JPH02289487A - Production of single crystal of compound semiconductor - Google Patents

Abstract

PURPOSE:To prevent the damage of a quartz tube and the unfixing of starting material and a seed crystal by setting carbon cloths at both noncontact ends of the starting material and the seed crystal and putting them in the quartz tube when a single crystal is grown by a floating zone melting method in a weightless state in space. CONSTITUTION:Carbon cloths 7 are set at both noncontact ends of a polycrystal 3 as starting material and a seed crystal 2, they are put in a quartz tube 1 and this tube 1 is sealed with a quartz cap 9. The sealed tube 1 is placed in a growth furnace and this furnace is carried in a means of transfer to space such as a space shuttle. A single crystal of a compd. semiconductor is grown by a floating zone melting method in a weightless state in space.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing a compound semiconductor single crystal, and particularly to a method for producing a compound semiconductor single crystal by a floating zone melting method (also referred to as a float zone method or FZ method). This invention relates to a manufacturing method that improves the method of sealing a sample into a quartz reaction tube.

(Prior art) In the floating zone melting method, as shown in FIG. 2, the raw material polycrystal 3 and the seed crystal 2 are stored in a raw material charging container such as a raw material crucible in the Czochralski method or a boat in the boat method. It is fixed in the quartz reaction tube (hereinafter abbreviated as quartz tube) 1 without contacting the inner wall.

For example, in the case of Pb5nTe growth, this fixation is performed by solidifying one end of the raw material polycrystal 3 and the seed crystal 2 with Pb indicated by 6 in the figure.

After the raw material polycrystal 3 and the seed crystal 2 have been sealed in the quartz tube 1, the quartz tube 1 is vertically installed in the growth furnace. As shown in FIG. 3, crystal growth is performed by irradiating the raw material polycrystal 3 with light 8 from light sources installed on the left and right sides of a growth furnace (not shown) and melting it. First, melting of the raw material is started from the joining region between the raw material polycrystal 3 and the seed crystal 2. The quartz tube 1 can be moved upward, and if the raw material polycrystal 3 is gradually melted from the seed crystal 2 as shown in FIG. 3, it is possible to grow a single crystal. Furthermore, this method generally yields a single crystal with less contamination of oxygen and the like.

However, if such a method is carried out under gravity,
Dripping of the raw material melt occurs, and only a single crystal with a small diameter can be obtained. Therefore, in order to obtain a single crystal with a certain diameter, it is necessary to grow the crystal under zero gravity. In reality, from this point of view, it is possible to produce single crystals using the floating zone melting method in zero gravity in space.
It is considered.

[Problem to be solved by the invention]

As described above, in the conventional method, the raw material polycrystal and the seed crystal are fixed in the quartz tube by solidifying molten Pb.

When molten Pb solidifies, Pb itself expands, or when a certain amount of mechanical vibration is applied to the quartz tube, Pb is damaged, causing the raw polycrystals and seed crystals to become unfixed, and the quartz tube to be damaged. Occasionally, it would break.

By the way, when considering single crystal manufacturing in outer space as mentioned above, it is difficult to carry out all the steps from the beginning in zero gravity due to the narrowness of the work space and the uncertainty of working in zero gravity. Because this is extremely difficult, it is necessary to securely perform steps such as fixing the raw polycrystals and seed crystals in the quartz tube on the ground. However, it is a well-known fact that when moving from ground gravity to space gravity, it is impossible to avoid quite severe vibrations, and with conventional methods there is a great risk of the quartz tube becoming unfixed or cracking.

The present invention eliminates the drawbacks of the conventional method as described above, and eliminates vibrations during movement from ground gravity to space gravity, which are unavoidable when growing single crystals by the floating zone melting method in zero gravity. It is an object of the present invention to provide a method that can prevent damage to a quartz tube or unfixation of raw materials and seed crystals due to this method, and thereby can stably produce compound semiconductor single crystals.

[Means to solve the problem]

The present invention is a compound semiconductor manufacturing method in which a single crystal is grown in zero gravity without using a container by the floating zone melting method. This method of manufacturing a compound semiconductor single crystal is characterized in that when the material and the seed crystal are encapsulated in contact with each other, carbon cloth is placed on both sides of the other ends of the raw material and the seed crystal that are not in contact with each other.

