JPH03232790A - Quartz crucible for apparatus for pulling up silicon single crystal - Google Patents

Abstract

PURPOSE:To decrease the oxygen concentration in a silicon single crystal produced by a rotary pull-up method while minimizing the change of properties other than oxygen concentration by using a quartz crucible for holding molten silicon and having a corner thickness meeting a specific condition. CONSTITUTION:The thickness of the corner part of a quartz crucible for holding molten silicon is made to be thicker than that of the side wall or bottom wall of the crucible, i.e., the thickness of at least the center of the corner is made to be >=1.3 times that of the side wall or the bottom wall.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a quartz crucible for use in an apparatus for producing silicon single crystals by a rotational pulling method.

[Conventional technology] When manufacturing silicon single crystals by the rotational pulling method, the second
As shown in the figure, a silicon single crystal 1 is pulled out from a silicon melt 5 held in a quartz crucible 2 while being rotated. Important qualities such as strength and gettering properties of impurities of wafers manufactured from silicon single crystal 1 vary depending on the oxygen concentration (Oi value) in the crystal, so it is important to improve wafer quality. It is necessary to control the O1 value to various values depending on needs and how the wafer is used.

The Oi value in the silicon single crystal 1 is influenced by the amount of oxygen released from the quartz crucible 2. Normally, the O1 value is adjusted by changing the temperature of the quartz crucible 2 depending on the rotation speed of the silicon single crystal 1 or the quartz crucible 2, the positional relationship between the quartz crucible 2 and the heater 4, and the like. However, if the rotation speed of the quartz crucible 2 or the positional relationship between the quartz crucible 2 and the heater 4 is changed, the convection of the silicon melt 5 in the quartz crucible 2 and the thermal history given to the silicon single crystal 1 will change. As a result, qualities other than the O1 value, such as the crystal radial distribution of dopants and the latent product distribution of oxygen precipitation, also change.

Therefore, there is a need for effective means for controlling only the O1 value while minimizing the influence on quality other than the Oi value.

[Problems to be Solved by the Invention] The present invention aims to minimize changes in quality other than the O1 value, such as dopant distribution in the crystal radial direction, oxygen precipitated tFiI distribution, etc., in the production of silicon single crystals by the rotating single-crystal method. The purpose is to reduce the Oi value while suppressing the Oi value.

[Means and effects for solving the problem] The quartz crucible for a silicon single crystal pulling device of the present invention that solves the above problems has a wall thickness of the corner of the quartz crucible that accommodates the silicon melt,
is thicker than the side wall or bottom of the crucible, and the wall thickness at least at the center of the corner is 1.3 times or more the wall thickness of the side wall or bottom. It is something to do.

The present inventors pulled a silicon single crystal l under several different conditions, such as the positional relationship between the quartz crucible 2 and the heater 4 and the crystal rotation speed, using the apparatus shown in FIG. As a result of a detailed investigation of the relationship between the distribution and the oxygen concentration in the silicon single crystal 1, we found that the oxygen concentration in the silicon single crystal 1 is closer to the maximum temperature in the quartz crucible 2 than to the average temperature in the quartz crucible 2. It was found that the correlation is strong, and that the higher the temperature of the highest temperature part, the higher the oxygen concentration in the silicon single crystal 1 tends to be.

When we investigated the temperature distribution of the melt 5 in the quartz crucible 2, we found that
As shown in FIG. 3, the temperature is highest at the corner 3 of the quartz crucible 2.
We investigated ways to lower the temperature. By keeping the wall thickness of the side wall 7 and the bottom 8 of the quartz crucible 2 constant, and changing the wall thickness of the corner 3, the corner 3, the side wall 7, and the bottom 8
The quartz crucibles 2 were made with eight different ratios α to the wall thickness, and the manufacturing conditions other than the shape of the quartz crucibles 2 were the same, and while growing crystals, the temperature at the corner 3 of the quartz crucible 2 was varied. l
1 liter determination was performed. As a result, it was found that the temperature of the corner 3 can be lowered by increasing α.

Next, the crystal was pulled under the above conditions, and the relationship between α and the oxygen concentration in the crystal was investigated. As a result, the acidity concentration in the crystals did not change clearly when α was less than 1.3 (it remained at a relatively high value, but it was observed that it decreased significantly when α increased to 1.3 or more). From the results of these considerations, silicon single crystal 1 can be obtained by setting α to 1.3 to 1-.
It has been found that the oxygen concentration inside can be reduced. Furthermore, more preferable results can be obtained by setting the value of α to 1.5 or more.

