JPS59232996A - Method and device for pulling up single crystal - Google Patents

Abstract

PURPOSE:To control easily the diameter of a pulled up single crystal with good responsiveness and to form the single crystal having uniform property and low dislocation density by controlling the temp. distribution of a B2O3 melt. CONSTITUTION:A single crystal 4 is formed by melting a semiconductor raw material and B2O3 in a crucible 6, immersing a sealant heater 7 protected with a heater cover 8 of boron nitride, etc. into the B2O3 melt, 2, adjusting the power of the heaters 5 and 7 to adjust the melts 1 and 2 to a prescribed temp. distribution, immersing a seed crystal 3 into a melt 1 of the semiconductor raw material and pulling up the seed crystal (the heater 7 and thermocouple 9 and moved according to the decrease in the level of the melt 1 with pull-up of the crystal 4 and the heater 5 is controlled by the thermocouple so that the specified temp. is maintained in the neighborhood of the boundary of the melt 1). If the diameter of the crystal 4 increases during the above-mentioned pulling up of the single crystal, the power of the heater 7 is increased to decrease the diameter of the crystal 4 to a desired value (the operation is reverse if the diameter decreases).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for pulling a semiconductor single crystal by a method (hereinafter referred to as LEC method).

In the LEC method, as shown in FIG. 1, the surface of a semiconductor raw material melt 1 is covered with a B203 melt 2, which is a sealant, and a seed crystal 3 is immersed in the surface of the raw material melt 1. This is a method of pulling up the single crystal 4 by pulling up the seed crystal 3. In order to improve the quality of this single crystal, improve yield, and increase efficiency in subsequent processes, it is important to control the diameter of the single crystal and keep it constant.

Conventionally, the diameter of the single crystal has been controlled by changing the power (output) of the heater 5 to adjust the temperature of the raw material melt 1, or by changing the pulling speed V. However, in the former method, the heat capacity of the heater 5, crucible 6, etc. is large, and the distance between the heater 5 and the single crystal 4 is large, so the response speed is slow and fine control cannot be performed. Conditions change,
There was a drawback that the temperature at the solid-liquid interface could not be kept constant.

In the latter method, the temperature gradient near the solid-liquid interface changes with the speed and the shape of the interface changes, so the properties of the single crystal change as the pulling speed changes, resulting in poor crystallinity.

becomes. Conventionally, it has been difficult to alleviate this temperature gradient, so there has been a drawback that the dislocation density of the single crystal increases due to thermal strain. This is because the present invention for B2O3 melt 2 was made to eliminate the above-mentioned drawbacks, and by controlling the temperature distribution of the B2O3 melt, the response of single crystal diameter control is quick and easy. It is an object of the present invention to provide a pulling method and apparatus for producing a single crystal that has uniform properties over the entire single crystal and has a low dislocation density.

A first aspect of the present invention is a method for pulling a single crystal in the liquid capsule Czochralski method, which is characterized in that the diameter of the single crystal is controlled by controlling the temperature distribution of the B2O3 melt.

A second invention of the present invention is an apparatus used in the first invention described above, which includes an annular heater that is immersed in the B2O3 melt and heats it, and a ring-shaped heater that is moved relative to the crucible. A single crystal pulling apparatus is characterized in that it is equipped with a device for pulling a single crystal.

The single crystal pulled by the present invention is, for example, Ga As
+Gap, l11-V group compound semiconductor of the periodic table such as InSb, TnP, InAs, etc., e.g. Zn
If-Vl of S, Zn5e, CdS, CdSe, etc.
It is made of a semiconductor such as a group compound semiconductor, a group (I) semiconductor such as Si or Ge, or a mixed crystal thereof.

Hereinafter, the present invention will be explained by examples using all the drawings. 2 and 3 are views showing an embodiment of the single crystal pulling apparatus of the present invention, FIG. 2 is a longitudinal sectional view of the apparatus, and FIG. 3 is a perspective view showing a sealant heater. In the figure, the same reference numerals as in FIG. 1 indicate the same parts.

In the figure, 7 is an annular sealant heater, which is immersed in the B2O3 melt 2. The sealant H-Turf is made of carbon, for example, and in order to protect it from the B2O3 melt 2, it is made of boron nitride (BN), pyrolytic boron nitride (pyrolytic boron nitride), etc., as shown in Figure 3. It is covered by a control heater cover 8.

Further, 9 is a pair of thermal lightning for measuring the entire temperature near the interface between the B2O3 melt 2 and the log 1 melt 1. Then, the power of the heater 5 is adjusted so that the temperature near the interface measured by the thermocouple 9 is constant.

The sealant heater 7 is provided with a device that moves up and down relative to the melt 6, and the heater 7
3 is melted, the crucible 6 is raised or the heater 7 is lowered to be immersed in the B2O3 melt 2. In addition, the position of the solid-liquid interface is determined by the sealant heater 7 and thermocouple 9 during pulling, as the liquid level in the crucible 6 decreases as the crystal grows.
The positions of these (7, 9) and screws are adjusted by moving 6 relatively upward or downward little by little so that the position of 132o3 relative to the interface between the 132o3 melt and the raw material melt does not change. Keep it constant. That is, this is possible because the thickness of the B2O3 melt 2 does not change and only the position in the axial direction shifts.

Next, a method for pulling a single crystal using the above-mentioned single crystal pulling apparatus will be described.

5- After melting the semiconductor raw material and B2O3 in the crucible 6, move the crucible 6 or the sealant heater 7 to melt the B2O3.
Immerse the heater 7 in the melt 2. Adjust the power of the heaters 5 and 7 to adjust the melt fj, 1 and 2 to a predetermined temperature distribution, and after immersing the seed crystal 3 in the melt 1 and allowing it to simmer, the seed crystal 3 is pulled up to form a single crystal. Raise 4. As the liquid level decreases, sealant heater 7 and thermocouple 9 are added to crucible 6VC.
move relatively.

