JPS6127358B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for growing a single crystal of a compound semiconductor having a volatile component as one of its constituent elements while keeping the stoichiometric composition constant. This method is designed to produce a high-quality compound semiconductor crystal with a more uniform stoichiometric composition throughout the crystal with good reproducibility.

In recent years, high-purity undoped semi-insulating GaAs has been attracting attention as a substrate single crystal for GaAs integrated circuits, but on the other hand, various defects that are thought to be caused by slight deviations in the stoichiometric ratio have also been observed. It has been pointed out. This undoped semi-insulating GaAs single crystal has conventionally been grown using the following two methods. In other words, (1) GaAs polycrystals having a stoichiometric composition are first synthesized using a boat made of SiO ₂ by the Bridgeman method, etc., and then the above polycrystals are synthesized.
Liquid sealant in _SiO2 or BN crucible
The so _{- called} liquid encapsulation high-pressure melting and pulling method (Liquid Encapsucation
Czochealshi: LEC) and undoped semi-insulating
A method for growing GaAs single crystals: (2) high-purity Ga, which is the raw material for GaAs, and As are directly weighed and filled into a SiO ₂ or BN (boron titanide) crucible at a stoichiometric composition; In this method, liquid sealing material B ₂ O ₃ is placed in the same crucible and GaAs is directly synthesized and melted under about 100 atmospheres, and then the pressure is reduced to several atmospheres and a single crystal is pulled and grown using the LEC method.

Although the typical manufacturing methods described above yield semi-insulating GaAs single crystals with large diameters, method (1) has the disadvantage that there are many impurities such as Si in the polycrystalline GaAs used ( In 2), As is synthesized with GaAs under high pressure and high temperature (100 atm, 1250°C).
GaAs melt with high volatilization and stoichiometric composition,
Therefore, a major drawback is that single crystals with stoichiometric composition cannot be obtained with good reproducibility. Further above
A common problem in methods (1) and (2) is that although single crystal growth is performed under several to several tens of atmospheres, As, a volatile component of group V, passes through the molten B ₂ O ₃ layer. It has been pointed out that when grown for a long time, the Ca/As ratio gradually changes along the crystal growth direction, and the yield as a GaAs IC substrate decreases.

For this reason, for example, in the method for producing compound crystals containing volatile components disclosed in Japanese Patent Publication No. 55-23798, a partition wall is provided between the space filled with the vapor of the volatile component and the inert gas space for applying high pressure. A method of automatically eliminating the pressure difference to prevent loss of volatile components has also been proposed. However, this method has the disadvantage that the lifting device is complicated.

Compound semiconductors containing other volatile components, e.g.
- group compound semiconductors such as Inp and InAs, -
Similarly to the case of GaAs, it has been difficult to control the suppression of volatile components in group and - group compounds.

The present invention aims to eliminate these drawbacks. Specifically, when producing a single crystal using the liquid-encapsulated melt pulling method (LEC method), by supplying all or part of the volatile elements into the melt from the outer wall of the crucible, the amount of volatile elements present in the melt can be controlled. An object of the present invention is to provide a method of manufacturing a compound semiconductor crystal with a constant stoichiometric composition ratio and a manufacturing apparatus thereof.

Therefore, the compound semiconductor single crystal production apparatus according to the present invention includes a crucible for storing a compound semiconductor raw material melt and a liquid sealant, and a device for bringing a seed crystal into contact with the melt and pulling the single crystal. A compound semiconductor single crystal manufacturing apparatus having a susceptor that supports the crucible in a vertically movable manner, and a heating means that can independently heat the upper and lower parts of the crucible, and an inner crucible made of a porous material for storing a liquid sealant and having ribs on the upper periphery; a space for storing a volatile raw material between the inner crucibles is formed on the outside of the inner crucible; an outer crucible that is provided in engagement with the rib so that the upper part is covered with a liquid sealant; It is characterized by the fact that it can be divided into four parts.

