JPS6235514A - Molecular beam crystal growth method - Google Patents

Abstract

PURPOSE:To exclude the use of an indium solder and to obtain the uniformity in a plane of a grown film by interposing a thermal conductive plate having thermal conductivity anisotropy in which thermal conductivity is large in the plane direction between a substrate and a heater through a gap on the substrate. CONSTITUTION:A heating plate 7 having thermal conductivity anisotropy that thermal conductivity is large in plane direction is interposed between a substrate S and a heater 6 for heating the substrate S through a gap G on the substrate S, and a growing substance is accumulated on the substrate S. The material of the plate 7 is preferably pyrolytic boron nitride (pBN). Since thermal transfer from the plate 7 to the substrate S is by heat radiation due to the presence of the gap G, it is not necessary to use an indium solder. Since the plate 7 has thermal conductivity anisotropy that the thermal conductivity is large in plane direction, even if the planar distribution of the heat received from the heater 6 is irregular, the temperature distribution of the plane opposed to the substrate S becomes uniform, the uniformity in the plane of the temperature of the substrate S is obtained to obtain a preferably grown film.

Description

[Detailed Description of the Invention] [Summary] In a method for supporting a substrate on which a growth substance is deposited in a molecular beam crystal growth method, the thermal conductivity between the substrate and the heater has a large thermal conductivity anisotropy in the in-plane direction. By interposing the heat conductive plate with the substrate with a gap therebetween, the use of indium solder can be eliminated and the in-plane uniformity of the grown film can be ensured.

[Industrial application field]

Molecular beam crystal growth (MBE) allows the thickness of a grown film deposited on a substrate to be controlled by, for example, about 10 people, and it is also possible to continuously grow a multilayered film. Due to these outstanding characteristics, in recent years, it has attracted attention in the crystal growth of compound semiconductors used in the formation of semiconductor devices.

It is desired to ensure in-plane uniformity of the grown film and to be able to handle the substrate in a manner that does not contaminate the grown film after growth.

[Conventional technology]

MBE is 1. As shown in the side sectional view of FIG. 5, in the ultra-high vacuum chamber 1, the molecular beams of the growth material radiated from the molecular beam source 3 are directed to the heated substrate S supported by the substrate supporter 2, as indicated by the arrow. This is a crystal growth method in which a crystal growth film is formed by irradiating the substrate S to deposit the growth material on the surface of the substrate S.

Conventionally, the substrate S is supported at this time as shown in the side cross-sectional view of FIG.

In the figure, 4 is a disk-shaped substrate support plate made of molybdenum (hO) and attached to the front of the substrate support 2;
5 is indium solder for attaching the substrate S to the substrate support plate 4;
6 is a heater arranged behind the substrate support plate 4.

The size of the substrate support plate 4 is, for example, an outer diameter of about 601 mm and a thickness of about 2 to 31 m.

The heater 6 heats the substrate S via the substrate support plate 4 and the indium solder 5, but the temperature distribution within the substrate support plate 4 is approximately uniform, and the heat is transferred to the substrate S by thermal conduction. The in-plane temperature distribution is approximately equal. In-plane uniformity of the temperature of the substrate S is necessary to obtain in-plane uniformity of the grown film.

[Problem that the invention seeks to solve]

Attaching the substrate S to the substrate support plate 4 using indium solder 5 involves applying the indium solder 5 to the substrate S and attaching it to the substrate support plate 4, but this application requires skill. , indium solder 5 between the substrate S and the substrate support plate 4
It may not be completely filled.

In this case, unevenness in heat transfer from the substrate support plate 4 to the substrate S causes bell-shaped irregularities (so-called cross hatches) on the surface of the grown film, making it impossible to obtain a uniform grown film.

Further, the substrate S is a compound semiconductor such as gallium arsenide (Ga).
If the substrate S is fragile such as As), the substrate S
This is particularly noticeable when the substrate S is large in size, resulting in a yield problem.

Furthermore, in the above method using indium solder 5, it is necessary to remove the indium solder 5 from the substrate S after crystal growth, and etching and roughening are performed for this purpose, but the important grown film is contaminated during this process. There is a problem.

[Means for solving problems]

FIG. 1 is a side sectional view showing the gist of the present invention.

As shown in FIG. 1, the above problem is such that a heating plate 7 having a large thermal conductivity anisotropy in the plane direction is placed between the substrate Fis and the heater 6 that heats the substrate S. Gap G
This problem is solved by the molecular beam crystal growth method of the present invention, in which a growth material is deposited on a substrate S-H by providing an intervening film.

According to the present invention, the material of the heating plate 7 is preferably pyrolytic boron nitride (pBN).

[Effect]

In the method of the present invention, the heater 6 heats the substrate S through the heating plate 7 and the gap G, but due to the existence of the gap G, heat transfer from the heating plate 7 to the substrate S is by thermal radiation. There is no need to use indium solder as in the past.

This eliminates the problems associated with conventional methods, such as damage to the substrate when applying indium solder, occurrence of cross-hatching due to uneven heat transfer, and contamination of the grown film when removing indium solder.

Furthermore, since the heating plate 7 has a large thermal conductivity anisotropy in the plane direction, even if the distribution of the heat received from the heater 6 in the plane direction is uneven, the temperature distribution on the surface facing the substrate S is The temperature of the substrate S becomes uniform, and the in-plane uniformity of the temperature of the substrate S is ensured.

