JPH067545B2 - Pattern formation method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern forming method, and more particularly to a pattern forming method having high resolution and suitable for suppressing variations in processing dimensions.

[Background of the Invention]

In a conventional pattern forming method, a solution of a photosensitive composition is spin-coated on a substrate such as a silicon wafer to form a thin film of the composition, and this is developed to form a desired pattern. By the way, with the high integration of semiconductors, 1
A fine pattern of less than μm is required. In order to achieve this, it is necessary to thin the photosensitive composition layer, but it is difficult to form a thin film of 0.1 μm or less without defects by the spin coating method.

In addition, a pattern has been formed in advance due to the multi-layered wiring in the semiconductor. It is necessary to provide a photosensitive composition layer on a substrate having steps. However, it is impossible to form a film having a uniform thickness on a surface having steps by the spin coating method.

Furthermore, in the conventional resist pattern forming technique, in order to suppress the dimensional variation of the resist pattern after development (improve the dimensional accuracy), it is mainly necessary to improve the resolution of the exposure apparatus and strictly control the development conditions. is necessary.
However, an increase in cost associated with the exposure apparatus is inevitable as the resolution becomes higher, which causes a problem as a mass production technique. Further, even if the development conditions are controlled, it is almost impossible to control the flow and diffusion of the chemical species involved in the development.Therefore, the degree of variation in the development dimension can be ignored sooner or later than the pattern width. It is clear that it will disappear.

The Langmuir-Blodgett method (LB method) is known as another method for obtaining an organic thin film. This is a method in which the substrate is moved up and down on the water surface on which the monomolecular layer is developed, and the monomolecular film is sequentially transferred onto the substrate. It is also possible to form a fine pattern by irradiating an electron beam on the thin film of 0.1 μm or less produced in this way. Mol.Cryst.Liq.Cryst. 96 353 ('83) and JM
There is a description in aterials Sci. 18 2603 ('83) and the like.

However, the pattern obtained by this method has many defects,
There were two types of defects. The first is due to dust in the air. In the LB method, the substrate is exposed to the air for a long time in order to make it move up and down. Class 10
The above experiment was carried out in the clean room of No. 2, but 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, which has not existed in the conventional spin coating method. A film was formed using water distilled three times.
Even so, mixing of the electrolyte is unavoidable, which results in Si
Is thought to have corroded.

From the above results, it was found that there are many problems in mass productivity when the LB method is applied to a semiconductor process. Furthermore, this L
Also in the B method, it is difficult to form a film on a substrate having a step.

[Object of the Invention]

An object of the present invention is to overcome the problems of the prior art and to provide a fine pattern forming method having high dimensional accuracy. Another object of the present invention is to provide a method for realizing the same pattern formation on a substrate having a step.

[Outline of Invention]

Some of the inventors have found that vacuum deposition of surfactants
The present invention was obtained by finding that an alignment film equivalent to that obtained by the Langmuir.Blodgett method can be obtained. The vacuum vapor deposition method is an excellent means for obtaining a thin film, and since each molecule is oriented in the film, the structural change in the film is promptly caused by irradiation with electron beams, X-rays or ultraviolet light. proceed. Further, since the film is formed in a vacuum, there is also an advantage that there is no fear of the influence of dust and the occurrence of defects due to corrosion of the substrate.

Examples of the Invention Example 1 A monovalent carboxylic acid having a double bond at the ω position (ω-tr) shown below by resistance heating to a tantalum boat having a film thickness of 0.1 mm.
icosenoic acid) was vacuum-deposited on a Si substrate.

CH ₂ = CH (CH ₂ ) ₂₀ COOH The degree of vacuum in the vacuum device is 1.5 × 10 ⁻³ Pa, and Si
The wafer was rotated together with the support at 100 rpm to make the film thickness uniform. The shortest distance between the wafer and the boat is 10 cm. During vapor deposition, changes in the natural frequency of the crystal oscillator were monitored, and the current value passed through the boat was controlled so that the vapor 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 the film thickness of one of the plurality of wafers on which the organic thin film was formed was measured by the multiple interference method, it was 0.35 μm.
It was m. When X-ray diffraction was performed on the other sheet, a diffraction pattern showing orientation was obtained. A resolution test pattern was drawn on the remaining sample by an electron beam drawing apparatus. The irradiation dose is 1 μc / cm ² . When the developed sample was developed with ethanol, it was nominally 0.25 μm
The pattern was formed up to the minimum repeated pattern of the line-0.25 μm space. No defect was found in the obtained pattern as observed by a scanning electron microscope.

The effect of development time on the dimensional accuracy was investigated for a nominal line of 0.5 μm. The results are shown in Fig. 1. The horizontal axis is the time of immersion in ethanol, and the
The average of the line widths measured at the points is shown on the vertical axis. When the developing time is 20 seconds or more, the dimensional variation is 0.027 μm in the same wafer, and the dependency of the average line width on the developing time is small. Therefore, according to the present invention, the dimensional accuracy is improved by about one digit as compared with the prior art, and the margin of the developing time is increased.

The reason for the above result is considered as follows. In the vapor deposition film, each molecule is oriented in the direction perpendicular to the substrate. Therefore, when the thin film is immersed in a solvent, the rate of penetration of the solvent into the film is anisotropic. That is, the permeation rate in the thickness direction along the molecular axis is high, but the solvent is unlikely to permeate in the image direction.
Therefore, it is considered that the dimensional accuracy is improved and the development time dependency is small.

