JPH0784640B2 - Method for producing crystalline aluminum nitride - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing aluminum nitride, which utilizes various characteristics such as optical characteristics, electrical characteristics, mechanical characteristics, and thermal conductivity. The present invention relates to a method for producing a thin film suitable for applications, particularly for electronic materials and acoustic materials.

(Prior Art) In recent years, in order to utilize various characteristics of aluminum nitride, such as electric insulation, high thermal conductivity, and wear resistance, for various purposes,
Attempts have been made to form a thin film on the surface of a solid substrate.

Currently, a CVD (Chemical Vapor Deposition) method, a reactive sputtering method, a reactive ion plating method and the like are carried out as a means for forming an aluminum nitride thin film on the surface of a solid substrate.

(Problems to be Solved by the Invention) By the method described above, desired properties, specifically, good light transmission properties, good thermal conductivity, good thermal stability, good chemical stability, good In order to obtain excellent electrical insulation, etc., CV
In the D method, the substrate temperature during film formation needs to be 500 to 1000 ° C. or higher, which greatly limits the substrate material. Also in the ion plating method or the ion plating method, in order to obtain a crystalline aluminum nitride layer having the above-mentioned desired characteristics, it is necessary to perform a crystallization step by heat treatment during film formation or after film formation. If the substrate is damaged or the film is peeled off due to, the manufacturing cost also rises. Further, in these methods, since the aluminum nitride layer is simply deposited on the surface of the substrate, there is a problem of peeling due to thermal cycling or mechanical shock. In addition, there are problems such as poor reproducibility due to difficulty in setting conditions, which is a drawback of film formation, and difficulty in maintaining constant conditions. In particular, optical properties such as transparency greatly change due to slight deviation of film forming conditions, which makes it difficult to apply aluminum nitride to optical parts.

(Means for Solving the Problems) The present invention is to improve the characteristics of aluminum nitride by coating the surface of the substrate with aluminum nitride and then ion-implanting nitrogen from the surface.

In the present invention, the aluminum nitride to be coated may be crystalline or non-quality, and it is not necessary to heat the substrate being coated. In other words, it was possible to produce crystalline aluminum nitride having good reproducibility at room temperature by performing room temperature coating and room temperature injection.

In addition, it is possible to further increase the density by performing a slight heat treatment during coating, during injection, or as a post-treatment.

Further, by implanting nitrogen ions into the vicinity of the interface between the aluminum nitride thin film and the solid substrate or inside the solid substrate with relatively high implantation energy, it is possible to mix the interface between the thin film and the substrate, and aluminum nitride having high adhesiveness A thin film is obtained.

Furthermore, since the ion implantation process is performed in a high vacuum, the aluminum nitride thin film is formed by a process such as reactive sputtering or reactive ion plating in a vacuum so that the ion implantation function and the film forming function are By using the same equipment installed side by side, samples can be processed without exposing them to the atmosphere.

(Operation) The solid substrate or the base film surface is subjected to the usual cleaning and degreasing treatment, for example, the cleaning and degreasing treatment with an organic solvent such as ethanol, acetone or trichloroethylene, and then the aluminum nitride film forming technique according to the present invention is used. Form a film. Next, from the surface of the formed thin film, nitrogen ions are preferably accelerated to 10 to 400 keV (set at a position where the ions are to be added), and preferably implanted at a dose of 1 × 10 ¹⁶ to 2 × 10 ¹⁸ ions / cm ² . Here, the acceleration energy is 10 to 400 keV, which is 10
At keV or less, the sputtering effect remarkably increases and it is difficult to achieve the effect of appropriate ion implantation.When energy exceeding 400 keV is used, a large amount of irradiation damage, dislocation, etc. occur, which adversely affects the thin film and the substrate. This is because the heat treatment for recovery is not preferable because the cost of the apparatus also increases and the cost increases. Further, when the implantation amount up to 1 × 10 ¹⁶ ions / cm ² , the crystallinity of the formed thin film becomes amorphous,
If the amount of implantation is more than this amount, the crystallization or the crystallization axis is changed. Improving the characteristics is not observed even if the implantation exceeds 2 × 10 ¹⁸ ions / cm ² .

(Effect of the Invention) According to the present invention, a crystalline aluminum nitride having improved characteristics is obtained by crystallizing an amorphous material or changing the orientation direction of the crystal axis of aluminum nitride which has already been crystallized. be able to.

Further, it can be formed on the surface of an arbitrary solid substrate with high adhesion of aluminum nitride.

Further, the difficulty of setting conditions and the problem of reproducibility, which are disadvantages of film formation, can be solved, and productivity can be significantly improved. Such effects are obtained and are extremely effective in industry.

(Examples) Examples of the present invention will be described below, but the present invention is not limited to these, and appropriate modes can be adopted as described above.

Example 1 First, a silicon wafer that has been ultrasonically degreased and cleaned with acetone is placed in an ion plating apparatus, and the inside of the chamber is set to 2 × 10 ^−6.
After evacuation to Torr and introducing nitrogen gas to 1 × 10 ⁻⁴ Torr, 99.99% pure aluminum was heated and melted by an electron beam to be evaporated. The vaporized aluminum and nitrogen in the atmosphere are passed through an electron beam shower generated by an electron emission filament for ionization to be ionized or activated, and reacted on a silicon wafer to form a film at a rate of 35 Å / min.
To form an aluminum nitride thin film with a thickness of 750Å.

Next, nitrogen ions are accelerated in an ion implantation chamber with a vacuum degree of 1 × 10 ^-6 Torr at an acceleration energy of 80 keV, and the implantation amount is 5 × 10 ¹⁷ ions / cm 2.
Up to ² injections were made in stages.

