JP2004179337A - Method of forming solar cell element - Google Patents

Method of forming solar cell element Download PDF

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JP2004179337A
JP2004179337A JP2002342881A JP2002342881A JP2004179337A JP 2004179337 A JP2004179337 A JP 2004179337A JP 2002342881 A JP2002342881 A JP 2002342881A JP 2002342881 A JP2002342881 A JP 2002342881A JP 2004179337 A JP2004179337 A JP 2004179337A
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metal
semiconductor substrate
firing
paste
electrode
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JP3968001B2 (en
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Yuko Fukawa
祐子 府川
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Kyocera Corp
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Kyocera Corp
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming a solar cell element which is capable of protecting a semiconductor substrate against cracking and superior in output characteristics. <P>SOLUTION: An opposite conductivity-type semiconductor impurity is diffused into one main surface of one conductivity-type semiconductor substrate 1, a surface electrode 4 whose main component is a first metal is formed on the main surface of the semiconductor substrate 1, a back electrode composed of a current collector 5 whose main component is a second metal, and an output port 6 whose main component is a third metal more easily solder-wettable than the second metal is formed on the other main surface of the semiconductor substrate for the formation of the solar cell element. Paste which is mainly formed of the second metal to serve as the current collector 5 of the back electrode is applied on the other surface of the semiconductor substrate 1, the substrate 1 is subjected to first baking, paste which is mainly formed of the first metal to serve as the surface electrode 4 is applied on the one main surface of the semiconductor substrate 1, the substrate 1 is subjected to second baking, paste which is mainly formed of the third metal to serve as the output port 6 of the back electrode is applied on the other main surface, and then the substrate is subjected to third baking. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は太陽電池素子の形成方法に関し、特に金属ペーストを焼き付けて表面電極と裏面電極を形成する太陽電池素子の形成方法に関する。
