Raised source and drain structure of poly-Si TFTs

By a raised source and drain structure, we can fabricate a Poly-Si TFT with low sheet resistance at its source and drain region and low off stage current with a thin channel silicon region. With the structure, we separated the two fundamental issues for making high quality TFTs. A top gate Poly-Si TFT was fabricated by this technique. The characteristics of the TFTs were compared with conventional implanted source and drain region. To process the structure, we used a selective etching process for n+ film over Poly-Si channel. This technique can be used for large area source and drain doping without any problems regarding surface charging, channel silicon etching, and burned photo resist from ion doping.