JPH0620948A - Manufacture of infrared detector material - Google Patents

Abstract

PURPOSE:To enhance crystal uniformity of a grown thin film of HgCdTe when an infrared detector material is manufactured by the HgCdTe as a material by an MBE method. CONSTITUTION:An HgCdTe growing substrate 2 is fixed to a substrate holder 1 through a mirror surface thin plate 10 having the same size as that of the holder 1, and an HgCdTe thin film is grown on the substrate 2 by using an MBE method. Thus, adhesive properties of the substrate 2 are enhanced, and an irregularity in a temperature of the entire surface of the substrate 2 is eliminated. It is interrupted by the plate 10 during growing, HgCdTe is not deposited on the holder 1, reaction of the holder 1 with gallium is prevented, and a decrease in a substrate temperature due to an increase in radiational cooling can be prevented.

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 infrared detector material using a HgCdTe thin film as a material by a molecular beam epitaxy (MBE) method.

[0002]

2. Description of the Related Art FIG. 2 shows a conceptual diagram in the case of growing a HgCdTe thin film by a molecular beam epitaxy (MBE) method. In the figure, the crucible 4 contains the elements Hg and Te of the molecular beam source of HgCdTe and the compound CdTe. By opening the shutter 3, a molecular beam is irradiated from the heated crucible 4 to the growth substrate 2, and HgCdTe grows on the growth substrate 2. An enlarged view around the substrate holder 1 is shown in FIG. In FIG.
The growth substrate 2 is heated by the heater 6 from the back surface of the substrate holder 1.

Since the HgCdTe thin film has a high volatility and has a drawback that mercury in the crystal is removed by heating at 100 ° C. or more in the atmosphere in the process, conventionally, the substrate 2 to be grown is
It was fixed to the substrate holder 1 with a low melting point metal such as gallium (melting point about 30 ° C.) 8.

The substrate to be grown 2 is formed by such a substrate heating device.
Is heated, for example, Journal
of Vacuum Science and Tec
hnology B5 (1987) p.734 W. E.
As described by Hoke et al., The surface of the substrate holder 1 is a rough surface with large irregularities. The radiative cooling from the substrate becomes large, and the temperature displayed on the thermocouple 7 is constant, but the actual substrate temperature (which is almost equal to the surface temperature of the substrate holder) decreases as the growth of the thin film progresses. Are shown (see FIG. 4).

In order to stabilize the substrate temperature, a method has been adopted in which the power supplied to the heater is increased at a constant rate as the thin film is deposited (for example, Journal of of).
Crystal Growth 111 (1991)
898 p. P. Faurele et al.), Whereby the actual substrate temperature was stabilized and controlled so that the thin film crystallinity in the film thickness direction became uniform.

[0006]

However, according to the above-mentioned conventional method, when the growth rate of the thin film is changed or the size (area) of the substrate is different, radiation is emitted from the surface of the substrate holder 1 by radiation cooling. Since the amount of heat applied changes intricately, it was not easy to control the amount of power supplied to the heater 6.

Further, since the substrate holder 1 is made of a material such as molybdenum and has a rough surface with many irregularities, even if an adhesive metal such as gallium is used, the adhesion between the substrate 2 and the substrate holder 1 is poor and the thermal conductivity is high. Was bad. Therefore, HgCdT
e It is not easy to control the substrate temperature during thin film growth, and HgCdT
The crystallinity and reproducibility of the e thin film are extremely low, and there is a problem that the electrical characteristics of the crystal and the infrared detection wavelength band vary from one crystal to another.

In addition, materials such as GaAs and Si may be replaced with HgC.
In the case of dTe growth substrates, it was necessary to heat-treat these substrates at 500 ° C. or higher. At such a high temperature, the gallium and molybdenum substrate holders react with each other to form a compound of gallium and molybdenum on the surface of the substrate holder 1.

