氣態氫氟酸清洗閘極氧化層及堆疊式閘極在不同晶面上之研究

Abstract

在本篇論文中，我們研究在成長閘極氧化層之前利用氣態氫氟酸清洗對pMOSFETs的影響，而除了採用傳統的Cz-wafer，我們還將元件製作在Hydrogen Annealed Wafer (Hi-wafer)來探討與Cz-wafer的差異。我們發現利用氣態氫氟酸清洗可以改善Cz-wafer和氧化層的界面缺陷，進而提昇元件的遷移率及驅動電流，但是氣態氫氟酸清洗對於Hi-wafer卻沒有明顯的改善。此外，由實驗結果發現製作在Hi-wafer上的元件界面缺陷密度會比製作在Cz-wafer上的低。最後，我們利用非晶矽及複晶矽堆疊的結構來製作元件的閘極，結果顯示此種堆疊結構的閘極可以有效的防止硼穿透，進而減少對pMOSFETs介電層的傷害。

In this thesis, the effect by using in-situ HF-vapor cleaning before gate oxidation for pMOSFETs on two different silicon substrates – Czochralski grown silicon wafer (Cz-wafer) and hydrogen annealed silicon wafer (Hi-wafer) has investigated. HF-vapor cleaning step can remove native oxide effectively and improve SiO2/Si interface quality. From the results, the drain current, interface-state-density and mobility are improved by HF-vapor cleaning with O2 oxide on Cz-wafer. However, it shows no improvement on Hi-wafer by HF-vapor cleaning. We also found that the interface-state-densities of pMOSFETs on Hi-wafer are lower than Cz-wafer due to the less oxygen impurities. In other words, devices fabricated on Hi-wafer show better interface quality. Finally, we used the stack gate (α-Si 500Å + poly-Si 1500Å) to compare with conventional single poly-Si gate. We found that pMOSFETs with stack gate can effectively suppress boron penetration.