| Summary: | 碩士 === 長庚大學 === 電子工程學研究所 === 96 === In this work, after the poly-Si thin film transistors channel are deposited, we utilize high κ value material praseodymium titanium oxide to form the gate dielectric of the low temperature poly-Si thin film transistors by dual e-gun evaporation system, and use TiN as its gate electrode. Compare to the general high κ value material, using praseodymium titanium oxide as gate dielectric shows higher κ value, lower gate-leakage current, and superior thermal stability. Choosing TiN metal gate to replace conventional poly-Si gate can reduce process temperature and sheet resistance of the gate.
In addition, after channel are deposited, we utilize CF4 plasma treatment on it by plasma enhanced chemical vapor deposition (PECVD) system, then use praseodymium titanium oxide gate dielectric and TiN metal gate to form low temperature poly-Si thin film transistors. Compare with the poly-Si praseodymium titanium oxide gate dielectric TFTs using CF4 plasma treatment and control TFTs, the CF4 plasma-treated TFTs shows higher on current, lower gate-leakage current, gate-induced drain leakage (GIDL), and improves mobility and reliability.
Finally, we test the CF4 plasma-treated TFTs and control TFTs with hot-carrier stress and positive bias temperature instability (PBTI). The results show that the CF4 plasma-treated TFTs exhibit superior reliability characteristic. The improvement is a result of the fluorine passivation, which reduces trap-state density and forms stronger Si-F bonds in place of the weak Si-H bonds in the poly-Si channel and at the praseodymium titanium oxide gate dielectric/poly-Si interface. So the CF4 plasma treatment can promote hot-carrier stress and positive bias temperature instability (PBTI) immunity.
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