JPH05105574A - Cleaning and recovery of impurity on inner surface of quartz crucible - Google Patents

Abstract

PURPOSE:To wash and analyze the impurity on the inner surface of a quartz crucible using a small amount of chemical agent. CONSTITUTION:Vapor of hydrofluoric acid is made to contact with the inner surface of a closed quartz crucible 1 and the surface is washed with pure water to wash off the impurities on the inner surface. The washed liquid is recovered and analyzed. The amount of hydrofluoric acid can be decreased, the processing time can be shortened and the dissolving thickness of the inner surface of the quartz crucible can delicately be controlled to enable the accurate investigation of the impurity distribution in the direction of depth.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to cleaning and recovery of impurities on the inner surface of a quartz crucible used for growing a silicon single crystal for semiconductors.

[0002]

2. Description of the Related Art Conventional cleaning methods for quartz crucibles include nitric acid,
A method of dissolving a few + micron near the surface with a chemical such as hydrofluoric acid is used. On the other hand, as a chemical analysis method for impurities in a quartz crucible, there is used a method in which quartz is made into a fine powder or directly, and the surface thereof is dissolved with a chemical such as nitric acid or hydrofluoric acid to carry out chemical analysis. SIM is used as a physical analysis method.
The S (secondary ion mass spectrometry) method is used.

[0003]

The quartz crucible for growing a silicon single crystal contains impurities on the surface and in the bulk, which are dissolved in the silicon melt during the growth of the single crystal to lower the purity of silicon. , Adversely affecting the occurrence of crystal defects. Therefore, it is necessary for a quartz crucible for producing a single crystal to accurately measure the purity of the surface and a depth of a few under the surface + a depth of micron, and to clean immediately before use. However, in the conventional chemical analysis method, the quartz crucible is made into a fine powder, or the surface is dissolved with a chemical such as nitric acid or hydrofluoric acid for analysis.
It is impossible to measure the impurities on the very surface and the total impurities separately. Further, although the analysis using SIMS is very easy to analyze the impurities on the surface, the analysis region is too small, that is, a few + microns, and is not suitable for the evaluation of the entire surface of the quartz crucible.
In addition, there is a problem that it takes a lot of time to prepare and measure a sample and the cost is large. Next, in the method of cleaning the quartz crucible, a large amount of chemicals is used in order to dissolve the entire surface of the quartz crucible by immersing the entire quartz crucible in hydrofluoric acid or nitric acid or spraying and spraying. Further, in the case of immersion, there is a problem that impurities are left in the chemicals and a stable cleaning effect cannot be obtained.

[0004]

The present invention is a method for cleaning the inner surface of a quartz crucible, which comprises contacting hydrofluoric acid vapor with the surface of a sealed quartz crucible and then cleaning with pure water. Further, it is a method for recovering impurities on the inner surface of the quartz crucible, in which the liquid washed in the method of the preceding paragraph is recovered and used for analysis of impurities on the inner surface of the quartz crucible.

[0005]

According to the present invention, since the inner surface of the closed quartz crucible is dissolved by the hydrofluoric acid vapor, it is possible to dissolve only the very inner surface of the crucible, which is required. There are few impurities and no impurities remain in hydrofluoric acid. The thickness of the layer to be dissolved can be controlled by adjusting the time of contact with the hydrofluoric acid vapor.

[0006]

EXAMPLE An example of a quartz crucible having a diameter of 355 mm, a height of 350 mm and a wall thickness of 10 mm will be described. As shown in Fig. 1, place a hydrofluoric acid container 2 containing 200cc of hydrofluoric acid on a hydrofluoric acid resistant Teflon sheet 3 laid to keep the airtight state and prevent the intrusion of impurities, and place the quartz crucible 1 on it. When it is covered, the vaporized hydrofluoric acid vapor contacts the inner surface of the quartz crucible and melts the inner surface of the quartz crucible. FIG. 2 shows a method of recovering impurities. 30 cc of pure water 5 is poured with the opening of the quartz crucible facing upward. The impurities are washed and collected while tilting the quartz crucible and bringing pure water into contact with the bottom and side surfaces of the quartz crucible. The recovered liquid was analyzed by an atomic absorption method.
Table 1 shows a comparative example together with the examples in which the above-mentioned quartz crucible was washed and collected by the conventional method of immersing the entire quartz crucible in hydrofluoric acid.

[0007]

[Table 1]

According to the method of the present invention, as shown in Table 1, the amount of hydrofluoric acid used was smaller than that of the comparative example, and the number of steps required for the treatment could be reduced. Further, the surface to be dissolved can be limited to the inner surface, and unlike the comparative example, the unnecessary outer surface is not dissolved and a large amount of hydrofluoric acid waste liquid is not generated. Further, the thickness of dissolution can be controlled more finely, and the distribution of impurities in the depth direction can be examined in detail.

[0009]

As described above, according to the method of the present invention, the amount of hydrofluoric acid used is small, the time required for the treatment can be shortened, and the melting thickness of the inner surface of the quartz crucible can be finely controlled. The distribution can also be investigated accurately.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a method for cleaning impurities on an inner surface of a crucible according to the present invention.

FIG. 2 is an explanatory diagram showing a method of collecting impurities.

[Explanation of symbols]

 1 Quartz crucible 2 Hydrofluoric acid container 3 Teflon sheet 4 Hydrofluoric acid 5 Pure water

Claims (2)

[Claims] 1. A method for cleaning the inner surface of a quartz crucible, which comprises contacting hydrofluoric acid vapor with the inner surface of a closed quartz crucible and then cleaning with pure water. 2. Collecting the liquid washed in claim 1,
A method for recovering impurities from the inner surface of a quartz crucible for use in analyzing impurities on the inner surface of the quartz crucible.