Effect of mechanical stress on reliability of gate-oxide film in MOS transistors

The effect of mechanical stress on the initial and time-dependent dielectric breakdown characteristics of gate-oxide films in MOS transistors was measured by changing the stress field in both silicon substrates and in the thin films used for the gate electrodes. The initial breakdown failure rate decreases monotonically as internal stress in the gate electrodes is reduced. On the other hand, there is a critical stress beyond which the average lifetime of time-dependent breakdown failure decreases to less than a tenth.