Optimization of excimer laser annealing on low temperature polysilicon for thin film transistor applications

Excimer laser annealing (ELA) amorphous silicon (a-Si) to poly-silicon (poly-Si) in different gas environment, i.e. N
₂
or N
₂
mixed O
₂
:2%, is studied for the fabrication of thin film transistors (TFTs). Influence of laser power on the surface morphology, grain size and height of gibbous grain is investigated. The variation of threshold laser power for the generation of surface ablation in N
₂
and N
₂
:98% mixed O
₂
:2% environment is also discussed. From experiment, it is found that the combination of O
₂
:2% enhance the threshold laser power for the generation of surface ablation from 320mJ/cm
²
to 390mJ/cm
²
. In the condition of average grain over 0.25mum, the process window is 30mJ/cm
²
for N
₂
, but is 50mJ/cm
²
for N
₂
mixed O
₂
:2% environment