JPS5886726A - Forming method for pattern - Google Patents

Abstract

PURPOSE:To form a resist pattern for fine processing on a substrate to be processed, by making use of a vapor-phase graft copolymerization method for a macromolecular material. CONSTITUTION:A chemical substance, such as polymethyl methacrylate, which is known as a conventional radical initiator and capable of producing a radical even with the application of high-energy beams, or a macromolecular material similar thereto, is mixed with a radical initiator, and ultraviolet rays are applied thereto in an ambience of a gas produced from the mixture solution of a monomer capable of vinyl polymerization, such as methyl methacrylate, and of an initiator, such as propionaldehyde, of about 0.5-4wt% to the monomer. Thereby a vapor-phase graft copolymerization film is formed selectively on the part of a base film whereon the beams are applied. By this constitution, the swelling due to a developing solution is eliminated, the resolution is improved remarkably, and a resist pattern for fine processing can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pattern forming method in which an arbitrary resist pattern for high-precision microfabrication can be directly formed on a substrate to be processed using a dry method.

Conventionally, in the manufacture of ICs and LSIs, etc., a resist made of a polymer compound, etc. is applied onto the surface of the substrate to be processed to form a film, and this is then exposed to high-energy rays such as ultraviolet rays, far ultraviolet rays, X-rays, and electron beams. is irradiated to create a latent image by decomposing the polymer main chain (positive type) or inducing crosslinking between the polymer main chains (negative type), and in the development process that follows this step, the above irradiation 1. The pattern is visualized by utilizing the difference in dissolution rate in a developer between the decomposed or crosslinked portion and the non-irradiated portion, and the substrate to be processed is processed using these patterns.

Practical resist materials used in these processing processes must be highly sensitive to the high-energy beams used, and must also have high resolution in order to improve processing accuracy. However, since the developing process is always performed by immersion in an organic solvent or alkaline solution, it has the disadvantage that the pattern part swells in the developing solution and the resolution decreases, which is especially noticeable in negative-tone resists. This is a limiting factor for resolution.

On the other hand, as the integration of LSI etc. progresses and the size of the pattern formed on the surface of the substrate to be processed becomes finer, to about 2 μm or less, the processing of the substrate to be processed will no longer be done using the conventionally used corrosive liquid. In chemical etching, since the amount of undercut caused by isotropic etching cannot be ignored, dry etching using high frequency plasma of carbon tetrafluoride gas or carbon tetrachloride gas has come to be used. For this reason, the resist must have so-called dry etching resistance, since it is unlikely to be decomposed or deformed in these dry etching atmospheres. However, in order to achieve high sensitivity in positive resists, a molecular structure that is easily decomposed by high-energy irradiation is required, and sensitivity and dry etching resistance tend to be at odds with each other. Nothing has been achieved that satisfies the above.

In addition, in the conventional resist process, since the resist comes into contact with many solvents during synthesis, dissolution in a coating solvent, coating, and development, there are many opportunities for the resist to be contaminated with impurities. There were problems with the semiconductor process, which they disliked. Particularly, as the device size becomes ultra-fine, a small amount of impurity, such as a gate oxide film in a MOS process, cannot be removed and the device deteriorates.

Furthermore, in the conventional resist process, dust in the resist and in the process atmosphere directly affects the yield.
This method has drawbacks such as the need to perform precise filtration of the resist solution in a strictly controlled clean room.

The present invention was made in view of the current situation, and
The purpose is to solve the problems of the conventional methods and to provide a pattern forming system that can directly form any resist pattern for high-precision, fine-patterning on the surface of a substrate to be processed by a dry method.

To summarize the present invention, the pattern forming method of the present invention is as follows:
A film made of a base material that generates active points that can initiate addition polymerization by irradiation with high-energy rays is formed on a substrate, and after pattern irradiation of the film with high-energy rays, the irradiated film is pattern-irradiated in a monomer gas atmosphere. The method is characterized in that a graft polymer film having a pattern shape is formed by selectively graft polymerizing parts.

The present invention involves graft polymerization to active sites capable of initiating addition polymerization (i.e., bottomer radicals), which are generated by irradiating a generally known polymeric material with high-energy rays, in the gas phase of monomer gas. This method uses a vapor phase graft polymerization method and applies it to a resist pattern formation method for microfabrication.

As the base material in the present invention, any material that can efficiently generate the above-mentioned active points with high-energy rays can be used. However, as described later, when the purpose is a practical microfabrication process, It is desirable to have a material type that has a high etching rate in certain dry processing processes.

