JPH0388792A - Quartz crucible for pulling up silicon single crystal and its production - Google Patents

Abstract

PURPOSE:To obtain the high-quality crucible with the amt. of the unmelted quartz powder remaining in the outer wall of the crucible remarkably reduced as compared with the conventional crucible by spraying high pressure water onto the outer wall to remove the deposited unmelted quartz powder. CONSTITUTION:The quartz crucible produced by the rotary-mold method is placed on a holder fixed on the rotating shaft. The crucible is rotated, and high pressure water is injected toward the crucible from the vertically movable nozzle set on the side wall of the crucible and sprayed on the outer wall. The water pressure is preferably controlled to 250-400kg/cm<2> or more preferably to 280-300kg/cm<2>. When the quartz crucible freed of unmelted quartz powder is used to pull up an Si single crystal, yield of the single crystal is increased to >=70%, and the single crystal conversion efficiency is improved as compared with the case where a crucible ground by a grindstone, etc., is used.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a quartz crucible for pulling silicon single crystals used as semiconductors and a finishing method thereof.

[Prior art and problems]

Pulling of silicon single crystals for semiconductors by the Czochralski (CZ) method is carried out by melting raw silicon in a quartz crucible. Currently, quartz crucibles are generally manufactured using a rotary molding method. In the rotary molding method, quartz powder is deposited in a crucible shape and then heated and melted from the inside to form a glass-like quartz crucible with a transparent inner wall. On the other hand, the outermost layer of the outer wall of the crucible should be kept in a slightly thin, opaque state of unfused quartz powder so that the crucible can be easily removed from the mold.

However, if a large amount of these unfused quartz powder remains, the particles scattered when pulling the silicon single crystal react with the silicon to generate silicon monoxide (Sj, 0) vapor, which condenses at the upper edge of the crucible. and get mixed into silicon crystals,
Alternatively, the quartz powder may be mixed into the single crystal as it is, causing a decrease in the silicon single crystallization yield.

Conventionally, the unfused quartz powder remaining on the outer wall of the crucible is removed by fire polishing or grinding with a grindstone, but the grinding process is extremely troublesome and the effect of the grinding is not always sufficient. Therefore, there is a limit to the improvement in the single crystallization yield. In addition, if you polish it with a metal brush.

Although most of the unfused quartz powder can be removed, it is undesirable because it tends to cause scratches on the outer surface of the crucible and metal powder adheres as impurities.

[Knowledge related to problem solving]

In the present invention, it has been found that adhering unfused quartz powder can be effectively removed by spraying high-pressure water onto the outer wall of the crucible.

[Structure of the invention]

The present invention provides a finishing method for a quartz crucible for pulling silicon single crystals, which comprises spraying high-pressure water on the outer wall of the crucible to remove adhering unfused quartz powder, and a quartz crucible for pulling silicon single crystals produced by this method. I will provide a.

As mentioned above, unfused quartz powder adheres to the outer wall of the quartz crucible manufactured by the rotary molding method. In the present invention, these unfused quartz powders are removed by spraying high-pressure water from the outside. The pressure of high pressure water used is 250 to 400 kg/aJ
is preferable, and 280 to 300 kg/aJ is more preferable. If it is less than 250 kg/cd, the time required to remove the remaining unfused quartz powder will be long and the removal will not be sufficient. Moreover, if it exceeds 400 kg/aJ, there is a risk that the outer peripheral edge will be damaged, which is not preferable.

There are various methods for spraying high-pressure water onto the outer wall of the crucible, but one preferred method is to place the crucible on a stand mounted on a rotating shaft, and while rotating the crucible, High-pressure water is jetted toward the crucible from a vertically movable nozzle installed on the side, spraying it against the outer wall of the crucible.

The rotation of the crucible and the vertical movement of the nozzle may be performed using mechanical power such as a motor, or may be performed manually.

The sprayed water and the removed quartz powder may be discharged to the outside through a container or a gutter from a water receiver installed at the bottom of the stand.

〔Effect of the invention〕

The amount of unfused quartz powder remaining on the outer wall of the quartz crucible made using the finishing method of the present invention is significantly smaller than that of conventional crucibles. When silicon single crystals are pulled using this crucible, the single crystallization yield is over 70%, compared to using a crucible ground with a conventional grindstone.
Single crystallization yield is improved.

[Examples and comparative examples]

The present invention will be specifically explained below using Examples and Comparative Examples.

Example A quartz crucible for pulling silicon single crystals made by the rotary molding method was placed on a rotating table, and while the crucible was being rotated, a high pressure of 300 kg/a# was applied from a nozzle installed on the side of the crucible that could move up and down. Water was sprayed onto the outer wall of the crucible to remove the remaining unfused quartz powder. After spraying high-pressure water over the entire surface of the outer wall of the crucible for 5 minutes, we measured the amount of unfused quartz powder remaining on the outer wall of the crucible.4
．． It was 5g.

The amount of residual unfused quartz powder was determined by measuring the weight of the entire crucible after high-pressure water treatment, and then polishing the surface of the crucible with a metal brush, measuring the weight of the entire crucible again, and determining the difference between the two. As a result of pulling a silicon single crystal using this crucible, a single crystallization yield of 73% was obtained (Table).

Comparative Examples 1 to 2 A quartz crucible made by the rotary molding method under the same conditions as the example was used to remove unfused quartz powder using a grindstone as in the past, and Si monomer was made under the same conditions as the example. Comparative Example 1 is a case in which a crystal is pulled, and a case in which a Si single crystal is pulled under the same conditions as in the example using a quartz crucible sprayed with 200 kg/a# pressure water for 15 minutes using the same equipment as in the example. Comparative Example 2 was prepared and the same measurements as in the example were carried out.

The results are shown in the table below.

In the table, the evaluation of single crystallization yield is 070% or more -E,
Δ65-70%, ×65% or less.

Claims (1)

[Claims] 1. A method for producing a quartz crucible for pulling silicon single crystals, which comprises spraying high-pressure water on the outer wall of the crucible to remove adhering unfused quartz powder. 2. A quartz crucible for pulling silicon single crystals produced by the method of claim 1.