碩士 / 國立高雄大學 / 電機工程學系碩士班 / 104 / In order to achieve better electrical characteristics and reliability, device material and structure are contineously improved. Progressively, traditional planar MOSFET has been replaced by FinFET devices. In this work, N-type FinFETs with 20nm channel length are investigated.
FinFET developed from double gate to tri-gate single-fin structure, followed by multi-fin structure, which is investigated in this work. It is found that multi-fin structure provides better device performance than single-fin structure due to increased effective gate width, although the capability to control the gate is weaker under each fin for multi-fin structure. Furthermore, multi-fin structure shows better reliability under hot carrier injection (HCI) stress, which may be attributed to the existing of coupling effects between neighboring fins in multi-fin structure.
Gate material has transformed from traditional SiO2/poly-Si gate to high-k/metal gate (HK/MG). TiN and TaN are two of the most potential candidates for metal gate. It is found that TiN and TaN with different stack thickness can affect device characteristics. For TiN/TaN/TiAl metal gate stack, Ta and Al atoms will diffuse to the interface between metal gate and high-k layer to form dipoles, which can change the effective work function (EWF) and threshold voltage (VTH). When the barrier layer TiN/TaN becomes thicker, the Al diffusion to interface and EWF shift to mid-gap can be prevented.
Moreover, devices with different gate stack thickness have been characterized under HCI stress. It is suggested that Ta atoms diffuse into HfO2 to form Hf-Ta-O, which results in high-quality Si-O interface and impoves reliability. While the diffusion of Al atoms easily form Hf-Al-O, which induces more VTH shift after HCI stress. Different HCI stress voltages were further performed and the conclusion is similar that devices with thicker TaN stack show better reliability and stability.
| Identifer | oai:union.ndltd.org:TW/104NUK00442002 |
| Date | January 2016 |
| Creators | CHEN, SHIH-YAO, 陳詩堯 |
| Contributors | YEH, WEN-KUAN, 葉文冠 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 110 |
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