. By stabilizing the resist pattern as mentioned above, the resist pattern having the remarkably improved thermal stability, and the less tendency for generating the crinkling on the surface of the pattern, and having the excellent reproducibility is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for stabilizing positive photoresist patterns. More specifically, the present invention provides ultra-L
The present invention relates to a stabilization method for obtaining a positive photoresist pattern with significantly improved thermal stability, no wrinkles on the surface, and extremely high reproducibility, which is suitable for the production of semiconductor devices such as SI. .

BACKGROUND OF THE INVENTION In recent years, in the manufacture of semiconductor devices, the density and degree of integration have been increasing, and as a result, microfabrication on the submicron order is required for forming micropatterns by photolithography processes. For this reason, in pattern formation in the manufacture of semiconductor devices, i-! ! Negative photoresists have been mainly used in the past, but instead of negative photoresists, high-resolution positive photoresists that can provide pattern widths of 1 to 2 μm are becoming mainstream.

On the other hand, in the manufacture of semiconductor devices, a substrate is usually subjected to photolithography and etching processes multiple times, so that the substrate has steps. Then, when forming a pattern on such a substrate using a positive photoresist.

The difference in level of the substrate causes scattering of actinic rays and defocus, resulting in a problem that a desired resolution cannot be obtained.

As a means of solving such problems, a method is known in which conventionally, a positive photoresist containing an ultraviolet absorber is used to eliminate halation from the substrate. However, in order to form fine patterns on the submicron order,
As described above, it is necessary to improve the positive photoresist used to eliminate halation from the substrate and to improve the thermal strength of the photoresist film.

This is because the thermal strength of the photoresist greatly affects the etching, lift-off, and other processes performed after pattern formation.

By the way, in one photolithography process when using a positive photoresist in the manufacture of semiconductor devices, first, a positive photoresist is applied onto a substrate and dried to form a photosensitive layer, and then actinic rays are applied to the photosensitive layer. After selectively irradiating to form an image, development is performed to form a resist pattern. This resist pattern is usually subjected to a heat treatment in order to improve its thermal strength, and then transferred to an etching process.

In this etching process, in recent years, with the trend toward finer patterns, dry etching methods such as plasma etching and active ion etching have been used.Furthermore, with the miniaturization of resist patterns, extremely fine lines can be produced. Etching processing is required. Therefore, in order to meet such demands, the emergence of a resist pattern with excellent thermal strength is strongly desired.

However, the conventional heat treatment after development has a limit in improving the thermal strength of the resist pattern, and it is difficult to meet the above requirements. Therefore, various methods have been proposed for the purpose of further improving the thermal strength of the resist pattern. For example, a method has been proposed in which a developed resist pattern is irradiated with ultraviolet rays in the wavelength range of 200 nm to 300 nm for several seconds, called deep UV. This ultraviolet irradiation treatment crosslinks the resin component of the photoresist by the action of ultraviolet rays, increases the softening point of the photoresist itself, and increases the heat treatment temperature to obtain a resist pattern with improved thermal strength. It is something.

However, in this processing method, the upper layer of the resist pattern layer is mainly crosslinked, so although the upper layer, middle layer, and lower layer of the resist pattern layer are continuous, the degree of crosslinking is different, and as a result, Due to the effect of stress, wrinkles occur on the surface of the resist pattern, the shape changes, and dimensional accuracy inevitably decreases.

Therefore, this processing method cannot be said to be a practical method in a field where high precision is required, such as the manufacture of semiconductor devices.

Another method for improving the thermal strength of a resist pattern is to irradiate the entire surface of the resist pattern with ultraviolet rays while heating the resist pattern layer to a temperature of 80 to 150°C. A method has been proposed for obtaining a resist pattern with improved thermal strength and less generation (Japanese Unexamined Patent Publication No. 135943/1983). In this method, crosslinking from the upper layer of the resist pattern by ultraviolet rays is
This method reduces the internal stress of the resist pattern by heating it to 0° C., thereby improving the thermal strength while preventing the occurrence of wrinkles.

