JPS6364909A - Production of silicon thin plate for solar cell - Google Patents

Abstract

PURPOSE:To directly obtain the titled thin plate from a molten state in good yield, by melting polycrystalline silicon fed above a water-cooled copper hearth with an electron gun, feeding the molten silicon into the hearth, sticking the molten silicon onto a water-cooled rotating drum and winding up the resultant silicon strip. CONSTITUTION:Polycrystalline silicon 1 in the form of a rod, etc., is horizontally fed onto a water-cooled copper hearth 2 in a device for producing the titled thin plate provided in a vacuum vessel at a constant speed and the tip part thereof is placed above the hearth 2 and melted with an electron gun 3 to feed proplets into the hearth 2. The droplets are subsequently melted with the electron gun 3 to give molten silicon 8, which is made to stick to a water- cooled rotating drum 4 having lateral stripes 7 of 0.1-0.3mm width at a regular interval, coagulated and wound upward to provide a silicon thin plate 5. The resultant silicon thin plate 5 is peeled from the drum 4 with a scraper 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Applications] This invention relates to a method for efficiently manufacturing silicon thin plates for solar cells.

[Conventional technology]

A conventional method for manufacturing silicon wafers for solar cells is shown in FIG.

First, polycrystalline silicon (99
, 99999999X) is basically a process of synthesis and precipitation.

Typical synthesis reactions and precipitation reactions are shown below.

(Synthesis reaction) S i + 3 Hc 1 → S i H
c l s 10 Hz (precipitation reaction) S IHC13+H
The x→S i +3 Hc 1 precipitation reaction is carried out on a red-hot silicon core rod through an electric current, and a so-called CVD (Chemical Vapor Depot) is applied to the surface of the red-hot silicon rod.
The Siemens method, in which silicon is precipitated to obtain rod-shaped polycrystals, is commonly used.

Next, the method for manufacturing silicon single crystal from polycrystal is FZ.
There are two methods: the floating zone method and the CZ method (pulling method).

As shown in Figure 6, the FZ method melts a floating zone in argon or vacuum using high-frequency heating, and the CZ method melts a single crystal from a quartz crucible in a graphite heater as shown in Figure 7. This is a method of growing a single crystal by pulling it upward using the seed as a nucleus.

Next, the obtained single crystal has a thickness of about 0.0 mm, as shown in FIG.
Cut into 5 pieces thick. At this time, the cutting and polishing allowance is approximately 0.5a+m, and in the end, one piece of silicon single crystal for solar cells of 0.5- is obtained from a silicon single crystal of 1+lll11, and the yield is approximately 5 pieces. .

In addition, if you polish it thinner than this, it will break, so 0.5
The limit is the level of ability.

On the other hand, in reality, the thickness of Si wafer for solar cells is O,1
If a 0.1 mm thick Si film can be obtained instead of the conventional method, the yield will be 10 times that of the conventional method.

Also, it is difficult to manufacture large diameter wafers using conventional methods.
The maximum diameter that can be obtained is approximately 00 mφ.

[Problem that the invention seeks to solve]

The conventional method for manufacturing silicon wafers for solar cells has a yield of 50X, and if a 0.1 m thin silicon plate can be directly manufactured, the yield will be 10 times that of the conventional method.

In view of the above-mentioned prior art, the present invention provides zero
．． The object of the present invention is to provide a method for manufacturing a silicon thin plate for solar cells, which yields a silicon thin plate with a thickness of 1 m.

[Means for solving problems]

The present invention has been made to achieve the above object.

That is, the present invention rotates a water-cooled rotary drum whose axis is approximately horizontal within a vacuum device at a predetermined circumferential speed, and a polycrystalline silicon bar is horizontally or The tip of polycrystalline silicon is fed vertically, the tip is melted with an electron gun, and then injected dropwise into a water-cooled copper hearth.Alternatively, polycrystalline silicon is continuously fed into the hearth, and this is melted with an electron gun, resulting in water-cooled silicon. This is a method for manufacturing a thin silicon plate for solar cells, which involves manufacturing a thin silicon plate by depositing molten silicon in a copper hearth onto the water-cooled rotating drum and rolling it up.

Further, it is preferable that the surface of the water-cooled rotating drum used in the method of the present invention is provided with striped grooves or protrusions.

[Effect]

In the method of the present invention, melting is performed in a high vacuum and high temperature using an electron gun as a heating source and a long beam, and scouring is performed in a water-cooled steel hearth, producing a silicon thin sheet with higher purity than relatively low-grade metallic silicon. is obtained. Further, by providing horizontal striped grooves, vertical grooves, striped protrusions, etc. on the surface of the water-cooled rotating drum, the thin silicon plate can be easily peeled off and a long plate can be manufactured.

The following embodiments of the present invention will be described.

〔Example〕

Next, the method of this invention will be explained with reference to the drawings.

Figure 1 shows one implementation of this invention method! ? ! FIG.

Rod-shaped polycrystalline silicon 1 is fed horizontally (or vertically) at a constant speed onto a water-cooled copper hearth 2 in a vacuum container (not shown). This tip is melted by an electron gun installed above, and the droplets are injected into the water-cooled copper hearth 2 below.

A water-cooled rotary drum 4 is installed adjacent to this water-cooled steel core 2, and this rotates in the direction of the arrow in the figure, and molten silicon 8 adheres to and solidifies on this drum 4 and is rolled upward. . The rolled-up silicon thin plate 5 is peeled off from the water-cooled rotating drum 4 by a scraper 6.

Generally, silicon thin plates are brittle and may break, making it difficult to manufacture long continuous thin plates. Therefore, 0.1 to 0.3 m of water is placed on the water-cooled rotating drum 4 in advance.
Horizontal striped grooves or protrusions 7 as shown in Figure 2 of approximately s
are attached at regular intervals, and the thickness of the silicon thin plate in this part is thinner than in other parts (by doing so, when it is peeled off from the water-cooled rotating drum 4 by the scraper 6, it can be made to break from this thin part. preferable.