【０００２】
【従来の技術】
従来の太陽電池素子を図１に示す。例えばＰ型半導体基板１の表面近傍の全面に一定の深さまでＮ型不純物を拡散させてＮ型を呈する拡散層２を設け、半導体基板１の表面に窒化シリコン膜などから成る反射防止膜３を設け、表面に表面電極４を設けるとともに、裏面にアルミニウムなどから成る集電部５と銀などから成る出力取出部６とで構成される裏面電極５、６を設けている。また半導体基板１の裏面には高濃度のＰ型拡散層７が形成される。
【０００３】
これらの太陽電池素子の表面電極４は反射防止膜３の上に表面電極材料を塗布し焼成することによって、電極材料の下の反射防止膜３を溶融させ半導体基板と直接接触させるいわゆるファイヤースルー法が一般的である。
【０００４】
またこれらの太陽電池素子の裏面電極５、６を形成するには、アルミニウムからなる第二の金属を主成分とするペーストを半導体基板１の裏面の一部を除いた大部分に塗布して乾燥した後、この第二の金属を主成分とするペーストを塗布しなかった部分とその周縁部を覆うように銀からなる第三の金属を主成分とするペーストを塗布して乾燥し、最後に半導体基板１の表面に銀からなる第一の金属を主成分とするペーストを塗布して乾燥して、第一の金属を主成分とするペーストと第二の金属を主成分とするペーストと第三の金属を主成分とするペーストとを同時に焼成する方法、すなわち同時焼成法が従来用いられてきた（例えば特許文献１参照。）。
【０００５】
また、アルミニウムからなる第二の金属を主成分とするペーストを半導体基板１の裏面の一部を除いた大部分に塗布して乾燥した後、この第二の金属を主成分とするペーストを塗布しなかった部分とその周縁部を覆うように銀からなる第三の金属を主成分とするペーストを塗布して乾燥して１回目の焼成を行った後、半導体基板１の表面に銀からなる第一の金属を主成分とするペーストを塗布して乾燥して２回目の焼成を行う方法もある（例えば特許文献１参照。）。
【０００６】
さらに、アルミニウムからなる第二の金属を主成分とするペーストを半導体基板１の裏面の一部を除いた大部分に塗布して乾燥して１回目の焼成を行った後、この第二の金属を主成分とするペーストを塗布しなかった部分とその周縁部を覆うように銀からなる第三の金属を主成分とするペーストを塗布して乾燥した後、半導体基板１の表面に銀からなる第一の金属を主成分とするペーストを塗布して乾燥して２回目の焼成を行う方法もある（例えば特許文献１参照。）。
【０００７】
これによって半導体基板１の裏面には、集電部５とはんだ濡れ性の良好な出力取出部６が形成されるとともに、集電部５の下の半導体基板１には高濃度のＰ型拡散層７が形成される。
【０００８】
その後、表面電極４および裏面電極の出力取出部６上にはんだ（不図示）を被着して、太陽電池素子を直列もしくは並列に接続するインナーリードを接続する。
【０００９】
【特許文献１】
特開平１０−３３５２６７号公報
【００１０】
【発明が解決しようとする課題】
ところが、この従来の太陽電池素子の形成方法では、焼成の際に集電部５のアルミニウムと出力取出部６の銀との重なり部、つまり熱膨張係数の異なる半導体基板１とアルミニウムと銀との重なり部に応力が発生し、半導体基板１の割れの原因になるという問題があった。
【００１１】
また、アルミニウムを焼成してから表裏面に銀を塗布して同時に焼成する方法によれば、上記問題は緩和されるものの、表面電極４をファイヤースルー法により形成する場合、表裏面の焼成の温度が低すぎると反射防止膜３を充分に溶融させることができず、表面電極４の半導体基板１との接触抵抗を十分に低下させることができないという問題が発生し、焼成温度が高すぎると集電部５のアルミニウムと出力取出部６の銀との重なり部、つまり熱膨張係数の異なる半導体基板１とアルミニウムと銀との重なり部に応力が発生し、半導体基板１の割れの原因になるという問題が再度発生してしまうことがあった。
【００１２】
本発明は、このような従来技術の問題点に鑑みてなされたものであり、半導体基板の割れを防止できるとともに、出力特性の良好な太陽電池素子の形成方法を提供することを目的とする。
【００１３】
【課題を解決するための手段】
上記目的を達成するために、本発明に係る太陽電池素子の形成方法では、一導電型を呈する半導体基板の一主面側に逆導電型半導体不純物を拡散するとともに、第一の金属を主成分とする表面電極を形成し、他の主面側に第二の金属を主成分とする集電部とこの第二の金属よりも半田濡れ性のよい第三の金属を主成分とする出力取出部とから成る裏面電極を形成する太陽電池素子の形成方法において、前記半導体基板の他の主面側に前記裏面電極の集電部となる第二の金属を主成分とするペーストを塗布して１回目の焼成を行い、一主面側に前記表面電極となる第一の金属を主成分とするペーストを塗布して２回目の焼成を行い、その後他の主面側に前記裏面電極の出力取出部となる第三の金属を主成分とするペーストを塗布して３回目の焼成を行うことを特徴とする。
