JPH079888B2 - Method for manufacturing polycrystalline silicon thin film substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to the production of polycrystalline silicon wafers used for solar cells and other photoelectric conversion elements, etc. by the centrifugal force based on the rotation of a turntable. The present invention relates to an improvement of a so-called spin method in which a resin is poured into a mold, that is, a mold and solidified.

<< Prior Art >> A known method for manufacturing a polycrystalline silicon wafer by a spin method is to place a lower plate b on a turntable a and an upper plate c on it as shown in FIG. , A cavity e is formed in a casting mold d formed by both plates b and c, and these are placed in an inert gas atmosphere, and an injection port f opened at the axial center position of the cavity e in the turntable a, Molten silicon g is injected, and this is turned table a.
The cavity e is filled with the centrifugal force generated by the rotation of the.

In the casting mold d shown here, the upper plate c as shown in FIG.
The injection port f is opened at the center of the lower plate, and four molding grooves b1, b2, b3, b4 are connected to the upper surface of the lower plate b by a cross-shaped inflow groove b5, and four molding grooves are formed at a time. It is now possible to manufacture polycrystalline silicon wafers.

However, in the case of the above spin method, when forming a thin polycrystalline silicon wafer by reducing the thickness of the cavity, it is necessary to have a considerable thickness since it will be damaged during the device processing. As a result, the silicon raw material is also considerably consumed and the wafer becomes expensive, and the silicon raw material cost occupies 80% of the price at present.

Further, in order to manufacture a solar cell or the like, since electrodes are formed on the above-mentioned polycrystalline silicon wafer, it is necessary to separately process the wafer, and the wafer is damaged in this step.

Further, since the casting mold d is filled with the molten silicon g, the upper plate b and the lower plate c formed of carbon, for example, are coated with silicon nitride so that the molten silicon g does not adhere thereto. It must be applied sufficiently, and if it has peeled off, the coating process must be repeated, and if the production peeling from the casting mold d is still difficult, the product There is a drawback that it may damage the.

<< Problems to be Solved by the Invention >> The present invention is intended to solve the drawbacks of the above-mentioned conventional methods, and a backing substrate formed in advance by a metal material of an inexpensive metal or alloy in the lower plate of the casting mold described above. A product in which an extremely thin film of polycrystalline silicon is consolidated and formed on the backing substrate by placing molten silicon in the narrow space of the casting die left on the substrate by centrifugal force. In order to obtain a product with a low unit price, it is possible to eliminate the possibility of damaging this even in the subsequent device processing and to make the handling processing easy and quick. At the same time, the purpose is to make the backing substrate usable as an electrode as a solar cell as it is so as not to separately form the electrode.

<Means for Solving the Problems> In order to achieve the above object, the present invention places the molten silicon obtained by melting the silicon base material in an inert atmosphere on a turntable in the same atmosphere. The mold module lower plate and the mold module upper plate placed on the mold module upper plate are supplied into the cavity of the mold through the injection port opened at the center of the turntable, and the molten silicon is supplied in advance to the mold module lower plate. Molded module top backing substrate made of cheap metal material placed on the plate The narrow cavity left between the plate and the mold is filled by the centrifugal force accompanying the rotation of the turntable, and solidified to fill the backing substrate. A polycrystalline silicon thin film characterized by being formed by consolidating a polycrystalline silicon thin film on a substrate, and detached from the cavity. It is intended to provide a method for manufacturing a substrate.

<Operation> In the present invention, since the backing substrate made of an inexpensive metal material is placed in advance on the mold module lower tray, only in the narrow cavity between this and the mold module lower tray, due to the centrifugal force due to the rotation of the turntable. Molten silicon
The product is quickly filled, so that a product in which molten silicon is solidified on the backing substrate is obtained, a substrate having an extremely thin polycrystalline silicon thin film which is not easily damaged, is obtained, and peeling from the mold is facilitated.

<< Examples >> The present invention will be described in detail with reference to the illustrated examples. FIG. 1 shows a manufacturing apparatus that can be used to carry out the method. Furnace body 1
Includes a rolling crucible 3 heated by a heater 2, a funnel 4, and a heater 5 and a turntable 6 below it.
The mold 7 is placed on the turntable 6.

Here, in the mold 7, a cavity 7c is formed by a mold module lower plate 7a on the turntable 6 and a mold module upper plate 7b stacked on the mold module lower plate 7a, and at the center position of the mold module upper plate 7b. entrance
The opening 7d is formed so as to communicate with the cavity 7c.

