JP2012041211A - Polycrystalline silicon wafer and method for casting the same - Google Patents
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- 229910021420 polycrystalline silicon Inorganic materials 0.000 title claims abstract description 47
- 238000000034 method Methods 0.000 title claims abstract description 36
- 238000005266 casting Methods 0.000 title claims abstract description 31
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 51
- 239000001301 oxygen Substances 0.000 claims abstract description 51
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 51
- 238000006243 chemical reaction Methods 0.000 claims abstract description 23
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims abstract description 21
- 229910052802 copper Inorganic materials 0.000 claims abstract description 21
- 239000010949 copper Substances 0.000 claims abstract description 21
- 239000000758 substrate Substances 0.000 claims abstract description 16
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 claims abstract description 6
- 238000001816 cooling Methods 0.000 claims description 25
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 21
- 229910052710 silicon Inorganic materials 0.000 claims description 21
- 239000010703 silicon Substances 0.000 claims description 21
- 230000006698 induction Effects 0.000 claims description 11
- 230000007423 decrease Effects 0.000 claims description 9
- 230000005674 electromagnetic induction Effects 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 claims description 3
- 230000004927 fusion Effects 0.000 claims 1
- 239000007788 liquid Substances 0.000 claims 1
- 235000012431 wafers Nutrition 0.000 description 31
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 9
- 229910052796 boron Inorganic materials 0.000 description 8
- 239000002210 silicon-based material Substances 0.000 description 8
- 239000013078 crystal Substances 0.000 description 7
- 238000004519 manufacturing process Methods 0.000 description 4
- 239000002019 doping agent Substances 0.000 description 3
- 238000002474 experimental method Methods 0.000 description 3
- 239000010453 quartz Substances 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 2
- 238000011109 contamination Methods 0.000 description 2
- 238000009749 continuous casting Methods 0.000 description 2
- 230000020169 heat generation Effects 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 229910021421 monocrystalline silicon Inorganic materials 0.000 description 2
- 230000002093 peripheral effect Effects 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 239000011574 phosphorus Substances 0.000 description 2
- 238000007711 solidification Methods 0.000 description 2
- 230000008023 solidification Effects 0.000 description 2
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052787 antimony Inorganic materials 0.000 description 1
- WATWJIUSRGPENY-UHFFFAOYSA-N antimony atom Chemical compound [Sb] WATWJIUSRGPENY-UHFFFAOYSA-N 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 229910052785 arsenic Inorganic materials 0.000 description 1
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 229910052733 gallium Inorganic materials 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
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- H—ELECTRICITY
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- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
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Abstract
Description
本発明は、多結晶シリコンウェーハ及びその鋳造方法に関し、特に、格子間酸素濃度が低く、太陽電池の基板として用いることにより、太陽電池の変換効率の低下を抑制できる多結晶シリコンウェーハ及びその鋳造方法に関する。 TECHNICAL FIELD The present invention relates to a polycrystalline silicon wafer and a casting method thereof, and in particular, a polycrystalline silicon wafer having a low interstitial oxygen concentration and capable of suppressing a decrease in conversion efficiency of a solar cell by using it as a solar cell substrate and a casting method thereof. About.
現在、太陽電池の製造用の基板としては、主にシリコン結晶が用いられている。
シリコン結晶には単結晶と多結晶とがあり、単結晶シリコンを基板として用いた太陽電池は、多結晶シリコンを基板としたものと比較して、入射した光エネルギーを電気エネルギーにする変換効率が高いという特徴がある。
この単結晶シリコンは、無転位の高品質な結晶を製造するため、一般にチョクラルスキー法によって製造されるが、このチョクラルスキー法による製造は、コストが高くなるという問題がある。また、一般に多結晶の鋳造の場合よりも、単結晶の成長中には、石英坩堝からの酸素の混入が高くなる傾向があり、問題点の1つと考えられている。
At present, silicon crystals are mainly used as substrates for manufacturing solar cells.
