JPH0699211B2 - Single crystal growth method and apparatus - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method and an apparatus for growing a single crystal of a compound semiconductor, and more particularly to a method and an apparatus for reliably growing a single crystal by controlling a heat flow in a horizontal boat growth method. It is a thing.

[Prior art and its problems]

When a single crystal of a compound semiconductor is grown by the temperature gradient solidification method, it is possible to control the heat flow in the melt, particularly the heat flow at the solid-liquid interface, only by gradually lowering the temperature in the electric furnace from the seed part to the melt part. It is difficult and often becomes polycrystalline during the growth. This also applies to the horizontal Bridgman method.

Therefore, various improvements have been made in order to control the heat flow in the melt and produce a single crystal with a low dislocation density. For example, in the method disclosed in Japanese Patent Laid-Open No. 55-62882, the growth interface is freely controlled by installing a cooling gas blowing device on the upper part of the boat so that a low dislocation density single crystal is grown at a high growth rate. It was done.

However, it is difficult to precisely control the heat flow in the melt only by providing the cooling gas blowing device in the upper part of the electric furnace. In particular, in the case of indium phosphide having a stacking fault energy of 18 erg / cm ² and about one third of that of gallium arsenide, which is extremely susceptible to twinning, subtle thermal fluctuation causes polycrystallization. There is a problem.

Therefore, more precise heat flow control is required to manufacture single crystals of indium phosphide and other compound semiconductors that are difficult to single crystallize.

[Means for solving problems and their effects]

When the indium phosphide single crystal was grown by the temperature gradient solidification method, the temperature distribution on the inner wall of the electric furnace and on the boat was actually measured, and as shown in FIG. The temperature A of the liquid is often higher than the temperature B of the inner wall of the electric furnace. In such a temperature state, a heat flow that escapes from the indium phosphide melt through the boat wall to the outside of the boat exists, and crystal nuclei are likely to be generated on the inner wall surface of the boat. Therefore, polycrystallization is likely to occur, and it is extremely difficult to form a single crystal.

Therefore, the present invention lowers the temperature inside the boat from the surroundings, suppresses the generation of nuclei on the inner wall surface of the boat by generating a heat flow from the outside of the boat toward the inside of the boat, and makes it possible to reliably grow a single crystal. It is the one.

That is, the present invention is to place a volatile element in a low temperature part in a quartz ampoule heated by an electric furnace, and put a boat containing a metal element in a high temperature part, and use the temperature gradient solidification method or the horizontal Bridgman method in the boat. After creating a melt of the compound semiconductor in the method for growing a single crystal, a heat sink is thermally coupled to the seed end side of the boat, and a cooling pipe communicating with the outside of the furnace is provided around the heat sink.
While absorbing the heat in the boat to the heat sink through the seed, to provide heat by providing an auxiliary heater around the boat, thereby keeping the temperature inside the boat lower than the temperature outside the boat, It is characterized in that a single crystal is grown so that heat is constantly supplied from around the boat into the melt in the boat.

Further, the apparatus of the present invention used to carry out this method is a quartz ampoule in which a volatile element is placed on one end side and a boat containing a metal element is placed on the other end side, the one end side is a low temperature part, In a single crystal growing apparatus horizontally installed in an electric furnace having the other end side as a high temperature part, a heat sink installed so as to contact the seed end side of the boat and the sheet sink outside the quartz ampoule. A cooling pipe whose end is installed so as to surround the furnace, an auxiliary heater which is installed outside the quartz ampoule so as to surround the boat and which is divided at least vertically, and the cooling pipe and the auxiliary heater. It is characterized by having a heat insulating plate installed between.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.
1 to 4 show an example of an apparatus used in the method for growing a single crystal according to the present invention. In the figure, 11 is a quartz ampoule whose inside is evacuated, 12 is a volatile element such as phosphorus installed on one end side, and 13 is a boat installed on the other end side. A metal element such as indium is contained in the boat 13, and a seed 14 is installed on one end side thereof. Reference numeral 15 is a low temperature side electric furnace for controlling the vapor pressure of phosphorus in the quartz ampoule 11, and 16 is a high temperature side electric furnace for heating the boat 13 side with a predetermined temperature profile.