Therefore, in order to carry out the present invention using the above manufacturing apparatus, the silicon base material is stored in the rolling crucible 3 in advance, and the injection port 7d is aligned with the axis of the turntable 6. When the mold 7 is placed, the backing substrate 8 is placed on the mold module lower plate 7a in a fitted state, thereby narrowing the cavity 7c in the mold 7 to reduce the backing substrate 8 and the mold module. The narrow cavity 7c 'is left between it and the upper plate 7b.

Here, the backing substrate 8 is formed of a metal material which is cheaper than silicon such as iron and stainless steel, and the mold 7 is made of carbon and the one coated with silicon nitride is used. The thickness of the backing substrate 8 is actually 0.5 mm, and the thickness of the cavity 7c is
It was set to 0.6 mm.

After the furnace body 1 is operated and the heater 2 melts the silicon base material in the rolling crucible 3, the silicon base material in the funnel 4 is rotated by rotating the silicon base material around the axial center point 3a. The silicon Si is allowed to flow down, and the silicon Si is injected from the funnel 4 into the injection port 7d of the mold 7. At this time, the turntable 6 is rotated.

At this time, the mold 7 is actually heated by the heater 5 to about 1400 ° C., and the molten silicon Si of 1450 ° C. (melting point) is injected into the mold 7, and the turntable 6 is rotated at 400 rpm. did.

The molten silicon Si thus injected is on the backing substrate 8 by the centrifugal force F generated by the turntable 6 and flows into the narrow cavity 7c ', and then enters the narrow cavity 7c' as shown in FIG. 2 (b). Once filled, the heating by the heater 5 is stopped and the material is cooled and solidified, whereby a polycrystalline silicon thin film substrate 10 which is a product having a polycrystalline silicon thin film 9 formed by crystal growth on the backing substrate 8 is formed. The obtained polycrystalline silicon thin film 9 had a thickness of 0.1 mm in the above-mentioned specific example.

Of course, the polycrystalline silicon thin film substrate 10 is shown in FIG. 2 (c).
After the mold module upper plate 7b is opened as described above, it is taken out from the mold 7.

<< Effect of the Invention >> Since the present invention is configured as described above,
An extremely thin polycrystalline silicon thin film can be formed without labor,
Since the backing substrate made of an inexpensive metal material occupies a considerable part of the polycrystalline silicon thin film substrate as a product, not only it is possible to provide an inexpensive product but also this manufacturing process. Since the backing substrate will be formed in, the above-mentioned backing substrate can be used as an electrode without forming an electrode during device processing of a solar cell or the like, so that the device processing becomes easy and various processes can be performed. It was also confirmed that the extremely thin crystalline silicon thin film could be damaged by the presence of the backing substrate, and the lifetime of the product was 4 μsec or more, so that it could be sufficiently used as a solar cell.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view showing an example of a manufacturing apparatus that can be used to carry out the method according to the present invention, and FIGS. FIG. 3 is a partial vertical sectional front view of the mold showing the consolidation process, FIG. 3 is a vertical sectional front view showing the vicinity of the casting die of the conventional spinning method manufacturing apparatus, and FIG. 4 is a plan view showing the upper tray of the same casting die. 5 (a) and 5 (b) are respectively a plan view and a vertical front view showing the lower tray of the same type. 1a …… Inert atmosphere 6 …… Turntable 7 …… Mold 7a …… Mold module lower plate 7b …… Mold module upper plate 7c …… Cavity 7c ′ …… Narrow cavity 8 …… Backing substrate 9 …… Polycrystalline silicon Thin-film Si ... Molten silicon F ... Centrifugal force

Claims (1)

[Claims] 1. A mold module lower tray in which molten silicon obtained by melting a silicon base material in an inert atmosphere is placed on a turntable in the same atmosphere, and a mold module placed on the lower tray. The molten silicon is supplied into the mold cavity consisting of the upper plate from the injection port opened at the axial center of the turntable, and the molten silicon is preliminarily placed on the lower plate of the mold module, and the backing substrate is made of an inexpensive metal material. A narrow cavity left between the mold module upper plate and the mold cavity is filled with the centrifugal force associated with the rotation of the turntable, and solidified to form a polycrystalline silicon thin film on the backing substrate. A method for manufacturing a polycrystalline silicon thin film substrate, characterized in that it is separated from the cavity.