JP2002154890A - Crucible for pulling semiconductor silicon single crystal and method for producing semiconductor silicon single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the generation of vibration at liquid surface when a large diameter ingot is pulled while using a quartz crucible by a Czochralski method being one method for producing a silicon single crystal. SOLUTION: It is possible to suppress the deformation of the crucible and the generation of vibration at the liquid surface and to pull the large diameter silicon ingot in a good yield by providing a crucible for pulling semiconductor silicon. The crucible has been melted while vacuum exhausting in a vacuum vessel having a rotary mold and heating electrodes and has an inner transparent layer containing OH in an amount of <=5 ppm, in which the inner transparent layer to a depth of at least 1 mm from the surface is made of synthetic quartz.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quartz glass crucible for pulling single crystal silicon. Particularly, the present invention relates to a quartz glass crucible which is most suitable for pulling a large-diameter silicon ingot.

[0002]

2. Description of the Related Art CZ which is a method of manufacturing a silicon single crystal
In the (Czochralski) method, polysilicon is put in a quartz glass crucible, melted, a seed crystal is applied to a melt, and a single crystal is pulled up. In recent years, however, the charge amount of polysilicon has been rapidly increased due to an increase in diameter. Increasing the charge amount of polysilicon means prolonging the pulling time and increasing the heating temperature, and the load on each used member is also rapidly increasing. Conventionally, as a 22-inch, 24-inch or 32-inch quartz glass crucible, a crucible having a layer of synthetic quartz glass which is hardly devitrified on its inner surface is used. Japanese Patent Publication 58-5
0955 describes a crucible lined with synthetic quartz. Initially, this synthetic crucible was of ultra-high purity and was aimed at improving the purity of a silicon single crystal, but in reality there was no merit worth the cost. However, due to the semiconductor recession from 1998 to 2011, the large diameter was delayed,
Since semiconductor companies have focused on reducing the cost of 8-inch wafers, the trend has been to increase the amount of recharge or single charge, and synthetic quartz glass crucibles that do not easily devitrify even for a long time have become mainstream.

[0003]

The synthetic quartz crucible has a low viscosity because its silica matrix structure is random compared to natural quartz glass, and it is easy to deform the crucible itself and expand bubbles in the transparent layer on the inner surface. There's a problem. The difference in structure between the synthetic layer and the natural layer also causes the occurrence of liquid level vibration.

[0004]

Means for Solving the Problems The present inventors provided a rotating mold and a heating electrode in a vacuum vessel, and melted them while evacuating them to thereby reduce the OH of the inner transparent layer of the crucible.
If the content is 5 ppm or less, the liquid surface vibration will be reduced until practically no problem occurs, and if the inner transparent layer is at least 1 mm from the surface, the yield will not be reduced by devitrification of the inner surface of quartz glass. We have found and completed the present invention.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, a rotating mold and a heating electrode are provided in a vacuum vessel and melted while evacuating, so that the OH content of the inner transparent layer of the crucible is 5 ppm or less. , And at least from the surface of the inner transparent layer
Quartz crucibles of 1 mm or more are provided. Natural quartz powder is formed by centrifugal force in a rotating mold, and then synthetic powder is formed on the inner surface. The thickness of the synthetic powder at this time is 1.7 mm
Above. 1 mm or more on the inner surface after melting by setting it to 1.7 mm or more
The above composite layer is formed. The vacuum vessel is closed, and the air is gradually evacuated to a degree of vacuum of 1 Torr or less, preferably 0.01 Torr or less. This is to discharge a large amount of gas generated during melting out of the system. If this gas remains in the bubbles, the bubbles expand when the silicon single crystal is pulled up,
Affects the yield of single crystallization. Next, the heating electrode is inserted into the mold and the voltage is charged. In this case, graphite, tungsten, or the like can be used as the heating electrode. The heating program is closely related to sintering. The sintering of the synthetic powder starts at 1400 ° C and rapidly sinters between 1500 and 1700 ° C. Sintering occurs at the earliest or later, and bubbles are generated. Preferably the temperature rises sharply to 1650 ° C, then 10 ° C to 1750 ° C.
Preferably, the temperature is raised from 0 ° C / h to 20 ° C / h. When the required thickness of the transparent layer is achieved, the vacuum is released to about 60 torr with Ar gas, the heating temperature is increased from 1800 to 2000 ° C, and the outer layer is made an opaque layer. After the completion of the melting, the electrode is immediately raised, and when the temperature of the quartz crucible is about 1150 to 1250 ° C., the electrode is inserted again, the temperature is maintained at 1150 to 1250 ° C. for about 30 minutes, and then the crucible is taken out by rapid cooling. The OH value of the synthetic silica glass inner layer is calculated by the following equation using the value calculated by the infrared absorption spectrometer. OH (ppm) = 910 × (1 / T) × log (Ta / Tb) T: sample thickness (mm) Ta: transmittance of 2.6 μm (%) Tb: 2.73
μm transmittance (%) The content of this OH group is 50 ppm for the synthetic powder used.
Or even 100 ppm will be less than 5 ppm. This is because the Si-OH dissociates and diffuses when held at a high temperature and escapes from quartz glass. When the OH content becomes 5 ppm or less,
The viscosity of the synthetic layer is almost the same as that of natural quartz glass. This not only improves the viscosity of the entire crucible, but also reduces the liquid surface vibration of the silicon melt. The reason why the thickness of the inner surface synthetic layer is set to 1 mm or more is that, due to the melting of silicon for a long time, quartz glass is melted, and in some cases 1 mm or more is melted, natural quartz is exposed, causing devitrification,
This is for reducing the yield of single crystallization.

