JPH06283447A - Vapor phase growth of compound semiconductor film - Google Patents

Abstract

PURPOSE:To prepare a device having a good crystalline property such as a surface condition and X-ray half-value width and an excellent characteristic. CONSTITUTION:A low temperature buffer layer is made to grow on a semiconductor substrate at a temperature of low temperature growth, a buffer layer is made to grow at a temperature of a prescribed a growth temperature higher than the low growth temperature, thermocycle anneling performing a temperature rise to a higher temperature than the growth temperature and a temperature fall to a lower temperature than the low temperature growth temperature is performed so as to make a middle layer to grow at a prescribed temperature exceeding the low growth temperature and under the high growth temperature. Further, thermocycle annealing is performed followed by growing an active layer at a higher temperature than the low growth temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to Si semiconductors having GaA
The present invention relates to a method of vapor-depositing a thin film of a compound semiconductor crystal such as s that does not lattice match.

[0002]

2. Description of the Related Art Conventionally, research has been conducted on forming a GaAs device such as an optical device at a low cost by forming a compound semiconductor thin film such as GaAs on a relatively inexpensive Si wafer. This GaAs device
It can be integrated with Si devices, and is particularly promising for high-efficiency solar cells.

Since the Si substrate and the compound semiconductor thin film such as GaAs have greatly different lattice constants and thermal expansion coefficients,
The dislocation density (EPD) of the grown thin film is high (10 ⁷ -1
0 ⁸ cm ^-2 ), or the crystallinity is not sufficient due to poor surface condition. Therefore, as a growth method for improving the characteristics of the thin film, a two-step growth method or a thermal cycle annealing method is used.

FIG. 3 shows a substrate temperature process for growing GaAs on a Si substrate by combining the two-step growth method and the thermal cycle annealing method. First, the Si substrate is heated to 900 ° C. or higher in hydrogen to remove the oxide film on the surface of the Si substrate (a). Next, the substrate temperature is set to 300 to 500 ° C.
And the GaAs low temperature buffer layer is grown to 5 to 50 nm (b).

Further, the substrate temperature is raised to 550 to 800 ° C. and the GaAs buffer layer is grown to 1 μm (c).
After raising the substrate temperature to 850 to 900 ° C., the step of lowering it to 300 ° C. or lower is repeated several times (1 to 10 times), so-called thermal cycle annealing is performed (d). Finally, as in the process c, the substrate temperature is set to 550 to 800 ° C., and the GaAs layer serving as the active region of the device is grown by several μm.

[0006]

However, in the conventional growth method, the crystallinity such as X-ray half width is not sufficient,
In particular, since the surface state of the thin film is rough, there is a problem that a fine device cannot be produced.

Therefore, the present invention has been made in order to solve such a conventional problem, and an object of the present invention is to obtain excellent crystallinity such as surface condition and X-ray full width at half maximum. It is an object of the present invention to provide a vapor phase growth method of a compound semiconductor thin film capable of producing a device having characteristics.

[0008]

In order to achieve the above object, the present invention provides a method of vapor-depositing a compound semiconductor thin film which is not lattice-matched with a semiconductor substrate on a semiconductor substrate by vapor deposition at a predetermined low temperature. A low temperature buffer layer is grown at a growth temperature, a buffer layer is grown at a predetermined high temperature growth temperature that is higher than the low temperature growth temperature, a temperature rise to a temperature higher than the high temperature growth temperature and a temperature lower than the low temperature growth temperature. Thermal cycle annealing is performed to lower the temperature, the intermediate layer is grown at the low temperature growth temperature or higher or the high temperature growth temperature or lower, and the thermal cycle annealing is performed again, and then the active layer is grown at a temperature higher than the low temperature growth temperature. The main point is to do.

