JPS6149416A - Coating method of carbon tray for manufacturing polycrystalline silicon wafer - Google Patents

Abstract

PURPOSE:To obtain a manufacturing tray having high strength against temperature and impact and a long durable period by forming a polysilicon film on the surface of a carbon tray by a known means, heating it in N2, and forming an SiC on te lower layer of the film and an SiN on the upper layer. CONSTITUTION:Approx. 2-3mum of a polysilicon film 2 is accumulated on the surface 1' of the carbon tray 1 by a CVD method or the like, and treated at 1,200-1,300 deg.C in N2 for approx 1hr. The C of the tray and the Si of the film are bonded to form an SiC film 3 on the lower layer of the film 2, N of the atmosphere and the Si of the film 2 are bonded to form an SiN4 film on the upper layer. Since they are chemical bonds, a coating being rigid and extremely hard to separate is completed. According to this method, the purpose can be performed by the film of 2-3mum thick to provide twice as high as the conventional one for durable period until a partial separation occurs.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of coating a carbon plate used for producing polycrystalline silicon wafers used in solar cells and other photoelectric conversion elements.

[Conventional technology]

Conventionally, polycrystalline silicon wafers have been manufactured by various methods, but they have had various problems.

In other words, the most common ingot method involves casting an ingot on a silicon base material and then slicing it to obtain wafers. However, the slicing process is complicated and there is a large loss of material during slicing. Unfortunately, the product was expensive and not suitable for mass production.

・In addition, the ribbon method and casting method (@Synthesis method) are considered as methods that do not involve slicing, but both have the disadvantage that large solar cell materials cannot be obtained, and furthermore, the casting method has the disadvantage that silicon Since the crystal grains become very fine and large crystal grains cannot be obtained, the wafer has a defect that the photoelectric conversion rate of the solar cell obtained is extremely poor at 2 to 3%.

Therefore, the present applicant has developed a method for manufacturing polycrystalline silicon wafers that can significantly improve the defects of the above methods.
The silicon base material is already melted, and this melt is dropped onto a rotating production plate made of quartz or carbon, and by effectively utilizing centrifugal force, a thin layer of the melt with the desired diameter expansion is created. We proposed a method (spin method) in which the same layer is formed, solidified, and then peeled off from the manufacturing device.

This spin method has many excellent features, but since the above-mentioned molten silicon base material solution is directly dropped into the manufacturing device to form a thin layer of melt, the manufacturing device These components tend to diffuse easily, and especially when carbon is used in this country, there is a problem in that carbon is mixed into the melt as a contaminating impurity and has an adverse effect on the characteristics of the product wafer.

Therefore, in order to solve this problem, it has already been proposed to sequentially form a double film layer of SiC and SiN on the surface of carbon manufacturing equipment. If the molten silicon base material solution is dropped and the polycrystalline silicon material is produced as described above, the carbon plate crab bon is produced as follows: 1. It has also been confirmed that it is possible to very effectively prevent Ω from entering the JR product Silico X Ueno K.

However, in the conventional method of coating a carbon plate with the above-mentioned double film layer, the surface of the carbon plate is first coated with a CVD method.
After forming a SiC film by employing a known method such as sputtering or vacuum evaporation, SiNMk is then formed on the surface of the SiC film by means such as the above-mentioned CVD method.

Therefore, when using this conventional method, the SiC film is
The m5sxN film must be stacked to a considerable thickness of about IO μm, so it is necessary to use that much raw material, and when adopting the CVD method etc., the material must be replaced from SiC to SiN. from,
Of course, it is necessary to spend about 30 hours on the coating, and the SiC film mentioned above is % of the carbon in the carbon plate. Because of this, when used under high temperature conditions during silicon wafer manufacturing, it tends to peel off easily, and it can withstand only about 10 uses before it eventually becomes partially peeled off.

[Problem that the invention seeks to solve]

The present invention has been made in view of the above-mentioned conventional circumstances, and involves passing a melt of a silicon base material down onto a production plate on which a release agent layer is formed on the upper surface to form a thin layer of the melt. When manufacturing a polycrystalline silicon wafer by forming a polycrystalline silicon wafer by forming a polycrystalline silicon wafer and peeling it off from a manufacturing device after completely solidifying it, SiC and SiH films are not simply stacked in an adhesive state as in the conventional method, but are A double layer of SiC and SiN is formed integrally in a chemically bonded state, which reduces the time required for coating and allows the layer thickness to be formed thinner than that of conventional methods. The aim is to improve the service life by more than double based on the physical bonding, thereby making it possible to produce polycrystalline silicon wafers of high quality and properties.

