JPH0483794A - Compound semiconductor single crystal growth method and equipment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method and apparatus for pulling a long 1-2 group compound semiconductor single crystal of high purity or uniform composition.

[Conventional technology]

■-■ Group compound semiconductor single crystals are produced using the horizontal Bridgman method (
HB method) or liquid capsule pulling method (LEC method). Since the present invention relates to an improvement of the LEC method, this will be explained. This is done by putting the raw material and liquid sealant in a crucible and heating it with a heater to form a melt, then introducing an inert gas into a vacuum container and applying high pressure to suppress the volatilization of Group V and converting the raw material melt into a melt. Soaking a seed crystal is a method of growing a single crystal by planting the seed and pulling it up while rotating. The lifting device includes a vacuum container, an upper shaft and a lower shaft that can be rotated up and down, a vacuum evacuation device, an inert gas introduction system heater, and the like. A susceptor and a crucible are supported on the lower shaft. The lower shaft is rotating. A seed crystal is attached to the lower end of the upper shaft, but the upper shaft also rotates. This is to make temperature conditions uniform in the rotational direction. The purpose of covering the raw material melt with a liquid sealant and applying high pressure of inert gas is to suppress the decomposition of group (I) elements, which have a high vapor pressure near their melting point. When using such a device, the length of the single crystal pulled is limited by the amount of raw material initially charged in the crucible. As the raw material melt in the crucible decreases as it is pulled, it is no longer possible to pull a single crystal when the melt level decreases and the amount of melt decreases. For this reason, it is not possible to pull a sufficiently long single crystal. Once a short single crystal is pulled up, the operation must be terminated, it must be collected, and the same preparations must be made to grow it a second time. Since this increases the growth cost, there is a strong desire to pull longer single crystals. In order to pull longer single crystals, the only option is to replenish the crucible with raw materials. In the case of silicon single crystal pulling methods, many methods have been proposed that allow continuous supply of raw materials. British patent 755.422 (195G, 8.2
2) Japanese Patent Publication No. 59-79000 (19B4.
5.8) U.S. Patent 4,859,421 (19
87,4,21) U.S. Patent 2,977.258
(19G1.3.28) US Patent 4. Ei5
0,540 (1987, 3, 17) All of these methods use a wide crucible to pull a single crystal from one region of the crucible, and replenish other regions by dissolving fixed raw materials. When the amount of solid raw material supplied and the amount of solid raw material withdrawn are made approximately equal, the same amount of raw material melt always exists in the crucible. In this way, the silicon single crystal can be pulled until the replenishment solid is exhausted or until the geometric upper axis pulling limit in the apparatus is reached. Since a sufficiently long silicon single crystal ingot can be grown, the cost of manufacturing the single crystal can be reduced. In both of these methods, a single crystal is pulled and a raw material solid is descended and melted in the same crucible. A crucible with a large surface area and a shallow bottom is used. Although the crucible can rotate around the central axis, the centers of the pulling axis and the lower axis that supports the crucible do not coincide. However, since the crucible rotates widely, the raw material melt is stirred and the temperature becomes uniform, so there is no problem. In the case of silicon single crystal,
It is relatively easy to grow long single crystals by simultaneous pulling and replenishment. In fact, using this method, 6 pieces with a length of 1 m or more
Silicon single crystals for inch and 8 inch wafers are being pulled. However, it is difficult to apply such a method to a single crystal of a ■-■ group compound semiconductor. In this case, the raw material melt is covered with a liquid sealant in order to suppress the dissociation of group (1), which has a high vapor pressure. When attempting to replenish the raw material solid, it is necessary to prevent Group Ⅰ elements from being removed from the surface of the solid material. The solid supply would then have to be covered with a liquid capsule. As such, Japanese Patent Application No. Sho G1-158897 (published on SG1.7.18) and Japanese Patent Application No. Sho 59-281274 (S59.12.2
9 application)■JP-A-Sho Go-137891 (SGo, 7
．． 23 Published) Patent Application 1982-248971 (55
8, 12, and 24 applications). GaAs is placed in a rotatable crucible 30', which is schematically shown in FIG.
The crucible containing the melt 31 and B20332 as a liquid sealant is supported by the lower shaft and can rotate around the vertical axis. A GaAs single crystal 33 is lifted up from the GaAs melt. Cylinder 34, B20 on the periphery of the crucible
A GaAs polycrystal rod 36 surrounded by 335 is suspended and gradually descends. GaA
The lower end of the s-polycrystal melts and increases the melt. There is an auxiliary heater 37 around the replenishment cylinder 34, and the cylinder 34
It dissolves the B2O2 inside and turns it into a liquid. Of the above ■
This method pulls a long single crystal of non-doped GaAs by continuously replenishing the raw material. (2) has a slightly different purpose; in order to uniformly dope impurities with a segregation coefficient of less than 1, non-doped polycrystals are supplied to prevent the impurity concentration from increasing. There is also a solid raw material in which Ga and As are stored in separate containers and added to the raw material melt through separate routes. ■JP-A Showa Fil-15889Ei (SG1.7.1
8) Patent application 1987-281273 (S59.12
．． (Application No. 29) Figure 3 shows a schematic configuration of this. A container 41 for storing As is added below the crucible 40, and a small hole 42 for As vapor to enter is bored at the bottom of the crucible so that As enters into the crucible from below. A Ga container 44 is located diagonally above the crucible, and a small amount of Ga is introduced into the crucible through a pipe 45. As and Ga react in the raw material melt 43 to form GaA
s It becomes a melt. This is directly synthesizing the feedstock.