Note that all of these treatments were carried out by cooling the substrate holder with water and keeping the substrate temperature during treatment at room temperature.

Curves (a) to (d) in FIG. 1 show the X-ray diffraction intensities of the respective samples thus obtained.

Curve (a) shows the crystal structure of the aluminum nitride thin film before ion implantation. From this curve, it can be seen that the aluminum nitride layer formed under the above film formation conditions is crystalline aluminum nitride oriented in (101). When this aluminum nitride is ion-implanted, the implantation amount of 5 × 10 ¹⁶ ions / cm ² (curve (b)) to 1 × 10 ¹⁷ ions / cm ² (curve (c)) becomes (002) and (101 It can be seen that the state is changed to a state in which aluminum nitride oriented in () is mixed, and the implantation amount is further increased to give a (002) C-axis oriented single crystal at 5 × 10 ¹⁷ ions / cm ² (curve (d)).

Example 2 First, a silicon wafer that has been ultrasonically degreased and cleaned with acetone is placed in an ion plating apparatus, and the inside of the chamber is set to 2 × 10 ^−6.
After evacuation to Torr and introducing nitrogen gas to 1 × 10 ⁻⁴ Torr, 99.99% pure aluminum was heated and melted by an electron beam to be evaporated. The vaporized aluminum and nitrogen in the atmosphere are passed through an electron beam shower generated from an electron emission filament for ionization to be ionized or activated and reacted on a silicon wafer, and a film formation rate of 6.25Å / m
An aluminum nitride thin film with a film thickness of 1000 Å was formed in.

Next, nitrogen ions were accelerated in the ion implantation chamber with a vacuum degree of 1 × 10 ^-6 Torr at an acceleration energy of 80 keV, and the dose was 1 × 10 ¹⁷ ions / cm 2.
Up to ² injections were made.

Note that all of these treatments were carried out by cooling the substrate holder with water and keeping the substrate temperature during treatment at room temperature.

Curves (a) to (c) in FIG. 2 show the X-ray diffraction intensities thus obtained.

The curve (a) represents the crystal structure of the aluminum nitride thin film before ion implantation. From this curve, it can be seen that the aluminum nitride layer formed under the above film forming conditions is in an amorphous state. When this aluminum nitride is ion-implanted, it becomes 5
With an injection dose of × 10 ¹⁶ ions / cm ² (curve (b)), (101)
Crystals that have been changed to crystalline aluminum nitride having the orientation of 1) and the implantation amount is further increased to have orientations of (100), (101) and (102) at 1 × 10 ¹⁷ ions / cm ² (curve (c)). It can be seen that it becomes a crystalline aluminum nitride layer.

From this, using the method for producing an aluminum nitride layer according to the present invention, even if the aluminum nitride thin film produced by film formation is amorphous, it can be crystallized by performing ion implantation, and easily crystallized. It has become possible to produce a crystalline aluminum nitride.

Example 3 First, a slide glass that has been ultrasonically degreased and cleaned with acetone is placed in an ion plating apparatus, and the room is set to 2 × 10 ⁻⁶ To.
After evacuation to rr and introducing nitrogen gas to 1 × 10 ⁻⁴ Torr, 99.99% pure aluminum was heated and melted by an electron beam to be evaporated. The vaporized aluminum and nitrogen in the atmosphere are passed through an electron beam shower generated from an electron emission filament for ionization to be ionized or activated, and then reacted on a slide glass to form a film at a rate of 6.25Å / min.
A thin film of 1250Å aluminum nitride was formed.

Next, nitrogen ions were accelerated in the ion implantation chamber with a vacuum degree of 1 × 10 ^-6 Torr at an acceleration energy of 80 keV, and the dose was 1 × 10 ¹⁷ ions / cm 2.
Up to ² injections were made.

Note that all of these treatments were carried out by cooling the substrate holder with water and keeping the substrate temperature during treatment at room temperature.

FIG. 3 is a graph showing the relationship between the nitrogen ion implantation amount and the light (wavelength 6000Å) transmittance of the sample thus obtained. While the transmittance of unimplanted aluminum nitride is 66%, the implanted aluminum nitride shows a high value of about 94% regardless of the amount of implantation, and shows that it can be easily controlled. At this time, there was no change in the aluminum nitride thin film before and after the implantation.

From this, it can be seen that the use of the method for producing an aluminum nitride layer according to the present invention can greatly expand the application range of aluminum nitride, such as use for an optical component that requires high transparency.

[Brief description of drawings]

1 is a graph showing the X-ray diffraction intensity for each sample obtained in the first example, FIG. 2 is a graph showing the X-ray diffraction intensity for each sample obtained in the second example, FIG. The figure is a graph showing the relationship between the visible light transmittance (transparency) and the nitrogen ion implantation amount of each aluminum nitride sample obtained in the third example.

Claims (6)

[Claims] 1. A method for producing crystalline aluminum nitride, which comprises forming an aluminum nitride thin film and then implanting nitrogen ions. 2. The method according to claim 1, wherein the method for forming the aluminum nitride thin film is a reactive ion plating method. 3. The method according to claim 1, wherein the method for forming the aluminum nitride thin film is a reactive sputtering method. 4. The manufacturing method according to any one of claims (1) to (3), wherein the temperature for forming the aluminum nitride thin film is room temperature. 5. The maximum concentration position of the implanted nitrogen ions is in the vicinity of the interface between the aluminum nitride thin film and the film forming substrate, according to any one of claims (1) to (4). The manufacturing method according to item 1. 6. The manufacturing method according to any one of claims (1) to (5), wherein the nitrogen ion implantation temperature is room temperature.