COMPARISON OF AL SIN/A-SI-H AND AL/SIO2/A-SI-H TOP GATE STRUCTURES UNDER THERMAL BIAS STRESSES/

Two kinds of insulators, PECVD silicon nitride (SiN) and DECR silicon dioxide (SiO2), are compared using top gate metal/insulator/semiconduc tor structures based on amorphous silicon (a-Si:H). The comparison is based on quasistatic capacitance measurements following several therma l bias annealing steps at different bias-anneal voltages V-ba. For pos itive bias annealing, both Al/SiN/a-Si:H and Al/SiO2/a-Si:H structures show similar behaviour with increasing V-ba, indicating changes in th e a-Si:H bulk defect density. For negative bias annealing, the two kin ds of structures behave differently owing to their different interface s. Experimental results indicate the presence of a bump in the interfa ce trap level density at the SiN/a-Si:H interface, which is not observ ed at the SiO2/a-Si:H interface. (C) 1997 Elsevier Science S.A.