JP3813752B2

JP3813752B2 - Semiconductor device acceleration test method and apparatus

Info

Publication number: JP3813752B2
Application number: JP00070599A
Authority: JP
Inventors: 修二緒方; 良孝菅原
Original assignee: Kansai Electric Power Co Inc
Current assignee: Kansai Electric Power Co Inc
Priority date: 1999-01-05
Filing date: 1999-01-05
Publication date: 2006-08-23
Anticipated expiration: 2019-01-05
Also published as: JP2000199778A

Description

【０００１】
【発明の属する技術分野】
本発明は半導体素子、特に大電力用半導体素子の加速試験方法及びその試験装置に関するものである。
【０００２】
【従来の技術】
大電力用の半導体素子の主要な特性に耐圧がある。半導体素子の一例のサイリスタをオフ状態にして、アノードとカソード間に電圧を印加したとき、リーク電流が流れる。ある一定のリーク電流が流れたときにサイリスタに印加した電圧を耐圧という。一般に耐圧は半導体素子の使用期間が長くなると低下することが知られている。耐圧が低下すると、半導体素子が組み込まれた電気回路又は電子回路の動作に異常をきたすおそれがでてくる。このため、長期間にわたって半導体素子を使用する場合には耐圧の変化が所定の許容範囲にあることを確認するために、信頼性試験を実施している。
【０００３】
大電力用半導体素子の耐圧の従来の試験方法には、直流電圧印加試験と交流電圧印加試験とがある。直流電圧印加試験は、多数の半導体素子に一定の直流電圧を長時間印加して時間に対する、破損した半導体装置の数の分布を調べるものである。交流電圧印加試験は、多数の半導体素子に商用周波数の一定の交流電圧を加えて時間に対する破損した半導体装置の数の分布を調べる。いずれの場合も印加する電圧は、大電力用の半導体素子の定格電圧以下であるが、通常の使用条件よりも厳しい、例えば定格電圧の９０％や８０％などの電圧値である。これにより半導体素子の物理的、化学的な劣化を加速して調べ、使用期間中に耐圧が大幅に変化しないことを確認する。またこれにより半導体素子の使用状態における寿命や故障率を推定することもできる。
【０００４】
【発明が解決しようとする課題】
通常、大電力用の半導体素子は商用周波数で使用されるため、電圧は順方向と逆方向の両方向に交互に印加される。従来の直流電圧印加試験の場合、半導体素子の順方向と逆方向の２回に分けて印加試験を行わなくてはならず、試験時間が長くなる。又、直流電圧印加試験の場合は半導体素子の順方向もしくは逆方向の一方向に印加電圧によるストレスが連続的に与えられるため、ストレスが大きくなりすぎ、別の劣化モードによる破壊が生じるという問題があった。一方従来の交流電圧印加試験は通常の使用条件と同じ商用周波数で試験を行うため、半導体素子に過大なストレスを与えず実レベルのストレスの下で試験ができる。しかし劣化試験をあまり加速することができず、長い試験時間を要するという問題があった。
【０００５】
本発明は半導体素子の耐圧に関する加速試験方法及びその試験装置に関するものであり、半導体素子に上記従来の試験のような過大なストレスを与えることなく適度なストレスの範囲で加速試験を行うことができる試験方法と試験装置を提供することを目的とする。
【０００６】
【課題を解決するための手段】
本発明の半導体素子の加速試験方法は、両極間の電流経路を開閉する半導体素子の加速試験方法であって、半導体素子の使用時に前記半導体素子の電流経路を形成する両極間に印加する交流電圧の周波数より高い周波数であり、オフ状態の前記半導体素子をオンにする、前記両極間の印加電圧の上昇速度で定義される臨界オフ電圧上昇率を、前記半導体素子の定格電圧の４倍の値で除した値で表される周波数よりは低い周波数であって、前記半導体素子の定格電圧より低い値の交流電圧を前記両極間に印加するステップ、及び前記交流電圧が前記両極間に印加されているときに、前記半導体素子の前記両極間を流れるリーク電流を測定するステップを有する。
【０００７】
本発明の半導体素子の加速試験装置は、両極間の電流経路を開閉する半導体素子の加速試験装置であって、半導体素子の使用時に前記半導体素子の電流経路を形成する両極間に印加する交流電圧の周波数より高い周波数であって、オフ状態の前記半導体素子をオンにする、前記両極間の印加電圧の上昇速度で定義される臨界オフ電圧上昇率を、前記半導体素子の定格電圧の４倍の値で除した値で表される周波数より低い周波数であって、前記半導体素子の定格電圧より低い値の交流電圧を前記両極間に印加する交流電源、及び前記交流電圧が前記両極間に印加されているときに、前記半導体素子の前記両極間を流れるリーク電流を測定する電流測定手段を有する。
【０００８】
本発明の加速試験方法及び加速試験装置によれば、半導体素子の両電極間に実使用周波数の商用周波数よりも高い周波数の電圧を印加し、半導体素子に順方向及び逆方向の電圧ストレスを与える。電力用の半導体素子などの、高い温度で使用されるとともに、印加される電圧がきわめて高い半導体素子では、半導体素子に電圧が印加される回数に応じて劣化が進行する。半導体素子の両極間に定格電圧以下で実使用周波数よりも高い周波数の電圧を印加することにより、所定時間内に半導体素子に与えられるストレスの回数が増加し素子の劣化が加速される。
【０００９】
【発明の実施の形態】
この発明の加速試験方法は、半導体素子の両電極間に商用周波数よりも高い周波数の電圧を印加する。印加電圧は定格電圧以下の所定の電圧とし、定格電圧と臨界オフ電圧上昇率とから算出される最大周波数より低く、試験対象素子が実際に使用される周波数の５０Ｈｚ又は６０Ｈｚより高い周波数の電圧を印加して試験を行い、リーク電流を測定して耐圧の変化を推定する。
以下、本発明の好適な実施例を図１から図８を参照して説明する。
【００１０】
《第１実施例》
以下に本発明の第１の実施例の半導体素子の加速試験装置を図１を参照して説明する。図１は、この発明の半導体素子の加速試験装置のブロック図である。
【００１１】
被試験半導体素子として定格電圧８０００Ｖの光サイリスタ素子１を用いる場合について説明する。三相２００Ｖの商用電源３に接続されたコンバータ４によって三相交流を直流に変換する。コンバータ４の２本の出力端はインバータ５の入力端に接続され、商用電源の周波数より高い所定の周波数の交流電圧に変換する。インバータ５の出力端は変圧器２の入力端子２Ａに接続され、交流電圧は変圧器２により昇圧される。変圧器２で所定の電圧に昇圧された交流電圧は、変圧器の両出力電圧２Ｂにそれぞれ接続された光サイリスタ１のアノードとカソードに印加される。両出力端子２Ｂ間には電圧プローブ８が接続され、出力電圧を測定する。出力端子２Ｂの一方とカソードとの接続線１６には電流を検出するＣＴ７がもうけられている。光サイリスタ１の電極には熱電対などの温度センサが取り付けられている。温度センサ６，ＣＴ７，及び電圧プローブ８の検出値を計測用のオシロスコープなどの記録装置９に入力して記録する。記録装置９は内部に時計を有し、アノード電流（リーク電流）の変化を１万ないし２万時間にわたって記録する。光サイリスタ１には、加熱装置１７に接続されたヒータ１８が取り付けられている。加熱装置１７は、温度センサ６の検出値に基づいて光サイリスタ１を所定の温度に保つ。この温度は例えば１２５℃である。
【００１２】
光サイリスタ１が試験により極端に劣化するのを防ぐために印加する交流電圧の最大値は定格電圧の８０％である６４００Ｖにしている。
【００１３】
光サイリスタ１のオフ状態において、アノードとカソード間の順方向電圧を所定の電圧上昇速度、例えば２０００Ｖ／μｓで上昇させると、光サイリスタ１はオンとなる。この電圧の上昇速度を「臨界オフ電圧上昇率」という。光サイリスタ１の臨界オフ電圧上昇率が２０００Ｖ／μｓであるとき、光サイリスタ１がオンにならない印加交流電圧の最大周波数は（２０００×１０^６）／（８０００×４）の演算により求められ、６２５００Ｈｚとなる。本実施例では、定格電圧以下の電圧で、使用周波数よりも高い周波数の電圧を印加することにより試験を加速して行う。加速の倍率は電圧には依存せず、周波数に依存する。最大周波数が６２５００Ｈｚであるので６０Ｈｚの商用周波数と比べて最大１０４１倍の加速が可能となる。５０Ｈｚの場合は１２５０倍の加速が可能となる。本実施例では６２５００Ｈｚより低い周波数である１２００Ｈｚで実験を行って、６０Ｈｚの場合と比較した。６０Ｈｚ、６４００Ｖの交流電圧を１００００時間印加した素子と、１２００Ｈｚ、６４００Ｖの交流電圧を５００時間印加した素子とを比較した結果を図２に示す。図２の横軸は時間を示し、縦軸はリーク電流の測定結果を示す。図２に示すようにリーク電流はほぼ同じであった。
【００１４】
一般に半導体素子を長期間使用したとき耐圧が低下する。耐圧が低下した半導体素子は正常な素子に比べて同じ電圧でより大きなリーク電流が流れる。従ってリーク電流を測定することによって耐圧の変化を推定することができる。図２において、６０Ｈｚ、６４００Ｖの交流電圧を１００００時間印加したものと、１２００Ｈｚ、６４００Ｖの交流電圧を５００時間印加したものとのリーク電流が同じことから、６０Ｈｚでは１００００時間で生じた耐圧の低下が、１２００Ｈｚでは５００時間で生じたことが推定できる。この実験結果から高い周波数の交流電圧を用いることによって耐圧の低下を加速させることができることが確認された。加速による時間短縮は周波数に反比例している。これにより耐圧の変化が周波数を高くすることによって加速できることが確認できた。
【００１５】
《第２実施例》
