潔淨室氯離子微污染物造成有圖晶圓之金屬線路腐蝕探討

Abstract

潔淨室環境中微量的Cl- 會造成晶圓金屬線路腐蝕缺陷(Metal Corrosion)，導致元件缺陷與製程良率下降；本研究提出以潔淨室有圖晶圓進行微污染採樣，設計不同型式的氯離子微污染控制環境，並配合使用離子移動式光譜儀以及吸收瓶採樣+離子層析儀分析方法，研究潔淨室氯離子的環境背景濃度，以及有圖晶圓暴露於微污染控制環境，研究內容包括發生金屬線路腐蝕的敏感度、再現性、最大允許環境曝露濃度之恕限值等，進而依據實驗結果來研擬實廠對於氯離子微污染之防範策略。 由潔淨室氯離子背景濃度以及微污染控制環境研究結果顯示，IMS可有效應用於無塵室氯離子監測，和吸收瓶之同步量測差異分析呈現高相關性(R2=0.9933)；本研究創新設計之無塵布微污染環境，其濃度誤差為12%~17%，與滲透管微污染環境之HCl濃度控制能力相當；本研究設計之有圖晶圓的確可有效偵知金屬線路腐蝕缺陷，並且由表面缺陷分析儀分析之缺陷數量與暴露濃度正相關，由能量散射光譜儀分析缺陷的成分也均有發現氯元素的成分，以上的缺陷分析之再現性均為 100%，有三明治結構的Al-0.5%Cu 8吋有圖晶圓相較於Al-1%Si-0.5%Cu 6吋有圖晶圓有較佳的抗腐蝕能力，TiN障礙層也較TiW障礙層具有更佳的抗腐蝕能力；最後，依據本研究建立金屬線路腐蝕之可容許曝露Cl- 濃度為2ppbv，此可容許曝露Cl- 濃度並可作為實廠運作之參考建議值。

Chloride ions (Cl-) induce metal corrosion of integrated circuits and cause wafer scrap events in the clean room environment. In this study, pattern wafers were designed to monitor critical Cl- concentration which leads to metal corrosion effects in a simulated airborne molecular contamination (AMC) mini-environment, meanwhile, the HCl concentrations in the mini-environment and the real fab were monitored by a real-time Ion Mobility Spectrometer (IMS) and impinge+IC. The results help to understand the sensitivity, corrosion occurrence, and recommended exposure limit and preventive action plan. The results indicate that the IMS can be used for HCl AMC monitoring, and show very good agreement (R2=0.9933) with the impinger+IC method. It also proved that the innovative “clean wiper” mini-environment can serve as a stable Cl- simulated source, which can control the simulation within 12%~17% error in ppbv levels. The designed pattern wafer exposure tests can be an effective method to monitor metal corrosion, and the corrosion defects’ reproducibility is 100%. Furthermore the Al-0.5%Cu pattern wafer with “sandwich” structure provided better anti-corrosion capability than the Al-1%Si-0.5%Cu pattern wafer. The TiN barrier layer also provide better anti-corrosion capability than TiW barrier layer. Above all, this study concludes the suggested exposure concentration of Cl- at 2 ppbv in a real fab application.