Such base materials include polymethyl methacrylate,
Polymeric materials such as polymethyl vinyl ketone, polyvinyl salt, polyvinylidene chloride, cellulose, polyacrylonitrile, and polyvinylidene fluoride, benzoyl peroxide, caprylyl peroxide, lauroyl peroxide, tertiary methyl perisobutyl Chemical substances that are known as ordinary radical initiators and can generate radicals even when irradiated with high-energy rays, such as di-tertiary butyl perphthalate, azobisin butyronitrile, and tetramethylthiuram disulfide, and the above-mentioned polymeric materials. A mixture of the above-mentioned radical initiator and the above-mentioned radical initiator can be applied, and by using such a mixture, the efficiency of radical generation can be improved, and as a result, the sensitivity can be increased.

Furthermore, vinyl-polymerizable monomers such as methyl methacrylate, methyl isopropenyl ketone, methyl vinyl ketone, and ethyl acrylate, and propionaldehyde, diacetyl, and isovaler in a weight ratio of about 0.5 to 3 to these monomers are further added. A gas phase polymer obtained by irradiation with ultraviolet light in a gas atmosphere generated from a mixed solution with an initiator such as an aldehyde can also be used as the base material in the present invention.

In the present invention, a film made of the above-mentioned base material is formed by a conventional coating method, and is irradiated with high-energy radiation in a pattern. As high-energy rays, electron beams, X-rays, deep ultraviolet rays, etc. can be used. When X-rays or far ultraviolet rays are used, turn irradiation can be performed in combination with a mask that absorbs them.

In the present invention, after the pattern irradiation, the irradiated film is selectively graft-polymerized in the irradiated areas in various monomer gas atmospheres.The monomer gas atmosphere that can initiate addition polymerization includes styrene, maleimide, divinylbenzene, etc. , N-vinylcarbazole, vinylferrocene, hinyltrichlorosilane, acrylonitrile, methyl methacrylate, etc. can be applied. When applying these, it is necessary to quickly remove oxygen by preventing the substrate film from coming into contact with oxygen after irradiation. After creating a vacuum atmosphere free from dust, the above monomer gas is introduced to give a power of about 3 mm+J/<-L, and is usually kept at room temperature for a predetermined period of time to carry out graft polymerization, resulting in a uniform glossy film. can be obtained.

After the graft polymerization film is formed, a desired pattern can be obtained by removing the base material film on which the graft polymerization film is not formed, which is the part that is not irradiated with high energy rays, by a normal plasma ashing method.

According to the present invention, by forming a graft polymer film pattern on the base film surface by vapor phase graft polymerization, the wet development process that is always used in the conventional resist process is no longer necessary, and the conventional resist process Swelling caused by the developer solution, which was a disadvantage of the previous method, is eliminated, and resolution can be significantly improved. In addition, as shown in the examples below, by using photo-vapor phase polymerization to form the base film, the entire resist process becomes a dry atmosphere, and only the vapor of the monomer solution becomes the supply source of the resist, which is different from conventional methods. This method is much more advantageous in preventing contamination of the resist and processed substrate by solvents and human handling.

On the other hand, in graft polymerization, a polymer chain grows from one active site, that is, a polymer radical, and the growth is stopped due to recombination of the polymer radicals. Therefore, by controlling the type of substrate, the type of monomer for graft polymerization, and the graft polymerization conditions, it is possible to reduce the irradiation high energy dose to the same graft polymerized film, that is, to increase the sensitivity. In general, polymers with aromatic rings or inorganic elements have a slow plasma ashing rate, whereas aliphatic polymers such as polymethyl methacrylate or polymethyl isopropenyl ketone, or their )/logen substituted products, have a low plasma ashing rate.
Plasma ashing speed is relatively fast. These trends are similar in other general dry etching methods.

In the present invention, the base film is made of a material with a fast plasma ashing rate, and the graft polymer film is made with a material with a slow plasma ashing rate, and after the graft polymer film pattern is formed, plasma aging is performed to remove the non-irradiated area. By removing the base material, a resist pattern similar to the conventional resist process is obtained.

However, even if dry etching of the substrate, which is generally performed after forming a resist pattern, is performed directly after forming a craft polymer film pattern, the desired dry etching process can be performed because the base film is quickly etched away.

The sensitivity of the resist according to the present invention is due to the graft polymerizability of the monomer, and the sensitivity of conventional resists is different from that of the conventional resist (positive type due to the ease of decomposition of the polymer main chain) or negative type due to the ease of crosslinking between the polymer main chains. ) is different from that which was caused by

Therefore, the conflicting phenomenon between sensitivity and dry etching resistance in conventional positive resists and the conflicting phenomenon between sensitivity and resolution in negative resists does not occur.

Next, the present invention will be explained with reference to the drawings. That is,
The drawings are process diagrams showing a specific example of the formation of a cross-turn according to the present invention, in which (a) shows the step of forming the base film of substrate-1, and (b) shows the process of forming the base film of (a). A step of irradiating a desired pattern area with high energy rays, (C) is a step of placing the irradiated base film of (b) in a monomer atmosphere to form a graft polymerized film, and (d) is a step of (a) and (b). and (c), in which reference numeral 1 represents the substrate, 2 represents the base film, 3 represents the high energy beam, 4 represents the monomer atmosphere, and 5 represents the graft polymerized film.

