JPS6126592A - Crystal growing device - Google Patents

Abstract

PURPOSE:To reduce absolute amounts of change in shape of supply substances, and to stabilize convection of melt, by dividing supply substances to a crystal growing device into plural parts, making the product of an electric current to be sent to them and time constant. CONSTITUTION:In growing crystal, the through hole of the bottom 2 of a crucible is filled with a rod of carbon or boron nitride having the same outer shape as that of the supply substances 5 instead of them, a material for melt is put in the crucibles 1 and 2, the temperature is raised, and the material is melted. The material is cooled once, the supply substances 5 are inserted into the hole instead of the carbon or boron nitride rod, the temperature is raised again, the substances are melted, the seed crystal 4' is immersed in the melt 3, and gradually pulled up while rotating it, to grow crystal largely. As the crystal is pulled up, a component having high segregation coefficient is exhausted, so an electric current is sent from the electric source 6 to a path of the supply substances 5, the melt 3, the first crucible 1 or the crystal 4 in order to supply the component, and the supply substances 5 are dissolved in the melt 3. In the operation, the product of an electric current sent to each of the plural supply substances 5 and time is made equal by changing the switch 11.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a pulling crystal growth apparatus equipped with means for replenishing a melt (or solution) with components that are easily depleted during crystal growth.

During crystal growth, components with large segregation coefficients in the melt are gradually depleted, causing compositional fluctuations in the growing crystal, resulting in a significant decrease in the utilization efficiency of the crystal.

For this purpose, various methods of replenishing the component substances have been attempted.

[Conventional technology]

FIG. 3 is a sectional view of a crystal growth apparatus equipped with a conventional component supply means.

The illustrated device is a device proposed by the present inventor, in which 1 is a cylindrical crucible side wall made of a conductive material such as carbon;
2 is a crucible bottom made of an insulating material such as boron nitride (PBN), 3 is a melt, 4 is a grown crystal, and 4' is a seed crystal.

A replenishment substance 5 containing the components to be replenished and having a higher melting point than the growth melt is brought into contact with the melt 3, and a current is passed between the replenishment substance 5 and the melt 3 to melt the components to be replenished. Let it dissolve in liquid 3.

For this purpose, a power source 6 is connected between the replenishment material 5 and the crucible side wall 1 or the seed crystal 4' via a changeover switch 7 and a current detection section 9.

The drive device 8 is driven by the current detection unit 9 via the feedback circuit 10, and the replenishment substance 5 is pushed out into the melt 3.

In the device described above, when the replenishment material 5 is a semiconductor crystal, local differences in electrical properties such as specific resistance cause local non-uniformity in the current flowing through the material, and as a result, the replenishment The melting of the substance 5 becomes uneven in places, and the part that comes in contact with the melt 3 has an asymmetrical uneven shape, which causes turbulence in the convection of the melt, causing the growing crystal to become gradually distorted, and the crystal to grow. This may cause problems such as the tendency for dislocations to occur.

[Problem that the invention seeks to solve]

Shape abnormalities due to local non-uniformity in the melting of the replenishing material adversely affect convection in the melt, making it difficult to obtain uniform crystals.

[Means for solving problems]

The solution to the above problem is to provide a mechanism that can move the replenishment substance containing the components to be replenished relative to the crucible, and a means for passing an electric current between the melt or solution held in the crucible and the replenishment substance. This is achieved by the crystal growth apparatus according to the present invention, which has a plurality of replenishment substances and has current switching means for making the product of the current and time flowing through each replenishment substance constant. .

[Effect]

The present invention is based on the fact that when a current is passed between the replenishment material and the melt, the amount of the replenishment material dissolved into the melt is proportional to the amount of electric charge, and that the smaller the size of the replenishment material, the better the characteristics within the replenishment material. Since the absolute amount of non-uniformity is small, the absolute amount of change in the shape of the replenishment material due to dissolution when electric current is applied will be small. By making the product of the current applied to this and the time constant, the absolute amount of change in shape of each replenishment substance is reduced, and the overall shape of the part of each replenishment substance that comes into contact with the melt remains relatively constant. This is to stabilize the convection of the melt.

FIG. 2 is a diagram illustrating the relationship between the dimensions of the replenishment material and the amount of deformation.

FIG. 2 (in aj, let d be the absolute amount of deformation when a single supplementary substance is used.

In FIG. 2 (bl), when the single replenishment substance is one-dimensionally divided into n pieces and the tips are aligned, the absolute amount of deformation is d/n.