Example 2 The ω-tricosenoic acid used for vapor deposition in Example 1 was synthesized by a known method, but it was obtained by repeating purification at each step of the synthesis. A pattern was formed in the same manner as in Example 1 by using ω-tricosenoic acid obtained by synthesizing without undergoing a purification process, and the same result as in Example 1 was obtained. The ω-tricosenoic acid used in this example contains impurities, but no decrease in recording sensitivity or resolution, which is probably due to impurities, was recognized.

Example 3 A resolution test pattern was drawn on the vapor-deposited film of monovalent carboxylic acid on a Si wafer formed by the same method as in Example 1 using an electron beam drawing apparatus. Irradiation dose is 0.5 μc / cm ²
That is, the irradiation dose is such that only the thin film surface layer reacts.

The five drawn samples were placed in a cylindrical plasma processing apparatus, a mixed gas of O ₂ : CF ₄ = 9: 1 was introduced to set the pressure to 200 Pa, and a high frequency voltage of 13.56 MHz was applied. Application was performed to generate plasma, and development processing was performed for 2 minutes.

After development, the residual film thickness of the formed pattern was measured and found to be 0.41 μm. Of the developed patterns, the smallest repeating pattern having a nominal 0.2 μm line-0.2 μm space was the smallest. As a result of measuring the dimensional accuracy with a side-scanning electron microscope for an independent line of nominally 0.5 μm, 0.48 ± 0.021 per 50 points in one wafer
μm (mean ± standard deviation x 3), 0.47 for 5 wafers
A value of 0 ± 0.029 μm was obtained.

According to the prior art, the dimensional variation (evaluated by 3 times the standard deviation of dimensional measurement values) is 0.2 under similar conditions.
Since it was on the order of μm, it is clear that the present invention suppressed it by about an order of magnitude and significantly improved the dimensional accuracy.

In the cylindrical plasma processing apparatus, even though the plasma distribution is usually non-uniform, the variation within the same wafer and the variation among a plurality of wafers are extremely small. According to this, it is shown that high-precision processing is possible even if the control for the developing conditions is gentle.

As in the case of Example 1, development anisotropy also occurs in the case of the development process using plasma, and it is considered that this improves dimensional accuracy.

In the above-mentioned embodiment, the pattern is 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 as the organic material that is subjected to vacuum deposition to form a resist. However, in order to obtain high recording sensitivity, the organic compound is a surface-active substance having a polar group at one end and a hydrophobic group at the other end, and has one or more unsaturated bonds or quaternary groups in the molecule. It is desirable to include carbon.

As the surface-active substance having an unsaturated bond, unsaturated monocarboxylic acids such as ω-tricosenoic acid and diacetylene monocarboxylic acid and metal salts thereof, long-chain derivatives of acrylic acid such as α-octadecylacrylic acid, octadecyl acrylate and Examples thereof include acrylic acid such as octadecyl methacrylate and esters of methacrylic acid.

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

〔The invention's effect〕

 The effects of the present invention are listed below.

(1) According to the present invention, since the film thickness of the photosensitive composition layer can be reduced, a pattern with high resolution can be obtained. The conventional spin coating method had a limit of 0.2 μm width, but 0.095 μm
A 0.15 μm wide pattern was obtained from the vapor-deposited film having a thickness of m. A finer pattern can be formed by reducing the film thickness.

(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 digit as compared with the conventional technique.

(3) Since the film is formed in a clean atmosphere called vacuum, a pattern with few defects is formed. The frequency of occurrence of defects is the same as or lower than that of the conventional technique, and is improved by one digit or more as compared with the LB method.

(4) A pattern is formed with high sensitivity even from a vapor deposition material containing impurities. When the alignment film is formed by the LB method, if the film contains impurities, the alignment is disturbed and the sensitivity is lowered. Therefore, it is necessary to form a film using a sufficiently purified material. On the contrary, during vacuum deposition, the irregular products having a high vapor pressure evaporate first, and the irregular substances having a low vapor pressure remain in the boat. Therefore, in the vacuum deposition method, a film is formed while purifying, and a single-component thin film is obtained.

(5) As shown in Example 3, the irradiation energy for forming a latent image may be an amount sufficient for the resist surface layer to react, so that the irradiation amount required in the conventional method is 1
A dose of ½ or less is sufficient, and the same effect can be obtained as the resist sensitivity is improved.

[Brief description of drawings]

FIG. 1 is a graph showing the influence of development time on dimensional accuracy.

Claims (3)

[Claims] 1. A pattern forming method in which a latent image is formed in a thin film by exposing the photosensitive organic thin film layer, and the latent image is patterned by development. In the pattern forming method, the organic thin film is formed of an organic compound. A pattern forming method characterized by using a vacuum deposition method. 2. The organic compound constituting the organic thin film,
The pattern forming method according to claim 1, which is an amphipathic one having a hydrophilic group and a hydrophobic group in one molecule. 3. The pattern forming method according to claim 1, wherein the developing process is a plasma treatment in a low temperature gas plasma atmosphere containing oxygen as a main component.