JPH10182278A - Crucible for pulling single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a crucible which prevents earlier run-out of the service life of a crucible made of graphite, etc., to support the crucible on the inner side and obviates the occurrence of the intrusion of impurities into the single crystal to be pulled up, etc., by accumulating the raw materials for the single crystal including a melt in contact with the inner side and including glassy carbon into at least part thereof. SOLUTION: The crucible 1 consisting of the glassy carbon consists of a straight cylindrical part 2 and a bottom 3 inclusive of a round part in the section shape of the crucible 1 and is formed to a specified thickness. A recess 5 is formed on the inner side of the crucible 1 and the silicon melt as a raw material melt or polycrystalline silicon before melting is accumulated into the recess 5 in the state of maintaining contact with the inner sides 2a, 3a. The crucible 1 contains the glassy carbon in at least part thereof. The glassy carbon forming the parts along at least the inside surfaces 2a, 3a has open porosity of <=1% and the content of the metal impurities is <=10ppm. The crucible 1 is obtd. by holding a molding of thermosetting phenol powder in high-purity graphite plates and firing the molding by heating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for producing a single crystal of silicon, gallium arsenide, indium phosphide or the like (hereinafter simply referred to as "single crystal") by pulling the single crystal by the Czochralski method. The present invention relates to a single crystal pulling crucible.

[0002]

2. Description of the Related Art One of the most typical methods for producing single crystals for semiconductors, for example, silicon single crystals for semiconductors (hereinafter simply referred to as "silicon single crystals"), is pulling of silicon single crystals by the Czochralski method. is there. This method is performed using a first crucible that stores polycrystalline silicon inside and a second crucible that fits and supports the first crucible inside. Then, the polycrystalline silicon is melted by a heating element arranged on the outer periphery of the second crucible, and while the silicon seed crystal is immersed in the silicon melt, the second crucible supporting the first crucible is rotated while rotating upward. The single crystal silicon is grown at the lower end of the seed crystal.

The second crucible is made of a carbon material because it can withstand a high-temperature atmosphere and has a certain mechanical strength, and has a long service life. For example, a graphite crucible made of is used. Conventionally, the first crucible is made of quartz (SiO ₂₎ because it is necessary to avoid mixing of impurities in manufacturing a single crystal of silicon (Si) and to reduce costs. ) Has been used.

[0004]

However, it has been found that the use of a quartz crucible for the first crucible shortens the life of the second crucible made of graphite. That is, it was found that the following phenomena occurred between the crucible made of quartz and the crucible made of graphite, causing the crucible made of graphite to be worn out and to have a reduced strength.

As described above, in the process of manufacturing a silicon single crystal, the polycrystalline silicon or silicon melt stored in the first crucible is heated from outside the second crucible made of graphite. As a result, both the first crucible and the second crucible made of quartz are exposed to a high temperature. Under the high-temperature environment, the following reaction occurs between the first crucible and the second crucible. Is generated. SiO ₂ + C → SiO + CO 2C + SiO → SiC + CO

That is, the graphite crucible is depleted so as to supply the carbon C responsible for the above reaction, and the SiC is formed from the inner surface of the graphite crucible by the action of SiO gas on the inside of the graphite crucible in contact with the quartz crucible. Invite. Further, since the SiO gas is transmitted upward from a gap between the quartz crucible and the graphite crucible and leaks to the outside, SiC is also formed in a portion other than the inner surface side of the graphite crucible, such as the outside. And
Every time the production of silicon crystals is repeated, the depletion of the graphite crucible and the conversion to SiC progress.

[0007] Since this SiC is brittle, as the formation of SiC progresses, cracks are apt to occur in the graphite crucible, leading to a decrease in the mechanical strength of the graphite crucible and, together with the depletion of the graphite crucible, to shorten the life of the crucible. . On the other hand, in order to increase the purity of the single crystal to be pulled, it is necessary to prevent impurities from being mixed into the melt from the first crucible storing the single crystal raw material melt inside.

Further, the SiO gas leaked to the outside also acts on peripheral members other than the graphite crucible, so that the peripheral members constituting a single crystal manufacturing apparatus containing carbon are converted into SiC. It is also desirable to prevent this. When a quartz crucible is used for the first crucible,
Each time single crystal pulling is completed, the quartz crucible is crushed and cannot be used for multiple single crystal pulling. However, due to the configuration of the single crystal manufacturing apparatus, it is also desired that the first crucible can be used for pulling the single crystal a plurality of times.

Accordingly, the present invention relates to a crucible used for pulling a single crystal, which stores therein a raw material melt of the single crystal, and prevents a use life of a crucible such as graphite supporting the crucible inside from being shortened. It is another object of the present invention to provide a single crystal pulling crucible that can be used and does not mix impurities into the single crystal to be pulled.

