JPS6286823A - Formation of fine pattern - Google Patents

Abstract

PURPOSE:To form a fine pattern of submicron order by irradiating the whole surface of a lower positive type photo resist layer formed on a substrate with a great quantity of ultraviolet rays. CONSTITUTION:A positive type photo resist layer A is formed more thickly than the thickness of a step difference on a substrate which has the step difference and the whole surface of the resist layer A is irradiated with ultraviolet rays. The required quantity of radiation of ultraviolet rays is 1,000mJ/cm<2> or more. A positive type photo resist layer is provided on the resist layer A and then, the upper resist layer is patterned by the selective irradiation of active beam of light and development. The exposed resist layer A is dry-etched by using oxygen gas. This forms a fine pattern of submicron order.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for forming fine patterns. More specifically, the present invention relates to a method for forming fine patterns using a multilayer resist method with a two-layer resist structure, which is effective for processing submicron-order substrates with steps in the manufacture of semiconductor devices.

Conventional technology In recent years, in the semiconductor industry, industrial computers,
Demand for office automation, personal computers, etc. is expanding dramatically, and the technology continues to develop rapidly. Along with this, semiconductor devices are becoming denser and more integrated, and the formation of fine patterns is also progressing. , microfabrication with a pattern width on the order of submicrons is required. Currently, pattern formation in the manufacture of semiconductor devices is performed by photolithography, and the photoresists used for this are now mainly positive-type with high resolution, replacing the negative-type photoresists that were mainstream until now. As a result, the pattern width is 1
Microfabrication of ~2 μm is now being performed.

However, in the manufacture of semiconductor devices, substrates are usually subjected to multiple photolithography and etching steps, which creates steps on the substrate, and a positive photoresist is applied to the substrate with such steps to form a pattern. When forming a photoresist, there are problems such as non-uniformity of the photoresist coating thickness due to the step difference in the substrate, scattering of actinic rays during exposure, and a shift in focus, and as a result, the desired resolution cannot be obtained. Ta.

Therefore, as a means to overcome these drawbacks, a pattern forming method using a multilayer resist method has been proposed. This multilayer resist method involves forming an organic polymer layer on a substrate as a lower resist layer, and then forming a thin photoresist layer on top of this as an upper resist layer, in order to fill in the steps and flatten the substrate. After this photoresist layer is patterned by a conventional method, the exposed lower resist layer is subjected to a dry etching process using oxygen gas, thereby obtaining the entire fine pattern.

In this multilayer resist method, the lower resist layer is dry-etched by making full use of the oxygen plasma resistance of the upper resist layer, so the resist used for the upper layer has relatively high resistance compared to negative type resists. Positive photoresists with high oxygen plasma properties are preferred, and positive photoresists containing silicon are particularly preferred because of their excellent oxygen plasma resistance.

Furthermore, in this multilayer resist method, a combination is required in which the lower resist layer formed on the substrate and the upper resist layer directly provided thereon do not change in quality at their contact surfaces. As the resist used for the lower layer, it is known that positive photoresists using imide resins and phenol novolak resins are effective because of their high plasma resistance. However, when a positive photoresist is used as the upper layer resist, this material and the imide resin form a mixed layer at the contact surface, and the positive photoresist is soluble, resulting in a multilayer resist structure. As a result, a problem arises in that the desired resolution cannot be obtained.

This positive photoresist and multilayer resist method are technologies that can respond to the rapidly progressing miniaturization of processing dimensions, so the development of a method to effectively use positive photoresist as the upper layer resist in the multilayer resist method is necessary. This is extremely important for the development of the semiconductor industry.

Problems to be Solved by the Invention Under these circumstances, the purpose of the present invention is to solve the problem that even if positive photoresists are used for the upper and lower layers in a multilayer resist method with a two-layer resist structure, The object of the present invention is to provide a method capable of forming fine patterns on the order of submicrons without causing deterioration.

Means for Solving the Problems The inventors of the present invention have conducted extensive research to achieve the above object, and have found that by irradiating a large amount of ultraviolet rays to the lower positive photoresist layer formed on the substrate, It was discovered that the photoresist layer was insoluble in organic solvents and alkaline aqueous solutions, thereby achieving the objective, and based on this knowledge, the present invention was completed.

That is, in the present invention, a positive photoresist layer is formed thicker than the step on a substrate having steps, the entire surface of the photoresist layer is irradiated with ultraviolet rays, a further positive photoresist layer is provided on top of the photoresist layer, and then an activated photoresist layer is formed. Provided is a method for forming a fine pattern, which comprises patterning an upper resist layer by selectively irradiating it with light and developing it, and then dry etching the exposed lower resist layer using oxygen gas. It is something to do.

