高性能後化學機械研磨清洗技術之探討

Abstract

在雙鑲嵌技術中銅化學機械研磨製程之化學機械研磨後清洗為一道非常重要之製程。減少介電材質表面的有機、銅污染殘餘物為本研究的目標。在我們的研究中，提出一項採用HAL緩衝氫氟酸加上後來臭氧超純水清洗的新式化學機械研磨清洗。在TXRF(全反射X光螢光分析儀)的分析中，和目前雙鑲嵌技術銅清洗製程中所使用的檸檬酸清洗相比，展現出較佳的介電質銅污染清洗成效。 此外，AFM(原子力顯微鏡)平坦度驗證也顯示出比檸檬酸清洗有更平滑的表面。TDS（熱分解質譜儀）用於檢查後化學機械研磨清洗後銅及介電質表面的有機殘餘物。在HAL緩衝氫氟酸浸泡後及臭氧超純水清洗後發現較少的有機殘餘物。這樣的清洗成效歸功於臭氧超純水清洗有機物的去除效果及HF蝕刻之結果。 除了上述的分析之外，還實施電性特性化以驗證在重要奈米元件清洗過程中所提出的清洗方法的實際成效。結果顯示所提出的清洗方式得到比目前使用的檸檬酸清洗較佳的漏電、崩潰、電荷崩潰性能。依據上述所有的實驗結果，我們的清洗方式為可行的且優於傳統式化學機械研磨清洗 。

Post CMP cleaning is an inevitable process for copper CMP in dual damascene technology. Minimizing organic, copper contamination residues on the dielectric surface is a goal of our investigation. In our study, a novel post CMP cleaning using HAL buffer HF solution and subsequent ozone water clean is proposed. From TRXRF (Total Reflection X-ray Fluorescence) and AFM (Atomic Force Microscope) roughness verification analysis, the new cleaning method has better copper clean performance compared to the citric clean, which is currently used in dual damascene copper clean process. TDS (Thermal Decomposition Spectrometer) is also used to check the organic residue on copper and dielectric surface after post CMP cleaning. Few organic residues are found in the clean process by using ozone water clean followed HAL buffer HF dip. The clean performance is attributed to the HF etching effect and the organic elimination effect of ozone water clean. In addition to the above analysis, the electrical characterization is also performed to verify the actual effect the proposed clean approaches on the device cleaning process. The result shows that the proposed clean method has better leakage current, breakdown voltage, charge to breakdown performance than the citric clean. Based on all the experimental results mentioned above, our clean method is feasible and is superior to the conventional CMP clean.