Investigation of Temperature-Dependent Mechanism of TCR in a-Si:H for Microbolometer Applications

This study investigates the temperature coefficient of resistance (TCR) of a-Si:H according to process conditions to find out the temperature-dependent mechanism for microbolometer applications. Four types of a-Si:H films were prepared using PECVD by adjusting the SCCM of the doping gases: high B ₂ H ₆ (B1), low B ₂ H ₆ (B2), high PH ₃ (P1), and low PH ₃ (P2). Secondary ion mass spectroscopy (SIMS) analysis is performed to confirm the doping concentration. N-type (P1 or P2) seems to be less favorable for improving the channel conductance, but it has a large TCR meaning that P2 has the highest temperature dependency as well as the largest absolute TCR value. After pre-annealing in D ₂ atmospheres, P1 and P2 show a significant reduction in the TCR. In addition, R _C is observed to be reduced with TCR after post-metal annealing. The 1/ _f noise is also correlated with TCR and is found to have a trade-off relation. These results imply that the TCR is primarily influenced by the trap states in a-Si:H film. Based on the experimental results, thermal-assisted transport through the local potential barrier is suggested for the temperature dependency of TCR in a-Si:H.