Impact of Silicon Nitride Gate Dielectric Composition on the Stability of Low Temperature Nanocrystalline Silicon Thin Film Transistors

摘要

We report on the stability of nanocrystalline silicon (nc-Si) bottom gate (BG) thin film transistors (TFTs) with various compositions ([N]/[Si]) of hydrogenated amorphous silicon nitride (a-SiNx:H) gate dielectric, formed at 280°C. The shift in threshold voltage (△VT) is larger for gate dielectrics with lower [N]/[Si] content. For example, after 5 hours of stressing at 15 V, the △Vt is 0.3 V, 1 V, and 12.4 V for [N]/[Si] of 1.3, 1.2, and 1, respectively. Relaxation tests on the stressed TFTs show that the charge trapping in the gate dielectric is the primary instability mechanism in nc-Si BG TFTs.