JPS58185496A - Method of making silicon nitride jig for pulling up silicon single crystal - Google Patents

Abstract

PURPOSE:After a smooth base material of a desired shape is coated with a film of crystalline silicon nitride by the CVD method, the substrate is removed to give a crucible that can give good-quality single crystal of low oxygen content. CONSTITUTION:A substrate of a desired shape with smooth surfaces, e.g., a glass carbon with a surface roughness of less than 350mu Hmax, is placed in a CVD reaction furnace to effect coating with crystalline silicon nitride. Then, the carbon substrate is removed by oxidation. The resultant silicon nitride crucible has a small surface area and has a small amount of silicon nitride dissolved in the silicon melt, whereby the silicon crystal grows as a single crystal not as a polycrystal.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a silicon nitride jig used for pulling columnar or plate-shaped single crystal silicon.

The Choralski method (CZ method) is known as a method for manufacturing cylindrical single crystal silicon for cutting out semiconductor wafers. This method melts the silicon raw material in a crucible,
A seed crystal is immersed in this molten silicon and the seed crystal is pulled up to produce cylindrical single crystal silicon.

In the C2 method described above, a crucible made of quartz glass has conventionally been used. However, when a quartz glass crucible is used, the quartz glass and molten silicon react, and the reaction product is incorporated into the silicon crystal as an oxygen impurity. Oxygen impurities in silicon crystals cause crystal defects, which has the disadvantage of deteriorating the characteristics of manufactured integrated circuits.

In addition, as a method for manufacturing plate-shaped single crystal silicon, the EFG method (edg@d@fin@d film fe@d gr
owth method) is known. In this method, silicon raw material is melted in a furnace, one end of a hollow frame-shaped die is immersed in the molten silicon, and a plate-shaped seed crystal is placed in the molten silicon that rises through capillary action through the middle receiving part of the guide. By soaking and pulling up this seed crystal, a plate-shaped single crystal silicon crystal is produced.

In the above-mentioned EFG method, conventionally, a crucible with a quartz backing and a Gui made by Kagen have been used. However, the quartz glass crucible has the same drawbacks as the C2 method, and in addition, when Kamen-made Dai Kumquat is used, Kagen easily reacts with molten silicon to form silicon carbide, and such silicon carbide is difficult to use. If formed around the hollow part, there is a disadvantage that not only the silicon crystal is pulled up into a circular part, but also the silicon crystal becomes polycrystalline.

Therefore, the present inventors considered using jigs such as crucibles and gouers made of silicon nitride, which hardly reacts with molten silicon.
After depositing a crystalline silicon nitride film on at least one of the inner or outer surfaces of a base material having a desired shape by the CVD method, the base material is removed. A method of manufacturing is disclosed.

If a silicon nitride jig developed by the method described above is used to pull silicon crystal, it is possible to produce high-quality single crystal silicon with a low oxygen concentration in most cases.

However, depending on the manufacturing conditions, the silicon crystal may become polycrystalline even when using the silicon nitride jig manufactured by the method described above.

This is true for silicon nitride molds manufactured by depositing a thick crystalline silicon nitride film on the inner surface of the base material and then removing the base material.
This is especially noticeable when using friends.

As a result of various studies on the causes of polycrystallization of silicon crystals, the inventors of the present invention have found that the cause is as described below. When the silicon nitride film 2 is deposited on the surface of the base material 1,
Silicon nitride grows as shown in FIG. That is,
Since silicon nitride is initially deposited on the surface of the base material 1, which has a different nature, the growth of crystal grains is suppressed and the crystal grains are small.

Therefore, in the initial stage, silicon nitride grows in accordance with the surface shape of the base material 1.

Thereafter, as the growth progresses, the crystal grains become larger and the surface of the silicon nitride film 2 becomes more uneven.

This means that the inner surface of the base material 1 is coated with CVD as shown in FIG.
A silicon nitride screw 3 manufactured by depositing a crystalline silicon nitride film 2 (by a method) and then removing the base material 1 shows that its inner surface becomes extremely uneven. ing.

In particular, the surface roughness of the base material 1 becomes rougher and becomes more noticeable as the thickness of the silicon nitride film 2 on which it is coated becomes thicker.

If the silicon nitride crucible 3 having such a highly uneven inner surface is used for pulling silicon crystal, the surface area of the crucible 3 in contact with molten silicon increases. Because of this, Ruth? Silicon nitride of No. 3 becomes easier to dissolve in molten silicon. The silicon nitride dissolved in the molten silicon is deposited on the surface of the molten silicon as β-phase silicon nitride when the silicon crystal is pulled up, and incorporated into the silicon crystal ingot. The silicon nitride incorporated into the ingot causes dislocations to occur in the silicon crystal, so it is thought that the silicon crystal becomes polycrystalline. The above problem can be avoided by reducing the thickness of the silicon nitride film 2 because the surface roughness of the silicon nitride film 2 will not become rough, but in this case there is a slight problem in terms of mechanical strength.

On the other hand, as shown in FIG. 3, crystalline silicon nitride is deposited on the outer surface of the base material 1 by the CVD method! IX2'c The silicon nitride crucible 4 manufactured by removing the base material 1 after being subjected to observation can be manufactured by removing the base material 1 regardless of its wall thickness as long as the surface of the base material 1 is smooth. The inner surface will be smooth. 4 tons of silicon nitride crucible manufactured in this way? When used to pull silicon crystals, since the surface area of the lug 4 in contact with the molten silicon is not so large, the amount of silicon nitride dissolved in the molten silicon is small, and it precipitates on the molten silicon surface when the silicon crystal is pulled. Since there is also less β-phase silicon nitride, it is thought that the silicon crystal becomes single crystal rather than polycrystalline.

