Temperature Coefficient of Poly-Silicon TFT and its Application on Voltage Reference Circuit With Temperature Compensation in LTPS Process

The temperature coefficient (TC) of n-type polycrystalline silicon thin-film transistors (poly-Si TFTs) is investigated in this paper. The relationship between the TC and the activation energy is observed and explained. From the experimental results, it is also found that TC is not sensitive to the deviation of the laser crystallization energy. On the contrary, channel width can effectively modulate the TC of TFTs. By using the diode-connected poly-Si TFTs with different channel widths, the first voltage reference circuit with temperature compensation for precise analog circuit design on glass substrate is proposed and realized. From the experimental results in a low-temperature poly-Si process, the output voltage of voltage reference circuit with temperature compensation exhibits a very low TC of 195 ppm/degC , between 25degC and 125degC. The proposed voltage reference circuit with temperature compensation can be applied to design precise analog circuits for system-on-panel or system-on-glass applications, which enables the analog circuits to be integrated in the active-matrix liquid crystal display panels.