JP2830290B2 - Single crystal growing method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a semiconductor such as Si, Ge, GaAs, I, or the like by a vertical Bridgman method or a vertical gradient freezing method.
The present invention relates to a method and an apparatus for growing a group III-V compound semiconductor such as nP, a group II-VI compound semiconductor such as CdTe and ZnSe, and an oxide such as BSO and LBO.

(Prior Art) Conventionally, the above-mentioned single crystal is grown by a vertical Bridgman method, a vertical gradient freezing method, a pulling method or the like. In the vertical Bridgman method, a raw material melt is accommodated in a vertical container, the container is placed in a temperature gradient furnace, and the container is moved downward, whereby the raw material solution is cooled and solidified from below, thereby forming a single crystal. It is a method of nurturing. The vertical gradient freezing method is a method in which a vertical container is fixed, the output of a heater is adjusted, the temperature distribution is moved, and the raw material melt is cooled and solidified from below to grow a single crystal. In the method of growing a single crystal using these vertical containers, a single crystal can be obtained along the side wall of the container, so that a columnar single crystal can be easily grown. In addition, since the heater is arranged from the periphery by a heater arranged near the vertical container, the temperature control of the raw material melt becomes easy, and the ambient temperature of the raw material melt can be kept high, so that crystallization from below can be achieved. The solid-liquid interface on the upper surface of the single crystal to be formed can be easily maintained in a convex shape, and the incorporation of crystal defects can be avoided.

However, in these methods, in growing an impurity-containing single crystal, the impurity concentration in the single crystal increases or decreases from below to above due to the segregation phenomenon of the impurity, and the single crystal having a uniform impurity concentration is obtained. Could not get.

On the other hand, the pulling method is a method of pulling a single crystal from a raw material melt in a crucible by an upper shaft, and is suitable for growing a large single crystal. The pulling method described in Japanese Patent Application Laid-Open No. 61-26129 attempts to always keep the impurity concentration of the raw material melt of the inner crucible constant by using a double crucible and to keep the impurity concentration of the crystal constant. is there.

(Problems to be Solved by the Invention) However, in the above-mentioned double crucible method, it is difficult to control the shape of the pulled crystal and the shape of the solid-liquid interface, which are common drawbacks of the pulling method. The raw material melt of the inner crucible is heated by the raw material melt, and the raw material melt of the inner crucible is convected. Therefore, the impurity concentration varies in the radial direction, and it is difficult to grow a single crystal having a uniform impurity concentration. Was.

The present invention solves the above-mentioned disadvantages, and utilizes the advantages of the double crucible method to the vertical Bridgman method and the vertical gradient freezing method to easily grow a single crystal having a uniform impurity concentration and a method therefor. It is intended to provide a device.

(Means for Solving the Problems) The configuration of the present invention is as follows.

(1) In a method of growing a single crystal by cooling and solidifying a raw material melt contained in a vertical container from the bottom, a horizontal baffle is formed on the raw material melt while leaving a gap L of 5 mm or less between the raw material melt and the inner wall of the container. soaked with the outer periphery of the baffle and attached to the cylindrical portion of the height L ₂ extending upward, at that time, the cylindrical portion height L _2,
The gap L is set so as to maintain the relationship of L ₂ ≧ 3 × L, and the distance L ₁ between the solid-liquid interface and the lower surface of the baffle is set.
There holds a certain distance in a range that satisfies L ₁ ≦ D _1/2, with the diameter D ₁ of the single crystal, and as the raw material melt from the gap does not flow back, gradually the baffle A method for growing a single crystal, characterized by raising.

(2) The method for growing a single crystal according to (1), wherein one or more communication holes having a diameter of 6 mm or less are provided in the baffle.

(3) In a method for growing a single crystal by cooling and solidifying a raw material solution contained in a vertical container from the bottom, a horizontal baffle is immersed in the raw material melt while leaving a gap between the inner wall of the container and the baffle. The baffle is provided with one or more communication holes having a diameter of 6 mm or less, and a cylindrical portion extending upward is provided on the outer periphery of the baffle so that the upper end of the cylindrical portion always comes above the raw material melt, and the solid-liquid interface And the distance L ₁ between the lower surface of the baffle and the single crystal is maintained at a constant distance within a range satisfying L ₁ ≦ D _1/2 between the diameter D ₁ and the raw material melt does not flow backward from the gap. A method for growing a single crystal, comprising: gradually raising the baffle.

(4) In a single crystal growing apparatus provided with a vertical container for accommodating the raw material melt and a means for melting the raw material and cooling and solidifying the raw material from the bottom thereof, a gap l of 5 mm or less is provided between the container and the inner wall of the container. using the horizontal baffle left, on the outer periphery of the baffle and attached to the cylindrical portion of the height L ₂ extending upwardly, the cylindrical portion of the height L _2, L ₂ ≧ 3 × l between the gap l And a drive shaft for raising and lowering the baffle is provided, and a distance L ₁ between the solid-liquid interface and the lower surface of the baffle is set.
Gradually increases but maintains a certain distance in a range that satisfies L ₁ ≦ D _1/2, with the diameter D ₁ of the single crystal, and the raw material melt from the gap to the baffle so as not to flow back An apparatus for growing a single crystal, comprising: means for controlling the drive shaft to be driven.

