Width dependent degradation of polycrystalline silicon TFTs

Abstract

The DC stress induced device degradation of sequential lateral solidification (SLS) polysilicon thin film transistors (TFTs) was investigated by monitoring the threshold voltage in the linear regime of operation. Devices with different channel widths were compared. It was observed that the degradation of device parameters during hot carrier experiments was dependent on the channel width. The origin of this dependence is ascribed to self-heating effects.

Instability dependent upon bias and temperature stress in amorphous‐indium gallium zinc oxide (a‐IGZO) thin‐film transistors

“…When the TFTs are subjected to high fields, there temperature is increased, which is the "self-heating effect." 17,18 We can confirm this self-heating effect by investigating the drain bias dependency according to temperature. In Fig.…”

Degradation and lifetime estimation of n-MOS SLS ELA polycrystalline TFTs during hot carrier stressing: effect of channel width in the regionVth⩽VGS,stress⩽VDS,stress/2

“…The relationship between the variations of the two parameters (V th and G m,max ) depends only on their relative values and does not depend on different possible degradation mechanisms for devices with different widths. Indeed, even though for different stress conditions (V GS,stress = V DS,stress ), it has been reported [23] that the channel width affects the intensity and not the mechanism of device degradation. Moreover, it is noted (figure 9) that when the threshold voltage variation becomes prominent, the percentage change of transconductance is found to be approximately above 15-20%, which implies that the threshold voltage variation is apparent and is attributed to the contribution of G m,max to V th and is not originated by a significant carrier trapping mechanism.…”