JPS6219052B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a pattern forming method that uses a vapor phase graft polymerization method to directly form a resist pattern for high-precision microfabrication on a substrate to be processed. Conventionally, in the production of ICs and LSIs, the substrate to be processed is coated with an organic composition such as a polymer compound called a resist, and a latent image is formed on the resist by irradiating it with high-energy radiation in a pattern, which is then developed. After forming a patterned resist film, the substrate to be processed is immersed in a corrosive liquid to chemically etch the parts of the substrate not covered by the resist, and the resist is peeled off to form the desired pattern. Wet methods of forming on substrates have been used. However, with the miniaturization of LSI devices in recent years, the wet method described above cannot achieve sufficient processing accuracy due to side etching, and dry etching methods such as etching using high-frequency plasma of gases such as carbon tetrafluoride and carbon tetrachloride are now being used. It has come to be used. For this reason, resist materials used for pattern formation are required to have high sensitivity and resolution to energy rays, as well as high resistance to dry etching. However, sensitivity, resolution, and dry etching resistance tend to be contradictory, and no material has been found that satisfies all of them. Therefore, Harada et al.
The base material coated on the substrate to be processed is irradiated with high-energy rays to create active points, and a monomer gas is introduced onto this film to selectively graft polymerize to the irradiated areas of the pattern, resulting in direct polymerization without the need for development. We also propose a method of forming patterns using a dry method. However, even in this case, in order to thicken the base material layer and create a resist pattern with a good shape ratio, it is necessary to thicken the graft polymer film, which increases the amount of high-energy radiation irradiated to the pattern area, and also increases the graft polymer film thickness. It is also necessary to increase the processing time. This lengthens the substrate processing time and becomes extremely uneconomical in semiconductor device manufacturing. In addition, since graft polymerization has no directionality,
Grafting for a long time increases not only the film thickness but also the line width, resulting in a decrease in resolution. The purpose of the present invention is to perform graft polymerization in order to significantly improve the resolution, pattern shape, and dry etching resistance of the pattern in a method of obtaining a desired pattern by graft polymerization on a substrate film irradiated with high-energy rays. An object of the present invention is to provide an improved method for a base film that can be used. That is, to summarize the present invention, the present invention involves forming a film made of a base material that generates active points capable of initiating addition polymerization by irradiation with high-energy rays on a substrate, and then irradiating the film with high-energy rays in a pattern. The irradiated film is selectively graft-polymerized in the patterned irradiated areas in a monomer gas atmosphere to form a pattern-shaped graft polymer film, and this graft polymer film is used as a mask to form fine particles on the base film by etching. In the method of forming a pattern, a two-layer base material layer is used, the lower layer is made of an organic polymer material film, and the upper layer is made of a silicon oxide film, and a graft polymer in the shape of the irradiation pattern is deposited on the upper silicon oxide film. A film is formed, and using this graft polymer film as a mask, the silicon oxide film not covered by the graft polymer film is etched away, and then the organic polymer material film in the area not covered by the silicon oxide film is removed. The present invention relates to a pattern forming method characterized by etching and removing. The most important point in the present invention is that the silicon oxide film generates active sites capable of addition polymerization by irradiation with high-energy rays, and that it can be dry etched using oxygen gas, which has a high etching rate for organic polymer material films. It was discovered that there was no etching at all. As a result, even if a very thin silicon oxide film is used, a pattern can be transferred to a relatively thick organic polymer material film, so the graft polymer film used as a mask necessary for etching the silicon oxide film is also thin. good. Therefore, it not only improves the decrease in resolution caused by increasing the thickness of the graft polymer film, but also reduces the amount of high-energy ray irradiation, which leads to higher sensitivity, and is also effective in shortening the graft polymerization processing time. . Hereinafter, the present invention will be specifically described based on the accompanying drawings. The drawings are process diagrams showing a specific example of pattern formation according to the present invention. Step (a) is the application of an organic polymer material film, (b) is the deposition of a silicon oxide film, (c) is the irradiation of high-energy rays, and (d) is the introduction of a monomer gas capable of addition polymerization. (e) Etching of silicon oxide film using the graft polymer film pattern as a mask, (f)
(g) shows etching of the substrate to be processed, and (g') shows doping of the substrate to be processed. Therefore, 1 is a substrate to be processed, 2 is an organic polymer material film, 3 is a silicon oxide film, 4 is a high energy beam, 5 is a monomer gas for graft polymer,
