Piezoresistive Sensitivity, Linearity and Resistance Time Drift of Polysilicon Nanofilms with Different Deposition Temperatures

Abstract

Our previous research work indicated that highly boron doped polysilicon nanofilms (≤100 nm in thickness) have higher gauge factor (the maximum is ∼34 for 80 nm-thick films) and better temperature stability than common polysilicon films (≥ 200nm in thickness) at the same doping levels. Therefore, in order to further analyze the influence of deposition temperature on the film structure and piezoresistance performance, the piezoresistive sensitivity, piezoresistive linearity (PRL) and resistance time drift (RTD) of 80 nm-thick highly boron doped polysilicon nanofilms (PSNFs) with different deposition temperatures were studied here. The tunneling piezoresistive model was established to explain the relationship between the measured gauge factors (GFs) and deposition temperature. It was seen that the piezoresistance coefficient (PRC) of composite grain boundaries is higher than that of grains and the magnitude of GF is dependent on the resistivity of grain boundary (GB) barriers and the weight of the resistivity of composite GBs in the film resistivity. In the investigations on PRL and RTD, the interstitial-vacancy (IV) model was established to model GBs as the accumulation of IV pairs. And the recrystallization of metastable IV pairs caused by material deformation or current excitation is considered as the prime reason for piezoresistive nonlinearity (PRNL) and RTD. Finally, the optimal deposition temperature for the improvement of film performance and reliability is about 620 °C and the high temperature annealing is not very effective in improving the piezoresistive performance of PSNFs deposited at lower temperatures.

Influence of current-induced recrystallization on piezoresistive properties of polysilicon nanosized thin films deposited at different temperatures

“…For 580°C and 600°C samples with more amorphous contents and small grains, the CIRC decreases the GB width and increases tunneling current through GBs. It enhances the tunneling piezoresistive effect [2] and increases the GF. For 670°C samples with large grains, the further reduction of scattering centers at GBs decreases the proportion of GB resistivity in film resistivity, and the variation in GB width could be neglected compared to large grain size.…”

“…Our previous research work [1,2] indicates that polysilicon nanosized thin films (PNTFs, ~80nm in thickness) exhibit larger gauge factor (GF ≥ 34) and better temperature stability than polysilicon thick films (> 200nm in thickness, GF is 20~25) at high doping level. It makes PNTFs potential for the fabrication and application of piezoresistive sensors with low temperature drift and high sensitivity.…”

Piezoresistive transduction optimization of p-doped poly-Silicon NEMS

“…These π and r the p-doped poly-Si [14]. For roximation, bl π is considered as ntration [15]. As mentioned, the in resistivity, so an accurate GB is essential.…”

Modeling and simulation of polysilicon piezoresistors in a CMOS-MEMS resonator for mass detection

“…For certain operating conditions, piezoresistive sensing can even be used to amplify rather than attenuate the electrical input to the resonator [6]. Since the discovery of piezoresistance, several generations of commercial device designers and academic researchers have designed piezoresistive sensors for diverse applications [7], [8]. This paper presents the modeling and simulation of longitudinal and transverse polysilicon resistors, which are deposited at the maximum stress points of a CMOS-MEMS resonator for mass detection, to study their resistance change with stress.…”