JPH0251875B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing -group compound semiconductor single crystals such as GaAs, InP, and InAs, and particularly to a method for producing a cross-sectional temperature distribution at a solid-liquid interface. The present invention relates to a method for manufacturing a semiconductor single crystal.

[Prior art] In general, methods for manufacturing compound semiconductor single crystals include the horizontal Bridgeman method (H-B method) and the Japanese Patent Application Laid-open No. 58
-156599, the temperature gradient method (G・F
law) is already known. These methods are generally the same, although there is a difference in whether or not the melt-filling boat and the heating furnace move relative to each other. In other words, the - group elements are eutecticized in a proportion of chemical equivalents in a long boat, and the solid-liquid interface is moved longitudinally while maintaining a constant temperature gradient formed in the longitudinal direction of the boat. A single crystal is produced by gradually solidifying the crystal.

In any method, in order to obtain a high-quality single crystal, it is extremely important to control the cross-sectional temperature distribution at the solid-liquid interface in addition to controlling the temperature gradient formed in the longitudinal direction of the boat. In other words, in order to obtain a high-quality single crystal, it is necessary to realize a temperature distribution at the solid-liquid interface that allows the growth of the single crystal to start from the free surface of the upper layer of the melt and proceed toward the bottom of the boat, and to maintain that state. is required to remain stable for a long period of time.

For this reason, the following two methods have been adopted as conventional methods for obtaining the above-mentioned temperature distribution. The first method is to divide the heater for controlling the solid-liquid interface into multiple parts along the circumferential direction of the boat, and control each divided heater individually to obtain the optimal cross-sectional temperature distribution. It is something.

The second method is to provide heat dissipation holes above the furnace body along its longitudinal direction, thereby lowering the temperature of the upper layer of the melt at the solid-liquid interface and realizing crystal growth from the free surface. It is.

[Problems to be Solved by the Invention] However, the first and second conventional methods described above have the following problems.

In other words, the first method not only makes the heater structure extremely complicated because the divided heaters are controlled individually, but also makes the heater control system complicated, which not only increases equipment costs but also makes the structure complicated. As a result, the life of the furnace body was also shortened. Further, in the second method, since the opening size of the heat dissipation hole is fixed, there is a problem that the amount of heat dissipation cannot be delicately controlled during crystal growth. To solve this problem, we controlled the ambient temperature outside the heat radiation hole,
A method of adjusting the amount of heat dissipated from the heat dissipation holes may be considered, but this would require large installation costs and lead to a rise in maintenance costs.

[Object of the Invention] The present invention has focused on the above-mentioned problems and has been devised to effectively solve the problems.

The purpose of the present invention is to control the cross-sectional temperature distribution of the solid-liquid interface using a heating element installed at the bottom of the boat containing the melt, thereby optimizing the cross-sectional temperature without complicating the furnace structure. can be held at −
The present invention provides a method for manufacturing a group compound semiconductor single crystal.

[Summary of the Invention] The configuration of the present invention that achieves the above object is that a heating element for controlling cross-sectional temperature distribution is arranged in the lower part of the boat, and the melt on the bottom side of the boat at the solid-liquid interface is heated by this heating element. The gist of this study is to control the cross-sectional temperature distribution of the solid-liquid interface to grow a single crystal downward from the free surface.

[Example] Below, the method of the present invention will be explained in detail based on the accompanying drawings.

FIG. 1 is a side view showing an example of a semiconductor manufacturing apparatus for carrying out the method of the present invention, and FIG. 2 is an enlarged cross-sectional view taken along the line -- in FIG.

As shown in the figure, 1 is a boat for accommodating a melt M of - group element metal, and this boat 1 is configured as a long container that is open at the top and has a substantially rectangular cross section; Seed crystal 2 is attached to. - group elements are eutectic in a proportion of chemical equivalents and stored in the boat 1 as a melt M. This boat 1 is housed in a closed container 3 such as a transparent quartz tube with both ends closed. On the outer periphery of the airtight container 3, there is a heater wire 4 wound along the length of the boat 1 to heat the contents inside the boat 1, and a heat insulating material 5 covering the outer periphery of the heater wire 4 to keep the inside of the airtight container 3 warm. are sequentially formed to constitute the furnace body. A heat radiation hole 6 is formed in the upper part of the heat insulating material 5 along its longitudinal direction, and heat radiation from the hole cools the upper part of the melt M in the boat 1 and cools the free surface of the melt M. I'm starting to do that. By controlling the amount of heat from the heater wire 4, a temperature gradient is created in the longitudinal direction of the boat, and by moving the boat in the longitudinal direction while keeping this gradient constant, the solid-liquid interface is also moved. let me,
Gradually solidify the crystal from the seed crystal. At this time, it is of course important to control the temperature gradient in the longitudinal direction of the boat as described above, but in order to obtain a good single crystal, it is also important to control the cross-sectional temperature distribution at the solid-liquid interface.

Therefore, in order to improve the above-mentioned temperature distribution, this device example is provided with a heating element 7 for controlling cross-sectional temperature distribution (hereinafter referred to as "control heating element") at the lower part of the boat 1. Specifically, the control heating element 7 is made of, for example, a silicon carbide heater or a tantalum heater having a predetermined electrical resistance, and is installed along the longitudinal direction of the closed container 3 facing the bottom of the boat 1. It is arranged as one long piece. A power supply line (not shown) is connected to the control heating element 7, so that the amount of heat generated can be controlled by controlling the supplied current. Further, a large number of thermocouples (not shown) as temperature detection means are provided along the longitudinal direction of the closed container 3 corresponding to the boat 1, for example, on the upper and lower sides thereof, and based on the detected values, The temperature gradient and cross-sectional temperature distribution are controlled.

