JPS60222848A - Formation of pattern - Google Patents

Abstract

PURPOSE:To enhance resolution and to suppress dispersion of finishing dimensions by depositing an org. photosensitive compd. through vacuum evaporation to form a thin photosensitive film on the substrate to be worked at the time of forming a pattern on said thin photosensitive org. film through exposure and development. CONSTITUTION:The thin photosensitive org. film layer is formed by evaporating and depositing an org. compd., such as omega-tricosenic acid, having a hydrophilic group on one terminal of the molecular structure and a hydrophobic group on the other terminal in vacuum on the substrate to be worked. This thin film is exposed in a prescribed pattern and plasma treated in a low-temp. gas plasma atm. essentially consisting of oxygen to execute development and to form an intended pattern. As a result, since the photosensitive compsn. layer can be reduced in thickness, a pattern high in resolution is obtained, and since layer is oriented in the film thickness direction, anisotropic development is executed and development can be enhanced in dimensional precision.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a pattern forming method, and particularly to a pattern forming method that has high resolution and is suitable for suppressing variations in processing dimensions.

[Background of the invention]

In conventional pattern forming methods, a solution of a photosensitive composition is spin-coated onto a substrate such as a silicon wafer to form a thin film of the composition, and this is developed to form a desired pattern. Incidentally, as semiconductors become more highly integrated, finer patterns of 1 μm or less are required. In order to achieve this, it is necessary to make the photosensitive composition layer thin, but it is difficult to form a thin film of 0.1 μm or less without defects using a spin coating method.

In addition, as semiconductor wiring becomes multilayered, patterns must be formed in advance. It is necessary to form a photosensitive composition layer on a substrate having steps. However, with the spin coating method, it is impossible to form a film with a uniform thickness along a surface having steps.

Furthermore, in conventional resist pattern forming technology, in order to suppress dimensional variations in the resist pattern after development (improve dimensional accuracy), it is mainly necessary to improve the resolution of the exposure device and strictly control the development conditions. is necessary.

However, as the resolution becomes higher, the cost associated with the ny6 device inevitably increases, which poses a problem as a mass production technology.

Furthermore, even if the development conditions are controlled, it is almost impossible to control the flow and diffusion of chemical species involved in development, so the degree of variation in development dimensions cannot be ignored compared to the pattern width. That is clear.

Langmuir-F is another method for obtaining organic thin films.
31 o d get; l; method (L B method) is known. This is a method in which the monomolecular film is sequentially transferred onto the substrate by raising and lowering the substrate on the surface of water on which a monomolecular layer has been developed. It is also possible to form a fine pattern by irradiating the thin film of 0.1 μm or less produced in this way with an electron beam, and Mo1. Crys+:,l,iq,Crys7,96
353 ('83) ya J, Materials Sc
i, 182603 ('83), etc.

However, the patterns obtained using this method have many defects.
There were two types of these defects. The first is due to dust in the air. In the LB method, the substrate is exposed to air for a long time because it is moved up and down slowly. Although the above experiment was conducted in a class 10 clean room, it is presumed that dust in the air adhered to the substrate during film formation.

The second defect is due to corrosion of the Si wafer used as the substrate, and does not exist in the conventional spin coating method. Film formation was performed using triple-distilled water, but
Even so, electrolyte contamination is unavoidable, and this causes Si
It is thought that it was corroded.

From the above results, it was found that there are many problems in terms of mass production when applying the LB method to semiconductor processes.

Furthermore, with this LB method, it is also difficult to form a film on a substrate having steps.

[Purpose of the invention]

An object of the present invention is to overcome the problems of the prior art and provide a method for forming fine patterns with high dimensional accuracy. Furthermore, it is an object of the present invention to provide a method for realizing similar pattern formation even on a substrate having steps.

[Summary of the invention]

Some of the inventors of the present invention have discovered that an alignment film equivalent to that obtained by the Langmujr and Blodgett method can be obtained by vacuum deposition of a surface-active substance, thereby obtaining the present invention.

