JPS59182218A - Production of polycrystal silicon wafer - Google Patents

Abstract

PURPOSE:To obtain easily the titled wafer having high quality and characteristics without fear for contamination of a release agent nor components of a production dish in a melt, by forming a thin melt layer on a release agent layer, formed on the top of the production dish, and consisting of a silicon based powder layer. CONSTITUTION:A silicon based powder layer 2 (release agent layer) is left and formed on a plane for forming a wafer of a production dish 1 by applying a release agent formed by dissolving silicon based powder in an organic solvent, heating and drying the release agent. The production dish 1 having the release agent layer 2' formed thereon is placed on a recovery pan 10 of a turntable mechanism 8, and a silicon base material melt is dropped onto the center thereof. A thin melt layer 3 is formed on the whole top surface of a plane (1a) for forming a wafer by centrifugal force, cooled, solidified and peeled to give the aimed silicon sheet 3'. Thus, the aimed polycrystal silicon wafer having high quality and characteristics can be easily obtained without fear of contamination of the release agent nor components of the production dish 1 in the melt.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing polycrystalline silicon sea urchin used in solar cells and other photoelectric conversion elements.

Conventionally, polycrystalline silicon wafers have been manufactured by various methods, and the most common method is to cast an ingot of a predetermined shape from a silicon base material and then obtain wafers by slicing the ingot. In this case, not only does the slicing process take a lot of time, but also about 50% of the ingot is lost during slicing, making the product expensive and making mass production impossible.

Therefore, the ribbon method and the casting method (casting method) have already been implemented as methods that do not involve slicing, but the ribbon method, for example, jets molten silicon onto the circumferential surface of a rotating drum and forms a ribbon-shaped wafer on the circumferential surface. and
When using this method, it is practically impossible to manufacture ribbons with a ribbon width of several mm, and large solar cells, etc.
There is a problem with not being able to do it.

In addition, in the above-mentioned gearing method, the silicon matrix is heated to form a melt.1-1 This is poured into a mold according to the dimensions of the product wafer, and the movable parts of the mold are used to turn the melt into a melt. When this method is used, a wafer of a predetermined shape is moved around at once, and desirable results can be expected in terms of mass production.As mentioned above, the melt is poured from all sides. You will be held down.

Therefore, in this method, when the upper and lower surfaces and side surfaces of the mold assimilate the above-mentioned melt, the growth of crystal grains (grains) is suppressed, and the vicinity of the parts of the assimilated product in contact with each surface of the mold is However, since the crystal grains become very fine and large crystal grains cannot be removed, it is not possible to satisfy the requirement of large crystal grain generation, which is considered desirable for solar cells/recon wafers, etc. The charging conversion efficiency of the solar cells thus 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 matrix 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 melt with a desired diameter expansion is created. We proposed a method (spin method) in which a layer is formed, and after the same layer is solidified, it is formed into a splinter 1 from a manufacturing device.

This spin method has many excellent features, but when the thin layer of solidified melt is peeled off, the layer adheres to the manufacturing device and is easily damaged during the peeling process. This work was extremely complicated and required great skill, which created a bottleneck in mass production.

In addition, according to this method, the melt of the molten silicon matrix is directly dropped into the manufacturing device to form a thin layer of the melt.
Components of the manufacturing equipment are likely to diffuse into the melt, and especially if the manufacturing equipment is made of carbon, this carbon will be mixed into the melt as a contaminating impurity and will have a negative impact on the characteristics of the product wafer. There was a problem.

In order to solve this problem, conventional methods used silicon nitride as a solvent and volatile solvent as a solution to be applied as a mold release agent to two surfaces of the manufacturing device, thereby forming a film of several microns on the top surface of the manufacturing device. The above problem was solved by dropping a silicon matrix solution onto the upper surface of the interlayer to form a thin layer of melt and solidifying it.

