New applications of R.F.-sputtered glass films as protection and bonding layers in silicon micromachining

Different r.f-sputtered borosilicate glass films are characterized. Layers sputtered in 100% Ar and annealed in N2 at 550 °C for 3.5 h are found to be best applicable as protection layers in anisotropic etching of Si in KOH solutions and as bonding layers in silicon micromachining. For in situ inspection of the progress of the silicon-to-silicon anodic bonding process using sputtered glass as intermediate layer, an infrared inspection equipment is built. Also, an alternative evaluation method of the bonding quality is presented. Bonding experiments with sputtered glass layer thicknesses ranging from 20 to 1000 nm show corresponding progress of the bonding process. The yield does not seem to depend on the thickness of the borosilicate layer. Furthermore, new possible applications are demonstrated, in which the sputtered glass layer acts both as an etch stop and bonding layer.