〔Example〕

FIG. 1 is a cross-sectional view and a plan view of a crystal growth apparatus equipped with component replenishment means, showing an embodiment of the present invention.

This device is InAsNP I-XI Ga, lIn
1-XASI Suitable for pulling ternary compound semiconductor crystals such as GaAs, lp, -X, etc.

In the crucible, the crucible has a cylindrical side wall 1 made of a conductive material such as carbon, and an insulating material such as PBN, and has seven through holes arranged symmetrically with respect to the axis of rotation of the crystal in the center. It is constructed by stacking the bottom part 2 with the bottom part 2 on top of the other.

Seven replenishment substances 5 are inserted so as to fit into each through hole, and these are pushed out into the melt 3 by a drive device 8 as a whole, and are connected to a power source 6 through a changeover switch 11, respectively. It has become.

Replenishment substance 5 is InP in the case of InAsxP+-x.

Ga, In+4. For ΔS, GaAs, , GaASx
In the case of P+-x, GaP is preferably used.

For growth, first plug the through hole in the bottom 2 of the crucible with a rod of carbon or PBN of the same external shape instead of the replenishment material 5, weigh the melt materials into the crucibles 1 and 2, and raise the temperature. melt.

Once cooled, a replenishing material 5 made of InP, GqAs, or GaP is added instead of the carbon or PBH rod.
．． Insert the seed crystal 4' and raise the temperature again to melt it.
is immersed in the melt 3 and gradually pulled up while rotating to grow the crystal 4 to a large size.

In this case, the replenishment substance 5 used has a melting point higher than that of the melt, so it will not melt at this point.

As the crystal is pulled up, components with large segregation coefficients in the melt, for example, P when melt 3 is InAsxP+-x,
< GaJr++-xAs, Ga, GaAs
, P, -, since P will be depleted, the supply material 5, melt 3, and first crucible l will be supplied from the power source 6 to compensate for this.
Alternatively, an electric current is passed through the path of the crystal 4 so that the replenishment substance 5 is dissolved into the melt 3. At this time, the changeover switch 11 is used to make the product of the current flowing through each of the plurality of replenishment substances 5 equal to the time.

If a constant current source is used for the voltage tA6, the switch may be changed over at regular intervals. The shorter the switching time, the smaller the temporal variation in the amount of elution between the replenishment substances 5.

If the replenishment material 5 is pushed out by the driving device 8 by the amount of melt released, and the tip is always placed at the bottom of the crucible, the shape of the melt 3 will not change, so the flow in the melt will be constant and turbulent. will not occur.

In the conventional example in which a single replenishment material was used, if there were severe unevenness in the replenishment material, it would not only cause turbulence in the melt but also cause the melt to leak from the bottom of the crucible. This does not occur and stable crystal growth can be achieved.

In the example, seven wooden round rod-shaped replenishment substances were used, but the greater the number, the greater the effect.

Further, in the embodiment, the replenishment substance 5 was brought into contact with the melt from the bottom 2 of the crucible, but it may be brought into contact from the surface of the melt.

Furthermore, although the embodiments have been applied to growth from a melt, the present invention can also be applied to growth from a solution.

〔Effect of the invention〕

As described in detail above, according to the present invention, components that are easily depleted in the melt can be replenished without disturbing the convection of the melt, so that uniform and high-quality crystals can be obtained.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view and a plan view of a crystal growth apparatus equipped with component replenishment means showing an embodiment of the present invention, and FIGS. 2(a) and (
b) is a diagram illustrating the relationship between the dimensions of the replenishing material and the amount of deformation, and FIG. 3 is a sectional view of a crystal growth apparatus equipped with a conventional component replenishing means. In the figure, 1 is the crucible side wall, 2 is the crucible bottom, 3 is the melt,
4 is a grown crystal, 4' is a seed crystal, 5 is a supply substance, 6 is a power source, 7.11 is a changeover switch, 8 is a drive device, 9 is a current detection section, and 10 is a feedback circuit. Chi 1 A Fu 2 Ka (phantom (b)

Claims (2)

[Claims] (1) A crystal that is equipped with a mechanism that can move a replenishment substance containing the components to be replenished relative to a crucible, and a means for passing an electric current between the melt or solution held in the crucible and the replenishment substance. 1. A crystal growth apparatus comprising a plurality of replenishment substances and current switching means for making the product of current and time passed through each replenishment substance constant. (2) Claim 1, characterized in that a plurality of replenishing substances are arranged at symmetrical positions with respect to the rotation axis of the crystal.
The crystal growth apparatus described in Section 1.