The vacuum evaporation method is an excellent method for obtaining thin films, and because the molecules in the film are oriented, it is difficult to use electron beams.

Structural changes in the film proceed rapidly by irradiation with X-rays or ultraviolet light. Furthermore, since the film is formed in a vacuum, it has the advantage that there is no fear of defects caused by the influence of dust or corrosion of the substrate.

[Embodiments of the invention]

Example 1 A partial carboxylic acid (shown below) having a double bond at the ω position was prepared by resistance heating a tantalum boat with a film thickness of 0 and 1 mm.
ω-IZrjcosenoic acj, d) was vacuum deposited on the St substrate.

CH2= CH(CH2) qo The degree of vacuum in the COOH vacuum apparatus was 1.5×10”Pa, and the Si wafer was rotated at 1100 rpm with the support stand to ensure uniform film thickness.The shortest distance between the wafer and the bow was The distance was ]Ocm.During the deposition, changes in the natural frequency of the crystal oscillator were monitored, and the value of the current flowing through the boat was controlled so that the deposition rate was constant.

After vapor deposition for 60 minutes, the inside of the apparatus was returned to atmospheric pressure and the wafer was taken out.

When we measured the film thickness of one of the multiple wafers on which organic thin films were simultaneously fabricated using multiple interference method, we found that it was 0.35 μm.
It was m. When the other sheet was subjected to X-ray diffraction, a diffraction pattern indicating orientation was obtained. A resolution test pattern was drawn on the remaining samples using an electron beam drawing device. The irradiation dose is .mu.c/Cm2. When the drawn sample was developed with ethanol, the nominal value was 0.25μ.
Patterns were formed up to the minimum repeating pattern of m lines and 0.25 μm spaces. As far as observation using a scanning electron microscope was concerned, there were no defects in the resulting pattern.

The effect of development time on dimensional accuracy was investigated for isolated lines with a nominal diameter of 0.5 μm. The results are shown in Figure 1. The horizontal axis is the immersion time in ethanol, and 50% in the same web.
The vertical axis shows the average value of the line width measured for the points. When the development time is 20 seconds or more, the dimensional variation within the same web is 0.027 μm, and the dependence of the average line width on the development time is small.

Therefore, according to the present invention, the dimensional accuracy is approximately 1
The development time has also become more flexible.

The reason for the above result can be considered as follows. In the deposited film, each molecule is oriented in a direction perpendicular to the substrate. Therefore, when the thin film is immersed in a solvent, there is anisotropy in the rate of penetration of the solvent into the film. That is, the permeation rate in the thickness direction along the molecular axis is high, but it is difficult for the medium to permeate in the lateral direction.

Therefore, it is thought that the dimensional accuracy is improved and the dependence on development time is small.

Example 2 The ω-I licosenic acid used for vapor deposition in Example 1 was synthesized by a known method, and was obtained by repeating purification at each stage of synthesis. A pattern was formed in the same manner as in Example 1 using ω-tricosenic acid synthesized without going through the process of purification, and the same results as in Example 1 were obtained. Although the omega-tricosenic acid used in this example contains impurities, no decrease in recording sensitivity or resolution, which may be caused by impurities, was observed.

Example 3 A resolution test pattern was drawn on a partially carboxylic acid vapor-deposited film of the St wafer+, which was formed in the same manner as in Example 1, using an electron beam drawing device. Irradiation dose is 0.5μc/cm
”, which is the dose at which only the surface layer of the thin film reacts.

The five samples that had been drawn were placed in a cylindrical plasma processing apparatus, and a mixed gas of 02:CF4=9:1 was introduced and the pressure was set at 200 Pa, followed by 13.56M.
Plasma was generated by applying a high frequency voltage of Hz, and development was performed for 2 minutes.