[0009] This compound, when used in the same substrate holder 1 from the next time, becomes unsuitable for gallium and causes poor heat conduction to the substrate 2 to be grown. It was necessary to etch the substrate holder 1 with a solution of (+ nitric acid + hydrochloric acid) to remove the compound on the surface of the holder. Therefore, the holder wears out after every etching, and there is a drawback that the holder can be used in the MBE device for a short life.

An object of the present invention is to improve the adhesion between a substrate and a substrate holder and prevent the substrate temperature from lowering during crystal growth to produce an infrared detector material using a high quality HgCdTe thin film. To extend the life of the substrate holder of the MBE device.

[0011]

In order to achieve the above object, in the method for producing an infrared detector material according to the present invention, a molecular beam epitaxy method is used, and the infrared detector is provided on a growth substrate placed on a substrate holder. HgCd as a material
A method of manufacturing an infrared detector material for growing a Te thin film, wherein the entire surface of a substrate holder is covered with a mirror-finish thin plate of the same size as the holder, and a substrate to be grown is brought into close contact with the mirror surface of the thin plate to grow HgCdTe. It is a thing.

[0012]

According to the present invention, the growth substrate is fixed via a mirror-finished thin plate of the same size as the substrate holder, and the entire surface of the substrate holder is covered with the mirror-finished thin plate to increase the apparent growth-target substrate area and the substrate temperature. To prevent the decrease of

Further, by covering with a mirror-finished thin plate having the same area as that of the substrate holder, it becomes easy to grow HgCdTe thin film on the same wafer from the same material having a different area to a growth substrate or various growth substrates made of different materials. It is a thing.

Further, in order to prevent the substrate holder and the low melting point metal gallium for fixing the growth substrate from reacting at a high temperature of 500 ° C. or higher, a mirror thin plate is used as a separator.

Further, by using the mirror surface, gallium for adhering the growth substrate can be made to fit well,
The adhesion with the substrate to be grown is increased, the risk of dropping the substrate to be grown is avoided, and the temperature unevenness on the entire surface of the substrate to be grown is eliminated.

According to the method of the present invention, the HgCdTe thin film is deposited on a mirror-finished thin plate having the same surface area as that of the substrate holder, and HgCdT thin film is deposited on the rough surface of the substrate holder.
Since e is not deposited, radiative cooling is almost eliminated. Therefore, it is possible to prevent the substrate temperature from being lowered due to the deposition of the HgCdTe thin film.

Further, by using a mirror-finish thin plate having substantially the same area as the surface area of the substrate holder, any size of growth substrate can be loaded on the same mirror-finish thin plate regardless of the material, and the area can be increased. There is no need to control the substrate temperature due to the difference in

Further, by separating the substrate holder and gallium with a mirror thin plate, the reaction between the substrate holder and gallium can be prevented.

Further, by using a thin mirror surface plate, the effective surface area can be made smaller than that of a molybdenum substrate holder surface having a lot of irregularities, and the distance to the substrate to be grown becomes small, so that the surface tension is improved. However, the adhesion with the substrate to be grown is improved.

[0020]

EXAMPLE An example of a method for manufacturing an infrared detector material will be described below with reference to the drawings. In FIG. 1, on a substrate holder (usually having a diameter of 2 or 3 inches) 1 made of molybdenum, a 2 or 3 inch mirror-finished thin plate (Si wafer is used in this case) 1 of the same size as the holder through indium 9.
Fix 0.

The substrate holder 1 is generally a rough surface with large irregularities, but since the Si wafer has a mirror-like surface morphology, metallic gallium (Ga) having a melting point of about 30 ° C. 8), it was possible to stretch it very well because the wettability was good. When the growth substrate 2 for HgCdTe epitaxial growth is fixed on this, the mutual distance is very narrow, the surface tension is improved, and the degree of adhesion with gallium is excellent, and the growth substrate is in the middle of transportation or growth. The risk of falling from it could be greatly reduced.

Further, due to the improved adhesion, the heat from the substrate heater becomes almost uniform over the entire area of the growth substrate 2. When the grown HgCdTe thin film was evaluated by the double crystal method X-ray, the in-plane variation in crystallinity was improved by about one digit.

