JPH08176803A - Method for producing molecularly oriented organic film - Google Patents

Abstract

PURPOSE: To obtain an extremely thin oriented org. film having excellent surface flatness and high purity by alternately laminating plural ionized molecules on a substrate by vapor deposition. CONSTITUTION: A crucible is heated by a resistance heater in an ion source, for example, to sublimate a monomer put in the crucible, and the sublimated monomer is ionized by an electron impact in an ionization part above the crucible. The ion beam is then accelerated with a voltage Va' and irradiated on the substrate. A heater for controlling the substrate temp. and annealing the polymerized film is set above the substrate and a rate monitor between the ionization part and substrate, and vapor deposition is conducted while monitoring its rate. Vapor deposition and polymerization are performed simultaneously or alternately by opening a shutter above the two kinds of ion sources. A polyimide thin film is produced with this device from the pyromellitic dianhydride and oxydianinline as the two kinds of ion sources. The liq. crystal oriented film, the ultra-flat interface in an LSI and an extremely thin insulating film are formed by this method with good reproducibility, and this method can be applied to a molecular device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an organic film. More specifically, the present invention relates to LS
The present invention relates to a method for producing a molecularly oriented organic film, which is useful as a radiation resistant material, a material for outer space, etc., by an ion beam alternating vapor deposition polymerization method.

[0002]

2. Description of the Related Art Organic polymer polymers are useful as interlayer insulating films and liquid crystal alignment films for LSIs and the like and have excellent electrical, optical and mechanical properties. In particular, for example, polyimide has a high glass transition point, and is excellent in heat resistance, chemical stability, orientation controllability, etc., so it is also used as a heat-resistant radiation material and a space material, and is used as a superconducting magnet for a fusion reactor. It is also considered to be used as an insulating material and a protective material that prevents deterioration of equipment due to atomic oxygen in outer space.

As a method for obtaining such a polymerized polymer film, conventionally, a method of polymerizing a monomer using a solvent and coating the obtained solution on a substrate is known. 1000 Å
It was difficult to obtain the following uniform thin film. As a method for forming a monolayer film, Langumuir-Blodgett (L
Although thin film fabrication by method B) has been studied, large area thin films are used because the reaction such as substitution of hydrophilic groups / hydrophobic groups is complicated and the control of surface pressure when obtaining thin films is extremely difficult. Hard to get. Further, since a solvent is used also in the polymerization process and the like, contamination of impurities still poses a problem.

On the other hand, in response to such a wet process, a vapor deposition polymerization method (vacuum vapor deposition polymerization method) has been proposed in which a monomer is evaporated in a vacuum chamber and polymerized on a substrate to directly obtain a polymerized film. . Since this method is a dry process and is a process under non-thermal equilibrium, it has been expected to obtain a polymer film which cannot be obtained by a conventional chemical wet process. However, in practice, this evaporation polymerization method has a small degree of freedom during preparation, and it has been difficult to impart special functionality to a thin film.

Under such circumstances, next-generation LSI
For the development of LCDs and large-screen LCDs, it has been desired to realize new practical technical means capable of overcoming the problems of the conventional techniques. Therefore, the present invention has been made in view of the above circumstances, and it is possible to produce a polymer film having extremely thin, excellent surface flatness and high chemical purity, which cannot be obtained by the conventional technique. It aims to provide a new method.

[0006]

In order to solve the above-mentioned problems, the present invention is characterized in that a plurality of ionized molecules are alternately laminated and vapor-deposited on a substrate to form an oriented organic film. A method for manufacturing an oriented organic film is provided.

[0007]

The method of the present invention relates to the alternate vapor deposition polymerization method using an ion beam, which is characterized by the above-mentioned constitution,
By alternately depositing ionized molecules,
It is possible to obtain an organic thin film having good crystallinity and orientation. So far, as a method of forming a thin film of a metal or a compound thereof, a so-called ion plating method or vapor deposition in a crucible has been used as a means for forming a thin film having a high film adhesion strength by vapor deposition and good crystallinity. There is known a cluster ion beam method in which a material is evaporated and blown out as a cluster (a mass of atoms), which is ionized and accelerated to hit the substrate. Therefore, in the present invention, these methods are developed to ionize a plurality of types of monomers forming an organic film, control an interaction between a substrate and a monomer molecule by applying an acceleration voltage, and crystallinity / orientation of a polymer film. In order to improve the property, the monomers are alternately laminated and vapor-deposited to produce a molecular orientation control organic film as an ion beam alternating vapor deposition polymer film. By this method, it is possible to directly form a polymer film having a liquid crystal alignment force on a substrate without surface alignment treatment.

Various types of monomer molecules are included in the method of the present invention. Selected according to the type of the target organic film, for example, a polymerized organic film is a condensation system such as polyimide, polyamide, polyester, polycarbonate, polyurea, polycarbamate, polyether, polysulfide, polyamine, polysulfoxide, or polyacrylate, The monomer is selected according to the addition system such as polymethacrylate and polyfluorocarbon.

