JPH0635360B2 - Method for manufacturing single crystal aluminum nitride film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] This invention uses a combination of aluminum vapor deposition and so-called low energy nitrogen ion irradiation to form a single crystal (hexagonal single crystal, hereinafter the same) aluminum nitride film on a substrate. It relates to the method of making above.

[Conventional technology]

For example, it is used as a substrate material for hybrid ICs, and has high thermal conductivity and high electrical insulation as a substitute for beryllia (BeO), which has a problem in that the raw material is toxic. Recently, single crystal aluminum nitride has attracted attention.

In that case, the conventional method for producing a single crystal aluminum nitride film using nitrogen ion implantation is to implant nitrogen ions directly into aluminum metal or aluminum single crystal with energy of about 50 to 100 KeV.

[Problems to be solved by the invention]

However, in the conventional method as described above, although a single crystal aluminum nitride film can be prepared for the time being, there are many problems as follows.

Since only nitrogen ions are implanted, in other words, only nitrogen ions can be controlled, and the controllability of the Al / N (Al: aluminum, N: nitrogen, the same applies hereinafter) is poor.

The range (average projective range) of nitrogen ions in aluminum metal (or single crystal) is small (for example, 100 Ke
The thickness of the obtained aluminum nitride single layer is small, and most of them are the aluminum single layer and the mixed layer of aluminum and aluminum nitride.

Since the energy of nitrogen ions is high, damaged parts such as defects are likely to occur in the aluminum nitride crystal. When such a damaged portion occurs, the electrical insulation property and mechanical strength of the film deteriorate. However, if the energy of the nitrogen ions is simply lowered, the range of the nitrogen ions in the metal becomes small, and as mentioned above, the thickness of the aluminum nitride single layer becomes smaller and smaller.

Therefore, an object of the present invention is to provide a method for manufacturing a single crystal aluminum nitride film capable of solving the above problems.

[Means for solving problems]

According to the method for producing a single crystal aluminum nitride film of the present invention, aluminum vapor deposition and nitrogen ion irradiation are performed on a substrate in a vacuum, the energy of the nitrogen ion is within a range of 0.5 to 40 KeV, and the substrate surface temperature at the time of ion irradiation. Is performed at a temperature of 350 ° C. or lower.

[Action]

Conventionally, it was thought that a single crystal aluminum nitride film could not be formed in a so-called low energy region where the energy of nitrogen ions was 40 KeV or less. However, by using aluminum vapor deposition and nitrogen ion irradiation in combination, the energy of nitrogen ions is within the range of 0.5 to 40 KeV, and the substrate surface temperature at the time of ion irradiation is 350 ° C. or less, it is possible to obtain a high-quality single substrate with few damaged parts. A crystalline aluminum nitride film was obtained.

〔Example〕

FIG. 1 is a schematic view showing an example of an apparatus for carrying out the method for producing a single crystal aluminum nitride film according to the present invention. A substrate 3 made of, for example, silicon, glass, metal, ceramics, etc., is attached to a holder 1 having a heater 2 inside a vacuum container (not shown).
The evaporation source 4 and the ion source 7 are arranged toward the.
The evaporation source 4 is, for example, an electron beam evaporation source, has aluminum metal 5 as an evaporation material, and aluminum vapor 6 from the evaporation source 4 is vapor-deposited on the substrate 3. The ion source 7 is, for example, a bucket type ion source, and irradiates the substrate 3 with nitrogen ions 8. Incidentally, 9 is a film thickness monitor for film thickness control.

At the time of film formation, the inside of the vacuum container is, for example, 10 ⁻⁷ Torr.
After exhausting to a certain degree, the substrate 3 is preferably heated by, for example, the heater 2. The surface temperature of the substrate 3 at that time is preferably about 150 ° C. at the maximum. The substrate 3 is heated to promote the reaction between aluminum and nitrogen ions to facilitate their bonding, to form a film while annealing the substrate 3, to promote the diffusion of nitrogen ions, and the nitrogen ions to be introduced into the aluminum. It is easy to enter. The maximum temperature is set to about 150 ° C. in order to prevent the base temperature from becoming too high because the surface temperature of the substrate 3 at the time of ion irradiation needs to be suppressed to 350 ° C. or lower for the reason described later.

Then, with the substrate 3 heated as described above, the evaporation source 4
And aluminum ion irradiation by the ion source 7 are alternately or simultaneously performed under the following conditions.

That is, the energy of the nitrogen ions 8 is set to 0. 0 in order to reduce the damaged portion in the produced single crystal aluminum nitride film.
5/40 KeV, and more preferably 0.5-5 KeV
And

The surface temperature of the substrate 3 at the time of ion irradiation is 350 ° C. or lower. This is because since the transformation point of aluminum is about 450 ° C., the thermal damage to the single crystal aluminum nitride produced with a difference from the temperature is minimized.

