JP2017039634A - Production method of silicon crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of an FZ single crystal which extremely reduces heavy metals such as Fe and Cu, light metals represented by Al, C that is homologous to silicon, and O2 etc. in comparison with a conventional CZ single crystal for a solar system, and by which life time of at least 600 μ sec. or more is obtained.SOLUTION: A supply power of a high frequency apply working coil 1 with a coil of one to several winds of a doughnut shape and a bowl type being wide in an upper circumference, and narrow in a lower circumference is adjusted, while a product single crystal support ring 8 is contacted to a product single crystal 3, and stress applied to a thin single seed crystal 4 is transferred to the product single crystal support ring, when the single seed crystal 4 is pulled down to grow the product single crystal 3 at a speed of 2 to 6 mm/min. in desirably Ar + He gas atmosphere, and an axis of the single seed crystal 4 is arranged in eccentricity to an axis of a silicon polycrystal raw material rod 2, and a melting silicon raw material is supplied in eccentricity from the silicon polycrystal raw material rod 2, in the production method of the FZ single crystal for a solar cell.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a silicon crystal for a solar cell, and more particularly relates to a method for producing an FZ single crystal for a solar cell, which is limited to the purpose of using the FZ method single crystal as a solar cell among silicon crystals. .

  As a raw material for solar cells, over 80% of the world currently uses silicon. However, most of the raw material silicon is manufactured by the high-cost Siemens method. Moreover, since the polycrystalline silicon manufacturing process by the Siemens method is basically established for semiconductors, it is a robust and complex process with the highest priority on quality, and its product is about 8 to 10 times as much. It is expensive.

  Since the raw material cost becomes high in this way, in order to secure a large amount of power generation with a small amount of raw material silicon, a solar cell silicon crystal that can be mass-produced at a lower cost and can obtain a high photoelectric conversion efficiency. Development is required.

Problems to be solved by the invention

  In order to obtain a high photoelectric conversion efficiency in a solar cell, a solar cell that is inexpensive and highly efficient can be obtained by adopting an FZ single crystal instead of a silicon crystal for solar cells that has progressed from amorphous to polycrystalline to CZ single crystal. A photovoltaic system can be established to achieve the final purpose for consumer use. However, it is generally recognized that FZ single crystals are much more expensive than CZ single crystals due to differences in manufacturing methods. For this reason, it is hardly used in current solar cells. The present invention provides an FZ single crystal that is specialized for solar cells and has reduced costs.

  Provided is a technology for producing FZ single crystals for solar cells having a long lifetime, specializing in solar cell substrate materials, as FZ single crystals, which are the materials that provide the longest lifetime in the industry as a semiconductor silicon substrate. In other words, the FZ single crystal produced by this method has the required crystal perfection (lineage, swirl, twins, other micro defects such as miniature defects generally called a saucer, etc.) The present invention is not particularly required, and relates to a single crystal manufacturing method characterized in that the lifetime is kept at least 600 μsec or more.

  Unlike the conventional solar CZ single crystals, the FZ single crystals for solar cells produced industrially by this method include Fe, Cu, heavy metals such as so-called “lifetime killer” contained in silicon, Al, and so on. The purpose is to drastically reduce representative light metals, C of the same family as silicon, O2 and the like.

Means for solving the problem

In order to solve the above problems, the invention claimed in the present application is as follows.
(1) While melting the seed single crystal (seed) with the high-frequency application working coil, the raw material silicon polycrystalline raw material rod is heated in advance with the preheating coil for raw material heating, and the melting temperature is subsequently continued with the high-frequency application working coil. Dissolve its bottom until. Thereafter, the seed single crystal (seed) is passed through the high-frequency application working coil and brought into contact with the charge raw material silicon polycrystalline raw material rod, and the seed single crystal ( Pull seed down. At this time, the axis of the seed single crystal (seed) is eccentrically set with respect to the axis of the charging raw material silicon polycrystalline raw material rod, and the silicon raw material dissolved from the charging raw material silicon polycrystalline raw material rod is eccentric. The production method of the FZ single crystal is characterized in that the product FZ single crystal is produced by supplying the product.
(2) In the above (1), the high-frequency application working coil is a donut shape, and uses a bowl-shaped coil having a bowl shape with a wide upper circumference and a narrow lower circumference.
(3) The raw material silicon polycrystal raw material rod for charging usually needs to be grind controlled for its diameter in microns, but the preheating coil for heating the raw material is controlled by the output of the laser diameter detector. A method for producing an FZ single crystal.
(4) The product FZ single crystal is gently pulled down from the seed single crystal (seed) at a speed of about 2 to 6 mm / min to grow the product crystal, while the upper edge of the product FZ single crystal is ground from below as a product single crystal support ring A method for producing an FZ single crystal, wherein a stress applied to a thin seed crystal is transferred to a product single crystal support ring by gently raising and contacting the applied quartz support ring.
(5) The solar FZ furnace normally uses Ar gas, but in the present invention, Ar + He gas is used for the purpose of preventing the occurrence of the mustache-like peak voltage caused by noise at the time of application, and the argon discharge caused by this. A method for producing an FZ single crystal, characterized in that

