潔淨室無機污染物之採樣及晶圓表面吸附沈積行為探討

Abstract

半導體產業積體電路製造技術快速發展，傳統針對微粒污染控制所設計之潔淨室將無法符合氣態分子污染物之潔淨需求，其中無機氣態分子污染物質(Inorganic airborne molecular contaminants)一旦沈積吸附於晶圓表面，將導致元件缺陷與製程良率下降。 本研究提出無塵室無機分子污染物質最佳採樣方式，並使用擴散固氣採樣器(DDS)完成黃光區及蝕刻區無機氣態及固態污染物濃度分析，以了解常見無機分子污染物之種類、濃度大小與其潛在污染來源；並建立不同曝露時間之晶圓表面無機污染物吸附沉積動力模式，預測環境中可允許濃度或最大曝露時間之恕限值。 由無機污染物採樣技術研究結果顯示，DDS和吸收瓶皆可有效應用於無塵室無機污染物採樣，其中DDS採集SO2氣體及SO42-微粒污染物濃度合計後，其和吸收瓶採集SO42-濃度間具有高相關性(R2=0.99)。黃光區及蝕刻區主要氣體污染物為NH3及HF氣體，主要酸鹼性微粒為Na+、NH4+、Cl- 及SO42-；黃光區及蝕刻區酸鹼性微粒質量濃度分別佔細微粒(<2.5µm)質量濃度56.1%及62.4%。晶圓表面無機污染物沉降潛勢分析結果顯示，晶圓表面斑點污染物質呈現明顯半中空孔洞(Semi-void)圓形形狀，斑點污染物尺寸>100×100 µm2，斑點污染源為有機、無機氣態分子污染物及微粒組成。無機污染物沉降於晶圓表面潛勢能力大於有機污染物質，其中K+ 離子具有最大沉降潛勢。晶圓曝露於無機污染物環境下，經數秒的時間，即可能造成晶圓元件污染與陷缺。

The deposition of inorganic airborne molecular contaminants (AMCs) on wafer surfaces will result in deterioration on device performance. In this study, three sampling devices which have been used in the cleanroom samling of AMCs are compared and optimal sampling conditions are suggested. The inorganic gas and particulate compounds at the photo and etch areas are evaluated by a diffusion denuder sampler (DDS) and the deposition kinetics of inorganic compounds onto wafer surface are also developed to predict the allowable wafer exposure durations. The results reveal that the impinger and the DDS are proved to be suitable for sampling inorganic AMCs. The SO42- collected by the impinger and the sum of SO2 gas and SO42- particles taken by the DDS show very good agreement (R2=0.99). At the photo and etch areas, the major inorganic gases are NH3 and HF while the major particulate species are Na+, NH4+, Cl- and SO42-. The inorganic species in the PM2.5 mass account for 56.1% and 62.4% of the particulate mass at the photo and etch areas, respectively. The results of surface deposition of ionic contaminants on silicon wafers show that the morphology of hazing contaminants is in spherical shape with semi-void and >100×100 µm2 size. The compounds causing wafer hazing might be from the organic, inorganic AMCs and particles as well. The inorganic AMCs possess relatively higher sticking potential as compared to that of organic AMCs, among which the K+ ions have the greatest adsorption rate. It indicates that AMCs could incur damage to silicon wafer even under only a few seconds of exposure to inorganic compounds.