新穎的功率電晶體於熱載子效應之特性化分析及模型建立

Abstract

在最近幾年，先進的CMOS技術已經成熟的應用在射頻RF (radio-frequence)這塊領域上面，像是無線通訊系統、藍芽技術的應用、WLANs以及超寬頻(ultra-wide band)等等。而微波元件又是通訊系統中最重要的骨架。當中又以矽為基底的金氧半場效電晶體已經成為射頻元件的主流。 整合的功率放大器對於SOC的應用上相當重要，因此發展適用的功率電晶體是必須的。而功率電晶體則需要可以承受較高的崩潰電壓以達到傳送較高能量和附加功率效能的功用。但傳統CMOS技術的缺點就是限制住輸出的崩潰電壓，這對於RF方面的應用而言，是一種矛盾的關係。所以一些文獻提出了改進的方法，諸如Drain-extended MOS (DEMOS)以及Lateral-Diffused MOS (LDMOS) transistors都可以提高崩潰電壓，但是他們在高頻特性的表現上面，卻沒有這麼地理想。 於是我們利用UMC的製程技術，從DEMOS的結構上去改變以達到改善的效果。而這新的元件命名為Pseudo-drain MOS (PDMOS)。本篇論文的重點即是討論這顆改善後新元件的直流特性和高頻特性，並將其結構做些改變，再將改變前後的兩個不同結構深入比較受到熱載子效應後的直流特性和高頻特性以及功率特性方面的行為，更進一步分析在熱載子效應下的可靠度比較。 最後，透過小訊號模型的建立，經由討論各別小訊號參數的變化情形，我們發現金氧半場效電晶體的互導，汲極到源極的電阻以及閘極到源極的電容還有汲極的電阻受到熱載子效應影響較大，特別是汲極電阻的變化，也輔助說明了這兩種不同結構在直流特性上的差異性。

In recent years, advanced CMOS technologies have been investigated and pushed to perform well in RF areas, like in wireless systems: Bluetooth applications, WLANs and UWB (ultra-wide band). Microwave transistors are the backbone of these modern wireless communication systems. Since the Si-based MOSFETs (metal-oxide-semiconductor field-effect transistors) have become the mainstream of RF transistors in recent years. The integration of the power amplifier for SOC realization is very important. Hence, the development of suitable power cells using MOS transistors is necessary to achieve this goal. Power transistors with high breakdown voltage are required to achieve higher power delivery and power added efficiency (PAE). But, the drawback of CMOS technology is the inherent limitation of a lower output breakdown voltage, and it is incompatible for RF power applications. Therefore, some literatures which addressed this issue introduced devices like the “Drain-extended” MOS (DEMOS) and the “Lateral-Diffused” MOS (LDMOS) transistors to obtain a higher breakdown voltage and power performance. However, the high frequency characteristics were degraded. In this thesis, we improved the performance from DEMOS by UMC technologies. And the new device is named Pseudo-drain MOS (PDMOS). The purpose of this thesis is to investigate the DC characteristic and RF characteristic of this new RF MOSFETs and then we do some variation on structures. Besides, we compare to go deep into the DC characteristic, RF characteristic and power performance which suffer hot carrier stress on different structure from changing before and after. Then we try to analyze the reliability under hot carrier stress. Finally, by way of building a small-signal model, we proposed that individually parameter after hot carrier HC stress, the transconductance(gm0), drain-to-source resistance(Rds), gate-to-source capacitance(Cgs), and drain resistance(Rd) suffer more degradation after HC stress. Especially the variation on drain resistance(Rd) could explain the difference between these two structures for their DC characteristics.