KR20120026430A - Apparatus and method for manufacturing polycrystalline silicon - Google Patents

Abstract

PURPOSE: An apparatus and method for manufacturing a polycrystalline silicon are provided to maintain the lifetime of a solar cell by suppressing the contamination of an electrode metal. CONSTITUTION: An induction coil(2) is formed in order to surround a cooler mold(1). A plasma torch(3) is installed in the upper part of the cooler mold and is movable up. A support(4) is installed in the lower part of the induction coil and is movable down. A thermostat(6) heats the coagulate silicon ingot and prevent rapid cooling. A carked cask(7) is attached to the lower part of the thermostat.

Description

Apparatus and method for manufacturing polycrystalline silicon {APPARATUS AND METHOD FOR MANUFACTURING POLYCRYSTALLINE SILICON}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for producing polycrystalline silicon capable of producing n-type polycrystalline silicon by applying a continuous casting technique by electron induction, and in particular, using plasma heating in combination with plasma arc, The n-type polycrystalline silicon used as a substrate material of a solar cell relates to the manufacturing apparatus and manufacturing method of the polycrystal silicon which can manufacture without degrading a solar cell characteristic.

When a continuous casting device by electromagnetic induction (hereinafter referred to as "electron casting device") with a cooling mold without a bottom divided in the circumferential direction is used, the molten material (herein, molten silicon) and the mold are hardly formed. Since there is no contact, an ingot (silicon ingot) without impurity contamination can be produced. Since there is no contamination from the mold, there is an advantage of not having to use a high purity material as the material of the mold, and since it can be cast continuously, a significant reduction in manufacturing cost is possible. Therefore, the electronic casting apparatus has been applied to manufacture of polycrystal silicon used conventionally as a substrate material of a solar cell.

FIG. 4 is a diagram schematically showing a configuration example of an electronic casting apparatus used for producing polycrystalline silicon. FIG. As shown in the same figure, inside of the induction coil 2 for heating, the plate-shaped piece of copper long in the longitudinal direction which can water-cool an inside is formed of the induction coil 2 Parallel to the winding axis direction and in the induction coil 2 in a state insulated from each other, and the space surrounded by the plate-shaped piece is cooled without mold (i.e., the side wall is water-cooled). Mold) 1. As the cooling mold 1, the water-cooled copper mold which used the plate-shaped piece as the copper piece is used normally.

The support 4 which can move below is provided in the lower end position (namely, the position corresponded to the bottom part of the cooling mold 1) of the induction coil 2 for heating. In addition, a heat insulator 6 for heating the solidified ingot (silicon ingot 5) to prevent sudden cooling by providing a lower side of the induction coil 2 for heating is provided. The crack cylinder 7 is attached to it. The silicon ingot 5 is drawn downward by a drawing device (not shown).

Above the cooling mold 1, the raw material injector 15 which can inject the raw material into the mold 1 during dissolution is provided. In this example, a plasma torch 3 for heating the raw material silicon is attached above the mold 1 as necessary.

All these devices are installed in the sealed container 8 so that the molten silicon 11 and the high temperature silicon ingot 5 do not directly contact the atmosphere, and usually, the inside of the sealed container 8 is replaced with an inert gas. It is comprised so that continuous casting may be performed in a slightly pressurized state.

In the electroforming method using the above-described electroforming device, when a silicon raw material is charged into the mold 1 and an alternating current is passed through the induction coil 2, a single shape constituting the mold 1 is formed. Since each of the small pieces of metal is electrically divided from each other, a current forms a loop in each of the small pieces, whereby a current is generated on the inner wall side of the mold 1, and a magnetic field is formed in the mold 1 to form silicon. The raw material is melted by heating.

The silicon raw material in the mold 1 receives a force in the inner normal direction of the molten silicon 11 surface by the interaction between the magnetic field generated by the current in the inner wall of the mold 1 and the current on the molten silicon 11 surface. It dissolves in the non-contact state with the mold 1.

