JPS6315741B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for vapor phase growth on a − group compound semiconductor substrate such as GaAs.

Conventionally, in the manufacture of semiconductor devices, oxidation, diffusion treatments, etc. have been performed under normal pressure or reduced pressure. However, in recent years, attempts have been made to carry out the oxidation treatment under high pressure (usually 1 atm or more, about 20 atm) for the purposes described below.

(1) Lowering the temperature of the semiconductor process The rate of oxidation under high pressure increases almost in proportion to the pressure, so if high-pressure oxidation is performed at the conventional oxidation time, an oxide film of the same thickness can be obtained at a lower temperature. It will be done. The advantages of this low-temperature process are that it is economical by extending the lifespan of equipment and fixtures such as furnaces and quartz tubes, and that contaminants that contaminate semiconductor wafers through the quartz tubes (furnace core tubes) are reduced. , the ability to prevent wafer warping that occurs under high temperatures, and the ability to prevent the generation and movement of dislocations and stacking faults within the wafer.

(2) Shortening the semiconductor process When oxidizing under high pressure, an oxide film with the same thickness can be obtained in a shorter oxidation time by oxidizing at the same temperature as under normal pressure. Furthermore, devices with a LOCOS structure require a very thick oxide film, but if high-pressure oxidation is used in such cases, desired oxidation can be achieved in a short time.

In the high-pressure oxidation method having the above-mentioned advantages, a high-pressure oxidation furnace conventionally used is shown in FIG. This high-pressure oxidation furnace is equipped with a robust high-pressure vessel 1 that can withstand high temperatures and pressures of about 1000° C. or less, and requires complicated temperature and pressure control. That is, a quartz tube 4 containing a boat 3 holding a semiconductor wafer 2 is disposed inside the high-pressure container 1, and the quartz tube 4 is used to heat the wafer 2 in a predetermined manner.
A heater 5, a heat insulating material 6, and a cooling pipe 7 are provided in a complicated manner between the high-pressure vessel 1 and the high-pressure vessel 1, respectively. Further, 8 is a pipe for introducing high-purity gas into the quartz tube 4, 9 is a gas discharge pipe, 10 is a pipe for introducing gas into the furnace, 1
1 is a gas exhaust pipe. In such a high-pressure oxidation furnace, the cooling pipe 7 is necessary because the heat generated by the heater 5 raises the furnace wall of the high-pressure vessel 1 to a high temperature, which not only complicates the structure but also places the entire system under high temperature. Therefore, it is necessary to process the wafer 2 while being housed in the quartz tube 4 in order to prevent the contamination of impurities.

In order to correct these deficiencies, the present inventors came up with a high-pressure oxidation method as described below as a reference example with reference to FIGS. 2 and 3.

That is, first, a first reference example will be described with reference to FIG. 2. The high-pressure oxidation furnace shown in FIG. It is meant to accommodate
It is configured such that a laser beam 30 can be irradiated only onto the wafer 22 from the outside through the viewing window 20. In addition, 23 is the sample stand or boat, 2
8 is a high-pressure, high-purity gas introduction pipe, and 29 is a gas discharge pipe. Although the viewing window 20 is made of a material with low optical loss to the laser beam, its installation area may be relatively small. The laser beam 30 can be obtained by a well-known Nd:YAG laser, but if the beam diameter is small, a device that scans the surface of the wafer 22 with the laser beam 30 or a device that moves the boat 23 may be used to direct the laser beam 30 onto the wafer 22. A moving mechanism for relatively scanning the surfaces of 22 may be incorporated. Further, it is reasonable to provide a feeding mechanism that sequentially feeds the wafers 22 into the high-pressure container 21 to enable continuous processing.

