JP3136533B2 - Quartz crucible for pulling silicon single crystal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quartz crucible for pulling a silicon single crystal used for pulling a silicon single crystal used for a semiconductor or the like from molten silicon.

[0002]

2. Description of the Related Art Silicon single crystals for semiconductors are:
Conventionally, the raw material polycrystalline silicon was melted at its melting temperature (about 1420
C.) and a silicon single crystal is pulled from a silicon solution, and a quartz glass crucible is used to heat and melt this polycrystalline silicon.

In pulling this single crystal silicon,
It is known that the quality of the above-mentioned quartz crucible greatly affects single crystal silicon. In particular, if bubbles are present near the inner surface of the crucible wall in contact with the silicon melt, the internal bubbles will thermally expand during pulling, causing the inner surface of the crucible to partially exfoliate, and bubbles and exfoliated quartz chips will be mixed into the silicon single crystal. As a result, polycrystallization is performed, and the single crystal crystallization yield (single crystallization ratio) is reduced.

[0004] In order to avoid such inconvenience, a crucible whose wall is made of transparent quartz substantially containing no air bubbles is known. Is very difficult, and the quality of the obtained silicon single crystal is easily affected.Moreover, there is a problem that the strength of the crucible and the manufacturing process are disadvantageous, so that the product price is high. Not.

At present, a quartz crucible 1 generally used
0, as shown in FIG. 2, the inner portion of the crucible wall in contact with the silicon melt is formed of a transparent glass layer 11 substantially containing no bubbles, and the outer portion is formed of an opaque glass layer 12 containing many bubbles. This is a quartz crucible whose appearance is opaque as a whole.

The quartz crucible 10 is conventionally manufactured mainly by a rotary molding method. In a general rotary molding method, a hollow (bowl) -shaped mold having a large number of suction holes for depressurization provided on an inner surface is used, and the inner surface is filled with quartz powder by horizontally rotating the mold, and an arc electrode is formed. The quartz powder layer is heated and melted and vitrified by a heating source such as the above to form a crucible. In this vitrification stage, the air bubbles inside are suctioned and removed by depressurizing the quartz powder layer through the suction holes of the mold, and a quartz glass crucible having a transparent glass layer substantially free of air bubbles inside is obtained. On the other hand, the outer peripheral portion of the crucible does not affect the pulling up even if bubbles are present, but rather an opaque layer with less heat radiation is suitable for obtaining a heat retaining effect during heating, and the opaque layer is more transparent than the transparent layer. Since it has an advantage that a uniform temperature distribution can be obtained for diffusing and transmitting heat, it is formed of an opaque glass layer containing many bubbles.

As described above, in the conventional quartz crucible, the outer peripheral portion is formed of an opaque glass layer containing many bubbles, and the inner peripheral portion is formed of a transparent glass layer containing substantially no bubbles. The thickness of the transparent glass layer and the opaque glass layer is such that the entire crucible is uniformly heated.
Each of the crucibles is formed almost uniformly.

During the pulling of a single crystal, the inner wall of the crucible gradually dissolves in the silicon melt. After the oxygen in the quartz migrates to the silicon melt, most of it diverges from the surface of the melt, but part of the oxygen is taken into the single crystal and becomes a source of oxygen concentration. Therefore, as a method of pulling a silicon single crystal having a high oxygen concentration, the position of the crucible 10 is kept high with respect to the heater 30 as shown in FIG. Part 22
Is locally raised to a high temperature, and the crucible inner surface (transparent layer) 11 at that portion is dissolved more in the silicon melt.

In such a heating operation, in a conventional quartz crucible having a thick opaque layer in order to give priority to the conventional heat retaining property, the entire transparent glass layer of the crucible curved portion melts into the silicon melt during pulling by the heating operation. In addition, there is a problem that the opaque layer is exposed to the silicon melt and the yield of single crystallization is greatly reduced. When the opaque layer is thickened to avoid this, the heat transfer effect of the entire crucible is reduced, and even if the above heating operation is performed, the temperature of the crucible curved portion inner surface is hardly increased, and the amount of melting of the crucible inner surface does not increase so much. A silicon single crystal having a high oxygen concentration cannot be obtained.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a quartz crucible for pulling a silicon single crystal which has solved the above-mentioned problems in the conventional quartz crucible. In view of the above problems, the inventors of the present invention have made the above-described problems by reducing the thickness of the opaque glass layer by increasing the thickness of the transparent glass layer at the curved portion of the crucible in a quartz crucible having an opaque glass layer on the outer wall and a transparent glass layer on the inner wall. Can be solved. The present invention is based on this finding.