In the method of the present invention, there are no particular restrictions on the positive photoresist used for the lower resist layer, and most can be used as long as it has a positive effect, but preferred positive photoresists include photosensitive The sulfo/acid of quinonediazides such as orthobenzoquinonediazide, orthonaphthoquinonediazide, orthoanthraquinonediazide and a compound having a phenolic hydroxyl group or amine group are partially or completely esterified, or partially or completely Examples include 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 gallates. Aryl gallate, phenol, p-methoxyphenol, dimethylphenol, hydroquinone, bisphenol A1 naphthol, pyrocatechol, pyrogallol, pyrogallol monomethyl ether, pyrogallol-1,3-dimethyl ether, gallic acid, esterification or etherification with some hydroxyl groups remaining gallic acid,
Examples include aniline and p-aminodiphenylamine.

In addition, examples of film-forming substances to be added to the positive photoresist include novolac resins obtained from phenol, cresol, etc. and aldehydes, acrylic resins,
polyvinyl alcohol, polyvinyl alkyl ether,
Alkali-soluble resins such as copolymers of styrene and acrylic acid, polymers of hydroxystyrene, polyvinylhydroxybenzoate, and polyvinylhydroxybenzal are effective.

The positive photoresist is advantageously used in the form of a solution, in which the photosensitive material and film-forming material are dissolved in a suitable solvent.

Examples of such solvents include ketones such as acetone, methyl ethyl ketone, cyclohexanone, isoamyl ketone; monomethyl ether, monoethyl ether, monopropyl ether, motubutyl ether of ethylene glycol, ethylene glycol monoacetate, diethylene glycol or diethylene glycol monoacetate. or polyhydric alcohols such as monophenyl ether and their derivatives; cyclic ethers such as dioxane; 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 is applied as a lower resist onto a substrate having steps, using a spinner or the like for the purpose of flattening, dried, and then irradiated with ultraviolet rays over the entire surface to remove organic solvent and alkali. A lower resist layer that is insoluble in the aqueous solution is formed. At this time, the amount of UV irradiation was 1000 mJ
/crd or more is required, and if the irradiation amount is less than this, it will not become completely insoluble in organic solvents and alkaline aqueous solutions, which is not preferable. Regarding ultraviolet light generating lamps,
There is no particular restriction IIi as long as it can irradiate ultraviolet rays of looOmJ/d or more, and for example, a low-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, an arc lamp, a xenon lamp, etc. can be used.

Since the amount of UV irradiation has the following relationship, from this formula, the amount of UV irradiation is 1
The intensity of the lamp and the irradiation time can be appropriately selected so that the value is 0100O/Ctf1 or more.

In this way, after the lower resist layer is made insoluble in organic solvents and alkaline aqueous solutions by irradiation with ultraviolet rays, a positive photoresist layer is provided thereon as an upper resist layer. As the positive photoresist used here, the positive photoresist used for the lower resist layer described above can be used in the same way, but since this upper resist layer is required to have excellent oxygen plasma resistance, especially Silicon-containing positive photoresists are preferred. Examples of such substances include p-trimethylsilylphenol and phenol, p-trimethylsilylphenol and cresol, p-tri(trimethylsiloxy)silylphenol and cresol, trimethylphenylsilane and phenol, and dimethyldi(4-hydroxyphenyl)silane and phenol. , a condensate of dimethyldi(4-hydroxyphenyl)silane and cresol, a condensate of dimethyldiphenylsilane and cresol, etc., and formalin, and a quinonediazide group-containing compound. Since positive photoresists have high oxygen plasma resistance, silicon-containing positive photoresists other than those mentioned above can also be used.

In the method of the present invention, this positive photoresist is used as an upper resist layer and is coated with a spin coater or the like on the lower resist layer that has been irradiated with ultraviolet rays, and after drying, the quinonediazide group-containing compound is exposed to light and becomes solubilized. Selectively irradiate active light from a light source such as a low-pressure mercury lamp, high-pressure mercury lamp, ultra-high-pressure mercury lamp, arc lamp, or xenon lamp through a desired mask, or scan an electron beam. irradiate while Next, a developer,
For example, 1 to 2 mw of sodium hydroxide aqueous solution, tetramethylammonium hydroxide aqueous solution, trimethyl (2 mw)
A resist pattern is formed on the underlying resist layer by dissolving and removing the portion solubilized by exposure with an alkaline aqueous solution such as -hydroxyethyl) ammonium hydroxide aqueous solution. Next, by etching the exposed lower resist layer by dry etching using oxygen gas, such as plasma etching or reactive ion etching, it is possible to form a fine pattern with high dimensional accuracy that is faithful to the mask pattern. can.