[Problem to be solved by the invention]

In the cases of (1) and (2) described above, a polycrystalline raw material such as GaAs must be synthesized in advance. Therefore (i)I
The cost for synthesizing the II-V group compound semiconductor raw material increases. (ii) There is a risk that impurities may be mixed in during the process of synthesizing polycrystalline raw materials for replenishment. Since this is replenished, there is a possibility that the raw material melt for single crystal growth may be contaminated. (i) As shown in FIG. 2, the replenishment solids must be confined within the cylinder along with the 8203 melt. Geometrical constraints limit the volume of replenishment solids to a small size. Due to the small amount of supply, it is not possible to pull up very long single crystals. (iv) The structure becomes complicated because a replenishment mechanism and an auxiliary heater are provided in a narrow space diagonally above the crucible. There are problems such as. In case (2), the supplementary raw material is directly synthesized inside the apparatus, so there is no need for the cost of synthesizing the polycrystalline raw material in advance. However, this has the following drawbacks. (i) In the raw material melt in the crucible, group (1) and group (2) elements combine to form a compound. Since this is an exothermic reaction, if this reaction occurs in the raw material melt, the temperature environment within the melt will be disturbed. Then, the state of the solid-liquid interface is affected. (i) It is difficult to make a small hole in the bottom of the crucible that allows As gas to pass from bottom to top but prevents the raw material melt from leaking. (i) The amount of synthesis is controlled by the amount of Ga supplied. The amount of vaporized As cannot be controlled, and excess As is drawn out of the raw material melt and dissipated into the internal space of the growth container. There are problems such as. The present invention solves these problems and
A method and apparatus capable of pulling a long ■-■ group compound semiconductor single crystal by replenishing the raw material melt into a crucible while reducing the cost for raw material synthesis and preventing the contamination of impurities during raw material synthesis. It is an object of the present invention to provide.

[Means to solve the problem]

