JP2005343774A - Quartz glass crucible for pulling silicon single crystal and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a quartz glass crucible for pulling a silicon single crystal where the variation of oxygen content and aluminum content in the silicon single crystal can be made as little as possible, the occurrence of vibration on the surface of a molten silicon liquid can be suppressed without increasing the content of an OH group in a transparent layer consisting of synthetic quartz glass and the generation of surface roughness, inner layer separation and cristobalite spots at the inner surface of the crucible is little in a long term operation and to provide its manufacturing method. <P>SOLUTION: The quartz glass crucible has an opaque outer layer formed with molten natural silica powders and the transparent layer having a thickness of 0.4-5 mm and consisting of natural quartz glass formed inside. The quartz glass crucible for pulling the silicon single crystal characterized in that the transparent layer consisting of the synthetic quartz glass containing aluminum of 1-20 ppm is formed inside in the range of at least 0.15-0.55L wherein L is a distance from the bottom center of the inner surface of the quartz glass crucible to the upper edge surface along the inner surface of the crucible and its manufacturing method are provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a quartz glass crucible for pulling a silicon single crystal and a method for manufacturing the same.

  Conventionally, a so-called Czochralski method (CZ method) has been widely used for the production of silicon single crystals. In this CZ method, a silicon polycrystal is melted in a crucible made of quartz glass, a silicon single crystal seed crystal is immersed in the silicon melt, and the seed crystal is gradually pulled up while rotating the crucible. Is grown using seed crystals as nuclei. The single crystal produced by the CZ method is required to have a high purity and to be able to produce a silicon wafer with a high yield, and the quartz glass crucible used for the production includes a transparent inner layer containing no bubbles and bubbles. A quartz glass crucible having a two-layer structure composed of an opaque outer layer is generally used.

  In recent years, as the diameter of a silicon single crystal is increased, the pulling operation of the single crystal takes a long time, and thus the silica glass crucible has been required to have higher purity. Therefore, the present applicants have proposed a crucible in which the inner layer of a quartz glass crucible having a two-layer structure composed of a transparent inner layer and an opaque outer layer is formed of synthetic silica powder (Patent Document 1). A quartz glass crucible with an inner layer made of synthetic quartz glass has a very low content of impurities, reduces the rough surface of the crucible inner surface and the occurrence of cristobalite spots due to the pulling of the silicon single crystal, and can be operated for a long time. There is an advantage that the yield of crystal pulling can be improved.

  However, when the transparent inner layer is composed of synthetic quartz glass, the physical properties of the transparent inner layer and the outer layer such as the difference between transparent and opaque and the difference between synthetic and natural greatly differ, so distortion occurs at the boundary between the two, In particular, a crucible curved portion having a high heat load due to the heater and a long contact time with the silicon melt sometimes causes problems such as deformation and peeling of the transparent inner layer.

  Further, the crucible whose transparent inner layer is made of synthetic quartz glass has a drawback that the surface of the melt is likely to vibrate when the polysilicon is melted as compared with the crucible made of natural quartz glass. This vibration is often seen in the initial pulling process in the first half of the single crystal body, especially from seeding to shoulder formation, and it takes time for seeding work, and the crystal is disturbed and remelted, causing so-called meltback. There was a case where the property was lowered. Therefore, the present inventors have proposed a crucible having a multilayer structure having an opaque intermediate layer of synthetic quartz glass between a transparent inner layer made of synthetic quartz glass and an opaque bulk layer made of natural quartz glass (Patent Document 2). However, the crucible having a multi-layer structure has a drawback of increasing the price of the quartz glass crucible because it uses a large amount of expensive synthetic quartz powder.

  As a quartz glass crucible for solving the above-mentioned disadvantages, the present inventor formed an opaque outer layer formed by melting natural silica powder and a transparent layer made of natural quartz glass inside, and the quartz glass crucible. For pulling up a silicon single crystal in which a transparent layer made of synthetic quartz glass is formed inside at least 0.15 to 0.55 L with respect to the distance L from the bottom center of the inner surface to the upper end surface along the inner surface of the crucible A quartz glass crucible was proposed (Cited document 3). This silica glass crucible for pulling silicon single crystal suppresses the occurrence of vibration on the surface of the silicon melt, and has advantages such as less rough skin on the inner surface of the crucible, peeling of the inner layer, and occurrence of cristobalite spots even during long-time operation. , Synthetic quartz glass part and natural quartz glass part coexist on the inner surface of the crucible, and they cause a big difference in the amount of penetration into the silicon melt, resulting in variations in oxygen content and aluminum content in the silicon single crystal. was there.

