JPS5935094A - Method and apparatus for preparation of silicon single crystal - Google Patents

Abstract

PURPOSE:To obtain a silicon single crystal containing a proper amount of oxygen, by contacting molten silicon with silicon oxide in the course of pulling the silicon single crystal from molten silicon using a silicon nitride or silicon carbide crucible. CONSTITUTION:High purity molten Si 3 is put into a graphite crucible 2 lined with an Si3N4 or SiC layer 1, and a silicon single crystal 4 is pulled by using a seed silicon crystal. In the above process, a material 5 obtained by coating the tungsten core weight 7 with a silicon oxide 6 such as SiO2 or SiO (e.g. quartz glass) is sent to the bottom of the crucible 2. The pulled silicon single crystal 4 contains the oxygen transferred from the material 5, and the silicon wafer prepared therefrom is free from the problems of strain-development during thermal treatment which are inherent to the wafer prepared from oxygen-free silicon single crystal.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for producing a silicon single crystal with a controlled oxygen concentration.

Generally, a quartz glass crucible is used for silicon single crystals at C7 and legal pressure, and silicon is melted in this quartz glass crucible and pulled using a seed crystal. At this time, a portion of the quartz glass is dissolved in the molten silicon, and oxygen is mixed into the silicon single crystal. The oxygen concentration in this silicon single crystal depends on the contact area between the molten silicon and the quartz glass crucible, the temperature, the size of convection, etc., and improvement has been required for quality control purposes, but it is impossible to control this. It was difficult.

Recently, one crucible using silicon nitride or silicon carbide has been developed.
A technique has been developed to pull up silicon crystals by using a silicon crucible, but in these cases, there is no oxygen contamination from the silicon crucible, so it is difficult to obtain a 1.2 oxygen-free structure during heat treatment such as oxidation treatment or diffusion treatment of the silicon wafer. The accompanying wafer distortion (slip) is likely to occur, and I, Si, super I, S
This has been a problem in applications that require precision materials such as I.

In the present invention, 1-, in order to make the silicon single crystal a predetermined oxygen concentration, 5I8N4 or Yi SiC material is used for the pot, and silicon oxide is used to melt the required amount of oxygen per I7 into the molten silicon. It is designed so that they are in contact with each other.

Embodiments of the present invention will be explained below with reference to the drawings.

In FIG. 1, 1 is a silicon nitride film coated with carbon on its inner surface. 3 is molten silicon, a silicon single crystal that is being pulled up by 4 times. 5 is a charge according to the present invention, and as shown in FIG. 2, it has a structure in which a tungsten rod 1 is inserted into a quartz glass outer tube 6 in order to have a higher specific gravity than bath-fused silicon. , deposited in silicon melt.

The structure of the present invention is as follows.The molten silicon is not contaminated with oxygen from the crucible, but instead the quartz glass deposited in the silicon melt melts from its surface, and the oxygen concentration of the silicon melt increases. This will ultimately determine the oxygen concentration in the silicon single crystal. El''i which controls the oxygen concentration is proportional to the surface area of the quartz glass in contact with the molten silicon, temperature, etc., and thus the necessary conditions can be determined.

FIG. 3 shows a method of contacting quartz glass, not by depositing it as in FIG. 1, but by immersing it by supporting a quartz glass rod 8 above.It comes into contact with molten silicon. To adjust the area of the quartz glass, move the quartz glass rod up and down as shown by the arrow, or use multiple rods at the same time if necessary].When using such a rod Another advantage is that #i molten silicon can be easily stirred.

Melt/recon 41 by the method shown in Figure 1 and Figure 3.
The crystal in silicon was pulled up 4 inches from φ, but the contact surface of the quartz glass was kept at 50 cm.
FIG. 4 shows how the oxygen concentration changes along the length of the silicon single crystal when the silicon single crystal is pulled. For reference, we have also listed cases (5) when using a quartz glass JL crucible and cases (03) when using a Si*N+ crucible, but as shown in the figure, when using a quartz glass crucible, the In contrast, in the case of the present invention, it is 11. It hasn't changed much. On the other hand, when using a silicon nitride crucible, the oxygen concentration is extremely low and
'L cannot be increased or decreased.

In the case of the present invention, when the surface area of quartz glass is 50α2 for molten silicon 4"y, ((-'+
+ (IJl12) Oxygen concentration is 7 to 9 X ] 01
7at□(m') and t1\\ are constant, and by changing the surface area of the quartz glass, -C is constant in the length direction of the single crystal! ) Oxygen concentration can be changed easily.

Figure 5 shows the relationship between the lees appearance of 8i(-)y and the oxygen concentration in the crystal. However, the same effect can be obtained with a crucible coated with silicon carbide, and a crucible made of silicon nitride, silicon carbide alone, or a composite thereof may also be used. The refined silicon oxide is quartz glass, which is easily available as it has a high purity, but other materials such as silicon oxide or quartz may also be used. Further, in order to bring quartz glass into contact with molten silicon, some measures are required since the specific gravity of quartz glass is smaller than that of molten silicon, but this is not limited to the case of the embodiment.

[Brief explanation of the drawing]

The figures show embodiments of the present invention; FIGS. 1 and 3 are schematic longitudinal sectional front views of an apparatus for carrying out the method of the invention; FIG. 2 is a schematic vertical sectional front view showing a charge; and FIG. 4 is a silicon A diagram showing changes in oxygen concentration in the length direction of a single crystal, Figure 5 is 81
09. This is a diagram showing the relationship between the amount of elution and the oxygen concentration in the crystal. 1. Silicon nitride film 2. Carbon profiteering 3.
... Molten silicon 4 ... Silicon single crystal 5 ...
・Includes 6...quartz glass outer tube 1...ri 2
・Gusubun rod 8...Quartz glass rod-shaped body Inventor: Hideo Nagashima Inventor: 1) Hideo Michi - Inventor: Hidetsu Matsuo Applicant: Toshiba Ceramics Co., Ltd. Figure 1 Figure 4! R&J 5th figure) ↑ 020

Claims (4)

[Claims] (1) When producing a silicon single crystal from molten silicon using a crucible whose inner surface is made of at least SiSN4 or Fis+c, a controlled method characterized by bringing silicon oxide into contact with the molten silicon in the crucible. f
A method for producing silicon single crystals having a certain oxygen concentration. (2) It is preferable that the silicon oxide is silicon monoxide or silicon dioxide. (3) Silicon oxide is quartz glass with lli junk inside! The method according to claim 1, characterized in that 1 and π are the same. (4) At least the inner surface is 5isN* or S r
1. An apparatus for producing silicon crystals, comprising: a crucible made of C, a silicon raw material charged into the crucible, and silicon oxide charged into the crucible.