Sacrificial wafer bonding for planarization after very deep etching

A new technique is presented that provides planarization after a very deep etching step in silicon. This offers the possibility for resist spinning and layer patterning as well as realization of bridges or cantilevers across deep holes or grooves. The sacrificial wafer bonding technique contains a wafer bond step followed by an etch back. Results of polymer bonding followed by dry etching and anodic bonding combined with KOH etching are discussed. The polymer bonding has been applied in a strain based membrane pressure sensor to pattern the strain gauges and to provide electrical connections across a deep corrugation in a thin silicon nitride membrane by metal bridges