JPH04209790A - Apparatus for pulling up silicon single crystal - Google Patents

Abstract

PURPOSE:To prevent the formation of polycrystalline crystal caused by the splashing of molten liquid of raw material and to improve the yield of acceptable product by dividing the space in a crucible with upper and lower divided partition walls and making the wall thickness of the upper partition wall to be thinner than that of the lower partition wall. CONSTITUTION:A crucible 3 placed in a single crystal pull-up apparatus is divided into an inner chamber and an outer chamber with a cylindrical partition wall placed concentric to the crucible. The cylindrical partition wall is divided into a lower partition wall 4 for holding an inner chamber molten liquid 1 and an upper partition wall 5 placed immediately above the lower partition wall. The wall thickness of the upper partition wall 5 is made to be thinner than that of the lower partition wall 4. Intrusion of raw material splash generated in the charging and melting of silicon raw material into the inner chamber acting as a pull-up chamber can be prevented by the above construction to completely eliminate the trouble of the formation of polycrystalline crystal on the pulled-up crystal.

Description

[Detailed description of the invention]

[00011

[Industrial Application Field] The present invention relates to a silicon single crystal pulling device using a double structure crucible.
Or it is used for repeated lifting. [0002] [0002] Conventionally, a technique for pulling a single crystal while continuously charging and melting a silicon raw material into a quartz crucible has been proposed as a method for improving productivity and reducing costs for pulling silicon single crystals. (For example, Japanese Patent Application Laid-Open No. 1986-
No. 88896, JP-A-57-183392, JP-A-5
8-36,997, JP-A-62-278188, JP-A-63-319287, JP-A-1-294589, JP-A-2-83292, etc.). [0003] A conventional example of such a single crystal pulling apparatus will be explained with reference to FIG. The quartz crucible 3 stores an inner raw material melt 1 and an outer raw material melt 2, which are separated by a cylindrical partition wall 14 provided inside. The granular silicon raw material 8 is introduced into the outer chamber through the raw material input pipe 9 and melted, and while being supplied into the inner chamber through the opening 6 provided in the partition wall 14,
A silicon single crystal 10 is continuously pulled up from an internal raw material melt 1. The crucible 3 is set in a carbon crucible 7 and supported by a crucible shaft 13 so as to be movable up and down and rotatable. The single crystal 10 is held by a pulling wire 12,
It is pulled up while rotating. 11 is a seed chuck. [0004] In the above-mentioned conventional technique in which a single crystal is pulled up while charging and melting a silicon raw material, a granular polycrystalline silicon raw material produced by a fluidized bed method is widely used as the input raw material. [0005] This raw material contains 1 to 25 ppp due to its manufacturing method.
bw% of hydrogen (see Rare Metal News, No. 1528, January 1990, ps), which ruptures when the raw material is melted and heated, causing splashing of the silicon melt and polluting the inside of the furnace. It attaches to the crystal interface that is being pulled up. [0006] This causes a serious problem in that the pulled crystal becomes polycrystallized, and the yield of good quality products (weight of non-defective product/weight of charge) decreases to, for example, about 40%. Even when a low hydrogen silicon raw material with a hydrogen content of about 1 ppbw% (10-9w%) is actually used, polycrystallization of the pulled single crystal due to the above-mentioned melt splashing sometimes occurs. For example, under normal single crystal pulling conditions, approximately 1
The melt splash phenomenon occurs about once per hour. [0007] Without devising a pulling device, it is far from practical use of a method for pulling a single crystal while charging and melting a silicon raw material. [0008]