Patent No. 2811290, Patent No. 2933404 JP 2001-348294 A Japanese Patent Application No. 2003-126490

  Therefore, the inventors of the present invention have conducted intensive research to develop a quartz glass crucible with little variation in the oxygen content and aluminum content of the silicon single crystal while taking advantage of the quartz glass crucible of the above cited reference 3, In the quartz glass crucible, by adding 1 to 20 ppm of aluminum to the transparent layer made of synthetic quartz glass, the variation in the oxygen content and aluminum content of the silicon single crystal is reduced, and the OH group content in the inner layer is reduced. The present invention has been completed by finding that the occurrence of vibrations on the surface of the silicon melt can be suppressed without increasing. That is,

  The present invention has little variation in the oxygen content and aluminum content of the silicon single crystal, and can suppress the occurrence of vibration on the surface of the silicon melt without increasing the OH group content in the transparent layer made of synthetic quartz glass. An object of the present invention is to provide a quartz glass crucible for pulling up a silicon single crystal that is less likely to cause rough skin on the inner surface of the crucible, peeling of the inner layer, and occurrence of cristobalite spots even during long-time operation.

  Another object of the present invention is to provide a method capable of producing a quartz glass crucible for pulling a silicon single crystal having the above-described excellent characteristics at a low cost.

  In order to achieve the above object, the present invention provides a quartz glass crucible having an opaque outer layer formed by melting natural silica powder and a transparent layer having a thickness of 0.4 to 5 mm made of natural quartz glass formed inside thereof. , Synthetic quartz containing 1-20 ppm of aluminum inside the range of at least 0.15-0.55 L with respect to the distance L from the center of the inner surface of the quartz glass crucible to the upper end surface along the inner surface of the crucible The present invention relates to a quartz glass crucible for pulling up a silicon single crystal characterized by forming a transparent layer made of glass and a method for producing the same.

  As described above, the quartz glass crucible of the present invention is a crucible used when pulling up a silicon single crystal, but the yield of pulling a silicon single crystal depends on the transition of the single crystal, and most of it is in the latter half of the pulling process. In other words, the contact time with the silicon melt is long, and the heat load from the heater is also large, from the curved portion to the bottom of the quartz glass crucible (distance from the bottom center of the inner surface of the crucible to the top surface along the inner surface This is due to rough skin on the inner surface and peeling of the inner layer that occur in a range of at least 0.15 to 0.55 L relative to L). Therefore, in the quartz glass crucible of the present invention, a composition containing at least 0.15 to 0.55 L of aluminum with respect to the distance L to the upper end surface along the inner surface of the crucible, preferably containing 3 to 10 ppm of aluminum. A transparent layer made of quartz glass is formed. By forming a transparent layer made of synthetic quartz glass containing this aluminum, roughening of the inner surface, peeling of the inner layer, generation of cristobalite spots are reduced, and the crystallization rate is increased. In addition, the amount of synthetic quartz powder used is small and the crucible manufacturing cost can be reduced. The thickness of the transparent layer made of synthetic quartz glass containing aluminum is preferably in the range of 0.2 to 1.5 mm, and when the thickness is less than 0.2 mm, there is little effect of suppressing the occurrence of rough skin and cristobalite spots, Even if a layer exceeding 1.5 mm is formed, there is no change in the effect of suppressing the occurrence of rough skin and cristobalite spots, and the production cost of the quartz glass crucible is rather increased, which is not preferable. L is a value measured along the inner surface from the one-dot chain line in FIG. 1 to the upper end surface of the crucible.