The substrates with steps used in the method of the present invention include substrates that themselves have irregularities, such as silicon wafers that have been etched multiple times, as well as substrates that have metals such as aluminum deposited on them. It also includes substrates whose surfaces have irregularities.

Effects of the Invention The fine pattern forming method of the present invention is a method using a multilayer resist method with a two-layer resist structure, which is known as a pattern forming method with high dimensional accuracy. By irradiating the entire positive photoresist layer with a large amount of ultraviolet rays, the photoresist layer becomes insoluble in organic bath agents and alkaline aqueous solutions.
Even if a positive-type photoresist layer is further provided as an upper resist layer on top of that, no deterioration occurs at the contact surface. Therefore, a high-resolution positive-type photoresist can be used in the multilayer resist method, and submicron A fine 11a pattern of the order of magnitude can be easily formed.

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

Example 1 TR-40 was applied to the surface of a substrate on which aluminum was deposited on a 4-inch silicon wafer with a step of O, am.
00 type resist coater (manufactured by Tatsumo Co., Ltd.) 1r: using
0FPR-soo (manufactured by Tokyo Ohka Kogyo Co., Ltd.), which is a positive photoresist containing a cresol novolac resin and an ester condensate of 7-toquinonediazide-5-sulfonic acid and 2.3.4-)lyhydroxypenzophenone 436 nr as a light absorber for this solid content.
p-N,N-dimethylamino-p'- with absorption at c
25μ of ethoxyazobenzene added 5% by weight
Coated to a thickness of 90.m at 110°C. After baking using a hot plate for seconds, the temperature was 185mW/365℃.
The entire surface was irradiated with ultraviolet rays for 2 minutes using a 5 KH ultra-high pressure mercury lamp with an intensity of 22,200 m J
/cr&).

Next, a silicon-containing positive photoresist solution was applied thereon using the resist goater, and baked at 110° C. for 90 seconds using a hot plate to obtain a film thickness of 1.3 μm. This silicon-containing positive photoresist solution is a silicon-containing phenol novolak resin obtained by formalin condensation of 4 moles of trimethylsilylphenol and 17 rutophenols.
00 parts by weight and naphthoquinone-1,2-diazide-5-
25 parts by weight of a condensate of sulfonic acid and 2.3.4-trihydroxybenzophenone was dissolved in 300 parts by weight of ethylene glycol monoethyl ether acetate, and filtered using a membrane filter with 0.2 μm pores. It was prepared by

Next, using a reduction projection exposure device 1505 Ga A type wafer stepper (Nippon Kogaku Kogyo Co., Ltd. ff), exposure was performed through a test chart mask (manufactured by Inu Nippon Printing Co., Ltd.), and then 2.38 weight percent tetramethylammonium hydroxy The film was developed in an aqueous solution at 23° C. for 30 seconds. As a result, a silicon-containing positive photoresist pattern H1o with a sharp cross-sectional shape of s μm was obtained.

Furthermore, a parallel plate plasma etching device OAPM-
400 (manufactured by Tokyo Ohka Kogyo Co., Ltd.) at a pressure of 10 tn.
Torr, oxygen gas flow! 10cc/min,
When the lower resist layer was etched by reactive ion etching under the conditions of RF output of 50 W and processing temperature of 25°C, a 0.8 μm pattern faithful to the upper resist pattern was obtained regardless of the unevenness of the underlying substrate. Ta.

Comparative Example In the example, the same treatment as in the example was performed except that the underlying positive photoresist layer was not irradiated with ultraviolet rays.

As a result, since the lower resist layer was not irradiated with ultraviolet rays, the lower resist layer melted and flowed away when the upper resist layer was coated, and the lower resist layer did not appear in the center of the wafer. No trace remained, and the resist pattern after exposure and development could not form uniform lines due to unevenness caused by steps.

Claims (1)

[Claims] 1. On a substrate having steps, a positive photoresist layer is formed to be thicker than the steps, the entire surface of the photoresist layer is irradiated with ultraviolet rays, and then a positive photoresist layer is provided on top of the photoresist layer, and then an activated photoresist layer is formed. A method for forming a fine pattern, which comprises patterning an upper resist layer by selectively irradiating a light beam and performing a development process, and then dry etching the exposed lower resist layer using oxygen gas. 2. The method according to claim 1, wherein the upper positive photoresist layer is made of a silicon-containing positive photoresist.