Problems to be Solved by the Invention In the conventional pulling device that pulls up a single crystal while charging a granular silicon raw material into a crucible and melting it, as described above (2) There is a problem in that the splashing phenomenon of the liquid occurs, which causes polycrystallization of the pulled crystal and reduces the yield of good products. An object of the present invention is to provide a silicon single crystal pulling device that can eliminate polycrystallization of pulled crystals caused by splashing of melt and improve the yield of good quality pulled crystals. ] The present invention provides a cylindrical partition wall in a crucible for storing a silicon raw material melt in order to divide the inside of the crucible into an inner chamber and an outer chamber, and an opening in the partition wall through which the raw material melt can move. In the apparatus for pulling silicon single crystals from a melt in an inner chamber while introducing and melting a silicon raw material into an outer chamber, the cylindrical partition wall is arranged to overlap a lower partition wall for storing the raw material melt and an upper part of the lower partition wall. pulling of a silicon single crystal characterized in that the upper partition wall is divided into at least one upper partition wall (also referred to as a melt splash prevention partition wall), and the thickness of the upper partition wall is thinner than the thickness of the lower partition wall. [00111] [Operation] In the pulling device of the present invention, the height of the cylindrical partition wall is determined by the height of the stored silicon raw material melt surface (the melt surface of the outer chamber and inner chamber of the crucible). The height of the partition wall was made sufficiently higher than the height of the partition wall (the height of the partition wall is almost the same) to prevent splashing of the melt from entering the inner chamber which is the crystal pulling chamber. Then, due to its own weight, the lower region of the partition wall becomes noticeably softened and deformed, and the problem arises that the opening or pipe-like passage (see Japanese Patent Application Laid-open No. 79790/1983), which is the passage for the raw material melt, collapses. In order to prevent this, the cylindrical partition wall was divided into a plurality of parts, the lower partition wall for storing the raw material melt was made thick enough not to deform, and the thickness of the upper partition wall for preventing flying in was made as thin as possible to reduce weight. [0013] In this way, it was possible to prevent polycrystallization of the pulled crystal and softening deformation of the lower partition wall due to splashing of the melt. [001'4] [Example] FIG. 2 is a cross-sectional view of a main part showing an example of the configuration of a single crystal pulling device. The crucible 3 is divided into an inner chamber and an outer chamber by a cylindrical partition wall arranged concentrically, and the melt 1 in the inner chamber and the outer chamber are divided into an inner chamber and an outer chamber. The cylindrical partition wall contains a silicon raw material melt consisting of an inner chamber melt 2. The cylindrical partition wall includes a lower partition wall 4 that accommodates the inner chamber melt 1, and an upper partition wall 5 that is placed over the top of the partition wall 4.
The wall thickness of the upper partition wall 5 (for example, 2 mm) is thinner than the wall thickness of the lower partition wall 4 (for example, 6 mm). Note that in FIG. 1, the same reference numerals as in FIG. 4 indicate the same or corresponding parts, so the explanation will be omitted. [0015] Next, an embodiment of an apparatus having the same configuration as the single crystal pulling apparatus shown in FIG. 1 will be described below. [00161 In FIG. 2, a lower partition wall (quartz ring) 4 with a diameter of 15 inches and a wall thickness of about 6M is arranged concentrically in a quartz crucible 3 with a diameter of 18 inches, and on top of this lower partition wall 4, a ring of 15 inches is placed. Upper partition walls (quartz rings) 5 having a diameter and wall thickness of about 2 mm are placed one on top of the other to form a double structure crucible. An opening 6 with a diameter of approximately 3 mm is formed below the lower partition wall 4 symmetrically with respect to the crucible axis 13.
There are several locations. [0017] Approximately 25 kg of silicon raw material is stored and melted in this quartz crucible 3, and approximately 31 gr of granular silicon raw material 8 is obtained.
A silicon single crystal 10 with a diameter of about 5 inches is poured from the inner chamber melt 1 into the outer chamber melt 2 at a rate of about 1/min.
Pull up at a speed of mm/min. This trial was repeated using the distance H (mm) between the upper end of the quartz crucible 3 and the upper end of the upper partition wall 5 as a parameter, and the yield rate of pulled single crystals was examined. The results are shown in FIG. Note that the distance h1 between the silicon raw material melt surface and the upper end of the lower partition wall 4 is about 20 mm, and the height h2 of the quartz crucible 3 is 350 m. [0018] In FIG. 3, the horizontal axis represents H(in
) is the value when the height of the upper partition wall 5 is changed, and the vertical axis is the pulling single crystal quality rate (crystal quality product/charge amount x 100
%) hail. The results of this first trial reveal the following. [00191 (a) When the height of the upper partition wall 5 is lower than the upper end of the crucible 3, that is, when H (mm) is a negative number, the splash of the melt when the raw materials are introduced and melted jumps into the inner chamber, and the polymorphism of the pulled crystal is A crystallization phenomenon is observed, and the yield rate of pulled single crystals is significantly reduced, becoming almost 0% when H is less than 150 mm. (00201(b) When the height of the upper partition wall 5 is set 50 to 150M higher than the upper end of the crucible 3, the upper partition wall 5 prevents the splashing of the melt from jumping into the inner chamber, and the pulled crystal becomes polycrystallized. is not observed, and the pulled single crystal yield rate is good at about 80%. [00211 (c) Furthermore, the height of the upper partition wall 5 is increased,
When H exceeds 150 mm, the rate of producing good quality pulled single crystals decreases. This is because the temperature environment at the solid-liquid interface for single crystal pulling becomes poor, making it impossible to pull the single crystal. In addition, about 40 kg of crystals were pulled up in this pulling process. [00221 Next, the thickness of the upper partition wall 5 is taken as a parameter,
The deformation of the lower partition wall 4 and the closing of the openings 6 were investigated. This second trial used the pulling apparatus shown in FIG. 2, and the single crystal pulling method and main conditions were the same as the first trial.
The thickness of the lower partition wall 4 is 6M, and the height of the upper partition wall 5 is H=100.
mm, and the wall thickness is 6mm, 4mm, 3mm
, 2mm, and 1mm. For each wall thickness, the deformation of the lower partition wall 4 and the presence or absence of blockage of the opening 6 were examined, and the yield rate of the pulled single crystal was determined. The results are shown in Table 1. [0023]