After the molten silicon 11 is sufficiently homogenized, if the support 4 is moved downward little by little, the cooling starts by moving away from the induction coil 2, so as to be unidirectional toward the molten silicon 11 in the mold 1. Solidification proceeds to form a silicon ingot 5 having a cross section having the same shape as the mold cross section.

Since the amount of molten silicon 11 decreases corresponding to the movement of the support 4 downward, the amount of raw silicon is supplied from the raw material injector 15, and the upper surface of the molten silicon 11 is always the same. The polycrystalline silicon ingot 5 can be continuously manufactured by maintaining a height level and continuing heating melt | dissolution, drawing, and raw material supply.

The quality of the polycrystalline silicon produced using this electronic casting device is high purity, and the conversion efficiency (particularly, energy that can be converted into electrical energy and extracted with respect to incident light energy) when used as a substrate of a solar cell. In order to increase the ratio, many technical developments have been made in the past. At that time, development of a method of using both electromagnetic induction heating by an induction coil and plasma heating by a plasma arc has been actively progressed.

For example, Patent Literature 1 discloses a silicon continuous casting method in which electromagnetic induction heating and plasma heating are used in combination to improve quality as a solar cell. According to the casting method described in the above document, the burden of electromagnetic induction heating can be reduced by using plasma heating in combination with the melting of raw materials during casting, and by the reduction, tropical flow of molten silicon due to electromagnetic force is suppressed. By suppressing the heat flux downward, the solid-liquid interface is flattened. As a result, it is said that the temperature gradient in the radial direction of the silicon ingot immediately after solidification is reduced, the thermal stress generated inside the crystal is alleviated, and the occurrence of crystal defects deteriorating the conversion efficiency of the solar cell is suppressed.

And in this patent document, in order to utilize the effect of a plasma heating to the maximum, the method of scanning a plasma arc torch horizontally on a silicon melt is proposed without performing heating to the center part of the silicon melt in a crucible further, The plasma arc is said to be preferably a transition type plasma arc which is easy to obtain a large output required for silicon casting.

In the silicon continuous casting method which uses such electromagnetic induction heating and plasma heating together, a copper (Cu) electrode is used as an electrode (plasma electrode) of a plasma torch. This is because, in plasma heating, the electrode becomes high in order to generate a high temperature plasma arc, but the copper material has high thermal conductivity, so that water cooling is effective.

However, when a Cu electrode is used as the plasma electrode and the cathode is used as a cathode, gas (usually Ar) molecules, which are plasma media, are formed on the plasma electrode by arc discharge between the plasma electrode (cathode) and the object to be dissolved (melted silicon; anode). And ionized Ar ions collide. Therefore, the plasma electrode is damaged, evaporated, melted, and consumed, and Cu is mixed in the plasma medium. In addition, the emission of electrons is accelerated in the plasma electrode.

Even if the plasma electrode (Cu electrode) is used as the anode and the silicon to be dissolved is used as the cathode, the plasma electrode is damaged, melted, and consumed by arc discharge, but not as much as when the Cu electrode is used as the cathode.

Cu mixed in the plasma medium due to the melting loss of the plasma electrode (Cu electrode) and introduced into the atmosphere contaminates the polycrystalline silicon ingot during manufacture or the molten silicon before solidification by electron casting. The metal impurity becomes a trap (trap) level of recombination of the carriers generated by light, thereby extinguishing the carriers (i.e., shortening the carrier life), shortening the life time of the polycrystalline silicon, and further, transferring the polycrystalline silicon to the substrate. This reduces the conversion efficiency of the solar cell configured. In this case, in particular, the influence on the life time of the n-type silicon is great, and even if the amount of Cu contamination is the same, the life-time value of the n-type silicon is significantly worse than that of the p-type silicon.

Japanese Laid-Open Patent Publication 2001-19594

 Miyazaki Morimasa: “Silicon Crystals and the Challenge of Wafer Technology – Large-Sized Hardening and Flattening” Edit by Kishino Seigo, Realize, Japan, 1994, p273

This invention is made | formed in view of such a situation, and when manufacturing n type polycrystal silicon by the electromagnetic induction method using plasma heating by a plasma arc together, the metal contamination contaminates polycrystalline silicon used as a substrate material of a solar cell. It is an object of the present invention to provide an apparatus and a method for producing polycrystalline silicon that can be produced without reducing the effect of the solar cell and degrading the solar cell characteristics (particularly, life time).

