JP3134415B2 - Single crystal growth method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to semiconductors such as Si, Ge, etc., by the Czochralski method (CZ method), the vertical Bridgman method (VB method), the vertical slow cooling method (VGF method), etc.
aAs, GaP, GaSb. InAs, InP, InS
III-V compound semiconductor single crystal such as b, CdTe, Hg
_The present invention relates to a method for growing a group II-VI compound semiconductor single crystal such as _1-x Cd _x Te and ZnSe.

[0002]

2. Description of the Related Art Conventionally, in order to grow a single crystal having few crystal defects, it has been known that the solid-liquid interface shape of the crystal is made flat or convex toward the melt. In order to obtain such a solid-liquid interface, Japanese Patent Application Laid-Open No. 62-216995 proposes disposing a heat shield plate on the inner wall of a crucible.
No. 58881 proposes growing a single crystal while placing a thermocouple in a crucible and monitoring the melt temperature near the solid-liquid interface.

[0003]

However, Japanese Patent Application Laid-Open No. 62-21 / 1987
In the method of 6995, it is difficult to keep the shape of the solid-liquid interface constant over the entire length of the crystal because the temperature distribution near the solid-liquid interface changes as the amount of the raw material melt decreases. In addition, the reproducibility was poor because the shape of the solid-liquid interface greatly changed depending on how the heat shield plate was installed.

Therefore, the present invention provides a CZ method, a VB method, a VG method.
In a method for growing a single crystal from a melt, such as the F method, the above-mentioned drawbacks are eliminated, the shape of the solid-liquid interface is easily controlled, and a method for growing a single crystal having excellent crystallinity is provided. is there.

[0005]

According to the present invention, there is provided a method for growing a single crystal from a melt, wherein (d ² T / dz ² ) (T is the temperature, A method for growing a single crystal, characterized in that the temperature environment is adjusted so that (z is the coordinate in the growth direction) is 0 or negative. The above-mentioned temperature environment is obtained, for example, by arranging three or more thermocouples in the vicinity of the solid-liquid interface on the side surface of the grown crystal, detecting the temperature distribution in the growth direction, and setting the above (d ² T / dz ² ) to 0 or The temperature environment can be adjusted by controlling the plurality of heaters of the growth furnace to be negative.

[0006]

FIGS. 1 and 2 are conceptual diagrams of a single crystal manufacturing apparatus for carrying out the present invention. FIG. 1 shows an apparatus for carrying out a CZ method, and FIG. 2 shows an apparatus for carrying out a VB method. . In the apparatus shown in FIG. 1, a crucible 5 is supported at the center of a chamber 4 so as to be rotatable up and down by a lower shaft 6. The crucible 5 contains a raw material melt 7 and a liquid sealant 8, and a heater is provided around the crucible 5. 13,1
4 and a heat insulating material 15 are arranged to form a predetermined temperature environment,
After the seed crystal 10 attached to the upper shaft 11 is sufficiently mixed with the raw material melt 7, the single crystal 12 is grown by gradually pulling it while rotating. Thermocouples 1, 2, and 3 are arranged near the crystal-solid interface 9, and a measurement signal is sent to the computer 16 to control the heaters 13 and 14. d ² T / dz ² )
Is adjusted to be 0 or negative.

In the apparatus shown in FIG. 2, a crucible 18 is rotatably supported by a lower shaft 19 at the center of a chamber 17 and a seed crystal 20 is mounted on the bottom of the crucible 18. And a heater 2 is provided around the crucible 18.
A predetermined temperature environment is formed by arranging 3, 24, 25 and the heat insulating material 26, and the crucible 18 is gradually lowered while rotating to grow a single crystal 27 from the upper end of the seed crystal 20. Thermocouples 1, 2, and 3 are arranged near the crystal-solid interface 28, and a measurement signal is sent to the computer 16 so that the heaters 23, 24,
By controlling 25, the temperature environment is adjusted so that (d ² T / dz ² ) near the solid-liquid interface during the growth of the straight body portion becomes zero or negative.

In the single crystal growing method as described above, since the crystal growth rate is low, it is known that the heat distribution in the crystal of the straight body portion which is considered to be in thermal equilibrium satisfies the following Laplace equation. ing. (D ² T / dr ² ) + (1 / r) (dT / dr) + (d ² T / dz ² ) = 0 Here, the coordinates are r in the crystal diameter direction and z in the growth direction. I took it. The temperature distribution in the crystal diameter direction was approximated by a quadratic function, and was set as the following equation. T = ar ² + To... Here, To is the temperature of the crystal center (r = 0). Assuming this equation to be the temperature distribution near the solid-liquid interface inside the crystal, the solid-liquid interface shape is convex toward the melt when a> 0, and a
It can be seen that when <0, it is concave on the melt side, and when a = 0, it is flat. By substituting the equation into the equation, the following equation is obtained, and it can be seen that the relationship in Table 1 holds. (D ² T / dz ² ) =-4a

[0009]

[Table 1]