本発明の第２の実施例の試験装置の構成は実質的に図１に示す第１の実施例のものと同じである。異なる点は、被試験サイリスタのアノードとカソード間に印加する電圧の正負の波高値が互いに異なっていることである。
一般に、インバータ装置などに用いられる大電力用半導体素子に印加される順方向電圧は、逆方向電圧より高い。本実施例はこのような用途の半導体素子に好適である。
【００１６】
図３に、印加する電圧の波形図を示す。図３に示すように、アノード電圧の正の電圧の波高値が負の電圧の波高値よりも高くなされている。このような波形は、図１のインバータ５のパルス幅制御を行うことにより形成することができ印加する電圧の逆方向電圧を順方向電圧より小さくしている。これにより半導体装置の実際に使用される状態に適合するように加速の条件を設定することができる。本実施例でも定格電圧以下で使用周波数よりも高い周波数の電圧を印加することにより試験を加速して行うものである。加速率は電圧には依存せず、周波数に依存するので８０００Ｖの光サイリスタの場合最大１０４１倍（６２５００／６０）まで加速できる。本実施例では、たとえば、印加電圧が同じ場合、６０Ｈｚで１００００時間印加した素子と、１２００Ｈｚで５００時間印加した素子とのリ−ク電流が同じことから、耐圧の変化が周波数を増加させることで加速され、リーク電流を測定することで検出されることが確認できた。
【００１７】
《第３実施例》
次に本発明の第３の実施例の試験装置を図４のブロック図を参照して説明する。被試験半導体素子が定格電圧４５００ＶのＧＴＯサイリスタ（Gate turn off thyrister）の場合について説明する。インバータ５の出力端は単相半波整流回路１０の入力端に接続されている。単相半波整流回路１０の出力端は変圧器２の入力端子２Ａに接続されている。変圧器２の両出力端子２Ｂ間にはＧＴＯサイリスタ１１が接続されている。その他の構成は、図１のものと同じであるので重複する説明は省略する。コンバータ４で商用周波数の３相交流をいったん直流に変換し、インバータ５でこの直流を高周波電圧に変換する。現在のほとんどの高耐圧ＧＴＯサイリスタは逆阻止耐圧が極めて低い逆導電形である。従って高い逆方向電圧を印加するとＧＴＯサイリスタ１１が破損するおそれがある。本実施例では、単相半波整流回路１０で高周波電圧を半波整流して半波の出力電圧を得る。半波の出力電圧を変圧器２で昇圧して順方向の最大電圧が定格電圧の８０％で、逆方向電圧が実質的に零の電圧を生成しＧＴＯサイリスタ１１に印加する。
【００１８】
印加する電圧の最大値は定格電圧の８０％である３６００Ｖである。このＧＴＯサイリスタ１１の臨界オフ電圧上昇率は６００Ｖ／μｓであるので、印加交流電圧の最大周波数は３３３３３Ｈｚとなる（６００×１０^６／４５００×４）。従って６０Ｈｚの商用周波数に比べて最大５５６倍の加速試験が可能となる。本実施例では６０Ｈｚと１２００Ｈｚの交流電圧を用いて実験を行った。６０Ｈｚ、３６００Ｖの電圧を１００００時間印加した素子と、１２００Ｈｚ、３６００Ｖの電圧を５００時間印加した素子とのリーク電流が同じであった。測定結果を図５に示す。これにより耐圧の変化が周波数を増加することで加速され、変化した耐圧をリーク電流の測定で知ることができることが確認できた。
【００１９】
《第４実施例》
次に本発明の第４の実施例の試験装置を図６のブロック図を参照して説明する。図６に示す試験装置では定格電圧２０００Ｖのサイリスタ１４を測定対象としている。３相の商用電源３にコンバータ４が接続され、三相交流をいったん直流に変換する。コンバータ４の出力端に、２個のインバータ１２とインバータ１３が並列に接続され、直流電圧を高周波電圧に変換する。インバータ１２とインバータ１３とは変換周波数が互に異なるように構成されているので、変圧器２の入力端子２Ａに振幅変調された高周波電圧を出力することができる。このような電圧条件で使用する用途としては大出力ラジオ放送装置などに用いる半導体素子がある。例えばインバータ１２から出力される高周波電圧を式、Ａｃｏｓ（ωｔ＋θ）で表される波形とし、インバータ１３から出力される高周波電圧を式、Ａｃｏｓｐｔで表される波形とする。両者を合成すると合成された高周波電圧は式、Ａ（１＋ｋｃｏｓｐｔ）ｃｏｓ（ωｔ＋θ）で表される波形となる。図７に示すアノード電圧の波形図は、上記の各式において、Ａ＝１、ｋ＝１、ｐ＝１、ω＝１０、θ＝πとした場合を示す。
【００２０】
図６において、サイリスタ１４のアノードとカソード間に印加する電圧の最大値は定格電圧の８０％である１６００Ｖである。このサイリスタ１４の臨界オフ電圧上昇率は３００Ｖ／μｓであるので、印加交流電圧の最大周波数は３７５００Ｈｚとなる（３００×１０^６／２０００×４）。従って６０Ｈｚの商用周波数に比べて最大６２５倍の加速試験が可能となる。
【００２１】
本実施例によれば、大出力ラジオ放送に用いられる、高い振幅変調電圧が印加される大電力用半導体素子に関しても、半導体素子の極端な劣化を招くことなく、最大６２５倍までの加速試験ができる。搬送周波数６０Ｈｚ、１６００Ｖの電圧を１００００時間印加した素子と、搬送周波数１２０００Ｈｚ、１６００Ｖの電圧を５０時間印加した素子とのリーク電流が同じであった。測定結果を図８に示す。これにより耐圧の変化が周波数を増加させることで加速され、リーク電流を測定することで検出されることが確認できた。
【００２２】
以上のように、本実施例の試験装置では、半導体素子の定格電圧と臨界オフ電圧上昇率から算出される最大周波数より低く、かつ試験対象素子が実際に使用される周波数の５０Ｈｚ又は６０Ｈｚより大きな周波数の電圧を印加して試験を行なうことにより半導体素子の劣化を加速して短時間で耐圧の変化を知ることができる。これに基づいて半導体素子の使用状態における寿命や故障率を推定することができる。
【００２３】
この発明の実施の態様は以上の実施例に限定されるものではなく、細部については様々な変形が可能である。例えば半導体素子に流れる電流を測定して記録する手段としては、オシロスコープやＣＴに限るものではなく、回路に抵抗を挿入して抵抗に生じる電圧に基づいて測定してもよい。またコンバータでいったん商用電圧を直流電圧に変換してから、インバータで直流電圧を高周波電圧に変換しているが、サイクロコンバータで直接商用電源の２００Ｖから電圧を高周波電圧に変換してもよい。
さらにこの発明は、サイリスタ、ＧＴＯサイリスタだけではなくダイオード、トランジスタ、ＩＧＢＴ、ＳＩトランジスタ、ＳＩサイリスタ、ＭＯＳＦＥＴなどの各種半導体素子や、複数の半導体素子を含むハイブリッドＩＣあるいは複数の半導体素子が組み合わされたモジュールなどにも適用できる。
【００２４】
【発明の効果】
以上の実施例の説明から明らかなように、本発明によれば、半導体素子の定格として定められた定格電圧と臨界オフ電圧上昇率から算出される最大周波数以下でかつ試験対象素子が実際に使用される周波数の５０Ｈｚ又は６０Ｈｚより大きな周波数の電圧を印加して試験を行う。これにより、使用条件と大幅に異なる劣化を招くことなく半導体素子の劣化要因を加速して、耐圧の変化を短時間で確認できるとともに、半導体素子の使用状態における寿命や故障率を推定することができ、試験に要する期間を低減することができる。
【図面の簡単な説明】
【図１】この発明の第１の実施例である半導体素子の試験装置のブロック図
【図２】第１の実施例における６０Ｈｚと１２００Ｈｚでのリーク電流と試験時間との関係を示すグラフ
【図３】第２の実施例におけるアノード電圧の波形図
【図４】この発明の第３の実施例である半導体素子の試験装置のブロック図
【図５】第３の実施例における６０Ｈｚと１２００Ｈｚでのリーク電流と試験時間との関係を示すグラフ
【図６】この発明の第４の実施例である半導体素子の試験装置のブロック図
【図７】第４の実施例におけるアノード電圧の波形図
【図８】第４の実施例における６０Ｈｚと１２０００Ｈｚでのリーク電流と試験時間との関係を示すグラフ
【符号の説明】
１光サイリスタ
２変圧器
３商用電源
４コンバータ
５インバータ
６温度センサ
７ＣＴ
８電圧プローブ
９オシロスコープ
１０記録装置
１１ＧＴＯサイリスタ
１２インバータ
１３インバータ
１４サイリスタ
１６接続線
１７加熱装置
１８ヒーター[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an acceleration test method and a test apparatus for a semiconductor element, particularly a high power semiconductor element.
[0002]
[Prior art]
The main characteristic of high-power semiconductor devices is withstand voltage. When a thyristor as an example of a semiconductor element is turned off and a voltage is applied between the anode and the cathode, a leak current flows. The voltage applied to the thyristor when a certain leak current flows is called withstand voltage. In general, it is known that the breakdown voltage decreases as the period of use of a semiconductor element increases. When the withstand voltage is lowered, there is a risk that the operation of the electric circuit or electronic circuit in which the semiconductor element is incorporated becomes abnormal. For this reason, when a semiconductor element is used for a long period of time, a reliability test is performed in order to confirm that the change in breakdown voltage is within a predetermined allowable range.