[0011]

According to the present invention, there is provided a quartz crucible for pulling a silicon single crystal having the following structure. (1) In a quartz crucible in which an inner surface side portion of a wall is substantially made of a transparent glass layer containing no air bubbles and an outer surface side portion of the wall is made of an opaque glass layer containing air bubbles,
The thickness of the transparent glass layer at the curved portion connecting the peripheral wall portion and the bottom portion of the crucible is 0.1 mm thicker than the transparent glass layer at the other wall portions.
A quartz crucible for pulling a silicon single crystal, wherein the quartz crucible is formed thicker than 5 mm. (2) The quartz crucible according to (1), wherein the thickness of the opaque glass layer in the curved portion is formed to be 0.5 mm or more thicker than the other portions of the opaque glass layer. (3) The thickness of the entire wall including the transparent glass layer and the opaque glass layer is uniform in the entire crucible, the transparent glass layer on the peripheral wall and the bottom is 0.7 to 1.0 mm, and the transparent glass layer on the curved portion is The quartz crucible according to the above (1) or (2), wherein is larger than 1.2 mm.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic sectional view showing an example of pulling a silicon single crystal using a quartz crucible according to the present invention. As shown in the figure, the outer shape of the quartz crucible 10 of the present invention has a bowl-like hollow shape as in the prior art, and is mounted on a carbon crucible 13 for use. A heater 30 is provided outside the carbon crucible, and the heater 30 melts polycrystalline silicon as a raw material charged in the quartz crucible to pull up a silicon single crystal.

The inner surface side portion of the quartz crucible 10 is formed by a transparent glass layer 11 having substantially no air bubbles. Therefore, there is no fear that the inner peripheral surface of the crucible is peeled off due to the expansion of the bubbles at a high temperature, or that the single crystallization is disturbed by the inclusion of the bubbles. On the other hand, the outer surface side portion of the quartz crucible is formed by an opaque glass layer 12 containing many bubbles. Therefore, the heat retention is high and the temperature change in the crucible is suppressed. Here, "contains substantially no bubbles" means that the bubble content is less than 0.3%, and "contains a large number of bubbles" means that the bubble content is 0.3% or more. The bubble content can be represented by the ratio (W2 / W1) of the bubble occupying area (W2) at a constant cross-sectional area (W1) of the quartz crucible.

The transparent glass layer of the curved portion 22 of the quartz crucible 10 is formed to be 0.5 mm or more thicker than the transparent glass layer of the peripheral wall portion 23 and the bottom portion 21. At the time of pulling a single crystal, the transparent glass layer on the inner surface of the crucible wall and the bottom is 0.1 mm.
Usually, the transparent glass layer has a thickness of 0.7 to 5 mm.
It is formed to a thickness of 1.2 mm. Therefore, the thickness of the transparent glass layer in the curved portion is preferably 1.2 mm or more. Since the opaque glass layer and the transparent glass layer are continuously and integrally formed through the peripheral wall portion, the curved portion, and the bottom portion of the crucible, the layer thickness of the portion connected to the peripheral wall portion or the bottom portion on both sides of the curved portion is continuous. Is gradually decreasing or increasing.

In the case where the temperature of the curved portion is locally raised to pull a single crystal having a high oxygen concentration, if the thickness of the transparent glass layer of the curved portion is less than 1.2 mm, the transparent portion of the curved portion is not pulled during the pulling. It is not preferable because the entire glass layer is melted and the opaque layer is exposed to the silicon melt to lower the yield of single crystallization. In this case, the above problem can be prevented by forming a transparent layer having a thickness of 1.2 mm or more over the entire crucible. The crucible inner volume decreases and the crucible cost increases.