Examples of the monomer include carboxylic acids, carboxylic acid esters, aldehydes, ketones, amines, amides, nitriles, isocyanates, carbonates, sulfides, epoxides, sulfoxides, various olefinic halides, carboxylic acids, esters, hydroxides, Organic monomers such as ethers, nitrites, amines will be used.

In the present invention, at least two kinds of these monomers are used to enable the production of an organic film having a controlled molecular orientation. For its production, alternating vapor deposition is performed by sublimation and evaporation of monomer molecules, ionization thereof, and acceleration according to the conventionally known ion plating method and cluster ion beam method. A crucible or the like depending on the type of monomer can be used.

After vapor deposition, the substrate may be heated, if necessary, to promote the formation and modification of the polymer bonding structure. More specifically, for example, according to the present invention, it is possible to form a polyimide film having excellent molecular orientation. This is also a remarkable point of the present invention. A polyimide thin film is formed, and it is possible to confirm the effect of making the polyimide thin film ultra-thin and molecular orientation by irradiation of an ion beam, and the electrical and optical characteristics of the polyimide thin film.

Further, according to the present invention, an extremely thin polymer film having excellent surface flatness and high chemical purity, which cannot be obtained by the conventional spin coating method, can be produced. As a result of these, it is considered that a highly reproducible liquid crystal alignment film is formed, an ultra-flat interface is formed in a next-generation LSI, an extremely thin insulating film is formed, and the device is applied to a molecular device.

To further explain, according to the method of the present invention: 1. An organic film whose orientation is controlled in the direction perpendicular to the substrate can be produced. 2. An organic film having a liquid crystal aligning force can be directly formed. It realizes a remarkable feature that the liquid crystal alignment direction can be controlled by the incident direction of the monomer beam, which is not obtained by the conventional method. With such characteristics, it becomes possible to control the film thickness in the multilayer structure. Further, there is no need for liquid crystal alignment treatment such as rubbing, the manufacturing process of the liquid crystal device is simplified, and moreover, a uniform alignment state can be realized over a large area. Furthermore, since the orientation of liquid crystal molecules can be freely controlled, the blocking and transmission of polarized light can be easily controlled, and application to electronic, optical and magnetic devices becomes possible.

The present invention will be described in more detail with reference to the following examples.

[0015]

EXAMPLE 1 FIG. 1 is a schematic view illustrating an apparatus which can be used in the method of the present invention. In this example, two ion sources are provided for two types of monomers so that the vapor deposition conditions can be set independently.

In the ion source, the resistance heating heater heats the crucible, sublimates the monomer charged in the crucible, and ionizes it in the ionization section above the crucible. Ionization is performed by the electron impact method. After that, the ion beam is accelerated by the voltage Va ′ and is irradiated onto the substrate. A heater for controlling the substrate temperature and annealing the polymer film is provided above the substrate holder. A rate monitor is provided between the ionization section and the substrate so that vapor deposition can be performed while monitoring the evaporation rate. A shutter is provided above the two kinds of ion sources, which enables simultaneous vapor deposition polymerization and alternate vapor deposition polymerization. In the case of alternate vapor deposition polymerization, it is important to prepare under the boundary conditions (substrate temperature, vapor deposition rate, etc.) in which the monomer physically adsorbs to the substrate.

By using the above apparatus, PMDA (pyromellitic dianhydride) and OD are used as two kinds of monomers.
A polyimide (PI) thin film was manufactured using A (oxydianiline). PMDA puts the crucible above 210 ° C,
When ODA is heated to 180 ° C. or higher, the vapor deposition rate rapidly increases. Therefore, in order to control the deposition, the PMDA crucible is at 175 to 200 ° C., and the ODA crucible is at 165.
It was set to ~ 170 ° C.

The substrate temperature was set to 45 to 50 ° C., which is the limit temperature at which the monomer can be condensed. After the vapor deposition, the substrate temperature was set to 300 ° C. for 30 minutes for imidization. On the board
Si, glass and NaCl were used. F of the obtained vapor deposition film
FIG. 2 shows a T-IR spectrum. Further, FIGS. 3A and 3B show electron beam diffraction images of thin films produced by simultaneous vapor deposition and alternate vapor deposition, respectively. It is known that crystallized PI has an orthorhombic structure as shown in FIG. The electron diffraction image of the obtained PI thin film is a ring pattern, and it is considered that the PI thin film has a polycrystalline or uniaxially oriented structure. When indexing is performed on each of FIGS. 3A and 3B, both are (001).
Perpendicular to the plane. That is, in the obtained PI thin film, the main chain c-axis is uniaxially oriented in the direction perpendicular to the substrate. Also,
It can be seen that many rings clearly appear in FIG. 3B as compared with FIG. 3A, and the c-axis orientation becomes remarkable in the case of the alternating vapor deposition polymerization method.