According to the method of the present invention, after vaporizing phosphorus 12 and diffusing it into indium to form a melt of indium phosphide in the boat 13, the temperature profile in the high temperature side electric furnace 15 is gradually changed. Alternatively, the single crystal is grown in the boat 13 from the seed 14 side by gradually moving the electric furnace or the ampule while keeping the temperature profile in the furnace as it is.

The present invention further employs the following configuration in order to generate a heat flow from the outside to the inside of the boat 13 in such a method.

First, in the quartz ampoule 11, a heat sink 21 having good thermal conductivity is placed in contact with the tip of the seed shelf of the boat 13. A cooling pipe 22 for cooling the heat sink 21 is installed around the heat sink 21 outside the quartz ampoule 11. The cooling pipe 22 has its end portion led out of the electric furnace 16 so that an inert gas for cooling flows therein. The amount of heat released from the heat sink 21 is controlled by adjusting the flow rate of this inert gas. The cooling pipe 22 is installed at a predetermined position in the electric furnace 16, and the quartz ampoule 11 is installed through the ring part thereof.

A flange-shaped heat insulating plate 23 is provided near the boat 13 of the cooling pipe 22.
Is installed so that thermal disturbance due to the cooling pipe 22 is not applied to the vicinity of the boat 13.

Further, a large number of auxiliary heaters 24 divided in the axial direction and the circumferential direction are installed outside the quartz ampoule 11 and at positions corresponding to the periphery of the boat 13. Each of the auxiliary heaters 24 is, for example, a semi-cylindrical quartz material 25 having a high temperature heater wire 26 such as Kanthal wire or Pyromax wire fixed thereto in an appropriate pattern as shown in FIG. The amount of heat generated can be controlled. The reason why the auxiliary heater 24 is divided into a plurality of parts in the axial direction is to facilitate uniform heat distribution in the vicinity of the boat 13 which is difficult to achieve only with the electric furnace 16 and to finely adjust the temperature distribution in the axial direction.
Further, the reason why the auxiliary heater 24 is divided into the upper and lower parts is to adjust the upper and lower heat generation amounts to eliminate the temperature difference in the vertical direction in the electric furnace 16. The auxiliary heater may be divided into, for example, four parts in the circumferential direction, and the temperature may be adjusted from above, below, left and right.

After forming the indium phosphide melt 27 in the boat 13, in order to grow a single crystal, first, the electric furnace 16 and the auxiliary heater are used.
A soaking state is formed over almost the entire length of the boat 13 by using the 24 and the heat sink 21, and thereafter, crystal growth is started by, for example, a temperature gradient solidification method. Although the temperature profile is given by the electric furnace 16 as in the conventional case, heat absorption by the heat sink 21 and the cooling pipe 22 and auxiliary heating by the auxiliary heater 24 are further performed while maintaining the temperature profile. As a result, the heat flow inside and outside the boat 13 is as shown by the arrow in FIG. That is, the heat supplied from the auxiliary heater 24 enters the boat 13 from the outside of the boat 13, flows through the indium phosphide melt 27 and the seed 14, and then flows to the heat sink 21. Therefore, in this state, the temperature in the melt 27 is lower than that of the wall of the boat 13, nucleation from the inner wall surface of the boat 13 is suppressed, and the single crystal from the seed 14 grows reliably.

FIG. 7 shows the temperature distribution during this crystal growth process. That is, in the entire process of the temperature gradient solidification method, the temperature A of the indium phosphide melt in the boat 13 is the temperature B of the inner wall of the electric furnace 16.
Is lower than. Giving such a temperature distribution is extremely effective for growing a single crystal.

By the way, in a normal horizontal electric furnace, 20 to 30 ℃ vertically
There is a temperature difference of (upper part is higher). The presence of such a temperature difference adversely affects the growth of directional solidification. Such a temperature difference can be removed by installing the auxiliary heater divided into upper and lower parts in the electric furnace as in the above-mentioned embodiment and adjusting the electric power supplied to each auxiliary heater.
In addition, the auxiliary heaters may be installed one above and one below as long as they do not affect the soaking length of the temperature distribution in the axial direction in the electric furnace. If the soaking length is affected, the auxiliary heater may be divided into a plurality of parts in the axial direction as well, and the calorific value of each may be adjusted to obtain the required soaking length.