Note that the wall thickness of the corner 3 of the quartz crucible 2 may be such that α is 1.3 or more at least at the center. The thickness of the center portion is determined by the straight line g on the outer surface of the side wall portion 7 shown in FIG.
It is expressed as the distance between the intersection points Q and H between a straight line n passing through the intersection point P of .

The reason for this is thought to be that the oxygen concentration in the silicon melt 5, which is the source of crystal pulling, is greatly affected by the oxygen elution from the hottest part of the contact surface between the quartz crucible 2 and the silicon melt 5. It will be done.

Therefore, the best way to reduce the oxygen concentration in the silicon single crystal 1 is to lower the temperature of the hottest part of the contact surface between the quartz crucible 2 and the silicon melt 5, that is, the corner part 3, especially the center part. This is because it is thought to have a negative effect. In fact, as shown in the example below, this QR
When the wall thickness between the two sides was made 1.3 times or more the wall thickness of the side wall portion 7 and the bottom portion 8, a decrease in the Oi value was observed.

[Example] As an example of the present invention, as shown in FIG. 1, the thickness of the center QR of the corner 3 of the quartz crucible 2 is 12 mm, the thickness of the side wall 7 and the bottom 8 is gmm, The wall thickness of the corner portion 3 is 12 mm from the center portion QR toward the side wall portion 7 and the bottom portion 8.
Quartz crucible 2 gradually decreased from 8mm to 8mm (
α=1. 5) was used to melt 45 kg of silicon polycrystal, and 30 kg of silicon single crystal 1 was pulled from the melt 5.

On the other hand, as a comparative example, as shown in Figure 2, the wall thickness was 8 m.
30k using a quartz crucible (α = 1.0) with constant m
A silicon single crystal 1 of g was pulled up.

Note that various conditions such as melt amount, crystal rotation speed, crucible rotation speed, crystal pulling speed, etc. were the same as in the examples of the present invention.

Silicon single crystal 1 obtained in Examples and Comparative Examples
As a result of evaluating the Oi value ratio, the Oi value of the silicon single crystal 1 obtained in the example was reduced by 10% compared to that in the comparative example.

Furthermore, as another embodiment of the present invention, a quartz crucible 2 with α=1°3 and 1.4 was used, and 3.
A 0 kg silicon single crystal 1 was pulled up and the above comparative example (α-
As a result of evaluating the Oi value ratio with the silicon single crystal 1 obtained in 1, 0), the Oi value of the silicon single crystal 1 obtained in these examples was 5% and 8%, respectively, compared to that in the comparative example. % reduction.

In addition, as a reference example, 30 kg of silicon single crystal 1 was pulled in the same manner as above using a quartz crucible 2 with α = 1.1 and 1.2, and the silicon single crystal 1 obtained in the above comparative example (α = 1.0) was pulled. As a result of evaluation based on silicon single crystal 1 and Oi value ratio,
O of silicon single crystal 1 obtained in these reference examples
The i values are only 0 for those in the comparative example, respectively.
．． It was reduced by only 5% and 1%.

[Effects of the Invention] As described above, in the quartz crucible for use in a silicon single lumen extraction device of the present invention, the wall thickness of the corner of the quartz crucible containing the silicon melt is equal to or greater than that of the side wall of the crucible. The wall thickness of the corner portion is thicker than that of the bottom portion, and the thickness of at least the center portion of the corner portion is 1.3 times or more the thickness of the side wall portion or the bottom portion. When silicon single crystals are produced by the rotational pulling method using the quartz crucible according to the invention, the Oi value can be reduced while minimizing quality changes other than the Oi value.

Additionally, as an accompanying effect, the time during which the quartz crucible can hold the melt can be extended. This is more effective when pulling a plurality of ingots from one quartz crucible or when pulling a long ingot.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view schematically showing the structure of an embodiment of the quartz crucible of the present invention, and FIG. 2 is a cross-sectional view schematically showing the main parts of a silicon single crystal pulling apparatus using a conventional quartz crucible. 3 is a diagram showing an example of the temperature distribution inside a conventional quartz crucible. 1... Silicon single crystal, 2... Quartz crucible, 3...
・Crucible corner, 4... Heater 5... Silicon melt, 6... Graphite crucible, 7... Crucible side wall, 8...
- Crucible bottom, 9...lowest part of the crucible.

Claims (1)

[Claims] The wall thickness of the corner of the quartz crucible containing the silicon melt is thicker than the wall thickness of the side wall or bottom of the crucible, and the wall thickness of at least the central portion of the corner is thicker than the wall thickness of the side wall or bottom of the crucible. A quartz crucible for use in a silicon single crystal pulling device, characterized in that it is 1.3 times or more thicker than its wall thickness.