JPS62187193A - Method and device for growing single crystal - Google Patents

Abstract

PURPOSE:To surely grow a single crystal by rendering the temp. of a melt lower than that of a boat wall by a combination of a heat sink and a cooling pipe, and controlling the generation of a crystal body on the inner wall of the boat. CONSTITUTION:For example, the melt 27 of indium phosphide is prepared in the boat 13 to grow a single crystal. A soaking state is formed over the whole length of the boat 13 by using an electric furnace 16, an auxiliary heater 24, and the heat sink 21. Then the growth of a single crystal is started, for example, by a temp. gradient solidification method. Although a temp. profile is given by the electric furnace 16 as before, heat absorption by the heat sink 21 and the cooling pipe 20 and auxiliary heating by the auxiliary heater 24 are simultaneously carried out. Consequently, heat flows as shown by the arrow on the inside and outside of the boat 13, and the heat from the auxiliary heater 14 enters the inside of the boat from the outer periphery of the boat 13 and flows toward the heat sink 21 through the melt 27 and a seed 14. Accordingly, the temp. of the melt 27 is made lower than that of the wall of the boat 13, the generation of nuclei from the inner wall surface of the boat 13 is controlled, and the single crystal from the seed 14 is surely grown.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a method and apparatus for growing single crystals of compound semiconductors, and more particularly to a method and apparatus for reliably growing single crystals by controlling heat production in a horizontal boat growth method. It is something.

[Prior art and its problems]

When growing single crystals of compound semiconductors using the temperature gradient solidification method, it is difficult to control the heat flow in the melt, especially at the solid-liquid interface, by simply lowering the temperature in the electric furnace gradually from the seed section to the melt section. It is difficult and often becomes polycrystalline during growth. This also applies to the horizontal Bridgman method.

Therefore, various improvements have been made to control the heat flow in the melt and to produce single crystals with low dislocation density. For example, the method disclosed in Japanese Patent Application Laid-Open No. 55-62882 installs a cooling gas blowing device on top of the boat to freely control the growth interface and grow a low dislocation density single crystal at a high growth rate. This is how it was done.

However, it is difficult to precisely control the flow of heat within the melt simply by providing a cooling gas blowing device in the upper part of the electric furnace. In particular, in materials such as indium phosphide, which has a stacking fault energy of 18 erg/cm'', which is about one-third that of gallium arsenide, and which is extremely prone to twinning, polycrystallization occurs due to subtle thermal fluctuations. There is a problem.

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

[Means for solving problems and their effects]

When indium phosphide single crystals are grown using the temperature gradient solidification method, when we actually measure the temperature distribution on the inner wall of the electric furnace and inside the boat, we find that the indium phosphide molten inside the boat is 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, there is a heat flow that escapes from the indium phosphide melt to the outside of the boat through the boat wall, and crystal nuclei are likely to be generated on the inner wall surface of the boat. For this reason, polycrystalization tends to occur, making it extremely difficult to produce a single crystal.

Therefore, the present invention lowers the temperature inside the boat compared to the surroundings, generates a heat flow from the outside of the boat toward the inside of the boat, suppresses the generation of nuclei on the inner wall of the boat, and makes it possible to reliably grow single crystals. This is what I did.

That is, in the present invention, a volatile element is placed in a low-temperature part of a quartz ampoule heated by an electric furnace, a boat containing a metal element is placed in a high-temperature part, and the temperature gradient solidification method or horizontal Bridgman method is used to cool the volatile element in the boat. In the method of growing a single crystal after creating a compound semiconductor melt, a heat sink is thermally coupled to the seed end side of the boat, and a cooling pipe leading to the outside of the furnace is provided around the heat sink,
Absorbing the heat inside the boat through the seeds toward the heat sink, and providing heat by providing an auxiliary heater around the boat, thereby keeping the temperature inside the boat lower than the temperature outside the boat, This method is characterized by growing a single crystal by constantly supplying heat from around the boat into the melt inside the boat.