In carrying out the process, first, on a substrate 1 such as a silicon wafer whose surface has been thermally oxidized, a predetermined base material that generates active points that can initiate addition polymerization by irradiation with high-energy rays is applied, and a base film 2 is formed.
[(a) step], and then irradiating the desired pattern area of the base film 2 of (a) with high energy rays 3 such as electron beams, X-rays, and deep ultraviolet rays [(b) process]. In this step, active points capable of initiating addition polymerization are generated in the high-energy ray irradiated portion of the base film 2. Next, the irradiated base film obtained in (b) is exposed to a predetermined monomer atmosphere 4 to selectively graft-polymerize the pattern irradiated areas to form a pattern-shaped graft-polymerized film 5 [Step (C)] . Graft polymerization occurs at a portion where active sites capable of initiating addition polymerization are generated by irradiation with high-energy rays 3. After completing these steps and removing the monomer gas atmosphere, a desired graft polymer film pattern can be obtained [step (d)]. Although the base film 2 in the unirradiated area in (d) is removed by plasma ashing in the next step (not shown), the film thickness of the graft polymer film pattern in the irradiated area is not reduced at all by plasma ashing. It does not occur, or even if it does, it is only in very small amounts.

Next, the present invention will be explained with reference to examples, but the present invention is not limited to these examples in any way.

Example 1 Polymethyl methacrylate, polymethyl isopropenyl ketone, polyvinylidene fluoride, lauroyl peroxide, or polymethyl methacrylate containing 1% by weight lauroyl peroxide was uniformly coated on a silicon wafer whose surface had been thermally oxidized. A film with a thickness of about 0.2 μm was formed.

Each of these base films was irradiated with a line pattern having a width of approximately 5 μm using an ordinary electron beam irradiation device.

Further, each of these base films was irradiated with X-rays from a molybdenum target and far ultraviolet rays from a deuterium lamp, using a 2-μm-thick thin gold film with linear holes about 5 μm wide as a mask. In this case, the X-ray and deep ultraviolet irradiation were performed in a nitrogen atmosphere where the base film could not come into contact with oxygen.

After irradiating the base film with electron beams, X-rays, and far ultraviolet rays by the method explained above, avoid contact with oxygen.
After quickly transferring to an oxygen-free vacuum atmosphere, styrene gas was introduced to give a pressure of 3 mbar, and the mixture was left to stand for 1 hour to perform graft polymerization on the irradiated area. Regardless of the irradiation source and substrate, a uniformly glossy film with no surface defects in the irradiated area was obtained. Furthermore, no increase in film thickness was observed in non-irradiated areas.

When we measured the amount of increase in film thickness in the high-energy ray irradiated area, we found that
The amount of increase in film thickness increases as the amount of high-energy ray irradiation increases, but it varies from 0.6 to 1.0 depending on the graft polymerization conditions.
A saturation phenomenon of film thickness increase was observed above 0 μm.

Table 1 shows the amount of high-energy ray irradiation required for each high-energy ray to increase the film thickness of the irradiated part by 0.4 μm for each base material.

Table 1 Next, the graft polymer film pattern of each base material film-H produced as above was measured using a plasma aching device. ．． 5
8 at 0 cc/min oxygen flow and 1 Torr internal pressure
When performing 1-ashing by applying a high frequency of -100W at 13.56 MHz for 1 minute, the base material film part where no graft polymerized film is formed, which is the part not irradiated with high-energy rays, was completely removed, and the high-energy rays Only the graft polymer film pattern, which was the irradiated area, remained. Also, in this case, about 50
0 people (O, O 5 μm) Graft polymer film thinning of the pattern part; B, H, 2 squares / ζ0 Example 2 A polymethyl methacrylate base film with a film thickness of 0.2 μm was prepared using the same method as in Example 1. After producing four pieces and irradiating them with an electron beam in the same manner as in Example 1, they were quickly transferred to an oxygen-free vacuum atmosphere so that each base material did not come into contact with oxygen. Maleimide, N-vinylcarbazole, vinyltrichlorosilane, or acrylonitrile gas was introduced into the base film, which was thus transferred to a vacuum atmosphere, as an atmosphere of various monomer gases capable of addition polymerization, each at a pressure of 3 mbar. 1-Graft polymerization was carried out by standing for 1 hour until i. In any monomer gas atmosphere,
A uniformly glossy film with no surface defects in the irradiated area was obtained. Furthermore,
No increase in film thickness was observed in non-irradiated areas. In this case, as in Example 1, the amount of increase in the film thickness of the high-energy ray irradiated area was measured, and it was found that as the amount of high-energy ray irradiation increased, the amount of increase in the film thickness increased, but graft polymerization did not occur. 7) Table 2 shows that when the film thickness increase in the irradiated area is 0.4 μm for each monomer gas atmosphere, This shows the required amount of high-energy ray irradiation.