  Furthermore, the quartz glass crucible of the present invention is a composition containing aluminum in the range of 0.6 to 1.0 L with respect to the distance (L) from the center of the bottom of the inner surface of the crucible to the upper end surface along the inner surface of the crucible. A transparent layer made of quartz glass is not formed, or even if it is formed, the thickness is preferably 0.2 mm or less. By forming a transparent layer made of natural quartz glass instead of synthetic quartz glass on the inner surface within the above range, vibration of the silicon melt surface can be more effectively suppressed. Further, even if a transparent layer made of synthetic quartz glass containing aluminum is formed, if the thickness is 0.2 mm or less, polysilicon is melted (melted down), and aluminum is added before starting to pull up. The transparent layer made of the synthetic quartz glass contained melts and the natural quartz glass layer is exposed to suppress vibrations on the surface of the silicon melt. In this case, compared with the case where a transparent layer made of synthetic quartz glass containing aluminum is not formed, the amount of natural quartz glass that dissolves into the silicon melt at the time of meltdown is small, so that the impurity melts into the silicon melt less. it can.

  As described above, the quartz glass crucible of the present invention has a synthetic quartz glass portion and a natural quartz glass portion mixed on the inner surface of the crucible, and the aluminum content of the synthetic quartz glass portion is usually less than 0.5 ppm, whereas natural quartz The aluminum content of the glass part is 5-20ppm, which is a big difference in aluminum content, the physical properties are different between the synthetic quartz glass part and the natural quartz glass part, and the boundary between them is distorted. Deformation or peeling occurs in the crucible curved portion having a long contact time with the melt, or there is a difference in the amount of crucible dissolved in the silicon melt, resulting in variations in the oxygen content or aluminum content of the silicon single crystal. In the quartz glass crucible of the present invention, aluminum is contained in the transparent layer made of synthetic quartz glass in an amount of 1 to 20 ppm, preferably 3 to 10 ppm, and the aluminum containing the synthetic quartz glass portion and the natural quartz glass portion. The difference between the two is reduced, the difference in physical properties between the two is reduced, the strain at the boundary is reduced, and the difference in the amount of melting of the crucible is reduced, thereby suppressing variations in oxygen content and aluminum content in the silicon single crystal. is there. Preferably, the difference in aluminum content between the synthetic quartz glass portion and the natural quartz glass portion is 3 ppm or less. If the difference in aluminum content exceeds 3 ppm, the difference in the amount of penetration into the silicon melt increases, which is not preferable. Moreover, generation | occurrence | production of the vibration of the silicon melt surface can be suppressed, without increasing the OH group content of the transparent layer which consists of synthetic quartz glass by containing aluminum of the said range. Silica powder containing aluminum is dried after a method of mixing aluminum powder with silica powder, a method of hydrolyzing, drying, and firing a uniform solution of a silicon compound and an aluminum compound, or by immersing silica powder in a solution of an aluminum compound. However, the method of forming a coating film of an aluminum compound on silica powder or the like is preferable. In particular, a method of hydrolyzing, drying and firing a uniform solution of a silicon compound and an aluminum compound is preferable because it can contain aluminum uniformly.

  In addition to the above, the quartz glass crucible of the present invention is provided with a transparent layer made of natural quartz glass between a transparent layer made of synthetic quartz glass containing aluminum and an opaque outer layer made of natural quartz glass. By providing the transparent layer made of natural quartz glass, distortion at the boundary between the inner layer and the outer layer is relieved, and deformation of the crucible and peeling of the transparent inner layer are further reduced. The transparent layer made of natural quartz glass has a thickness of 0.4 to 5.0 mm, preferably 0.7 to 4.0 mm. When the thickness of the transparent layer made of natural quartz glass is in the above range, the function as the relaxation portion is optimized.

  The quartz glass crucible of the present invention can pull up a silicon single crystal with little variation in oxygen content and aluminum content, and also without increasing the OH group content of the inner layer made of synthetic quartz glass. The generation of vibration can be suppressed. Furthermore, since a transparent layer made of synthetic quartz glass containing aluminum is provided, even during long-time operation, there is little occurrence of rough skin and cristobalite spots, and there is little peeling of the inner layer and deformation of the crucible. Moreover, the quartz glass crucible of the present invention can reduce the production cost of the crucible because the amount of expensive synthetic quartz powder used is small.