However, although this method shows the effect of preventing wrinkles to some extent, it is necessary to control many conditions such as heating temperature, time, and amount of UV irradiation in order to perform UV irradiation and heat treatment at the same time. In the manufacture of semiconductor devices, which is difficult to adjust and requires highly accurate reproducibility, there is a problem in that defective products often occur and the yield rate decreases. Moreover, the resist pattern layer after development processing contains water, solvent, etc. as evaporable components, and even if these components are activated by heat treatment and try to evaporate from within the resist pattern, the resist pattern layer due to ultraviolet irradiation may Since crosslinking of the surface portion occurs at the same time, it is trapped inside the resist pattern, resulting in problems such as inhibiting improvement in the thermal strength of the pattern and impairing reproducibility. Therefore, this method is still not a fully practical method in the semiconductor industry.

Furthermore, in response to the trend toward finer patterns in recent years, positive photoresists containing ultraviolet absorbers are increasingly being used to prevent nolation from the substrate, as described above. The above method using a positive photoresist (Japanese Unexamined Patent Publication No. 135943/1983)
A new problem has arisen in that many wrinkles appear on the surface of the resist pattern.

By the way, this positive photoresist containing an ultraviolet absorber is attracting attention as it can respond to the miniaturization of patterns, which is expected to progress further in the future. Therefore, a resist pattern stabilization method that is effective even for such positive photoresists is extremely important, and its development is strongly desired.

Problems to be Solved by the Invention The purpose of the present invention is to meet the above-mentioned needs by using a positive photoresist containing an ultraviolet absorber, which has a remarkable thermal strength and is suitable for manufacturing semiconductor devices such as VLSI. It is an object of the present invention to provide a method for stabilizing a positive-type photoresist pattern, which is capable of obtaining a positive-type photoresist pattern which has high reproducibility and is free from wrinkles on the surface.

Means for Solving the Problems The inventors of the present invention have conducted intensive research to achieve the above object, and have achieved the object by separately sequentially subjecting the developed resist pattern to heat treatment and ultraviolet irradiation treatment. The present invention was completed based on this finding.

That is, in the present invention, a photosensitive layer made of a positive photoresist containing an ultraviolet absorber is subjected to a required image-forming exposure, and then developed to form a resist pattern, and then the resist pattern does not undergo deformation. The present invention provides a method for stabilizing a positive photoresist pattern, which comprises irradiating the entire surface of the resist pattern with ultraviolet rays after heat treatment at a high temperature.

The positive photoresist used in the method of the present invention is not particularly limited and can be used as long as it has a positive effect, but a preferred positive photoresist is mainly composed of a photosensitive substance and a film-forming substance. It is something. This photosensitive material is prepared by partially or completely esterifying a quinonediazide group-containing compound, for example, a sulfonic acid of a quinonediazide such as orthobenzoquinonediazide, orthonaphthoquinonediazide, orthoanthraquinonediazide, and a compound having a phenolic hydroxyl group or an amine group, or Examples include partially or completely amidated ones.

Examples of compounds having a phenolic hydroxyl group or amino group include polyhydroxybenzophenones such as 2,3,4-)lyhydroxypenzophenone and 2,2',4,4'-tetrahydroxybenzophenone.

Or alkyl gallate, aryl gallate, phenol, p-methoxyphenol, dimethylphenol,
Hydroquinone, bisphenol A1 naphthol, pyrocatechol, pyrogallol, pyrogallol monomethyl ether, pyrogallol-1,3-dimethyl ether, gallic acid, gallic acid esterified or etherified with some hydroxyl groups remaining.

Examples include aniline and p-aminodiphenylamine.

On the other hand, film-forming substances include, for example, novolak resins obtained from phenol, cresol, etc. and aldehydes, acrylic resins, polyvinyl alcohol, polyvinyl alkyl ethers, copolymers of styrene and acrylic acid, hydroxystyrene nopolymers, polyvinyl Hydroxybenzoate.

Examples include alkali-soluble resins such as polyvinylhydroxybenzal.

The positive photoresist used in the present invention is advantageously used in the form of a solution by dissolving the photosensitive material and film-forming material in a suitable solvent.

Examples of such solvents include ketones such as acetone, methyl ethyl ketone, cyclohexanone, and inamyl ketone; monomethyl ether, monoethyl ether, monopropyl ether of ethylene glycol, ethylene glycol monoacetate, diethylene glycol, or hashiethylene glycol monoacetate; Examples include polyhydric alcohols such as motubutyl ether or hamonophenyl ether, cyclic ethers such as the hisso derivative nidioxane, and esters such as methyl acetate, ethyl acetate, and butyl acetate. These may be used alone or in combination of two or more.