Table 2 Next, the graft polymer film pattern on each base film prepared above was subjected to plasma ashing in the same manner as in Example 1 to obtain the same graft polymer film pattern as in Example 1.

Example 3 A silicon wafer whose surface was thermally oxidized was cooled to 0°C in vacuum, degassed in advance, and cooled to -5°C.
A large amount of gas was introduced into the methyl methacrylate monomer solution containing 1 ml of propionaldehyde. Gas pressure in all cases was 7.5 Torr. In this state, the surface of the silicon wafer was irradiated with a high-pressure mercury lamp through a quartz glass window for 3 hours to form a base film made of a vapor phase polymerized film on the surface of the silicon wafer. The thickness of the gas phase polymerized film in this case is 0.23μ
It was m.

Next, the base film is transferred to an electron beam irradiation device, an X-ray irradiation device, and a far ultraviolet irradiation device in a state where it cannot come into contact with oxygen.
-1 Each energy field was irradiated in the same manner as in Example 1.

After irradiation, the base film was quickly transferred to an oxygen-free vacuum atmosphere to avoid contact with oxygen, and then styrene gas was introduced at a pressure of 3 mbar and left for 1 hour to prevent graft polymerization on the irradiated area. went. Regardless of the irradiation source and base film, a uniformly glossy film with no surface defects in the irradiated area was obtained. Furthermore, no increase in film thickness was observed in the non-irradiated area 1.

When we measured the amount of increase in film thickness in the high-energy ray irradiated area, we found that
The amount of increase in film thickness increases as the amount of high-energy ray irradiation increases, but it varies from 0.6 to 1.0 depending on the graft polymerization conditions.
A saturation phenomenon of film thickness increase was observed above 0 μm.

Table 3 shows, for each high-energy ray, the amount of high-energy ray irradiation required to increase the film thickness of the irradiated area by 0.4 μm.

Table 3 Next, the graft polymerized film pattern on each base film prepared above was subjected to plasma ashing in the same manner as in Example 1 to obtain the same graft polymerized film pattern as in Example 1.

Example 4 A polymethyl methacrylate base film having a film thickness of 0.2 μm was prepared in the same manner as in Example 1, and then electron beam irradiation was performed in the same manner as in Example 1. In this case, the line pattern width of electron beam irradiation is 5 μm.

The thickness was 6 μm, 1 μm, 0.5 μmlO, and 2 μm, and the irradiation period was changed for each.

After electron beam irradiation, the base film was quickly moved to an oxygen-free vacuum atmosphere to prevent it from coming into contact with oxygen, and 3 mbar styrene gas was introduced into this and left for 1 hour to allow graft polymerization to the electron beam irradiated area. went.

The graft polymerization pattern prepared by the above method was observed with a scanning electron microscope, and it was found that the graft polymerization film with a line width of 5 μm was 0.4 μm at an irradiation dose of 200 μC/d from Example 1.
0.4μ for other line widths compared to 0.4μ for other line widths.
The electron beam irradiation dose that would give a film thickness of m was determined. The results obtained are shown in Table 4.

Table 4 The resist process according to the present invention, as shown in the above examples, includes base film formation by photo-vapor phase polymerization, high-energy ray irradiation, selective graft polymerization, and dry etching of the substrate to be processed. All of this can be carried out in a vacuum or without contact with the outside air, and because it does not use organic solvents, there is no risk of device contamination due to impurities or the yield rate due to dust, etc.
Not only is this a significant improvement, but the high-precision clean room that was previously required is no longer necessary, making it possible to achieve significant economic savings.

As described above, according to the present invention, it is possible to directly form any resist pattern for high-precision microfabrication on the surface of a substrate to be processed by a dry method.

[Brief explanation of the drawing]

The drawings are process diagrams showing a specific example of turn formation according to the present invention. 1... Substrate 2... Base film 3...
...High energy rays 4 ...Monomer atmosphere 5 ... Graft polymer membrane patent applicant Hiroshi Nakamoto, agent of Nippon Telegraph and Telephone Public Corporation

Claims (1)

[Claims] (1) Form a film made of a base material that generates active points that can initiate addition polymerization by irradiation with high-energy rays on a substrate, irradiate the film with high-energy rays in a pattern, and then place the irradiated film in a monomer gas atmosphere. A method for forming a pattern, comprising: selectively graft-polymerizing the irradiated portion of the pattern to form a graft-polymerized film having a pattern shape.