射頻金氧半場效電晶體

Abstract

本論文研究矽-金屬氧化物-半導體場效電晶體的高頻模型。電晶體的小信號S參數，在不同的偏壓狀況下量測，頻率範圍由100MHz到18GHz。由量測所得的S 參數中，我們發現了非準靜態效應的影響，包括了電晶體轉導的低通特性，以及由閘極所見的輸入阻抗含有非零的實部。另一方面由於基質的導電係數並非無限大，造成了汲極輸出阻抗在高頻時下降。為了能獲得較佳的S參數擬合，我們選擇了能夠成功的描述小尺寸元件特性的BSIM3v3模型。同一製程不同長寬的電晶體的直流特性用來抽取標準的BSIM3v3模型參數。我們加入源於非準靜態效應的閘極電阻，以及基質電阻網路。量測所得的S參數，作為額外電路元件最佳化時的標的。模擬得的S參數吻合量測所得者。我們也研究了閘極電阻與偏壓的關係，其趨勢與理論預測一致。

Small signal S parameters of a quarter micron Si MOSFET in common source configuration are measured from 100MHz to 18 GHz in different biasing conditions. From the S parameters we found the evidence of the non-quasi-static (NQS) effects, namely the low-pass nature of the transconductance, and the nonzero real part of the impedance looking into the gate. Also the output impedance is lowered by the finite conductance of the substrate. In order to fit the S parameters, we chose BSIM3v3, which is successful in describing the small geometry effects, as the basic model. DC characteristics of Si MOSFET of various channel lengths and widths were measured, and BSIM3v3 model parameters were carefully extracted. A gate resistor originating from the NQS effect showing up at the frequency range of interest, and a network accounting for the substrate resistance are added. The measured S parameters are used as the guideline in determining the added components. Good fitting was obtained. The variation of the gate resistance with bias was investigated, and was in agreement with the theory.