Fabrication and High-Frequency Characterization of N-type Poly-Si Thin-Film Transistors
Lin, Ting Yao
Lin, Horng Chih
Huang, Tiao Yuan
|關鍵字:||N型多晶矽薄膜電晶體;光阻微調技術;小訊號參數;小訊號模型;截止頻率;n-type poly-Si thin-film transistors;photoresist-trimming techniques;small-signal parameters;small-signal model;cut-off frequency|
In this thesis, we have fabricated n-type poly-Si thin-film transistors (TFTs) and studied their high frequency characteristics. High frequency characteristics are affected easily by the parasitic components, hence reduction of these components is essential. Resistances of source, drain, and gate are reduced with the aid of Ni silicidation technique in this work. To effectively shrink the gate length, we used both over-exposure and photoresist-trimming techniques to shrink the dimension of the PR patterns. These actions are helpful in improving the high frequency characteristics. However, we found the fluctuation in the dimensions of the interdigital poly-Si gate patterns fabricated by double-pattering process is significant. The anomalously shortened gate lengths in the interdigital gate structures tend to increase the off-state current. We’ve also successfully extracted the small-signal parameters by using a small-signal model. The simulation results of S parameters agree well with the measured data, confirming the accuracy of the small-signal model. As compared with the device with single-gate pattern, the values of parasitic resistances become smaller and the values of parasitic capacitances increase in the interdigital gate structure. But it is still beneficial for improving cut-off frequency and maximum oscillation frequency with the interdigital gate structure. Although the extrinsic resistances are large and may affect the practical ac performance, the analysis is confirmed with the simulation results and proved to be reliable. From both the normalized data and the comparison of the experimental results with the simulation, it is observed that the trends of calculation agree well with the measurements.
|Appears in Collections:||Thesis|
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