Negative bias temperature instability mechanism: The role of molecular hydrogen

Abstract

The role of dimerization of atomic hydrogen to give molecular hydrogen in determining negative bias temperature instability (NBTI) kinetics is explored analytically. The time dependency of NBTI involving molecular hydrogen was found to obey a power law with a slope of 1∕6, as opposed to the 1∕4 slope derived for a reaction involving atomic hydrogen. The implications of this dimerization reaction for voltage and temperature acceleration are also discussed. Simulation results validating these predictions are also described. The higher slopes typically reported for NBTI are shown to be an artifact of measurement, and experimental data supporting this lower time dependency is shown.

Critical analysis of short-term negative bias temperature instability measurements: Explaining the effect of time-zero delay for on-the-fly measurements

“…The R-D model attributes the robust ͑constant over several decades in time 4 ͒ long-term n ϳ 1 / 6 exponent to the diffusion of molecular hydrogen ͑H 2 ͒. 3,7 This "H 2 R-D" model also provides a consistent interpretation of temperature and field dependencies of NBTI for long-term stress, as extensively studied for devices with SiO 2 , plasma SiON, and thin thermal SiON dielectrics. 2,5,6,8 Although the classical "H 2 R-D" model provides an excellent interpretation for long-term stress data, our analysis shows that ͑1͒ the predictions of this model is inconsistent with the short term, sub-10 s, NBTI degradation ͓see Fig.…”

“…This requires explicit consideration of H within the R-D framework, as this should be the first by-product after interface trap generation, before getting transformed to H 2 . 3,7 Although neutral charge state may not be a stable form of atomic hydrogen, its transient formation is indeed possible. 10 Therefore, in the generalized R-D model, diffusion of both H and H 2 and H ↔ H 2 conversion are explicitly incorporated in the R-D framework by the following equations: 11 Our simulation results, based on the solution of Eqs.…”

“…[1][2][3][4][5][6][7] At long stress time ͑t stress Ͼ 10-100 s͒, ⌬V T shows a power law behavior when plotted with respect to time ͑⌬V T ϳ At n ͒ with a consistent time exponent ͑n͒ of ϳ1 / 6. This time exponent is independent of the measurement techniques used to monitor ⌬V T ͓e.g., ultrafast measurement ͑UFM͒, 9 "delay-free" on-the-fly I dlin measurement ͑OTFM͒, 2,3,5,6,8 etc.͔. The R-D model attributes the robust ͑constant over several decades in time 4 ͒ long-term n ϳ 1 / 6 exponent to the diffusion of molecular hydrogen ͑H 2 ͒.…”

“…The origin of such degradation has been debated for the last few years, and it is now generally accepted that, for devices with SiO 2 , plasma SiON, and thin thermal SiON gate dielectrics, NBTI degradation results mainly from depassivation of Si-H bonds at the Si/dielectric interface and resultant diffusion of hydrogen species into gate dielectric and poly-Si. [1][2][3][4][5][6][7][8] As such, several groups have used the reaction-diffusion ͑R-D͒ model to interpret NBTI degradation. [1][2][3][4][5][6][7] At long stress time ͑t stress Ͼ 10-100 s͒, ⌬V T shows a power law behavior when plotted with respect to time ͑⌬V T ϳ At n ͒ with a consistent time exponent ͑n͒ of ϳ1 / 6.…”

“…[1][2][3][4][5][6][7][8] As such, several groups have used the reaction-diffusion ͑R-D͒ model to interpret NBTI degradation. [1][2][3][4][5][6][7] At long stress time ͑t stress Ͼ 10-100 s͒, ⌬V T shows a power law behavior when plotted with respect to time ͑⌬V T ϳ At n ͒ with a consistent time exponent ͑n͒ of ϳ1 / 6. This time exponent is independent of the measurement techniques used to monitor ⌬V T ͓e.g., ultrafast measurement ͑UFM͒, 9 "delay-free" on-the-fly I dlin measurement ͑OTFM͒, 2,3,5,6,8 etc.͔.…”