多重閘極金氧半場效電晶體的本質參數變異特性分析

Abstract

本論文系統化地探討了三種重要的本質參數變異：隨機參雜濃度變動 (Random Dopant Fluctuation)、線邊緣的粗糙程度 (Line Edge Roughness) 以及等效氧化層厚度變異 (Equivalent Oxide Thickness Variation) 對於多重閘極金氧半場效電晶體變異特性的影響。更精確地說，我們利用Atomistic模擬以及傅立葉分析探討元件微縮對於多重閘極金氧半場效電晶體變異特性的影響。

經由模擬的結果我們得知：對於高參雜元件而言，隨機參雜濃度變動是最主要的變異來源。在低參雜的元件方面，我們探討了兩種不同類別的線邊緣粗操程度。第一個類別是悲觀地假設線邊緣粗操程度並不會隨著元件微縮而得到相對應的改善；在這個情況下，我們發現線邊緣粗糙程度對於多重閘極電晶體變異程度的影響將比隨機參雜濃度變動以及等效氧化層厚度變異嚴重。在第二個類別中，線邊緣粗操程度遵循ITRS對於不同世代電晶體理想的預測；我們發現在高度微縮的元件中，由於局部等效通道長度的變異，源極/汲極隨機參雜濃度變異的重要性將會逐漸升高。這意味著在低參雜濃度且高度微縮的多重閘極金氧半場效電晶體，利用Atomistic模擬來分析元件的變異特性是必須。

This thesis systematically investigates three important intrinsic parameter fluctuations, random dopant fluctuation (RDF), line edge roughness (LER) and equivalent oxide thickness (EOT) variation in multi-gate MOSFETs. Specifically, we have performed atomistic simulation and Fourier synthesis to investigate the impact of scaling on the variability of multi-gate devices.

Our results indicate that RDF is the dominant variation source for heavily doped devices. For lightly doped devices, two scenarios for LER have been examined. In the pessimistic scenario that the LER does not scale with the technology generation, we find that the LER will dominate over the RDF and EOT variation. In the optimistic scenario that the LER follows the ITRS roadmap for each technology node, the Source/Drain RDF becomes increasingly important in ultra-small devices because of the local variation of effective channel length. In other words, the atomistic simulation has to be employed for lightly doped extremely-scaled multi-gate devices.