Post TSV etch cleaning process development using SAPS megasonic technology

In this paper, the method of space alternated phase shift (SAPS) megasonic technology is applied for post-etch (Bosch) TSV wafers cleaning process. The SAPS technology provides uniform sonic energy on each point of entire wafer by alternating phase of megasonic wave in the gap between a megasonic device and the wafer. For this study, 5×50 μm post-etch (Bosch) TSV wafers were used. Experimental verification is provided using both physical analysis and electrical test. SEM equipped with an EDX was used to detect the presence of fluoropolymer residue (i.e., CXFY) for pre- and post-cleaning TSV coupons, FIB-SEM was used to evaluate copper plating performance; TSV leakage current map and Voltage ramp dielectric breakdown (VRDB), which act as principal electrical reliability metric, were also used to assess cleans effectiveness. The test results indicate that the megasonic energy can propagate to the bottom of TSV, and the wafers undergo SAPS cleaning process exhibit obvious electrical performance enhancement comparing with those cleaned by conventional single-wafer spray approach.