In the method of the present invention, the positive photoresist containing an ultraviolet absorber is used.

As this ultraviolet absorber, azo dyes, quinoline dyes, aminoketone dyes, anthraquinone dyes, etc. can be used, but particularly preferred ultraviolet absorbers include p-N, N-dimethylamino-p'-ethoxyazobenzene. , 4-hydroxy-4'-dimethylaminoazobenzene, 2,4-dihydroxy-41-diethylaminoazobenzene, 2,4-dihydroxyazobenzene, 2
, 4-dihydroxy-4'-nitroazobenzene,
4-(3-Me)
'-methylbenzene), 8-hydroxynaphthalene-1
-azo(2',4'-dimethylbenzene), 1-(4'
-(2-Methyl-1-phenylazo)-2'-methylphenyla7''] -]2-hydroxybenzene1-
(4'-Phenyl7''-1'-Phenyl7 So)-2
-Hydroxynaphthalene and the like.

These ultraviolet absorbers may be used alone or in combination of two or more, and the amount thereof is usually 0.1 to 20% by weight based on the weight of the positive photoresist.
It is preferably selected in a range of 0.1 to 15% by weight. If this amount is less than 0.1% by weight, the halation prevention effect will not be effectively exhibited, and if it exceeds 20% by weight, crystals of the ultraviolet absorber will precipitate in the photoresist film, resulting in a tendency to form a heterogeneous phase. I don't like it because it is.

To give one example of a preferred method for forming a resist pattern in the method of the present invention, first, a positive photoresist containing the above-mentioned ultraviolet absorber is coated on a substrate, and after drying, a low pressure mercury lamp, a high pressure mercury lamp, an ultra-high pressure mercury lamp, Using an arc lamp, a xenon lamp, etc., actinic light is selectively irradiated through a desired mask, or irradiation is performed while scanning an electron beam. Next, using a developer, for example, a weakly alkaline aqueous solution such as a sodium hydroxide aqueous solution, a tetramethylammonium hydroxide aqueous solution, or a trimethyl(2-hydroxyethyl)ammonium hydroxide aqueous solution,
A resist pattern is formed on the substrate by dissolving and removing the portion that has been solubilized by irradiation with actinic light.

In the method of the present invention, after a resist pattern is formed on a substrate in this manner, heat treatment is performed at a temperature that does not cause deformation of the resist pattern. The processing temperature is usually in the range of 80 to 120°C. Generally, at temperatures below 80°C, it is not possible to sufficiently remove the evaporated components remaining in the resist pattern layer, and at temperatures above 120°C, the resist pattern melts and sag, resulting in a hollow shape. This is undesirable because it deforms. This temperature range is a guideline and is not limited, and depending on the type of positive photoresist used, the temperature range of the heat treatment can be wider.

Further, the method of this heat treatment is not particularly limited as long as it is a method that can heat the resist pattern layer, and for example, a hot air circulation method, a hot plate method, a far-infrared lamp method, etc. can be used. Further, the heat treatment time cannot be particularly limited because it depends on the type of photoresist used and the heating means used, but in a heating temperature range of 80 to 120°C, a treatment time of 0.5 to 5 minutes is usually sufficient.

In the method of the present invention, after the resist pattern is heat-treated in this way, the entire surface of the pattern is irradiated with ultraviolet rays. This ultraviolet irradiation may be carried out immediately after the heat treatment, or may be carried out after the resist pattern has been cooled to room temperature. Examples of ultraviolet lamps used include low-pressure mercury lamps,
Examples include high-pressure mercury lamps, ultra-high-pressure mercury lamps, xenon-mercury lamps, etc., but lamps having maximum intensity in the wavelength range of 300 to 400 nm are particularly preferred, and therefore ultra-high-pressure mercury lamps are preferred.

The ultraviolet irradiation time cannot be particularly limited because it depends on the intensity of the ultraviolet generating lamp used, but care must be taken because if the irradiation time is too long, wrinkles will easily occur in the resist pattern.