The method for growing a compound semiconductor single crystal of the present invention involves a ■-■ group compound raw material melt covered with a liquid sealant in a crystal growth crucible provided in a pulling furnace filled with inert gas. To,
In the method of growing a single crystal by dipping a seed crystal attached to the lower end of a pulling shaft and pulling up the seed crystal while rotating, a sealed container is connected to a crucible for crystal growth through a communication pipe in a pulling furnace. is provided, and continuously feeds group (1) elements and group (2) elements to a crucible for raw material synthesis and supply in the sealed container to synthesize a raw material melt of a group (2)-(2) compound,
This raw material melt is continuously supplied to the crystal growth crucible through a communication pipe, and the inner crucible immersed in the raw material melt of the crystal growth crucible is rotated to grow a single crystal within the inner crucible. The compound semiconductor single crystal growth apparatus of the present invention includes a pulling furnace that can be evacuated and can apply high pressure of inert gas, and a - a crucible for crystal growth containing a raw material melt of a group compound semiconductor and a liquid sealant covering it;
A main heater for heating the raw material melt in the crystal growth crucible, an inner crucible for rotating the raw material melt in the crystal growth crucible, an inner crucible hanging jig for hanging the inner crucible, and an inner crucible. An outer shaft that supports a hanging jig and can be rotated up and down, an inner shaft that pulls up a single crystal of III-V compound semiconductor from the raw material melt by attaching a seed crystal to the lower end, and an inner shaft and an outer shaft. a pulling shaft that can rotate and raise and lower these independently, a sealed container that is a space that is installed inside the pulling furnace and can be sealed, and a communication pipe that is installed inside the sealed container and is connected to the crucible for crystal growth. A crucible for raw material synthesis and supply that communicates with the crucible, a heater that heats the crucible for raw material synthesis and supply, a heater that heats the sealed container, and a group 2 raw material container that accommodates the group M raw material and supplies the group 2 raw material to the crucible for raw material synthesis and supply. , a group-■ raw material container that accommodates the group-■ raw material and supplies the group-■ raw material to the crucible for raw material synthesis and supply, a heater for heating the group-■ raw material, and a flow rate for adjusting the supply amount of the group-■ raw material. It is characterized by an adjustment mechanism.

[For production]

Group ■ raw material container, Continuously from Group ■ raw material container, Group ■ raw material,
Group (2) raw materials are supplied to a crucible for raw material synthesis and supply, where compound raw materials are synthesized. The synthesized raw materials flow into the crucible for crystal growth through the communication pipe. As the single crystal is pulled up, the raw material melt in the crucible for crystal growth decreases, but new raw material melt is replenished, so the liquid level in the crucible for crystal growth must be kept at a constant height. I can do it. In this way, a long single crystal can be grown from the raw material by adding a new raw material.This reduces the cost of single crystal growth.Also, since there is no need to synthesize polycrystalline raw materials in advance, Manufacturing costs can be reduced.Furthermore, since polycrystalline raw materials are not first synthesized and then taken out and stored outside before use, there is no possibility of contamination after synthesis. It is possible to pull up shaku single crystals.