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, the inventors investigated the influence which the metal impurity (Cu or X) mixed in p-type or n-type crystalline silicon has on the life time of the said crystalline silicon.

The life time is defined as the time when the carrier generated by light irradiation or the like decreases by recombination and its concentration becomes 1 / e. If lattice defects or metallic impurities are present on the silicon substrate of the solar cell, they become trap (capture) levels, and carriers are extinguished by recombination, resulting in a shorter life time.

On the other hand, in the substrate of a solar cell, the higher conversion efficiency is obtained as the life of the carrier generated by light is longer. Therefore, by investigating the lifetime of a substrate, the evaluation of the conversion efficiency of the solar cell using the substrate can be performed to some extent.

FIG. 2 is a view described in the above-mentioned Non-Patent Document 1, which shows the relationship between the surface concentration of the impurity Cu present on the surface of the silicon substrate and the life time. The unit of surface concentration is atoms / cm <2>.

As shown in FIG. 2, in the case of p-type silicon (indicated by □ in the figure), even if the surface concentration of Cu increases, there is no significant change in life time. In contrast, in the case of n-type silicon (indicated by ■ in the drawing), when the surface concentration of Cu is low (about 1 × 10 ¹⁰ atoms / cm 2), n-type silicon has a longer life time than p-type silicon. With the increase of the surface concentration, the life time is reversed, and the p-type silicon becomes longer, and when the surface concentration becomes about 1 × 10 ¹³ atoms / cm 2, the difference in life time becomes considerably large.

That is, when manufacturing n type polycrystal silicon by an electroinduction method using plasma heating together, when using a Cu electrode as a plasma electrode, contamination of molten silicon and an ingot resulting from the melting loss of a Cu electrode cannot be avoided, When contamination progresses, the remarkable fall of a solar cell characteristic (especially life time) is anticipated.

FIG. 3 is a diagram described in the above-mentioned Non-Patent Document 1, which shows the relationship between the surface concentration of impurity tungsten and the life time present on the silicon substrate surface. As shown in Fig. 3, in either case of p-type silicon (indicated by □ in the figure) and n-type silicon (indicated by ○ in the figure), the life time gradually decreases with increasing surface concentration, but n-type silicon Is always longer than p-type silicon. In addition, although FIG. 3 and FIG. 2 are the result with respect to a silicon single crystal, it does not think that a big difference arises in a single crystal and a polycrystal regarding the fact that a metal impurity becomes a trap of carrier recombination.

2 and 3, it can be seen that the influence on the life time of n-type silicon varies greatly depending on whether the impurity (polluted) metal is Cu or Pb. When the impurity metal is Cu (see Fig. 2), the life time of n-type silicon is shortened almost linearly with the increase of the surface concentration of Cu, and when the contamination by Cu proceeds, the surface concentration is further increased. The life time is expected to be further shortened. In contrast, when the impurity metal is Q (see FIG. 3), the adverse effect on the life time (shortening of the life time) is relatively small, and the tendency to saturate with the increase of the surface concentration is recognized.

Therefore, when the n-type polycrystalline silicon is produced by the electromagnetic induction method using plasma heating together, a polycrystalline silicon is obtained in which the lifetime is long (that is, the carrier life is long) and high conversion efficiency is obtained when used as the substrate of the solar cell. In order to do this, it is considered that Ｗ is suitable as an electrode material of the plasma electrode.

The present inventors produced n-type polycrystalline silicon by the electromagnetic induction method which actually uses plasma heating together, and investigated the effect which the difference of an electrode material has on the life time of polycrystal silicon based on such examination result. As a result, as shown in the Examples described later, it was confirmed that V was suitable as a material of the plasma electrode.

