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A STUDY ON WEAR MECHANISMS FOR ABRASIVE FREE POLISHING OF WAFERS WITH COPPER FILM
|關鍵字:||Abrasive free polishing (AFP);無磨粒化學機械拋光;benzotriazole (BTA);citric acid (CA);shear stress;苯基疊氮;檸檬酸;剪應力||出版社:||機械工程學系||摘要:||
Abrasive free polishing (AFP) is the technology for planarization and polishing of wafers without abrasives. As it can avoid surface scratch of wafer in the polishing process, AFP has become the main technology in the planarization of wafer with copper film in semiconductor fabrication. This research investigates material removal mechanisms of AFP that includes chemical corrosion, passivation in non-contact region and mechanical wear in contact region. The removal rate can be estimated based on these three mechanisms. In addition, experiments are designed and conducted as a comparison with the theoretical calculation. The results of this research lead to the following conclusions. (1) The role of mechanical wear is more important as the contact area between the wafer and pad increases at higher polishing pressure. Chemical reaction becomes more crucial as the polishing speed increases, causing the decrease of contact area between the wafer and pad. (2) The shear stress on wafer and removal rate (RR) increase with the pressure and speed. (3) Experimental results showed that polishing slurry with chemical solution assists the removal of material. RR of slurry with Citric Acid (CA) as an additive is higher than that with benzotriazole (BTA) added. (4) The thickness of passivative film, based on the calculation from RR, with BTA as an additive is higher than that with CA as an additive. It further implies that the variation of removed copper film with BTA as an additive is less than that of polishing solution with CA. Such good consistency between the theory and experimental results indicates the models of material removal in this research can provide a good estimation.
|Appears in Collections:||機械工程學系所|
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