JPH06293588A - Production of semiconductor single crystal - Google Patents

Abstract

PURPOSE:To provide a process for production capable of improving a single crystallization rate, decreasing the generation rate of oxygen induced lamination defects and increasing the number of service times of a graphite crucible in the production of the semiconductor single crystal by a pulling up method. CONSTITUTION:A heat resistant sheet 3 consisting of carbon fibers is held into the spacing between the graphite crucible 1 and a quartz crucible 2 and the single crystal is pulled up. This heat resistant sheet 3 is composed of a base sheet 3a and a side sheet 3b and is used to cover the inside surface of the graphite crucible 1. As a result, the reaction of the parting surface and inside surface of the graphite crucible 1 to SiC and the consequent deformation of the crucible are suppressed. In addition, the impurities which are heretofore accumulated on the inside surface of the graphite crucible 1 are accumulated on the heat resistant sheet 3. Then, the thickness decrease on the inside surface of the graphite crucible 1 is suppressed by exchanging the heat resistant sheet 3 at the every time of putting up the single crystalline by one to several times and the amt. of the impurities accumulated on the inside surface is greatly decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor single crystal.

[0002]

2. Description of the Related Art As one of the methods for producing a silicon single crystal which is a basic material of a semiconductor integrated circuit, a pulling method for pulling a cylindrical single crystal from a raw material melt in a crucible is used. In the pulling method, a quartz crucible housed in a graphite crucible is filled with high-purity polycrystalline silicon, and the polycrystalline silicon is heated and melted by a graphite heater provided so as to surround the outer periphery of the graphite crucible, and then a seed chuck. The seed crystal attached to the above is immersed in the melt, and the seed chuck is pulled up while rotating the seed chuck and the graphite crucible in the same direction or opposite directions to grow a silicon single crystal.

[0003]

When a silicon single crystal is grown by the pulling method, the graphite crucible and the quartz crucible cause a chemical reaction as shown by the following formula, and the graphite crucible becomes SiC. C + SiO ₂ → SiO + CO 2C + SiO → SiC + CO Generally, the graphite crucible is divided into 2 or 3 parts.
When the dividing surface is made of SiC, the gap between the mating surfaces gradually increases, and the graphite crucible deforms. Along with this, the quartz crucible accommodated in the graphite crucible is also deformed and the melt surface position is changed, and the temperature in the vicinity of the division surface of the graphite crucible is lowered, so that the temperature distribution of the melt is changed. The growth of the single crystal during pulling is hindered. Also, the thermal history of the single crystal changes. In order to prevent such problems from occurring, measure the amount of deformation of the graphite crucible each time the pulling of the single crystal is completed, and if the opening amount of the mating surfaces exceeds the specified value, replace the graphite crucible with a new one. There is. Even when the deformation amount of the graphite crucible does not exceed the predetermined value, the amount of impurities such as calcium and sodium accumulated on the inner surface of the graphite crucible increases with each use, and oxygen-induced stacking in the single crystal occurs. This increases the frequency of occurrence of defects (also referred to as OSF).

As described above, as the number of times the graphite crucible is used increases, single crystallization is hindered, and oxygen-induced stacking faults in the single crystal are more likely to occur. As a result, the number of times the graphite crucible is used is limited. Incurs high costs. The present invention has been made by focusing on the above-mentioned conventional problems. It is intended to improve the single crystallization rate, reduce the occurrence rate of oxygen-induced stacking faults in the single crystal, and extend the service life of the graphite crucible. It is an object of the present invention to provide a method for producing a semiconductor single crystal capable of performing the above.

[0005]

In order to achieve the above object, a method for producing a semiconductor single crystal according to the present invention includes a crucible for storing a raw material melt and a crucible for accommodating the crucible in the production of the semiconductor single crystal by a pulling method. In the gap with the support to
A heat-resistant sheet that covers the inner surface of the support is sandwiched, and in such a configuration, the heat-resistant sheet is made of carbon fiber.