[0003]
Conventional test methods for the breakdown voltage of high-power semiconductor devices include a DC voltage application test and an AC voltage application test. In the DC voltage application test, a constant DC voltage is applied to a large number of semiconductor elements for a long time to examine the distribution of the number of damaged semiconductor devices with respect to time. In the AC voltage application test, a constant AC voltage having a commercial frequency is applied to a large number of semiconductor elements to examine the distribution of the number of damaged semiconductor devices with respect to time. In any case, the voltage to be applied is equal to or lower than the rated voltage of the semiconductor element for high power, but is a voltage value that is stricter than normal use conditions, for example, 90% or 80% of the rated voltage. This accelerates and examines physical and chemical degradation of the semiconductor element, and confirms that the withstand voltage does not change significantly during the period of use. This also makes it possible to estimate the lifetime and failure rate of the semiconductor element in use.
[0004]
[Problems to be solved by the invention]
Usually, since a semiconductor element for high power is used at a commercial frequency, a voltage is applied alternately in both the forward and reverse directions. In the case of a conventional DC voltage application test, the application test must be performed in two steps, the forward direction and the reverse direction of the semiconductor element, and the test time becomes longer. In addition, in the case of a DC voltage application test, the stress due to the applied voltage is continuously applied in one direction of the semiconductor element in the forward direction or the reverse direction, so that the stress becomes too large and the breakdown due to another deterioration mode occurs. there were. On the other hand, since the conventional AC voltage application test is performed at the same commercial frequency as that under normal use conditions, the test can be performed under actual level stress without applying excessive stress to the semiconductor element. However, there is a problem that the deterioration test cannot be accelerated so much and a long test time is required.
[0005]
The present invention relates to an acceleration test method and a test apparatus for a breakdown voltage of a semiconductor element, and can perform an acceleration test in an appropriate stress range without applying excessive stress to the semiconductor element as in the conventional test. An object is to provide a test method and a test apparatus.
[0006]
[Means for Solving the Problems]
The semiconductor element acceleration test method of the present invention is a semiconductor element acceleration test method for opening and closing a current path between two electrodes, and an AC voltage applied between the two electrodes forming the current path of the semiconductor element when the semiconductor element is used. A critical off-voltage rise rate defined by the rate of rise of the applied voltage between the two electrodes that turns on the off-state semiconductor element is a value that is four times the rated voltage of the semiconductor element. A step of applying an alternating voltage between the two electrodes, the frequency being lower than the frequency represented by the value divided by the lower value than the rated voltage of the semiconductor element, and the alternating voltage being applied between the two electrodes. A leakage current flowing between the two electrodes of the semiconductor element is measured.
[0007]