【００１４】
前記太陽電池素子の形成方法では、前記焼成は１回目の焼成よりも２回目の焼成の温度が低いとともに、２回目の焼成よりも３回目の焼成の温度が低いことが望ましい。
【００１５】
上記太陽電池素子の形成方法では、前記第一の金属と前記第三の金属が銀からなることが望ましい。
【００１６】
また、上記太陽電池素子の形成方法では、前記半導体基板がシリコンからなり、前記第三の金属を主成分とするペーストにアルミニウムを含有することが望ましい。
【００１７】
また、上記太陽電池素子の形成方法では、前記第二の金属がアルミニウムからなることが望ましい。
【００１８】
【発明の実施の形態】
以下、本発明の実施形態を詳細に説明する。
本発明に係る太陽電池素子の構造も基本的には従来の太陽電池素子と同様である。すなわち、例えばＰ型半導体基板１の表面近傍全面に一定の深さまでＮ型不純物を拡散させてＮ型を呈する拡散層２を設け、半導体基板１の表面に窒化シリコン膜などから成る反射防止膜３を設け、表面に表面電極４を設けるとともに、裏面にはアルミニウムなどから成る集電部５と銀などから成る出力取出部６とで構成される裏面電極を設けている。また半導体基板１の裏面には高濃度のＰ型拡散層７が形成される。
【００１９】
このような太陽電池素子は、例えばＰ型半導体基板１をＮ型不純物雰囲気中で熱処理などして、表面領域の全面に一定の深さまでＮ型不純物を拡散させてＮ型を呈する拡散層２を形成し、ＣＶＤ法などで反射防止膜３を形成して拡散層２を分離した後、表面電極４および集電部５と電極取出部６とから成る裏面電極が形成されるとともに、集電部５の下の半導体基板１に高濃度のＰ型拡散層７が形成される。表面電極４は反射防止膜３の上に表面電極材料を塗布し焼成することによって、電極材料の下の反射防止膜３を溶融させ半導体基板と直接接触させるいわゆるファイヤースルー法をもちいる。
【００２０】
上記表面電極４、集電部５、および電極取出部６は、以下のように形成される。すなわち、半導体基板１の裏面に集電部５となるアルミニウムからなる第二の金属を主成分とするペーストを塗布して約７２０〜８５０℃で３〜３０分程度の１回目の焼成を行う。このときの焼成温度が７２０℃以下であったり、焼成時間が３分以下であったりすると、アルミニウムが十分に半導体基板１に拡散されず、太陽電池素子の特性低下を招くおそれがある。また、焼成温度が８５０℃以上であったり、焼成時間が３０分以上であったりすると、拡散層２の不純物が再度拡散されることによって接合が深くなったり、表面電極４が拡散層２の接合を破壊するなどの問題が発生するおそれがある。
【００２１】
次に半導体基板１の表面に表面電極４となる例えば銀からなる第一の金属を主成分とするペーストを塗布し、約７００〜８００℃で１〜２０分程度の２回目の焼成を行う。このときの焼成温度が７００℃以下であったり、焼成時間が１分以下であったりすると、銀が十分に焼結せずに剥離の原因となったり、接触抵抗が十分に低下しないなどの問題が発生するおそれがある。また、焼成温度が８００℃以上であったり、焼成時間が２０分以上であったりすると、拡散層２の不純物が再度拡散されることによって接合が深くなったり、表面電極４が拡散層２の接合を破壊するなどの問題が発生するおそれがある。
【００２２】
次に、半導体基板１の裏面に出力取出部６となる例えば銀からなる第三の金属を主成分とするペーストを塗布し、約６５０〜７５０℃で０．５〜１５分程度の３回目の焼成を行う。このときの焼成温度が６５０℃以下であったり、焼成時間が０．５分以下であったりすると、銀が充分に焼結せずに剥離の原因となったり、接触抵抗が十分に低下しないなどの問題が発生するおそれがある。反対に焼成温度が７５０℃以上であったり、焼成時間が１５分以上であったりすると、上記と同様に拡散層２の不純物が再度拡散されることによって接合が深くなったり、表面電極４が拡散層２の接合を破壊するなどの問題が発生するおそれがある。
【００２３】
この方法によれば、集電部５のアルミニウムからなる第二の金属は１回目の焼成によって焼結する。したがって、その後その上に出力取出部６となる銀からなる第三の金属を主成分とするペーストを塗布して３回目の焼成を行っても、アルミニウムはすでに焼結しているので、銀とは合金化しにくい。これによって熱膨張係数の異なる半導体基板１とアルミニウムと銀との重なり部での応力が緩和され、従来問題であったこの重なり部での応力に起因する半導体基板１の割れを低減できる。また２回目の焼成により表面電極４は半導体基板１と接触する。したがって３回目の焼成の際、裏面電極のアルミニウムと銀の合金化を防ぐため焼成温度を低くしても、表面電極の接触抵抗が十分に低下しないなどの問題の発生を防ぐことができる。
【００２４】