Silicon crystals include single crystals and polycrystals, and solar cells using single crystal silicon as a substrate have a conversion efficiency that converts incident light energy into electrical energy compared to those using polycrystalline silicon as a substrate. It is characterized by being expensive.
This single crystal silicon is generally produced by the Czochralski method in order to produce dislocation-free high-quality crystals. However, the production by this Czochralski method has a problem of high cost. In general, oxygen is more likely to be mixed from the quartz crucible during single crystal growth than in the case of polycrystalline casting, which is considered to be one of the problems.
一方、多結晶シリコンを製造する方法としては、キャスト法が知られている(例えば特許文献1)。
キャスト法による多結晶シリコンの鋳造では、ルツボ内で原料である高純度シリコンを加熱溶解し、ボロン等のドーパントを均一添加して、ルツボの中で凝固させる。ルツボは、耐熱性及び形状安定性が求められるため、一般に石英が用いられる。
このキャスト法に一方向性凝固法を適用することにより、結晶粒の大きい多結晶シリコンを得ることが可能となる。
On the other hand, a casting method is known as a method for producing polycrystalline silicon (for example, Patent Document 1).
In the casting of polycrystalline silicon by the casting method, high-purity silicon as a raw material is heated and dissolved in a crucible, and a dopant such as boron is added uniformly and solidified in the crucible. Since crucibles are required to have heat resistance and shape stability, quartz is generally used.
By applying a unidirectional solidification method to this casting method, it is possible to obtain polycrystalline silicon having large crystal grains.
しかし、キャスト法は、溶融したシリコンと石英ルツボとが接触することによって不純物汚染が生じることがあり、また、キャスト法は造塊法であるため、連続した鋳造が困難であることから、生産効率の低下を招くという問題がある。 However, in the casting method, impurity contamination may occur due to the contact between the molten silicon and the quartz crucible, and since the casting method is an ingot-making method, continuous casting is difficult, so production efficiency There is a problem of causing a decrease in
これに対し、溶融シリコンが鋳型にほとんど接触することなく、シリコン結晶を鋳造することのできる電磁鋳造法が知られている(例えば、特許文献2)。
図1は、電磁鋳造法に用いる電磁鋳造装置の一例を模式的に示す断面図である。
図1に示すように、チャンバ１は、内部の発熱から保護されるように二重壁構造の冷却容器になっており、中央部に冷却モールド2、誘導コイル3、ヒータ4が配置されている。
図示例で、冷却モールド2は、銅の水冷筒体であり、上部を除いて周方向に複数分割され、無底である。
また、図示例で、誘導コイル3は、冷却モールド2の外周側に同芯に周設されて、同軸ケーブル(図示せず)で電源に接続される。
図示例で、ヒータ4は、冷却モールド2の下方に同芯に設けられ、冷却モールド2から引き下げられるインゴット5を加熱して、インゴット5の引き下げ軸方向に所定の温度勾配を与える。
On the other hand, there is known an electromagnetic casting method capable of casting a silicon crystal with almost no molten silicon in contact with a mold (for example, Patent Document 2).
FIG. 1 is a cross-sectional view schematically showing an example of an electromagnetic casting apparatus used in the electromagnetic casting method.
As shown in FIG. 1, the chamber 1 is a double-walled cooling container so as to be protected from internal heat generation, and a cooling mold 2, an
In the illustrated example, the cooling mold 2 is a copper water-cooled cylinder, and is divided into a plurality of parts in the circumferential direction except the upper part, and has no bottom.
Further, in the illustrated example, the
In the illustrated example, the heater 4 is provided concentrically below the cooling mold 2, heats the ingot 5 pulled down from the cooling mold 2, and gives a predetermined temperature gradient in the pulling axis direction of the ingot 5.
