TSV (through silicon via) interconnection on wafer-on-a-wafer (WOW) with MEMS technology

The fabrication of WOW (wafer-on-a-wafer) with MEMS technology has been developed. A wafer was thinned and stacked on a base wafer. After the TSVs were patterned on the thinned wafer, they were filled by Cu for interconnection. The wafers were bonded with benzocylcobutene (BCB, CYCLOTENE^TM) as an adhesive material. The BCB layer was also acted as a dielectric layer between top and bottom silicon wafers. The TSVs were created by DRIE (deep reactive ion etching) and filled by Cu electroplating. This paper describes that thinned Si wafers down to 20 mum were stacked on a base wafer with TSVs interconnection filled by Cu. The thinned wafers were stacked up to seven. The electrical characteristics were measured by daisy-pattern including 243 TSVs filled by Cu and the stress simulation for TSV was also shown.