前記焼成は１回目の焼成よりも２回目の焼成の温度が低いとともに、２回目の焼成よりも３回目の焼成の温度が低いことが望ましい。このようにすることにより、１回目の焼成で焼結したアルミニウムは２回目、３回目の焼成の影響を受けにくくなり、２回目の焼成で焼結した表面電極４の銀は３回目の焼成の影響を受けにくくなる。これにより、半導体基板１とアルミニウムと銀との重なり部での応力が緩和され、表面電極に起因する接合の破壊も発生しない。
【００２５】
このような金属を主成分とするペーストは、他に溶剤とエチルセルロース等のバインダーを混合して構成される。
【００２６】
また、出力取出部６として塗布される銀からなる第三の金属を主成分とするペーストにはアルミニウムを含有することが望ましい。半導体基板１に使用するシリコンへの拡散係数の大きなアルミニウムを銀に含有させることにより、１回目や２回目のの焼成よりも低温の３回目の焼成でも出力取出部６のシリコンとの接着強度を確保することができるからである。
【００２７】
なお、本発明は上記実施形態に限定されるものではなく、本発明の範囲内で多くの修正および変更を加えることができる。例えばペーストを塗布した後の乾燥は、次のペーストを塗布するときに印刷機の作業テーブルやスクリーンに前のペーストが付着するといった問題がなければ省略してもよい。
【００２８】
第１および第３の金属としては金や白金を用いることもできる。
【００２９】
【発明の効果】
以上のように、本発明に係る太陽電池素子の形成方法によれば、半導体基板の他の主面側に裏面電極の集電部となる第二の金属を主成分とするペーストを塗布して１回目の焼成を行い、一主面側に表面電極となる第一の金属を主成分とするペーストを塗布して２回目の焼成を行い、その後他の主面側に裏面電極の出力取出部となる第三の金属を主成分とするペーストを塗布して３回目の焼成を行うことにより、銀からなる第三の金属を主成分とするペーストを塗布して３回目の焼成を行っても、アルミニウムはすでに焼結しているので、銀とは合金化しにくい。これによって熱膨張係数の異なる半導体基板１とアルミニウムと銀との重なり部での応力が緩和され、従来問題であったこの重なり部での応力に起因する半導体基板１の割れを低減できる。また２回目の焼成により表面電極４は半導体基板１と接触しているので３回目の焼成の際、裏面電極のアルミニウムと銀の合金化を防ぐため焼成温度を低くしても、表面電極の接触抵抗が十分に低下しないなどの問題の発生を防ぐことができる。
【００３０】
本発明の形成方法によって得られる太陽電池素子は、特に高特性を要求される太陽電池モジュールに使用すれば、その効果を有効に発揮する。
【図面の簡単な説明】
【図１】太陽電池素子の構造を説明する図である。
【符号の説明】
１・・・半導体基板、２・・・拡散層、３・・・反射防止膜、４・・・表面電極、５・・・集電部、６・・・出力取出部、７・・・高濃度Ｐ型拡散層[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for forming a solar cell element, and more particularly to a method for forming a solar cell element in which a front electrode and a back electrode are formed by baking a metal paste.
[0002]
[Prior art]
FIG. 1 shows a conventional solar cell element. For example, an N-type impurity is diffused to a predetermined depth over the entire surface near the surface of the P-type semiconductor substrate 1 to provide an N-type diffusion layer 2, and an anti-reflection film 3 made of a silicon nitride film or the like is provided on the surface of the semiconductor substrate 1. In addition, the front surface electrode 4 is provided on the front surface, and the back surface electrodes 5 and 6 composed of the current collecting portion 5 made of aluminum or the like and the output extraction portion 6 made of silver or the like are provided on the back surface. On the back surface of the semiconductor substrate 1, a high-concentration P-type diffusion layer 7 is formed.
