本研究目的在製作鉭(Ta)及氮化鉭(TaNx)薄膜並探討其材料特性，以應用於銅-矽晶基材間之擴散阻障層。利用反應性射頻磁控濺鍍製程，在固定氬氣(Ar)流量的氣氛下，將鉭(Ta)金屬薄膜沉積至(100) n-type矽晶基材，利用X光繞射分析(XRD)、掃描式電子顯微鏡(SEM)、電阻率量測及-step膜厚量測，觀察基板偏壓(substrate Bias)變化對鉭(Ta)金屬薄膜之結構、電阻率(ρ)、及沉積速率的影響。這些結果發現在矽晶基材上會沉積出電阻率約200 μΩ-cm之介穩態正方體β-Ta，隨著Bias變化，β-Ta薄膜之電阻率呈一向下趨於平緩的曲線變化。此外由XRD可觀察到不同的Bias下，β-Ta薄膜顯微結構的變化，應是影響電阻率的主要原因之一。
確切掌握β-Ta薄膜製程以後，本研究進一步探討在不同氮氣/氬氣流量比例的氣氛下，將不同氮含量之鉭基(TaNx)薄膜沉積至矽晶基材上，薄膜沉積完畢後以掃描式電子顯微鏡觀察表面，X射線光電子能譜儀(XPS)分析薄膜表面的化學鍵結，穿透式電子顯微鏡(TEM)觀察微結構變化，再利用XRD觀察到在不同的氣體流量比下，將發生一連串的相轉變行為，依氮氣流量的增加，相的改變由複晶Ta轉變為非晶質Ta2N、複晶TaN及複晶Ta4N5，此外TaNx薄膜在電性上亦產生實質的變化。
接著探討由不同組成與結構設計之Ta-N薄膜，其在『Si/Ta-N/Cu』金屬化系統中高溫擴散阻障行為。所採用之結構如下：
Cu / Ta / Si 結構
Cu / Ta2N(RT.) / Si 結構
Cu / Ta2N(100℃) / Si 結構
Cu / Ta2N(200℃) / Si 結構
Cu / TaN(1%) / Si 結構
Cu / TaN(2%) / Si 結構
Cu / TaN(4%) / Si 結構
對試片分別在500、600、700及800℃下退火30分鐘，用四點探針量測片電阻變化，低掠角X光繞射分析(GIAXD)分析各鍍層相變化及反應物的成份，掃描式電子顯微鏡觀察銅膜表面型態，歐傑電子能譜(AES)縱深元素分析，藉以知道『Cu / Ta-N / Si』金屬化系統各層結構的變化。
比對GIAXD、SEM、AES的結果顯示上述幾種不同的結構在退火後有不同的行為，Cu / Ta / Si 結構與Cu / Ta2N(RT.) / Si 結構在800℃/30分鐘退火後片電阻值明顯上升，造成電阻上升的原因為高電阻相(Cu3Si,TaSi2)的生成及表面銅膜產生球化不連續所導致；Cu / TaN(4%) / Si 結構在800℃/30分鐘退火後片電阻值亦明顯上升，造成電阻上升的原因為表面銅膜產生球化不連續所導致；Cu / Ta2N(100℃) / Si 結構、Cu / Ta2N(200℃) / Si 結構與Cu / TaN(2%) / Si 結構在800℃/30分鐘退火後片電阻值僅些微上升，雖高電阻相已生成，但仍可觀察到有殘留部分的Cu膜，顯示阻障層仍能維持其熱穩定性；Cu / TaN(1%) / Si 結構800℃/30分鐘退火後片電阻值仍維持一定，推論Cu膜仍維持連續性且表面無高電阻相生成，顯示有較好之熱穩定性。

The objective of this dissertation is to study the material characteristics of sputtered Ta and TaNx thin films and the viability of employing them as the diffusion barrier between copper and silicon. On the first part, Ta films are deposited on n-type Si (100) substrates at a fixed argon flow. Phase identification of the deposited films is performed by X-ray diffraction (XRD). Tantalum surface morphology is inspected by scanning electron microscopy (SEM). Resistivity is measured by the four-point probe method (FPP). It is found that substrate bias (VBias) affects the film resistivity (ρ), structure and deposition rate. The results show that the as-sputtered Tantalum film is the tetragonal β-Ta phase with resistivity of 200 μΩ-cm, which decreases gradually as increasing bias varies. Moreover, the microstructure of β-Ta films from XRD, which, is one of the major reason affecting with various bias.
Subsequently, the TaNx films with different atomic ratio were attempted by various N2/Ar+N2 ratio during sputtering. The TaNx films are analyzed by using SEM for surface morphology, X-ray photoelectron spectroscopy (XPS) for chemical bonding states, transmission electron microscopy (TEM) for microstructure, and XRD for phase identification. Experimental results reveal that the phase transformation of TaNx films with increasing nitrogen flow rates is in the sequence of poly-Ta, amorphous Ta2N, poly-TaN, and poly-Ta4N5. Accordingly, the electrical properties of TaNx films vary with the resulting phase. In the study of the diffusion barrier properties of Ta-N thin films for Cu metallization in ULSI circuit devices. The multilayered structures, Cu / Ta / Si, Cu / Ta2N(RT.) / Si, Cu / Ta2N(100℃) / Si, Cu / Ta2N(200℃) / Si, Cu / TaN(1%) / Si, Cu / TaN(2%) / Si, and Cu / TaN(4%) / Si, are compared and annealed in the vacuum chamber at 500℃,600℃,700℃,and 800℃ for 30 min following sputtering. Sheet resistance for films at each temperature is then measured by FPP. The phase identification is performed by glancing angle X-ray diffraction (GIAXD). Copper surface morphology is inspected by SEM. Auger electron spectroscopy is used to evaluate the degree of the atomic inter-diffusion across the interface by compositional depth profile.
The results from GIAXD, SEM and AES analyses show that these structures exhibit different behaviors upon annealing. The sheet resistance of Cu / Ta / Si and Cu / Ta2N(RT.) / Si increases steeply after 800℃/ 30 min annealing. The resistance increase is due to the phases (Cu3Si, TaSi2) of high resistance formed and the spheroidization of copper film. The sheet resistance of Cu / TaN(4%) / Si also increases steeply after 800℃/ 30 min annealing, which is due to the spheroidization of copper film. Nevertheless, the sheet resistance of Cu / Ta2N(100℃) / Si, Cu / Ta2N(200℃) / Si and Cu / TaN(2%) / Si only increases marginly upon annealing at 800℃ for 30 min, which is due to the presence of residual continuous Cu films. Finally, the sheet resistance of Cu / TaN(1%) / Si remains the same upon annealing at the same conditions, probably caused by the absence of the formation of both high-resistive phase and spheroidization of the Cu films, implying this structure has best thermal stability.

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