The apparatus of the present invention used to carry out this method includes a quartz ampoule in which a volatile element is placed on one end and a boat containing a metal element is placed on the other end. In a single crystal growth apparatus installed horizontally in an electric furnace with the other end as a high temperature section, the heat sink is installed so as to be in contact with the seed end side of the boat, and the heat sink is installed outside the quartz ampoule. a cooling pipe whose end communicates outside the furnace; an auxiliary heater which is divided into at least an upper and a lower part and which is installed outside the quartz ampoule so as to surround the boat; and a combination of the cooling pipe and the auxiliary heater. It is characterized by comprising a heat insulating plate installed between the two.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

1 to 4 show an example of the apparatus used in the single crystal growth method of the present invention, in which 1) is a quartz ampoule whose interior is evacuated; 12 is a volatile element placed on one end of the ampoule; Rin, 13 is a boat installed on the other end side. A metal element such as indium is housed in the boat 13, and a seed 14 is installed at one end of the boat 13. 15 is a low-temperature side electric furnace that controls the vapor pressure of phosphorus in the quartz ampule 1), and 16 is a high-temperature side electric furnace that heats the boat 13 side with a predetermined temperature profile.

The method of the present invention involves creating a melt of indium phosphide in a boat 13 by evaporating phosphorus 12 and diffusing it into indium, and then gradually changing the temperature profile in the high-temperature electric furnace 15. Alternatively, the method is the same as the conventional method in that the single crystal is grown in the boat 13 from the seed 14 side by gradually moving the electric furnace or the ampoule while leaving the temperature profile in the furnace as it is.

In this method, the present invention further employs the following configuration in order to create a heat flow from the outside to the inside of the boat 13.

First, a heat sink 21 with good thermal conductivity is installed in the quartz ampoule 11 in contact with the tip of the seed shelf of the boat 13. Also, the heat sink 2 on the outside of the quartz ampoule 1)
A cooling pipe 22 for cooling the heat sink 21 is installed around the heat sink 21 . The end of the cooling pipe 22 is led out of the electric furnace 16, and an inert gas for cooling is allowed to flow therein. By adjusting the flow rate of this inert gas, the amount of heat released from the heat sink 21 is controlled. In addition, cooling pipe 2
2 is installed at a predetermined position within the electric furnace 16, and the quartz ampoule 1) is inserted through the ring portion thereof.

Further, a flange-shaped heat insulating plate 23 is installed near the boat 13 of the cooling pipe 22 to prevent thermal disturbances caused by the cooling pipe 22 from being 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 1) at positions corresponding to the periphery of the boat 13. Each auxiliary heater 24 is, for example, a semi-cylindrical quartz material 25 with high-temperature heater wires 26 such as Kanthal wire or Pyromax wire fixed in an appropriate pattern, as shown in FIG. The amount of heat generated can be controlled by The reason why the auxiliary heater 24 is divided into a plurality of parts in the axial direction is to make it easier to uniformly heat the vicinity of the boat 13, which is difficult to achieve with the electric furnace 16 alone, and to finely adjust the temperature distribution in the axial direction. The reason why the auxiliary heater 24 is divided into upper and lower halves is to adjust the amount of heat generated in the upper and lower halves to eliminate temperature differences in the vertical direction within the electric furnace 16. Note that the auxiliary heater may be divided into four parts in the circumferential direction, and the temperature may be adjusted from the top, bottom, left, and right.

Now, after creating the indium phosphide melt 27 in the boat 13, in order to grow a single crystal, first create a uniform heating condition over almost the entire length of the boat 13 using the electric furnace 16, the auxiliary heater 24, and the heat sink 21. Then, crystal growth is started, for example, by a temperature gradient solidification method. The temperature profile is provided by the electric furnace 16 as in the conventional case, but while the temperature profile is maintained, heat absorption by the heat sink 21 and cooling pipe 22 and auxiliary heating by the auxiliary heater 24 are performed. As a result, the heat flows inside and outside the boat 13 as shown by the arrows in FIG. In other words, the heat supplied from the auxiliary heater 24 enters the boat 13 from around the outside of the boat 13, passes through the indium phosphide melt 27 and the seeds 14, and flows to the heat sink 21. Therefore, in this state, the temperature in the melt 27 is lower than that in the wall of the boat 13, suppressing the generation of nuclei from the inner wall surface of the boat 13, and ensuring that the single crystal from the seed 14 grows.

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 lower than the temperature B of the inner wall of the electric furnace 16. Providing such a temperature distribution is extremely effective for growing single crystals.