The following methods are effective for single crystal pulling and fine control of diameter.

Generally, when the power of the sealant heater 7 is changed, B2O
The temperature distribution within the 3-melt 92 is as shown in FIG. 4 qualitatively.

In Figure 4, (a) shows when the power is small, (b) shows when the power is medium, and (c) shows when the power is small.

In the figure, the left end shows the heater 7 side, and the right end shows the single crystal 4 side.

From Fig. 4, if the power of the sealant heater 7 is set to dog,
As the temperature on the surface side of the single crystal 4 of the B2O3 melt 2 increases by 6 degrees, the radiant heat from the heater 7 to the crystal also increases, and the temperature gradient in the axial direction also decreases.

Therefore, when the diameter of the single crystal 4 increases, increasing the power of the encapsulant heater 7 increases the temperature of the B2O3 melt 2, reduces the amount of heat escaping from the single crystal 4, and increases the diameter of the single crystal 4. Become thinner. If the diameter of single crystal 4 becomes thinner,
If you do the opposite of the above, the diameter will increase.

By controlling the power of the encapsulant heater in this way, B2O3
By controlling the temperature distribution of the melt, the diameter of the single crystal 4 can be precisely controlled.

EXAMPLE A single crystal of a GaA, s semiconductor was grown using the single crystal pulling apparatus of the present invention shown in FIG. 2 and the conventional apparatus shown in FIG.
Each was produced by the LEC method using a 2O3 melt.

The temperature distribution of the B20 liquid and the raw material melt is as shown in FIG. It can be seen from FIG. 5 that the temperature gradient within the B2O3 melt according to the present invention is smaller than that of the conventional example.

Using these devices, GaAs semiconductor single crystals each having a diameter of 50+uLX and a length of 100 mm were fabricated. However, in the case of the present invention, B2O3 is
The diameter of the single crystal was controlled by controlling the temperature distribution of the melt.

The variation in diameter of the obtained single crystals according to the present invention was 10 mm, and that of the conventional example was ±7 mm711.

In addition, the distribution of dislocation density (XIO'/d) of the wafer taken from the front part of the single crystal is shown in Figure 6 (a).
As shown in (b), (a) the figure is according to the present invention, (
b) The figure shows a conventional example.

From FIG. 6, it can be seen that in the case of the present invention, the variation in dislocation density is smaller and lower than that of the conventional example.

Also, the front part and rear part (back part) of each single crystal.
The average dislocation densities of the wafers sampled are shown in Table 1.

Table 1 From Table 1, it can be seen that the average dislocation density of the sample according to the present invention is lower than that of the conventional example.

From the above-mentioned examples, when the single crystal pulling apparatus according to the present invention is used, the temperature distribution of the B2O3 melt can be controlled, and as a result, the diameter variation is small and the dislocation density is small over the entire single crystal. GaAs with low and little variation
It was found that a single crystal could be obtained.

As described above, the method of the present invention is a method for pulling a single crystal using the liquid capsule Czochralski method.
By independently controlling the temperature distribution of only the melt, when the diameter of the single crystal becomes thicker, B20g is used.When the temperature of the melt is increased and the diameter becomes thinner, B20g
The diameter is controlled by lowering the temperature of the O3 melt and increasing the diameter. This method has the advantage of 9- good thermal responsiveness and the ability to quickly and easily control the diameter of the single crystal, thereby improving yield and efficiency in subsequent steps.

In addition, the method of the present invention can optimally control the temperature gradient near the solid-liquid interface and the shape of the interface by controlling the temperature distribution of the B2O3 melt, so that the dislocation density can be reduced throughout the single crystal. There is an advantage that a semiconductor single crystal having low and uniform characteristics can be manufactured.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an example of a conventional single crystal pulling apparatus. FIGS. 2 and 3 are views showing an embodiment of the single crystal pulling apparatus of the present invention, with FIG. 2 being a longitudinal sectional view of the apparatus, and FIG. 3 being a perspective view showing a sealant heater. FIGS. 4(a), (b), and (c) are diagrams qualitatively showing the temperature distribution in the B2O3 melt when the power of the sealant heater is changed, respectively. Figure 5 shows B2O3 in the embodiment of the present invention and the conventional example.
FIG. 10 is a diagram showing the temperature distribution of the melt and the raw material melt. FIGS. 6(A) and 6(B) 11-1 are diagrams showing the dislocation density distribution state of wafers taken from the front part of single crystals obtained by the method of the present invention and the conventional method, respectively. 1... Raw material melt, 2...-B208 melt, 3...
・Seed crystal, 4...single crystal, 5...heater, d...
- Crucible, 7... Sealing agent heater, 8... Heater cover, 9... Thermocouple. 11-71Figure 7r2Figure 73Figureff4Figure (A) (C). Hiro 5 figure death & (-C) → Yoshi 6 figure c mouth)

Claims (3)

[Claims] (1) A single crystal pulling method using the liquid capsule Czochralski method, which is characterized in that the diameter of the single crystal is controlled by controlling the temperature distribution of a 20 g B melt. (2) An apparatus for pulling a single crystal using the liquid capsule Czochralski method, which is equipped with an annular heater that is immersed in the B20B melt to heat it, and a device that moves the heater relative to the crucible. A single crystal pulling device characterized by: (3) The single crystal pulling apparatus according to claim 2, wherein the heater is covered with boron nitride or pyrolytic boron nitride.