Extraction of trap states in laser-crystallized polycrystalline-silicon thin-film transistors and analysis of degradation by self-heating

Trap states at the oxide-silicon interface and grain boundary in laser-crystallized polycrystalline-silicon thin-film transistors were extracted. The oxide-silicon interface traps and grain boundary traps can be extracted using the low-frequency capacitance–voltage characteristic and current–voltage characteristic, respectively. The traps above and below the midgap can be extracted using n-type and p-type transistors, respectively. The oxide-silicon interface traps consist of deep states and therefore seem to be caused by dangling bonds. The grain boundary traps consist of tail states and therefore seem to be caused by distortion of silicon-silicon bonds. Moreover, degradation by self-heating was analyzed. The oxide-silicon interface traps increase after the degradation. This means that silicon-hydrogen bonds are dissolved, and dangling bonds are generated. The grain boundary traps also increase a little.