This invention is the result of such examination, Comprising: The manufacturing apparatus of the polycrystalline silicon of (1) below, and the manufacturing method of the polycrystal silicon of (2) are summary.

(1) A conductive bottomless cooling mold, wherein a part of the axial direction is divided into a plurality of in the circumferential direction, and an induction coil surrounding the mold, and are provided as a heating source so as to be elevated above and below the cooling mold. A device for producing polycrystalline silicon having a plasma torch for generating a plasma arc, wherein the molten silicon is lowered downward to coagulate by using electric induction heating by the induction coil and plasma heating by a plasma arc. And Ｗ as a plasma electrode provided in the plasma torch, and the apparatus is used for the production of n-type polycrystalline silicon.

In the apparatus for producing polycrystalline silicon of the present invention, when the plasma electrode is used as the anode and the silicon to be heated is used as the cathode, consumption of the electrode is slightly suppressed and n manufactured by using the apparatus. It is preferable because it can be kept high without deteriorating the life value of the type polycrystalline silicon.

(2) Polycrystalline silicon is continuously cast into polycrystalline silicon by charging a silicon raw material into a bottomless cooling mold, melting a combination of electromagnetic induction heating and plasma heating by a plasma arc, and lowering and melting the molten silicon downward. A method of producing silicon, the method of producing polycrystalline silicon, wherein n is used as a plasma electrode for generating the plasma arc, and n-type polycrystalline silicon is produced.

In the method for producing polycrystalline silicon of the present invention, by adopting an embodiment in which the plasma electrode is used as an anode and silicon as a heated material is used as a cathode, the consumption of the electrode is slightly suppressed and the n-type polycrystalline silicon obtained It is preferable because it can be kept high without deteriorating the life time value.

The manufacturing apparatus of the polycrystalline silicon of this invention is a manufacturing apparatus which has a plasma torch in addition to an induction coil as a heating source, and uses 으로서 as a plasma electrode, Usually, it is preferable to further make a plasma electrode (Ｗ electrode) into an anode Embodiment is adopted. By using this manufacturing apparatus, the influence of the contamination by the metal used for the electrode can be suppressed, and the n-type polycrystalline silicon can be manufactured which has a long lifetime and is very suitable as a substrate material of a solar cell. The manufacturing method of the polycrystal silicon of this invention can be easily performed using the manufacturing apparatus of the said invention.

BRIEF DESCRIPTION OF THE DRAWINGS It is a longitudinal cross-sectional view which shows schematic structural example of the manufacturing apparatus of the polycrystal silicon of this invention.
FIG. 2 is a diagram showing the relationship between the surface concentration and the life time of impurity Cu present on the silicon substrate surface.
3 is a graph showing the relationship between the surface concentration and the life time of the impurity film existing on the silicon substrate surface.
It is a figure which shows typically the structural example of the electronic casting apparatus used for manufacture of polycrystal silicon.

(Form to carry out invention)

The apparatus for producing polycrystalline silicon of the present invention is based on the premise that the electroforming apparatus has a conductive bottomless cooling mold in which a part of the axial direction is divided into a plurality of in the circumferential direction, and an induction coil surrounding the mold.

The premise of such an electronic casting apparatus is that when manufacturing an n-type polycrystalline silicon used as a substrate material of a solar cell, casting is performed in a mold with little contact between molten silicon and the mold, and metal contamination from the mold is caused. This is because n-type polycrystalline silicon can be produced which is very suitable as a substrate material of a solar cell. It is not necessary to use a high purity material as a material of a mold, and since it can cast continuously, the manufacturing cost can also be reduced significantly.

The premise that the manufacturing apparatus of the present invention further has a plasma torch for generating a plasma arc, which is provided as a heating source so as to be elevated above the cooling mold, is described in Patent Document 1 mentioned above. It is because the silicon ingot which improved the quality as a solar cell can be manufactured by using plasma heating by a plasma arc together with raw material melt | dissolution similarly.

A feature of the production apparatus of the present invention is that tungsten is used as the plasma electrode provided in the plasma torch, and the apparatus is used for the production of n-type polycrystalline silicon.