[0003]
The surface electrode 4 of these solar cell elements is coated with a surface electrode material on the anti-reflection film 3 and baked to melt the anti-reflection film 3 under the electrode material and directly contact the semiconductor substrate, a so-called fire-through method Is common.
[0004]
Further, in order to form the back electrodes 5 and 6 of these solar cell elements, a paste mainly composed of a second metal made of aluminum is applied to most of the semiconductor substrate 1 except for a part of the back surface and dried. After that, a paste containing a third metal as a main component made of silver is applied so as to cover a portion where the paste containing a second metal as a main component was not applied and a peripheral portion thereof, and is dried. A paste composed mainly of a first metal made of silver is applied to the surface of the semiconductor substrate 1 and dried, and a paste composed mainly of a first metal and a paste composed mainly of a second metal are formed. A method of simultaneously firing a paste containing three metals as main components, that is, a simultaneous firing method has been conventionally used (for example, see Patent Document 1).
[0005]
Further, a paste mainly composed of the second metal made of aluminum is applied to most of the back surface of the semiconductor substrate 1 except for a part thereof and dried, and then the paste mainly composed of the second metal is applied. A paste mainly composed of a third metal made of silver is applied so as to cover the unprocessed portion and the peripheral portion thereof, dried and baked for the first time, and then the surface of the semiconductor substrate 1 is made of silver. There is also a method in which a paste containing a first metal as a main component is applied, dried, and fired a second time (for example, see Patent Document 1).
[0006]
Further, a paste mainly composed of a second metal made of aluminum is applied to most of the semiconductor substrate 1 except for a part of the back surface, dried and baked for the first time. After applying a paste composed mainly of a third metal composed of silver so as to cover a part where the paste composed mainly of the third metal was not applied and its peripheral part and drying it, the surface of the semiconductor substrate 1 is composed of silver There is also a method in which a paste containing a first metal as a main component is applied, dried, and fired a second time (for example, see Patent Document 1).
[0007]
As a result, a current collecting portion 5 and an output extraction portion 6 having good solder wettability are formed on the back surface of the semiconductor substrate 1, and a high concentration P-type diffusion layer is formed on the semiconductor substrate 1 below the current collecting portion 5. 7 is formed.
[0008]
After that, solder (not shown) is applied on the surface electrode 4 and the output extraction portion 6 of the back electrode, and inner leads for connecting the solar cell elements in series or in parallel are connected.
[0009]
[Patent Document 1]
JP-A-10-335267
[Problems to be solved by the invention]
However, in this conventional method for forming a solar cell element, at the time of firing, an overlapping portion of aluminum of the current collecting portion 5 and silver of the output extracting portion 6, that is, the semiconductor substrate 1 having a different coefficient of thermal expansion from the aluminum and silver. There is a problem that stress is generated in the overlapping portion, which causes cracking of the semiconductor substrate 1.
[0011]
According to the method of baking aluminum and then applying silver on the front and back surfaces and baking at the same time, the above problem is alleviated. Is too low, the antireflection film 3 cannot be melted sufficiently, and the contact resistance of the surface electrode 4 with the semiconductor substrate 1 cannot be sufficiently reduced. It is said that stress is generated at the overlapping portion between the aluminum of the electrical portion 5 and the silver of the output extraction portion 6, that is, the overlapping portion between the semiconductor substrate 1 and the aluminum and silver having different thermal expansion coefficients, which causes the semiconductor substrate 1 to crack. Sometimes the problem occurred again.
