鎢化矽及氮化鉭在銅金屬化系統之擴散障礙特性

Abstract

本論文主要探討以低壓化學氣相法沉積之鎢化矽及濺鍍法沉積之氮化 鉭，作為銅和矽及銅和二氧化矽之間的擴散障礙層，於氮氣中熱處理30分 鐘之熱穩定性。其中鎢化矽膜係以矽烷(SiH4)還原六氟化鎢(WF6)方式成 長。在電性方面，我們利用「銅／障礙層／p+n」接面二極體及「銅／障 礙層／二氧化矽／矽」電容等結構，於熱處理後的電性劣化程度來定義障 礙層的熱穩定性。在材料分析方面，我們利用四點探針、X光繞射分析、 掃描式電子顯微鏡以及二次離子質譜儀，來探討其劣化原因。 對具 備50nm厚度鎢化矽障礙層之Cu/WSix/p+n二極體而言，元件的熱穩定性只 可達500℃；而藉由在鎢化矽膜上作氮氣電漿處理，可以提昇障礙層的擴 散障礙能力，使元件的熱穩定性提高到600℃。在氮化鉭方面︰對Cu/ TaNx/p+n二極體而言，使用25nm厚度氮化鉭的熱穩定性可達700℃，10nm 厚度氮化鉭的熱穩定性可達600℃，但對5nm厚度的氮化鉭而言，熱穩定性 只可達500℃。另一方面，對於Cu/TaNx/SiO2/Si電容，10nm厚度的氮化鉭 可以成功地阻止銅擴散到二氧化矽，其熱穩定性可達600℃。 This thesis studies the diffusion barrier properties of W- silicide and Ta-nitride with respect to Cu metallization. The W-silicide films were depositedby low pressure chemical vapor deposition using the SiH4 reduction of WF6 process. The Ta- nitride films were deposited using reactive sputtering in Ar/ N2 mixing ambient. In the electrical aspect, leakage current measurement on the Cu/barrier/p+n junction diodes and capacitance-voltage measurement on the Cu/barrier/SiO2/Si MOS capacitors were used to characterize the capacity of barrier in the metallization system. Degradation mechanism of the barrier films was investigated using the measurement and analysis techniques of sheet resistance, XRD, SEM, AFM, SIMS, and AES. For the Cu/WSix/p+n junction diodes with a WSix barrier of 50nm, the thermal stability of the diodes was found to reach 500℃; an in-situ N2 plasma treatment on the surface of WSix raised the stability temperature to 600℃. For the Cu/TaNx/p+n junction diodes, the thermal stability of the diodes was found to reach 700℃ for 25nm of TaNx, 600℃ for 10nm of TaNx, and 500℃ for 5nm of TaNx. For the Cu/TaNx/SiO2/Si MOScapacitors, a barrier film of 10nm thickness is able to maintain the devices integrity up to 700℃.