[0010]

According to a first aspect of the present invention, there is provided a single crystal pulling crucible in which a single crystal raw material melt is stored in contact with the inside thereof. This is a single crystal pulling crucible partially including glassy carbon. When performing the production of a single crystal, as described above, using a first crucible that stores the raw material melt of the single crystal inside, and a second crucible that fits and supports the first crucible inside Done. And since a crucible containing a carbon material is used for the second crucible like a graphite crucible, when a quartz crucible is used for the first crucible, as described above, the second crucible is consumed and SiO
The generation of gas causes the second crucible to become SiC, thereby shortening its life. Here, if a crucible formed by containing glassy carbon is used for the first crucible, the second crucible is prevented from being worn out or becoming SiC, so that the life of the second crucible is prevented from being shortened. Can be. Also,
The constituent members of the manufacturing apparatus for manufacturing a single crystal, many of the peripheral members other than the above crucible also include members formed containing carbon, and if the generation of the SiO gas can be prevented, these peripheral members Of SiC can be prevented. The following advantages are also obtained from the quality of the manufactured single crystal. Since the quartz crucible conventionally used as the first crucible has a composition of SiO ₂ , oxygen (O) penetrates into the single crystal, and the produced single crystal has defects due to oxidation-induced stacking faults (OSF). Was occurring. When a crucible formed including glassy carbon is used as the first crucible, generation of such OSF can be prevented. In addition, since glassy carbon can be highly purified, the problem of contamination of the manufactured single crystal with impurities can be avoided. Furthermore, when a crucible molded body containing glassy carbon is formed, its chemical composition is carbon C, so that it does not soften and has a coefficient of thermal expansion with Si, which is a residue of a single crystal pulled up. Is near. Therefore, unlike a quartz crucible having a composition of SiO ₂ , it is not crushed by a Si residue. Therefore, the first crucible can be repeatedly used for pulling the single crystal a plurality of times without being crushed every time the single crystal is pulled up once.

The invention according to claim 2 is characterized in that the glassy carbon forming at least a portion along the inside of the single crystal pulling crucible has an open porosity of 1% or less. This is a crucible for pulling a single crystal. When at least a portion along the inside of the vitreous carbon forming the single crystal pulling crucible is formed to have an open porosity of 1% or less,
The chemical reaction of the single crystal stored inside with the raw material melt can be suppressed, and the transformation of glassy carbon during pulling of the single crystal can be prevented. Thereby, it is possible to suppress a decrease in the number of times that the crucible formed containing glassy carbon can be used repeatedly.

According to a third aspect of the present invention, the glassy carbon forming at least a portion along the inside of the single crystal pulling crucible has a metal impurity content of 10 ppm or less. A single crystal pulling crucible according to claim 2. By forming at least a portion along the inside of the glassy carbon forming the single crystal pulling crucible so that the content of metal impurities is 10 ppm or less, it is possible to prevent impurities from being mixed into the raw material melt.
This can prevent the quality of the single crystal to be pulled from deteriorating.

According to a fourth aspect of the present invention, there is provided a single crystal pulling crucible according to any one of the first to third aspects as a first crucible, and a second crucible for fitting the first crucible inside to support it. An apparatus for producing a single crystal, wherein the second crucible is a crucible made of graphite. When a single crystal manufacturing apparatus is configured by using the crucible made of glassy carbon as the first crucible, even if a crucible made of graphite is used for the second crucible, it is possible to suppress the depletion of the graphite and the formation of SiC. Can prevent the life of the device from being shortened.

The invention according to claim 5 is the crucible for pulling a single crystal according to any one of claims 1 to 3, wherein the single crystal is a silicon single crystal. When a silicon single crystal is manufactured by using the crucible made of the glassy carbon, no impurity is mixed into the raw material melt of silicon stored inside the crucible, and the single crystal of silicon does not deteriorate in the quality of the single crystal. Can be manufactured.

The invention according to claim 6 is the apparatus for producing a single crystal according to claim 4, wherein the single crystal is a silicon single crystal. When a silicon single crystal is manufactured by a single crystal manufacturing apparatus configured using a crucible made of the glassy carbon, impurities are not mixed into a silicon raw material melt stored inside the crucible, and crystal quality is reduced. A single crystal of silicon without deterioration can be manufactured.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a cross-sectional shape of an example of a single crystal pulling crucible 1 according to the present invention. As shown in FIG. 1, the crucible 1 includes a straight body portion 2 and a bottom portion 3 including an R portion, and these components are formed to have a certain thickness.

