JP2543449B2 - Crystal growth method and apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crucible supporting structure in a crystal growing method and a crystal growing apparatus, and relates to CdTe.
And a technique suitable for growing a II-VI group compound semiconductor crystal as described above.

[0002]

2. Description of the Related Art Conventionally, GaA is one of the compound semiconductor single crystals.
s and InP single crystals are manufactured by the LEC method (liquid sealed Czochralski method). On the other hand, CdTe
Since such II-VI compound semiconductor single crystals are difficult to grow by the LEC method, they are grown by the horizontal boat method or the vertical annealing method.

Of these, the growth of CdTe single crystals by the vertical slow cooling method has generally been carried out by an apparatus as shown in FIG. 2 (a).

That is, a seed crystal 2 and a raw material (polycrystal) are put in a crucible 1 having a funnel shape at the bottom, supported by a susceptor 3 made of BN (boron nitride), and enclosed in a quartz ampoule 4. Then, this is installed in a furnace having a cylindrical heater 5, and power is supplied to the heater 5 to form a temperature gradient (see FIG. 2 (b)) such that a portion above the seed crystal 2 has a melting point or higher. The temperature is gradually lowered while maintaining this gradient to grow crystals.

Unlike the seeding of the LEC method, the seeding of the above method is structurally difficult to perform while directly observing the state at the time of seeding, and the BN susceptor 3 has a high thermal conductivity. It was difficult to form a temperature gradient on the crystal, and it was difficult to realize the seeding position with good reproducibility.

As a device for performing the above seeding with good reproducibility, in the vertical Bridgman method, a window for observing the tip of the ampoule is provided in the lower part of the growth furnace, and the temperature of the ampoule tip is measured by a non-contact thermometer (infrared thermometer). , A method of growth in which the state of phase transformation at the tip of an ampoule is observed and seeding can be performed with good reproducibility is disclosed (Electronic Materials Research Institute Vol. 4, No. 2 (1986) 14). This method has the advantage that the seeding position can be confirmed indirectly because the position when the upper part of the seed crystal melts corresponds to the temperature indication of the infrared thermometer, but it has the disadvantage that the growing device becomes large. It was

[0007]

DISCLOSURE OF THE INVENTION The present invention eliminates the above-mentioned drawbacks, and an object of the present invention is to observe a seed crystal melting position by improving a crucible supporting structure in crystal growth by a vertical annealing method. Without increasing the reproducibility of the seeding position and improving the production yield of the single crystal.

[0008]

[Means for Solving the Problems]

According to the present invention, in a method of growing a single crystal from a seed crystal by melting a raw material in a crucible and then gradually lowering the temperature, the temperature gradient in the vertical direction of the seed crystal lower part is set to the vertical direction of the seed crystal upper part. The present invention provides a crystal growth method characterized by making the temperature gradient larger than the above temperature gradient.

Further, the present invention comprises a cylindrical heating element and a supporting element which is arranged inside the heating element and which supports a crucible containing a raw material. The heating element forms a desired temperature gradient. In the apparatus for growing a single crystal from a seed crystal by gradually melting the raw material in the crucible and then gradually lowering the temperature, the material around the seed crystal of the support may be changed into upper and lower parts.
The present invention provides a crystal growth apparatus characterized in that the upper half is made of a material having a high thermal conductivity and the lower half is made of a material having a low thermal conductivity.

[0010]

According to the above means, since the temperature gradient in the vertical direction of the seed crystal becomes large in the portion surrounded by the lower support, even if the temperature distribution around the support slightly fluctuates, the conventional support can be The variation in the position for seeding is reduced and the reproducibility of the seeding position is improved as compared with the time of use.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of a susceptor which is a main part of a crystal growth apparatus according to the present invention. In this embodiment, the upper susceptor 14 around the seed crystal portion is made of a material having a high thermal conductivity such as high-purity carbon, and the lower susceptor 15 is made of a material having a low thermal conductivity such as quartz. There is.

In FIG. 1, 13 is a heater as a heating element, 16 is a heat-resistant brick on which the quartz ampoule 12 is placed, and the heating element 13 is similar to the conventional apparatus shown in FIG. 11 and the susceptor are formed in a cylindrical shape so as to surround the outside thereof, and are configured so that a predetermined temperature gradient can be formed.

In the above embodiment, carbon is used as the material having high thermal conductivity, but boron nitride or the like may be used instead of carbon. In addition to quartz, alumina or the like may be used as the material having a low thermal conductivity.