6 means the graft polymer film, and 7 means the dopant. First, a relatively thick organic polymer material film 2 of about 1 μm is applied onto the substrate 1 to be processed (step a). A relatively thin silicon oxide film 3 of about 75 nm or less is formed on this (step b). This silicon oxide film can be formed using a CVD method (Chemical Vapor Deposition method) in which SiH ₄ is oxidized in a gas phase and deposited on the organic polymer material film, a reactive sputtering method targeting silicon, or A high frequency sputtering method, a vapor deposition method using fused quartz as a raw material using an electron beam evaporator, a method of applying a solution of a silicon compound dissolved in alcohol, and then forming a silicon oxide film, etc. are used. The substrate having the two-layer film thus obtained is irradiated with high-energy rays 4 in an arbitrary pattern (step c).
Electron beams, X-rays, ion beams, and far ultraviolet rays can be used as high-energy beams. The thus irradiated substrate is placed in an atmosphere of monomer gas 5 capable of addition polymerization without being brought into contact with air, and the irradiated areas are selectively grafted to form a graft pattern (step d). The graft polymer film 6 can be thickened by increasing the irradiation dose or by lengthening the graft polymerization time, but if it is deposited to a thickness sufficient to remove the silicon oxide film on the base film by dry etching. good. For example, if the silicon oxide film is 75 nm thick, a graft polymer film of about 150 nm is sufficient. Next, using this graft polymer film pattern as a mask, the area not covered by the graft polymer film, that is, the unirradiated area of the silicon oxide film is removed by dry etching (step e). As an etching gas, a gas which etches a silicon oxide film more quickly than a graft polymer film is usually used, such as CF ₄ or CHF ₃ , or a gas prepared by adding H ₂ thereto. Using the thus obtained patterned silicon oxide film as a mask, the organic polymer material film in the unirradiated area is removed by dry etching (step f). The etching gas used here is usually oxygen, which etches silicon oxide films more slowly than organic polymer material films. In this way, a relatively thick organic polymer material film can be processed into a desired pattern using a thin graft polymer film. After that, the patterned organic polymer material film is used to perform etching or doping on the underlying substrate to be processed (step g,
g′). As the monomer gas to be graft-polymerized, organic monomers capable of addition polymerization and gasification, such as styrene, divinylbenzene, vinyltoluene, acrylonitrile, etc., can be used. In addition, the organic polymer material film used as the lower layer of the two-layer base film can be selected from any material in principle as long as it does not change in quality when the silicon oxide film is applied. In other words, materials with high dry etching properties against reactive gases other than oxygen gas and with a low possibility of contamination of impurities into the substrate to be processed are preferable. Polyimide acids, polystyrene and its derivatives, polyparaxylylene, copolymers of acrylic acid or methacrylic acid and phenyl acrylate, phenyl methacrylate, naphthyl acrylate, naphthyl methacrylate, etc. are coated and then heat treated (meth)acrylic. Acid-aromatic (meth)acrylate copolymer anhydride, AZ-based resist, etc. can be used. EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples. Example 1 Polyamic acid (Trainice #2000 manufactured by Toray Industries, Ltd.) is applied by spin coating onto a thermally oxidized silicon substrate to form a 1.2 μm thick film. 1.0 by heating this film at 300℃ for 1 hour.
A polyimide film with a thickness of μm was obtained. A 75 nm thick silicon oxide was deposited thereon using the SiH ₄ oxidation method using a CVD reactor. The adhesion conditions are _N2
Gases were flowed at 6000 c.c./min, O ₂ at 250 c.c./min, and SiH ₄ at 40 c.c./min, and the substrate temperature was 300° C. for 1 minute. Next, using an electron beam exposure device, a line pattern with a width of 5 μm was irradiated with various exposure doses at an accelerating voltage of 20 KV. Then 10 ^-3 without contact with air
The substrate was moved to a vacuum atmosphere of 3 Torr, styrene gas purified and degassed at a gas pressure of 3 Torr was introduced, and the mixture was left to stand for 1 hour to perform graft polymerization on the irradiated area. As a result of microscopic observation, a uniform and glossy polystyrene graft polymer film was formed in the irradiated area, but no graft polymer film was observed in the unirradiated area. The amount of electron beam irradiation required to obtain a graft polymer film with a thickness of approximately 0.15 μm is approximately 75 μm.
It was C/ ^cm2 . After heating this sample in air at 150°C for 30 minutes, the silicon oxide film not covered by the graft polymer film was reactively sputter etched using carbon tetrafluoride gas to which 10% hydrogen gas was added. It was removed by The reactive sputter etching ratio of the styrene graft polymer film and silicon oxide film using the gas is approximately 1:2, and a 75 nm silicon oxide film can be sufficiently etched away by a 150 nm thick styrene graft polymer film. It was possible.
The polyimide regions not covered by the silicon oxide film were then removed by reactive sputter etching using oxygen gas. The sputter etching speed ratio of polyimide and silicon oxide at 0.03 torr pressure and oxygen gas flow rate of 5 c.c./min is more than 100:1 and 1.0 μm
Even after completely etching the thick polyimide film, there was almost no reduction in the silicon oxide film in the irradiated area. Next, a silicon oxide pattern with a depth of 1 μm was fabricated by reactive sputter etching using 10% hydrogenated carbon tetrafluoride. Examples 2 to 5 Similar to Example 1, on a thermally oxidized silicon substrate
A 1.0 μm thick polyimide film and a 75 nm thick silicon oxide film were formed and exposed under the same conditions. Thereafter, the samples were placed in a vacuum atmosphere of 10 ^-3 Torr without contact with each other, and the polymerizable monomer gases for each sample were divinylbenzene (Example 2), acrylonitrile (Example 3), and maleimide (Example 4).
When phenyl acrylate (Example 5) was introduced at a gas pressure of 3 torr and allowed to stand for 1 hour to carry out graft polymerization, a graft polymer film was formed only in the irradiated areas in all cases. Table 1 shows the amount of electron beam irradiation required to make the graft polymer film thickness 150 nm.

