JPH02172888A - Crucible for pulling up silicon single crystal - Google Patents

Abstract

PURPOSE:To eliminate the disturbance of single crystal growth by bubbles from the bottom of the crucible made of air bubble-contg. silica glass to be used in a CZ method by installing a bluebells silica glass plate which does not generate the bubbles near the m. p. of silicon to the bottom of the inside surface of the crucible. CONSTITUTION:The crucible 1 for pulling up the silicon single crystal by the Czochralski method is produced by a method for melting the powder silica in the rotating crucible, etc. The bubbleless silica glass plate 2 which has the diameter smaller than the bore of the crucible 1 and does not generate the bubbles at about the m. p. of the silicon is then installed by welding, etc., to the bottom of the inside surface of this crucible 1 in which the bubbles are unavoidably intruded. The hindrance of the growth of the single crystal by the infiltration of the bubbles generated from the silica glass to the solid-liquid boundary of the single crystal under pulling up is obviated in this way even if the crucible 1 is used over a long period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a crucible for pulling a silicon single crystal using the Czochralski method.

[Prior Art and Problems to be Solved by the Invention] A silicon single crystal pulling method using the Czochralski method has been practiced for a long time and has become a nearly perfected technology.

In this technology, as is well known, a molten semiconductor raw material is placed in a silica glass crucible, a seed crystal is brought into contact with the molten surface, and at the same time rotated and pulled up gradually. As the contact surface solidifies, crystal growth occurs. A cylindrical single crystal can be obtained.

The crucible material used for pulling this single crystal is generally made by melting powdered silica in a rotating crucible. Therefore, air bubbles inevitably get mixed into the crucible. The bubbles expand in the molten silicon due to the high temperature. Furthermore, silica glass is gradually eroded by the molten silicon raw material. As a result, when the crucible is used for a long time, air bubbles generated from silica glass enter the solid-liquid interface of the silicon single crystal being pulled, resulting in a problem that the growth of the single crystal is inhibited.

As a method to solve this problem, JP-A-59-21
There is an invention disclosed in Publication No. 3697. This invention is
At least the side of the crucible in contact with the semiconductor raw material melting surface,
It is made of thick transparent silica glass to prevent the formation of bubbles. However, there are disadvantages in that the ability to prevent air bubbles from forming from the bottom is weak, and as the size of the crucible increases, the costs required for raw materials and processing become extremely high.

Although the purpose is not to directly prevent air bubbles, JP-A-56-7
In the invention disclosed in Japanese Patent No. 8496, quartz glass, quartz powder, quartz glass plates, or quartz glass rods are fused to the inner surface of a crucible.

However, this invention aims to equalize the oxygen concentration, and does not include any measures to prevent bubbles.

Furthermore, Japanese Patent Laid-Open No. 188498/1989 discloses an invention in which a silicon nitride film is coated on the surface of a crucible. Although this method obviously prevents bubbles, the oxygen concentration in the silicon decreases, resulting in a wafer unsuitable for IC use.

The present invention has been made in view of the above circumstances, and is a method for producing a single crystal using the Czochralski method, which avoids the adverse effects of air bubbles generated from the crucible, does not particularly increase the production cost, and produces a good silicon single crystal. The present invention aims to provide a crucible for pulling a single crystal to obtain a crystal.

[Means for Solving the Problems] A crucible for pulling a silicon single crystal according to the present invention is a crucible made of bubble-filled silica glass used for pulling a silicon single crystal using the Czochralski method. , a bubble-free resin glass plate having a diameter equal to or less than the inner diameter of the crucible and which does not generate bubbles near the melting point of silicon is installed.

[Operation] Convection within the crucible can be divided into thermal convection that rises along the crucible wall and forced convection that occurs due to the rotation of the silicon single crystal. Bubbles generated on the sides of the crucible quickly reach the melt surface due to the thermal convection and do not inhibit the growth of the single crystal.On the other hand, due to the forced convection, bubbles are generated at the center of the crucible from bottom to top. An upward flow is generated, and as a result, bubbles generated directly under the silicon single crystal at the bottom of the crucible rise and reach the interface between the silicon single crystal and the melt, inhibiting single crystal growth.

