JPS6123313A - Formation of mold-releasing layer for manufacturing disc of polycrystalline si wafer - Google Patents

Abstract

PURPOSE:To be scared to intermix a mold-releasing agent constitution into melt and to eliminate that a mold-releasing layer is injured by impact at the time of melt dripping by a method wherein a specific mold-releasing layer in which Si parent material melt is weak deposition on the surface of a manufacturing disc, when polycrystalline Si wafer is manufactured. CONSTITUTION:On the surface 1a of a manufacturing disc 1, where a parent material melt is flowed and supplied, mixed solution in which mold-releasing agent powder such as Si3N4, SiO, SiO2, SiC, BN and the like are mixed with solution is dissolved SiO2 concentration 1-5% in an organic solvent is applied, thereafter a mold-releasing agent A is formed by heat-solidification thereof. By this fact, the complete mold-releasing layer A is in a state of semi-solidification remaining powdery element, and is able to be prevented scattering of the mold-releasing powder. Thereby, the property and the quality of the Si wafer is kept and improved the trouble such as the crack of the mold-releasing layer is broken by dripping of melt so as not to be complete solidification.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a mold release agent for manufacturing plates of 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 is to obtain ingots by casting an ingot into a base material and then slicing it, but the slicing process is complicated and the material used during slicing is This resulted in large losses and high cost products, which were not comparable to mass production.

In addition, there are methods that do not involve slicing, such as the ribbon method and the casting method, but both have the disadvantage of not being able to obtain large solar cell materials, and in the casting method, silicon crystal grains are extremely thin. Since the crystal grains become so fine that large crystal grains cannot be obtained, the photoelectric conversion rate of the solar cell obtained with the sea urchin is also extremely poor at 2 to 3 inches.

Therefore, the present applicant has already developed a method for producing polycrystalline silicon (polycrystalline silicon) that can significantly improve the defects of the above-mentioned methods, by melting a silicon base material and using this melt as a polycrystalline silicon material. A thin layer of melt with a desired expanded diameter is formed by effectively utilizing centrifugal force, and after the layer solidifies, it is peeled off from the production plate (spin method). law) was proposed.

This spin method has many excellent features, but since the thin layer of melt adheres to the production plate, it is easy to break when the thin layer of melt is peeled off, and the work is complicated and requires skill. This has become a bottleneck for mass production.

In addition, since the above-mentioned molten silicon base material melt is directly dropped onto the production plate to form a thin layer of melt, the components of the production plate are likely to diffuse into the melt, and in particular, the four plates are made of carbon. In this case, 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 wafer as a product.

To solve this problem, we have already added powder 5t3N, + 5to2,5ill on both sides of the production pan.

A film is formed using a mold release agent such as SiC or BN, and a melt of the silicon base material is dropped on two sides of the inner film to form a thin layer of the melt.
It is also being solidified.

However, when such a mold release agent layer is used, the impact caused by dropping the melt of the silicon base material onto the production plate,
The mold release agent gets mixed into the melt, which not only tends to deteriorate the properties and quality of the silicon wafer product, but also causes the mold release agent layer to peel off and scatter due to the impact of the melt. In such places, there is a problem in that due to direct contact between the melt and the production plate, components of the production plate are mixed into the melt, causing crystal defects and deteriorating its properties and quality. Was.

Therefore, we dissolved silicone powder in an organic solvent, applied it to a production plate and dried it to form one layer of teeth, and then sputtered the same layer again to make a second layer of mold release agent. A release agent layer is also used, which is a layered layer of
According to this, although the defects in the powder layer can be improved by solidification, the work is complicated due to multilayer formation, and the mold release agent is solidified, so the silicon base material melt There was a problem in that the release agent layer cracked and peeled off when it was dropped.

[Problem that the invention seeks to solve]

The present invention has been made in view of the above-mentioned conventional circumstances, and involves dropping a melt of a silicon base material onto a production plate on which a mold release agent layer is formed on the upper surface to form a desired thin layer of the melt. When manufacturing polycrystalline silicon Uninow by peeling it off from the production plate after solidifying it, it is possible to eliminate the possibility that the mold release agent component will be mixed into the melt, and the mold release agent component will be removed by the impact during dropping. The purpose of the present invention is to provide a method for forming a mold release agent layer that can produce a polycrystalline silicon urethane 1 of high quality and high properties without damaging the polycrystalline silicon material.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention has an organic solvent containing Sulfur on the surface of a production tray to which a silicon base material melt is supplied flowing down.
In the solution in which iO2 was dissolved to a concentration of 1 to 5%,
S i3 N4, S to.

The method is characterized in that after applying the mixed solution in which mold release agent powders such as S i02 , S ic , BN, etc. are mixed, the solution is heated and solidified.

[For production]

In the present invention, by having the above-mentioned continuous structure, not only a solution of S i 02 in an organic solvent but also a mold release agent powder are mixed and placed on the production plate in a coexisting state, and this is heated, so that the finished product is The released mold release agent layer remains in a semi-solid state with powdery elements remaining.

That is, by mixing a mold release agent powder and using a solution of silicon oxide (Si02) in an organic solvent as a fixing material, the above-mentioned ready-made powder release can be achieved even when the melt of the silicon base material is dropped. It can prevent the mold agent from scattering, maintain and improve the properties and quality of the silicon wafer, and since it is not completely solidified, problems such as cracking of the mold release agent layer due to dripping of the melt are eliminated. It is possible to achieve the intended purpose.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail based on the drawings.

