JP2008094639A - Silica glass crucible - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silica glass crucible which is suitable for pulling up a semiconductor single crystal such as silicon or the like in a good yield and by which an impurity contamination caused by the crucible is prevented and a liquid surface vibration of a raw material melt liquid filled in the crucible can be effectively suppressed. <P>SOLUTION: In a silica glass crucible comprising a transparent silica glass layer at the inside surface side and an opaque silica glass layer containing closed bubbles at the outer periphery, the part at 500 μm from the inside surface of the crucible in the thickness direction is composed of having fluorescence intensity at the peak wavelength of 390 nm of 0.15 or lower of the base fluorescence intensity at the wavelength of 560 nm of the 10 ppb ethanol solution of rhodamine B when irradiating an excitation light having the wavelength of 242 nm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a silica glass crucible suitably used for melting a raw material in pulling a semiconductor single crystal such as silicon.

  Semiconductor single crystals such as silicon are mainly manufactured by the Czochralski (CZ) method. The production of a silicon single crystal by the CZ method involves growing a silicon single crystal ingot by immersing a seed crystal of a silicon single crystal into a silicon raw material melt obtained by melting polycrystalline silicon and gradually pulling it up while rotating. Is done.

In the silicon single crystal pulling by the CZ method as described above, the container for heating and melting the raw material is generally a natural silica glass in which the outer layer is melted and vitrified from a natural raw material such as quartz, and the inner layer is a transparent synthetic silica. A silica glass crucible made of glass is used.
However, when the raw material silicon is melted in such a silica glass crucible, the liquid surface of the silicon raw material melt is more likely to vibrate than a crucible made only of natural silica glass. In particular, the vibration at the initial stage of the single crystal pulling process is large, and there is a problem that the seeding is poor when the seed crystal is deposited, or the meltback is caused to reduce the productivity.

On the other hand, for example, Patent Document 1 describes that the vibration of the surface of the silicon raw material melt can be suppressed by using natural silica glass for the inner layer in a specific range of the crucible straight body portion. .
Patent Document 2 describes that the vibration of the silicon raw material melt surface can be suppressed by a silica glass crucible in which a region containing a predetermined amount of bubbles of a specific size is formed in a part of the inner layer of the crucible. Yes.
JP 2004-59140 A JP 2005-206446 A

  However, the crucible containing the natural silica glass in the inner layer as described in the above-mentioned Patent Document 1 generally has a larger amount of impurities than the synthetic silica glass. Impurity contamination of single crystal is likely to occur. For this reason, it is difficult to say that the crucible is a preferred embodiment for pulling up a silicon single crystal that requires high purity and high quality.

  Moreover, the fundamental cause of the liquid level vibration of the silicon single crystal raw material melt in the crucible has not been clarified, and as described in Patent Document 2, the inclusion in the silica glass constituting the crucible It was not always possible to suppress the liquid level vibration of the silicon single crystal raw material melt only by specifying the bubble density.

  Therefore, in a silica glass crucible used for pulling up a semiconductor single crystal such as silicon, the crucible itself does not become a source of impurity contamination of the single crystal to be pulled up, and vibration of the surface of the raw material melt can be effectively suppressed. Things are sought.

  The present invention has been made to solve the above technical problem, and does not cause impurity contamination caused by the crucible, and is effective for vibration of the liquid surface of the single crystal raw material melt filled in the crucible. An object of the present invention is to provide a silica glass crucible suitable for pulling up a semiconductor single crystal such as silicon with high yield.

A silica glass crucible according to the present invention is a silica glass crucible having a transparent silica glass layer on the inner surface side and an opaque silica glass layer including closed pores on the outer periphery thereof, and the crucible inner surface in the cross section in the thickness direction To 500 μm, the fluorescence intensity at a peak wavelength of 390 nm when irradiated with excitation light having a wavelength of 242 nm is 0.15 or less of the reference fluorescence intensity at a wavelength of 560 nm of a 10 ppb ethanol solution of rhodamine B.
According to the crucible that defines the physical properties of the silica glass on the inner surface as described above, in the process of pulling up the semiconductor single crystal, the liquid surface vibration of the single crystal raw material melt filled in the crucible can be suppressed, Contamination of the single crystal raw material melt due to impurities contained in the silica glass constituting the crucible can be suppressed.