[Example] A compound semiconductor single crystal growth method and a growth apparatus according to an example of the present invention will be explained with reference to FIG. The pulling furnace 1 is a container that can be evacuated and filled with high-pressure gas. In the pulling furnace 1, a crystal growth crucible 2, a sealed container 3, a group V raw material container 19, a pulling shaft 5, and the like are installed. A crucible 2 for crystal growth contains a raw material melt 6 of the ■-■ group. This is heated by a main heater provided on the side of the crucible 2. The surface of the raw material melt 6 is covered with a liquid sealant 8. The pulling shaft 5 has a double structure. A pulling shaft is constituted by an outer shaft 9 and an inner shaft 10 that are arranged concentrically, and both can rotate and move up and down independently. A seed crystal 11 is attached to the lower end of the inner shaft 10. While rotating this, seed it in the raw material melt 6 and then pull it out.■
- Pulling up the single crystal 12 of the ■ group compound. As in the normal LEC method, the inside of the pulling furnace 1 is filled with high-pressure inert gas 13, and pressure is applied to the liquid sealant 8. This is to prevent dissociation of group V elements from the surface of the raw material melt 6. However, unlike the normal pulling method, the crucible 2 for crystal growth is fixed without rotating. In this case, a circumferential temperature distribution will occur in the raw material melt 6, so the rotating inner crucible 14
The inner crucible 14 in which the raw material melt 6 is immersed is a conical container with a hole 15 in the center. This is connected to the outer shaft 9 by an inner crucible hanging jig 4. By rotating the outer shaft 9, the inner crucible 14 can be rotated. Since the raw material melt 6 rotates due to the rotation of the inner crucible 14, the temperature uniformity of the raw material melt in the rotating direction is maintained even if the crystal growth crucible 2 is stationary. A crucible 16 for synthesizing and supplying raw materials is provided inside the sealed container 3 . This is for synthesizing a DI-V group compound raw material inside the pulling furnace 1. A sealed container heater 17 is provided on the outer periphery of the sealed container 3 . There is also a heater 17' for raw material synthesis inside the sealed container. A group ■ raw material container 18 is placed outside the pulling furnace 1, and a group ■ raw material container 19 is placed inside the pulling furnace 1.
There are 1 group raw materials (Ga, In, etc.) and 2 group raw materials (P+ ASN sb, etc.), respectively. The group ■ raw material is in a liquid state from the group raw material container 18 into the pipe 2.
0 and is supplied to the crucible 16 for raw material synthesis and supply. ■
From the group material container 19, the group material is in a gas or liquid state,
The raw material is supplied through the pipe 21 to the crucible 16 for raw material synthesis and supply. B2O3 seals 22 and 23 containing B2O3 in a perforated dish-shaped container are provided at the portions where the M-group pipe 20 and the ■-group pipe 21 penetrate the earthen wall of the sealed container 3. The B2O3 seals 22.23 can isolate the inside of the sealed container 3 from the inside of the pulling furnace 1 while allowing the pipe 20.21 to move up and down. B2O3 seal 22.2
A heater 24 for heating the sealant is provided near 3. A heater 25 for heating the group (2) raw material is provided near the group (1) raw material container 18 if necessary. Further, a flow rate adjustment mechanism 26 is provided at the outlet of the Group 1 raw material container 18, so that the flow rate of the Group 2 raw material can be freely adjusted. A heater 27 for heating the group (2) raw material is also provided near the group (1) raw material container 19. Group (3) raw materials are stored in a solid state, but in the case of PNAS, when heated, a portion of the raw materials becomes gas and passes through the pipe 21 to the crucible 16 for raw material synthesis and supply.
to go into. In this case, since the vapor pressure of the group (1) raw material is determined by the heating temperature, the supply amount can be adjusted by the heating temperature of the heater. In this example, the Group 1 raw material container 19 is located inside the furnace, but it may also be installed outside the furnace. Although the Group (1) raw material container 18 is located outside the furnace, it may be installed inside the furnace. (1) Released gas or (2) Released liquid and (2) Released liquid enter the crucible 16 for raw material synthesis and supply, where they are heated to an appropriate temperature and react to form a -V group compound. Then, it is held in the state of melt 28. This synthetic raw material melt 28 passes through a communication pipe 29 and enters the bottom of the crucible 2 for crystal growth. New raw materials are supplied through the communication pipe 29. A heater 30 is also provided near the communication pipe 29. The relationship between the heights of the raw material melt in the crystal growth crucible 2 and the raw material synthesis and supply crucible 16 is determined from the pressure balance condition. By feeding appropriate amounts of the Group (1) raw material and the Group (2) raw material to the crucible 16 for raw material synthesis and supply, the raw material melt can be supplied in fixed amounts to the crucible 2 for crystal growth. When pulling the single crystal 12, the brightness of the liquid level in the crystal growth crucible can be kept constant by making the supply amount and the pulling amount equal. In other words, the weight of single crystal pulled within unit time is dS/dt
If the weight of one supplementary raw material is dQ/dt, then dt
dt. At this time, the liquid level in the crucible 2.16 remains unchanged. The relationship between the liquid level height is given as follows. Based on the bottom of the crystal growth crucible 2, the height of the raw material melt 6 in the crystal growth crucible 2 is H1, and the height of the synthetic raw material melt 28 in the raw material synthesis supply crucible 16 is K. Let d be the thickness of the liquid sealant 8 in the crystal growth crucible 2. Let the density of the raw material melt be ρ and the density of the liquid sealant be ρ1. Inert gas (N2, Ar,
Ne, --------) partial pressure is P. , the partial pressure of group V element gas is Q. shall be. Of course P. is Q. Much larger. The inert gas partial pressure in the internal space of the sealed container 3 is p,
Let the y-group element gas partial pressure be Ql. B2O3 seal 22.
Let Δ be the difference in pressure between the inside and outside at 23. The case where the pressure inside the sealed space 3 is higher is defined as Δ>O. The pressure balance is Po + Qo + dg + ρoHg = P++Q+
It is given by 1ρokg−Δ ■. g is the gravitational acceleration. Δ is limited by the thickness of the B2O3 seal, the diameter of the hole, etc., but is not necessarily O. If the gas pressures are the same and Δ;O, then ρId