A semiconductor element acceleration test apparatus according to the present invention is a semiconductor element acceleration test apparatus that opens and closes a current path between two electrodes, and an AC voltage applied between the two electrodes that form the current path of the semiconductor element when the semiconductor element is used. The critical off-voltage rise rate defined by the rate of rise of the applied voltage between the two electrodes that turns on the off-state semiconductor element is four times the rated voltage of the semiconductor element. An alternating current power source for applying an alternating voltage between the two electrodes, which is a frequency lower than the frequency represented by the value divided by the value and lower than the rated voltage of the semiconductor element, and the alternating voltage is applied between the two electrodes. Current measuring means for measuring a leakage current flowing between the two electrodes of the semiconductor element .
[0008]
According to the acceleration test method and the acceleration test apparatus of the present invention, a voltage having a frequency higher than the commercial frequency of the actual use frequency is applied between both electrodes of the semiconductor element, thereby applying forward and reverse voltage stress to the semiconductor element. . In a semiconductor element that is used at a high temperature and has a very high voltage applied, such as a power semiconductor element, the deterioration proceeds according to the number of times the voltage is applied to the semiconductor element. By applying a voltage having a frequency lower than the rated voltage and higher than the actual use frequency between both electrodes of the semiconductor element, the number of stresses applied to the semiconductor element within a predetermined time is increased, and the deterioration of the element is accelerated.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
In the accelerated test method of the present invention, a voltage having a frequency higher than the commercial frequency is applied between both electrodes of the semiconductor element. The applied voltage is a predetermined voltage equal to or lower than the rated voltage, and a voltage having a frequency lower than the maximum frequency calculated from the rated voltage and the critical off-voltage rise rate and a frequency higher than 50 Hz or 60 Hz, which is the frequency at which the test target element is actually used. A test is performed by applying voltage, and a leakage current is measured to estimate a change in breakdown voltage.
A preferred embodiment of the present invention will be described below with reference to FIGS.
[0010]
<< First Example >>
A semiconductor device acceleration test apparatus according to a first embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a block diagram of a semiconductor device acceleration test apparatus according to the present invention.
[0011]
The case where the optical thyristor element 1 having a rated voltage of 8000 V is used as the semiconductor element to be tested will be described. The converter 4 connected to the three-phase 200V commercial power supply 3 converts the three-phase alternating current into direct current. The two output terminals of the converter 4 are connected to the input terminal of the inverter 5 and convert it into an AC voltage having a predetermined frequency higher than the frequency of the commercial power supply. The output terminal of the inverter 5 is connected to the input terminal 2 </ b> A of the transformer 2, and the AC voltage is boosted by the transformer 2. The AC voltage boosted to a predetermined voltage by the transformer 2 is applied to the anode and cathode of the optical thyristor 1 connected to both output voltages 2B of the transformer. A voltage probe 8 is connected between the output terminals 2B to measure the output voltage. A connection line 16 between one of the output terminals 2B and the cathode is provided with CT7 for detecting current. A temperature sensor such as a thermocouple is attached to the electrode of the optical thyristor 1. The detection values of the temperature sensors 6, CT7 and voltage probe 8 are input to a recording device 9 such as an oscilloscope for measurement and recorded. The recording device 9 has a clock inside, and records changes in anode current (leakage current) over 10,000 to 20,000 hours. A heater 18 connected to the heating device 17 is attached to the optical thyristor 1. The heating device 17 keeps the optical thyristor 1 at a predetermined temperature based on the detection value of the temperature sensor 6. This temperature is, for example, 125 ° C.
[0012]
