JPS5964591A - Single crystal pulling equipment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to the Czochralski method (hereinafter referred to as CZ method).
Alternatively, the present invention relates to an apparatus for pulling a single crystal using the liquid capsule Czochralski method (hereinafter referred to as LEC method).

(Background Art) An apparatus for pulling a single crystal by the CZ method or the LEC method uses a thick-phase melt 4 (e.g., Ga
As needed, the entire surface was covered with B2O3 shaving liquid 5 (in the case of LEC method), and a seed crystal 6, which was drawn on the surface of the melt 4 with several lines on the two axes 8, was immersed and soaked in it. After that, a device is used to pull up the seed crystal 6 and pull up the single crystal 7 (eg, GaAs). 1 is an in-furnace heater, 2 is a susceptor,
9 is a crucible support shaft.

In this case, conventionally, one heater was used to maintain the temperature distribution inside the furnace as shown in the figure on the right.

However, this method does not allow high quality single crystals to be obtained for the reasons described below.

One heater can produce at most 4 liters of melted liquid.
The temperature distribution in the furnace, which has an important role in obtaining high-quality single crystals, has a crystal diameter of about tlI due to changes each time.
The position of the melt, the thickness of the B2O3 melt, and the shape of the heated paulownia are determined, and cannot be controlled from the outside.

There is an appropriate temperature gradient for completely stable crystal growth.
In order to grow a low-dislocation single crystal, a region with such a temperature gradient must exist over a wide range. However, since the temperature distribution cannot be well controlled with a single heater, it is necessary to find an ideal temperature gradient. It is difficult to widen the scope of the field.

Therefore, after the divine example 1o, the single crystal 7 is the B2o3 melt 5
(B203 is a heat-retaining phase and has a relatively low gradient in one liquid of B2O3) and has a small temperature gradient within the crystal (dislocations are difficult to enter). Even if the single crystal 7 can be grown at a certain position, when the single crystal 7 comes out of the B2O3 melt 5, the temperature gradient in the crystal becomes suddenly large and the number of dislocations increases.

Therefore, in order to make the B2O5 melt 7115 have low dislocations even when it comes out of the B2O3 melt, it is necessary to effectively heat the single crystal 7 that comes out of the B2O3 melt, but it is a waste of time to do this with just one heater. Right (The dotted line in the figure is the required temperature gradient.

In addition, if the crucible position is further lowered to reduce the temperature gradient above the B2O3 melt 5, the B2O3 melt
The temperature gradient in the temporary region becomes too small, resulting in poor growth, and the amount of heat escaping upward decreases, causing the solid-liquid interface to become concave downward, causing polycrystalization from the lineage.

In this way, with one heater, it is not possible to maintain the dislocation density at a low level at ψ1°^; part (bank part) immediately after the seed layer of the single crystal.

(Disclosure of the Invention) The present invention has been made to solve all of the above-mentioned problems, and it facilitates the adjustment of the temperature gradient so that the temperature gradient is suitable for stable growth of a single crystal. The present invention provides a partial crystal pulling apparatus that can stably obtain a single crystal with low dislocations due to the long range.

The present invention provides an apparatus for pulling single crystals by the Czochralski method, in which the furnace heating heater is composed of two or more stages of heaters, and among the heaters, the upper heater that heats the crystal part during pulling is This is a single crystal pulling device characterized by having an upwardly open shape or having a resistance at the upper part of the heater smaller than that at the lower part of the heater.

The single crystal pulled by the device of the present invention is I-
Group 1' compounds (e.g., GaAs, InAs, Gap,
InP, etc.), 11-W group compounds (e.g., 'Zn5e, etc.)
or mixed crystals thereof, or single crystals of semiconductors such as Si and Ge, oxides, nitrides, carbides, etc., which are particularly effective when pulled by the LEC method.

Hereinafter, the present invention will be explained using examples.

FIG. 2 is a longitudinal sectional view and a temperature distribution diagram showing an embodiment of the device of the present invention. In the figure, the same reference numerals as in Figure 1 indicate the same parts. The first difference in the diagram is
The in-furnace heater 10i is divided into two stages: a two-part heater +1 and a lower heater 12. The lower heater 12 mainly heats the four melting surfaces of the raw material. -J two-part heater 11
is for making an ideal single crystal internal temperature fraction A V3. The upper heater 11 is, for example, a circle Φ(
1! It has the shape of the side of a table.

