深次微米部分空乏型矽在絕緣層上金氧半場效電晶體之低頻雜訊特性研究

Abstract

近年來，由於矽在絕緣層上互補式金氧半場效電晶體(SOI CMOS)的先天結構優勢，使其成為積體數位以及射頻應用方面的新選擇。然而，由部分空乏型SOI金氧半場效電晶體中的基體懸浮效應抑或界面陷阱所產生的低頻雜訊卻會在電路或是系統中造成問題。此外，它也是射頻類比電路中一項重要的評量指標。在本篇論文中，我們將探討部分空乏型SOI金氧半場效電晶體的低頻雜訊分別在基體懸浮和基體接地時，隨汲極偏壓、溫度、通道長度變化的特性。實驗中，我們使用HP4156A半導體參數分析儀來量測元件的電流電壓特性。而低頻雜訊的量測則是同時結合了BTA9812雜訊分析儀以及HP35670A動態訊號分析儀來完成。 在基體懸浮元件中，由於基體懸浮效應，因此可以觀察到一個似羅倫兹雜訊過沖(Lorentzian-like noise overshoot)；此雜訊過沖在較高的汲極偏壓、溫度以及較短的通道長度下會被抑制。這裡我們採用一種以汲極到基體接面漏電所產生的散彈雜音(shot noise)和源極到基體阻抗，彼此間之交互作用為基礎的模型來解釋所觀察到的雜訊行為。在基體接地的元件中，雜訊過沖會被抑制住，而且只能觀察到閃爍雜音(flicker noise)。由閘極所看入的閃爍雜音在線性區正比於所施加的閘極電壓平方以及反必於通道長度，並且和溫度的改變無關。這表示，部分空乏型元件中的閃爍雜音主要是由通道中陷阱所產生的移動率擾動所造成的。 此外，在論文中也探討了熱載子效應對SOI元件中低頻雜訊的影響。在經過熱載子應力之後，由於閘極引發的汲極漏電流(GIDL)增加，使得基體懸浮元件中的似羅倫兹雜訊過沖會往較高的頻率移動，而雜訊的平台值會減小。再者，經過熱載子應力後，如果交換源極和汲極，所量測到的雜訊過沖，將因基體懸浮效應的降低而被抑制。至於閃爍雜音，不論在基體懸浮元件還是基體接地元件中都會因為應力後介面缺陷態的增加而增加。

In recent years, SOI CMOS have been proposed as a candidate for integrated digital and RF applications due to its inherent predominance. However, the low-frequency noise in partially depleted (PD) SOI MOSFETs due to floating-body effect or interface trap would cause problems in circuit or system, and also be an important figure-of-merit for RF analog circuits. In this thesis, we investigate the low-frequency noise characteristics of PD SOI MOSFETs with floating-body structure and source-to-body-connected structure at various drain biases, temperatures, and channel lengths. The current-voltage characteristics of devices were measured using HP4156A semiconductor parameter analyzer. The low-frequency noise measurements were performed using a BTA9812B noise analyzer in conjunction with an HP35670A dynamic signal analyzer. For floating-body devices, a Lorentzian-like noise overshoot was observed due to floating body effect. The noise overshoot can be suppressed at high drain bias, high temperature, and short channel length. A model based on the interaction between the shot noise of the drain-body junction leakage and the source-body impedance has been adopted to explain the noise behavior. For source-to-body-connected structure, the noise overshoot was suppressed and only 1/f noise existed. The input-referred 1/f noise is proportional to the square of gate drive voltage and the reciprocal of gate length in linear operation, and is independent of temperature. It suggests that the 1/f noise in PD devices is dominated by the trap-induced mobility fluctuation in the channel. The hot-carrier effect on the low-frequency noise of SOI devices has also been studies in this thesis. After hot-carrier stress, the Lorentzian-like noise overshoot in floating-body device moves to higher frequencies and the plateau of the noise overshoot reduces due to the increase of gate-induced-drain-leakage current. Moreover, as the source and drain interchanged, the noise overshoot can be eliminated with the reduction of floating body effect after stress. For both floating-body and source-to-body-connected devices, the 1/f noise increases after stress due to the increase of interface states.