[0006]

Embodiments of the present invention will be described below. Example The apparatus shown in FIG. 1 is the apparatus used in the present invention. Reference numeral 1 denotes a water-retained stainless steel vacuum vessel, in which an upper portion is provided with a graphite electrode and a lifting device.
The 4-thyristor control circuit controls the temperature while taking in the signal of the radiation thermometer attached to the viewing window at the top of the 11 water-cooled containers. A mold 5 with a rotating mechanism is provided below the vacuum vessel, and a graphite heat insulating material 6 is provided around the mold 5. The vacuum vessel is provided with a mechanical booster 8 and a rotary pump 9, and a PIC for controlling the degree of vacuum and a valve 10 for introducing Ar gas. 40 kg of natural quartz powder IOTA-6 (manufactured by UNIMINE, USA) was charged into a rotating stainless steel water-cooled mold having an inner diameter of 650φ and molded, and 10 kg of synthetic powder SQ (manufactured by Asahi Denka) was charged from above. The vacuum vessel was closed, and the pressure was reduced to 0.005 torr with a rotary pump and a mechanical booster. After that, the graphite electrode was lowered, and the temperature was raised to 1650 ° C in 30 minutes.
After the temperature was raised to 50 ° C. in 1 hour, the temperature was raised to 1950 ° C. in 10 minutes. Thereafter, the mechanical booster was turned off, Ar gas was injected, the degree of vacuum was released to 40 torr, and melting was performed at 1950 ° C. for 20 minutes. Next, the temperature of the inner surface of the crucible was rapidly cooled to 1250 ° C., kept at 1250 ° C. for 15 minutes, the graphite electrode was turned off, the electrode was separated from the crucible, and allowed to cool. The OH value of the inner synthetic transparent layer of this crucible is 2 ppm and that of the outer natural quartz glass layer
The OH value was 1 ppm or less. The respective viscosities were log values of 10.75 and 10.87 at 1400 ° C. The transparent layer of this crucible was 5 mm, of which the composite layer was 4 mm. No visible bubbles were present in this synthetic transparent layer. After trimming the height to 450mm and washing, pour 200kg of polysilicon and pull up 12 "single crystal,
The liquid surface vibration did not occur, and all liquids could be pulled up automatically. The yield was 100% of the expected yield. When a cross section of the crucible after use was examined with a microscope, no bubbles were visually observed in the inner synthetic transparent layer. In addition, as a result of examination with an electron microscope, 1
Bubbles were present, but disappeared after withdrawal.

[0007]

Industrial Applicability The crucible of the present invention can provide a practically usable synthetic crucible having a high viscosity, having no occurrence of liquid level vibration, and having an inner surface synthetic layer having almost no air bubbles.

[Brief description of the drawings]

FIG. 1 is an apparatus of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Stainless steel water-cooled vacuum vessel 2 Graphite electrode 3 Electrode raising / lowering device 4 Power control panel 5 Water-cooled mold 6 Graphite plate 7 Pressure control valve 8 Mechanical booster 9 Rotary pump 10 Argon introduction mass flow 11 Pressure sensor 12 Radiation thermometer 13 Rotary motor

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G014 AH00 4G077 AA02 BA04 CF10 EG01 HA12

Claims (2)

[Claims] 1. A method of manufacturing a semiconductor silicon pulling crucible, comprising: providing a rotating mold and a heating electrode in a vacuum vessel; 2. The crucible produced by the method of claim 1, wherein the inner transparent layer has an OH content of 5 ppm or less, and at least 1 mm from the surface of the inner transparent layer is made of synthetic quartz. Crucible for pulling up semiconductor silicon