As described above, according to the silica glass crucible according to the present invention, the silicon single crystal pulled from the single crystal raw material melt filled in the crucible is filled in the crucible without causing impurity contamination due to the crucible. It is possible to effectively suppress the liquid level vibration of the melted silicon single crystal raw material.
Therefore, the silica glass crucible according to the present invention can be suitably used to pull up a semiconductor single crystal such as silicon with a high yield.

Hereinafter, the present invention will be described in more detail.
The silica glass crucible according to the present invention has a multilayer structure in which the inner surface is a transparent silica glass layer made of synthetic silica glass, and the outer peripheral portion is an opaque silica glass layer containing many closed pores.
By having closed pores on the outer periphery, the infrared transmittance from the heater outside the crucible can be reduced when pulling up the single crystal, and the liquid level vibration of the silicon single crystal raw material melt filled in the crucible The effect which suppresses is produced.

However, if the inner surface of the crucible is made of opaque silica glass containing closed pores, the reaction between the silica glass on the inner surface of the crucible and the silicon single crystal raw material melt releases the pores in the silica glass on the inner surface of the crucible. Due to the large diameter of the bubbles, the dislocation-free rate of the pulled single crystal is lowered.
For this reason, the crucible inner surface is a transparent silica glass layer that does not contain closed pores. Moreover, by forming this transparent silica glass layer with high-purity synthetic silica glass, impurity contamination from the inner surface of the crucible to the silicon single crystal raw material melt can be suppressed.

Further, when pulling up the silicon single crystal, as described above, the silicon single crystal raw material melt filled in the crucible reacts with the silica glass on the inner surface of the crucible, and the inner surface of the crucible is eroded.
Therefore, the glass structure in the region within 500 μm in the thickness direction from the inner surface of the crucible affects the liquid level vibration of the silicon single crystal raw material melt filled in the crucible.
The present invention is based on the finding that the inner surface portion of the crucible is formed of silica glass exhibiting a specific fluorescence spectrum, whereby the crucible capable of effectively suppressing the liquid surface vibration can be obtained. It is.
That is, the silica glass crucible according to the present invention has a 10 ppb ethanol solution of rhodamine B having a fluorescence intensity of a peak wavelength of 390 nm when a portion of 500 μm from the inner surface of the crucible is irradiated with excitation light having a wavelength of 242 nm in the cross section in the thickness direction. The reference fluorescence intensity at a wavelength of 560 nm is 0.15 or less.

Silica glass exhibits a light absorption band called B2β at a wavelength of 242 nm, and emits blue light having a peak at a wavelength of 390 nm. This is considered to be caused by oxygen-deficient Si and SiO (“Amorphous Silica Material Application Handbook”, Realize Inc., 1999, p. 211, Philipp, J. Phys Chem. Solids, 1971. 32, p. 1935).
When these oxygen-deficient Si and SiO are present in the silica glass on the inner surface of the crucible, the wettability of the silicon single crystal raw material melt with respect to the inner surface of the crucible greatly changes, and the silicon single crystal raw material melt filled in the crucible Cause liquid level vibration.
Therefore, it is preferable that the silica glass crucible according to the present invention does not contain oxygen-deficient Si and SiO as described above in a region from the inner surface of the crucible to 500 μm in the cross section in the thickness direction.
In the present invention, as a means for detecting such oxygen-deficient Si and SiO, fluorescence intensity measurement at a peak wavelength of 390 nm is performed in a fluorescence spectrum when irradiated with excitation light having a wavelength of 242 nm.

The determination of the fluorescence intensity is based on the fluorescence intensity at a wavelength of 560 nm when a 10 ppb ethanol solution of rhodamine B (C ₂₈ H ₃₁ ClN ₂ O ₃ ), which is a typical fluorescent dye, is irradiated with excitation light having a wavelength of 242 nm. Do.
Since it is difficult to prepare a standard sample using silica glass, a fluorescent dye solution that is easily obtained and prepared as described above is used as the standard sample.