図1に示す装置を用いて、多結晶シリコンを鋳造するには、まず、冷却モールド2にシリコン材料6を装入し、次いで、誘導コイル3に交流電流を流す。
冷却モールド2は、周方向に分割され、各素片は互いに電気的に分離されているため、各素片内で電流ループを形成し、該電流が冷却モールド2内に磁界を発生する。
これにより、電磁誘導加熱によってシリコン材料が溶解され、シリコン融液7が溶製される。
In order to cast polycrystalline silicon using the apparatus shown in FIG. 1, first, the silicon material 6 is charged into the cooling mold 2, and then an alternating current is passed through the
The cooling mold 2 is divided in the circumferential direction, and the respective pieces are electrically separated from each other. Therefore, a current loop is formed in each piece, and the current generates a magnetic field in the cooling mold 2.
Thereby, the silicon material is melted by electromagnetic induction heating, and the silicon melt 7 is melted.
ここで、冷却モールド2内のシリコン材料は、冷却モールド2の内壁がつくる磁界と溶融シリコン表面の電流との電磁気的相互作用によって、冷却モールド2の径方向内側への力を受けるため、冷却モールド2とは非接触の状態で溶解されることとなり、冷却モールドからの不純物汚染が防止され、またインゴット5の下方への引き下げが容易となる。 Here, the silicon material in the cooling mold 2 receives a force inward in the radial direction of the cooling mold 2 due to the electromagnetic interaction between the magnetic field created by the inner wall of the cooling mold 2 and the current on the surface of the molten silicon. 2 is melted in a non-contact state, impurity contamination from the cooling mold is prevented, and the ingot 5 can be easily pulled down.
ここで、溶融シリコンを凝固させるに当たっては、溶融シリコンとインゴットを下部で保持する引き下げ装置8を下方へ移動させる。誘導コイル3の下端から離間するにつれ、誘導磁界が小さくなり、発熱量及び上記の径方向内側への力が小さくなり、冷却モールド2による冷却効果によって、溶融シリコン7が外周側から凝固していき、これを下方へ引き抜いていく。
引き下げ装置の下方への移動に合わせて、冷却モールド2へシリコン材料を連続的に追加装入して、シリコン材料6の溶解及び凝固を継続していくことにより、多結晶シリコンの連続鋳造が可能となる。
なお、多結晶シリコンウェーハの導電性は、ドーパントを添加したシリコン材料6を装入することによって、制御することができる。
p型多結晶シリコンウェーハの鋳造には、ドーパントとしてボロン、ガリウム、アルミニウムなどの溶融原料を用い、n型多結晶シリコンウェーハの鋳造には、ドーパントとしてリン、砒素、アンチモンなど溶融原料を用いることができる。
Here, in order to solidify the molten silicon, the
As the lowering device moves downward, continuous addition of silicon material to the cooling mold 2 and continuous melting and solidification of the silicon material 6 allows continuous casting of polycrystalline silicon. It becomes.
The conductivity of the polycrystalline silicon wafer can be controlled by inserting a silicon material 6 to which a dopant is added.
For casting p-type polycrystalline silicon wafers, molten raw materials such as boron, gallium and aluminum are used as dopants. For casting n-type polycrystalline silicon wafers, molten raw materials such as phosphorus, arsenic and antimony are used. it can.
ところで、上記のキャスト法や電磁鋳造法によって製造された多結晶シリコンウェーハを太陽電池用の基板として用いた場合、太陽電池における光エネルギーから電気エネルギーへの変換効率が、時間経過と共に低下するという問題がある。 By the way, when the polycrystalline silicon wafer manufactured by the above casting method or electromagnetic casting method is used as a substrate for a solar cell, the conversion efficiency from light energy to electric energy in the solar cell decreases with time. There is.
この原因の1つは、非特許文献1に記載のように、基板にボロンと酸素とが含有されていることにより、太陽光の照射時に、ボロンと酸素の複合体からなる欠陥が発生すること(Light Induced Degradation)に起因すると考えられている。 One of the causes is that, as described in Non-Patent Document 1, when the substrate contains boron and oxygen, a defect composed of a complex of boron and oxygen occurs when irradiated with sunlight. It is thought to be caused by (Light Induced Degradation).
