深次微米的N型金氧半電晶體對銦原子超陡分佈之研究

Abstract

本論文中我們研究了不同的銦原子佈植能量對通道最小尺寸為80nm的N型金氧半電晶體中（NMOS）之短通道效應和窄通道效應的影響。吾人首次發現在啟始電壓對閘極長度的曲線下，有不規則的橫跨產生。這種有趣的發現，伴隨著銦原子對通道佈植能量的減小而產生反向窄通道效應的降低，吾人可以把些現象歸因為銦原子在通道中無法活化而造成暫時的增大擴散效應降低。 接著，吾人首次驗證了極佳的特性和可靠度在閘極長度為80nm的動態啟始電壓的金氧半電晶體（DTMOS）。因為銦原子可以在空乏區域形成超陡峭的摻雜分佈，而可以形成低的啟始電壓，而且可以同時擁有大的基體效應（body effect）的優點，這是其他傳統的動態啟始電壓的金氧半電晶體所沒有的。在0.7伏特的操縱下，其結果為驅動電流可以達到348mA/mm，轉換電導（transconductance）為1,022 mS/mm, 且近臨界的斜率為74 mV/dec。而且實基體效應會在窄通道因為摻雜的分離而減小卻不會發生在銦原子佈植下的動態啟始電壓的金氧半電晶體。最後我們也發現可靠度在動態啟始電壓的金氧半電晶體下有較好的改善，特別是由銦原子佈植能量在150 KeV的動態啟始電壓的金氧半電晶體。

The effects of indium implant energy on short-channel effect (SCE) and narrow-channel effect (NCE) were studied on NMOS devices down to 80 nm channel length. An anomalous crossover in threshold voltage roll-off curves was observed, for the first time, on indium-implanted splits with different implant energies. This finding together with the observed reduction in reverse narrow-channel effect (RNCE) with reduced indium implant energy, can be explained by the suppression of transient enhanced diffusion (TED) due to indium deactivation. We have also demonstrated for the first time a high-performance and high-reliability 80 nm-gate-length dynamic threshold voltage MOSFET (DTMOS). Due to indium super steep retrograde In-SSR dopant profile in the channel depletion region, the novel In (150-keV)-doped-split DTMOS features a low threshold voltage and a large body effect to fully exploit the DTMOS advantage. These results are not possible with conventional DTMOS. Excellent transistor characteristics with drive current as high as 348 mA/mm, a record-high Gm of 1,022 mS/mm, and a subthreshold slope of 74 mV/dec, are achieved at 0.7 V operation. Moreover, the reduced body effects that have seriously undermined conventional DTMOS operation in narrow-width devices, are alleviated in the In-SSR DTMOS, due to reduced indium dopant segregation. Finally, we have found for the first time that hot-carrier reliability is also improved in DTMOS-mode operation, especially for In (150-keV)-doped-split DTMOS. Abstract Ⅰ Contents Ⅴ List of Figures Ⅶ List of Tables Ⅹ Chapter 1 INTRODUCTION 1 1.1 Reduction of Device Feature Length 1 1.2 Super-Steep-Retrograde Well 2 1.3 Dynamic Threshold Voltage MOSFET (DTMOS) 3 Chapter 2 Comparison of Indium-doped and BF2-doped nMOSFETs 6 2.1 Experimental 6 2.2 Effect of Transient Enhanced Diffusion 6 2.3 Effects of Mobility, Junction Capacitance and Hot-carrier Reliability 11 Chapter 3 Characteristics of Dynamic Threshold Voltage MOSFET 16 3.1 Short-Channel In-SSR DTMOS Performance 15 3.2 Narrow Channel Characteristics 19 3.3 Hot-Carrier Reliability 21 Chapter 4 Conclusion 23 Reference 25