[0009]

According to the above means, according to the present invention, the intermediate layer is grown at the low temperature growth temperature or higher temperature or the high temperature growth temperature or lower during the thermal cycle annealing immediately before growing the active layer. Annealing makes it possible to prevent defects such as surface roughness from propagating to the active layer and obtain an active layer having excellent characteristics.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows that the growth method of the present invention is used to produce Si.
A process for epitaxially growing GaAs on a substrate is shown. The raw material gas used in this example is TEG (triethylgallium) and AsH ₃ , the carrier gas is H ₂ , and the pressure is 75 Torr.

First, the Si substrate was exposed to hydrogen in hydrogen for 10 minutes at 95.
The oxide film on the surface of the Si substrate is removed by heating at 0 ° C. (it may be 900 ° C. or higher) and performing high temperature annealing (a). Next, the substrate temperature is set to 400 ° C (300 to 500 ° C may be used).
Down to 10 nm (5-5
It may be grown to 0 nm) (b). Furthermore, 700 ° C
Raise the substrate temperature to (550 to 800 ° C)
An aAs buffer layer is grown to 1.5 μm (1 μm to 3 μm may be used) (c).

After raising the substrate temperature to 850 ° C., 300
One cycle of thermal cycle annealing at 80 ° C. and 850 ° C. is repeated (d). In this thermal cycle annealing, 300 ° C
The following may be repeated at 850 ° C. or higher. After that, the substrate temperature is set to a low temperature of 500 ° C. and the intermediate layer is grown to 0.5 μm (e). The substrate temperature at this time may be at least the low temperature buffer layer growth temperature and at most the active layer or buffer layer growth temperature, and the film thickness may be 0.2 to 1 μm.

As in process d, again at 300 ° C. and 85
One cycle of 0 ° C. thermal cycle annealing is repeated (f). Finally, the substrate temperature is adjusted to 700 ° C. (may be 550 to 800 ° C.), and an active layer of 2.5 μm (may be several μm) is grown (g).

FIG. 2 shows an evaluation result by a conventional method in which an intermediate layer is not grown (comparative example), an evaluation result by the above-described example (Example 1), the substrate temperature during the growth of the intermediate layer, the active layer and the buffer layer. The evaluation result (Example 2) when the temperature is the same as that at the time of growing (700 ° C.) and the same as the above-described Example except for the above is shown.

As can be seen from this table, the surface roughness is the best in the example, and even when the intermediate layer is grown at 700 ° C., a good result is obtained as compared with the conventional case. Regarding the X-ray full width at half maximum, the case where the intermediate layer was grown at 700 ° C. was the best, and in the example as well, good results were obtained as compared with the conventional case. From this, the effect can be expected even if the substrate temperature during the growth of the intermediate layer is equal to or higher than the low temperature buffer layer growth temperature and equal to or lower than the active layer or buffer layer growth temperature.

[0016]

As described above, according to the vapor phase growth method for a compound semiconductor thin film of the present invention, a predetermined temperature above the low temperature growth temperature and below the high temperature growth temperature is set during the thermal cycle annealing before growing the active layer. Since the intermediate layer is grown at a temperature, the crystallinity such as surface condition and X-ray half width is good,
A device with excellent characteristics can be created.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a substrate temperature process in the present invention.

FIG. 2 is a table comparing the evaluation results of the conventional method and the evaluation results of the examples.

FIG. 3 is a diagram showing an example of a substrate temperature process in a conventional method.

Claims (1)

[Claims] 1. A method of vapor-depositing a compound semiconductor thin film which is not lattice-matched to a semiconductor substrate on a semiconductor substrate, wherein a low-temperature buffer layer is grown on the semiconductor substrate at a predetermined low-temperature growth temperature, and the low-temperature growth temperature is higher than the low-temperature growth temperature. A buffer layer is grown at a predetermined high-temperature growth temperature of high temperature, and thermal cycle annealing is performed to raise the temperature to a temperature higher than the high-temperature growth temperature and to lower the temperature to a temperature lower than the low-temperature growth temperature, And growing the intermediate layer at a predetermined temperature not higher than the high temperature growth temperature, further performing the thermal cycle annealing, and then growing the active layer at a temperature higher than the low temperature growth temperature. How to grow.