The surface temperature of 350 ° C. corresponds to about 2.5 W / cm ² when converted into the implantation power of the nitrogen ions 8 into the substrate 3, so the energy of the nitrogen ions 8 is 0.5 to 5 Ke.
In the case of V, the implantation amount of nitrogen ions 8 is 10 ¹⁶ to 10 ¹⁸
Ions / cm ² are preferred. If this is made too small, it will take a long time for film formation.

When vapor deposition and ion irradiation are performed alternately, the thickness of the aluminum vapor deposition film produced by one vapor deposition should be determined by considering the range of nitrogen ions 8 to be injected later and the sputtering effect of aluminum by nitrogen ions 8. It is preferable to select. This is because the single layer of aluminum nitride is formed within the range of the nitrogen ions 8. For example, when the energy of the nitrogen ions 8 is 0.5 to 5 KeV, the range of the nitrogen ions 8 is about 80 Å or less, so that the film thickness during one vapor deposition is preferably about 100 Å or less. Therefore, in the case where the aluminum nitride layer having a desired film thickness cannot be obtained by one-time vapor deposition and ion irradiation, both may be alternately repeated a plurality of times until it is obtained. However, when vapor deposition and ion irradiation are performed at the same time, it is possible to obtain an aluminum nitride layer having a desired film thickness by continuing both for a predetermined time.

FIG. 2 is a diagram showing an example of a film forming process in the apparatus of FIG. In this example, vapor deposition and ion irradiation are performed alternately. Under the above-described conditions, first, the aluminum vapor 6 is vapor-deposited on the substrate 3 to form the aluminum vapor-deposited film 10 on the surface thereof, and the aluminum vapor deposition is further performed. The film 10 is irradiated with nitrogen ions 8 to obtain a single crystal aluminum nitride film 11. When the required film thickness cannot be obtained by one-time vapor deposition and ion irradiation, vapor deposition and ion irradiation are repeated until the required film thickness is obtained.

By the method as described above, it was possible to obtain a good quality hexagonal single crystal aluminum nitride film in a low energy region which was considered impossible until now. An example of the electron beam diffraction pattern of the film is shown in FIG. In this case, the film forming conditions are as follows: aluminum deposition amount is 100Å, nitrogen ion energy is 5 KeV, and nitrogen ion implantation amount is 1 × 1.
It was 0 ¹⁷ ions / cm ² .

Finally, the features of the above-described method are as follows.

When forming the single crystal aluminum nitride film, the individual processing conditions of aluminum vapor deposition and nitrogen ion irradiation can be selected and combined relatively freely, and therefore the controllability with respect to the Al / N composition ratio is good. Therefore, for example, by setting the vapor deposition film thickness corresponding to the range of the nitrogen ions 8, there is no aluminum that is not combined with nitrogen when viewed in the depth direction, that is, the total thickness is a single crystal aluminum nitride film. It is also possible to do so.

A single crystal aluminum nitride film having a large film thickness can be easily obtained. In particular, if aluminum vapor deposition and nitrogen ion irradiation are alternately repeated a plurality of times, a desired film thickness can be suppressed while suppressing an increase in the surface temperature of the substrate 3, in other words, suppressing thermal damage to aluminum nitride. The single crystal aluminum nitride film can be easily obtained.

Since the energy of the nitrogen ions 8 is smaller than that in the conventional method, the occurrence of damaged portions such as pinholes inside the aluminum nitride film and defects inside the crystal can be reduced, and a high quality single crystal aluminum nitride film can be obtained.

Since it is not necessary to use expensive aluminum single crystal as in the conventional case, the film can be formed at low cost.

Since the low-energy nitrogen ions 8 are used, the cost of the ion source 7 is low, and the operation and handling of various devices including the ion source 7 are easy.

〔The invention's effect〕

As described above, according to the present invention, a good quality hexagonal single crystal aluminum nitride film with few damaged portions can be obtained. Moreover, the controllability of the Al / N composition ratio is good, and it is possible to obtain a single-crystal aluminum nitride single layer having a large thickness.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of an apparatus for carrying out the method for producing a single crystal aluminum nitride film according to the present invention. FIG. 2 is a diagram showing an example of a film forming process in the apparatus of FIG. FIG. 3 is an electron beam diffraction diagram of a single crystal aluminum nitride film obtained by the method of the example. 2 ... Heater, 3 ... Substrate, 4 ... Evaporation source, 6 ... Aluminum vapor, 7 ... Ion source, 8 ... Nitrogen ion, 1
1 ... Single crystal aluminum nitride film

Claims (2)

[Claims] 1. A substrate is subjected to aluminum vapor deposition and nitrogen ion irradiation in vacuum, and the nitrogen ion energy is 0.5.
A method for producing a single crystal aluminum nitride film, which is carried out in a range of -40 KeV and a substrate surface temperature at the time of ion irradiation of 350 ° C or lower. 2. The method for producing a single crystal aluminum nitride film according to claim 1, wherein aluminum vapor deposition and nitrogen ion irradiation on the substrate are alternately repeated a plurality of times.