As described above, the use of 으로서 as the plasma electrode, when manufacturing n-type polycrystalline silicon by the electromagnetic induction method using plasma heating in combination, has a long lifetime and high conversion efficiency is obtained when used as a substrate of a solar cell. To produce polycrystalline silicon.

The reason why the manufacturing apparatus of the present invention is used for the production of n-type polycrystalline silicon is that the effect of the manufacturing apparatus of the present invention is exerted particularly when manufacturing the n-type polycrystalline silicon. In addition, as described below, it can be said that the advantage of manufacturing n-type polycrystalline silicon by an electronic casting apparatus is very large.

That is, even when a silicon raw material to which a dopant such as phosphorus (P) is added is melted in a quartz crucible and monocrystalline silicon is produced from the solution by Czochralski (CZ) method, melting is carried out in the quartz crucible. Even when polycrystalline silicon is produced by a casting method which flows into a mold and solidifies, segregation of dopants occurs during crystal growth. In particular, when P is added, it is susceptible to segregation. However, in the case of continuously producing the polycrystalline silicon ingot by the electronic casting device, since the unidirectional solidification proceeds toward the molten silicon in the mold to form the silicon ingot, the dopant is averaged and segregation does not occur.

1: is a longitudinal cross-sectional view which shows the schematic structural example of the manufacturing apparatus of the polycrystal silicon of this invention, (a) is a whole figure, (b) and (c) is a partial enlarged view of a plasma torch. As shown to the same figure (a), the manufacturing apparatus of this invention has the electroconductive bottomless cooling mold 1 and the induction coil 2 which surrounds the mold 1, and is a heating source further As an example, a plasma torch 3 for generating a plasma arc is provided. The plasma torch 3 is provided above the cooling mold 1 so as to be lifted and lowered.

At the lower end position of the induction coil 2 (that is, the position corresponding to the bottom of the cooling mold 1), a support 4 which can move downward is provided. In addition, an insulator coil 2 is provided below the induction coil 2 to heat the solidified silicon ingot 5 to prevent sudden cooling, and under the insulator 6, a crack tube ( 7) is attached. The silicon ingot 5 is drawn downward by the drawing device 10. All these devices are installed in the sealed container 8 so that the molten silicon 11 and the high temperature silicon ingot 5 do not directly contact the atmosphere.

The plasma electrode is provided in the plasma torch 3, and is connected to the anode of the DC power supply 9 in the illustrated example. The cathode of the DC power supply 9 is connected to the molten silicon 11 via the drawing device 10 of the ingot 5 and the silicon ingot 5.

FIG.1 (b) shows typically the front-end | tip part of the plasma torch 3 and the state around it when a plasma electrode is used as a cathode. An arc discharge 13 is generated between the plasma electrode 12 constituting the cathode and the molten silicon 11 constituting the anode. Ar molecules and ionized Ar ions collide with the plasma electrode (cathode) to generate vaporized evaporates 14 to be mixed in the plasma medium, and metal contaminants are introduced into the atmosphere. However, Ｗ is a high melting point metal, and the amount of meltdown due to evaporation of 현저 is significantly smaller than that in the case of using Cu as the plasma electrode, and the consumption of the electrode 12 is also small.

In the apparatus for producing polycrystalline silicon of the present invention, it is preferable to use 으로서 as the plasma electrode 12, and to further use the plasma electrode (Ｗ electrode) as the anode, and to use the molten silicon 11 as the heated object as the cathode. Do.

When the plasma electrode is used as a cathode (see FIG. 1 (b)), Ar molecules and ionized Ar ions collide with the plasma electrode (cathode), and at least a small amount is dissolved by evaporation and the electrode is consumed. . In order to improve this state and to suppress the melt loss and to prolong (not shorten) the life time of the silicon obtained, it is effective to make the plasma electrode an anode by reversing the polarity of the plasma electrode.

