JP2789804B2 - Quartz crucible for pulling silicon single crystal and its manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a quartz crucible for pulling a silicon single crystal having a high silicon single crystallization rate and a method for producing the same. More specifically, the present invention relates to a quartz crucible for pulling a silicon single crystal, which has a uniform opaque layer to increase the single crystallization ratio, and a method for manufacturing the same.

(Prior art)

A silicon single crystal is mainly manufactured by a method of pulling molten polycrystalline silicon (CZ method), and a quartz crucible is used as a container for charging the molten polycrystalline silicon.

Quartz crucibles are manufactured by various methods, and a rotary molding method is known as a typical manufacturing method.
This method is a method in which quartz powder as a raw material is deposited in a layer on the inner peripheral surface of a crucible-shaped rotary mold, heated, melts the inner surface of the quartz deposited layer into a glass, and then cooled and solidified. In addition, various methods similar to the above methods are known.

By the way, most of the conventional quartz crucibles manufactured by the above methods have an opaque layer containing fine bubbles formed on the outer peripheral side to protect the inner transparent layer. When the fused polycrystalline silicon is charged into the quartz crucible, the opaque layer serves to enhance the heat insulating effect of the quartz crucible.

[Problems to be solved]

In the conventional quartz crucible, since the layer thickness of the opaque layer is not always the same in each part, the heat insulating effect becomes uneven,
There are various problems. For example, if the opaque layer on the peripheral wall or the bottom of the quartz crucible is not uniform, the molten silicon charged into the quartz crucible tends to cause undesirable convection disturbance,
There is a problem that the single crystallization ratio is reduced because the pulling of the silicon single crystal is adversely affected. Also, as the silicon single crystal is pulled up, the liquid level of the molten silicon falls, so if the opaque layer on the top of the quartz crucible is not uniform, the radiant heat transmitted through the opaque layer will be uneven, and the silicon crucible will be pulled up. The obtained silicon single crystal receives uneven radiant heat and causes crystal defects.

[Solution for problem]

The present inventors have found that in a quartz crucible for pulling a silicon single crystal, a high single crystallization ratio can be achieved by controlling the thickness of the opaque layer within a certain range.

An object of the present invention is to provide a quartz crucible for pulling a silicon single crystal and a method of manufacturing the same, which have solved the conventional problems described above based on the above findings.

[Configuration of the invention]

According to the present invention, there is provided a quartz crucible having an opaque layer on the outer periphery and a transparent layer on the inner periphery, wherein the thickness of each portion of the opaque layer is 130 to 70% of the average thickness of the opaque layer. There is provided a quartz crucible for pulling a silicon single crystal characterized by the following. In a preferred embodiment, a quartz crucible having an opaque layer having an average thickness of 1 mm to 10 mm or a quartz crucible having a transparent layer having a bubble content of 0.1% or less is provided.

Furthermore, according to the present invention, in a method for manufacturing a quartz crucible in which quartz powder is deposited on the inner peripheral surface of a rotary mold, and heated and melted, and then cooled, the melting rate of the deposited quartz powder is made uniform to form a transparent layer and an opaque layer. A method for manufacturing a quartz crucible for pulling a silicon single crystal, characterized in that the thickness is made uniform.

The wall thickness of the entire wall of the quartz crucible varies depending on the diameter of the crucible, but is usually 8 to 12 mm, and the thickness of the inner transparent layer is about 2 to 4 mm in consideration of the amount of erosion, and therefore the outer The average thickness of the opaque layer is 4 to 10 mm.

In the quartz crucible of the present invention, the layer thickness of each portion of the opaque layer is maintained at 130 to 70% of the average layer thickness of the opaque layer. The layer thickness of each part of the opaque layer is
If it is more than 130% or less than 70%, the heat insulating effect in that part becomes uneven, causing undesired convection turbulence in the molten silicon charged in the crucible, and the pulled silicon single crystal becomes uneven. Radiated heat, and the single crystallization ratio is reduced. On the other hand, when the thickness of each portion of the opaque layer is maintained at 130 to 70% of the average thickness of the opaque layer, such a disadvantage does not occur.

In the quartz crucible, the bubble content of the transparent layer is preferably controlled to 0.1% or less. The bubble content P is represented by a ratio (w / W × 100%) of an occupied area w of bubbles contained in a fixed area W of the quartz crucible wall. When the bubble content of the transparent layer exceeds 0.1%, the inner peripheral surface of the transparent layer is easily peeled off due to the expansion of the bubbles when pulling up the silicon single crystal, and the single crystallization ratio decreases.

Next, when the quartz crucible of the present invention is manufactured by the rotary molding method, it can be manufactured by depositing quartz powder on the inner peripheral surface of the rotary mold and then making the melting rate of the deposited quartz powder uniform. To uniformly control the melting rate of the deposited quartz powder, the heat source should be kept equidistant from the inner surface of the crucible,
Alternatively, the heating source may be reciprocated to continuously average and heat. The melting rate may be controlled by adjusting the heating temperature.

〔The invention's effect〕

In the quartz crucible of the present invention, since the layer thickness of the opaque layer is formed in a certain range in each part, the heat insulating property is kept uniform, and when the molten silicon is charged into the quartz crucible, the silicon single crystal is pulled up. The convection turbulence that adversely affects the airflow does not occur. Further, even when the single crystal is pulled up and the liquid level of the silicon solution falls, the radiant heat passing through the opaque layer is uniform, and the pulled silicon single crystal does not receive uneven radiant heat. Therefore, a high single crystallization ratio can be achieved, and the produced single crystal has few crystal defects.

〔Example〕

 Examples of the present invention are shown together with comparative examples.

Examples 1 to 6 The wall thickness of the container was 8 to 12 mm by the rotating molding method.
When manufacturing a quartz crucible, the distance between the quartz powder deposited on the inner peripheral surface of the mold and the heater is kept constant, and the opaque layer having an average layer thickness of 1 to 10 mm is adjusted while adjusting the heating time and the decompression time. A quartz crucible having the same was manufactured. Further, a silicon single crystal was pulled using this quartz crucible. Table 1 shows the results.

As shown in Table 1, in the examples of the present invention, the single crystallization ratio was 77 to 78%, and an excellent single crystallization ratio was achieved.

Comparative Examples 1 to 3 Quartz crucibles were produced in the same manner as in Example 1 except that the melting rate of the quartz powder was not controlled, and the heating time and the decompression time were changed. Further, a silicon single crystal was pulled using this quartz crucible. The results are shown in Table 1.

As shown in Table 1, the single crystallization ratio of this comparative example is 50 to 60% in each case, and it is understood that the single crystallization ratio is significantly lower than that of the example of the present invention.

Claims (4)

(57) [Claims] 1. A quartz crucible having an opaque layer on the outer periphery and a transparent layer on the inner periphery, wherein the thickness of each portion of the opaque layer is 130 to 70% of the average thickness of the opaque layer. Characteristic quartz crucible for pulling silicon single crystal. 2. The quartz crucible according to claim 1, wherein the opaque layer has an average thickness of 1 mm to 10 mm. 3. The quartz crucible according to claim 1, wherein the bubble content of the transparent layer is 0.1% or less. 4. Quartz powder is deposited on the inner peripheral surface of the rotary mold,
In the method of manufacturing a quartz crucible to be cooled after heating and melting,
A method of manufacturing a quartz crucible for pulling a silicon single crystal, wherein the melting rate of the deposited quartz powder is made uniform to make the thicknesses of the transparent layer and the opaque layer uniform.