By the way, in a normal horizontal electric furnace, there are 20 to 3
There is a temperature difference of 0°C (higher at the top). The existence of such a temperature difference has a negative effect on the growth of unidirectional solidification.Such a temperature difference can be solved by installing an auxiliary heater divided into upper and lower parts in the electric furnace as in the above embodiment. This can be removed by adjusting the power supplied to the In addition, if the auxiliary heater does not affect the soaking length of the temperature distribution in the axial direction in the electric furnace, it is sufficient to install one at the top and one at the top. By dividing it into a plurality of parts in the direction and adjusting the amount of heat generated in each part, the required soaking length can be obtained.

Further, in the above embodiment, the number of turns of the cooling pipe around the heat sink is 1 second, but if it is desired to further enhance the heat absorption effect, the number of turns of the cooling pipe around the heat sink may be 2 or more. However, in that case, it is necessary to increase the thickness of the heat insulating plate in order to minimize thermal disturbance to the crystal growth area.

In addition, when growing crystals using the temperature gradient solidification method, if a large temperature gradient cannot be maintained during the growth process due to the temperature distribution of the low-temperature part of the quartz ampoule (the zone where volatile elements are placed), use the boat as described above. may be installed in the opposite direction, with the seed shelf located on the opposite side of the volatile element. In that case, the heat sink and cooling pipe will naturally be installed on the end side of the quartz ampoule.

In the above embodiments, the present invention was mainly applied to the temperature gradient solidification method, but the present invention is equally applicable to the horizontal Bridgman method.

Furthermore, in the above embodiments, the growth of indium phosphide single crystals has been described, but the present invention is also applicable to the growth of other compound semiconductor single crystals.

〔Effect of the invention〕

As explained above, according to the present invention, when growing a single crystal by the temperature gradient solidification method or the horizontal Bridgman method,
The combination of the heat sink, cooling tube, and auxiliary heater creates a heat flow in which heat enters the boat from the orbit outside the boat, passes through the compound semiconductor melt, passes through the seeds, and flows to the heat sink, causing the temperature of the melt to drop to the boat wall. Since the temperature is set to be lower than , generation of crystal nuclei on the inner wall surface of the boat is suppressed, and single crystals can be grown reliably.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the apparatus used in the single crystal growth method of the present invention, and FIGS.
5 is a perspective view of the auxiliary heater used in the device;
The figure is an explanatory diagram showing the flow of heat inside and outside the boat in the method of the present invention, Figure 7 is a graph showing the temperature distribution when the temperature gradient solidification method is implemented by the method of the present invention, and Figure 8 is a graph showing the conventional temperature gradient solidification method. It is a graph showing temperature distribution in a solidification method. 1) ~quartz ampoule, 12~phosphorus, 13~boat, 14~
Seed, 15 - low temperature side electric furnace, 16 - high temperature side electric furnace, 2
1-heat sink, 22-cooling pipe, 23-insulation board, 24
Figure 1 Z7 indium phosphide melt Figure 6

Claims (2)

[Claims] (1) A volatile element is placed in the low temperature part of a quartz ampoule heated by an electric furnace, a boat containing a metal element is placed in the high temperature part, and the compound is placed in the boat using the temperature gradient solidification method or the horizontal Bridgman method. In the method of growing a single crystal after creating a semiconductor melt, a heat sink is thermally coupled to the seed end side of the boat, and a cooling pipe leading to the outside of the furnace is provided around the heat sink, and the inside of the boat is heated. heat is absorbed through the seeds toward the heat sink, and auxiliary heaters are provided around the boat to provide heat, thereby keeping the temperature inside the boat lower than the temperature outside the boat, so that the heat is constantly absorbed. A single crystal growth method characterized by growing a single crystal by supplying it from around a boat into a melt inside the boat. (2) A quartz ampoule containing a volatile element on one end and a boat containing a metal element on the other end is placed horizontally in an electric furnace with one end as a low-temperature section and the other end as a high-temperature section. In the single crystal growth apparatus installed, a heat sink installed on the seed end side of the boat, a cooling pipe installed outside the quartz ampoule so as to surround the heat sink, the end of which communicates with the outside of the furnace; An auxiliary heater installed outside the quartz ampoule so as to surround the boat and divided into at least an upper and lower part, and a heat insulating plate installed between the cooling pipe and the auxiliary heater. Crystal growth equipment.