鎢基金屬玻璃薄膜擴散阻障層之應用與CoCrNiAlSi中熵合金機械性質之研究

Abstract

本研究共涵蓋兩個研究主題：鎢基金屬玻璃薄膜在半導體擴散阻障層之應用與CoCrNiAlSi中熵合金機械性質之研究。 首先，為了解決積體電路中Cu易擴散至Si基板導致元件失效的問題，本研究開發非晶態W–Ni–B金屬玻璃薄膜，作為Cu/Si間的擴散阻障層。利用磁控濺射製備了 Cu（150 nm）/W–Ni–B（10 nm）/Si 多層結構，並在 700–950°C 下退火 30 分鐘。利用奈米壓痕技術和示差掃描熱分析儀(DSC)，分別測試了 W–Ni–B 金屬玻璃薄膜的機械性能和熱特性。亦使用穿透式電子顯微鏡（TEM）和能量散射光譜（EDS）進行元素分佈及相互擴散行為的研究。實驗結果顯示，W–Ni–B薄膜具備高硬度（20 GPa），以及 863°C和903°C的高玻璃轉變溫度與結晶溫度。此外，在退火溫度高達800°C時，W–Ni–B金屬玻璃薄膜能有效阻止Cu和Si之間的相互擴散。然而，在950°C的退火條件下，Cu/W–Ni–B /Si系統發生了原子相互擴散，並形成了具有高電阻率的Cu3Si化合物，導致W–Ni–B阻障層失效。由於其優異的阻障性能與高硬度的獨特組合，W–Ni–B 金屬玻璃薄膜被認為是銅互連技術中一種可靠的擴散阻障層。 第二部分則聚焦於CoCrNi中熵合金難以兼具高強度與高延展性的瓶頸，透過加入輕量元素Al與Si進行共同摻雜設計。Al促進B2相析出提升強度，Si則提供固溶強化，有助於改善合金整體機械性能。研究首先運用計算相圖法(CALPHAD)進行合金設計，透過計算熱力學模擬來預測其相形成，結果顯示合金系統將形成三種不同的相: FCC、B2 與 sigma 相。隨後在 CALPHAD 方法的指引下，本研究利用電弧熔煉技術製備了CoCrNi和(CoCrNi)97−xAlxSi3（x = 0, 3, 5, 7）中熵合金，合金經過均質化、冷軋(壓縮比～80%)與退火處理後，進行微觀結構與力學性能分析。結果顯示，隨Al含量增加，強度提升但延展性略降；其中(CoCrNi)92Al5Si3合金表現最佳，具備1203.7 MPa抗拉強度與48.5%延展性，且密度較原始合金降低約10%，顯示出其在結構應用中的巨大潛力。

Two main research topics were shown in the present study. The first part focuses on the performance of amorphous tungsten-based thin film metallic glass (TFMG) as a diffusion barrier between Cu and Si in integrated circuits. Due to the inter-diffusion between Cu and Si for Cu metallization, a qualified diffusion barrier layer in integrated circuits is essential to prevent the degradation of devices. The Cu (150 nm)/W–Ni–B (10 nm)/Si multilayered structures were fabricated by sputtering and annealed at 700–950°C for 30 min. The mechanical properties and thermal characteristics of W–Ni–B TFMG were evaluated by nanoindentation and differential scanning calorimeter, respectively. The transmission electron microscope-EDS elemental mapping and line scan were used to study the element distribution and inter-diffusion behavior of the multilayered structure. It was found that W–Ni–B TFMG possessed high hardness of 20 GPa and high glass transition/crystallization temperatures of 863°C/903°C. The W–Ni–B TFMG could effectively block Cu–Si inter-diffusion for the annealing temperature up to 800°C. Inter-diffusion and formation of Cu3Si compounds with high electric resistivity at 950°C annealing resulted in failure of the barrier layer. Based on its unique combination of excellent barrier performance and high hardness, W–Ni–B TFMG could be regarded as a robust diffusion barrier layer for Cu interconnect technology. The purpose of the second study is to achieve excellent strength-ductility synergy in CoCrNi-based medium entropy alloys (MEAs) with lightweight. To achieve this, lightweight elements of Al and Si were adopted as dopants, in which Al and Si could promote precipitation of B2 and sigma phases, respectively, in FCC matrix for strength enhancement and Si could also reduce the stacking fault energy to facilitate twin formation. The calculation of phase diagrams (CALPHAD) method was applied to facilitate the alloy design. Under the guidance of CALPHAD, CoCrNi and (CoCrNi)97-xAlxSi3 (x = 0, 3, 5, 7, 9) MEAs were fabricated using arc melting, followed by homogenization, cold rolling and recrystallization. The effects of Al and Si co-doping on the microstructures, mechanical properties and strengthening mechanisms of CoCrNi-based MEAs were investigated. Abundant twins were observed in Al-0 (for x = 0). The grain size decreased slightly with the increasing solute atoms but significantly in the presence of precipitates, while the hardness increased slightly with the increasing solute atoms but significantly in the presence of precipitates. Considering the synergistic strengthening mechanisms of solid solution strengthening, grain boundary strengthening and precipitation strengthening, the yield strength was calculated and compared with measurements. Compared to CoCrNi MEA, (CoCrNi)92Al5Si3 MEA exhibited an optimal combination of tensile strength (1203.7 MPa) and ductility (48.5 %). Moreover, the alloy's density was ~10% lower than that of CoCrNi, suggesting the great potential of the alloy for structural applications.