Laser annealing technique for metal oxide TFT

A method to make a thin film transistor (TFT), the method comprising:

• providing a substrate;
• forming an oxide semiconductor layer over the substrate;
• forming a source metal on a source region of the oxide semiconductor layer;
• and
• forming a drain metal on a drain region of the oxide semiconductor layer, wherein a channel region of the oxide semiconductor layer is defined between the source region and the drain region;
• etching the source metal and the drain metal to expose the channel region of the oxide semiconductor layer;
• forming a dielectric oxide layer over the oxide semiconductor layer so that the dielectric oxide layer is contacting the oxide semiconductor layer;
• and
• annealing without crystallizing the oxide semiconductor layer by heating the dielectric oxide layer with an infrared (IR) laser radiation under ambient conditions to a temperature below a melting temperature of the oxide semiconductor layer, the oxide semiconductor layer and the dielectric oxide layer forming part of the TFT, wherein annealing the oxide semiconductor layer occurs after etching the source metal and the drain metal.