Next, the method of the present invention will be specifically explained based on an example of the apparatus configured as described above.

First, in boat 1, for example, In, P, etc.
The group elements are accommodated in a chemical equivalent ratio, and the - group elements are eutecticized to form a melt M by energizing the heater wire 4. Then, by appropriately controlling the amount of current applied to the heater wire 4, a solidification point of the melt M is formed in the middle, and the solid-liquid interface 8 is shown by the arrow along the longitudinal direction of the boat 1 while keeping this slope constant. By moving the boat in this manner, single crystal growth is started from the seed crystal side, and the crystal is gradually solidified in the longitudinal direction of the boat to produce a single crystal. In this case, since the heat radiation hole 6 is formed above the closed container 3, the upper side of the melt M, that is, the free surface side, tends to be cooled. As a result, the crystals gradually solidify from above to below, and the cross-sectional temperature distribution at this time is very important. Therefore, the control heating element 7 provided below the boat 1 is energized to heat it, thereby making the bottom side of the boat 1 higher in temperature to obtain an optimal cross-sectional temperature distribution. In other words, since the melt at the bottom of the boat 1 is held at a higher temperature than its upper free surface, crystal growth is ensured below the free surface, and an optimal cross-sectional temperature distribution is obtained. Fine control of the amount of heat generated is performed by controlling the current supplied to the control heating element 7. In FIG. 1, the right side of the boat 1 shows the grown single crystal 9, and the left side shows the still molten molten compound 10. The quality of the cross-sectional temperature distribution is determined, for example, based on the temperature values detected by a large number of thermocouples (not shown) installed above and below the boat 1 along its longitudinal direction, and this feedback signal is used to control the current as described above. It will be done.
Such delicate control of the amount of heat generated is mainly performed by the control heating element 7 located below the boat 1. That is, at the start of crystal growth,
As shown in Figure 3, the shape of the solid-liquid interface tends to be slightly concave, so it is necessary to correct this to a flat shape, so at the start of growth, the power of the control heating element 7 is slightly increased to generate heat. Increase the amount slightly,
The solidification of crystals in the lower part of the boat 1 is slightly delayed. This corrects the concave state of the solid-liquid interface,
A planar solid-liquid interface tilted linearly downward can be obtained.

Then, as the crystal solidification progresses in the longitudinal direction of the boat 1, the solid-liquid interface tends to be inclined linearly as shown in Figure 4, approaching the ideal state considerably, so that the crystals grow. Accordingly, the power of the control heating element 7 is gradually reduced to reduce the amount of heat generated.

In this way, since the amount of heating of the melt at the bottom of the boat is controlled by the control heating element 7 provided at the bottom of the boat 1, it is possible to realize the optimum cross-sectional temperature distribution for single crystal growth. Moreover, the optimum temperature distribution can be kept constant during the crystal growth period, and a high quality single crystal can be obtained.

In the above device example, the elongated control heating element 7 is fixedly provided at the bottom of the boat 1 to control the amount of heat generated. However, the present invention is not limited to this. It may be configured as shown in FIG. That is, a single small heating element 7 for control is provided at the bottom of the boat 1 so as to be movable along the longitudinal direction of the boat 1, and this small heating element 7 itself follows the movement of the solid-liquid interface 8. and move the boat longitudinally,
Its movement is controlled so that it is always located below the solid-liquid interface 8.

According to this device example, there is no need to provide a heater over the entire lower part of the boat 1, and a small control heating element 7 is sufficient, and the structure can be greatly simplified compared to the device example described above.

[Effects of the Invention] In summary, according to the method of the present invention, the following excellent effects can be exhibited.

(1) By controlling the amount of heat using a control heating element installed at the bottom of the boat as a heat source, it is possible to optimize the cross-sectional temperature distribution near the solid-liquid interface and maintain the state to the specified level required for single crystal growth. It can be maintained stably for only a certain amount of time.

(2) Therefore, the temperature at the bottom of the boat near the solid-liquid interface can be maintained at a higher temperature without complicating the structure of the device, making it possible not only to reliably grow crystals from the free surface but also to achieve optimal growth. Since a cross-sectional temperature distribution can be realized, a high quality semiconductor single crystal can be obtained.

[Brief explanation of drawings]

FIG. 1 is a side view showing an example of a semiconductor single crystal manufacturing apparatus for carrying out the method of the present invention, FIG. 2 is an enlarged cross-sectional view taken along the line arrow in FIG. FIG. 4 is a partial cross-sectional view showing the solid-liquid boundary state at the start of crystal growth. FIG. 5 is a partial cross-sectional view showing the solid-liquid boundary state in the latter half of crystal growth. FIG. It is a side view showing an example of a manufacturing device. In the figure, 1 is a boat, 2 is a seed crystal, 7 is a heating element for controlling cross-sectional temperature distribution, 8 is a solid-liquid interface, and M is a melt.

Claims (1)

[Claims] 1. In a boat, a melt is formed by eutecticizing the - group elements in a proportion of chemical equivalents, and the melt is moved along the solid-liquid interface while keeping the temperature gradient formed in the length direction of the boat constant, and a seed crystal is formed. In order to gradually solidify the crystal from the bottom to form a single crystal, a heating element for controlling the cross-sectional temperature distribution is placed at the bottom of the boat, and the heating element heats the melt on the bottom side of the boat at the solid-liquid interface, so that the free surface 1. A method for producing a - group compound semiconductor single crystal, characterized in that the cross-sectional temperature distribution of a solid-liquid interface is controlled in order to grow the single crystal further downward.