  The fluorescence intensity at the peak wavelength of 390 nm when the excitation light having the wavelength of 242 nm is irradiated to the 500 μm portion from the inner surface of the crucible in the cross section in the thickness direction is 0.15 or less with respect to the reference fluorescence intensity by the fluorescent dye. If it is a certain silica glass crucible, the liquid level vibration of the silicon single crystal raw material melt filled in the crucible can be effectively suppressed.

The silica glass crucible according to the present invention as described above can be produced by, for example, the following method.
First, natural silica raw material powder such as crystal is put into a crucible mold having a plurality of through holes and rotated to form a crucible-shaped outer layer. Synthetic silica raw material powder obtained by hydrolysis of silicon alkoxide or silicon tetrachloride is introduced so as to cover the inner surface of the outer layer. By inserting an arc electrode into this and vitrifying by vacuum arc melting while introducing a predetermined amount of water vapor, the inner side is a transparent silica glass layer, and the outer peripheral part is an opaque silica glass layer containing many closed pores. A silica glass crucible is obtained. Furthermore, the silica glass crucible according to the present invention is obtained by subjecting this crucible to annealing treatment in a reducing atmosphere.

EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example, this invention is not restrict | limited by the following Example.
First, natural silica raw material powder was put into a crucible mold having a plurality of through holes and rotated to form a crucible-shaped outer layer. Synthetic silica raw material powder was introduced so as to cover the inner surface of the outer layer. An arc electrode was inserted therein, and vitrification was performed by reduced-pressure arc melting while introducing a predetermined amount of water vapor.
The amount of water vapor introduced at this time was changed, and 15 silica glass crucibles having a diameter of 24 inches, which was a transparent silica glass layer on the inner side and an opaque silica glass layer containing a large number of closed pores on the inner side, were produced.
Further, each crucible was annealed in a reducing atmosphere to obtain a silica glass crucible used for pulling a silicon single crystal.

A 2 mm × 4 mm, 1 mm thick measurement sample is cut out from each crucible, and the fluorescence intensity at a peak wavelength of 390 nm is measured when excitation light having a wavelength of 242 nm is irradiated to a 500 μm portion from the inner surface of the crucible in the cross section in the thickness direction. did.
This fluorescence intensity was determined as a relative intensity with respect to the reference fluorescence intensity at a wavelength of 560 nm of a 10 ppb ethanol solution of rhodamine B. These results are shown in Table 1.

Moreover, the state of the liquid surface vibration of the raw material melt in the crucible when the silicon single crystal was pulled by the CZ method was investigated using each crucible. These results are shown in Table 1.
In the evaluation in Table 1, the case where there is no liquid level vibration or there is almost no liquid level vibration and the seeding can be performed smoothly is indicated by ○, and the case where the liquid level vibration is so large that the seeding is difficult. X.

  As shown in Table 1, the relative fluorescence intensity at a peak wavelength of 390 nm (wavelength 560 nm of a 10 ppb ethanol solution of rhodamine B) when a portion of 500 μm from the inner surface of the crucible is irradiated with excitation light having a wavelength of 242 nm in the cross section in the thickness direction. In the silica glass crucible according to the present invention having a fluorescence intensity standard) of 0.15 or less, it was confirmed that the liquid level vibration of the silicon single crystal raw material melt filled in the crucible was suppressed.

Claims (1)

  A silica glass crucible having a transparent silica glass layer on the inner surface side and an opaque silica glass layer including closed pores on the outer periphery thereof, and having a wavelength of 242 nm at a portion of 500 μm from the inner surface of the crucible in the cross section in the thickness direction A silica glass crucible, wherein the fluorescence intensity at a peak wavelength of 390 nm when irradiated with excitation light is 0.15 or less of the reference fluorescence intensity at a wavelength of 560 nm of a 10 ppb ethanol solution of rhodamine B.