Preferably, the opaque glass layer is formed thinner by the thickness of the transparent glass layer in the curved portion than in other portions. By forming the opaque glass layer of the curved portion thinly, heat from the heater is easily transmitted in the curved portion, so that this portion is mainly heated, and the inner surface temperature of the curved portion locally increases, and this portion is heated. Of the transparent glass layer increases, and the oxygen concentration of the silicon single crystal increases. On the other hand, the other portions of the opaque glass layer have a constant thickness, so that the heat retention of the entire crucible is not impaired and the quality of the single crystal is good. In the curved portion, the thickness of the opaque glass layer is reduced by the thickness of the transparent glass layer, so that the thickness of the entire wall including both layers is the same as the other portions, and the thickness of the entire crucible becomes uniform. It is preferred.

The quartz crucible 10 of the present invention is characterized by the curved portion 22 as described above, and the other portions, that is, the thicknesses of the transparent glass layer and the opaque glass layer in the crucible side wall portion 23 and the crucible bottom portion 21, The shape and size of the crucible are not particularly limited, and may take various forms as in the case of the conventional quartz crucible.

The quartz crucible of the present invention can be manufactured by using a known crucible manufacturing method such as a rotary molding method. In particular, the rotary molding method is industrially advantageous because it can be manufactured at low cost. In order to manufacture the quartz crucible of the present invention by a rotary molding method, first, a raw material quartz powder is deposited on the inner peripheral surface, the bottom, and the curved portion of the rotated mold. Then, this is heated and melted by, for example, arc discharge or the like, and the surface of the deposited quartz layer is melted and vitrified, and at the same time, the pressure is reduced from the mold side, and the air inside the quartz layer is sucked out through the vent holes provided in the mold. To form a transparent glass layer substantially free of bubbles. When the transparent glass layer is formed to the desired thickness, the pressure is stopped, and if the melting is further continued, an opaque glass layer is formed outside the transparent glass layer in which air contained between the quartz powder is taken in as bubbles.

As described above, if a transparent glass layer and an opaque glass layer having a uniform thickness are formed and then the inner surface temperature of the crucible is further increased, the viscosity of the transparent glass layer is reduced and the transparent glass layer flows. The transparent glass layer flows toward the lower curved portion due to gravity, and the transparent glass layer at the bottom flows toward the curved portions on both sides due to centrifugal force, so that a thick crucible of the transparent glass layer at the curved portion is obtained. Also, instead of increasing the temperature of the inner surface of the crucible, the transparent glass layer of the curved portion can be formed thicker even if the decompression force of the curved portion is increased as compared with other portions.

On the other hand, except that the transparent glass layer of the curved portion is formed thicker and that the raw material quartz powder of the curved portion is filled thinner than the other portions, the opaque glass at the curved portion is melted by heating in the same manner as in a normal manufacturing method. The layer can be formed thin. According to this method, the inner raw material quartz powder is heated and melted to form a transparent glass layer having a uniform thickness, and the remaining opaque layer is formed thin. Further, by using a mold that can independently adjust the decompression force of the curved portion, and by increasing the decompression of the curved portion more than other portions at the time of decompression, the transparent layer of the curved portion can be made thicker and the opaque layer can be made thinner.

[0021]

EXAMPLES Examples of the present invention will be described below together with comparative examples. Example 1 A quartz crucible of the present invention was produced by a rotary molding method as follows. The particle size of the raw material quartz powder is 1
Those having a size of 00 to 400 μm (center particle diameter 210 μm) were used.
First, a quartz layer having a thickness of 22 mm is deposited on the inner surface of the mold, and then the surface of the quartz layer is melted and vitrified by an arc electrode. The air inside the quartz layer was sucked out through the vent holes to remove bubbles on the surface of the quartz layer to form a transparent glass layer. Thereafter, the decompression was stopped and 10
Heating was continued for a minute to form an opaque glass layer. At this time, the thickness of the transparent glass layer was 0.8 mm, and the thickness of the opaque glass layer was 7.2 mm. Subsequently, the voltage of the arc electrode was increased by 20%.
By increasing the heating temperature and melting for 3 minutes to slightly deform the transparent layer by flowing, a quartz crucible having a thickness of 1.2 mm in the transparent glass layer in the curved portion and a thickness of 0.7 mm in the transparent glass layer in the other portion is obtained. Obtained. The thickness of the opaque glass layer was uniform without any change due to the cooling effect of the mold.

Example 2 The deposition thickness of the raw material quartz powder was set to 21 mm for the curved portion, and
A quartz crucible having each layer thickness shown in Table 1 was obtained in the same manner as in Example 1 except that the thickness was 2 mm.