If the high-pressure oxidation furnace is configured as described above, only the wafer 22 can be heated by the laser beam 30, so that only the vicinity of the surface of the wafer 22 becomes high temperature. Therefore, the high-pressure vessel 21 only needs to withstand pressure, and can be designed without considering the influence of heat as in the conventional case, making the structure of the furnace very simple.
In addition, in the oxidation process, the quality of the oxide film is determined only by the purity of the atmospheric gas in the high-pressure vessel 21, and is not affected by the heater in the furnace unlike in the past, so all you need to do is make the atmospheric gas highly purified. A high purity oxide film can be formed. During this oxidation treatment, when a mixed gas of high pressure monosilane (SiH ₄ ) and O ₂ is introduced into the container 21 from the pipe 28 as an atmospheric gas, the laser beam 30
SiH ₄ +2O ₂ on the wafer 22 being heated by
→A chemical reaction of SiO ₂ + 2H ₂ O occurs, and the wafer 22
An oxide film (SiO ₂ ) grows on the surface by CVD.
This growth itself occurs at high speed because it is under high pressure.
Note that the oxide film may be formed locally or selectively by setting the irradiation area of the laser beam 30.

Next, a second reference example will be described with reference to FIG. 3. The high-pressure oxidation furnace shown in FIG. 3 is suitable for cases where a higher purity atmosphere is required. and place the wafer 22 in this quartz tube.
It accommodates. In this case, peephole 2
The laser beam 30 from 0 efficiently reaches the surface of the wafer 22 through the wall of the quartz tube 24.
Note that 38 is a high pressure (high purity) gas introduction pipe similar to 28, and 39 is a gas discharge pipe similar to 29.

The above two reference examples are based on oxidizing gas (O ₂
The present invention can also be applied to the case where the wafer 22 is directly oxidized by introducing only H ₂ O).

The present inventor has developed a high-pressure oxidation method as described above.
As a result of considering applying the present invention to a method of performing vapor phase growth on a group compound semiconductor substrate and adding various considerations, the present invention was arrived at, which allows the above-mentioned vapor phase growth to be performed satisfactorily. The present invention thus obtained provides a method for vapor phase growth of - group compound semiconductors such as GaAs, etc.
A gas containing the same group element as the group element such as As constituting the -group compound semiconductor substrate and a source gas for vapor phase growth are introduced into a container that accommodates the group compound semiconductor substrate, and The energy beam is irradiated onto the - group compound semiconductor substrate housed in the chamber.

Next, an embodiment of the present invention will be described with reference to FIGS. 2 and 3. In the above-mentioned first and second reference examples, a GaAs semiconductor substrate is used as the wafer 22,
Furthermore, a mixed gas of monosilane (SiH ₄ ) and ammonia is used as the high-pressure gas. Therefore, in this case, a nitride film can be grown on the wafer 22 by CVD according to 3SiH ₄ +4NH ₃ →Si ₃ N ₄ +12H ₂ . In this way, wafer 2
2. Despite the use of a GaAs semiconductor substrate in which As easily dissociates, good vapor phase growth can be performed without dissociating As.

Note that in the above embodiments, it is also possible to form a nitride film by introducing only a nitriding gas, for example, NH ₃ gas.

Since the present invention has the above-described configuration, it is possible to successfully perform vapor phase growth of a - group compound semiconductor substrate by irradiation with an energy beam without causing dissociation of group elements.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional high pressure oxidation furnace. FIG. 2 is a cross-sectional view of a high-pressure oxidation furnace used in reference examples and examples of the present invention, and FIG. 3 is a cross-sectional view of another high-pressure oxidation furnace same as the above. In addition, in the symbols used in the drawings, 20... peephole, 21... high pressure container, 22... semiconductor wafer, 24... quartz tube, 30... laser beam,
40...High frequency oscillation coil.

Claims (1)

[Claims] 1. In a method for vapor phase growth on a -group compound semiconductor substrate, a group V element that is the same as the group element constituting the -group compound semiconductor substrate is placed in a container that accommodates the -group compound semiconductor substrate. A vapor phase growth method, characterized in that a gas containing the above and a source gas for vapor phase growth are introduced, and an energy beam is irradiated onto the - group compound semiconductor substrate housed in the container.