FIG.1 (c) shows the state of the front end part of the plasma torch 3 connected in this way, and the state of the periphery thereof. An arc discharge 13 occurs between the plasma electrode 12 and the molten silicon 11, but since the collision of Ar molecules or ionized Ar ions to the plasma electrode 12 is avoided, the consumption of the electrode is minimal. In addition, introduction of metal contaminants into metal contamination into the atmosphere is also suppressed.

As the electrode used as the electrode material of the plasma electrode, in addition to pure metal, for example, a zinc alloy in which 1% to 2% of ThO ₂ , ZrO ₂ , CeO _2, etc. used as an electrode for TIG welding is added or dispersed; It is good to use a thin material conventionally used in the field of refining and welding.

As a plasma torch used together with an induction coil as a heating source, a transition type having a heated object shown in FIG. 1 as a counter electrode and an electrode in the torch are discharged to eject the generated plasma from the torch. Although there is a non-implementation type, a transition type plasma torch that is easy to obtain a large output and has high thermal efficiency is preferable.

In the method for producing polycrystalline silicon of the present invention, a silicon raw material is charged into a bottomless cooling mold, melted using a combination of electromagnetic induction heating and plasma heating by plasma arc, and the polycrystalline silicon is lowered and solidified by lowering it. Assuming that silicon is continuously cast, the method is characterized in that n is used as a plasma electrode for generating the plasma arc, and n-type polycrystalline silicon is produced. The reason for this assumption and the reason why n is used to manufacture n-type polycrystalline silicon as the plasma electrode are as described above.

Also in the manufacturing method of this invention, employ | adopting embodiment which uses V as a plasma electrode, makes a plasma electrode (Ｗ electrode) into an anode, and uses silicon as a to-be-heated substance as a cathode is preferable. Is a high-melting-point metal, and even though it is used as a cathode, the electrode consumes little. However, Ｗ makes the electrode an anode, so that the consumption of the electrode is made smaller and the introduction of metal contaminants into the atmosphere is suppressed, resulting in a polycrystalline. I can lengthen the life time of the silicon.

In using plasma heating together, Ar used normally may be used as a plasma medium. Regarding other conditions, there is no change basically by changing the Cu electrode of the plasma torch to the electrode, and the operation may be performed in accordance with the conventional method.

The manufacturing method of this invention can be easily performed according to the operation procedure conventionally performed using the manufacturing apparatus of the polycrystal silicon of this invention mentioned above.

As described above, in the apparatus and method for producing polycrystalline silicon of the present invention, the characteristics (particularly, life time) of the solar cell are based on the electrode material (Ｗ, Cu) of the plasma electrode and the metal impurity (pollution) concentration resulting therefrom. And a technique that can be lengthened without shortening the life time of the n-type polycrystalline silicon by employing a pin electrode for the plasma electrode by using a largely different type depending on the conductivity type (p-type and n-type) of the polycrystalline silicon. to be. Since the longer the life time, the longer the carrier life, high conversion efficiency is obtained when the solar cell is configured.

(Example)

Using the apparatus for producing polycrystalline silicon of the present invention having the schematic configuration shown in FIG. 1, the method of the present invention is applied to produce an n-type silicon ingot having a cross-sectional dimension of 345 mm x 505 mm and a length of 7 m. , The consumption rate of the electrode, the amount of ingot contamination by the electrode material and the life time were investigated. In addition, the same investigation was performed also about the case where Cu electrode was used for comparison. In addition, the same investigation was conducted about the p-type silicon ingot.

The conditions of heating in the case of using together plasma heating by a plasma arc are as follows.

Plasma Current: 1100A

Plasma Voltage: 120V

Plasma irradiation time: 70 hours

Distance between object to be heated and electrode: 200㎜

Table 1 shows the results. In Table 1, "the amount of ingot contamination" was calculated from the electrode consumption. In addition, about "life time", the polarity was made negative for each of the electrode materials used, and the life time when the p-type polycrystalline silicon was manufactured was relatively displayed as 1 (reference), respectively. In addition, the measurement of life time was performed by the micro-PCD method about the silicon wafer cut out from each obtained ingot.