[0023]

[Table 1]

Embodiment 3 Quartz powder is deposited on the inner surface of a mold in which the depressurizing system of the curved portion and the other portions can be controlled independently.
Arc melting was performed for one minute. The depressurizing force of the curved portion was strengthened by -50 mmHg from the other portions, and the pressure was reduced for the first minute and 20 seconds.
In the other part, a conventional vacuum pressure of -500 mmHg to -700 mmHg was applied for the first minute. As a result, a quartz crucible having each layer thickness shown in Table 2 was obtained.

[0025]

[Table 2]

Comparative Example 1 In Example 1, the transparent glass layer (layer thickness: 0.8 mm) and the opaque glass layer (layer thickness: 7.2 mm) were both uniform without performing a heating operation for flowing and deforming the transparent glass layer. A raw quartz crucible was obtained (an intermediate product in Example 1).

Comparative Example 2 The same operation as in Comparative Example 1 was carried out except that the decompression time was 1 minute and 30 seconds, and both the transparent glass layer (layer thickness: 1.2 mm) and the opaque glass layer (layer thickness: 6.8 mm) were used. A quartz crucible that remained uniform was obtained.

Silicon Single Crystal Pulling Test Using the crucibles obtained in Examples 1 to 3 and Comparative Examples 1 and 2, a silicon single crystal was pulled under the same conditions, and the single crystal yield and oxygen concentration were evaluated. . Table 3 shows the results.

[0029]

[Table 3]

As is clear from Table 3, the crucible of Comparative Example 1 has a thin transparent layer in the curved portion, an opaque layer is exposed during the pulling operation, and the single crystal is polycrystallized, so that the single crystal yield is low. The crucible of Comparative Example 2 has a good yield because the thickness of the transparent layer is large, but the crucible inner surface temperature at the curved portion is hard to increase, so that the crucible is lower than the reference oxygen concentration. On the other hand, the crucibles of the present invention obtained in Examples 1 to 3 have good single crystal yield and oxygen concentration.

[0031]

As described above, in the quartz crucible of the present invention, the transparent glass layer at the curved portion is thicker than the transparent glass layer of the other wall, and the opaque glass layer is formed thinner. It is easy to obtain a high oxygen concentration single crystal, and even in that case, the single crystal yield is high. In addition, the crucible internal temperature is uniform, and the heater temperature of the curved portion may be low.
Also in the production of crucibles, the temperature of the quartz crucible does not unnecessarily increase, and damage to the carbon crucible and the quartz crucible can be suppressed. The effect of the present invention is remarkable in pulling up a large crucible having a high crucible temperature.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a silicon single crystal pulling operation using a quartz crucible according to the present invention.

FIG. 2 is a schematic cross-sectional view of a conventional quartz crucible.

FIG. 3 is a schematic cross-sectional view showing a silicon single crystal pulling operation using a conventional quartz crucible.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Single crystal under pulling, 2 ... Molten silicon, 10 ... Quartz crucible, 11 ... Transparent glass layer, 12 ... Opaque glass layer,
13: carbon crucible, 21: crucible bottom, 22: crucible curved part, 23: crucible peripheral wall, 30: heater.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-221780 (JP, A) JP-A-4-119986 (JP, A) JP-A-59-213697 (JP, A) JP-A-1- 148782 (JP, A) JP-A-1-148783 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C30B 1/00-35/00

Claims (3)

(57) [Claims] 1. A quartz crucible in which an inner surface side portion of a wall is made of a transparent glass layer substantially free of bubbles and an outer surface side portion of the wall is made of an opaque glass layer containing bubbles. A quartz crucible for pulling a silicon single crystal, wherein a thickness of a transparent glass layer in a curved portion connecting a peripheral wall portion and a bottom portion is formed to be 0.5 mm or more thicker than a transparent glass layer of another wall portion. 2. The quartz crucible according to claim 1, wherein the thickness of the opaque glass layer in the curved portion is formed to be thinner than the other portions by 0.5 mm or more. 3. The thickness of the entire wall including the transparent glass layer and the opaque glass layer is uniform in the entire crucible, the transparent glass layers on the peripheral wall and the bottom are 0.7 to 1.0 mm, and the transparent portion on the curved portion is transparent. 2. The quartz crucible according to claim 1, wherein the glass layer has a thickness of 1.2 mm or more.