That is, if the second order differential of the temperature distribution in the growth axis direction (z) near the solid-liquid interface in the crystal can be known, the solid-liquid interface shape of the grown crystal can be estimated. Figure 1,
In the apparatus shown in FIG. 2, when the temperature is measured by three thermocouples arranged above and below the solid-liquid interface, the temperature can be shown as a curve as shown in FIG. By calculating (d ² T / dz ² ) by approximation with a function, it can be seen that the solid-liquid interface shape can be estimated as shown in Table 1 above. In addition, it was calculated as described above (d
² T / dz ² ) is a value on the outer periphery of the crystal and not on the inside of the crystal, so it was worried that the shape of the solid-liquid interface was strictly reflected. If the emissivity of the protective tube is the same as that of the crystal, the value can be made closer to the value inside the crystal. In the present invention, the outputs of the plurality of heaters in the furnace are adjusted, and (d ² T / dz ² ) is calculated each time,
While judging whether the value is positive or negative, it is fed back to the output of the heater to grow the straight body while keeping the solid-liquid interface shape always flat or convex to the melt side. The above description has been made on the assumption that a columnar crystal is grown. However, the present invention is not necessarily limited to a columnar crystal, and a crystal close to a columnar column is similarly effective.

[0011]

【Example】

(Example 1) Ga was produced by the LEC method using the apparatus shown in FIG.
As single crystals were produced. 2.5 kg of GaAs polycrystalline raw material and 200 g of B ₂ O ₃ were placed in a 4-inch diameter pBN crucible.
Was accommodated. The thermocouple is obtained by putting W-Re in a protective tube made of Mo, and the thermocouples are arranged along the circumference at a position 35 mm from the center of the furnace, and the first thermocouple is arranged from the surface of the raw material melt. The upper thermocouple was held at a height of 5 mm, the second thermocouple at a height of 10 mm, and the third thermocouple at a height of 15 mm. The temperature gradient in the growth axis direction was approximated to a quadratic function as shown in FIG. 3 from the measured values of the three thermocouples, and (d ² T / dz ² ) near the solid-liquid interface became −10 to −4 (K / cm). ^When the crystal was grown by adjusting the output of the upper heater so as to fall within the range of ² ), a long crystal having a diameter of 2 inches and a length of 180 mm was obtained. The obtained crystals were all single crystals, and the solid-liquid interface shape was found to be a convex state protruding 3-5 mm toward the melt over the entire crystal. EPD was 8000 or less in the whole crystal, and no increase in EPD was observed even at the tail portion. Further, the same experiment as above was repeated six times, and similarly good results were obtained.

(Embodiment 2) Using the apparatus shown in FIG.
A GaAs single crystal was manufactured by the VB method. 1.6 kg of GaAs polycrystalline raw material and 1 kg of pBN crucible having a diameter of 2 inches
It contained 00 g of B ₂ O ₃ . Thermocouple W-Re to Mo
The thermocouple was placed in a protective tube, and three thermocouples were arranged along the circumference at a position 5 mm from the wall of the crucible, and the first thermocouple was at a height of 5 mm upward from the surface of the raw material melt. The second thermocouple was held at a height of 10 mm and the third thermocouple was held at a height of 15 mm. From the measured values of the three thermocouples, the temperature gradient in the growth axis direction is approximated to a quadratic function as shown in FIG.
(D ² T / dz ² ) near the solid-liquid interface is -10 to -4 (K
/ Cm ² ) by growing the crystal by adjusting the output of the upper heater so that a single crystal can be obtained entirely, and the solid-liquid interface shape is 3 to 3 mm on the melt side over the entire crystal.
It turned out that it was a convex state protruded by 10 mm. Also,
EPD was 10 ⁴ or less in the whole crystal, and no increase in EPD was observed even in the tail portion. Further, the same experiment as above was repeated three times, and similarly good results were obtained. On the other hand, when a single crystal was grown in the same manner as in Example 2 without detecting the temperature distribution, the entire amount of the single crystal could not be obtained, for example, lineage polymorphization occurred at the tail.

[0013]

According to the present invention, by adopting the above structure, it is possible to grow crystals in the straight body while confirming the solid-liquid interface shape of the crystals. It has become possible to obtain a uniform single crystal with few defects.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a single crystal manufacturing apparatus for carrying out the present invention.

FIG. 2 is a conceptual diagram of another single crystal manufacturing apparatus for carrying out the present invention.

FIG. 3 is a graph of a temperature distribution near a solid-liquid interface measured by three thermocouples in an example.

────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) C30B 1/00-35/00 CA (STN) JICST file (JOIS)

Claims (2)

(57) [Claims] 1. A method for growing a single crystal from a melt, comprising: (d ² T / d) near the solid-liquid interface of the crystal being grown in the straight body.
z ² ) (T is a temperature, z is a coordinate in a growth direction) and a temperature environment is adjusted so as to be zero or negative. 2. A temperature distribution in a growth direction is detected by vertically arranging three or more thermocouples in the vicinity of a solid-liquid interface near a side face of a grown crystal, and when (d ² T / dz ² ) is 0 or negative. The heater of the growth furnace is controlled so as to be as described above.
The method for growing a single crystal according to the above.