Recent issues in negative-bias temperature instability: Initial degradation, field dependence of interface trap generation, hole trapping effects, and relaxation

Abstract

Recent advances in experimental techniques (on-the-fly and ultrafast techniques) allow measurement of threshold voltage degradation due to negative-bias temperature instability (NBTI) over many decades in timescale. Such measurements over wider temperature range (-25 degrees C to 145 degrees C, film thicknesses (1.2-2.2 nm of effective oxide thickness), and processing conditions (variation of nitrogen within gate dielectric) provide an excellent framework for a theoretical analysis of NBTI degradation. In this paper, we analyze these experiments to refine the existing theory of NBTI to 1) explore the mechanics of time transients of NBTI over many orders of magnitude in time; 2) establish field dependence of interface trap generation to resolve questions regarding the appropriateness of power law versus exponential projection of lifetimes; 3) ascertain the relative contributions to NBTI from interface traps versus hole trapping as a function of processing conditions; and 4) briefly discuss relaxation dynamics for fast-transient NBTI recovery that involves interface traps and trapped holes.