However, in the method of applying such a mold release agent to the manufacturing device/separating the release agent from the manufacturing device, it is necessary to simply apply a solution in which the mold release agent is dissolved to the manufacturing device. -1, due to the impact when the melt of /recon mother 14 was dropped into the manufacturing device, 1
Not only is it easy for the properties and quality of the silicon wafer to deteriorate due to the mixing of type 11 agent, but also that the agent is peeled off due to the same impact.
At the point where the melt is scattered, the melt and the manufacturing device end up coming into direct contact, and components from the manufacturing device are mixed into the melt, causing crystal defects, which deteriorates its properties and quality. There was a problem that the

This invention was devised in view of the current situation, and its purpose is to: - Drop a melt of silicon matrix onto the top surface of a manufacturing device to form a thin layer of melt of a desired size; When manufacturing polycrystalline silicone sea urchin by peeling it from the manufacturing equipment after solidifying it, there is no risk of the mold release agent or components of the manufacturing equipment being mixed into the melt, resulting in high quality and high properties. It is an object of the present invention to provide a method for manufacturing polycrystalline silicon wafers that can easily obtain polycrystalline silicon wafers.

In order to achieve such an object, the present invention has a method in which the melt of the silicon base material on a rotating production plate in a desired atmosphere is made to flow in the direction of diameter expansion by the centrifugal force caused by the rotation. , a polycrystalline silicon wafer manufacturing method in which a thin melt layer of a desired diameter is formed by the melt, solidified, and then the thin layer is peeled off from a manufacturing device, in which the wafer forming plane of the manufacturing device is , a mold release agent produced by dissolving silicon-based powder with an organic solvent is applied, and then the manufacturing device is heated at a required temperature to dry the organic solvent, thereby forming a remaining silicon-based powder layer. The thin melt layer is formed on the silicon-based powder layer.

Hereinafter, the present invention will be described in detail based on the embodiments shown in the accompanying drawings.

FIG. 1 shows a state in which a mold release agent (2) has been applied to the wafer forming plane (1a) of the manufacturing device (1).

The manufacturing device (1) contains quartz (which has little reactivity with silicon).
Materials such as SiCh) and carbon (c) having wafer forming planes (1a) of desired shapes such as circular and rectangular shapes of various sizes are prepared, and any of these can be selected and used.

In addition, polyvinyl alcohol (PVA) is used as a mold release agent).
), etc., is used, and silicon oxide or silicon nitride is suitable as the powder.

The use of silicon powder as a mold release agent in this way is
This is because it is a similar material to the silicon matrix, so it has little reactivity with the silicon sheet, and it is easily solidified by heating.

Next, the mold release agent (2) obtained as described above was added to the manufacturing device (1).
), but this can be done by brush or spray method, and after such application process, this manufacturing device (1)
is heated to a required temperature in a heating furnace, and the temperature in this case is preferably 600°C or higher.

Due to this heating, the organic solvent of the mold release agent (1) dries, and the upper surface of the manufacturing device (1), that is, the wafer forming plane (1a), is dried.
), a silicon-based powder layer remains formed, and the thickness of the powder layer is preferably about 200 μm.

In this way, after the silicon-based powder layer d is formed in the manufacturing device, a thin layer of melt with a desired expanded diameter is formed on the upper surface of the powder layer. The process of forming θ will be explained below with reference to FIG.

The silicon base material is put into the crucible (4) shown in the same figure, the dirt is heated and melted by the melting heat source (5), and the melt is put into the crucible (4).
) is discharged into the funnel (7), where it is received by the phlegm funnel (7), and then from the outlet (7).
As shown by the dotted line in the figure, the melt is applied to the wafer forming plane (1a
) to approximately the center of the area.

At this time, it is preferable to rotate the turntable mechanism (8) in advance, but the rotation may be started at the same time or before the melt solidifies after the dropping is completed, and the centrifugal force caused by the rotation causes the melt to flows in the direction of diameter expansion. and,
This diameter-expanding flowing melt is expanded over the entire surface of the wafer forming plane (1a) to its outer periphery, and the excess supply of melt is discharged from the outer periphery by centrifugal force, resulting in a change in the wafer forming plane Oa). A thin melt layer (3) matching the shape is formed, and this is solidified by natural cooling and an appropriate cooling means, and as shown in FIG. (1a).