[0012]
The present invention has been made in view of such problems of the related art, and an object of the present invention is to provide a method for forming a solar cell element that can prevent a semiconductor substrate from cracking and has good output characteristics.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, in a method for forming a solar cell element according to the present invention, a semiconductor material having one conductivity type is diffused with a semiconductor impurity of a reverse conductivity type on one principal surface side, and a first metal is mainly contained. Forming a front surface electrode, and collecting, on the other main surface side, a current collector mainly composed of a second metal and an output extraction mainly composed of a third metal having better solder wettability than the second metal. In the method for forming a solar cell element forming a back electrode comprising a portion, a paste containing a second metal as a main component serving as a current collector of the back electrode is applied to the other main surface of the semiconductor substrate. A first baking is performed, a paste mainly composed of a first metal to be the surface electrode is applied to one main surface side, and a second baking is performed. Then, the output of the back electrode is applied to another main surface side. A third baking paste, which is to be the extraction part, is applied and the third baking is performed. And performing.
[0014]
In the method for forming a solar cell element, it is preferable that the temperature of the second firing is lower than that of the first firing, and that the temperature of the third firing is lower than the second firing.
[0015]
In the method for forming a solar cell element, the first metal and the third metal are preferably made of silver.
[0016]
In the method for forming a solar cell element, it is preferable that the semiconductor substrate is made of silicon, and the paste containing the third metal as a main component contains aluminum.
[0017]
In the method for forming a solar cell element, the second metal is preferably made of aluminum.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
The structure of the solar cell element according to the present invention is basically the same as the conventional solar cell element. That is, for example, an N-type impurity is diffused to a certain depth over the entire surface near the surface of the P-type semiconductor substrate 1 to provide an N-type diffusion layer 2, and the anti-reflection film 3 made of a silicon nitride film or the like is provided on the surface of the semiconductor substrate 1. And a front surface electrode 4 is provided on the front surface, and a back surface electrode composed of a current collecting portion 5 made of aluminum or the like and an output extraction portion 6 made of silver or the like is provided on the back surface. On the back surface of the semiconductor substrate 1, a high-concentration P-type diffusion layer 7 is formed.
[0019]
In such a solar cell element, for example, a P-type semiconductor substrate 1 is heat-treated in an N-type impurity atmosphere to diffuse an N-type impurity to a certain depth over the entire surface region to form an N-type diffusion layer 2. After forming the antireflection film 3 by the CVD method or the like to separate the diffusion layer 2, the front surface electrode 4 and the back surface electrode composed of the current collecting portion 5 and the electrode extraction portion 6 are formed. 5, a high-concentration P-type diffusion layer 7 is formed in the semiconductor substrate 1 below. The surface electrode 4 employs a so-called fire-through method in which the surface electrode material is applied on the antireflection film 3 and baked to melt the antireflection film 3 under the electrode material and directly contact the semiconductor substrate.
[0020]
The above-mentioned surface electrode 4, current collecting part 5, and electrode extraction part 6 are formed as follows. That is, a paste mainly composed of a second metal made of aluminum to be the current collector 5 is applied to the back surface of the semiconductor substrate 1 and the first baking is performed at about 720 to 850 ° C. for about 3 to 30 minutes. If the firing temperature at this time is 720 ° C. or less, or the firing time is 3 minutes or less, aluminum may not be sufficiently diffused into the semiconductor substrate 1, which may cause deterioration in characteristics of the solar cell element. If the firing temperature is 850 ° C. or more, or the firing time is 30 minutes or more, the impurities in the diffusion layer 2 are diffused again to deepen the junction, or the surface electrode 4 is bonded to the diffusion layer 2. There is a possibility that problems such as destruction may occur.
[0021]
Next, a paste containing, as a main component, a first metal made of, for example, silver, which becomes the surface electrode 4, is applied to the surface of the semiconductor substrate 1, and second baking is performed at about 700 to 800 ° C. for about 1 to 20 minutes. If the sintering temperature at this time is 700 ° C. or less or the sintering time is 1 minute or less, silver may not be sufficiently sintered, causing peeling, or the contact resistance may not be sufficiently reduced. May occur. If the firing temperature is 800 ° C. or more, or the firing time is 20 minutes or more, the impurities in the diffusion layer 2 are diffused again to deepen the bonding, or the surface electrode 4 is bonded to the diffusion layer 2. There is a possibility that problems such as destruction may occur.