In order to prevent the optical thyristor 1 from being extremely deteriorated by the test, the maximum value of the alternating voltage applied is set to 6400 V which is 80% of the rated voltage.
[0013]
When the forward voltage between the anode and the cathode is increased at a predetermined voltage increase rate, for example, 2000 V / μs in the off state of the optical thyristor 1, the optical thyristor 1 is turned on. This rate of voltage increase is referred to as “critical off-voltage increase rate”. When the critical off voltage increase rate of the optical thyristor 1 is 2000 V / μs, the maximum frequency of the applied AC voltage at which the optical thyristor 1 does not turn on is obtained by the calculation of (2000 × 10 ⁶ ) / (8000 × 4), and is 62500 Hz. It becomes. In the present embodiment, the test is accelerated by applying a voltage not higher than the rated voltage and a frequency higher than the operating frequency. The acceleration factor does not depend on the voltage, but on the frequency. Since the maximum frequency is 62500 Hz, acceleration of up to 1041 times is possible compared with the commercial frequency of 60 Hz. In the case of 50 Hz, acceleration of 1250 times is possible. In this example, the experiment was performed at 1200 Hz, which is a frequency lower than 62500 Hz, and compared with the case of 60 Hz. FIG. 2 shows a result of comparison between an element to which an AC voltage of 60 Hz and 6400 V was applied for 10,000 hours and an element to which an AC voltage of 1200 Hz and 6400 V was applied for 500 hours. The horizontal axis of FIG. 2 indicates time, and the vertical axis indicates the measurement result of leakage current. As shown in FIG. 2, the leakage current was almost the same.
[0014]
Generally, the breakdown voltage decreases when a semiconductor element is used for a long time. A semiconductor element having a reduced breakdown voltage flows a larger leak current at the same voltage than a normal element. Therefore, the change in breakdown voltage can be estimated by measuring the leakage current. In FIG. 2, since the leak current is the same when the alternating voltage of 60 Hz and 6400 V is applied for 10,000 hours and when the alternating voltage of 1200 Hz and 6400 V is applied for 500 hours, the decrease in breakdown voltage that occurred in 10,000 hours at 60 Hz is observed. It can be estimated that it occurred in 500 hours at 1200 Hz. From this experimental result, it was confirmed that the decrease in breakdown voltage can be accelerated by using an AC voltage having a high frequency. Time reduction due to acceleration is inversely proportional to frequency. Thus, it was confirmed that the change in breakdown voltage can be accelerated by increasing the frequency.
[0015]
<< Second Embodiment >>
The configuration of the test apparatus of the second embodiment of the present invention is substantially the same as that of the first embodiment shown in FIG. The difference is that the peak values of the voltages applied between the anode and cathode of the thyristor under test are different from each other.
Generally, a forward voltage applied to a high power semiconductor element used in an inverter device or the like is higher than a reverse voltage. This embodiment is suitable for a semiconductor device for such a use.
[0016]
FIG. 3 shows a waveform diagram of the applied voltage. As shown in FIG. 3, the peak value of the positive voltage of the anode voltage is higher than the peak value of the negative voltage. Such a waveform can be formed by controlling the pulse width of the inverter 5 shown in FIG. 1, and the reverse voltage of the applied voltage is made smaller than the forward voltage. As a result, the acceleration condition can be set so as to match the state in which the semiconductor device is actually used. In this embodiment, the test is accelerated by applying a voltage lower than the rated voltage and higher than the operating frequency. Since the acceleration rate does not depend on the voltage but depends on the frequency, in the case of an optical thyristor of 8000 V, the acceleration can be increased up to 1041 times (62500/60). In this embodiment, for example, when the applied voltage is the same, the leak current of the element applied for 10000 hours at 60 Hz and the element applied for 500 hours at 1200 Hz are the same, so the change in breakdown voltage increases the frequency. It was confirmed that it was accelerated and detected by measuring the leakage current.
