JPS61174189A - Method and device for production of single crystal - Google Patents

Abstract

PURPOSE:To maintain the specified impurity concn. of a raw material melt with a simple device in the stage of growing a single crystal of a compd. added with an impurity having <1 coefft. of segregation or ternary compd. by changing the heating position of the raw material packed in a crucible. CONSTITUTION:For example, a raw material which is not added with the impurity is packed into the crucible 1 and is heated to melt by heaters 6, 7. The output of the auxiliary heater 7 is then regulated to solidify the raw material melt form the lower part. The upper part of the raw material melt is held in the state of the melt. A crucible 2 having the outside diameter approximate to the inside diameter of the crucible 1 and having a fine hole in the bottom is thereupon sunk into the melt, then the crucible settles on the solid raw material. The impurity is preliminarily added to the raw material prior to starting of the growth of the single crystal and thereafter the growth is started. The output of the heater 7 is regulated to melt the upper part of the raw material solid 3 by as much as the amt. approximately equal to the amt. of the grown single crystal or T(coefft. of segregation) X weight of the crystal in order to compensate the impurity concn. in the raw material melt 4 increasing with the growth of the single crystal.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method and apparatus for producing a single crystal, and in detail, B.
1. , sIO, , LIMbOl, B amount, Gams,
Gap.

Oxide single crystals grown by a pulling method such as nP or semiconductor impurities include uniform addition of impurities with a segregation coefficient of less than 1, or n1-4s.

Ga1-! The present invention relates to a manufacturing method and apparatus for making the composition of a ternary compound semiconductor single crystal, such as Musiem 8, uniform.

[Conventional technology]

When growing a single crystal from a raw material melt containing impurities,
When the segregation coefficient of impurities is smaller than 1 as the single crystal grows, the impurity concentration in the raw material melt increases, making it difficult to obtain a single crystal with a uniform impurity concentration. The same can be said of the third component in the ternary compound single crystal.

Conventional techniques for solving these problems include:
A method of uniformly adding impurities to a single crystal grown by a pulling method has been proposed, for example, by W, G, Pfann.
Author, “Zone Meltlng J (1978) p.
, 204-p., 206, a floating crucible with pores at the bottom is placed in the melt of one raw material, impurities are added inside the floating crucible, and additive-free material is placed outside the floating crucible. A method is to keep the concentration of the melt in the floating crucible constant by filling the raw material melt and diluting the melt in the floating crucible, where the impurity concentration increases as the crystals grow, with the external additive-free melt through the pores. be.

Alternatively, in order to keep the impurity concentration, which increases with growth, constant, there is also a method of adding an appropriate amount of a raw material melt without additives from the outside.

[Problem that the invention seeks to solve]

However, in the former method using a floating crucible described above, it is very difficult to set the pore diameter and the shape of the floating crucible, and if the addition time is too early, the melt inside and outside the floating crucible will become equalized by diffusion. It has the disadvantage that it is difficult to determine when to add impurities because it is stored away.

The latter method of adding raw material melt from the outside and diluting it is
The addition method is difficult, the furnace configuration becomes complicated, and there are problems in that the heat distribution within the furnace is disturbed.

The purpose of the present invention is to overcome these drawbacks and to provide a simple device that
An object of the present invention is to provide a method and an apparatus that can maintain a constant impurity concentration in a raw material melt and produce stable single crystals.

[Means for solving problems]

In the present invention, when growing a single crystal containing an impurity with a segregation coefficient of less than 1 or a ternary compound single crystal containing a third component with a segregation coefficient of less than 1, only the upper part of the raw material filled in a crucible is grown. The increase in the concentration of impurities or the third component in the molten raw material due to crystal growth is compensated for by heating the lower solid raw material part in the crucible, and the concentration of impurities or the third component in the raw material melt is reduced. This is a method for producing a single crystal, which is characterized by growing a single crystal while maintaining constant growth. Furthermore, the present invention provides a crucible, a movable crucible fitted into the crucible and having a pore in the lower part, a means for heating the upper part of the crucible, a means for heating the lower part of the crucible, and a method for growing raw materials from the raw material in the crucible. A single crystal manufacturing apparatus and a melt having means for pulling a single crystal
-f1: an auxiliary crucible communicating with the lower part of the crucible through a pore, means for heating the crucible, means for heating the auxiliary crucible, and means for pulling up the single crystal grown from the crucible and the raw material in the auxiliary crucible This invention relates to a single crystal manufacturing device.

In other words, in the method of the present invention, only the raw material in the upper part of the crucible for growing a single crystal is melted, and after adding impurities, the single crystal growth is started with the raw material coexisting with solid and liquid, and the impurities are removed as the crystal grows. The impurity concentration of the raw material melt is kept constant by melting a solid raw material that does not contain or has a low concentration.

The method of the present invention will be explained in detail below with reference to the drawings. 1st
The figure is a diagram explaining an embodiment of the present invention, and in the figure, 1 is a crucible made of PBX or carbon, platinum, etc., 2 is a movable crucible made of BN, AtN, etc. with holes in the bottom, and 3 is a crucible with no or low impurity addition. Concentrated raw material solid, 4 impurity-added raw material melt, 5 single crystal, 6 main heater, 7 auxiliary heater, 8 upper shaft, 9 chamber, 10 lower shaft, 11 load cell, 1
2 is an inert liquid (sealant).

To grow a single crystal, a crucible 1 is filled with raw materials without any impurities and heated by heaters 6 and 7.

melt. Next, the output of the auxiliary heater 7 is adjusted to solidify the raw material melt starting from the lower part. At this time, the upper part of the raw material melt is kept in a melt state. In this state, when the movable crucible 2, which has an outer diameter close to the inner diameter of the crucible 1, is submerged in the melt, it comes to rest on top of the solid raw material.