[Means for solving problems]

In order to achieve the above object, the present invention first applies a CVD method to the surface of a carbon plate to which a silicon base material melt is supplied.
A polycrystalline silicon film is formed by known means such as sputtering or vacuum evaporation, and then heated in a nitrogen atmosphere to coat the lower layer of the silicon film with C in a 7-fiber plate. A polycrystalline silicon urethane/carbon for manufacturing, characterized in that an SiC layer is formed by N in the atmosphere and 81 in the silicon film, and an SiN layer is formed in the upper layer by N in the atmosphere and 81 in the silicon film. The present invention provides a method for coating dishes.

[For production]

In the present invention, the interface between the carbon plate and the SiC layer and the interface between the SiC layer and the SiN layer are not simply bonded, but are chemically bonded through the edge heat treatment, so they are resistant to temperature and impact and have a long-term lifespan. Can withstand repeated use.

〔Example〕

To explain the present invention in detail with reference to the drawings, first, a polycrystalline silicon film 2 is formed and grown on the surface 1' of a carbon plate 1 shaped like a disk. Known CVD method, sputtering method,
A vacuum evaporation method or the like may be used, and the film thickness may be about 2 to 3 μm.

Next, the carbon plate 1 with the silicon film 2 formed thereon as described above is heated in an indoor atmosphere A.
However, the heating conditions are 1200 to 1300
It is desirable that the treatment be carried out at a temperature of about 0.degree. C. for about 1 hour.

Through the above heat treatment, C of the carbon plate 1 and Si of the silicon film 2 are chemically bonded, and the lower layer of the interlayer 2 has S.
An i0 layer 3 and an SiN layer 4 formed by chemical bonding of N in the nitrogen atmosphere A and Si in the silicon film 2 are formed on the upper layer of the film 2, respectively.

Therefore, the interface between the carbon plate 1 and the Si0 layer 3 and the interface between the SiC layer 3 and the SiN layer 4 are chemically bonded, and therefore the bond is strong and a complete coating is formed that is extremely difficult to peel off. I was able to do that.

〔Effect of the invention〕

Since the present invention has the above-mentioned configuration and can be implemented as in the above embodiments, it is possible to achieve the objective with a coating thickness of 2 to 3 μm, which is about 1/3 to 115 of the conventional example, and The coating can be completed in about 24 hours, compared to about 30 hours with the conventional method, which not only improves productivity, but also reduces encirclement resistance until partial peeling occurs. The lifetime of the polycrystalline silicon wafer produced using the carbon plate obtained according to the present invention, which is a barometer of quality, is 2μBec, which is twice that of the conventional example. It was confirmed that high quality Ueno 1 products are available.

[Brief explanation of the drawing]

Fig. 1 is a partially longitudinal front explanatory view showing the carbon plate after the initial process is completed in the method of coating a carbon plate according to the present invention, and Fig. 2 is a partially longitudinal front view showing the carbon plate after completing the four steps. It is an explanatory diagram. 1-...0 force-Bon plate body 1'...Surface of carbon plate intangible 2--Silicon film 3--eSiC layer 4--SiN layer A...・Nitrogen atmosphere agent Yoshio Saito, patent attorney Figure 1 Figure 2

Claims (2)

[Claims] (1) First, a polycrystalline silicon film is formed on the surface of the carbon plate to which the silicon base material melt is supplied by known means such as CVD, sputtering, or vacuum evaporation, and then this is deposited in a nitrogen atmosphere. By heating inside the silicon film, the C in the carbon dish and the Si in the silicon film are combined with the lower layer of the silicon film.
1. A method of coating a carbon plate for manufacturing a polycrystalline silicon wafer, characterized in that an SiC layer is formed by the above-mentioned N in the atmosphere and a SiN layer is formed in the upper layer by the N in the atmosphere and the Si in the silicon film. (2) The method for coating a carbon dish for producing polycrystalline silicon wafers according to claim 1, wherein the heating conditions are 1200 to 1300°C for about 1 hour.