[0017]
<< Third embodiment >>
Next, a test apparatus according to a third embodiment of the present invention will be described with reference to the block diagram of FIG. The case where the semiconductor device under test is a GTO thyristor (Gate turn off thyrister) with a rated voltage of 4500 V will be described. The output terminal of the inverter 5 is connected to the input terminal of the single-phase half-wave rectifier circuit 10. The output terminal of the single-phase half-wave rectifier circuit 10 is connected to the input terminal 2 </ b> A of the transformer 2. A GTO thyristor 11 is connected between both output terminals 2B of the transformer 2. Other configurations are the same as those in FIG. The converter 4 once converts the commercial frequency three-phase alternating current into direct current, and the inverter 5 converts the direct current into a high frequency voltage. Most current high breakdown voltage GTO thyristors are of the reverse conductivity type with extremely low reverse blocking breakdown voltage. Therefore, if a high reverse voltage is applied, the GTO thyristor 11 may be damaged. In this embodiment, the single-phase half-wave rectifier circuit 10 half-wave rectifies the high-frequency voltage to obtain a half-wave output voltage. The half-wave output voltage is boosted by the transformer 2 to generate a voltage whose maximum forward voltage is 80% of the rated voltage and whose reverse voltage is substantially zero, and is applied to the GTO thyristor 11.
[0018]
The maximum value of the applied voltage is 3600 V, which is 80% of the rated voltage. Since the critical rate of rise of off-state voltage of the GTO thyristor 11 is a 600V / .mu.s, the maximum frequency of the applied AC voltage is ^{33333Hz (600 × 10 6/4500} × 4). Therefore, an acceleration test of up to 556 times is possible compared with a commercial frequency of 60 Hz. In this example, the experiment was performed using 60 Hz and 1200 Hz AC voltage. The leakage current was the same between the element applied with a voltage of 60 Hz and 3600 V for 10,000 hours and the element applied with a voltage of 1200 Hz and 3600 V for 500 hours. The measurement results are shown in FIG. As a result, it was confirmed that the change in the breakdown voltage was accelerated by increasing the frequency, and the changed breakdown voltage could be known by measuring the leakage current.
[0019]
<< 4th Example >>
Next, a test apparatus according to a fourth embodiment of the present invention will be described with reference to the block diagram of FIG. In the test apparatus shown in FIG. 6, the thyristor 14 having a rated voltage of 2000 V is the measurement target. A converter 4 is connected to the three-phase commercial power source 3 to convert the three-phase alternating current into direct current. Two inverters 12 and 13 are connected in parallel to the output terminal of the converter 4 to convert a DC voltage into a high-frequency voltage. Since the inverter 12 and the inverter 13 are configured to have different conversion frequencies, an amplitude-modulated high-frequency voltage can be output to the input terminal 2 </ b> A of the transformer 2. As an application to be used under such a voltage condition, there is a semiconductor element used for a high-power radio broadcast apparatus or the like. For example, the high-frequency voltage output from the inverter 12 is an expression, a waveform represented by Acos (ωt + θ), and the high-frequency voltage output from the inverter 13 is an expression, a waveform represented by Acostt. When both are combined, the combined high-frequency voltage has a waveform represented by the expression A (1 + kcostt) cos (ωt + θ). The waveform diagram of the anode voltage shown in FIG. 7 shows a case where A = 1, k = 1, p = 1, ω = 10, and θ = π in each of the above equations.
[0020]
In FIG. 6, the maximum value of the voltage applied between the anode and the cathode of the thyristor 14 is 1600 V, which is 80% of the rated voltage. Since the critical rate of rise of off-state voltage of the thyristor 14 is a 300 V / .mu.s, the maximum frequency of the applied AC voltage is ^{37500Hz (300 × 10 6/2000} × 4). Therefore, an acceleration test of up to 625 times is possible compared with a commercial frequency of 60 Hz.
[0021]