(5) The apparatus for growing a single crystal according to (4), wherein one or more communication holes having a diameter of 6 mm or less are provided in the baffle.

(6) In a single crystal growing apparatus provided with a vertical container for accommodating a raw material melt and a means for melting the raw material and cooling and solidifying from the bottom thereof, a horizontal space having a gap between the inner wall of the container and the single crystal growing apparatus is provided. Using a baffle, the baffle is provided with one or more communication holes having a diameter of 6 mm or less, and a cylindrical portion extending upward is provided on the outer periphery of the baffle, and the upper end of the cylindrical portion is always higher than the raw material melt. It has is to attaching a drive shaft for raising and lowering the baffle, and, L ₁ between the distance L ₁ between the solid-liquid interface and the lower surface of the baffle between the diameter D ₁ of the single crystal ≦ D ₁ / 2, a single crystal characterized by comprising a drive shaft control means for gradually raising the baffle so that the raw material melt does not flow backward from the gap while maintaining a certain distance within a range satisfying Breeding equipment.

(Operation) FIG. 1 is a conceptual diagram showing a cross section of a vertical Bridgman device as one specific example of the present invention. A crucible 5 is arranged in a susceptor 6 supported on the lower shaft, a seed crystal 4 is placed on the bottom of the crucible, and a horizontal baffle plate 1 which is a feature of the present invention is immersed in the raw material melt 2. A drive shaft 14 is provided for raising and lowering the baffle plate. The baffle plate can be provided with a cylindrical portion 12 on its outer periphery in an upward direction. Around the vertical container, heaters 7, 8 and 9 for forming a temperature gradient are arranged. These devices are located in the outer container 10. Although not shown in this figure, when growing a III-V group compound semiconductor such as GaAs or InP, or a II-VI group compound semiconductor such as ZnSe or CdTe, the raw material melt is mixed with B ₂ O ₃ It is also possible to seal with a liquid sealant such as.

The single crystal is grown by placing the raw material in a crucible, forming a temperature gradient as shown in FIG. 2 by the heater, and gradually lowering the vertical container to convert the single crystal 3 into a single crystal.
Nurture. The solid-liquid interface 13 of the single crystal is at the melting point of the raw material melt 2.

When various experiments were performed using such a device, the following relationship was found. That is, the distance between the solid-liquid interface 13 and the lower surface of the baffle plate 1 is L _1, and the diameter of the single crystal 1 is D ₁
When the, by holding a certain distance L ₁ in the range of L ₁ ≦ D _1/2 to raise the baffle plate, to limit the raw material melt volume between the baffle plate and the solid-liquid interface In addition, the non-uniformity of the impurity concentration in the raw material melt can be suppressed, and a single crystal having a uniform impurity concentration can be grown at a high yield. When the height of the cylindrical portion attached to the outer periphery of the baffle plate 1 is L ₂ and the distance of the gap 12 between the baffle plate 1 and the inner surface of the crucible 5 is l, the gap l is 5 mm or less, ₂ ≧ 3
By setting it to l, it is preferable to prevent backflow of the raw material melt. Incidentally, when by increasing the height L ₂ of the cylindrical portion of the baffle plate always to exit above the surface of the raw material melt is to substantially prevent backflow of the raw material melt even a little wider gap l Can be.

The apparatus shown in FIG. 4 is the same as the apparatus shown in FIG. 1 except that a communication hole 11 is provided in the horizontal baffle plate. When a single crystal is grown using this apparatus, the raw material melt 2 can be supplied between the horizontal baffle plate 1 and the surface of the grown crystal 3 through the communication hole 11 of the horizontal baffle plate 1. Therefore, the apparatus is suitable for replenishing a relatively large amount of raw material melt. The diameter D ₂ of the communicating holes, it is desirable to 6mm or less.

Although the vertical Bridgman apparatus has been described above, the above-described baffle plate can be similarly applied to a vertical gradient freezing apparatus, and the same effect can be obtained.

Example A GaAs single crystal was grown using the vertical Bridgman apparatus shown in FIG. A PBN crucible with an inner diameter of 50 mm is placed in a carbon susceptor, and a 10 mm thick, 46 mm diameter PBN coated carbon baffle plate is used.
The one provided with a cylindrical portion of 20 mm was used.

