Main technological causes and some mechanisms of high power GTO´s failures

The necessity to compare the manufacturing qualities and their evolution on the electrical performances and reliability point of view requires these device valuations. The main neatness and manufacturing defects which can cause GTO thyristor failures or at least their electrical performance deterioration are described and discussed. Neatness defects generally encountered are due to the presence of metallic impurities which could lead to gate cathode short-circuits whereas manufacturing defects are linked to the fineness and care of device realization. The performance improvement of high power GTOs requires more and more technologies and realization care near the microelectronics ones. Some design choices are discussed as regards their corresponding electrical performances. Finally GTO failures observed at the INRETS laboratory are discussed on the basis of the experimental measurements