[0022]
Next, on the back surface of the semiconductor substrate 1, a paste mainly composed of a third metal, for example, silver, which becomes the output extraction section 6, is applied, and the third time is performed at about 650 to 750 ° C. for about 0.5 to 15 minutes. Perform baking. If the firing temperature at this time is 650 ° C. or less, or the firing time is 0.5 minute or less, the silver does not sinter sufficiently and causes peeling, and the contact resistance does not decrease sufficiently. Problem may occur. Conversely, if the baking temperature is 750 ° C. or more, or the baking time is 15 minutes or more, the impurities in the diffusion layer 2 are diffused again as described above, so that the junction is deepened or the surface electrode 4 is diffused. There is a possibility that a problem such as breaking of the junction of the layer 2 may occur.
[0023]
According to this method, the second metal made of aluminum of the current collector 5 is sintered by the first firing. Therefore, even after that, a paste mainly composed of a third metal made of silver, which becomes the output extraction portion 6, is applied thereon and the third baking is performed. Is difficult to alloy. As a result, stress at the overlapping portion between the semiconductor substrate 1 having different thermal expansion coefficients and aluminum and silver is reduced, and cracking of the semiconductor substrate 1 caused by the stress at the overlapping portion, which has been a problem in the related art, can be reduced. Further, the surface electrode 4 comes into contact with the semiconductor substrate 1 by the second baking. Therefore, at the time of the third firing, even if the firing temperature is lowered in order to prevent alloying of aluminum and silver of the back electrode, it is possible to prevent problems such as the contact resistance of the front electrode from not being sufficiently reduced.
[0024]
It is preferable that the temperature of the second firing is lower than that of the first firing, and that the temperature of the third firing is lower than the second firing. In this way, the aluminum sintered in the first firing is less affected by the second and third firings, and the silver of the surface electrode 4 sintered in the second firing is reduced by the third firing. Less susceptible. This alleviates the stress at the overlapping portion between the semiconductor substrate 1 and aluminum and silver, and does not cause breakage of the junction caused by the surface electrode.
[0025]
Such a paste containing a metal as a main component is formed by mixing a solvent and a binder such as ethyl cellulose.
[0026]
It is desirable that the paste mainly composed of the third metal made of silver, which is applied as the output extraction section 6, contains aluminum. By including aluminum having a large diffusion coefficient into silicon used for the semiconductor substrate 1 in silver, the bonding strength between the output extraction portion 6 and silicon can be improved even in the third firing at a lower temperature than in the first or second firing. This is because it can be secured.
[0027]
The present invention is not limited to the above embodiment, and many modifications and changes can be made within the scope of the present invention. For example, the drying after applying the paste may be omitted if there is no problem that the previous paste adheres to the work table or screen of the printing press when applying the next paste.
[0028]
Gold and platinum can also be used as the first and third metals.
[0029]
【The invention's effect】
As described above, according to the method for forming a solar cell element according to the present invention, a paste containing a second metal as a main component serving as a current collector of a back electrode is applied to the other main surface of the semiconductor substrate. The first baking is performed, a paste mainly composed of a first metal to be a surface electrode is applied to one main surface, and the second baking is performed, and then the output extraction portion of the back electrode is formed on the other main surface. By applying the paste mainly containing the third metal and performing the third baking, it is possible to apply the paste mainly containing the third metal composed of silver and perform the third baking. Since aluminum is already sintered, it is difficult to alloy with silver. This alleviates the stress at the overlapping portion between the semiconductor substrate 1 having different thermal expansion coefficients and aluminum and silver, and can reduce the cracking of the semiconductor substrate 1 caused by the stress at the overlapping portion, which has been a problem in the related art. In addition, since the front electrode 4 is in contact with the semiconductor substrate 1 by the second firing, even if the firing temperature is lowered during the third firing to prevent alloying of aluminum and silver on the back electrode, the contact of the front electrode can be prevented. It is possible to prevent problems such as insufficient reduction in resistance.