  The structure of the quartz glass crucible of the present invention is shown in FIG. 1 is a quartz glass crucible, 2 is the bottom of the crucible, 3 is a straight body, 4 is an opaque outer layer made of natural quartz glass, 5 is a transparent layer made of natural quartz glass, and 6 is a synthetic quartz glass containing aluminum. The transparent layer 7 is a curved portion. Moreover, the aspect of the apparatus which manufactures a quartz glass crucible is shown in FIG. In FIG. 2, 8 is a rotating mold, 9 is a crucible-shaped molded body, 10 and 15 are silica powder supply means, 11 is a plate-shaped lid, 12 is a flow control valve, 13 is a power source, 14 is an arc electrode, 16 Is a high temperature atmosphere. In the quartz glass crucible of the present invention, natural silica powder is introduced into a rotating mold 8 and formed into a crucible shape, and then an arc electrode 14 is inserted therein, and the opening of the crucible-shaped formed body is formed into a plate-shaped lid. 11 and the arc cavity 14 makes the inner cavity of the crucible-shaped body a high-temperature gas atmosphere, and at least partially melts and vitrifies to form an opaque outer layer 4, and then after or during the formation of the outer layer 4, silica A high-purity natural silica powder is supplied to the high-temperature atmosphere 16 while adjusting the supply amount from the powder supply means 10 with the flow rate regulating valve 12, and is formed into a molten glass to form the transparent layer 5 made of natural quartz glass. Further, a synthetic silica powder containing aluminum in the range of 1 to 20 ppm, preferably 3 to 10 ppm, is supplied from the silica powder supply means 15 to the high temperature atmosphere 16 to form a transparent layer made of synthetic quartz glass containing aluminum by melting into glass. Produced by forming a thickness of 0.2 to 1.5 mm in a range of at least 0.15 to 0.55 L with respect to the height (L) from the center of the bottom of the inner surface of the crucible to the upper end surface along the inner surface of the crucible. Is done.

  EXAMPLES The present invention will be described more specifically with reference to the following examples, but the present invention is not limited thereto. In addition, the average OH group content in the present invention is the D.I. M.M. DODD and D.D. B. FRASER, Optical determination of OH in fused silica, Journal of Applied Physics, vol. 37 (1966) p. It is a value measured by the measuring method described in 3911, and the aluminum content is a value measured by ICP emission spectroscopic analysis.

Using the apparatus shown in FIG. 2, high-purity natural silica powder (aluminum content: 12 ppm) is put into a rotating mold 8 and formed into a crucible shaped body 9 by centrifugal force. 14 was inserted, the opening was covered with a plate-like lid 11, and the inside of the internal cavity was made into a high-temperature gas atmosphere by the arc electrode 14, and the glass was melted into glass and cooled to produce an opaque outer layer 4 having a thickness of 8 to 10 mm. . Next, the inner cavity of the opaque outer layer 4 is made high temperature atmosphere 16 with the arc electrode 14 while rotating the mold 8, and then natural silica powder (aluminum content 6 ppm) is supplied from the silica powder supply nozzle 15 at 100 g / min. A transparent layer 5 made of natural quartz glass having a thickness of 0.9 to 2 mm was integrated with the inner surface of 4. Next, synthetic silica powder containing 3 ppm of aluminum is supplied at 100 g / min from the silica powder supply nozzle 15, and the distance (L) from the center of the bottom of the transparent layer made of natural quartz glass to the upper end along the crucible inner surface The transparent layer 6 made of synthetic quartz glass containing 3 ppm of aluminum from 0 to 0.55 L to 0.5 to 1.2 mm in thickness and 0.25 to 0.55 to 0.6 L in thickness. It was fused and integrated to a thickness of 0.1 to 0.2 mm and a thickness of 0.1 to 0.2 mm. The difference in aluminum content between the transparent layer made of natural quartz glass and the transparent layer made of synthetic quartz glass containing aluminum was 3 ppm. The obtained quartz glass crucible has a diameter of 24 inches, the average OH group content C _C of the opaque outer layer 4 made of natural quartz glass is 40 ppm, and the average OH group content C _B of the transparent layer 5 made of natural quartz glass is 70 ppm. , the average OH group content _{C a} of the transparent layer 6 made of synthetic quartz glass containing aluminum was 90 ppm. When this quartz glass crucible was filled with polycrystalline silicon, melted, and the single crystal was pulled up 5 times by the CZ method, no vibration was observed on the surface of the silicon melt, and the obtained silicon single crystal was obtained. The average single crystallization rate was as high as 94%. The results are shown in Table 1.