By covering the bottom of the crucible with a bubble-free silica glass plate that does not generate bubbles near the melting point of silicon, inhibition of single crystal growth due to bubbles can be prevented. In addition, there are two methods for fixing this bubble-free silica glass plate to the bottom of the crucible: one is to fuse it to the crucible in advance, and the other is to place this bubble-free silica glass plate on the bottom of the crucible before charging the silicon raw material to the crucible. Then, there is a method of fusion using heat to melt the silicon raw material.

[Example] Embodiments of the invention will be described with reference to the accompanying drawings.

FIG. 1 (a>, (b) is a diagram schematically showing one embodiment of the present invention, (a> is a longitudinal cross-sectional view of a crucible, (b) is a longitudinal cross-sectional view of a crucible,
In FIG. 1 showing a cross-sectional view, 1 is a crucible made of silica glass with bubbles, and 2 is a silica glass plate without bubbles.

Here, bubble-free silica glass is fused to the center of the bottom of the crucible along the curved surface of the bottom. Figure 2(a),
(b) is a diagram schematically showing another embodiment of the present invention, in which (a) is a vertical cross-sectional view of a crucible, and (b) is a cross-sectional view, a flat plate of bubble-free silica glass is shown. A welding part 3 is provided around the plate 2, and the plate 2 is fixed to the center of the bottom of the crucible 1 by welding at several points there. Figure 3 (
Figures a> and (b) are diagrams schematically showing other embodiments of the present invention, in which (a) is a longitudinal cross-sectional view of a crucible, and (b) is a cross-sectional view. glass feet 4
This is what was installed. In either case, the shape of the bubble-free silica glass may be circular or square, but the thickness is determined by calculating the amount of melted glass depending on the usage time of the crucible. The size of the bubble-free silica glass changes depending on the pulling conditions, but it is sufficient to cover the entire bottom of the crucible at most.

If the silica plate is welded to the crucible in advance as described above, there is no risk of the silica glass plate shifting when setting the crucible or charging raw materials. Alternatively, the welding may be performed using the heat generated when melting the silicon raw material after charging the silicon raw material.

In addition, the method and apparatus of the present invention are continuous in which a partition ring is immersed in the crucible to divide the inside of the crucible into a single crystal growth section and a raw material melting section, and raw material charging and single crystal growth are performed continuously over a long period of time. It is the most suitable for the operation.

[Effects of the Invention] According to the present invention, since a bubble-free silica glass plate is installed at the bottom of the crucible, it is possible to eliminate obstacles to single crystal growth due to air bubbles from the bottom of the crucible, without particularly increasing manufacturing costs. A good single crystal can be obtained.

[Brief explanation of the drawing]

1 to 3 are longitudinal and cross-sectional views of different crucibles according to embodiments of the present invention. 1... Crucible, 2... Bubble-free silica glass plate, 3
...Fused part, 4...legs.

Claims (4)

[Claims] (1) In a vitreous silica glass crucible used for pulling silicon single crystals in the Czochralski method, at the bottom of the inner surface of the crucible, a diameter of not more than the inner diameter of the crucible,
A crucible for pulling a silicon single crystal, characterized in that a bubble-free silica glass plate that does not generate bubbles near the melting point of silicon is installed. (2) The crucible for pulling a silicon single crystal according to claim 1, wherein the bubble-free silica glass plate is installed by welding the entire surface or a part of the silica glass plate to the bottom of the crucible. (3) The lower surface of the bubble-free silica glass plate has the same curved surface as the curved surface of the bottom of the crucible.
A crucible for pulling silicon single crystals as described in . (4) The crucible for pulling a silicon single crystal according to claim 1, wherein the bubble-free silica glass plate has reinforcing legs or beams at the bottom.