As a result of improving the nonuniformity of the substrate temperature in this way, the crystal uniformity of the grown HgCdTe was improved.

FIG. 4 shows a thermometer (pyrometer) utilizing infrared rays radiated from an object in the conventional method.
The graph shows the time-dependent change in the temperature of the growth substrate during the growth of the HgCdTe thin film. HgCd by MBE method
The growth temperature of Te is usually about 190 ° C., but the conventional method showed that the substrate temperature decreased by about 21 ° C. after growing for 1 hour.

When HgCdTe is grown according to the present invention,
As shown in FIG. 5, it was found that the radiative cooling from the peripheral portion of the growth substrate was very well suppressed only by a change of about 2 ° C. in 1 hour.

Since the temperature of the substrate to be grown is almost constant during the growth of the HgCdTe thin film, the characteristics of the growing HgCdTe thin film are hardly affected by the temperature.
Conventionally, double crystal X-ray diffraction of about 100 seconds could be improved to about 60 seconds by the method of the present invention. That is, HgCdTe
Deteriorates the crystal due to the decrease of the substrate temperature during growth (twin crystals)
The crystal uniformity was significantly improved as compared with the conventional method.

Further, since the mirror thin plate (Si wafer) having almost the same area as that of the substrate holder is used, the CdTe substrate, G having various areas different from each other can be formed on the mirror thin plate 10 of the present invention.
It becomes possible to stack the growth substrate 2 such as aAs or Si, and the stability of the substrate temperature is the same,
It is no longer necessary to compensate the substrate temperature with the power supplied to the substrate heater for each substrate having a different area as in the prior art.

Further, when Si or GaAs is used as a substrate for growing HgCdTe, it is necessary to temporarily heat-treat the substrate at a high temperature of 500 ° C. or higher in order to remove the oxide film on the surface of the Si or GaAs substrate. When a radiation cooling prevention Si wafer is used as a separator as in the present invention,
Since the Si wafer and gallium do not react even at 500 ° C. or higher, the compound of molybdenum and gallium was not formed on the surface of the substrate holder. That is, it is no longer necessary to wash the substrate holder with an etching solution that dissolves molybdenum each time a thin film is grown. Therefore, the substrate holder is not worn away, and the life of the holder can be extended.

[0029]

As described above in detail, according to the method for manufacturing an infrared detector material of the present invention, the substrate temperature is HgCdT.
During the film formation of e, the HgCdTe thin film that is extremely stable and has high quality and high uniformity can be formed. Therefore, by using the crystal produced by the method of the present invention, it is possible to realize an HgCdTe infrared detector having excellent operating characteristics, and it is possible to extend the service life of the substrate holder.

[Brief description of drawings]

FIG. 1 is a structural diagram for explaining a method of manufacturing an infrared detector material according to the present invention.

FIG. 2 is a structural diagram for explaining a conventional method for manufacturing an infrared detector material.

FIG. 3 is a view for explaining a conventional method for manufacturing an infrared detector material, and is an enlarged view of a part of FIG. 2;

FIG. 4 is a diagram for explaining a conventional method for manufacturing an infrared detector material, showing a change in substrate temperature during film formation of HgCdTe.

FIG. 5 is a diagram showing changes in substrate temperature during film formation of HgCdTe by the method of the present invention.

[Explanation of symbols]

 1 substrate holder 2 growth substrate 6 heater 8 gallium 9 indium 10 mirror thin plate

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location H01L 31/0264

Claims (1)

[Claims] 1. A method for producing an infrared detector material, comprising growing a HgCdTe thin film as an infrared detector material on a substrate to be grown set on a substrate holder by using a molecular beam epitaxy method, comprising: Cover the substrate with a mirror thin plate of the same size as the holder, and bring the substrate to be grown into close contact with the mirror surface of the thin plate.
A method for manufacturing an infrared detector material, which comprises growing CdTe.