JPH0465388A - Growing method for single crystal - Google Patents

Abstract

PURPOSE:To easily obtain single crystal free from generation of a strain by regulating the composition of melt for a raw material to the composition of specified amount deviated from the stoichiometric composition of single crystal to be grown and performing growth of single crystal in a specified mode. CONSTITUTION:Metallic Ga and metallic As being a raw material and B2O3 being a sealer are introduced into a crucible made of boron nitride and heated. In this case, when the composition of the raw material is shown in Ga1-xAsx, X is 0.515(deviation for the whole is regulated to 3 mol%). The raw material is synthesized while holding the temp. constant at about 800 deg.C and thereafter the temp. is raised to melt the raw material. Seed crystal 2 is cut off from GaAs single crystal and held to a seed crystal holder 1. This seed crystal 2 is stuck on the surface of the melt 4 of GaAs for the raw material through a liquid sealer 3. The temp. of melt 4 is controlled and also while the seed crystal 2 is rotated, it is pulled up to grow single crystal 6. Before growth of single crystal 6 is completed, pulling-up of seed crystal 2 is midway stopped. Thereafter the temp. of the crucible is slowly controlled and successively growth of single crystal is performed.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is applicable to semiconductor single crystals such as gallium arsenide and silicon, oxide single crystals such as bismuth germanate, cadmium tungstate, zinc tungstate, and gadolinium silicate. Regarding the training method.

(Prior Art) The Czochralski method is a method suitable for growing high-purity, high-quality single crystals.

As shown in Figure 2, in the Czochralski method, the raw material in a crucible 5 is melted by high-frequency heating, etc., and then a seed crystal 2 is brought into contact with the melt 4, and pulled up while rotating while controlling the temperature, followed by the seed crystal. This is a method of growing crystals. During pulling, a method is usually used to detect changes in the weight of the crystal or melt system, feed it back to the power supply to precisely control the temperature of the melt, and automatically control the diameter of the grown single crystal 6. ing.

(Problem to be solved by the invention) Although the above-mentioned Czochralski method yields a cylindrical single crystal and has good product collection efficiency, it does not measure the weight change of the grown single crystal and force the temperature of the crucible. The diameter of the single crystal must be controlled by changing the diameter of the single crystal, and there is a problem in that distortion is likely to occur inside the single crystal due to temperature changes.

In the production of single crystals, it is necessary that the grown single crystals be easily removed from the melting hole.

The present invention provides a method for growing a single crystal in which a single crystal is not strained due to temperature changes inside the single crystal, and which is easy to remove from a crucible.

(Means for Solving the Problems) The present invention provides a method for growing a single crystal in which a seed crystal is brought into contact with a raw material melt in a crucible, and a crystal following the seed crystal is grown while pulling the seed crystal. The composition is shifted by 0.5 to 5 mol% from the stoichiometric composition of the single crystal to be grown, the pulling of the seed crystal is stopped midway before the growth of the single crystal is completed, and the temperature of the crucible is then gradually lowered. The single crystal growth is controlled to continue to grow.

In the present invention, the composition of the raw material melt is shifted by 0.5 to 5 mol% (with respect to the whole) from the stoichiometric composition of the single crystal to be grown, but the value varies depending on the type of raw material, the type of single crystal, and the stoichiometric composition of the single crystal to be grown. It is determined by taking into account the crystal growth conditions, single crystal growth direction, crucible diameter, etc.

In the present invention, pulling of the seed crystal is stopped halfway before the growth of the single crystal is completed, but it is preferably stopped when 10 to 20% of the entire melt has grown as a single crystal. However, the timing to stop pulling the seed crystal is determined by taking into account the type of raw material, the growth direction of the single crystal, the diameter of the crucible, and other equipment restrictions.

After stopping the pulling of the seed crystal, the temperature of the crucible is gently controlled, for example, the temperature of the crucible is slowly cooled with a temperature gradient of 10 to 200 degrees per hour, and the growth of the single crystal is continued.

Pulling up the seed crystal means pulling up the seed crystal relative to the movement of the crucible, and stopping pulling the seed crystal means stopping the seed crystal relative to the movement of the crucible. It means that.

While pulling the seed crystal, the seed crystal and/or the rutsuho may be rotated. Preferably, the seed crystal is rotated relative to the base.