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 (5) such as an electric heater placed on the outer periphery of the crucible. , the melting temperature of the silicon 1420
It is possible to melt this by heating with the temperature in mind.The heat source (5) can be a heating wire as shown in the example, or a high-frequency heating device, and of course, it can be heated at appropriate times. It is desirable to be able to stop the heating or control the heating conditions.

Further, the turntable mechanism (8) has its rotating shaft (
The manufacturing device (1) is placed on a collection tray (10) fixed to the container 9), and the collection tray (10) and the manufacturing device el) are rotated synchronously about the coaxial shaft (9).

In this way, the wafer forming plane (1a) of the manufacturing device (1)
After 7 recontents (2) with a desired diameter expansion are formed, the silicone sheet (2) is peeled off from the manufacturing device (1).

In this S combination, a solidified silicon powder layer 2 is interposed between the manufacturing device (1) and the silicon sheet d, and
Since the powder layer d exerts a mold release effect, the adhesion at the interface between the powder layer d and the silicon sheet (=E4) is weak.
As a result, the silicone sheet d can be easily peeled off from the powder layer d by hand.

As described above, according to the present invention, the difficulties of the conventional ingot slicing method and ribbon method can be solved, and the manufacturing device can be In addition, a layer of silicon-based powder is formed on the wafer forming plane of the turntable by heating and solidifying, and the silicon sheet is formed on the top surface of the same powder layer that has a mold release effect. It can be easily peeled off from the manufacturing device, and as a result, it is easy to work on the pricked portion, and the silicone sheet is not damaged.

Further, according to the present invention, a silicon powder layer, which is similar to the silicon base material, is formed between the silicon sheet and the manufacturing device as a mold release agent, and the silicon base material melt is hardened. There is no problem such as the mold release agent scattering due to dropping of the liquid and direct contact between the melt and the manufacturing equipment, and as a result,
Since components from the manufacturing equipment do not mix into the melt, it is possible to obtain polycrystalline silicon wafers with high characteristics and high quality.
Furthermore, there is no adverse effect on the wafer due to the release agent layer.

[Brief explanation of the drawing]

The drawings show an embodiment of the manufacturing method according to the present invention, in which FIG. 1 is a front explanatory view of the manufacturing device with a mold release agent applied to the top surface, and FIG. Fig. 3 is a front perspective view showing an example of equipment for manufacturing polycrystalline silicon wafers, and Fig. 4 is a front view showing a state in which a silicon-based powder layer is formed by heating with the same equipment. FIG. 15 is a front explanatory view showing the state in which the wafer is formed, and FIG. 15 is a front explanatory view showing the state in which the wafer is peeled off from the manufacturing device. (1)...Producer (1a)...Wafer forming plane■...For mold release agent)...Silicon powder layer■...Thin layer of melt ■・・・Silicone sheet patent applicant representative Patent attorney Makoto Ifuji Figure 3 4 Single 4 Figure 5

Claims (2)

[Claims] (1) In a desired atmosphere, the melt of the silicon base material on a rotating production plate is made to flow in the direction of diameter expansion due to the centrifugal force caused by the rotation, thereby thinning the melt to a desired diameter. In a method for producing polycrystalline silicon wafers in which a layer is formed, solidified, and then the same thin layer is peeled off from a production plate, the wafer forming plane of the production plate is coated with silicon powder produced by dissolving silicon-based powder with an organic solvent. A mold release agent is applied, and then the manufactured film is heated at a required temperature to dry the organic agent, thereby forming a remaining silicon-based powder layer, and the melt thin layer is formed on this Noriko/based powder layer. A method for manufacturing a polycrystalline silicon wafer, characterized in that: (2) The method for producing a polycrystalline silicon wafer according to claim 1, wherein silicon oxide or silicon nitride is used as the silicon-based powder, and the organic solvent is dried at about 600°C.