If you increase the power of this upper heater 11, the solid line in Figure 3 ■
As shown in (the present invention), the temperature gradient within a single crystal can be maintained at the minimum value required for crystal growth over a wide range. Incidentally, if the upper heater is cylindrical as shown by the dotted line in Figure 3, the hottest part will be closer to the center of the upper heater, as shown by the dotted line ■ in the figure on the right, creating a temperature distribution that hinders crystal growth and solidification. This makes the liquid surface concave downward, causing polycrystalization. By forming the heater into a shape that is open on one side as in the present invention, this problem will not occur even if the upper heater is sufficiently long. Also, the chain line ■ in Figure 3 is □1 no f
l in the case of one heater! lr: indicates degree distribution.

14 indicates the surface of the B2O3 melt.

The heater on the father part does not have to be conical as shown in Figure 2, but as shown in Figure 4. -W It may be thick and cylindrical. In this case as well, the temperature distribution shown by the solid line ■ in FIG. 3 can be easily obtained.

The longer the length of the upper heater, the better.
Care must be taken to avoid a temperature gradient as shown by the dotted line ■ in the figure. Further, fine adjustment of the temperature distribution may be carried out by using the entire pool 13 as shown in FIG. 2 and by changing its shape, dimensions, position, etc.

The in-furnace heater of the present invention is not limited to a two-stage heater as shown in the embodiment in FIG. is obtained.

(Example) A GaAs single crystal was pulled using the apparatus of the present invention as shown in FIG.

A quartz tube with an inner diameter of 150 mm was used, the charge j1j of GaAs polycrystalline raw material O.1 was a hook, the charge of 4 KyXB203 was about 500y, the furnace pressure was 5aL+n, the pulling speed was +On+m/hour, and the pull was 2. Axis rotation 8r pan,
The rotation of the crucible support shaft was 9 rpm, and the rotation was 2 digits as 2 parts <100>.

The diameter of the single crystal was controlled by finely adjusting the power of the lower heaters 11 and 12. (Usually, only the lower heater 12 was adjusted, and when the lower heater 12 did not work well, the upper heater 11 was adjusted.) The diameter of the obtained single crystal was about 70 mm, and the length was about 200 mm.

As a result, even though the lineage tends to become polycrystalline as the diameter increases, all of the specimens were single crystals even with such a large diameter.

<100 cut from the front and back parts of a single crystal
>The entire wafer was etched at MI<oH, and the etch bit density (EPD)'fr was determined and the results are shown in Table 1.

For comparison, the EPD''i of a single crystal produced using a conventional pulling device f consisting of only one heater was determined.

Table 1 From Table 1, it can be seen that the device of the present invention has an EP
It can be seen that D becomes very low and there is almost no change from the front part to the back part.

(Effects of the Invention) The single crystal pulling apparatus of the present invention configured as described above has the following effects.

The heater inside the furnace consists of two or more stages.
Among these heaters, the upper heater that heats the pulled single crystal part is of the shape that opens upward, or the resistance of the upper part of the heater is lower than that of the lower part of the heater, so that the single crystal is heated by the radiation of the upper heater. , the single crystal is B2O3
B 203 Melt 710 even when in the melt. Since the temperature gradient in the single crystal is small even when it comes out of the single crystal, the temperature at the top of the single crystal can be lowered appropriately, making it possible to maintain the temperature gradient necessary for crystal growth throughout the single crystal. Further, these heaters can be easily adjusted from the outside.

In other words, it is possible to easily maintain the temperature gradient within the single crystal at a small value sufficient for growth throughout the entire process of single crystal growth, resulting in a low dislocation density from the noron part to the back part of the single crystal. Single crystals can be stably obtained.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view and a temperature distribution diagram showing an example of a conventional single crystal pulling apparatus. FIG. 2 is a longitudinal sectional view and a temperature distribution diagram showing an embodiment of the device of the present invention. FIG. 3 is a diagram showing the temperature distribution in the case of a two-stage heater, a cylindrical upper heater, and a single heater. l, 10- Furnace heating heater, 2... The Scepter,
3 Crucible, 4 Raw material melt, 5... B2O3 melt, 6...
・Seed crystal, 7・Medium crystal, 8... pull double axis, 9 crucible support +1111, II ・"two-part heater, 12...
Lower heater, 13.../- led, 14B203 melt surface.

Claims (1)

[Claims] (1) In an apparatus for pulling single crystals using the Czochralski method, the furnace heating heater consists of two or more stages of heaters, and the upper heater that heats the pulled single crystal part opens upward. 1. A single crystal pulling device characterized in that the resistance of the upper part of the heater is smaller than that of the lower part of the heater.