図2は、ボロンをドーピングした、抵抗率1.5Ωcmのp型多結晶シリコンウェーハで、FT−IR法(ASTM F121−79)で測定した格子間酸素濃度が異なるものを複数用意し、該多結晶シリコンウェーハを基板に用いた太陽電池の初期変換効率Aと光照射24時間後の変換効率Bとの比((A-B)/A)×100(%)で定義される変換効率の低下率を求める実験を行った結果を示す図である。
なお、ここでいう、「変換効率」は、太陽電池のセル単位面積当たりに照射した光エネルギーE1とセル単位面積当たりから取り出される変換後の電気エネルギーE2との比(E2/E1)×100(%)で定義される。
FIG. 2 shows a p-type polycrystalline silicon wafer doped with boron and having a resistivity of 1.5 Ωcm, which has multiple interstitial oxygen concentrations measured by the FT-IR method (ASTM F121-79). Obtain the conversion efficiency reduction rate defined by the ratio ((AB) / A) × 100 (%) of the initial conversion efficiency A of solar cells using silicon wafers as the substrate and the conversion efficiency B after 24 hours of light irradiation. It is a figure which shows the result of having conducted experiment.
The `` conversion efficiency '' here is the ratio of the light energy E1 irradiated per cell unit area of the solar cell and the converted electric energy E2 taken out per cell unit area (E2 / E1) × 100 ( %).
図2に示すように、太陽電池の変換効率は3%以上低下していることがわかる。
また、多結晶シリコンウェーハとして酸素濃度の低いウェーハを用いても、太陽電池の変換効率の低下率を大きく低減することはないこともわかる。
このように、従来、多結晶シリコンウェーハの格子間酸素濃度が微量であっても、その微量の酸素がボロンとの複合体を形成してしまうものであると考えられていた。
As shown in FIG. 2, it can be seen that the conversion efficiency of the solar cell is reduced by 3% or more.
It can also be seen that even when a wafer having a low oxygen concentration is used as the polycrystalline silicon wafer, the rate of decrease in conversion efficiency of the solar cell is not greatly reduced.
Thus, conventionally, even if the interstitial oxygen concentration of the polycrystalline silicon wafer is very small, it was considered that the small amount of oxygen would form a complex with boron.
本発明の目的は、太陽電池の基板として用いることにより、太陽電池の変換効率の低下を抑制できる多結晶シリコンウェーハ及びその鋳造方法を提供することにある。 The objective of this invention is providing the polycrystalline silicon wafer which can suppress the fall of the conversion efficiency of a solar cell by using it as a board | substrate of a solar cell, and its casting method.
発明者らは前記課題を解決すべく、鋭意究明を重ねた。
その結果、まず発明者は、電磁鋳造法においては、シリコン融液と銅モールドとが非接触状態で鋳造されるにも関らず、酸素含有率の低い銅モールドを用いることにより、多結晶シリコンウェーハの格子間酸素濃度を大幅に低減させることができることを見出した。
さらに、酸素含有率の低い銅モールドを用いるに当たり、チャンバ内の酸素分圧を低減させることも有効であることも知見した。
The inventors have made extensive studies to solve the above problems.
As a result, first, in the electromagnetic casting method, the inventor used polycrystalline silicon by using a copper mold having a low oxygen content even though the silicon melt and the copper mold were cast in a non-contact state. It has been found that the interstitial oxygen concentration of the wafer can be greatly reduced.
Furthermore, when using a copper mold having a low oxygen content, it has also been found that it is effective to reduce the oxygen partial pressure in the chamber.
そして、発明者は、これまでの通説に捉われずに、太陽電池用の基板に用いる多結晶シリコンウェーハ中の酸素濃度をさらに極端に小さくしたところ、酸素とボロンが複合体を形成するのを抑制して、該複合体に起因する太陽電池の変換効率の低下を大幅に抑制することができることの新規知見を得た。 And the inventor made the oxygen and boron form a complex when the oxygen concentration in the polycrystalline silicon wafer used for the substrate for the solar cell was further reduced extremely without being bound by the conventional theory. The new knowledge that it can suppress and can suppress significantly the fall of the conversion efficiency of the solar cell resulting from this composite_body | complex is acquired.
