銅/氮化鉭/參雜氟二氧化矽/矽結構之熱穩定性

Abstract

本論文主要探討濺鍍法沉積之氮化鉭(TaN)作為銅(Cu)和具有低介電係數的參雜氟二氧化矽(SiOF)之間的擴散障礙層，於氮氣中熱處理30分鐘之熱穩定性。參雜氟二氧化矽(SiOF)是以TEOS、O2和CF4氣體的電漿化學氣相沉積法成長。在電性方面，吾人以熱處理後的「銅/氮化鉭/參雜氟二氧化矽/矽」(Cu/TaN/SiOF/Si)的電容崩潰電場量測、以及熱處理後的「銅/氮化鉭/參雜氟二氧化矽/二氧化矽/矽」(Cu/TaN/SiOF/SiO2/Si)的電容電壓量測，來評估障礙層的熱穩定性。在材料分析方面，吾人以掃瞄式電子顯微鏡及二次離子質譜儀來分析探討SiOF的劣化原因。 對具有25nm厚度氮化鉭之Cu/TaN/SiOF/Si電容而言，電容崩潰電場量測的結果顯示元件的熱穩定性可達500℃。但經由Cu/TaN(25或50nm)/SiOF/SiO2/Si的電容電壓量測顯示經過300℃熱處理時，因產生的氣體外洩而衍生的應力，會使TaN障礙層受到破壞。藉由在SiOF膜上作氮氣電漿處理，可使Cu/SiOF/Si的熱穩定性提升至500℃，而且可使SiOF在熱處理過程中，不會發生氣體外洩的問題，從而避免TaN障礙層受到損壞。

This thesis studies the thermal stability of Cu/SiOF/Si capacitor with and without Ta-nitride (TaN) barrier layer. The SiOF films were deposited by plasma-enhanced chemical vapor deposition (PECVD) with the process gases of tetraethylorthosilicate (TEOS), O2 and CF4. The Ta-nitride films were deposited using reactive sputtering in an Ar/N2 mixed ambient. In the electrical aspect, the breakdown field measurement on the Cu/TaN/SiOF/Si capacitors and capacitance-voltage (C-V) measurement on the Cu/TaN/SiOF/SiO2/Si capacitors were used to characterize the capacity of the barrier in the metallization system. Analysis techniques of SEM and SIMS were used to investigate the degradation mechanism of the capacitors. With a 25nm thick TaN barrier between Cu and SiOF film, the Cu/TaN/SiOF/Si capacitors were able to remain stable at temperatures up to 500℃ from the results of breakdown field measurement. However, the results of the C-V measurement and the SEM micrographs revealed the outgassing of the SiOF film during the thermal process at a temperature of 300℃ led to wreckage of the TaN barrier layer. N2O plasma treatment on the SiOF film improved thermal stability of the Cu/SiOF/Si capacitor up to a temperature of 500℃; moreover, the plasma treatment made the SiOF film immune from outgassing at elevated temperatures, and thus prevented wreckage of the covering TaN layer.