| 摘要: | 隨著科技的進步，太空產業以及太空元件已經是不可或缺的技術，太空元件需要克服極端的特性，例如非常大的高低溫差、高輻射、真空環境散熱系統都是挑戰。另外量子電腦的推出，使得量子元件的研究需求大量增加，低溫 (Cryogenic Temperature) 金屬氧化物半導體場效電晶體 (Metal-Oxide-Semiconductor Field-Effect Transistor, MOSFET)元件廣泛的應用於量子元件，如何有效的讓系統表現符合預期，首先我們必須先對元件在不同極端狀況下的電性改變有所認識，進而將結果應用於電路中。在半導體的演進中，半導體的尺寸微縮隨著摩爾定律變化，較少相關研究專注於半導體的低溫特性分析，本研究對十六奈米的應變矽鰭式場效電晶體 (Fin Field-Effect Transistor, FinFETs) 展開低溫特性分析之研究，接著利用量測數據建構積體電路通用模式 (Simulation Program with Integrated Circuit Emphasis, SPICE)，最後透過SPICE模擬低溫特性中電路特性的變化。
本文提出十六奈米應變矽鰭式場效電晶體低溫準彈道傳輸電性的分析技術，載子在通道中飄移、散射、彈道傳輸是主要傳輸機制，根據文獻紀載通道長度小於10nm的元件彈道傳輸主導載子傳輸系統。通道介於10nm~100nm，彈道傳輸也大部分主導載子傳輸，但飄移、散射的影響力也不可忽視。這邊我們會說他處於準彈道傳輸 (Quasi-Ballistic Transport) 狀態，飄移、散射的特性可以藉由有效電子、電洞遷移率分析，本文利用電容-電壓量測 (Capacitance-Voltage Measurement) 計算出有效電子、電洞遷移率，我們可以發現隨著溫度降低，等效氧化層厚度 (Equivalent Oxide Thickness, EOT) 跟著減少至收斂。由於pFinFETs採用矽化鍺 (Silicon-germanium, SiGe) 做為源極和汲極的材料，電洞遷移率在低溫時將會大幅提升。有效遷移率的散射機制也在討論範圍包括聲子、表面、遙控 (remote) 散射機制。對彈道傳輸而言，本文使用虛擬源極傳輸模型 (Virtual Source Model, VSM) 萃取載子入射速度 (Injection Velocity) 以及源極-汲極電阻 (Source-Drain Resistance) 。載子入射速度隨著溫度降低而升高，pFinFETs改變較nFinFETs變化明顯。源極-汲極電阻在pFinFETs較nFinFETs大，主因是pFinFETs的源極-汲極使用SiGe而nFinFETs的源極-汲極使用Si。
分析低溫FinFETs的特性後，藉由量測數據分析的參數建立FinFETs的SPICE模型，這邊採用VSM模型，VSM模型使用量測數據與公式計算的擬合數據匹配，確認模型的準確度，進而推算Injection Velocity以及Source-Drain Resistance用以分析準彈道傳輸，最後藉由SPICE模擬反相器 (Inverter) 、 反或閘 (NOR) 、 反及閘 (NAND) 分析電路在低溫的電性變化。
綜合上述，本實驗首先透過16-nm FinFETs分析出低溫的準彈道傳輸特性，接著利用元件特性建構出的低溫應變矽準彈道傳輸之鰭式場效電晶體模型。並以此模型為基礎，分析電路層級中低溫的變化。
關鍵字： 鰭式場效電晶體、準彈道傳輸、虛擬傳輸模型、低溫、積體電路通用類比程式
;Through advancement of technology, space industry and space devices have become indispensable technologies. Space components need to overcome extreme characteristics in universe, such as huge temperature differences, strong radiation, and vacuum environmental cooling systems. Moreover, introduction of quantum computers has greatly increased the research demand for quantum electronic devices, and cryogenic temperature MOSFET devices are widely used in quantum devices. How can we make the system performance more effective? We must firstly understand electrical variability of devices under environmental extreme conditions, and then apply them and design in the circuit. With assistance of measurement data and the model of the Simulation Program Integrated Emphasis (SPICE) , the characteristics of the circuit in the cryogenic temperature characteristic can be simulated by SPICE.
In this paper, a strained silicon technology for cryogenic-temperature quasi-ballistic transport of 16 nm fin field effect transistors is proposed. Carrier drift, diffusion, and ballistic transport in the channel are main mechanisms of transport. Ballistic transport of devices with a channel length less than 10 nm dominates the carrier transport system. In the channel length between 10 nm and 100 nm, ballistic transport also plays an important rule in the carrier transport, but influence of drift and diffusion are still significant, known as the quasi-ballistic transport. Characteristics of drift and diffusion can be analyzed by the effective electron and hole mobility. In this paper, capacitance-voltage measurement is used to calculate effective electron and hole mobility. Then, we can find that with reduction of temperature, the equivalent oxide thickness (EOT) also reduces. Since the p-type FinFETs use silicon germanium (SiGe) as the source and drain material, the hole mobility increases significantly at cryogenic temperatures. Scattering mechanisms for effective mobility are also discussed, including phonon, surface, and remote scattering mechanisms. For ballistic transport, this paper uses the virtual source model (VSM) to extract the carrier injection velocity and source-drain resistance. The carrier injection velocity increases as the temperature decreases. That of the p-type FinFETs increases much more than that of n-type one. The source-drain resistance of the p-type one is larger than that of the n-type one in the cryogenic temperature, since SiGe is used for the source-drain of the p-type and Si is used for the source-drain of the n-type.
After the characteristics of the FinFETs at cryogenic-temperature have been analyzed, we use these results to construct an analytic model for simulation. The VSM model uses measured electrical properties of the FinFET, and then estimates the injection velocity and source-drain resistance by fitting measured data with calculated data. Next, we deploy this model into the Spice tool to simulate the electric characteristics of the inverter, NOR, NAND, and then analyze the impact of cryogenic temperature on the circuit.
Finally, this experiment first analyzes the quasi-ballistic transport characteristics of cryogenic temperature through 16-nm FinFETs, and then the cryogenic temperature strained silicon FinFETs model is constructed based on our measured device characteristics to predict electrical variations of cryogenic temperature in the circuit level.
Keywords: fin field effect transistors, quasi-ballistic transport, virtual source model, cryogenic temperature, Simulation Program with Integrated Circuit Emphasis |