As described above, since it is possible to manufacture the product with a smooth inner surface of metal regardless of the wall thickness, it is possible to increase the wall thickness and provide sufficient mechanical strength.

In addition, when manufacturing a silicon nitride die metal by depositing crystalline silicon nitride on the outer surface of a plate-shaped base material by CVD and then removing the base material, If the base material is smooth, the same thing as described above can be said.

Based on the above investigation results, the present inventors deposited a crystalline silicon nitride film on the outer surface of a smooth base material of a desired shape by CVD method, and then removed the base material. We have discovered a method for manufacturing a silicon nitride jig for pulling single-crystal silicon that can pull high-quality single-crystal silicon.

The present invention will be explained in detail below.

Example 1 First, the surface roughness was Hmax according to JIS B 0601.
Glassy carmen base material with a shape of 15 μm
i A heater installed in the CVD reactor and arranged around the outer circumference of the CVD reactor keeps the temperature inside the CVD reactor at about 13
The temperature was raised to 60°C. Next, KSi in the CV'D reactor
CA4 gas and positive 5. fst-H, gas was supplied as a carrier gas. These gases reacted in the CVD reactor, and a crystalline silicon nitride film was deposited on the outer surface of the f-box-like carton base material (the inner surface of the base material was coated, so silicon nitride was not coated). After a predetermined period of time, the gas supply was stopped.

Subsequently, the glassy carmen base material was oxidized and removed at 600° C. to produce silicon nitride rutz with a thickness of 2000 μm.

JIS BO60 of the inner surface of the obtained silicon nitride nut
The surface roughness according to No. 1 and the crystalline state of the silicon crystal pulled using this method are shown in the table below.

Example 2.3 A base material was processed using a l-shaped lug car and YK lathe (Example 2), and the surface roughness of this base material was -ax 35μ
It was m. Further, the surface of this base material was roughened with 20φ sandpaper to obtain a T base material (Example 3). The surface roughness of this base material was 350 μm in terms of Hmax. below,
After depositing a crystalline silicon nitride film on the outer surface of these base materials under the same conditions as in Example 1, these base materials were oxidized and removed at 600°C to produce a 2000 μm thick silicon nitride film. did.

The surface roughness of the inner surface of the obtained silicon nitride nuts and the crystalline state of the silicon crystals pulled using these nuts! I″Ik is shown in the table below.

Example 4 Silicone was cast into a bottom mold with a wall thickness of 3.
It was used as a base material. The surface roughness of this base material was 56 μm in terms of Hmax. After depositing a crystalline silicon nitride backing on the outer surface of the silicon substrate under the same conditions as in Example 1,
The silicon base material was removed by exposing it to an HCt atmosphere to produce a 2000 μm thick silicon nitride root box.

The surface roughness of the inner surface of the obtained silicon nitride rutz and the crystalline state of the silicon crystal pulled using this nitride.
? Shown in the table below.

In addition, Comparative Examples 1 to 4 in the table below were obtained by depositing a crystalline silicon nitride film on the inner surface of the base material used in Examples 1 to 4 above by CVD method, and then removing each base material. These are the results for silicon nitride Ruth I produced by the method.

Table implementation f13 mN carnton i 350'
400 *Wlz% Comparative Example Am Oshikagen 350 1 450 Polycrystal 1 Meiman Example 4:
Silicon l 56, '65 Single crystal yield example 4 Silicon 56 520 Polycrystalline As is clear from the above table, a crystalline silicon nitride film was deposited on the outer surface of a smooth base material to produce it.Example 1 All of the silicon nitride nuts No. 4 to 4 had a small surface roughness on the inner surface, that is, the HmaxO value, and the silicon crystals pulled using these nuts were all single crystals. In contrast, Comparative Examples 1 to 4 were manufactured by depositing crystalline silicon nitride lI on the inner surface of the same base material as in Examples 1 to 4.
All of the silicon nitride crucibles have large HmaxO values, and when pulling silicon crystals using these crucibles, there is a large amount of β-phase silicon nitride precipitated on the molten silicon surface.
All of the pulled silicon crystals were polycrystalline.

Note that the degree of smoothness of the base material is preferably 350 μm or less in Hmax.

As described in detail above, according to the present invention, it is possible to provide a method for manufacturing a silicon nitride jig for pulling single crystal silicon that can consistently pull high quality single crystal silicon.

[Brief explanation of the drawing]

FIG. 1 is an explanatory view showing the growth state of silicon nitride, and FIGS. 2 and 3 are explanatory views showing a method for manufacturing silicon nitride fissures. Wooden Ruth I. Applicant's representative Patent attorney Takeshi Suzue Disciple Figure 1 Figure 2 Figure 3 Continued from page 1 > Inventor Hisashi Muraoka Tokyo Shibaura Electric Co., Ltd. Research Center, 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki City 0 Request Person Tokyo Shibaura Electric Co., Ltd. 72 Horikawa-cho, Saiwai-ku, Kawasaki City

Claims (2)

[Claims] (1) In manufacturing a jig used to pull columnar or plate-shaped single crystal silicon from molten silicon, a crystalline silicon nitride film is deposited on the outer surface of a smooth base material of the desired shape by the CVD method. A method for manufacturing a silicon nitride jig for pulling single crystal silicon, the method comprising: removing the base material. (2) The method for manufacturing a silicon nitride jig for pulling single crystal silicon according to claim 1, wherein the degree of smoothness of the base material is 350 μm or less in Hmthx as a t% sign.