JPS6278200A - Method of forming orientation organic thin film - Google Patents

Abstract

PURPOSE:To form an orientating organic thin film by a safe, dry process without using water, etc., by heating and melting a polycrystalline organic thin film obtained by depositing evaporated organic monomer molecules on the surface of a substrate and cooling the thin film. CONSTITUTION:Evaporated organic monomer molecules are attached to the surface of a substrate to form a polycrystalline organic thin film. Then, the organic thin film is heated, melted and cooled to give the aimed organic thin film. Attaching of the organic monomer molecules to the surface of a substrate is carried out by applying vacuum deposition method, CVD method, plasma CVD method, etc. A film-forming organic compound such as fatty acid, unsaturated group-containing fatty acid, unsaturated hydrocarbon, protein, etc., is properly selected depending upon the purpose and use. Either substrate having flat surface of specular gloss or a substrate having difference in level can be used.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for forming an oriented organic thin film, and more particularly to a method for forming an oriented organic thin film by a dry process.

Technical background of the invention and its problems In recent years, there has been increasing interest in Langmuir-Prodgett films (LB films), which are expected to be applied to resists for ultrafine processing and the like as functional organic thin films. This Langmuir Project (LB film) is conventionally formed by forming a monomolecular film of an organic compound on the water surface and laminating the films one by one on a substrate, and can be produced at room temperature and pressure. It has the advantage that it can be easily made into a large area. With the progress of research on electrical properties, this ultra-thin film is expected to be applied in the field of functional thin films, and linear saturated fatty acids or their metal salts, which are known as film-forming molecules, are expected to be used. A thin film consisting of a resist material, an insulating thin film, a soft X-ray diffraction grating (Pb salt film), a two-dimensional magnetic material (
It is being considered to be used for Mnn film formation.

However, conventional Langmuir-Prodgett (LB) films have been formed by a wet method using water as mentioned above, so when selecting the type of film-forming molecules, the type and properties of the substrate material, etc. A major problem was the limitations associated with the wet method. Therefore, there has been a desire for a new method for forming organic thin films that does not have these limitations, as well as a method for converting the thin films into functional thin films.

Purpose of the Invention The present invention aims to solve the problems associated with the prior art as described above, and it is possible to form an oriented organic thin film by a completely dry process without using water or the like. It is an object of the present invention to provide a method for forming an oriented organic thin film that can impart orientation to the thin film, and it can be said that the present invention opens up new prospects for the production of organic thin films.

Summary of the Invention The method for producing an oriented organic thin film according to the present invention involves depositing evaporated organic monomer molecules on the surface of a substrate to form a polycrystalline 1aH film, and then heating and melting this organic thin film. It is characterized by cooling after that.

The organic monomer molecules may be deposited on the surface of the substrate by any method as long as the evaporated molecules are deposited on the substrate, such as vacuum evaporation, CVD, plasma carbon dioxide, etc.
A VD method or the like is appropriately employed. Regarding the organic monomer molecules that are film-forming molecules, film-forming organic compounds such as fatty acids, unsaturated group-containing fatty acids, unsaturated hydrocarbons, and proteins are appropriately selected depending on the purpose and use.

Specifically, stearic acid or a metal salt thereof is often used as the fatty acid, and vinyl stearate or the like is used as the unsaturated group-containing fatty acid.

There are no particular restrictions on the substrate used, and either a substrate with a flat, mirror-like surface or a substrate with steps can be used. Alternatively, a glass substrate on which a metal thin film is deposited by vacuum evaporation or the like can also be used as the substrate surface.

At this time, it is also possible to use the substrate surface by sequentially depositing two or more metal thin films on a glass substrate and etching the top layer to form a step. Specifically, a metal film such as copper, aluminum, chromium, titanium, etc., or an organic film is deposited on a glass substrate, or a silicon wafer or an inorganic substrate such as a glass substrate is coated with silicon or an organic film. A surface coated with a thin film of amorphous carbon can be used as the substrate surface. Note that a characteristic feature of this invention is that a hydrophobic substrate can also be used, which means that
This was not expected from the conventional wisdom of wet methods. It was discovered for the first time by the present invention that an oriented organic thin film can be formed on the surface of a hydrophobic substrate on which an inorganic film such as an amorphous carbon thin film is deposited.

After forming a polycrystalline organic thin film by depositing the evaporated organic monomer molecules on the surface of such a substrate as shown in (a) above, this Ia thin film is heated and melted. This can be done, for example, by heating the entire substrate or by irradiating a laser beam onto an organic thin film deposited on the surface of the substrate. This organic thin film is heated in the air or in an inert gas atmosphere. By melting the thin film as described above and then cooling it, an organic thin film with oriented single crystals can be obtained, and this oriented thin film can be used as a functional thin film.

Regarding this invention having the configuration described above, the effects of forming an oriented organic thin film will be explained with reference to the attached drawings.

The figure shows an amorphous carbon (a-C) film formed on a glass substrate by plasma CVD method as the deposition substrate surface, and stearic acid is deposited as a film-forming molecule on the surface of this clogging plate. It is a micrograph of the obtained organic thin film. Figure 1 shows the film produced by vapor deposition of stearic acid monomer (vacuum 1, 2 x 10'
Torr). The part with a small particle size is the film deposited on the hydrophilic part, and the part with a large particle size is the film deposited on the hydrophobic part.

