JPS60240119A - Molecular beam crystal growth - Google Patents

Abstract

PURPOSE:To enable preventing the roughness of the back surface due to lack of an element in a substrate and detecting the heating temperature of the substrate correctly with a pyrometer by irradiating radiation on a high melting point metal coated on the back surface of the substrate which is required of crystal growth on the surface to heat the substrate for growth. CONSTITUTION:A substrate 4 is previously coated on the back surface of the substrate 4 with a high melting point metal film 12, e.g., such as molybdenum or tungsten by sputtering, etc. and the substrate 4 is heated for crystal growth by the radiation of a heater 6 located on the back. This method enables to develop a later process without removing the high melting point metal film 12 and even if the substrate 4 is made of, e.g., GaAs, the roughness of the back surface due to lack of As is not generated and a pyrometer 8 detects the heating temperature of the substrate 4 correctly.

Description

DETAILED DESCRIPTION OF THE INVENTION fa) Technical Field of the Invention The present invention relates to a method for growing molecular beam crystals, and more particularly to a method for heating a substrate for growing crystals.

fb) Background of the Technology In the manufacture of semiconductor devices, crystal growth is an important process, and its success or failure influences the characteristics of the semiconductor element formed.

Although the vapor phase growth method and the liquid phase growth method are often used for this crystal growth, in recent years, the molecular beam crystal growth method (MBE method) has been attracting attention for the crystal growth of compound semiconductors.

In the molecular beam crystal growth method, as shown schematically in a plan view in Figure 1, constituent elements of the crystal to be grown are placed in an electric cavity L in an ultra-high vacuum (for example, about 10" Torr). The crucible 2 is heated and the molecular beam 3 that comes out is transferred to the substrate 4.
A method of epitaxially growing on the substrate 4 by applying
Molecules that are not captured by the substrate 4 are carried away by the vacuum system, and the surface of the substrate 4 is constantly supplied with fresh molecules. At this time, the intensity of the molecular beam 3 is determined by the heating temperature of the crucible 2, the shutter 5 that does not apply the molecular beam 3 to the substrate 4 is mechanically opened and closed, and the heating temperature of the substrate 4 is determined by the heat generated by the heater 6.
The heat generation is controlled by the output signal of a pyrometer 8 that detects the heat rays 7 emitted from the substrate 4.

For this reason, the molecular beam crystal growth method has the following outstanding features.

(2) Since the thickness of the growth layer is uniform and the growth rate is slow, fine control of the film thickness, for example, by about 10 people, is possible.

(2) By opening and closing the shutter 5, it is possible to continuously grow crystals in a multilayer structure.

(C) Prior Art and Problems In the molecular beam crystal growth method shown in FIG. 1, the substrate 4 was conventionally held and heated as shown in FIG. 2 (plan view). That is, a table 9 made of a heat-resistant metal such as molybdenum is provided at the position of the substrate 4, and in front of the table 9 the substrate 4 is pasted with a bonding metal 10 such as indium that becomes liquid when heated. The table 9 was heated to heat the substrate 4.

In this method, crystal growth can be performed well, but since the bonding metal 10 is attached to the back surface of the substrate 4 taken out after the growth, which is a problem in the subsequent process, the bonding metal 10 is removed by, for example, polishing. Therefore, there are problems in terms of quality and process for mass production of semiconductor devices.

As an improvement measure for this, there is a method as shown in FIG. 3 (plan view) in which the joining metal 10 is not used. This is a method of holding the substrate 4 by locking the end of the substrate 4 to the holder 11 without using the table 9 shown in FIG. 2, and heating the substrate 4 with radiation from the heater 6 located behind it. It is.

This method eliminates the problem of the bonding metal 10, but
For example, in the case of gallium arsenide (GaAs), the heating temperature of the substrate 4 is about 600 to 700°C, so there is a problem that arsenic (As) escapes from surfaces other than the growth surface during the growth period, resulting in roughening of the back surface. , pyrometers that detect temperatures of this level measure heat rays with a wavelength of about 2 μm, and GaAs
Since it is transparent to the heat rays, the pyrometer 8
Since the temperature of the heater 6 is detected rather than the temperature of the substrate 4, there is also the problem that it is difficult to control the heating temperature of the substrate 4.