According to the present invention, part or all of the volatile elements are supplied into the melt through the porous wall of the crucible filled with the raw material melt, so that the volatile components of the volatile elements are supplied from the outer wall of the crucible. Therefore, a single crystal is grown from a melt having a certain composition ratio. Therefore, a single crystal with good properties can be obtained with good reproducibility.

The present invention will be explained in more detail.

FIG. 1 is a cross-sectional view of one embodiment of the manufacturing apparatus according to the present invention, in which 1 is a porous inner crucible filled with a compound semiconductor melt and a liquid sealing material (B ₂ O ₃ etc.); 3 is a quartz sleeve crucible that is housed inside the outer crucible 2; 4 is a porous crucible 1 and a quartz sleeve crucible 3; 5 is a compound semiconductor melt, 6 is a mass of volatile elements that are constituents of the compound semiconductor melt 5, 7 is a liquid sealing material B ₂ O ₃ layer, 8 is a single crystal, 9 is a rib. A rib 9 is attached around the upper end of the porous crucible 1, and an inner space 4 is formed between the rib 9 and the quartz sleeve crucible 3. FIG. 2 is a schematic diagram (a) of a single crystal pulling apparatus using a double-structured crucible C according to the present invention and its vertical temperature distribution (b). In Figure 2, 10 is an upper heater that heats the porous crucible 1, 11 is an outer crucible 2, and a lower heater that heats the volatile elements placed in the bottom, 12 is a crystal rotation and pulling shaft, and 13 is a double crucible ( 1, 2, and 3) A susceptor that supports C and can be rotated and moved up and down, 14 is a pressure chamber, 15 is a crystal observation window,
16 is an inert gas inlet for pressurization, and 17 is a gas distribution plate. Note that since the upper heater 10 and the lower heater 11 can be controlled independently (the temperature control system is omitted from the figure), the temperature distribution shown in FIG. 2b can be created arbitrarily. The vapor pressure of the volatile components within the inner space 4 of the porous crucible 1 is controlled by the heating temperature of the lower heater 11. Therefore, melt 5
There is an advantage that the compensation for the volatile components that evaporate through the liquid sealing material 7 can be optimally selected depending on the set temperature of the lower heater 11. Further, if the vapor of the volatile components in the inner space 4 is excessive, it will be dispersed through the porous ribs 9 made of the same material attached to the upper circumference of the porous crucible 1.

In the manufacturing apparatus according to the present invention, the single crystal manufactured is not fundamentally limited, and any compound semiconductor single crystal containing a volatile component may be used. For example, − family, −
group, - group compound semiconductor single crystal, specifically
It is possible to effectively grow GaAs, InP, InAs, GaP, InGaP, InGaAs, etc.

The effects of the manufacturing apparatus according to the present invention will be explained below.
This will be explained using an example of single crystal production. Example 1 Fig. 3 illustrates the process of a single crystal manufacturing method carried out using a double crucible C and a furnace configuration according to the present invention. Parts other than the heater 10 and lower heater 11 are omitted.

First, as shown in Fig. 3a, As6', a volatile element to be compensated, is placed in the outer crucible 2 (actually, the quartz sleeve crucible 3), and the porous crucible 1 (hereinafter referred to as the inner crucible) is placed in the outer crucible. Put it in 2. and,
In order to synthesize GaAs, raw materials are placed in the inner crucible 1.
Ga18 and As19 are weighed and filled in a stoichiometric ratio. Next, a disk-shaped B ₂ O ₃ (solid) 7' having a thickness of approximately 1 cm that matches the inner diameter of the outer crucible 2 is placed. At this time, the relative position of the entire double crucible C and the upper heater 10 is adjusted using the susceptor 13 (not shown) so that the solid B ₂ O ₃ 7' is located in the lower half of the center of the upper heater 10. Then, the upper heater 10 is energized to melt only the B ₂ O ₃ 7' and cover the raw materials Ga 18 and As 19 as shown in FIG. 3b. Next, the susceptor 13 is raised while rotating (approximately 5 rpm) to melt Ga and energize the upper heater 10 to synthesize the GaAs melt 5 (Figure c). At this time, the pressure inside the chamber 14 (Fig. 2) is approximately 100
It was taken as atmospheric pressure. Inner crucible temperature to GaAs melting point ~1230
Hold the crucible and heater slightly above 10°C.
By completely entering the chamber 14, the temperature of the synthesized GaAs melt 5 is stabilized, and the pressure inside the chamber 14 is gradually lowered to about 5 atmospheres (Figure d). At this time, the temperature of the compensation As portion is raised to a set temperature by the lower heater 11. After holding it for a certain period of time, the rotating pulling shaft 12 (Fig. 2)
A GaAs seed crystal dipped in molten B ₂ O ₃ is passed through 7
A single crystal of Cr was pulled and grown by immersing it in GaAs melt 12 (Figure e).