= ρo(K −H) (3). The thickness d of the liquid sealant is fixed because it is determined by the amount initially put into Rupo 2. If the liquid level K of the raw material melt 28 in the raw material synthesis supply crucible 16 is constant, the liquid level H of the crystal growth crucible 2 is constant. The optimum mode for implementing the present invention is that K is constant and H is constant;
A mode in which the value is changed is also possible. When pulling a non-doped single crystal, it is sufficient to keep constant and H=constant, or when doping with impurities, K is constant at a constant rate.
It is better to reduce When raising a single crystal doped with an impurity with a segregation coefficient k smaller than 1, dt is used to keep the impurity concentration constant.
What is necessary is to set the relationship between the replenishment amount and the pulling amount, such as dt. Since the replenishment amount is smaller than the withdrawal amount, the liquid level gradually decreases. However, when k is small, this change is slight. Even in such cases, long single crystals can be pulled. Next, an example will be described in which the method and apparatus of the present invention are applied to pulling a non-doped GaAs single crystal. Therefore, what was previously referred to as group Ⅰ raw material container 18 is
The A raw material container 18 and the group II raw material container 19 will be written as the As raw material container 19. First, let's talk about the materials of the device. The crystal growth crucible 2 was a PBN crucible with a diameter of 6 inches. The sealed container 3 was a quartz container whose inner and outer surfaces were coated with PBN. The raw material synthesis supply crucible 16 in this is PB
It is made by N. The crystal growth Ruppo 2 and the crucible 16 for raw material synthesis and supply are connected through a PBN communicating pipe. The As raw material container 19 is made of carbon and has an inner surface coated with PBN. The Ga raw material container 18 is a carbon container provided outside the furnace, and its inner surface is coated with PBN. There are B2O3 chambers 22 and 23 in the upper part of the sealed quartz container 3, in which an appropriate amount of B2O3 was stored. The inner shaft 14 connected to the outer shaft 9 of the pulling shaft 5 is made of carbon, and its inner and outer surfaces are coated with PBN. Next, the crystal pulling operation will be explained. Crystal growth crucible 2 contains 5 kg of GaAs polycrystal and 700 g of B2.
It contained O3. At this time, a part of the GaAs polycrystal was placed so as to close the connecting hole of the circular pipe. A Ga raw material container 18 located outside the furnace contained 3 kg of Ga. As raw material container 19 in the furnace contained 5.4 kg of As. The molar ratio of Ga raw material and As raw material for replenishment is 1:1
．． It is 005. This is because the proportion of As is slightly increased in anticipation of loss of As due to decomposition. A seed crystal 11 is attached to the lower end of the inner shaft 10 of the pulling shaft 5. An inner crucible 14 is suspended from the outer shaft 9 via an inner crucible hanging jig 4. Once the inside of the pulling furnace 1 is evacuated, nitrogen (N2
) Filled with gas to a predetermined pressure. The entire sealed container 3 was heated by the heater 17 and controlled so that the lowest temperature part including the inside of the container 3 was 617°C. This is the temperature at which the vapor pressure of As becomes approximately 1 atmosphere. Since the vapor pressure of As is determined by the lowest temperature in a closed space, the lowest temperature is set to l1i17'C. Next, the main heater 7 melts B2O3, the liquid sealant of Ruppo 2 for crystal growth, and the raw material GaAs, and
The raw material melt was covered by No. 3. A part of this raw material melt flowed back through the communication pipe 29 and into the crucible 16 for raw material synthesis and supply. The liquid level in the crucible 16 increases and the pipe 20.21
The lower end of the was submerged in the melt. The heaters 25 and 27 were energized to heat the Ga1As raw material. The temperature of the As raw material container 19 was set to 617°C, and then
The temperature of the s-feeding pipe 21 was also maintained above this level. The flow rate adjustment mechanism 26 was adjusted so that the Ga raw material descended from the Ga raw material container 18 in appropriate amounts. The height of the outer shaft 9 of the pulling shaft was adjusted to position the inner crucible 14 in the raw material melt. Inner shaft: 3rpm, outer shaft: 10p
They were rotated in opposite directions at a speed of pm. Thereafter, only the inner shaft 10 was lowered, the seed crystal 11 was immersed in the raw material melt 6 for seeding, and then crystal growth was started. Following the seed crystal, a GaAs single crystal 12 grows. The height of the liquid level of the raw material melt in the crystal growth crucible 2 is kept constant. For this reason, the Ga raw material was continuously supplied in a constant amount so that the amount of GaAs synthesized per unit time was balanced with the amount of GaAs pulled. The As raw material is supplied as a gas at about 1 atm. Since GaAs is synthesized by supplying Ga, the amount of synthesis can be controlled by controlling the amount of Ga supplied. As long as the As partial pressure is controlled to about 1 atmosphere, the GaAs melt is maintained at a stoichiometric composition. A GaAs single crystal having a diameter of 3 inches and a length of 21 inches was grown by the method of the present invention. This is a long single crystal that cannot be obtained using conventional methods. This single crystal was semi-insulating throughout and had uniform properties. Effects of the Invention In the present invention, group (I) and group V elements are synthesized inside a furnace and supplied as a compound into a crucible for crystal growth. Since raw materials are supplied into the crucible, long single crystals can be grown. - The cost can be reduced compared to when the compound is synthesized first and then used as a supplementary raw material. Furthermore, since contamination with impurities can be prevented, a highly pure single crystal can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic longitudinal sectional view of a compound semiconductor single crystal growth apparatus according to an embodiment of the present invention. FIG. 2 is a schematic vertical cross-sectional view of a single crystal growth apparatus disclosed in Japanese Patent Application Laid-Open No. 158897/1997. FIG. 3 is a schematic longitudinal cross-sectional view of a single crystal growth apparatus disclosed in Japanese Patent Application Laid-Open No. 158896/1983. 1 ,,, Drawing furnace 2 ,,,
, crucible for crystal growth 3 , sealed container 4 ,
, Inner crucible hanging jig 5 , Pulling shaft 6 , Raw material melt 7 ,
Main heater 8 Liquid sealant 9 Outer shaft 10
Inner axis 11, Seed crystal 12, Single crystal 13, Inert gas 14゜15゜16. 17°17' 18°19°20°21. 26. 27゜28゜29゜30゜Inventor