本発明は、上記の知見に立脚するものであり、その要旨構成は、以下の通りである。
(1)FT−IR法(ASTM F121−79)で測定した格子間酸素濃度が1.0×1017atoms/cm3以下の多結晶シリコンウェーハであり、該多結晶シリコンウェーハを基板として用いた太陽電池の変換効率の低下率が3%以下であることを特徴とする、多結晶シリコンウェーハ。
The present invention is based on the above findings, and the gist of the present invention is as follows.
(1) A solar cell using a polycrystalline silicon wafer having an interstitial oxygen concentration of 1.0 × 10 17 atoms / cm 3 or less measured by the FT-IR method (ASTM F121-79) and using the polycrystalline silicon wafer as a substrate A polycrystalline silicon wafer characterized by a reduction rate of the conversion efficiency of 3% or less.
(2)チャンバの誘導コイル内に、軸方向の少なくとも一部が周方向で複数に分割された無底の銅の冷却モールドを配置し、前記誘導コイルによる電磁誘導加熱により、前記冷却銅モールド内にシリコン融液を溶製し、前記シリコン融液を凝固させつつ下方へ引き抜く、多結晶シリコンの鋳造方法において、
前記冷却銅モールドの酸素含有率が低く、且つ前記チャンバ内の酸素分圧が低いことを特徴とする、多結晶シリコンの鋳造方法。
ここで、「銅モールドの酸素含有率が低い」とは、従来用いられていた、酸素含有率100〜500(質量ppm)程度の銅モールドより酸素含有率が低いことをいう。
(2) A bottomless copper cooling mold in which at least a part in the axial direction is divided into a plurality of portions in the circumferential direction is disposed in the induction coil of the chamber, and the inside of the cooling copper mold is subjected to electromagnetic induction heating by the induction coil. In the casting method of polycrystalline silicon, the silicon melt is melted and drawn downward while solidifying the silicon melt.
A method for casting polycrystalline silicon, wherein the cooling copper mold has a low oxygen content and a low oxygen partial pressure in the chamber.
Here, “the oxygen content of the copper mold is low” means that the oxygen content is lower than that of a conventionally used copper mold having an oxygen content of about 100 to 500 (mass ppm).
(3)前記冷却銅モールドの酸素含有率が50(質量ppm)以下であり、且つ前記チャンバ内の酸素分圧が0.01kg/cm2以下であることを特徴とする、上記(2)に記載の多結晶シリコンの鋳造方法。 (3) The oxygen content of the cooling copper mold is 50 (mass ppm) or less, and the oxygen partial pressure in the chamber is 0.01 kg / cm 2 or less. Casting method of polycrystalline silicon.
本発明の方法によれば、FT−IR法(ASTM F121−79)で測定した格子間酸素濃度の低い多結晶シリコンウェーハを鋳造することができる。
この多結晶シリコンウェーハを基板として用いることにより、時間経過に伴う変換効率の低下を低減した太陽電池を実現できる。
According to the method of the present invention, a polycrystalline silicon wafer having a low interstitial oxygen concentration measured by the FT-IR method (ASTM F121-79) can be cast.
By using this polycrystalline silicon wafer as a substrate, it is possible to realize a solar cell in which a decrease in conversion efficiency with the passage of time is reduced.