Effect of the invention

  Compared to conventional products, low-cost solar cell FZ single crystals with a long lifetime can be obtained. This is far more photoelectric conversion than CZ single crystals with the highest photoelectric conversion efficiency among conventional products. Tandem-type silicon quantum dots that enable industrially improving the efficiency of FZ single crystals and, in the near future, the photoelectric conversion efficiency from 25% → 30% → 35% → 45% on the current technology line It can be supplied as a raw material for solar cells that facilitates industrialization of molds and the like.

  This means that the solar cell business, which has a future as clean energy, greatly contributes to the elimination of the shortage of silicon raw materials, and greatly contributes to the expansion of the use of solar cells, contributing to social and environmental improvements. That's big.

  Although specifically described in the above item [0006], the FZ single crystal produced according to the present invention thereby produces crystal integrity (lineage, swirl, twin, other micro defects, etc.) normally required for semiconductors. (Defect free) is not required, but the lifetime is mainly characterized by keeping about 600 μsec or more. Also, the FZ single crystal produced by the present invention is different from conventional CZ single crystals for solar cells, and is represented by heavy metals such as Fe, Cu, etc., which are so-called lifetime killers contained in silicon, Al. C and the like belonging to the same light metal and silicon can be extremely reduced. Of course, as is well known, the O2 content is extremely small compared to CZ.

FIG. 1 is an explanatory view showing an embodiment of the apparatus of the present invention.
While melting the seed single crystal (seed) 4 with the high-frequency application working coil 1, the raw material heating polycrystalline silicon rod 2 is charged to the melting temperature by the high-frequency application working coil 1 to the melting temperature. Dissolve. Then, the seed single crystal (seed) 4 is passed through the high-frequency application working coil 1 and brought into contact with the charge raw material silicon polycrystal raw material rod 2, and the seed single crystal is adjusted while adjusting the power supplied to the high-frequency application working coil 1. (Seed) 4 is pulled downward. At this time, the axis of the seed single crystal (seed) 4 is eccentrically set with respect to the axis of the charging raw material silicon polycrystalline raw material rod 2, and the silicon raw material dissolved from the charging raw material silicon polycrystalline raw material rod 2 is By supplying eccentrically, the product FZ single crystal is produced.

Overall view of crystal growth

DESCRIPTION OF SYMBOLS 1 ... High frequency application working coil 2 ... Raw material silicon polycrystal raw material rod 3 for charge ... Product FZ single crystal 4 ... Single crystal for seed (seed)
5 ... After-heating coil 6 ... Preheating coil for raw material heating 7 ... Laser diameter detector 8 ... Product single crystal support ring

Claims (5)

  While melting the seed single crystal (seed) with the high-frequency applying working coil, the bottom surface of the charging raw material silicon polycrystalline raw material rod is melted to the melting temperature with the high-frequency applying working coil by the preheating coil for raw material heating. Thereafter, the seed single crystal (seed) is passed through the high-frequency application working coil and brought into contact with the charge raw material silicon polycrystalline raw material rod, and the seed single crystal ( Pull seed down. At this time, the axis of the seed silicon single crystal (rod) is arranged and set so that the fine axis of the seed single crystal (seed) can be finely adjusted, and is dissolved from the polycrystalline silicon rod for charge silicon. A method for producing an FZ single crystal for a solar cell, wherein a product FZ single crystal is produced by supplying an eccentric silicon raw material eccentrically.   2. The method for producing an FZ single crystal for a solar cell according to claim 1, wherein the high-frequency application working coil is a donut shape, and uses a bowl-shaped coil having one or several turns having a wide upper circumference and a narrow lower circumference.   The raw material silicon polycrystal raw material rod for charging usually needs to be grind controlled for its diameter in micron units, but the FZ is characterized in that the preheating coil for material heating is controlled by the output of the laser diameter detector. A method for producing a single crystal.   The product FZ single crystal is gently pulled down from the seed single crystal (seed) at a speed of about 2 to 6 mm / min to grow the product crystal, and the upper edge is ground as a product single crystal support ring from below. A method for producing an FZ single crystal, wherein a stress applied to a thin seed crystal is transferred to a product single crystal support ring by gently raising and making contact with the support ring.   FZ furnaces for solar use normally use Ar gas. However, in the present invention, the FZ single crystal is characterized in that Ar + He gas is used in combination for further stabilization regarding prevention of corona discharge and the like due to atmospheric disturbance factors. Production method.

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