Abstract
In order to fabricate the medical image sensor circuitry, we must fabricate the poly-Si TFT to replace with the a-Si:H TFT . Our group have researched the poly-Si films which were fabricated by ECR-CVD hydrogen dilution method many years . But if we want to apply them to our device, they all have a big problem . That is the surface roughness of the poly-Si film . From our previous result, the surface roughness is a major problem to fabricate the top gate TFT . Even though the grain size is about 1□m, the RMS surface roughness is almost 90nm . For such a rough surface, it can not apply to the top gate poly-Si TFT . We have several to improve the surface roughness . First, take the hydrogen dilution samples to CMP process . We get a smooth surface and the RMS only 0.4nm . It improves a lot in surface roughness . Second, we change the way to deposit the poly-Si film . We use the layer by layer technique to deposit poly-Si film . From AFM and XRD, we really get improved in surface roughness . The grain size is several hundred nm, and the RMS surface roughness improved to 40nm for longer treatment time, even 10nm for short treatment time . Third, we use the layer by layer technique . But we change the hydrogen atom with deuterium atom . We found that the grain size became smaller, and the RMS surface roughness also became smaller (about 10nm). We thought it maybe the larger etching rate of deuterium . We also fabricate poly-Si TFT by SPC technique . We use the SPC to deposit poly-Si, and use it to fabricate TFT to conform the process work or not .