In this process, in the process from c to d, even if the pressure inside the chamber 14 is higher than the vapor pressure of the raw material As 19, there is a slight volatilization, and even during the growth of e, B ₂ O ₃ 7 is removed from the GaAs melt 5. Discrete through. However, according to the present invention, the compensation As 6' is filled into the inner space 4 by the heating of the lower heater 11,
It diffuses into the GaAs melt with a low As concentration through the porous walls (side walls and bottom wall) of the inner crucible 1, and the stoichiometric ratio is maintained by convection within the melt.

In the above example, a high-purity undoped semi-insulating GaAs single crystal (specific resistance 10 ⁷
Ωcm or more) was easily obtained.

Example 2 This will be explained using Figure 4. In the figure, components other than the quartz sleeve crucible 3 and the upper and lower heaters 10 and 11 are omitted. A large amount of raw materials As19 in the outer crucible
, insert the inner crucible 1, and put only the raw material Ca18 and solid B ₂ O ₃ 7' into the inner crucible 1. The relative positions of the upper and lower heaters 10, 11 and the double crucible C are as shown in FIG.
The As 19 is installed in advance so that each of the heaters 10 and 11 can heat it. Next, the upper heater 10 is
The temperature is raised to near the melting point of GaAs, and a Ga melt 20 and a molten B ₂ O ₃ layer 7 are formed. And lower heater 1
The raw material As19 is kept at the set temperature T1, which is electrically connected to _1.
is volatilized and the inner space 4 is filled with As vapor. At this time, the pressure inside the chamber 14 is determined by the temperature T ₁
Keep it higher than the As vapor pressure. In this way, the As vapor filling the inner space 4 diffuses into the high temperature Ga solution 20 through the porous wall of the inner crucible 1.
GaAs saturated melt is synthesized. At this time, the Ga melt 20 contains As and becomes the GaAs melt 5 whose volume is about twice that of the GaAs melt 5 (Fig. b→c).
It is necessary to reduce the amount in advance.
After the GaAs melt 5 was synthesized, single crystal growth was performed in the same manner as in Example 1 using seed crystals. In the above process
Excess As vapor in the inner space 4 after the GaAs saturated melt 5 is synthesized is dispersed through the ribs 9 around the inner crucible 1, and the As vaporized from the surface of the GaAs melt 5 during crystal growth is Similarly, compensation is made through the side walls and bottom wall of the inner crucible 1, and the stoichiometric composition of the GaAs melt 20 is always maintained. In this way, a highly pure semi-insulating GaAs single crystal with few impurities was obtained.