A depression 5 is formed inside the crucible 1, and a silicon melt as a raw material melt for pulling a single crystal or polycrystalline silicon before being melted is deposited on the inside 2 a,
It can be stored in the depression 5 in contact with 3a. The crucible 1 contains glassy carbon at least in part, but the glassy carbon forming at least a portion along the inner surfaces 2a and 3a is formed so as to have an open porosity of 1% or less. ing. In addition, the glassy carbon forming at least portions along the inner surfaces 2a and 3a has a metal impurity content of 10 ppm or less.

Next, a specific example of a process for manufacturing the crucible 1 will be described below. FIG. 2 shows a mold 11 used for obtaining a crucible-shaped molded body of the crucible 1. The mold 11 includes a pressing member 12 for molding and an outer casing 13.
And is provided. Inside the mold 11, a cavity 1 corresponding to the shape of the crucible 1 to be molded is formed in a state in which the pressing member 12 for molding is set on the outer casing 13.
4 so that the cavity 14 can be filled with a raw material of glassy carbon.

The size and shape of each part of the mold 11 are mainly determined by the relationship with the size and shape of the crucible 1 after molding. For example, the inner diameter r1 of the crucible 1
The size of the corresponding part of the holding member 12 is defined corresponding to the above, the inner diameter of the hollow part of the outer housing 13 is defined corresponding to the outer diameter r2 of the crucible 1, and the height h of the crucible 1 is defined. Thus, the depth of the hollow portion of the outer housing 13 is defined.

Further, during the formation of the crucible-shaped material, the holding member 12 can be detached from the external housing 13 so that gas accumulated in the forming material can be released.

First, as shown in FIG. 3, the temperature Tm of the mold 11 is set at 180 ° C., and as shown at 15, the cavity 14 of the mold 11 is filled with thermosetting phenol resin powder. Then, degassing is performed several times. Next, as shown in FIG. 3, when a pressure of 150 kg / cm ² is applied for 30 minutes, a phenol resin formed body 17 can be obtained.
Then, after the formed body 17 is roughly processed in accordance with the relation with the purpose of the final product, as shown in FIG.
The formed body 17 is cured by heating to 200 ° C. at a heating rate of h.

Next, as shown in FIG. 3, as a sintering step 1, a high purity graphite plate 20 is sandwiched and heated to 300 ° C. to 400 ° C. at a rate of 1 ° C./h.
A fired body 18 is obtained. Next, in the firing step 2, the fired body 1
8 is further fired. As shown in FIG. 3, heating is performed up to 1000 ° C. at a rate of 4 to 5 ° C./h in an inert atmosphere.

Next, in a firing step 3, the fired body 18 is further fired. As shown in FIG.
Heating is performed up to 2000 ° C. at a heating rate of 0 to 15 ° C./h. Next, by passing through the step of purifying the fired body 18 by the purifying step shown in FIG.
A molded article of the crucible 1 made of high-purity glassy carbon can be obtained. According to such a process, as the crucible 1
Bulk density 1.5 g / cm ² , open porosity 1% or less, bending strength about 120 MPa, purity of surface layer exposed to outside air 10 pp
m or less can be manufactured.

Next, a main part of the single crystal manufacturing apparatus used for manufacturing a single crystal by the Czochralski method, in which the crucible 1 is incorporated, will be described. FIG.
FIG. 2 shows a cross-sectional view of a main part of a configuration example of a single crystal manufacturing apparatus. The crucible 1 made of glassy carbon is used as a first crucible, and the crucible 1 is fitted and supported inside a second crucible 7.

The second crucible 7 is made of graphite. The second crucible 7 may be formed of a C / C material or the like other than graphite. On the outer periphery of the second crucible 7,
A heating element (not shown) is arranged, and the polycrystalline silicon initially stored inside the first crucible 1 is melted by heating by the heating element to form a silicon melt 6.

Then, while the silicon seed crystal 8 is immersed in the silicon melt 6, the second crucible 7 supporting the first crucible is rotated by a rotating mechanism (not shown) while being lifted by the pulling device 9 as shown by an arrow 10 in FIG. Then, the single crystal silicon 21 gradually grows at the lower end of the seed crystal 8. In the single crystal manufacturing apparatus shown in FIG. 4, since the first crucible is formed of glassy carbon, it is formed of a material containing carbon such as graphite as in the case of forming the first crucible with quartz. No chemical reaction occurs with the second crucible. Therefore, the second crucible 7 made of graphite or the like may be worn out,
There is no possibility that SiC is caused by generation of O gas.
This can prevent the life of the second crucible 7 from being shortened.