According to this embodiment, even for a high-power semiconductor device to which a high amplitude modulation voltage is applied, which is used for high-power radio broadcasting, an acceleration test up to 625 times can be performed without causing extreme deterioration of the semiconductor device. it can. The leak current was the same between the element to which the voltage of carrier frequency 60 Hz and 1600 V was applied for 10,000 hours and the element to which the voltage of carrier frequency 12000 Hz and 1600 V was applied for 50 hours. The measurement results are shown in FIG. As a result, it was confirmed that the change in breakdown voltage was accelerated by increasing the frequency and detected by measuring the leakage current.
[0022]
As described above, in the test apparatus of this example, the frequency is lower than the maximum frequency calculated from the rated voltage of the semiconductor element and the critical off-voltage increase rate, and is higher than 50 Hz or 60 Hz, which is the frequency at which the test target element is actually used. By performing a test by applying a voltage of a frequency, the deterioration of the semiconductor element can be accelerated and the change in the breakdown voltage can be known in a short time. Based on this, it is possible to estimate the lifetime and failure rate of the semiconductor element in use.
[0023]
The embodiment of the present invention is not limited to the above embodiments, and various modifications can be made to the details. For example, the means for measuring and recording the current flowing through the semiconductor element is not limited to an oscilloscope or CT, but may be measured based on a voltage generated in the resistance by inserting a resistance in the circuit. Further, the commercial voltage is once converted into a DC voltage by the converter, and then the DC voltage is converted into a high-frequency voltage by the inverter. However, the voltage may be directly converted from a commercial power supply of 200 V to a high-frequency voltage by a cycloconverter.
Furthermore, the present invention is not limited to thyristors and GTO thyristors, but also includes various semiconductor elements such as diodes, transistors, IGBTs, SI transistors, SI thyristors, MOSFETs, hybrid ICs including a plurality of semiconductor elements, or a module in which a plurality of semiconductor elements are combined. It can also be applied.
[0024]
【The invention's effect】
As is clear from the above description of the embodiments, according to the present invention, the device under test is actually used at a frequency lower than the maximum frequency calculated from the rated voltage defined as the rating of the semiconductor device and the critical off-voltage rise rate. The test is performed by applying a voltage having a frequency higher than 50 Hz or 60 Hz. As a result, the deterioration factor of the semiconductor element can be accelerated without causing deterioration significantly different from the use condition, and the change of the breakdown voltage can be confirmed in a short time, and the lifetime and failure rate in the use state of the semiconductor element can be estimated. And the time required for the test can be reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram of a semiconductor device test apparatus according to a first embodiment of the present invention. FIG. 2 is a graph showing a relationship between a leak current at 60 Hz and 1200 Hz and a test time in the first embodiment. 3] Waveform diagram of anode voltage in the second embodiment. [FIG. 4] Block diagram of a semiconductor device testing apparatus according to the third embodiment of the present invention. [FIG. 5] At 60 Hz and 1200 Hz in the third embodiment. FIG. 6 is a block diagram of a semiconductor device testing apparatus according to a fourth embodiment of the present invention. FIG. 7 is a waveform diagram of an anode voltage in the fourth embodiment. 8] A graph showing the relationship between the leakage current at 60 Hz and 12000 Hz and the test time in the fourth embodiment.
1 Optical Thyristor 2 Transformer 3 Commercial Power Supply 4 Converter 5 Inverter 6 Temperature Sensor 7 CT
8 Voltage probe 9 Oscilloscope 10 Recording device 11 GTO thyristor 12 Inverter 13 Inverter 14 Thyristor 16 Connection line 17 Heating device 18 Heater