After development, the remaining film thickness of the formed pattern was measured and found to be 0.41 μm. Of the developed patterns, the nominal 0.2 μm line-0.2 μIn space repeat pattern was the smallest. The dimensional accuracy of an isolated line with a nominal diameter of 0.5 μm was measured using a scanning electron microscope for length measurement, and the result was 0.48 ± 0.0 for 50 points within an I-wafer.
A value of 0.021 μm (average standard deviation x 3) and 0.470±0.029 pm for five wafers was obtained.

According to the prior art, the dimensional variation (evaluated by three times the standard deviation of the dimensional measurement values) is 0.2 under similar conditions.
It is clear that the present invention suppresses this by about one order of magnitude and significantly improves the dimensional accuracy.

Although plasma distribution is normally non-uniform in cylindrical plasma processing equipment, the method of the present invention has extremely small variations within the same wafer and between multiple wafers. This shows that even if the control over the development conditions is loose, highly accurate processing is possible.

As in the case of Example 1, anisotropy of development occurs also in the case of the plasma development process, and this is considered to be the reason for the improvement in dimensional accuracy.

In the above embodiments, the pattern was formed by electron beam irradiation, but the irradiation source is not limited to this, and ultraviolet rays, X-rays, ion beams, etc. can also be applied.

Any organic material can be used for vacuum deposition to form the resist. However, in order to obtain high recording sensitivity, the organic compound must be a surface active substance that has a polar group at one end and a hydrophobic group at the other end, and must have at least one -H unsaturated bond or It is desirable to contain quaternary carbon.

Surface-active substances having unsaturated bonds include unsaturated monocarboxylic acids and their metal salts such as ω-tricosenic acid and diacetylene monocarboxylic acid, long chain derivatives of acrylic acid such as α-octadecyl acrylic acid, octadecyl acrylate, etc. Examples include esters of acrylic acid and methacrylic acid such as octadecylmethacrylate-1-.

Further, for example, long-chain derivatives of O-quinonediazide compounds, which undergo structural isomerization upon photolysis, are also suitable materials for carrying out the present invention.

〔Effect of the invention〕

The effects of the present invention are listed below.

(1) According to the present invention, since the thickness of the photosensitive composition layer can be reduced, a pattern with high resolution can be obtained. The conventional spin coating method had a width limit of 0.2 μm, but the width of 0.09
A pattern with a width of 0.15 μm was obtained from a deposited film with a thickness of 5 μm. By reducing the film thickness, it is also possible to form finer patterns.

(2) Since the photosensitive composition layer is oriented in the film thickness direction, there is anisotropy in development, and the dimensional accuracy is improved by about one order of magnitude compared to the conventional technology.

(3) Since the film is formed in a clean atmosphere such as vacuum, a pattern with fewer defects is formed. The degree of defect occurrence is the same as or lower than that of the conventional technique, and is improved by more than one order of magnitude compared to the LB method.

(4) Patterns can be formed with high sensitivity even from vapor deposition materials containing impurities. When forming an alignment film using the LB method, if impurities are contained in the film, the alignment will be disturbed and the sensitivity will decrease. Therefore, it is necessary to form the membrane using sufficiently purified materials.

On the other hand, during vacuum evaporation, contaminants with high vapor pressure evaporate first, and contaminants with low vapor pressure remain in the boat.

Therefore, in the vacuum evaporation method, a film is formed while being purified, and a thin film of a single component can be obtained.

(5) As shown in Example 3, the irradiation energy for forming a latent image only needs to be an amount sufficient to cause the resist surface layer to react;
It is sufficient to use an irradiation dose of /2 or less, and the same effect as that of improved resist sensitivity can be obtained.

[Brief explanation of the drawing]

Claims (1)

[Scope of Claims] 1. A pattern forming method by exposing and developing a photosensitive organic thin film layer, characterized in that the organic thin film is formed on a substrate to be processed by vacuum evaporation of an organic compound. Method. 2. The pattern forming method according to claim 1, wherein the organic compound constituting the organic thin film has a parent group at one end and a hydrophobic group at the other end. 3. The pattern forming method according to claim 1, wherein the developing process is plasma treatment in a low-temperature gas plasma atmosphere containing oxygen as a main component.