[0030]
The solar cell element obtained by the formation method of the present invention exhibits its effects effectively, particularly when used in a solar cell module that requires high characteristics.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating the structure of a solar cell element.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 2 ... Diffusion layer, 3 ... Anti-reflection film, 4 ... Surface electrode, 5 ... Current collecting part, 6 ... Output extraction part, 7 ... High Concentration P-type diffusion layer

Claims (5)

一導電型を呈する半導体基板の一主面側に逆導電型半導体不純物を拡散するとともに、第一の金属を主成分とする表面電極を形成し、他の主面側に第二の金属を主成分とする集電部とこの第二の金属よりも半田濡れ性のよい第三の金属を主成分とする出力取出部とから成る裏面電極を形成する太陽電池素子の形成方法において、前記半導体基板の他の主面側に前記裏面電極の集電部となる第二の金属を主成分とするペーストを塗布して１回目の焼成を行い、一主面側に前記表面電極となる第一の金属を主成分とするペーストを塗布して２回目の焼成を行い、その後他の主面側に前記裏面電極の出力取出部となる第三の金属を主成分とするペーストを塗布して３回目の焼成を行うことを特徴とする太陽電池素子の形成方法。On the one main surface side of the semiconductor substrate having one conductivity type, the opposite conductivity type semiconductor impurity is diffused, and a surface electrode mainly composed of the first metal is formed, and the second metal is mainly formed on the other main surface side. A method of forming a back electrode comprising a current collecting portion as a component and an output extracting portion mainly composed of a third metal having better solder wettability than the second metal; On the other main surface side, a paste containing a second metal as a main component serving as a current collecting portion of the back electrode is applied and baked for the first time, and the first main surface side serving as the front electrode is formed on the first main surface side. A second paste is applied by applying a paste containing a metal as a main component, and then a third paste containing a third metal as a main component serving as an output extraction portion of the back electrode is applied to the other main surface. A method for forming a solar cell element. 前記焼成は１回目の焼成よりも２回目の焼成の温度が低いとともに、２回目の焼成よりも３回目の焼成の温度が低いことを特徴とする請求項１に記載の太陽電池素子の形成方法。2. The method of claim 1, wherein a temperature of a second firing is lower than that of the first firing, and a temperature of a third firing is lower than the second firing. 3. . 前記第一の金属と前記第三の金属が銀からなることを特徴とする請求項１または２に記載の太陽電池素子の形成方法。The method according to claim 1, wherein the first metal and the third metal are made of silver. 前記半導体基板がシリコンからなり、前記第三の金属を主成分とするペーストにアルミニウムを含有することを特徴とする請求項１ないし３のいずれかに記載の太陽電池素子の形成方法。The method according to any one of claims 1 to 3, wherein the semiconductor substrate is made of silicon, and the paste containing the third metal as a main component contains aluminum. 前記第二の金属がアルミニウムからなることを特徴とする請求項１ないし４のいずれかに記載の太陽電池素子の形成方法。5. The method according to claim 1, wherein the second metal is made of aluminum.
JP2002342881A 2002-11-26 2002-11-26 Method for forming solar cell element Expired - Fee Related JP3968001B2 (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017109835A1 (en) * 2015-12-21 2017-06-29 三菱電機株式会社 Solar cell manufacturing method

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017109835A1 (en) * 2015-12-21 2017-06-29 三菱電機株式会社 Solar cell manufacturing method
JPWO2017109835A1 (en) * 2015-12-21 2018-03-29 三菱電機株式会社 Manufacturing method of solar cell

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