Thin film FET prodn. using tantalum pent:oxide as gate oxide - by anodic oxidn. of doped tantalum gate electrode giving high transconductance

In the prodn. of thin film FETs, Ta2O5 is used as gate oxide. This is produced by anodic oxidn. of the gate electrode of doped Ta produced by photolithography and etching before application of the semiconductor film. The high dielectric constant of Ta2O5 compared with Al2 O3 or Y2O3 leads to high charge carrier inductor in the semiconductor channel and hence to a higher transconductance of the transistor. Also, the dielectric is stable for over 2 h at over 300 degrees C, which is decisive in mfr. The individual process stages can be optimised, since intermediate tests are possible. Used in mfr. by photolithography and etching, the surface is cleaned, before application of the semiconductor, in the same vacuum stage by etching with ions or uncharged particles. Very small channel lengths can be formed by the thickness of the semiconductor film.