Effect of stress interruption and pulsed biased stress on ultra-thin gate dielectric reliability

We studied the effects of stress interruption on the time-dependent dielectric breakdown (TDDB) life distributions of 2.0 nm oxynitride gate dielectric films. TDDB tests using two different breakdown detection techniques were conducted at several gate voltages. Additional tests were conducted using unipolar and bipolar pulsed bias with pulse repetition frequencies up to 100 kHz to study the effects of pulsed bias on the lifetime of 2 nm films. Our results show that (1) stress interruption longer than 1 s does not affect the defect generation and TDDB life distributions, (2) both current noise and the increase in low-voltage stress induced leakage current (SILC) detection techniques provide similar failure statistics for ultra-thin SiO₂, and (3) TDDB lifetime for ultra-thin gate dielectrics under unipolar biased stress does not substantially depend on pulse repetition frequencies less than 1 MHz, (4) however, we also report that TDDB lifetime for ultra-thin gate dielectrics under bipolar biased stress exhibits a frequency dependence.