Looking at the adhesion rate of PMDA and ODA to the substrate, when the substrate temperature is about 50 ° C., the same kind of monomer does not adhere, but different kinds of monomers adhere to each other by the polymerization reaction. Irradiation was performed to carry out laminated growth. FIG. 5 shows the relationship between the number of irradiations on the PMDA side and the film thickness value shown on the rate monitor. The irradiation time is 1 minute. For example, between the scales 24 and 25 on the horizontal axis is 24
Corresponding to the 1st irradiation of PMDA for 1 minute (the shutter on the PMDA side is open), PM on the 25 scale
The shutter on the DA side is closed, and the ODA monomer is 1
Irradiated for a minute. When the scale on the horizontal axis was closed, the film thickness increased due to re-evaporation, and the values at which the shutter closed were aligned on a straight line. FIG. 6 shows the relationship between the number of irradiations and the film thickness value.
It can be seen that the film thickness value increases in proportion to the number of irradiations.

Here, as shown in FIG. 7, in the thin film formation process by the alternate vapor deposition polymerization method, the excess monomer after the monomer for one layer is polymerized to form a film is used as long as the shutter is open. Although it adheres to the top (the rising part in FIG. 5),
Since the substrate temperature is high after the shutter is closed, it is considered that the substrate is desorbed from the surface by re-evaporation (reduced portion in FIG. 5). However, when the ODA and PMDA are alternately irradiated once, the film thickness grows further, and therefore it is considered that the decrease stops at the film thickness value increased by a constant value as compared with before the shutter is opened as shown in FIG. When the main chain is oriented in the vertical direction with respect to the substrate, 16Å grows for one deposition (Fig. 8). The slope of the straight line in FIG. 6 is considered to represent this. A MIS device was actually manufactured, a capacitance value was measured using a PI thin film formed by an alternate vapor deposition polymerization method for an insulating layer, and a comparison with a capacitance value expected from the number of alternate vapor depositions was as shown in Table 1. When the number of alternate vapor depositions is 7, the two are in good agreement.

[0021]

[Table 1]

Example 2 In Example 1, a liquid crystal cell was actually assembled using polyimide thin films formed by alternate vapor deposition polymerization. The polyimide thin film produced by the alternate vapor deposition polymerization method orients liquid crystal molecules. It was In this case, the alignment direction of the liquid crystal was a direction perpendicular to the incident directions of the two monomer beams (FIG. 9). Further, when the degree of liquid crystal orientation of the produced liquid crystal cell was examined by dichroic ratio, the results shown in Table 2 were obtained, showing that the liquid crystal is oriented.

[0023]

[Table 2]

Example 3 Using the alternate vapor deposition polymerization method of Example 1, M as shown in FIG.
An IS element was prepared and a BT test was conducted to examine the presence of impurities in the polyimide thin film. The gate electrode was Au and the lower electrode was Al to form an ohmic contact. As a result, as shown in FIGS. 11A and 11B, almost no hysteresis was observed in the MIS device using the PI thin film (FIG. 11A) produced under neutral conditions. Further, the shift of the C-V curve before and after the BT test is greatly shifted when the PI thin film made neutral (FIG. 11A) is used, but the PI thin film made by ionization and acceleration ( When FIG. 11B is used, there is almost no shift. All of these results show that when produced under ionizing conditions, the PI film has very few mobile impurity ions.

Of course, PMDA and ODA were used as the two kinds of monomers in the above examples, but the present invention is not limited to these and may be appropriately selected according to the boundary conditions such as the substrate temperature and the vapor deposition rate.

[0026]

As described in detail above, according to the present invention, it is possible to obtain an organic thin film having good crystallinity and orientation by alternately laminating and vaporizing ionized molecules using an ion beam. Further, according to the method of the present invention, it is possible to produce a liquid crystal alignment film having high reproducibility, to form an ultra-flat interface in a next-generation LSI, to form an extremely thin insulating film, and to apply it to a molecular device.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a device configuration for a method of the present invention.

FIG. 2 is a relationship diagram showing an FT-IR spectrum of a polyimide thin film as an example.

FIG. 3 is an explanatory diagram showing an electron diffraction image of a polyimide thin film as an example.

FIG. 4 is an explanatory diagram showing a crystal structure of a polyimide thin film as an example.

FIG. 5: Pyromellit dianhydride (P
It is a relational figure which shows the behavior of MDA) beam vapor deposition film thickness value.

FIG. 6 is a diagram showing the relationship between the number of alternating depositions of a polyimide thin film and the film thickness value according to the film thickness step shape.

FIG. 7 is a prediction principle diagram of the alternate vapor deposition method of the present invention.

FIG. 8 is an explanatory diagram of an alternating vapor deposition polymerization method in Example 2.

FIG. 9 is a diagram showing a relationship between a liquid crystal alignment state of a polyimide thin film and a monomer beam incident direction by alternating vapor deposition polymerization method and spin coating method.

FIG. 10 is an explanatory diagram showing a structure of an MIS element as an example.

FIG. 11 is a relationship diagram showing a state of a BT test in the MIS element.

Claims (1)

[Claims] 1. A method for producing a molecularly oriented organic film, which comprises depositing a plurality of ionized molecules alternately on a substrate to form an oriented organic film.