After stopping the pulling of the seed crystal, the seed crystal may be rotated relative to the crucible until the grown single crystal reaches the crucible wall, or the rotation may be stopped. After the grown single crystal reaches the crucible wall, the seed crystal cannot be rotated relative to the crucible, but the seed crystal and crucible can be moved in the same direction.
They may rotate at the same rotation speed.

After stopping the pulling of the seed crystal, it is desirable to allow the growing single crystal portion to reach the crucible wall and to further monocrystallize all of the melt, since a cylindrical single crystal can be obtained and the product collection efficiency is high.

(Function) If the composition of the raw material melt is shifted from the stoichiometric composition of the single crystal to be grown, a part of the raw material corresponding to the excess composition will precipitate around the single crystal in the final stage of single crystallization. It is believed that the generation of stress due to contact with the crucible is weakened, which allows the single crystal to be easily removed from the crucible and prevents the single crystal and the crucible from cracking.

In addition, in the present invention, after the pulling of the seed crystal is stopped, there is no need to control the diameter of the single crystal, and there is no need to forcefully change the temperature of the melt. It is thought that there is no.

Embodiment FIG. 1 is a cross-sectional view schematically showing temporal changes in the growth situation of a single crystal for explaining an embodiment of the present invention.

An embodiment of the present invention will be described below using FIG.

500g of Ga metal and 570g of As metal as raw materials
g.

300 g of B203 as a sealant was placed in a boron nitride crucible with a diameter of 100 mm and heated. In this case, the composition of the raw material, expressed as Ga+-xAsx, is X=0.515 (the deviation with respect to the whole is 3 mol%). The raw materials were synthesized while keeping the temperature constant at 800°C, and then the temperature was raised to melt the raw materials. As shown in FIG. 1(a), the seed crystal 2 cut out from the GaAs single crystal held by the seed crystal holder 1 is placed on B2.
It adhered to the surface of the GaAs raw material melt 4 through the liquid sealant 3 of 0.03. As shown in FIG. 1(b), the temperature of the raw material melt 4 was controlled and the seed crystal 2 was pulled up while rotating to grow a single crystal 6. The pulling and rotation of the seed crystal 2 was stopped when the diameter of the grown single crystal reached approximately 70 mm as shown in FIG. 1(C). Thereafter, the temperature was slowly lowered, and the grown single crystal reached the inner wall of the crucible as shown in FIG. 1(d).

Furthermore, the temperature was gradually lowered to crystallize all the raw materials. Thereafter, the single crystal was slowly cooled to room temperature and the grown single crystal was taken out. As shown in FIG. 1(e), it was found that As metal precipitates 7 were present at the interface between the single crystal and the crystal. The obtained GaAs single crystal has a diameter of 94 mm and low distortion.
It was a high quality single crystal with no cracks. Moreover, it was easy to take out the single crystal from the rutsuho, and the rutsuho did not break.

Although the embodiments described above are for the case where a liquid sealant is used, the present invention can also be applied to the case of growing a single crystal that does not require a liquid sealant.

In the above-described embodiment, the single crystal was grown by fixing the rutsuho, but the present invention can also be applied to cases where the rutsuho is moved.

Also, the cross-sectional shape of the rutsuho does not necessarily have to be circular,
Depending on the desired cross-sectional shape of the single crystal, rectangular, square, or elliptical crucibles can be used.

(Effects of the Invention) According to the method for growing a single crystal of the present invention, when taking out a single crystal from a crucible, the single crystal can be easily taken out without breaking the single crystal or the crucible.

Furthermore, according to the method for growing a single crystal of the present invention, temperature changes during growth can be made gentler, and the occurrence of strain due to temperature changes can be controlled.

Furthermore, compared to the Czochralski method, it is easier to obtain a single crystal with a larger diameter from a crucible of the same diameter.

[Brief explanation of drawings]

FIGS. 1(a) to 1(e) are simplified sectional views showing the method of the present invention, and FIG. 2 is a sectional view showing the conventional method. Explanation of symbols 1 Seed crystal holder 2 Seed crystal 4 Raw material melt 5 Rukka 6 Grown single crystal 7 Precipitate (a) (b) (c) (d) (e) Precipitate Fig. 2 Fig. 1

Claims (1)

[Claims] 1. In a single crystal growth method in which a seed crystal is brought into contact with a raw material melt in a crucible and a crystal following the seed crystal is grown while pulling the seed crystal, the composition of the raw material melt is determined by the stoichiometric composition of the single crystal to be grown. The composition is shifted by 0.5 to 5 mol% from A method for growing single crystals characterized by the following.