In particular, when a pBN plate is used as the heating plate 7, the thermal conductivity in the plane direction is 20 to 30 times the thermal conductivity in the direction perpendicular to the plane at a heating temperature of, for example, 500 to 800°C during crystal growth. , the in-plane temperature uniformity of the substrate S is extremely excellent, and a grown film with good in-plane uniformity can be obtained.

〔Example〕

FIG. 2 shows an embodiment of the method of the invention on the side Vj? 3 is an exploded perspective view of essential parts of the embodiment shown in FIG. 2, and FIG. 4 is a characteristic diagram of an example of a grown film showing a comparison between the embodiment shown in FIG. 2 and the conventional method shown in FIG. be.

In FIGS. 2 and 3, 2 is the substrate support shown in FIG.
A heating plate made of BN& (for example, "Bolloy" slope made by Union Carbide), 8 a substrate support ring made of Mo, 9 a pB
A guide ring is made of N and sets the gap between the substrate S and the pA plate 7, and lO is an annular presser made of tungsten (W) or tantalum (Ta) that fixes the guide ring 9 and the heating plate 7 to the substrate support ring 8. It is a spring.

After the guide ring 9, the substrate S, the heating plate 7 and the pressing spring 10 are inserted into the substrate support ring 8, a sixth
It is fixed in the same manner as the substrate support plate 4 shown in the figure.

In this embodiment, the step dimension a in the guide ring 9 is determined by heating v! Gap between j and 7
This is the sum of approximately 50 μm, that is, approximately 500 μm. What is important here is to set the size of the gap G so that the substrate S and the heating plate 7 do not come into contact with each other, and the size of the gap G is not limited to the above-mentioned 50 μm.

If the thickness of the substrate S or the dimensions of the gap G are different from those described above, it is sufficient to prepare a guide ring 9 having a corresponding step dimension a.

In the case of this configuration, an intervening member that can actively maintain the gap G is not provided, but in the MBE that was used in this embodiment, the substrate S is oriented slightly downward as shown in FIG. The gap G is maintained by its own weight. If this is difficult, an intervening member made of Mo or the like may be provided around the substrate S.

Further, in this configuration, the gap G is a substantially closed space. This serves to prevent a substance with a high vapor pressure, such as arsenic (8S) in GaAs, from evaporating from the back surface of the heated substrate S and causing the surface to become rough.

The heat transfer situation when the substrate S is heated by the heater 6 with the above configuration is as described above. Heating plate 7 in this case
Thermal conductivity anisotropy is a characteristic of pBN produced by vapor phase growth, whereas boron nitride (BN) produced by powder compaction has no thermal conductivity anisotropy and is
unsuitable for use in

Figure 4 shows the in-plane carrier concentration (Nd) when silicon (St)-doped n-type GaAs is grown on a 2-diameter GaAs substrate using the embodiment shown in Figure 2 and the conventional method shown in Figure 6. This is a characteristic diagram comparing the distribution on one diameter, and the solid line (○
2), and the broken line (x) indicates the conventional method shown in FIG. 6. Note that when using the conventional method, the attachment using indium solder is ensured and cross-hatching is prevented from occurring.

As is clear from this characteristic diagram, the in-plane uniformity of the grown film is better in this example than in the conventional method using indium solder. By the way, when the standard deviation σ is calculated from the data and the average value of σ/Nd, which indicates uniformity, is calculated, the value is 9.0% in the conventional method, but it improves to 6.7% in the example. ing.

Needless to say, since indium solder is not used in the above embodiment, there is no fear of damage to the substrate, occurrence of cross-hatching, or contamination of the grown film.

〔Effect of the invention〕

As explained above, according to the configuration of the present invention, in a method for supporting a substrate on which a growth material is deposited in MBE, it is possible to eliminate the use of indium solder and ensure in-plane uniformity of the grown film, and Problems caused by using solder, such as damage to the board, occurrence of cross hatches,
This has the effect of avoiding contamination of the grown film and making it possible to stably provide a high-quality grown film.

[Brief explanation of drawings]

FIG. 1 is a side sectional view showing the gist of the present invention, FIG. 2 is a side sectional view showing an embodiment of the method of the present invention, FIG. 3 is an exploded perspective view of a main part of the embodiment shown in FIG. Figure 2 is a characteristic diagram of a grown film example showing a comparison between the illustrated embodiment and the conventional method, Figure 5 is a side sectional view showing the main structure of MBE, and Figure 6 is a side view showing the conventional substrate support method. It is a sectional view. In the figure, 2 is a substrate supporter, 4 is a substrate support plate, 5 is indium solder, 6 is a heater, 7 is a heating plate, 8 is a substrate support ring, 9 is a guide ring, 10 is a pressing spring, G is a gap, and S is the substrate, and . Ascendance 2 z 1p direction 1st direction and also Komaraigata 2 toggle ratio and exchange date, Suga 1 (
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Claims (1)

[Claims] 1) A substrate (S) and a heater (6) that heats the substrate (S)
A heating plate (7) having a large thermal conductivity anisotropy in the plane direction is interposed between the substrate (S) and the substrate (S) with a gap (G) between the substrate (S) and the substrate (S). A molecular beam crystal growth method characterized by depositing a growth material on top. 2) The molecular beam crystal growth method according to claim 1, wherein the material of the heating plate (7) is pyrolytic boron nitride.