Further, in the above embodiment, the number of turns of the cooling pipe around the heat sink is set to one. However, if it is desired to further enhance the heat absorption effect, the number of turns may be set to two or more. However, in that case, it is necessary to increase the thickness of the heat insulating plate in order to prevent thermal disturbance to the crystal growth portion as much as possible.

In the case of growing crystals by the temperature gradient solidification method, if the temperature gradient in the growth process cannot be made large in consideration of the temperature distribution of the low temperature part of the quartz ampoule (zone where volatile elements are placed), the boat should be set as described above. May be installed in the opposite direction, ie with the seed shelf on the opposite side of the volatile element. In that case, naturally, the heat sink and the cooling tube are installed on the end side of the quartz ampoule.

In addition, in the said Example, although the case where this invention was applied to the temperature gradient solidification method was demonstrated, this invention is similarly applicable also to a horizontal Bridgman method.

Further, in the above embodiment, the growth of the indium phosphide single crystal has been described, but the present invention can be applied to the growth of other compound semiconductor single crystals.

〔The invention's effect〕

As described above, according to the present invention, when growing a single crystal by the temperature gradient solidification method or the horizontal Bridgman method,
By combining the heat sink, cooling tube and auxiliary heater, the heat entering the boat from around the outside of the boat passes through the melt of the compound semiconductor and creates the heat flow that flows through the seed to the heat sink, and the temperature of the melt changes to the wall of the boat. Since the temperature is lower than the temperature of 1, the generation of crystal nuclei on the inner wall surface of the boat is suppressed, and the single crystal can be reliably grown.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of an apparatus used for the method for growing a single crystal of the present invention, and FIGS.
II-II line of the figure, III-III line, sectional view in the IV-IV line,
FIG. 5 is a perspective view of an auxiliary heater used in the apparatus, FIG. 6 is an explanatory view showing the heat flow inside and outside the boat in the method of the present invention, and FIG. 7 is a temperature gradient solidification method by the method of the present invention. FIG. 8 is a graph showing the temperature distribution when the above is performed, and FIG. 8 is a graph showing the temperature distribution in the conventional temperature gradient solidification method. 11-quartz ampoule, 12-phosphorus, 13-boat, 14-seed,
15 ~ low temperature side electric furnace, 16 ~ high temperature side electric furnace, 21 ~ heat sink, 22 ~ cooling pipe, 23 ~ heat insulating plate, 24 ~ auxiliary heater, 27 ~ indium phosphide melt.

Claims (2)

[Claims] 1. A volatile element is placed in a low temperature part of a quartz ampoule heated by an electric furnace, and a boat containing a metal element is placed in a high temperature part of the quartz ampoule, and a temperature gradient solidification method or a horizontal Bridgman method is used in the boat. In a method for growing a single crystal after forming a melt of a compound semiconductor in, a heat sink is thermally coupled to the seed end side of the boat, and a cooling pipe communicating with the outside of the furnace is provided around the heat sink. The heat inside the boat is absorbed by the heat sink through the seeds, and the heat is supplied by providing an auxiliary heater around the boat to keep the temperature inside the boat lower than the temperature outside the boat. A single-crystal growing method, wherein a single crystal is grown such that is constantly supplied from around the boat into the melt in the boat. 2. A quartz ampoule having a volatile element on one end and a boat containing a metal element on the other end is placed in an electric furnace having the low temperature part on the one end side and the high temperature part on the other end side. In a single crystal growth apparatus installed horizontally, a heat sink installed on the seed end side of the boat, and a cooling pipe having an end installed outside the quartz ampoule so as to surround the heat sink to the outside of the furnace. An auxiliary heater which is installed outside the quartz ampoule so as to surround the boat and which is divided into at least upper and lower parts; and a heat insulating plate which is installed between the cooling pipe and the auxiliary heater. Single crystal growth device.