Claims

A method for accelerating a semiconductor element that opens and closes a current path between two electrodes,
The rising speed of the said when using the semiconductor device is a frequency higher than the frequency of the AC voltage applied between the electrodes to form the current path of the semiconductor device, to turn on the semiconductor device in the OFF state, the voltage applied between the two electrodes Is a frequency lower than the frequency represented by a value obtained by dividing the critical off voltage increase rate defined by the value by four times the rated voltage of the semiconductor element, and is lower than the rated voltage of the semiconductor element. Applying an alternating voltage between the electrodes;
as well as
A method for accelerating a semiconductor device, comprising: measuring a leakage current flowing between the electrodes of the semiconductor device when the AC voltage is applied between the electrodes .

The accelerated test method for a semiconductor device according to claim 1, further comprising a step of obtaining a withstand voltage with respect to the measured leak current from a relationship between a leak current and a withstand voltage obtained in advance for the semiconductor element.

2. The accelerated test method for a semiconductor device according to claim 1, wherein a forward voltage of an alternating voltage applied between both electrodes of the semiconductor device is higher than a reverse voltage.

2. The accelerated test method for a semiconductor device according to claim 1, wherein the reverse voltage of the AC voltage applied between both electrodes of the semiconductor device is substantially zero.

2. The acceleration test method for a semiconductor device according to claim 1, wherein the alternating voltage applied between both electrodes of the semiconductor device is amplitude-modulated.

The method of claim 1, wherein the semiconductor element is heated to a predetermined temperature.

A semiconductor device acceleration test apparatus that opens and closes a current path between two electrodes,
The rising speed of the said when using the semiconductor device is a frequency higher than the frequency of the AC voltage applied between the electrodes to form the current path of the semiconductor device, to turn on the semiconductor device in the OFF state, the voltage applied between the two electrodes An alternating current having a frequency lower than a frequency represented by a value obtained by dividing the critical off-voltage increase rate defined by (4) by a value four times the rated voltage of the semiconductor element and lower than the rated voltage of the semiconductor element. AC power supply for applying a voltage between the two electrodes,
as well as
An acceleration test apparatus for a semiconductor device, comprising current measuring means for measuring a leakage current flowing between the electrodes of the semiconductor element when the AC voltage is applied between the electrodes .

8. The acceleration test apparatus for a semiconductor device according to claim 7 , wherein the AC voltage applied between both electrodes of the semiconductor device of the AC power source has a forward voltage higher than a reverse voltage.

8. The acceleration test apparatus for a semiconductor device according to claim 7 , wherein a reverse voltage of the AC voltage applied between both electrodes of the semiconductor device of the AC power supply is substantially zero.

8. The acceleration test apparatus for a semiconductor device according to claim 7 , wherein the AC voltage applied between both electrodes of the semiconductor device of the AC power supply is amplitude-modulated.

8. The acceleration test apparatus for a semiconductor element according to claim 7, further comprising a heating unit that heats the semiconductor element to a predetermined temperature.