As an example, a preliminary experiment for growing a CdTe single crystal was conducted using the apparatus shown in FIG. A high-purity carbon member having an outer diameter of 82 mm and a thickness of 40 mm is used as the upper susceptor 14 made of a material having a high thermal conductivity, and the lower susceptor 15 made of a material having a low thermal conductivity is also an outer diameter of 82 mm and a thickness. A quartz member having a thickness of 40 mm was used. As the crucible 11, a crucible made of pBN having an inclination angle of 45 degrees was used. In order to measure the temperature distribution in the small diameter part of the crucible 11 in which the seed crystal is placed, P is placed in a quartz protective tube on the center axis of the crucible and on the outer wall of the small diameter part.
An R thermocouple was installed so that it could slide up and down, and 1500 g of CdTe polycrystal was placed in the crucible as a raw material. These were placed in a quartz ampoule 12, vacuum-sealed, and then placed inside a heater 13. Then, power is supplied to the heater 13 so that the temperature inside the crucible once becomes 1092.
After controlling the temperature so that the temperature becomes ℃ or more and melting all the CdTe polycrystals, the upper susceptor 14 and the lower susceptor 1
Heater 13 so that the vicinity of the contact surface with 5 is 1092 ° C
The temperature was controlled and the temperature distribution of the seed crystal part was measured. FIG. 3 shows the furnace wall temperature distribution (b) during measurement and the temperature measurement result (a) of the seed crystal part. It was confirmed that the lower half of the seed crystal part had a steep temperature gradient due to the influence of the quartz susceptor. For comparison, the temperature measurement results when the upper susceptor and the lower susceptor are both carbon and quartz are shown in FIG.
Shown in (a) and (b). Conventionally, crystal growth was performed in the state as shown in FIG. 4 (a), but in this case, the temperature of the seed crystal portion slightly changes each time the setting changes, even if the temperature distribution on the furnace wall remains the same. However, since the inside cannot be seen from the outside, the seeding position may change greatly, and in extreme cases, the seed crystal may melt, which is one of the factors that reduce the manufacturing yield. Was becoming. Further, in the case of FIG. 4 (b), since the thermal conductivity of quartz is low, the rate of heat escaping during single crystal growth is reduced, and even if seeding is performed with good reproducibility, the growth rate must be slowed. As a result, the production efficiency was lowered.

According to the present invention, as a result of seeding, the position of seeding is hardly displaced, and the manufacturing yield is improved.

[0016]

As described above, according to the present invention, in the apparatus for growing a single crystal by the vertical annealing method, the peripheral portion of the seed crystal of the support for supporting the crucible is divided into upper and lower parts, and the upper half has high thermal conductivity. The material, the lower half of which is made of a material with low thermal conductivity, makes the temperature gradient in the lower part of the seed crystal steep, and the seeding position hardly changes even if the ambient temperature environment changes slightly. Since it can be realized, there is an advantage that the manufacturing yield is improved.

[Brief description of drawings]

FIG. 1 is a sectional front view showing an embodiment of a main part of a crystal growth apparatus according to the present invention.

2 (a) and (b) are a cross-sectional view showing an example of a conventional single crystal growth apparatus by a vertical annealing method and an explanatory view showing its temperature distribution.

3 (a) and 3 (b) are explanatory views showing a seed crystal temperature distribution at the time of seeding by the device of the present invention and a furnace wall temperature distribution thereof.

4A and 4B are explanatory views showing a comparative example with respect to FIG.

Claims (3)

(57) [Claims] 1. A method for growing a single crystal from a seed crystal by melting a raw material in a crucible and then gradually lowering the temperature, wherein a temperature gradient in the vertical direction of the lower portion of the seed crystal is set to a temperature in the vertical direction of the upper portion of the seed crystal. A method for growing a crystal characterized by making it larger than a gradient. 2. A cylindrical heating body, and a supporting body disposed inside the heating body and supporting a crucible containing raw materials, wherein the heating body forms a desired temperature gradient, and the inside of the crucible is formed. In a device for growing a single crystal from a seed crystal by gradually melting the raw material and then gradually lowering the temperature, the material around the seed crystal of the support is divided into upper and lower parts, and the upper half is a material having high thermal conductivity, A crystal growth apparatus characterized in that the lower half is made of a material having a low thermal conductivity. 3. A crystal growth apparatus, wherein the material having high thermal conductivity is carbon or boron nitride, and the material having low thermal conductivity is quartz or alumina.