CHARACTERISTICS OF FAST SURFACE STATES ASSOCIATED WITH SIO2-SI AND SI3N4-SIO2-SI STRUCTURES

Characteristics of fast surface states located at the SiO2-Si interface of thermally oxidized silicon structures (MOS) and structures incorporating vapor-deposited silicon nitride films over thermally oxidized silicon (MNOS) have been investigated. Effects of oxidation and annealing conditions on the formation or reduction of fast surface states, using MOS capacitance-voltage curves, are first discussed. The effects of silicon nitride layers over thermal oxides on the electrical properties of MNOS structures are next presented, with emphasis being placed on the ability of the nitride to prevent or mask the annihilation of fast states which normally occurs during an anneal in dry N2 at 500°-565°C for 2-5 min after aluminum deposition. Such variables as deposition ambient, flow rate, high temperature anneals, nitride structure, and reactant type are shown to affect the masking ability of the nitride. These results, along with special experiments, help to confirm the postulate that some active species of hydrogen plays an important part in the elimination of fast surface states in MOS and MNOS structures. © 1969, The Electrochemical Society, Inc. All rights reserved.