In the crucible, 1.5 kg of GaAs polycrystal and ₂ parts of liquid sealant B ₂ O ₃
20 g of In and 15 g of In were charged, and 20 atm of Ar gas was sealed in an external container. Then, electricity is supplied to the heater to melt the raw material.Then, the temperature gradient near the solid-liquid interface is maintained at 20 ° C./cm, and the distance between the solid-liquid interface and the lower surface of the baffle plate is maintained at 10 to 15 mm to form a single crystal. Nurtured.

The In concentration of the obtained GaAs single crystal could be made very uniform as shown in FIG.

For comparison, a GaAs single crystal was grown under the same conditions as above except that the baffle plate was omitted. The obtained GaAs single crystal is the third
A large concentration gradient was shown as shown in the figure.

(Effect of the Invention) In the present invention, by adopting the above configuration, the shape control of the solid-liquid interface becomes easy, and the impurity concentration of the raw material melt between the baffle plate and the upper surface of the grown crystal is made uniform. As a result, it was possible to easily grow a columnar single crystal having few crystal defects and uniform impurity concentration.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a cross section of a single crystal growing apparatus as one specific row of the present invention, FIG. 2 is a graph showing an example of an axial temperature distribution of the apparatus shown in FIG. FIG. 4 is a graph showing the In concentration distribution in the axial direction of the single crystals obtained in Examples and Comparative Examples. FIG. 4 is a cross-sectional view of a single crystal growing apparatus provided with a communication hole in a baffle plate of the apparatus in FIG. FIG.

Claims (6)

(57) [Claims] 1. A method for growing a single crystal by cooling and solidifying a raw material melt accommodated in a vertical container from the bottom thereof, wherein a horizontal baffle is formed by leaving a gap l of 5 mm or less between the raw material melt and the inner wall of the container. immersed in the liquid, the outer periphery of the baffle and attached to the cylindrical portion of the height L ₂ extending upwardly, in which the cylindrical section height L ₂
Is set so as to maintain the relationship of L ₂ ≧ 3 × 1 with the gap l, and the distance L ₁ between the solid-liquid interface and the lower surface of the baffle is set between the diameter D _{1 of the} single crystal. L ₁ ≦ D _1/2 , a constant distance within a range satisfying, and, so that the raw material melt does not flow backward from the gap, gradually raise the baffle, characterized in that the single crystal Training method. 2. A communication hole having a diameter of 6 mm or less is provided in said baffle.
The method for growing a single crystal according to claim 1, wherein at least one is provided. 3. A method for growing a single crystal by cooling and solidifying a raw material melt contained in a vertical container from the bottom portion, wherein a horizontal baffle is immersed in the raw material melt while leaving a gap between the container inner wall. The baffle is provided with one or more communication holes with a diameter of 6 mm or less, a cylindrical portion extending upward is provided on the outer periphery of the baffle, and the upper end of the cylindrical portion is always above the raw material melt, and The distance L ₁ between the solid-liquid interface and the lower surface of the baffle maintains a certain distance within a range that satisfies L ₁ ≦ D _1/2 between the diameter D _{1 of the} single crystal and the raw material from the gap. A method for growing a single crystal, characterized by gradually raising the baffle so that the melt does not flow backward. 4. A single crystal growing apparatus having a vertical container for accommodating a raw material melt and a means for melting the raw material and cooling and solidifying the raw material from the bottom thereof, wherein a 5 mm or less space is formed between the vertical wall and the inner wall of the container. using the horizontal baffle to leave a gap l, the outer periphery of the baffle and attached to the cylindrical portion of the height L ₂ extending upwardly, the cylindrical portion of the height L _2, L ₂ ≧ 3 between the gap l Xl relationship is maintained, a drive shaft for raising and lowering the baffle is provided, and the distance between the solid-liquid interface and the lower surface of the baffle is set.
L ₁ is held a certain distance in a range satisfying, L ₁ ≦ D _1/2 between the diameter D ₁ of the single crystal, and gradually the baffle as the raw material melt from the gap does not flow back An apparatus for growing a single crystal, comprising control means for controlling the drive shaft to be raised. 5. A communication hole having a diameter of 6 mm or less is provided in said baffle.
The single crystal growing apparatus according to claim 4, wherein at least one is provided. 6. A single crystal growing apparatus comprising a vertical container for accommodating a raw material melt and means for melting the raw material and cooling and solidifying the raw material from the bottom thereof, wherein a gap is left between the container inner wall. Using a horizontal baffle, one or more communication holes having a diameter of 6 mm or less are provided in the baffle, and a cylindrical portion extending upward is provided on the outer periphery of the baffle, and the upper end of the cylindrical portion is always above the raw material melt. A drive shaft for raising and lowering the baffle, and a distance L ₁ between the solid-liquid interface and the lower surface of the baffle is L ₁ ≦ D between the diameter D _{1 of the} single crystal. _1/2,
A single crystal growing apparatus, comprising: a drive shaft control unit that keeps a certain distance within a range satisfying the condition, and gradually raises the baffle so that the raw material melt does not flow backward from the gap. .