As in Example 1, using the apparatus shown in FIG. 2, high-purity natural silica powder (aluminum content: 8 ppm) was put into a rotating mold 8 and formed into a crucible-shaped molded body 9 by centrifugal force. Then, the arc electrode 14 is inserted therein, the opening is covered with a plate-like lid body 11, the inside cavity is made into a high-temperature gas atmosphere by the arc electrode 14, melted into glass, cooled, and the thickness is 8 to 10 mm. An opaque outer layer 4 was prepared. Next, the inner cavity of the opaque outer layer 4 is changed to a high temperature atmosphere 16 by the arc electrode 14 while the mold 8 is rotated, and then natural silica powder (aluminum content 7 ppm) is supplied from the silica powder supply nozzle 15 at 100 g / min. A transparent layer 5 made of natural quartz glass having a thickness of 0.9 to 2 mm was integrated with the inner surface of 4. Next, synthetic silica powder containing 7 ppm of aluminum is supplied at 100 g / min from the silica powder supply nozzle 15, and the distance (L) from the center of the bottom of the transparent layer made of natural quartz glass to the upper end along the crucible inner surface The transparent layer 6 made of synthetic quartz glass containing 7 ppm of aluminum from 0 to 0.55 L with respect to 0 to 0.55 L to a thickness of 0.3 to 0.8 mm, and 0.55 to 0.6 L with a thickness of 0 to 0 The transparent layer made of synthetic quartz glass was not formed in 0.6 to 1 L. The difference in aluminum content between the transparent layer made of natural quartz glass and the transparent layer made of synthetic quartz glass containing aluminum was 0 ppm. The obtained quartz glass crucible has a diameter of 24 inches, the average OH group content C _C of the opaque outer layer 4 made of natural quartz glass is 40 ppm, and the average OH group content C _B of the transparent layer 5 made of natural quartz glass is 80 ppm. , the average OH group content _{C a} of the transparent layer 6 made of synthetic quartz glass containing aluminum was 150 ppm. When this quartz glass crucible was filled and melted with polycrystalline silicon and the single crystal was pulled up five times by the CZ method, no vibration on the surface of the silicon melt was observed at all. Moreover, although the natural quartz glass part and the synthetic quartz glass part were mixed on the inner surface of the quartz glass crucible, there was no variation in the oxygen content and the aluminum content in the silicon single crystal. The average single crystallization rate of the obtained silicon single crystal was as high as 92%. The results are shown in Table 1.
(Comparative Example 1)

In Example 1, a 24-inch quartz glass crucible was produced in the same manner as in Example 1 except that synthetic silica powder having an aluminum content of less than 0.1 ppm was used. The difference in aluminum content between the transparent layer made of natural quartz glass and the transparent layer made of synthetic quartz glass was 6 ppm. The obtained quartz glass crucible has a diameter of 24 inches, the average OH group content C _C of the opaque outer layer 4 made of natural quartz glass is 40 ppm, and the average OH group content C _B of the transparent layer 5 made of natural quartz glass is 70 ppm. , the average OH group content _{C a} of the transparent layer 6 made of a synthetic quartz glass was 90 ppm. Using this quartz glass crucible, polycrystalline silicon was filled and melted, and the single crystal was pulled five times by the CZ method. In any case, some vibrations on the melt surface were observed at the initial stage of pulling the silicon single crystal, there was some time loss, and the average single crystallization rate was as low as 88%. Further, since the entire inner surface is a transparent layer made of synthetic quartz glass, there was no variation in the oxygen content in the silicon single crystal. The results are shown in Table 1.
(Comparative Example 2)