The weight of the movable crucible 2 is adjusted using a weight or the like so that it sinks into the melt. Before starting single crystal growth, impurities are added and growth begins.

However, impurities may be added in advance before melting the raw materials. This is because the segregation coefficient is smaller than 1, so the amount of impurities that segregate into the raw material at the bottom of the crucible that is first solidified is smaller than that in the melt, which sufficiently compensates for the impurity concentration in the melt that increases with crystal growth. can do.

In order to compensate for the increase in impurity concentration in the raw material melt 4 as the single crystal grows, the output of the auxiliary heater 7 is adjusted so that the amount of impurities is approximately the same as that of the grown single crystal, or (T - segregation coefficient) x crystal weight. Melt the upper part of raw material solid 3 by the amount of . The melting amount of the raw material solid 5 can be estimated from the position of the movable crucible 2 or the position of the melt surface determined from the density difference between the raw material solid 3 and the liquid.

Further, the movable crucible 2 may be fixed, and in that case, the amount of melted raw material solid 3 can be determined from the position of the melt surface.

FIG. 2 shows an embodiment in which the movable crucible 2 is fixed. A portion of the bottom of the crucible communicates with an auxiliary crucible 13 provided at the bottom of the crucible 1. The auxiliary crucible 1'5 is heated by the auxiliary heater 7 to adjust the amount of melted raw material solid.

[Effect]

The principle of keeping the impurity concentration of the raw material melt constant during crystal growth using a conventional floating crucible is to use the diffusion of impurities or additive-free raw material melt through the pores provided at the bottom of the floating crucible. However, it is extremely difficult to control the diffusion rate, and there is a large limit on the time from the time the impurity is added until the end of single crystal growth.If it is too early, sufficient diffusion will not occur, and on the other hand, it takes too long. The entire melt (inside and outside of the floating crucible) becomes uniform.

As in the present invention, if the additive-free raw material outside the movable crucible is kept in a solid state and only the required amount is melted, there is no time limit as described above, and if the pore size at the bottom of the crucible is made large, melting can be achieved. It is possible to mix it with the melt in the floating crucible almost simultaneously and make it uniform.

In addition, according to this method, the raw material solid in an amount approximately equal to the single crystal growth weight is melted and flows into the movable crucible, so the depth of the raw material melt can always be kept constant, and the effect of convection can be controlled under certain conditions. This makes it possible to grow single crystals.

〔Example〕

Using the configuration shown in Figure 1, G with In added as an impurity
An aAs single crystal was grown.

The crucible 1 was filled with about 5 ml of GaAs raw material and B, 03 liquid sealant 2001, and heated to about 125 yen by heater 6.7.
After heating to 0°C to melt the entire body, cool it to form solid B, 03
A movable crucible 2 made of BN and equipped with a Mo weight was placed on top and heated again by the heater 6.7. At this time, heater 6.
7 and melted only the upper half of the raw material while observing the position of the movable crucible 2. Next, after adding about 20 In, the rotation speed of the upper shaft 8 and lower shaft 10 is 1 to 10 rpm.
Start growing at a lifting speed of 5 to 10 cm/h, calculate the lifting weight from the signal of the load cell 11 attached to the upper shaft 8, and move the raw material solid 3 in an amount corresponding to the weight to the position of the movable crucible 2. While observing this, the crystal growth was continued while melting by adjusting the output of the auxiliary heater.

The grown single crystal weighs 1.5 kg and is approximately 100 mm long.
-, the In concentration was about 1.5 WJ, and the variation in the In# degree within the crystal was within 20%. Further, no precipitation of In was observed inside the crystal, and the EPD from the shoulder to the rear end of the crystal was 100 to 500/m'' or less, and the electrical insulation was good.

The above examples are GaA with In added as an impurity.
s Although the case of growing a single crystal is shown, the example of growing a mixed crystal single crystal is also the same as the above example, and can also be applied to growing a mixed crystal single crystal.

〔Effect of the invention〕

As explained above, in order to keep the composition or impurity concentration of the raw material melt constant, the raw material to be supplied is kept in a solid state, and only the necessary amount is heated and melted and supplied, thereby controlling the composition of the raw material melt with high precision. b makes it possible to keep the impurity concentration constant, making it possible to make the composition or impurity concentration in the grown single crystal uniform.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams illustrating embodiments of the method of the present invention, where Figure 1 shows a case where a movable crucible is provided within the crucible, and Figure 2 shows a case where an auxiliary crucible is provided below the crucible. shows.

Claims (3)

[Claims] (1) When growing a single crystal containing an impurity with a segregation coefficient of less than 1 or a ternary compound single crystal containing a third component with a segregation coefficient of less than 1, only the upper part of the raw material filled in the crucible is grown. The increase in the concentration of impurities or the third component in the molten raw material due to crystal growth is compensated for by heating the lower solid raw material part in the crucible, and the concentration of impurities or the third component in the raw material melt is kept constant. A method for producing a single crystal, which is characterized by growing a single crystal while maintaining a constant temperature. (2) A crucible, a movable crucible fitted into the crucible and having a pore at the bottom, a means for heating the upper part of the crucible, a means for heating the lower part of the crucible, and a unit grown from the raw material in the crucible. A single crystal production device comprising means for pulling a crystal. (3) a crucible, an auxiliary crucible communicating with the lower part of the crucible through a pore, a means for heating the crucible, a means for heating the auxiliary crucible, and a means for pulling the single crystal grown from the raw materials in the crucible and the auxiliary crucible. A single crystal production device comprising: