奈米氮化鈦晶粒對全閘極奈米線互補式金氧半場效應電晶體電路功率與延遲特性擾動之研究

Abstract

IC 產業如今已發展至十數奈米層級，目前有兩大方向值得我們繼續努力研 究，「後摩爾定律」(More Moore)與「超越摩爾定律」(More than Moore)。後 摩爾定律跟隨摩爾定律，繼續挑戰其極限，往尺寸縮小的方向努力，如採用新興 材料、不同的元件結構或先進的製程技術等。超越摩爾定律則是朝發展多樣化的 應用邁進，不僅提高晶片的性能，更增進新的功能，生醫晶片的應用更是發展中 的亮點。其中，奈米線場效應電晶體更是研究生醫感測晶片的重要一環。 隨著技術節點逐漸下降且元件尺寸持續地微縮，全閘極奈米線場效應電晶體 的發展更是受眾人所矚目的未來趨勢，除了應用於 IC 產業外，奈米線場效應電 晶體另一顯著應用即為元件與 CMOS 電路整合生醫晶片感測器。然而，擾動的 問題在越來越小的奈米層級元件中日益嚴重。因此，研究各種擾動源對於 10 奈 米全閘極奈米線場效應電晶體之電特性的影響是項急迫的議題。 擾動源可被區分為以下幾種:製成變異、隨機摻雜擾動、通道與絕緣層介面 擾動和隨機功函數擾動。由於隨機摻雜擾動與通道與絕緣層介面擾動的影響較 小，則本論文主要研究的擾動源為隨機功函數擾動與製程變異擾動，製程變異擾 動則以不同製程變異中影響較大的高寬比變異效應來代表。 本論文介紹了多種模擬隨機功函數擾動的方法，平均化功函數擾動模擬法、 改良式平均化功函數擾動模擬法、區域化隨機功函數擾動模擬法與 TCAD 內建 功函數擾動模擬法，比較過各方優缺點後，則本論文的研究採用區域化隨機功函 數擾動模擬法。另外，本論文中亦提出與介紹區域化隨機功函數擾動模擬法在不 同高寬比結構中的應用。 本論文採用經實驗校估過的三維度元件暨電路整合模擬技術來探討隨機功 函數擾動與高寬比變異效應對 10 奈米全閘極奈米線場效應電晶體的影響。除了 基本的直流與交流電特性的影響外，我們亦深入探討數位電路中時序參數、雜訊 邊界以及功率消耗受到隨機功函數擾動與高寬比變異效應時的變異度。 在直流的部分，當高功函數氮化鈦金屬晶粒越多時，對於 N 型元件而言， 導通電流與截止電流皆下降，而臨界電壓則與高功函數氮化鈦金屬晶粒正相關， 但在 P 型元件中則有著完全相反的趨勢。隨著氮化鈦金屬晶粒尺寸的減小，臨界 電壓、汲極感應位障降低和次臨界擺幅的擾動則逐漸減少。當我們同時考慮隨機 功函數擾動與製程高寬比變異時，對於有相同氮化鈦金屬晶粒尺寸的元件而言， 若其高寬比越大，受到擾動的影響則越小，這是由於高寬比較大的元件擁有較大 的等效閘極面積，而氮化鈦金屬晶粒尺寸則相對較小。而交流特性則和直流有相 同的趨勢:氮化鈦金屬晶粒越大與較小高寬比的元件有較大的電容擾動。 在時序分析中，下降時間比上升時間來的小是因為 N 型元件有較大的驅動 能力。隨著高功函數氮化鈦金屬晶粒的增加，高至低延遲時間與低準位狀態雜訊 邊界會變得更高，低至高延遲時間與高準位狀態雜訊邊界則變小，這是因為延遲 時間與雜訊邊界的擾動皆受到臨界電壓擾動的影響並與其有相同趨勢。所有的功 率包含靜態功率、短路功率及動態功率皆遵循較大氮化鈦金屬晶粒有較大擾動的 趨勢。受到隨機功函數擾動與高寬比變異效應之電路亦在本研究中被討論。 綜合以上所述，本論文探討全閘極奈米線場效應電晶體之元件與電路所受隨 機功函數擾動與高寬比變異效應的影響。此研究成果可作為生醫奈米線電晶體感 測器的發展之參考，並可供半導體工業界研發與改良先進元件結構和製程技術。

The semiconductor industry has become vigorous and developed for over 30 years, but now the IC industry has developed to ten nanometer level. In 2016, Intel has postponed the launch of 10-nm technology. It’s inevitable that Moore’s law has almost reached the limit. In order to get rid of the dilemma of the attenuating Moore’s law, there are two directions worth our efforts to study, “more Moore” and “more than Moore”. More Moore follows Moore’s law and continues challenging the limits by striving to reduce device’s size, such as the use of new materials, different structures, or advanced process technology. More than Moore is mainly focus on developing diversified applications. It not only improves the chip’s performance, but also promotes new features. The application of biomedical chip is the bright spot of the development. Furthermore, in the development of more Moore and more than Moore, nanowire transistor is an indispensable part in the research of biomedical sensor as a three-dimensional (3D) structure. Nowadays, the technology node has gradually extended to 10 nm from the sub-16 nm. Along with the diminishing device dimension, multi-channel structures have been proposed to maintain the high performance and high packing density. Gate-All-Around (GAA) nanowire metal-oxide-semiconductor field effect transistor (NW MOSFET) is the most promising structure for technology roadmap. In addition to the applications in IC industry, the other significant application of NW MOSFET is the device or CMOS integration circuit biomedical sensor. However, variability problems have become more serious as the device shrinking down to nanoscale regime. Hence, studying the characteristic fluctuation on 10-nm-gate GAA NW MOSFET has been an urgent issue. The fluctuation sources can be divided as: process variation effect (PVE), random dopant fluctuation (RDF), interface trap fluctuation (ITF), and work function fluctuation (WKF). Since the RDF and ITF have relatively small variations, we mainly focus on WKF and PVE. Besides, the variation of PVE is represented by the aspect ratio (AR) effect. In this work, a variety of WKF simulation methods are introduced: the average WKF method, the modified average WKF method, the localized WKF (LWKF) method, and the built-in TCAD method. After comparing the advantages and disadvantages of these methods, we adopt the LWKF method. In addition, the newly proposed application of LWKF method in different AR structures is introduced comprehensively in this thesis. In this thesis, we use an experimentally calibrated 3D quantum mechanically corrected device and circuit simulation to explore the 10-nm-gate GAA NW MOSFET impacted by WKF and AR effect. In addition to the direct current (DC) and alternate current (AC) properties, the timing and power characteristics operating in digital circuit influenced by WKF and AR effect are also investigated. For DC analysis, in n-type devices, the trends of on-state current and off-state current have both decreased as the number of high WK increases and threshold voltage Vth has positive dependency on the number of high WK. As for p-type devices, it shows reversed trend. The variations of Vth, drain-induced-barrier-lowering, and subthreshold swing are diminished with the reducing grain size for both n- and p-type devices. While considering WKF combined with AR effect simultaneously, the device of larger AR has less influence on device characteristics with the fixing metal grain size because the larger AR has large effective gate area and the grain size is relatively small. AC analysis shows that the devices with large grain size and small AR have greatest gate capacitance variation. In timing analysis, falling time is smaller than rising time owing to the larger driving capability of n-type device. Along with the increasing high WK number, high-to-low delay time and noise margin low become higher while low-to-high delay time and noise margin high decrease because both the fluctuations of delay time and NM follow the trend of σVth. All power consumption terms including static, short-circuit, and dynamic power have followed the trend that the larger the grain size is, the larger the fluctuation is. The circuit fluctuations suffered from WKF with different AR are also under estimated. In summary, the DC, AC, and digital-circuit characteristics of GAA NWFET affected by WKF and AR effect have been discussed. The results of this thesis can be a valuable reference for the development of nanowire biomedical sensors and can provide contemporary semiconductor industry to develop and improve the innovative technologies.