[0027]

EXAMPLE A single crystal was produced by the Czochralski method using the crucible 1 made of glassy carbon according to the present invention, and a service life test was conducted for the number of times the second crucible 7 could be used repeatedly. Was. As a result of comparison with a quartz crucible by this test, the following results were obtained. 1. Example 1 A silicon single crystal was manufactured using a crucible made of glassy carbon as the first crucible and a graphite crucible as the second crucible. As a result, the graphite crucible was set to 45
Could be used times. 2. Example 2 A silicon single crystal was manufactured using a crucible made of glassy carbon as the first crucible and a crucible made of a carbon fiber reinforced carbon composite material as the second crucible. As a result, the crucible made of the carbon fiber reinforced carbon composite material could be used 50 times. 3. Comparative Example 1 A silicon single crystal was manufactured using a crucible made of quartz as the first crucible and a graphite crucible as the second crucible. As a result, the number of times the graphite crucible could be used was 20 times. 4. Comparative Example 2 A silicon single crystal was manufactured using a crucible made of quartz as the first crucible and a crucible made of a carbon fiber reinforced carbon composite material as the second crucible. As a result, the number of times that the crucible made of the carbon fiber reinforced carbon composite material could be used was 30 times.

From the above, it can be confirmed that when a crucible made of glassy carbon is used as a crucible for storing a single crystal raw material melt, it is possible to prevent the life of graphite crucibles supporting the crucible from being shortened. Further, in both Example 1 and Example 2, it was confirmed that the quality of the manufactured Si single crystal did not deteriorate.

[0029]

As described above, the first aspect of the present invention is as follows.
In the described invention, a crucible used for pulling a single crystal is formed including glassy carbon. Therefore, in manufacturing a single crystal, the crucible such as graphite made of a carbon material that is fitted and supported inside the crucible is used. And SiC conversion can be prevented,
This has the effect that the life of a crucible such as graphite can be prevented from being shortened. Further, it is possible to prevent the peripheral members other than the crucible of the single crystal manufacturing apparatus from being converted into SiC, and to prevent the life of the peripheral members from being shortened. In addition to the effect of eliminating so-called OSF defects in the manufactured single crystal,
There is an effect that the deterioration of the quality of the single crystal can be prevented by preventing impurities from being mixed into the single crystal. Further, when a crucible compact is formed containing glassy carbon, there is an effect that such a crucible can be repeatedly used for pulling a single crystal a plurality of times.

According to the second aspect of the present invention, the transformation of glassy carbon during pulling of a single crystal can be prevented, and the number of times that the crucible formed containing glassy carbon can be used repeatedly can be reduced. This has the effect.

According to the third aspect of the present invention, it is possible to reliably prevent metal impurities from being mixed in the single crystal raw material melt and to prevent the quality of the produced single crystal from being degraded. Play.

The invention described in claim 4 has an effect of preventing a crucible made of graphite constituting a single crystal manufacturing apparatus from having a shortened life.

According to a fifth aspect of the present invention, no impurities are mixed into the raw material melt of silicon stored inside the crucible.
There is an effect that a single crystal of silicon without quality deterioration can be manufactured.

The invention described in claim 6 has the same effect as the invention described in claim 5.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a single crystal pulling crucible according to the present invention.

FIG. 2 is a view showing a mold used for manufacturing a crucible.

FIG. 3 is a view showing a manufacturing process of a crucible made of glassy carbon.

FIG. 4 is a view showing an apparatus for manufacturing a single crystal of silicon.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Crucible made of glassy carbon 2 Crucible straight body 3 Crucible bottom 5 Depression inside crucible 6 Silicon melt 7 Graphite crucible 8 Silicon seed crystal 9 Crystal pulling device 10 Crystal pulling 11 Mold 12 Pressing member DESCRIPTION OF SYMBOLS 13 External housing 14 Cavity 15 Filling of resin powder 17 Crucible-shaped formed body 18 Crucible-shaped fired body 20 High-purity graphite plate 21 Growing single crystal

Claims (6)

[Claims] 1. A single crystal pulling crucible for storing a single crystal raw material containing a melt in contact with the inside thereof, wherein the single crystal pulling crucible includes glassy carbon in at least a part thereof. 2. The single crystal pulling crucible according to claim 1, wherein the glassy carbon forming at least a portion along the inside of the single crystal pulling crucible has an open porosity of 1% or less. 3. The single crystal according to claim 1, wherein the glassy carbon forming at least a portion along the inside of the single crystal pulling crucible has a metal impurity content of 10 ppm or less. Crucible for crystal pulling. 4. A single crystal manufacturing apparatus comprising: a single crystal pulling crucible according to claim 1 as a first crucible; and a second crucible that fits and supports the first crucible inside. A single crystal manufacturing apparatus, wherein the second crucible is a crucible made of graphite. 5. The crucible for pulling a single crystal according to claim 1, wherein the single crystal is a silicon single crystal. 6. The single crystal manufacturing apparatus according to claim 4, wherein said single crystal is a silicon single crystal.