複晶矽化鉑高溫穩定性之研究

Abstract

本論文主旨在於研究複晶矽化鉑之高溫穩定性。在複晶矽閘極上形成複晶 矽化鉑可以降低片電阻，從而達到降低延遲時間的目的。但是複晶矽化 鉑(600o)在後續製程中，經過 700℃60分鐘退火處理後，複晶矽化鉑的片 電阻便開始增加；當退火溫度大於 800℃時，片電阻隨著退火溫度的增加 而大幅度增大。藉由適當能量及劑量之含氟離子的植入，可以抑制複晶矽 化鉑片電阻的增加。實驗結果顯示，經由鉑之BF2+離子的佈植，在植入能 量為80KeV ，劑量為2E15cm^-2 時，經過 750℃60分鐘退火處理後，複晶 矽化鉑的片電阻保持不變。當退火溫度大於 750℃時，片電阻隨著退火溫 度的增加而增大。經由矽化鉑(PtSi)之BF2+離子的佈植，在植入能量為 80∼100KeV，劑量為2E15cm^-2 時，複晶矽化鉑的片電阻對退火溫度也有 類似的變化關係。由電子顯微鏡的檢視得知，經過 800℃60分鐘退火處理 後，複晶矽化鉑表面變得較粗糙，並且在矽化鉑剝除後的複晶矽表面有許 多小坑洞出現。由二次離子質譜分析儀(SIMS)分析結果顯示，經過高 於80 0℃ 60分鐘退火處理後，堆積在矽化鉑╱複晶矽界面的氟含量減少 ，這與複晶矽化鉑經過高於800℃ 60分鐘退火處理後不能保持完整的現象 一致。複晶矽化鉑閘極電容結構在經過退火處理後，與鋁╱複晶矽閘極電 容結構的比較發現：複晶矽化鉑閘極電容的漏電流密度比鋁╱複晶矽閘極 電容的漏電流密度大約大一個數量級(大約大十倍)。經過 700℃退火處理 後，複晶矽化鉑閘極電容的崩潰電場明顯劣化。此外，複晶矽化鉑閘極電 容的平帶電壓隨著退火溫度增加而改變，而鋁╱複晶矽閘極電容的平帶電 壓幾乎不因退火處理而改變。 In this thesis, the high temperature stability of PtSi/ poly-Si structure is investigated. The sheet resistance of the PtSi(600 o)/poly-Si structure unimplanted with BF2+ ion slightly increases after a 60 min anneal at 700℃, and then it continues to increase rapidly with increasing annealing temperature. The sheet resistance of the PtSi(600o)/poly-Si structure implanted with BF2+ ion at 80 KeV to a dose of 2E15 cm^-2 remain keep fairly stable after a 60 min. anneal at temperature up to 750℃. Above that temperature, the sheet resistance increases with increasing annealing temperature. For the sheet resistance of the PtSi(600o)/poly-Si structure processed by the ITS scheme with BF2+ implantation at 80 ~ 100 KeV to a dose of 2E15 cm^ -2, similar behavior is observed for the sheet resistance. For the 60 min annealing at 800℃, the surface of the PtSi film becomes rough, and small pin holes appear on the surface of poly-Si after removal of the PtSi film. SIMS analysis indicates that the amount of fluorine piled-up near the PtSi/poly-Si interface decreases after annealing at temperatures higher than 800℃. This is consistent with the observation that the integrity of the PtSi(600o)/poly-Si structure cannot sustain the annealing treatment at temperatures higher than 800℃ for 60 min. The leakage current density of the Pt-polycide gate capacitors is about one order of magnitude higher than that of the Al/poly-Si gate capacitors. This is observed for both the unannealed capacitor and the various correspondingly annealed capacitors. For the annealing treatment at temperatures higher than 700℃, obvious degradation in breakdown field is clearly observed for the Pt- polycide gate capacitors. The negative flatband voltage of the Pt-polycide gate capacitor decreases with increasing annealing temperature, while the flatband volt- age of the Al/poly-Si gate capacitor remains nearly unchanged.