以氮化鎢做為擴散障礙層之研究

Abstract

本論文旨在研究以氣相化學沉積(CVD)之非晶鎢(amorphous-W)薄膜做 為氮化鎢(tungsten nitride)之基材，非晶鎢之薄膜沉積條件如下，矽烷 與六氟化鎢(SiH4/WF6)之流量比值為 12.5/5 每分鐘標準立方公分(sccm) ，沉積溫度為300℃，腔體壓力為100mTorr，沉積完鎢薄膜之後不破真空 ，直接以氮氣電漿(plasma)予以氮化反應(nitridation)，氮化鎢以二次 離子質譜儀(SIMS)及X光譜儀(XPS)分別分析鎢氮化之厚度與原子比為2:1 。 電性方面以N+-P淺擴散層二極體(shallow junction diode) 與片電阻(Sheet resistance)做為判斷擴散障礙層於熱處理後好壞之依據 ，80nm厚的非晶氮化鎢與鎢置於鋁及矽之間做為擴散障礙層，可改進熱穩 定性(thermal stability)，實驗證明此種結構的二極體在加熱至575℃ 30分鐘，可成功的阻止鋁與矽之間相互擴散，氮化鎢薄膜經X光譜儀分析 後得知，由於氮原子與氮分子填充於鎢的晶界(grain boundary)，消除快 速的擴散路徑所致。 This thesis studies the novel tungsten nitride (WNx) film prepared by nitriding the amorphous chemical vapor deposited tungsten (CVD-W) films. Tungsten films were deposited with conditions followed, the flow rate of SiH4/WF6 is 12.5/5 sccm, temperature is 300℃ and presure is 100 mTorr. The in-situ nitridating process is executed in N2 plasma without breaking vaccum. After nitriding process, secondary ion mass spectroscopy (SIMS) and x-ray photoelectron spetroscopy (XPS) were used to determine the thickness of WNx and the atomic ratio of W to N ratio in WNx layer is 2:1, respectively. The electrical characteristics of the n+-p shallow junction diodes and the sheet resistance were used to judge the effetcness of WNx barrier layer after thermal annealing. Nitridation amorphous tungsten layer (WNx/W) of 80 nm was inserted between Al and Si. It is successful to retard Al-Si interdiffuse. The results show that this structure can improve the thermal stability of W contacted junction diodes up to 575℃ for 30 min annealing. The effectiveness of W2N barriers is attributed to stuffing grain boundaries with N atoms as well as to eliminating the rapid diffusion paths in tungsten films. This is observed by XPS.