以下に、本発明を導くに至った実験結果について詳述する。
まず、本発明者は、電磁鋳造法がシリコン材料と銅モールドとが非接触状態で鋳造される方法であるにも関らず、銅モールドに、従来用いられていた銅モールドより酸素含有率が低いものを用いることにより、多結晶シリコンウェーハの格子間酸素濃度を低減させ得ることを知見した。また、同時にチャンバ内の酸素分圧を低減させることが有効であることを併せて知見した。
表1は、酸素含有率(質量ppm)の異なる銅モールドを複数用意し、それぞれの銅モールドで電磁鋳造法により、チャンバ内の酸素分圧の様々な条件の下で、ボロンをドーピングした抵抗率1.5Ωcmのp型の多結晶シリコンを鋳造し、多結晶シリコンウェーハの格子間酸素濃度をFT−IR法(ASTM F121−79)で測定した結果を示している。
なお、従来の銅モールドの酸素含有率は100〜500(質量ppm)程度である。
また、チャンバ内の酸素分圧は、チャンバ内のアルゴンガス置換を繰り返し行うことにより低減したものである。
The experimental results that led to the present invention are described in detail below.
First, the inventor found that although the electromagnetic casting method is a method in which a silicon material and a copper mold are cast in a non-contact state, the copper mold has a higher oxygen content than a conventionally used copper mold. It has been found that the interstitial oxygen concentration of a polycrystalline silicon wafer can be reduced by using a low one. At the same time, it has been found that it is effective to reduce the oxygen partial pressure in the chamber.
Table 1 shows the resistivity of boron doped with various copper molds with different oxygen contents (mass ppm), each of which was electromagnetically cast under various conditions of oxygen partial pressure in the chamber. The figure shows the results of casting 1.5-Ωcm p-type polycrystalline silicon and measuring the interstitial oxygen concentration of the polycrystalline silicon wafer by the FT-IR method (ASTM F121-79).
In addition, the oxygen content rate of the conventional copper mold is about 100-500 (mass ppm).
The oxygen partial pressure in the chamber is reduced by repeatedly performing argon gas replacement in the chamber.
表1に示すように、ウェーハの格子間酸素濃度は、チャンバ内の酸素分圧が、0.01kg/cm3以下で、且つ銅モールドの酸素含有率を50質量ppm以下とすることによって1.0×1017atoms/cm3以下に低減させることができることがわかる。
これは、シリコン中に含まれる酸素は、シリコン融液が高温状態のときの短時間のモールドとの接触による経路と、シリコン融液がその後比較的低温に至るまでの間での、チャンバ内の雰囲気からの経路との、2つの異なる経路から混入すると考えられるからである。
なお、リン等をドーピングした抵抗率3Ωcmのn型多結晶シリコンの場合も上記と同様の条件で試験を行い、同様の条件の下で、多結晶シリコンウェーハの格子間酸素濃度を1.0×1017atoms/cm3以下とすることができた。
As shown in Table 1, the interstitial oxygen concentration of the wafer is 1.0 × 10 5 when the oxygen partial pressure in the chamber is 0.01 kg / cm 3 or less and the oxygen content of the copper mold is 50 mass ppm or less. It can be seen that it can be reduced to 17 atoms / cm 3 or less.
This is because the oxygen contained in the silicon is in the chamber between the path due to the contact with the mold for a short time when the silicon melt is at a high temperature and until the silicon melt subsequently reaches a relatively low temperature. It is because it is thought that it mixes from two different routes, the route from the atmosphere.
In the case of n-type polycrystalline silicon having a resistivity of 3 Ωcm doped with phosphorus or the like, the test was performed under the same conditions as described above, and under the same conditions, the interstitial oxygen concentration of the polycrystalline silicon wafer was 1.0 × 10 17. atoms / cm 3 or less could be achieved.
発明者は、上記の如くして、格子間酸素濃度が1.0×1017atoms/cm3以下の多結晶シリコンウェーハを鋳造できるに至り、これらを基板とする太陽電池を複数製造して、上記の変換効率の低下を評価する実験を行った。その評価結果を図3に示す。
なお、実験に用いた多結晶シリコンウェーハは、ボロンをドーピングした、抵抗率1.5Ωcmのp型ウェーハである。
As described above, the inventor has been able to cast a polycrystalline silicon wafer having an interstitial oxygen concentration of 1.0 × 10 17 atoms / cm 3 or less, and manufactured a plurality of solar cells using these as substrates. An experiment was conducted to evaluate the decrease in conversion efficiency. The evaluation results are shown in FIG.