As seen in the above example, the vapor of the volatile components filling the inner space diffuses into the melt through the inner crucible wall and is dispersed through the ribs 9 provided around the upper end of the inner crucible. This can be suppressed by making the pressure inside the chamber 14 higher than the vapor pressure of the volatile component compensating element 6 heated by the lower heater 11 at that temperature.
In addition to this, for example, as shown in Figure 5,
A sleeve crucible 2 is provided with a quartz rib 21 having the same size as the rib 9 of the porous crucible 1 at the upper end of the quartz sleeve crucible 3 that is tightly inserted into the outer crucible 2.
2 may be used. In addition, in the above example, the depth of the GaAs melt decreases as the crystal grows, and therefore the B ₂ O ₃ layer also falls into the inner crucible 1, so there is no B ₂ on the rib 9 of the inner crucible. It is also conceivable that no O ₃ remains and that the volatile components from the ribs 9 become more dispersed. In addition to using the quartz sleeve 22 shown in FIG. 5, for example, a porous crucible 23 as shown in FIG. 6 may be used to suppress the scattering. That is, since B ₂ O ₃ remains in the space 25 formed by the ribs 24 of the outer crucible 2 and the inner crucible 23 and external pressure is applied efficiently, the dispersion of volatile component vapor through the ribs 24 can be prevented.

In the above example, GaAs, a - group compound, was described, but the present invention can also be applied to the crystal growth of other compound semiconductors that have volatile elements as one of their constituents, such as GaP, InP, InAs, InGaP, and InGaAs. It is clear from these examples that high purity single crystals can be produced. Furthermore, it can be easily inferred that the same holds true for - groups other than - groups and - group compounds.

In the above example, BN is used as the material of the porous crucible 1.
However, not only BN but also porous AlN,
Al ₂ O ₃ , carbon, etc. have exactly the same effect, and the present invention does not specify the material of the crucible.
In addition, it is possible to first melt the solid solid B ₂ O ₃ in Example 1 using other methods, and the pressure in the crystal growth chamber, as well as the crystal growth conditions such as crystal rotation, susceptor rotation, and susceptor elevation, may also be changed. It is not subject to any restrictions. Furthermore, it is possible to produce a high-purity single crystal to which impurities have been added by inserting the added impurities into the inner crucible 1 together with the raw material.

According to the present invention, since the volatile element vapor constituting the compound semiconductor is diffused into the melt through the outer wall of the crucible, there is an advantage that a stoichiometric composition can be realized.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an embodiment of the compound semiconductor single crystal manufacturing apparatus according to the present invention, FIG. 2 is a cross-sectional view of a more specific embodiment of the compound semiconductor single crystal manufacturing apparatus according to the present invention, and FIG. FIG. 4 is an explanatory diagram for explaining the operation of the manufacturing apparatus according to the present invention, FIG. 5 is a sectional view showing another embodiment of the crucible used in the present invention, and FIG. 6 is a third cross-sectional view of the crucible used in the present invention. FIG. 1... Porous crucible (inner crucible), 2... Outer crucible, 3... Quartz sleeve crucible, 4... Inner space, 5... Compound semiconductor melt, 6... Mass of compensating volatile component, 7... Molten B ₂ O ₃ , 8... Single crystal,
9...Rib, 10...Upper heater, 11...Lower heater, 12...Crystal rotation and pulling shaft, 13...Susceptor, 14...Pressure chamber, 15...Observation window, 16...Gas inlet , 17... gas distribution plate,
18... Raw material Ga, 19... Raw material As, 7'... Solid
B ₂ O ₃ , 20...Ga melt, 21...quartz rib, 2
2... Sleeve crucible with quartz ribs, 23... Porous crucible, 24... Ribs, 25... Space created by the ribs 24 and the outer crucible.

Claims (1)

[Claims] 1. In a compound semiconductor single crystal manufacturing apparatus having a crucible for storing a compound semiconductor raw material melt and a liquid encapsulant, and a device section for bringing a seed crystal into contact with the melt to pull up the single crystal, the crucible is moved up and down. a susceptor capable of supporting the crucible; and a heating means capable of independently heating the upper and lower parts of the crucible; an inner crucible made of wood, a space formed outside the inner crucible for storing volatile raw materials between the inner crucibles, and provided in engagement with the ribs so that the liquid sealant covers the upper part of the ribs. and an outer crucible formed by the inner crucible and the outer crucible, and the rib is configured to disperse an excess amount of volatile raw material vapor stored in the space formed by the inner crucible and the outer crucible. Crystal manufacturing equipment.