Elimination of Defects Observed Following Patterned TiW-Au Metal Formation

Jason Fender and Terry Daly 
Freescale Semiconductor Inc. 2100 E. Elliot Rd., Tempe, AZ  85284
Email: jason.fender@freescale.com, terry-daly@freescale.com 
Phone:480-413-3521, 480-413-5029

For this work a physical vapor deposited TiW-Au metallization is used as the electrical continuity layer for subsequent patterned  electroplating of metal features on GaAs devices.  Once the pattern is plated and the Au seed has been removed via reverse plating, plasma etch is used to remove the field area TiW.  Following plasma etch, defects were observed across the wafer surface.  Auger electron spectroscopy (AES) revealed that the defects were Au particles.  Several methods of eliminating the Au particles were identified including, 1) use of vacuum break during the TiW-Au deposition, 2) 02 plasma ash prior to reverse plate, 3) a dual-iteration reverse plate process, and 4) a Au wet etch following reverse plate.  The dual-iteration reverse plating process was determined as the best alternative. 

Keywords:  defects, kTiW, Au, Au electroplating, plasma etch

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