In Figures 1 and 2, numeral 1 is a production tray, which is made of a material such as quartz (Sin2) or carbon (C) that has little reactivity with silicon, and is made of a desired shape such as a circular polygon of various dimensions and used. Optionally select and use A with surface 1&.

Then, a mold release agent layer (A) according to the present invention is formed on the surface 1a of this production plate 1.

To form this mold release agent layer (A), silicon oxide (Sin) is first added to an organic solvent such as polyvinyl alcohol (PVA).
2) is dissolved to a concentration of 1 to 5.

Next, mold release agent powder is mixed into this solution.

The mixing ratio is 5g of mold release agent powder to 10CC of solution.
The powder is preferably S to, S
Silicon-based powders such as IC, Si3N4, etc. are suitable;
Moreover, BN etc. can also be used.

The thus obtained mixed solution containing a mold release agent is applied to the surface 1a of the production plate 1 using a brush or spray, and is dried at high temperature (approximately 600 C or higher) in a heating furnace. A desired mold release agent layer (A) is obtained.

In the production of polycrystalline/recon wafers, once the release agent layer (A) is formed on the surface 1a of the production plate 1 in this way, the production plate 1 is placed in the equipment shown in FIG. equipment.

That is, according to the equipment, the production tray 1 is placed in the collection tray 1o of the turntable mechanism 8, and is placed coaxially with the rotating shaft 9, and the collection tray 10 is synchronized by driving the rotating shaft 9. and rotated.

Next, a silicon base material is put into the crucible 4, heated and melted by the melting heat source 5, and the melt is discharged into the funnel 7 by rolling of the crucible 4, and is received by the funnel 7. The flowed liquid flows from the outflow lower ′ to the production pan 1 as shown by the dotted line in the figure.
It is placed in the mold release agent layer (A), and is dropped approximately at the center (Ac) of the mold release agent layer (A).

At this time, it is preferable to rotate the turntable mechanism 8 in advance, but the rotation may be started at the same time as the dropping, or after the dropping is completed and before the melt solidifies. The liquid flows in the direction of diameter expansion.

Then, this diameter-expanding flowing melt is applied to the mold release agent layer (A).
The diameter is expanded all over the entire surface of the plate, and the diameter is expanded to its outer periphery, and the excess supply of melt is discharged from the outer periphery by centrifugal force. The polycrystalline silicon wafer is formed on the mold release agent layer (A) of the production plate 1 by solidifying it as shown in the figure and by allowing it to cool naturally or by an appropriate cooling means.

The silicon base material used is metal-edge silicon, semiconductor grade high-purity silicon, etc., and the base material is melted by a heat source 6 for melting such as an electric heater disposed on the outer periphery of the crucible 4. Silicon melting temperature 1420℃
This can be melted by heating in consideration of the above, and of course, if the heating is stopped at an appropriate time, the heating conditions can be controlled.

Here, the reason why the concentration of silicon oxide (Si02) dissolved in the organic solvent in the present invention was specified as described above is because the concentration determines the purity of the polycrystalline silicon wafer, that is, its ratio. This is because resistance varies as shown in the table below.

As a result, to obtain high purity polycrystalline silicon wafers,
A silicon oxide (Si20) concentration of 1-5% has been found to be suitable.

In this way, the polycrystalline/
Once the recon wafer is solidified, the same layer is removed from the silicon wafer, but in this case, the degree of adhesion at the interface between the silicon wafer and the release agent layer is weak, so the wafer can be easily removed manually. It is peeled off.

〔Effect of the invention〕

As described above, according to the present invention, when manufacturing polycrystalline silicon wafers by the spin method etc., a mold release agent layer with weak weldability of the silicon base material melt is formed on the surface of the manufacturing plate. , the peeling work becomes simple and efficient,
There is no damage to the silicon wafer.

Furthermore, according to the present invention, since silicon oxide (SiO2) is used as the material for fixing the particles of the mold release agent powder, when the silicon oxide melt is dropped to form a thin layer of the melt, Unlike the conventional mold release agent powder layer, the powder does not scatter, and the surface of the production plate is inadvertently exposed. As a result, there is no fear that components from the metering device may be mixed into the recon wafer. It is possible to significantly improve the quality of product characteristics such as battery wafers, etc., and because it has a composition in which mold release agent powder and assimilated silicon oxide (Si02) coexist,
Unlike a completely solid material, it is resistant to the impact of pouring the silicon matrix melt, and therefore the release agent layer will not peel off due to damage, which also reduces the characteristics of the wafer. I don't have to worry about letting it happen.

[Brief explanation of drawings]

Figure 2 is a perspective explanatory view showing an example of a setup for manufacturing polycrystalline soric wafers using the manufacturing dish obtained according to the present invention.
The figure is a front explanatory view of a state in which a product is obtained on the same production plate. A...Mold release agent layer 1...Production plate 1a...Surface of production plate

Claims (2)

[Claims] (1) On the surface of the production tray into which the silicon base material melt is supplied, Si_3N_4, SiO, SiO_2, SiC, BN are added to the solution containing SiO_2 dissolved in an organic solvent to a concentration of 1 to 5%. A mold release for a polycrystalline silicon wafer production plate, characterized in that the mixed solution containing a mold release agent powder such as the above is applied and then fixed by heating to form a mold release agent layer. Formation method of agent layer. (2) The amount of mold release agent powder mixed in the solution is as follows:
A method for layering a release agent for a polycrystalline silicon wafer manufacturing dish according to claim 1, wherein the ratio is 5g to 0CC.