| Summary: | 碩士 === 國立臺灣大學 === 電子工程學研究所 === 104 === The research of the post metallization annealing in forming gas was performed to study the effect of fixed charge and its interface on InAsPSb with atomic layer deposition Al2O3 oxide. And it is not only to improve fixed charge and border trap of the metal-oxide-semiconductor and Fermi level pinning, but enhance the C-V modulation and reduce frequency dispersion in the accumulation. Three results were improved from experiment: (1) the trend of flatband voltage (VFB) shift with increasing temperature approaching ideal showed reduction of fixed charge on oxide layer, (2) The lower C-V stretch out presented reduction of interface charge, (3) the reduction of dispersion frequency and increment of Cmod indicated the improvement of interface characteristic.
The discussion of the effect of forming gas and N2 on the post metallization annealing for InAsPSb was conducted. The result showed that the difference of frequency dispersion, Cmod, C-V stretch out between old and new ones were small from analysis of capacitance-voltage curve, flatband voltage shift and leakage current of gate. It told that bonds were rearranged to fill vacancies on interface of Al2O3/InAsPSb to improve Fermi level pinning with almost the same flatband voltage in both oxygen and non-oxygen environment. It was found that fixed charged on oxide layer was mainly influenced by annealing temperature, not gas entering the environment. Leakage current was 107 higher in N2 environment than that in forming gas environment. N2 kept more oxygen and aluminum vacancies. When voltage bias was exerted, leakage current was easier to be generated in conductive filaments.
Different temperature of the post metallization annealing in forming gas was conducted. Cmod, frequency dispersion of accumulation capacitance and hysteresis flatband voltage difference ∆VFB were improved with increasing temperature in the environment of post metallization annealing temperature lower than 250℃, because thermal energy can rearrange bonds to fill vacancies on interface of Al2O3/InAsPSb, reduce defect of bonds on oxide layer and improve Fermi level pinning. When annealing temperature was higher than 250℃ and kept increased in environment, overheating can make stable bond become unstable and even broken again. The border trap on interface of semiconductor also increased. Cmod and frequency dispersion of accumulation capacitance decayed, while hysteresis flatband voltage difference kept the same. Higher thermal energy can densify oxide layer and reduce barrier of tunneling, but it led to increasing leakage current with higher temperature in the forming gas environment.
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