[Effect]

The present invention will be specifically explained with reference to the drawings. FIG. 1 is a diagram showing an embodiment of the present invention, in which a raw material polycrystal 3 and a seed crystal 2 are sealed in a quartz tube 1 in the same state as in the conventional method. A carbon cloth 6 is inserted into each end of the quartz tube 1, and the outer periphery of the opening of the quartz tube 1 is sealed and fixed with a quartz tube sealing cap 9, so that vibrations from the outside are alleviated. In the illustrated example, the outer periphery of the opening of the quartz tube and the inner periphery of the sealing cap are threaded with the same pitch, and the two are screwed together. Also,
Since the inner diameter of the quartz tube l is made to be approximately close to the outer diameter of the seed crystal 2 and raw material polycrystal 3, even if the seed crystal 2 and raw material polycrystal 3 are enclosed in the quartz tube without being fixed, These positions are so thick that it causes problems in growing single crystals (they do not shift).

The work of enclosing the carbon cloth 6, the seed crystal 2, and the raw material polycrystal 3 into the quartz tube 1 is carried out in a place where almost no vibration occurs under ground gravity, considering the reliability of the work. After being sealed, the quartz tube is placed in a growth furnace and transported into a means of transport (for example, a space shuttle) under zero gravity in space. It is expected that the quartz tube will be subjected to severe mechanical vibrations during the transition from ground gravity to space gravity. At this time, in the case of the conventional method of fixing raw material polycrystals and seed crystals to a quartz tube with PB, cracks in the quartz tube, raw material polycrystals,
Seed crystals may become unfixed.

However, when the encapsulation according to the present invention is carried out, no unnatural force is applied to the quartz tube, the raw material polycrystal, and the seed crystal due to the encapsulation, and due to the relaxing effect of the carbon cloth, external mechanical vibrations are absorbed by the raw material polycrystal. , since it does not reach the seed crystal,
Such troubles are almost eliminated, the single crystal growth apparatus can be safely transported to a zero gravity state, and single crystal growth of a desired composition can be realized.

〔Example〕

EXAMPLE When seed crystals and raw material polycrystals were sealed in a quartz tube according to the present invention, a vibration experiment was conducted to examine to what extent the quartz tube was prevented from cracking or becoming unfixed due to mechanical vibration.

Seed crystal log by conventional Pb fixation method.

Quartz tube (size 30a+m) containing 40g of raw material polycrystal
φX 70 mm) (comparative example) and 10 quartz tubes of the same size (example) in which carbon cloth was placed at both ends according to the present invention and the same seed crystal and raw material polycrystal as in the comparative example were sealed. Then, each quartz tube was subjected to a vibration intensity of 5 g (this is the vibration intensity that the quartz tube is thought to receive when being transported from the ground gravity to the space gravity, and the seed crystal and raw material polycrystal to the quartz tube This is the highest vibration intensity that a quartz tube receives from the time of filling until the end of crystal growth. When we investigated whether or not the IO had come off, it was confirmed that cracks in the quartz tube or the fixation of raw material polycrystals and seed crystals had come loose in 5 out of IO in the conventional method, but in 1 out of 10 in the case of the present invention. didn't exist either.

〔Effect of the invention〕

As explained above, the present invention solves the problem of quartz tube damage caused by vibration during movement from ground gravity to space gravity, which is unavoidable when growing single crystals by the floating zone melting method under thermal lightning horns. Alternatively, it is effective in preventing the fixation of the raw material polycrystal and the seed crystal from becoming unfixed, thereby ensuring stable production of compound semiconductor single crystals.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram for explaining an embodiment of the present invention, and FIGS. 2 and 3 are schematic diagrams for explaining a conventional method. 1 is a quartz tube, 2 is a seed crystal, 3 is a raw material polycrystal, 4 is a raw material melt, 5 is a single crystal, 6 is a solid t'b, 7 is a carbon cloth, 8 is a light, 9 is a quartz tube sealing cap represents.

Claims (1)

[Claims] In a method for producing a compound semiconductor in which a single crystal is grown in zero gravity without using a container by the floating zone melting method, raw materials and seed crystals are placed together in a quartz reaction tube prior to growth in zero gravity. 1. A method for producing a compound semiconductor single crystal, which comprises placing carbon cloth on both sides of the other ends of the raw material and seed crystal that are not in contact with each other and enclosing the raw material and seed crystal in contact with each other.