Fabrication methods of gray tone mask for TFT process

• Main Authors: Wei-Ming Tsao, 曹偉銘
• Other Authors: 薛英家
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/00034497086638096500

碩士 === 國立中興大學 === 精密工程學系所 === 95 === When thicknesses are different on chromium mask, it will result in different transmittance. As the exposure energy varies onto photo resist, it is found different photoresist remained thicknesses and profiles after development. This technique has been applied to the photo process of semiconductor (SE) layer, source/drain (SD) electrode for TFT device fabrication. It is called 4-mask TFT process. After exposure and develop processes by using gray tone mask, the photoresist thicknesses are different in semiconductor and source/drain region. By adopt a plasma ashing step after semiconductor island etching, the thinner portion of source/drain region is removed. Thus, the two processes, SE and SD photo steps, can be combined into one single mask. It can improve the yield caused by the non-uniform photo problem in present 4-mask TFT process. The applications of gray tone masks have been studied in this thesis. Thickness of the mask will been confered with transmittance and photoresist remained after photolithography in this study. It is been found that the thicknesses of mask and transmittance are not in direct proportion, but there are relationships between the transmittance of the mask and the photoresist remained.