In the method of the present invention, as shown in FIG. 3, it is necessary to sufficiently irradiate the area A where the water-cooled rotating drum 4 and the silicon bath 8 are in direct contact with each other using the electron gun 3. This prevents the solidified shell 9 in the water-cooled steel hearth 2 from connecting with the solidified shell 9 on the water-cooled rotating drum 4, and allows the solidified shell 9 on the water-cooled rotating drum 4 to be raised stably.

As shown in FIG. 4, if the area in A section where the water-cooled rotating drum 4 and the silicone bath are in direct contact is not sufficiently irradiated, the solidified shell 9 in the water-cooled copper hearth 2 and the solidified shell 9 on the water-cooled drum 4 may be connected. I was unable to raise the turret in a stable manner.

For the above reasons, it is essential to irradiate part A with the electron gun 3, and the irradiation must be performed with high positional accuracy. Therefore,
It is not suitable to use a plasma torch as a heating source.

FIG. 2 is an explanatory diagram showing another embodiment of the method of the present invention. In a vacuum container (not shown), bulk silicon is fed into a water-cooled copper hearth 2 from a hopper 11 at a constant supply rate, and is melted by an electron gun 3 installed above. A water-cooled rotating drum 4 is located close to this water-cooled steel hearth 2.
is installed and rotates in the direction of the arrow in the figure, molten silicon adheres to and solidifies on this drum, is rolled up upwards, and the silicon thin plate is peeled off from the water-cooled rotating drum 4 by a scraper 6.

The electrobeam (electron gun 3) used as a heating source is used for melting at a high temperature in the aX sky, and a sufficient scouring effect is expected in the water-cooled copper hearth 2, so the silicon lump introduced into the water-cooled copper hearth 2 is Silicon thin plates obtained from metallic silicon (purity 98z) can also be obtained with sufficient purity for use in solar cells.

Therefore, in the case of water droplets, the silicon introduced into the water-cooled copper hearth 2 may be metal silicon.

In addition, the water-cooled rotary drum 4 may be provided with vertical grooves in addition to the horizontal striped grooves, or even with striped protrusions, the same effect can be obtained.

Rod-shaped polycrystalline silicon having a diameter of 60 wφ was supplied into the water-cooled steel hearth 2 under the following specifications and operating conditions based on FIG.

Diameter of water-cooled rotating drum 4: 0.5mm, W4 length: 0.3a
*Rotation speed of water-cooled rotating drum 4: 6 Orpm Size of water-cooled copper hearth 2: 0.3 m wide x 0.7 m long Electron gun 3
5OOKW melting material polycrystalline silicon rod 60
mφ Dissolution rate 300kg/h high plate
0.1 Thickness x 30 Width Under the above conditions, it was possible to continuously produce a 1 m thick silicon thin plate from 100 kg supplied into a water-cooled steel hearth in about 20 minutes.

〔Effect of the invention〕

According to the method for manufacturing a silicon thin plate for solar cells of the present invention, a silicon thin plate can be directly manufactured from a molten state, and thin plates for solar cells can be manufactured with a higher yield than conventional methods.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the method of the present invention, FIG. 2 is an explanatory diagram showing another embodiment, FIGS. 3 and 4 are enlarged explanatory diagrams of part A, respectively, and FIG. 5 is an explanatory diagram of the conventional method. 6 and 7 are explanatory diagrams of the conventional FZ method and CZ method, respectively, and FIG. 8 is an explanatory diagram of single crystal cutting. In the figure, 1: polycrystalline silicon, 2: water-cooled copper base,
3: Electron gun, 4: Water-cooled rotating drum, 5: Silicon M plate,
6: scraper, 7: m groove, 8: molten silicon, 9:
Solidified shell, 10: Drive roll, 118 hopper. Reference numerals in the drawings indicate the same or corresponding parts. Agent Patent Attorney Tadashi Sato Year 6: Sugreno! - Figure 1 Figure 2 Figure 7 Figure 8 Procedural Amendment (Mouse) 1. Indication of the case Japanese Patent Application No. 61-208052 2, Name of the invention Method for manufacturing silicon thin plates for solar cells 3, Person making the amendment Relationship to the case Patent applicant address 1-2 Marunouchi-chome, Chiyoda-ku, Tokyo Name
(412) Nippon Kokan Co., Ltd. 4, Agent address: Amita Building, 5-8-6 Toranomon, Minato-ku, Tokyo Figures 1 to 4 of the "Drawings" are attached to Figure 1 of the revised drawings. 6: Souffle bar correction drawings (Fig. 1, Fig. 2, correction drawing procedures, voluntary writing) Showa 6ξ3, 6th.

Claims (2)

[Claims] (1) A water-cooled rotary drum whose axis is approximately horizontal is rotated at a predetermined circumferential speed in a vacuum device, and a polycrystalline silicon bar is placed horizontally or vertically on the upper part of a water-cooled copper hearth provided close to the water-cooled rotary drum. The tip is melted with an electron gun and injected dropwise into a water-cooled copper hearth, or a lump of polycrystalline silicon is continuously introduced into a water-cooled copper hearth, and this is melted with an electron gun to generate the silicon. A method for manufacturing a silicon thin plate for a solar cell, characterized in that a thin silicon plate is manufactured by depositing molten silicon in a water-cooled copper hearth onto the water-cooled rotating drum and rolling it up. (2) The method for manufacturing a silicon thin plate for solar cells according to claim 1, characterized in that a water-cooled rotating drum having striped grooves or protrusions on its surface is used.