Hot-carrier-induced modifications to the noise performance of polycrystalline silicon thin-film transistors

Modifications of noise performances induced by hot-carrier degradation in polycrystalline silicon thin-film transistors, made by excimer laser crystallization, are presented. In particular, the normalized drain current spectral density of these devices shows an evident 1/f behavior, and as the device characteristics are degraded by prolonged bias stressing, the noise performances worsen. Hot-carrier degradation results in the formation of both interface states, that have been evaluated through the analysis of the sheet conductance, as well as of oxide traps near the insulator/ semiconductor interface, as evidenced by the 1/f noise measurements. A strong correlation between interface state and oxide trap densities has been found, suggesting a common origin for the generation mechanism of the two types of defects.