Fluorine Residue Reduction in Plasma Dicing

This paper showcases an innovative characterization in reducing fluorine residue in the plasma dicing process applied to RFID application wafers. The advantages of plasma dicing include a reduction in sawlane width, leading to an increase in Die Counts per Wafer (DPW) and enhanced die strength. This is achieved through a chemical etching process that separates the silicon wafer dies. The requirement for small die sizes in RFID applications results in a high DPW, exceeding 300,000 on a single wafer, and a narrower sawlane of less than 10um. Consequently, a plasma dicing solution becomes essential for RFID wafers. The Reactive Ion Etching (RIE) plasma dicing process, also known in the industry as Bosch Process is a high aspect ratio plasma etching process. This process provides a protective fluorocarbon layer on the sidewall for an anisotropic fluorine-based etching process. However, a challenge arises as the fluorinated gas used in plasma dicing can induce contamination on the sidewall or surface of the wafer. This contamination may affect the adhesion between the die and the backgrind tape. Particularly for small RFID dies on the wafer edge that need to adhere to the lamination tape post-backgrinding, the adhesion force can be compromised when fluorine contamination occurs at the wafer edge. This study was conducted to creatively optimize the RIE polymerization process and the fluorine residue cleaning process post-plasma dicing. The results of the study were analyzed using SEM and XPS tools to determine the level of fluorine residue. The analysis indicates a significant reduction in fluorinated material, demonstrating a positive outcome, hence making this study a success.