However, this can be solved by adjusting the amount of ultraviolet irradiation, but in this case, the relationship between the wavelength and the amount of irradiation becomes important. Specifically, when using an ultra-high pressure mercury lamp, 253.7 nm The ratio of the respective irradiation doses to the 365 nm resist pattern is 1:20 to 1.
: 100, preferably in the range of 1:30 to 1:60, and it is desirable that the irradiation amount of 253.7 nm to the resist pattern be at least 150 mJ/cr/I or more.

In order to adjust the ultraviolet irradiation amount ratio in this way, an ultraviolet filter is usually used, and a quartz blue filter is particularly suitable for adjusting the ultraviolet ray irradiation amount ratio to the above-mentioned ratio. In addition, through such an ultraviolet filter, the irradiation amount of 253.7 nm is 150 mJ/cr/1.
Although it is desirable that the amount be above, this can be adjusted depending on the intensity and irradiation time of the ultraviolet generating lamp used. For example, using an ultra-high pressure mercury lamp as an ultraviolet generating lamp,
When the resist pattern is irradiated with ultraviolet rays through a quartz blue filter that adjusts the irradiation dose ratio of 3.7 nm and 365 nm to 1:50, tssmw is applied to 365 nm.
, with an ultra-high pressure mercury lamp having an intensity of 253.7
In order to obtain an irradiation dose of 150 mJ/all in nm, irradiation for at least 45 seconds is required.

Effects of the Invention According to the resist pattern stabilization method of the present invention, thermal stability is significantly improved by sequentially and separately applying heat treatment and ultraviolet irradiation treatment to the resist pattern after development.
In addition, it is possible to obtain a resist pattern with extremely high reproducibility without the occurrence of wrinkles on the surface, and by adjusting the amount of ultraviolet rays to a specific ratio in the ultraviolet irradiation treatment, it is possible to avoid wrinkles. The prevention effect can be enhanced.

Since the method of the present invention has such excellent effects, it is an extremely effective method for preparing semiconductor devices such as VLSIs.

Example Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Cresol novolac resin and naphthoquinonediazide
0FPR-800, a positive photoresist containing an ester condensate of 5-sulfonic acid and 2,3,4-trihydroxybenzophenone (manufactured by Tokyo Ohka Kogyo Co., Ltd.)
p -N, N- as an ultraviolet absorber with respect to the solid content of
A solution of 5 weight dimethylamino-p'-ethoxyazobenceph was added and coated on a 4-inch silicon wafer using a TR-5111 type resist coater (manufactured by Tammo Co., Ltd.).
After applying it using
A coating film with a thickness of 1.30 μm was formed. Next, after exposure using a wafer stepper DSW-4800 (manufactured by OA) through a test chart mask (Dainippon Printing Co., Ltd.), a 2.38 weight percent tetramethylammonium hydroxide aqueous solution was used. , immersion development was performed at 23° C. for 1 minute, followed by rinsing with pure water for 1 minute to form a resist pattern on the wafer.

Next, this wafer was placed on a 90°C hot plate for 90°C.
The resist pattern was placed for a second and then heat-treated.

Perform the same operation as above to create 6 samples, 365
5 with maximum intensity (tss mW/ad) at nm
The entire surface of the resist pattern was irradiated with ultraviolet rays for different irradiation times using an ultra-high pressure mercury lamp, and then subjected to beta heating at 170° C. for 5 minutes using a pileup open (Thomas Scientific Instruments Co., Ltd.). The obtained resist pattern was observed and the results are shown in the attached table.

Example 2 When performing ultraviolet irradiation, 253.7 nm in the ultra-high pressure mercury lamp used in Example 1 was used as an ultraviolet filter.
A resist pattern was obtained by processing in the same manner as in Example 1, except that the ultraviolet ray irradiation treatment was performed through a quartz blue filter in which the ratio of the amount of ultraviolet rays and 365 nm was 1:50.

The observation results of this resist pattern are shown in the attached table.

Comparative Example A resist pattern was obtained in exactly the same manner as in Example 1, except that the heat treatment using a hot plate after development was not performed. The observation results of this resist pattern are shown in the attached table.

Claims (1)

[Claims] 1 A photosensitive layer made of a positive photoresist containing an ultraviolet absorber is subjected to the required image-forming exposure, then developed to form a resist pattern, and then heated at a temperature that does not cause deformation of the resist pattern. A method for stabilizing a positive photoresist pattern, comprising irradiating the entire surface of the resist pattern with ultraviolet rays.