[0006]

According to the above construction, a heat-resistant sheet of carbon fiber is sandwiched between the crucible for storing the raw material melt, that is, the quartz crucible and the support for accommodating the quartz crucible, that is, the graphite crucible. Since the pulling-up is performed, the graphite crucible does not directly contact the quartz crucible due to the interposition of the heat-resistant sheet, so that the dividing surface and the inner surface of the graphite crucible are prevented from becoming SiC. Further, conventionally, impurities accumulated on the inner surface of the graphite crucible are accumulated on the heat-resistant sheet by applying the present invention. Therefore, the heat-resistant sheet should be replaced every time the single crystal is pulled once or several times. Thus, the amount of impurities accumulated in the graphite crucible can be significantly reduced.

[0007]

EXAMPLES Examples of the method for producing a semiconductor single crystal according to the present invention will be described below with reference to the drawings. Figure 1
1 is a schematic cross-sectional view of a graphite crucible according to a first embodiment and a quartz crucible housed in the graphite crucible. A heat resistant sheet 3 is sandwiched between the graphite crucible 1 and the quartz crucible 2 over the entire surface. The heat resistant sheet 3 is made of carbon fiber and has a thickness of 3 mm or less. In this example, a sheet having a thickness of 0.4 mm was used. The heat resistant sheet 3 is a graphite crucible 1.
Bottom sheet 3a for covering the bottom of the inner surface of the graphite crucible 1
And a side surface sheet 3b that covers the inner peripheral surface other than the bottom portion. The bottom sheet 3a is obtained by cutting a heat-resistant sheet into a circular shape as shown in FIG. 2 and making radial cuts so that the bottom portion of the inner surface of the graphite crucible 1 does not have a gap and the overlapping portions of the sheets do not occur. . Side sheet 3
As shown in FIG. 3, b is a heat-resistant sheet cut into a rectangle, and covers the inner peripheral surface of the graphite crucible 1 excluding the bottom. The inner surface of the graphite crucible 1 is covered with these sheets 3a and 3b without any gap. The bottom sheet 3a and the side sheet 3b may be integrally cut.

The heat-resistant sheet 3 is sandwiched between a graphite crucible 1 and a quartz crucible 2, and a silicon polycrystal as a raw material is filled in the quartz crucible 2 and heated and melted to pull up a silicon single crystal. Since the heat-resistant sheet 3 is in contact with the quartz crucible 2, the heat-resistant sheet 3 becomes SiC and impurities are accumulated in place of the graphite crucible 1. Therefore, after performing the pulling operation once or several times, the heat resistant sheet 3
Must be replaced with a new one. By using the heat-resistant sheet 3, it is possible to prevent the dividing surface and the inner surface of the graphite crucible 1 from being made of SiC, thinning, and contamination, and the life of the graphite crucible can be reduced to 2 times that of the conventional one.
Could be more than doubled.

FIGS. 4 to 6 show an example of a quantitative change of impurities accumulated on the inner and outer surfaces of the graphite crucible in the present embodiment. To compare with this, the graphite crucible of the conventional single crystal manufacturing method is compared. An example of the impurity accumulation state is shown in FIGS.
Shown in. In these figures, the solid line indicates changes in the amount of impurities accumulated on the inner surface of the graphite crucible, and the dotted line indicates changes in the amount of impurities accumulated on the outer surface of the graphite crucible. 4 and 9 are potassium and FIG.
And FIG. 10 shows the accumulated amount of calcium, and FIGS. 6 and 11 show the accumulated amount of sodium. In the conventional method for producing a single crystal, the accumulated amount on the inner surface of the graphite crucible increases in proportion to the number of times the graphite crucible is used. However, in the case of this example, each element hardly increased, and the effect of using the heat-resistant sheet was exhibited.

