- 學位論文
濺鍍法製備Ag-Ge及Ta-Ge之特性
Properties of Co-Sputtered Ag-Ge and Ta-Ge Thin Films
摘要
積體電路主要的研究方向，主要在降低RC-delay，提升元件速率與改善電致遷移現象，現階段仍以銅製程為主，在尺寸持續縮小的情況下會有嚴重的RC-delay及階梯覆蓋率等問題，因此本論文嘗試以Ag-Ge及Ta-Ge合金，探討Ag-Ge與Ta-Ge之特性，研製低阻值，高熱穩定性之合金材料，以提供連導線製程新的研究方向。 本實驗使用多靶磁控濺鍍法製備Ag-Ge與Ta-Ge合金薄膜，Ag-Ge合金薄膜濺鍍於Si基板，Ta-Ge合金薄膜濺鍍於SiO2基板將製備合金薄膜在RTA中做300-700℃的熱處理後，利用四點探針(FPP)、X光繞射分析儀(XRD)、掃描式電子顯微鏡(SEM)、化學分析電子光譜儀(ESCA)、能量散射光譜儀(EDS)及穿透式電子顯微鏡(TEM)，分析薄膜之電性、相變化、微結構、熱穩定性及表面形貌，並進行附著性測試。 在製備Ag-Ge薄膜方面，Ag採DC濺鍍而Ge採RF濺鍍，由於Ag和Ge的原子大小、熱膨脹係數相近且結構相同，希望形成附著性佳且電阻低的薄膜，XRD結果中顯示熱處理後部分Ge固溶進Ag形成固溶體。電性測量發現添加少量的Ge即會使薄膜電阻上升，由 SEM圖觀察薄膜的Ag晶粒都有聚集的現象。Ag50Ge50熱處理超過600℃時薄膜會開始有孔洞，但薄膜比例銀含量越高，熱穩定性越好。最後進行附著力測試，薄膜中Ge比例少於30%時，薄膜產生脫落，退火後的薄膜附著力會有些許增加。兼顧附著性及電阻率，500℃熱處理之Ag70Ge30薄膜具備最佳的電阻值為29 μΩcm及附著力。 Ta-Ge薄膜方面，Ta採 DC濺鍍Ge採RF濺鍍，為避免Ta和Si產生反應選用SiO2基板，主要觀察不同成分比例的Ta-Ge薄膜特性。XRD檢測在不同成份比的薄膜中，發現Ta5Ge3及TaGe2的相，對照FPP的測量Ta5Ge3的相形成時電阻率沒有明顯變化，而TaGe2的相形成時電阻率下降，Ge51Ta49熱處理600℃持溫30 min薄膜得到最低的電阻110 μΩcm。SEM表示Ge10Ta90的薄膜附著性較差，在初鍍膜便有少許脫落情形，隨退火溫度增加附著力增加。
並列摘要
Silver and its alloys have bean promising in the multilevel metallization of semiconductor devices because of their superior electrical resistivity and resistance to electromigration. In this study, Ta-Ge and Ag-Ge thin films have been deposited on Si or SiO2/Si substrate by Magnetron sputtering. The as-deposited samples with Ag-Ge/Si and Ta-Ge/SiO2/Si structure were rapidly thermally annealed under Ar+H2 (5%) ambient at various temperatures. In the work, the phase and thermal stability of the thin film alloy ware mainly evaluated by employing XRD, FE-SEM and XPS and the electrical measurements was employed by 4-point probe method. The results showed that pure Ag thin film and a resistivity of 2.1 μΩcm, and that the resistivity of the Ag-Ge films increased with increasing Ge content. The Ag95Ge5 film had the lowest resistivity of 4.5 μΩcm. The XRD patterns for Ag-Ge thin film showed that grain size increased with increasing in annealing temperature, and also increased in adhesion. SEM images of Ag40Ge60 and Ag50Ge50 thin films showed that the porosity of Ag-Ge thin films increased with increasing in Ge content. The TaGe2 and Ta5Ge3 compounds could be formed within a range from 35.94% to 48.86% Ta atomic concentration from XRD results. A sharp decrease in resistance was found when the Ge51Ta49 sample was annealed at 600℃ for 30 min because of the formation of TaGe2.