JPH10182124A - Treatment of slice loss of silicon substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively recover cut waste of silicon by a metallurgical means and to reuse the recovered silicon by washing the cut waste of high-purity silicon sliced by a wire saw with an acid, drying, supplying the dried waste to a plasma jet, spraying it on a water-cooled copper and recovering the silicon as a cooled ingot. SOLUTION: A gas 4 is passed to a plasma generating nozzle 1 equipped with an anode 2 and a cathode 3 to produce a plasma jet 7. Cut waste of high- purity silicon sliced by a wire saw, washed with an acid and dried is dispersed into a plasma jet 7 from a powder throwing-in route 5 of the plasma generating nozzle 1, sprayed on a water cooled copper target 8 to form a cooled lump 9, which is recovered. In the case of cut waste sliced by using high-pressure water using pure water instead of a saw, washing with an acid is not required since the cut waste is not stained. Preferably, H2 is used as a carrier gas for transporting the cut waste.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating a silicon substrate slice loss generated when a high-purity silicon substrate used for a solar cell or the like is sliced.

[0002]

2. Description of the Related Art Conventionally, a process for manufacturing a wafer from a high-purity polycrystalline silicon ingot for a solar cell is shown in FIG. First, as shown in FIG. 3A, the surface of the cast silicon ingot 21 is peeled off, and then, as shown in FIG. And Next, the wafer block 22
Is sliced by a wire saw 24 as shown in FIG. As shown in the enlarged view of FIG. 4, in this wafer cutting, for example, a cutting margin 26 for cutting a wafer 460 having a thickness of 460 μm is about 300 μm, and the cutting loss reaches about 40%.

When a polycrystalline cast ingot is cut with a wire saw, cutting chips are generated. Conventionally, the cutting chips are discarded as cutting powder dust, and the yield of silicon becomes about 60%. For this reason, 40% of high-purity silicon becomes cutting waste as cutting loss. Since the cutting chips are fine particles, and the wire material, the cutting oil, the carbon, and the like are mixed, the cutting chips silicon generated by the cutting were not used in the remelting. This cutting waste contains Fe, Ni, and the like due to wear of the wire saw, and carbon due to wear of the diamond abrasive grains.

[0004]

The present situation is that the above-mentioned cutting chips from wafer cutting are discarded without being collected. The reason is that, even if these are collected and reused, it is expensive and not economical to convert them to silane gas and process them by CVD. The inventor paid attention to this point, and has developed a technique for recovering inexpensively by metallurgical means.

An object of the present invention is to provide such a novel means.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made to achieve the above-mentioned object, and as a novel technical means, after acid-cleaning and drying high-purity silicon cuttings sliced with a wire saw, A method for treating a silicon substrate slice loss, comprising supplying a plasma jet to a water-cooled copper target, spraying the plasma jet onto a water-cooled copper target, generating a cooled mass on the water-cooled copper target, and collecting the cooled mass. I do. As the acid cleaning, for example, hydrochloric acid cleaning is appropriate.

In the above-mentioned processing method, in the case where high-purity silicon cuttings sliced by high-pressure water using pure water instead of the high-purity silicon cuttings sliced by the wire saw, the high-purity silicon cuttings are dried and then subjected to plasma treatment. A method is provided for feeding into a jet. Slicing with high-pressure water using pure water does not cause contamination, so there is no need for acid washing, etc.
It is preferable because high-purity silicon can be obtained only by dehydration and spraying on a target after dehydration and drying. Pressure is 30
A mixture of pure water and high-purity silicon mixed at 0 to 1000 kg / cm ² is used.

In the above method, it is more preferable that H ₂ is used as a carrier gas for transporting cutting chips to be supplied into the plasma jet, and silicon oxidized at the time of cutting is reduced in the plasma jet. .

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram showing the means of the present invention. The plasma generation nozzle 1 includes an anode 2 and a cathode 3 and generates a plasma jet by passing a gas 4. From the powder input passage 5 of the plasma generation nozzle 1
The cutting chips 6 are supplied and dispersed in the plasma jet 7,
It is sprayed on the water-cooled copper target 8 in a molten state. The injected high-purity silicon 9 becomes a lump and becomes a water-cooled copper target 8.
Collect it as it accumulates on top. It is preferable to use hydrogen as a carrier gas in supplying the cutting chips 6, since silica (SiO ₂ ) is reduced in the plasma jet.

As shown in FIG. 2, high-purity silicon 11 is sprayed from a high-pressure water nozzle 13 with high-pressure water 14 to slice the wafer 12. At this time, pure water is used as the high-pressure water 14, and high-purity silicon particles can be mixed into the pure water to cut efficiently. The pure water 14 is concentrated and collected in a centrifugal separator or a sedimentation settling tank or the like,
The recovered slurry is dried and supplied to the plasma nozzle shown in FIG.

When the high-pressure water nozzle 13 is significantly worn, acid leaching of the cutting waste slurry is required.
Dissolve in Cl. High-purity silicon 9 recovered in FIG.
If redissolved and the impurities are purified by directional solidification, it can be recovered and reused again as silicon for solar cells at low cost.

[0012]

According to the present invention, wire saw cutting chips or high-pressure water cutting chips can be recovered and reused as high-purity silicon for solar cells at low cost.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a recovery method of the present invention.

FIG. 2 is an explanatory diagram of high-pressure water cutting.

FIG. 3 is a process chart of manufacturing a wafer from an ingot.

FIG. 4 is an explanatory diagram of generation of cutting waste.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plasma generation nozzle 2 Anode 3 Cathode 4 Plasma gas 5 Powder supply passage 6 Cutting chips 7 Plasma jet 8 Water-cooled copper target 9, 11 High-purity silicon 12 Wafer 13 High-pressure water nozzle 14 High-pressure water 21 Ingot 22 Wafer size block 23 Cutting line 24 Wire saw 25 Wafer 26 Cut-off

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Yasuhiko Sakaguchi 1 Kawasaki-cho, Chuo-ku, Chiba-shi Kawasaki Steel Engineering Co., Ltd. (72) Inventor Naomichi Nakamura 1 Kawasaki-cho, Chuo-ku, Chiba-shi Kawasaki Steel Co. In-house (72) Inventor Yoshihide Kato 1 Kawasaki-cho, Chuo-ku, Chiba City Kawasaki Steel Corp.

Claims (3)

[Claims] 1. A high-purity silicon chip sliced with a wire saw is washed with an acid and dried, and then supplied into a plasma jet. The plasma jet is sprayed on a water-cooled copper target, and cooled on the water-cooled copper target. A method for treating silicon substrate slice loss, comprising generating a lump and collecting the cooled lump. 2. A method for supplying high-purity silicon cuttings sliced with high-pressure water using pure water in place of high-purity silicon cuttings sliced by a wire saw into a plasma jet after drying. The method for treating silicon substrate slice loss according to claim 1. 3. The plasma jet according to claim 1, wherein H ₂ is used as a carrier gas for transporting cutting chips supplied into the plasma jet, and silicon oxidized at the time of cutting is reduced in the plasma jet. Processing method for silicon substrate slice loss.