FIG. 7 is a diagram showing the relationship between the number of times the graphite crucible is used and the oxygen-induced stacking fault occurrence rate in a single crystal. Data based on this example is shown by a solid line, and a conventional single crystal manufacturing method is used. The data are indicated by dotted lines. As can be seen from this figure, by covering the inner surface of the graphite crucible with a heat-resistant sheet to reduce the amount of impurities accumulated on the inner surface of the graphite crucible, the generation of oxygen-induced stacking faults in the single crystal could be halved.

In the second embodiment, a heat-resistant sheet molded to fit the inner shape of the graphite crucible is prepared and sandwiched in the gap between the graphite crucible and the quartz crucible. It can be done easily. Further, FIG. 8 is a schematic cross-sectional view in the case where only the bottom surface of the graphite crucible 1 is covered with a heat resistant sheet as a third embodiment. In this case, the graphite crucible 1 using the bottom sheet 3a shown in FIG.
It is sufficient to cover the bottom surface of the. In addition to these, heat-resistant spacers cut into an appropriate size to fit the shape of the inner surface of the graphite crucible may be spread on the inner surface of the graphite crucible so that there are no gaps and no overlapping portions.

[0012]

As described above, according to the present invention, a sheet made of carbon fiber is provided in the gap between the graphite crucible and the quartz crucible as a means for suppressing the formation of SiC on the inner surface or divided surface of the graphite crucible or the accumulation of impurities. Since it was decided to pull up the single crystal with the interposition of, the deformation of the graphite crucible and the accumulation of impurities, which were conventionally caused by the contact with the quartz crucible, were significantly reduced, and the single crystallization rate was improved accordingly. Also, the oxygen-induced stacking fault occurrence rate can be halved. Also,
By suppressing the contamination and deterioration of the graphite crucible, it is possible to extend the service life of the graphite crucible more than twice as long as the conventional one, and it is possible to contribute to the reduction of the single crystal production cost by combining these.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a graphite crucible and a quartz crucible sandwiching a heat resistant sheet.

FIG. 2 is a plan view of a bottom sheet.

FIG. 3 is a plan view of a side sheet.

FIG. 4 is a diagram showing a quantitative change of potassium accumulated on the inner and outer surfaces of a graphite crucible when a heat resistant sheet is used.

FIG. 5 is a diagram showing a quantitative change of calcium accumulated on the inner and outer surfaces of a graphite crucible when a heat resistant sheet is used.

FIG. 6 is a diagram showing a quantitative change of sodium accumulated on the inner and outer surfaces of a graphite crucible when a heat resistant sheet is used.

FIG. 7 is a diagram showing the relationship between the number of times a graphite crucible is used and the oxygen-induced stacking fault occurrence rate in a single crystal.

FIG. 8 is a schematic cross-sectional view of a graphite crucible and a quartz crucible in which a heat resistant sheet is sandwiched only on the bottom surface.

FIG. 9 is a diagram showing a quantitative change of potassium accumulated on the inner and outer surfaces of a graphite crucible in a conventional method for producing a single crystal.

FIG. 10 is a diagram showing a quantitative change of calcium accumulated on the inner and outer surfaces of a graphite crucible in a conventional method for producing a single crystal.

FIG. 11 is a diagram showing a quantitative change of sodium accumulated on the inner and outer surfaces of a graphite crucible in a conventional method for producing a single crystal.

[Explanation of symbols]

 1 Graphite crucible 2 Quartz crucible 3 Heat resistant sheet 3a Bottom sheet 3b Side sheet

Claims (2)

[Claims] 1. In the production of a semiconductor single crystal by the pulling method, a heat-resistant sheet for covering the inner surface of the support is sandwiched in a gap between a crucible for storing a raw material melt and a support for accommodating the crucible. A method for manufacturing a semiconductor single crystal, comprising: 2. The method for producing a semiconductor single crystal according to claim 1, wherein the heat resistant sheet is made of carbon fiber.