The polycrystalline silicon wafer used in the experiment is a p-type wafer having a resistivity of 1.5 Ωcm doped with boron.
図3に示すように、酸素濃度が1.0×1017atoms/cm3以下の範囲では、酸素濃度が低くなるにつれ、急激に太陽電池の変換効率の低下を抑制することができることがわかる。
本発明によれば、表1に示すように、1.0×1016〜1.0×1017atoms/cm3の範囲の格子間酸素濃度のウェーハを製造することができるため、このウェーハを基板として用いることにより、太陽電池の変換効率の低下率を3%以下まで大幅に低下させることができる。
なお、酸素濃度が1.0×1017atoms/cm3以下のn型多結晶シリコンウェーハでも同様に上述の太陽電池の変換効率の低下率を評価する試験を行い、変換効率の低下率が3%以下となることがわかった。
As shown in FIG. 3, it can be seen that when the oxygen concentration is in the range of 1.0 × 10 17 atoms / cm 3 or less, the decrease in conversion efficiency of the solar cell can be rapidly suppressed as the oxygen concentration decreases.
According to the present invention, as shown in Table 1, since a wafer having an interstitial oxygen concentration in the range of 1.0 × 10 16 to 1.0 × 10 17 atoms / cm 3 can be produced, this wafer can be used as a substrate. As a result, the reduction rate of the conversion efficiency of the solar cell can be significantly reduced to 3% or less.
In addition, even in an n-type polycrystalline silicon wafer having an oxygen concentration of 1.0 × 10 17 atoms / cm 3 or less, a test for evaluating the reduction rate of the conversion efficiency of the above-described solar cell was similarly conducted, and the conversion efficiency reduction rate was 3% or less. I found out that
1 チャンバ
2 冷却モールド
3 誘導コイル
4 ヒータ
5 インゴット
6 シリコン材料
7 溶融シリコン
8 引き下げ装置
1 chamber
2 Cooling mold
3 induction coil
4 Heater
5 Ingot
6 Silicon material
7 Molten silicon
8 Pulling device
Claims (3)
前記冷却銅モールドの酸素含有率が低く、且つ前記チャンバ内の酸素分圧が低いことを特徴とする、多結晶シリコンの鋳造方法。 A bottomless copper cooling mold in which at least a part in the axial direction is divided into a plurality of portions in the circumferential direction is disposed in the induction coil of the chamber, and silicon fusion is performed in the cooling copper mold by electromagnetic induction heating by the induction coil. In the casting method of polycrystalline silicon, the liquid is melted and pulled down while solidifying the silicon melt.
A method for casting polycrystalline silicon, wherein the cooling copper mold has a low oxygen content and a low oxygen partial pressure in the chamber.
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| JP2010181733A JP2012041211A (en) | 2010-08-16 | 2010-08-16 | Polycrystalline silicon wafer and method for casting the same |
| KR1020110080553A KR20120016591A (en) | 2010-08-16 | 2011-08-12 | Polycrystalline silicon wafer and casting method of polycrystalline silicon |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2016143868A (en) * | 2015-02-05 | 2016-08-08 | 信越化学工業株式会社 | Rear face junction type solar cell |
| WO2019231062A1 (en) * | 2018-05-29 | 2019-12-05 | 엘지전자 주식회사 | Compound semiconductor solar cell and method for manufacturing same |
-
2010
- 2010-08-16 JP JP2010181733A patent/JP2012041211A/en not_active Withdrawn
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- 2011-08-12 KR KR1020110080553A patent/KR20120016591A/en not_active Application Discontinuation
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2016143868A (en) * | 2015-02-05 | 2016-08-08 | 信越化学工業株式会社 | Rear face junction type solar cell |
| WO2019231062A1 (en) * | 2018-05-29 | 2019-12-05 | 엘지전자 주식회사 | Compound semiconductor solar cell and method for manufacturing same |
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| KR20120016591A (en) | 2012-02-24 |
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