Electrode material

plasma
Torch polarity

Electrode consumption
(Μg / h)

Ingot contamination by electrode material
(Atoms / cm 3)

Life time (?) n type p type

Ｗ

plus
<0.01
2.5 × 10 ¹²
10
1.5
minus
0.02
1.0 × 10 ¹³
5
1 (standard)

Cu

plus
0.65
4.5 × 10 ¹⁶
2.5
25
minus
15.05
1.0 × 10 ¹⁸
One
1 (standard)

As shown in Table 1, in the case where the electrode material is Ｗ (Example of the present invention), the life of the n-type polycrystalline silicon is longer than that of the p-type regardless of the polarity of the plasma torch. Silicone could be prepared.

In addition, when the polarity of the plasma torch is positive (that is, when Ｗ is the anode) and when the polarity is negative (that is, when Ｗ is the cathode), the former has a higher electrode consumption rate. Significantly degraded. This is because the collision between the Ar molecules and the ionized Ar ions to the P electrode was avoided by using the P electrode as the anode, and the ingot contamination was greatly reduced, and the life time of the silicon wafer cut out from the obtained ingot was good. . On the other hand, in the latter (when Ｗ was used as the cathode), the lifetime was 1/2 of that, which was lower than that of the former.

On the other hand, when the electrode material is made of Cu (comparative example), even when the collision of the Ar molecule and the ionized Ar ions to the Cu electrode is avoided by adding the polarity to the electrode, the electrode material is set to be smaller than that of the electrode material. The rate of consumption and ingot contamination were significantly higher. As a result, the life time was remarkably short compared with the case where the electrode material was set to kPa. In that case, the influence of the contamination by Cu on the life time was more remarkable in n-type silicon than in p-type silicon.

According to the above embodiment, when polycrystalline silicon is produced by the electromagnetic induction method in combination with plasma heating, the electrode material of the plasma electrode is selected from the viewpoint of long life and high conversion efficiency when the solar cell is constructed. It was confirmed that it was advantageous to manufacture n-type polycrystalline silicon as kappa.

According to the manufacturing apparatus and manufacturing method of the polycrystalline silicon of this invention, the influence of the contamination by metal can be suppressed, and polycrystalline silicon which is suitable as a board | substrate material of a solar cell with a long lifetime can be manufactured. Therefore, this invention can be utilized effectively in the manufacturing field of a solar cell, and can contribute greatly to the advancement of the natural energy utilization technique.

1: mold
2: induction coil
3: plasma torch
4: support
5: silicon ingot
6: thermostat
7: crack tower
8: airtight container
9: DC power
10: drawing device
11: molten silicon
12: plasma electrode
13: arc discharge
14: Cu Evaporate
15: raw material feeder

Claims (4)

Plasma arc, which has a conductive bottomless cooling mold in which a part of the axial direction is divided into a plurality of in the circumferential direction, an induction coil surrounding the mold, and is provided as a heating source so as to be elevated above and above the cooling mold. An apparatus for producing polycrystalline silicon, which has a plasma torch for generating a silicon, and uses molten silicon in combination with electromagnetic induction heating by the induction coil and plasma heating with a plasma arc to lower the molten silicon downward.
Using tungsten as a plasma electrode provided in the plasma torch,
And the said apparatus is used for manufacture of n type polycrystal silicon, The manufacturing apparatus of polycrystalline silicon characterized by the above-mentioned. The method of claim 1,
An apparatus for producing polycrystalline silicon, wherein the plasma electrode is used as an anode, and silicon, which is a heated object, is used as a cathode. The silicon raw material is charged into a bottomless cooling mold, melted by using electromagnetic induction heating and plasma heating by plasma arc together, and the polycrystalline silicon is continuously cast by lowering the molten silicon downward and solidifying. As a method of casting polycrystalline silicon,
Using tungsten as a plasma electrode for generating the plasma arc,
And n-type polycrystalline silicon is produced. The method of claim 3,
A method for producing polycrystalline silicon, wherein the plasma electrode is used as an anode, and silicon to be heated is used as a cathode.

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