+d) Object of the Invention In view of the above-mentioned conventional problems, the object of the present invention is to avoid the use of auxiliary materials that require removal after growth, and yet to
To provide a molecular beam crystal growth method that does not cause roughness on the back surface due to removal of components of the substrate even when using As, and allows a pyrometer to accurately detect the heating temperature of the substrate.

(e) Structure of the Invention The above object is to deposit a high melting point metal on the back surface of a substrate on which crystals are to be grown, and to heat the substrate during the growth by applying radiation to the deposited high melting point metal. This is achieved by a molecular beam crystal growth method characterized by the fact that it is carried out using

If the material deposited on the back side of the substrate is a high melting point metal,
There is no need to remove the material since it would be a manufacturing problem in the post-growth process if the substrate was left coated with the material.

Furthermore, since the deposited high melting point metal prevents the components of the substrate from coming off, the back surface does not become rough. Furthermore, since the deposited high melting point metal is opaque to the heat rays measured by the pyrometer and is in close contact with the substrate, the temperature of the substrate is equal to the temperature of the high melting point metal, and the substrate is opaque to the heat rays. Even if the transparent pyrometer measures the temperature of the high melting point metal, it will accurately detect the heating temperature of the substrate.

In this way, it is possible to eliminate quality and process problems in mass production of semiconductor devices associated with this growth process.

(fl Embodiments of the Invention Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same reference numerals indicate the same objects throughout the drawings.

FIG. 4 is a plan view schematically showing one embodiment of the method of the present invention for holding and heating a substrate, and FIG. 5 is a plan view schematically showing another embodiment.

In the method shown in FIG. 4, a high melting point metal film 12 such as molybdenum or tungsten is previously deposited on the back surface of the substrate 4 by vapor deposition or sputtering, and then the film is deposited in the same manner as shown in FIG. This is a method of growing crystals.

According to this method, as explained above, it is possible to proceed with the subsequent kneeing process without removing the high melting point metal film 12, and even if the substrate 4 is made of GaAs, for example, the back surface due to the removal of As No roughness occurred, and Pyromake 8 was applied to substrate 4.
Detects the heating temperature correctly.

The method shown in FIG. 5 is a method in which the heater 6 in the method shown in FIG. 4 is replaced with a lamp 13. The solution to the conventional problem is the same as that of the method shown in FIG. 4, and furthermore, since the lamp 13 can be placed outside the vacuum chamber 1 shown in FIG. It has the advantage of being easier.

The inventor of the present application has discovered that the G
Molybdenum with a thickness of approximately 1 μm, which will become the high-melting point metal film 12, is deposited on the aAs substrate 4 by the spacing method, and the impurity concentration with silicon as an impurity is I x 10 using the method shown in FIG.
``Atm/cJ n-type GaAs crystal was grown to a thickness of 2 pm, and the temperature distribution of the substrate 4 during growth was within a range of ±10°C as measured by the pyrometer 8, indicating that it was heated uniformly. It was confirmed that there was no evidence of As missing on the back surface of the subsequent substrate 4, and that the mobility of the grown crystal was at the desired value.

(gl Effects of the Invention As explained above, the structure according to the present invention does not use auxiliary materials that need to be removed after growth, and even if the substrate is made of GaAs, for example, It is possible to provide a molecular beam crystal growth method that does not cause roughness on the back surface due to removal of components and in which a pyrometer can accurately detect the heating temperature of the substrate, and it is possible to improve the mass production of semiconductor devices associated with this growth process. This has the effect of making it possible to eliminate quality and process problems.

[Brief explanation of drawings]

Fig. 1 is a plan view schematically showing the molecular beam crystal growth method, Fig. 2 is a plan view schematically showing the conventional method of holding and heating the substrate, and Fig. 3 is the same (conventional method). FIG. 4 is a plan view schematically showing an embodiment of the method according to the present invention, and FIG. 5 is a plan view schematically showing another embodiment of the method according to the present invention. In the drawing, ■ is a vacuum chamber, 2 is a crucible, 3 is a molecular beam, 4 is a substrate, 5 is a shutter, 6 is a heater, 7 is a hot wire,
8 is a pyrometer, 9 is a table, 10 is a joining metal, 1
Reference numeral 1 indicates a holder, 12 a high melting point metal film, and 13 a lamp.

Claims (1)

[Claims] A molecular beam crystal characterized in that a high melting point metal is deposited on the back side of a substrate on which a crystal is to be grown, and the substrate is heated during the growth by applying radiation to the deposited high melting point metal. Growth l method.