氟雜質對化學氣相沉積鎢膜閘極MOS電容的影響

Abstract

本論文研究氟雜質在低壓化學氣相沉積鎢膜技術在極大型積體電路上 之應用。本論文將討論一般性的化學氣相沉積鎢膜(the typical CVD tungsten)和一種新穎之化學氣相沉積非晶鎢膜(amorphous-like CVD tungsten)在MOS電容上的研究。另外為了有效控制氟雜質在閘極氧化層的 擴散，快速加熱處理(RTA)將使我們可達成此一目的並更可以研究氟雜質 濃度和其分佈對化學氣相鎢膜閘極MOS電容的電性所受的影響。 從二次 離子質譜分析(SIMS)中，我們可確知一般性化學氣相沉積鎢膜 (the typical CVD W) 存在著比另一種化學氣相沉積非晶鎢膜(amorphous-like CVD W)有較高濃度的氟雜質。同時，我們更發現一般性化學氣相沉積鎢 膜(the typical CVD W)在崩潰電荷(QBD)及崩潰電場(EBD)有較多被破壞 的分佈。而另一種本身就含有較低氟雜質濃度的化學氣相沉積非晶鎢膜( amorphous-like CVD W)則顯現有較佳的電性表現。 在本文中，我們 可以發現經由快速加熱處理(RTA)所擴散入閘極氧化層的氟雜質會對MOS電 容的電性有嚴重的影響。而含有較少氟雜質濃度及具有不錯電性表現的化 學氣相沉積非晶鎢膜(amorphous-like CVD W)被認為將是在多晶矽膜結構 電容上較佳的金屬電極。 This thesis studies the effects of fluorine in the low pressure chemicalvapor deposited tungsten film(CVD-W) for ULSI circuit applications. The typical CVD-W film and the new gas phase nucleated CVD-W film are performed in this work. In order to control the diffusion of fluorine into the oxidesprecisely, the rapid thermal annealing(RTA) was used to allow us to studythe impact of fluorine concentration and its distribution on the electricalproperties for CVD-W gate capacitors. The typical CVD-W exhibited higher fluorine concentration than the gasphase uncleated CVD-W was further confirmed in the SIMS analyses. We also found that the typical CVD-W sample has more damage distribution in chargeto breakdown and dielectric breakdown field. The gas phase nucleated CVD-Wsample with originally lower fluorine concentration was found to have superior electrical properties. In this work, it is concluded that the amount of incorporated fluorinewith RTA process in gate oxide has a dramatic impact on the electrical characteristrics of MOS capacitors. Lower fluorine concentration and comparable electrical properties to traditional polysilicon gate structurefor amorphopus-like tungsten film was confirmed to be a candidate formetal electrode on polysilicon gate structure.