In Example 2, a 24-inch quartz glass crucible was manufactured in the same manner as in Example 1 except that synthetic silica powder having an aluminum content of less than 0.1 ppm was used. The difference in aluminum content between the transparent layer made of natural quartz glass and the transparent layer made of synthetic quartz glass was 7 ppm. The obtained quartz glass crucible has a diameter of 24 inches, the average OH group content C _C of the opaque outer layer 4 made of natural quartz glass is 40 ppm, and the average OH group content C _B of the transparent layer 5 made of natural quartz glass is 80 ppm. , the average OH group content _{C a} of the transparent layer 6 made of a synthetic quartz glass was 150 ppm. The quartz glass crucible was used to fill and melt polycrystalline silicon, and the single crystal was pulled up 5 times by the CZ method. In any case, there was no vibration of the melt surface at the time of pulling up the silicon single crystal, and the average single crystallization rate was as high as 92%. However, the variation in oxygen content in the silicon single crystal was found in Example 2. It was a little more compared. The results are shown in Table 1.
(Table 1)

Melt surface vibration (surface vibration):
◎ Nothing at all
○ Without
△ is slightly

  The present invention suppresses the occurrence of vibrations on the surface of the silicon melt without increasing the OH group content in the transparent layer made of synthetic quartz glass with little variation in the oxygen content and aluminum content in the silicon single crystal. This is a quartz glass crucible that can raise the silicon single crystal at a high crystallization rate with little roughening of the inner surface of the crucible, exfoliation of the inner layer, and occurrence of cristobalite spots even during long-time operation. Useful in the field.

It is a schematic sectional drawing of the quartz glass crucible of this invention. The schematic of the manufacturing apparatus for manufacturing the said quartz glass crucible is shown.

Explanation of symbols

1: Silica glass crucible 2: Bottom part 3: Straight body part 4: Opaque outer layer made of natural quartz glass 5: Transparent layer made of natural quartz glass 6: Transparent layer made of synthetic quartz glass containing aluminum 7: Curved part 8: Rotating mold 9: Crucible shaped body 10, 15: Silica powder supply means 11: Plate-shaped lid 12: Flow rate regulating valve 13: Power supply 14: Arc electrode 16: High temperature atmosphere

Claims (7)

In a quartz glass crucible having an opaque outer layer formed by melting natural silica powder and a transparent layer made of natural quartz glass having a thickness of 0.4 to 5 mm formed inside thereof, the center of the bottom of the inner surface of the quartz glass crucible And forming a transparent layer made of synthetic quartz glass containing 1 to 20 ppm of aluminum inside the range of at least 0.15 to 0.55 L with respect to the distance L to the upper end surface along the inner surface of the crucible. A quartz glass crucible for pulling silicon single crystals. 2. The quartz glass crucible for pulling a silicon single crystal according to claim 1, wherein the aluminum content is 3 to 10 ppm. 3. The quartz glass crucible for pulling up a silicon single crystal according to claim 1, wherein the difference in the aluminum content between the transparent layer made of natural quartz glass and the transparent layer made of synthetic quartz glass is 3 ppm or less. The quartz glass crucible for pulling a silicon single crystal according to any one of claims 1 to 3, wherein the thickness of the transparent layer made of synthetic quartz glass containing aluminum is 0.2 to 1.5 mm. The inner surface in the range of 0.6 to 1.0 L with respect to the distance L from the bottom center of the inner surface of the quartz glass crucible to the upper end surface along the inner surface is a transparent layer made of natural quartz glass. The quartz glass crucible for pulling up a silicon single crystal according to any one of claims 1 to 4. Synthetic quartz containing aluminum having a thickness of 0.2 mm or less on the inner surface in the range of 0.6 to 1.0 L with respect to the distance L from the center of the inner surface of the quartz glass crucible to the upper end surface along the inner surface The quartz glass crucible for pulling up a silicon single crystal according to any one of claims 1 to 5, wherein a transparent layer made of glass is formed. The internal cavity of the quartz glass crucible base mounted on the rotating mold is brought to a high temperature atmosphere, partially melted to form an opaque outer layer, or during molding, natural silica powder is supplied into the high temperature atmosphere of the outer layer and melted A transparent layer made of natural quartz glass is formed on the entire inner surface of the opaque outer layer by vitrification, and then a synthetic silica powder containing 1 to 20 ppm of aluminum is supplied to melt glass to form a transparent layer made of the natural quartz glass. A transparent layer made of synthetic quartz glass containing aluminum inside at least 0.15 to 0.55 L with respect to the distance L from the center of the bottom of the inner surface of the quartz glass crucible to the upper end surface along the inner surface of the crucible. A method for producing a quartz glass crucible for pulling up a silicon single crystal.