[Table] Examples 6 to 9 An ethyl cellosolve acetate solution of phenyl methacrylate and methacrylic acid copolymer (phenyl methacrylate content 65% weight average molecular weight 200,000) was applied to a thickness of 1.2 μm on a thermally oxidized silicon substrate. Heated in air at 250°C for 30 minutes. On top of this
Silicon oxide films were formed to a thickness of 75 nm by CVD using SiH ₄ (Example 6), reactive sputtering (Example 7), high-frequency sputtering (Example 8), and coating with a silicon compound alcohol solution (Example 9). It was covered with Thereafter, a silicon oxide pattern was obtained in the same manner as in Example 1. Table 2 shows the conditions for forming the silicon oxide film and the amount of electron beam irradiation required to form the graft polymer film.

[Table] Examples 10 to 12 A base material was prepared in the same manner as in Example 1, and a Cu-L wire (13.3 Å) was
Thermal oxidation was carried out in the same manner as in Example 1 by irradiating with radiation (Example 10), deep ultraviolet rays from a 500W Xe-Hg lamp (Example 11), or ion beam from a liquid Ga-ion source (Example 12). A silicon pattern was formed. Table 3 shows the irradiation dose at which the graft polymer film thickness was 150 nm with a graft polymerization time of 1 hour.

[Table] Example 13 Same conditions as Example 1, pattern width only 0.5μ
Exposure was performed by changing the thickness of the film to light of m, 1 μm, and 2 μm. Table 4 shows the amount of electron beam irradiation and the line width of the graft polymer film at this time.

[Table] As explained above, by forming the base material that generates active points capable of addition polymerization by high-energy ray irradiation into a two-layer structure, and using an organic polymer material film as the lower layer and a silicon oxide film as the upper layer, This method has the advantage that a pattern with high shape ratio and resolution can be formed with a small amount of radiation without increasing the thickness of the graft polymer film.

[Brief explanation of the drawing]

The drawings are process diagrams showing a specific example of pattern formation according to the present invention. 1: Processed substrate, 2: Organic polymer material film, 3:
Silicon oxide film, 4: high energy beam, 5: monomer gas for graft polymerization, 6: graft polymer film, 7: dopant.

Claims (1)

[Claims] 1 A film made of a base material that generates active points capable of initiating addition polymerization by irradiation with high-energy rays is formed on a substrate, and after irradiating the film with high-energy rays in a pattern, the irradiated film is placed in a monomer gas atmosphere. In this method, a pattern-shaped graft polymer film is formed by selectively graft polymerizing the pattern irradiated area, and a fine pattern is formed on the base film by etching using this graft polymer film as a mask. Using a two-layer base film consisting of a molecular material film and an upper layer consisting of a silicon oxide film, a graft polymer film in the shape of an irradiation pattern is formed on the upper silicon oxide film, and this graft polymer film is Pattern formation characterized by etching and removing the silicon oxide film that is not covered with the graft polymer film as a mask, and further etching and removing the organic polymer material film in the area that is not covered with the silicon oxide film. Law.