Claims (2)

[Claims] (1) The lower end of the pulling shaft was attached to the III-V compound raw material melt covered with a liquid sealant in a crystal growth crucible installed in a pulling furnace filled with inert gas. In the method of growing a single crystal by soaking a seed crystal and pulling up the seed crystal while rotating, a sealed container connected to the crystal growth crucible by a communicating tube is provided in the pulling furnace, and the sealed container is Group III elements and Group V elements are continuously supplied to the crucible for raw material synthesis and supply inside to synthesize a raw material melt of III-V group compounds, and this raw material melt is continuously passed through a communication pipe for crystal growth. A method for growing a compound semiconductor single crystal, the method comprising growing a single crystal in an inner crucible while rotating the inner crucible, which is supplied to a crucible and immersed in a raw material melt of the crucible for crystal growth. (2) A pulling furnace that can be evacuated and apply high pressure of inert gas, and a
- A crystal growth crucible containing a raw material melt of a group V compound semiconductor and a liquid sealant covering it, a main heater for heating the raw material melt in the crystal growth crucible, and a raw material for the crystal growth crucible. An inner crucible for rotating the melt, an inner crucible hanging jig for hanging the inner crucible, an outer shaft that supports the inner crucible hanging jig and can be rotated up and down, and a seed crystal attached to the lower end. from the raw material melt by pulling it up.
an inner shaft for pulling up a single crystal of a III-V compound semiconductor;
A pulling shaft that includes an inner shaft and an outer shaft and can rotate them up and down independently, a sealed container that is a space that can be sealed and installed inside the pulling furnace, and a communication pipe installed inside the sealed container that allows crystallization to be carried out. A crucible for raw material synthesis and supply that communicates with the growth crucible, a heater that heats the crucible for raw material synthesis and supply, a heater that heats a sealed container, and a group III raw material that accommodates the crucible.
A group III raw material container for supplying the group III raw material to the crucible for raw material synthesis and supply, a group V raw material container for storing the group V raw material and supplying the group V raw material to the crucible for raw material synthesis and supply, and heating the group V raw material. 1. A compound semiconductor single crystal growth apparatus characterized by comprising a heater for the growth of a group III raw material, and a flow rate adjustment mechanism for adjusting the supply amount of a group III raw material.