Reliability problems in TTL-LS devices

Abstract An analysis of the possible failure modes of TTL-LS was carried out, with particular emphasis on long term thermal stability of Schottky diodes, all realized by PtSi - Ti/W - Al metallization system. Only from one supplier were there diodes in which changes in the characteristics, due to metallization defects, were observed during accelerated thermal cycles. On the contrary, once its uniformity is guaranteed, the Ti/W barrier layer inhibits the Si-Al interdiffusion up to 550 °C, 1 hr thermal annealing. Sensitivity to negative input pulses and electrical overstresses were also investigated. Scanning electron microscope and microprobe, and voltage contrast techniques seem to be more suitable instruments to investigate the reliability of such devices than the conventional life tests. The technology employed today seems provide suitable reliability for TTL Low-Power Schottky devices.