[Table 1] [0024] From this result, if the thickness of the upper partition wall 5 is thick,
It was found that the forging greatly deformed the lower partition wall 4 and also caused the apertures 6, which were melt passages, to be blocked, making it impossible to pull the single crystal. According to this example, the thickness of the upper partition wall 5 was set to at least about 1/2 or less of the thickness of the lower partition wall 4, and good results were obtained. [0025] In the pulling device of the above embodiment, the cylindrical partition wall is divided into two and the upper partition wall 5 is provided, and the height thereof is made higher than the upper end of the crucible 3 to serve as a partition wall to prevent melt from entering. This technology has completely eliminated polycrystallization of pulled crystals caused by splashing of the raw material melt when silicon raw materials are introduced and melted. [0026] In addition, to deal with the problem of hole blocking caused by the deformation of the cylindrical partition wall or the deformation of the opening that has newly occurred due to the lengthening of the cylindrical partition wall, the cylindrical partition wall is divided into upper and lower halves, and the thickness of the upper partition wall is reduced. This problem was solved by reducing the thickness and weight as much as possible. [0027] With these, the problems of the prior art can be solved, and the rate of single crystal quality of the pulled crystal has been significantly improved from about 40% in the past to more than 80%. [0028]Also, in the method of pulling a plurality of single crystals while charging and melting raw materials, deformation of the cylindrical partition wall is a bottleneck, but a bright prospect has been obtained for this method. Furthermore, the upper partition wall of the present invention can be used repeatedly, and a cost reduction effect is also expected. [0029] In the above embodiment, the cylindrical partition wall has upper and lower parts.
However, if desired, the upper partition wall may be further divided into a plurality of partitions, or the upper partition wall and the lower partition wall may be formed integrally. [00303] [Effect of the invention] As described above, the present invention provides
This eliminates polycrystallization of pulled crystals caused by splashing of the raw material melt when granular silicon raw materials are introduced and melted.
It was possible to provide a silicon single crystal pulling device that can improve the yield of good quality pulled crystals.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of essential parts showing an example of the configuration of a silicon single crystal pulling apparatus of the present invention.

FIG. 2 is a cross-sectional view of essential parts showing an embodiment of the structure of a silicon single crystal pulling apparatus of the present invention.

FIG. 3 is a graph showing the results of a first trial conducted using the lifting device shown in FIG. 2;

FIG. 4 is a sectional view of a main part showing an example of the configuration of a conventional silicon single crystal pulling apparatus.

[Explanation of symbols]

1 Inner chamber silicon raw material melt 2 Outer chamber silicon raw material melt 3 Crucible 4 Lower bulkhead 5 Upper bulkhead 6 Opening 7 Carbon crucible 8 Input raw materials 10 Pulled single crystal

Claims (1)

[Claims] Claim 1: In a crucible containing a silicon raw material melt,
A cylindrical partition wall is provided to divide the inside of the crucible into an inner chamber and an outer chamber, and an opening is provided in the partition wall through which the raw material melt can move, and while the silicon raw material is introduced into the outer chamber and melted, the melt inside the inner chamber is In an apparatus for pulling silicon single crystals from a liquid, the cylindrical partition wall is divided into a lower partition wall that accommodates a raw material melt and at least one upper partition wall that is placed over the upper part of the lower partition wall; A silicon single crystal pulling device characterized in that the thickness of the partition wall is thinner than the thickness of the lower partition wall.