Negative Bias Temperature Instability in Low-Temperature Polycrystalline Silicon Thin-Film Transistors

Bias temperature instability comparison of CMOS LTPS-TFTs with HfO2 gate dielectric

“…In general, n value is below 0.2 for PBTI, which the oxide charge trapping dominated, and around 0.35-0.15 for traditional NBTI mechanism, which the interface trap states and oxide trap states are generated by hydrogen reaction and diffusion model [20,21]. Fig.…”

“…It is because the thick high-j gate dielectric HfO 2 would have many pre-existing traps, resulting in more charge trapping effect than the oxide charge generation merely by the hydrogen reaction and diffusion effect. Therefore, the mechanism of NBTI with HfO 2 gate dielectric is the combination of hole trapping, which is induced by gate voltage, and the hydrogen reaction model, which the interaction between Si-H bond and hole breaks the bonding to generate the interface trap state and hydrogen diffusion [21]. As a result, both PBTI and NBTI would increase the threshold voltage |V TH |, subthreshold swing S.S. and degrade the transconductance G m .…”

Instability of p-channel poly-Si thin-film transistors under dynamic negative bias temperature stress

“…Such phenomenon of turnaround clearly indicates two competitive degradation mechanisms. As is known, the negative V th shift is typical for DC NBTI degradation [2][3][4]. Obviously in dynamic NBT stress, t gp can be regarded as the DC NBT stress time and the DC mechanism can be introduced during t gp , thus brings the negative V th shift.…”

“…Negative bias temperature instability (NBTI) is a key reliability issue in p-channel TFTs [2][3][4][5]. The degradation under DC NBT stress has been widely reported [2][3][4][5], while that under dynamic NBT stress is still unclear. Some reported that the degradation was similar as that in DC NBT stress [6].…”

A New Observation of the Elliot Curve Waveform in Charge Pumping of Poly-Si TFTs

“…2, an LT TFT transfer curve at a drain voltage (V d ) of 0.1 V is plotted in semi-log and linear scales. V fb = 0 V is estimated as the V g bias of the minimum drain current (I d ) [12]. V th = 10 V is extracted as the intercept of linear extrapolation of the transfer curve.…”