FIG. 2 shows a deposited film heated in the atmosphere. Figure 3 is a partially enlarged version of Figure 2.
It can be seen that there is a diamond shape with an angle of 55 degrees, which is a characteristic of C-type single crystals of stearic acid.

Table 1 shows the X-ray grid pattern of the C-type single crystal thus obtained.

Table 1 C-type single crystal (monoclinic) l, m, n 2θ2 2θ20.0,1
2.22 2.320.0,2 4.4
4 4.650.0,3 6.66 6
．． 980.0,4 8.88 9.310.
0,5 11.11 11.640.0.6
13.34 13.980.0,7 15.5
7 16.330.0.8 17.81 18
．． 680.0,9 20.06 21.040.
0.10 22.32 23.4.10.0.12
26.86 28.180.0.14 31.
44 33. ○○○, 0.16 36. ○7 3
7.880.0,18 40.77 42.830
．． 0,20 45.54 47.87 2θ1.2 above
The lattice constants were determined from θ2.

For lattice constant 2θ1 a = 9.363A b = 4.965A C = 50.88A B = 128.46° For 2θ2 a = 9.51A b = 4.95A C = 51.4A B = 129.6° Functionality The significance of this invention is extremely large, and its effects are obvious, as it has realized an oriented organic thin film, which is expected to be applied as a thin film to resists for ultrafine processing, etc., through a completely dry process.

The present invention will be explained in detail below.

- Approximately 200 μm thick C was deposited on a glass substrate by vacuum evaporation.
A thin film of u1Cr or Ti was deposited and then an A1 layer was deposited on this metal film.

The A1 layer, which is the upper layer of this two-layer deposited film, was etched into slits with a width of 4 to 100 μ by a lithography process. A step was formed by these two layers.

This metal film with steps is used as the surface of the substrate for vapor deposition, using stearic acid with a purity of 95% or more as a monomer,
An organic thin film was formed on the substrate by vacuum deposition at 6×10 −6 Torr using a tungsten boat. The obtained organic thin film was heated with a He-Ne laser or a He-Cd laser using a lens system and a substrate moving device at a laser power density of 2.4 W/mm2 and a scanning speed of '1 Qmm/m.
In, the organic thin film was heated by laser irradiation at a substrate temperature of 26°C. As a result, the vapor-deposited stearic acid film in the laser-irradiated area melted, and when it was cooled again, a planar single-crystal thin film was formed.

Example 2 Using a plasma CVD device with a parallel plate electrode system with a diameter of 20 cm and an electrode gap of 3.5 cm, methane 2QSCC)
1, hydrogen 23 CCH, gas pressure Q, 1 Torr, discharge frequency 13.45 MHz, and discharge power 100 W.
Amorphous carbon (
a-C) Membranes were coated. This a-C film has a contact angle of 9 when exposed to distilled water at room temperature (approximately 20°C) in the atmosphere.
Shows 0° hydrophobicity. On the a-C film deposited on the silicon wafer thus obtained, 98% pure stearic acid (40IO or 80111 (1> is the monomer and 1,2 x 10 'Tor
A stearic acid organic thin film was formed by vacuum evaporation at r for 30 minutes or [ ].

Next, the temperature of the entire substrate is raised in the air to the melting point of stearic acid (70 to 80°C) to melt the stearic acid,
Heated for minutes. When the material was cooled at a cooling rate of about 5° C./hr, a crystallized thin film was formed. This crystal exhibited a rhombic shape with an angle of 55 degrees, which is a characteristic of a C-type single crystal.

[Brief explanation of drawings]

The figure is a micrograph of a case where stearic acid is applied to an amorphous carbon (a-C) film. FIG. 1 is a microscopic photograph of the deposited film before heating, FIG. 2 is a microscopic photograph of the vapor deposition film after heating, and FIG. 3 is a partially enlarged microscopic photograph of FIG. 2.

Claims (11)

[Claims] (1) Formation of an oriented organic thin film characterized by depositing evaporated organic monomer molecules on the surface of a substrate to form a polycrystalline organic thin film, then heating and melting this organic thin film, and then cooling it. Method. (2) The method according to claim 1, wherein the organic monomer molecules are deposited on the substrate surface by vacuum deposition. (3) The method according to claims 1 and 2, wherein the organic monomer molecule is a fatty acid. (4) The method according to claim 3, wherein the organic monomer molecule is stearic acid. (5) The method according to any one of claims 1 to 4, wherein the substrate surface is a single layer film or a multilayer film having a mirror surface or steps. (6) The method according to claim 5, wherein the substrate surface is a metal film. (7) The method according to claim 5, wherein the substrate surface is an organic film or an inorganic film. (8) The method according to claim 7, wherein the substrate surface has hydrophobicity. (9) The method according to any one of claims 7 to 8, wherein the substrate surface is an amorphous carbon film. (10) The method according to any one of claims 1 to 9, wherein the organic thin film is heated by heating the entire substrate. (11) The method according to any one of claims 1 to 9, wherein the organic thin film deposited on the surface of the substrate is heated by irradiating the organic thin film with a laser beam.