Bond strength of conductive Si-Si fusion bonded seals

High temperature silicon direct (fusion) wafer bonding is a process with many application areas. Depending on the application, perfect insulation or zero resistance across the bonded interface is desired, but high bond strength is needed in both cases. Recently, we have presented a hydrophilic bonding process which resulted in ohmic behaviour and negligible electrical resistance of the bonding interface. This paper is an investigation of the bond strength of conductive hydrophilic high-temperature silicon direct wafer bonds. Dicing yield and pull test measurements have been performed. Bonding frames of widths of 100, 200, and 400 μm were fabricated. The measured resistance of chips from boron implanted wafers was 0.35-0.38 Ω, and the resistance of chips from three non-implanted wafers was below 0.68 Ω. The dicing yield was above 89 % for frame widths of 200 μm or wider. Bond strengths of 10.5-13.5 MPa were measured on frames of 400 μm width. There was no significant difference in bond strength between implanted wafers, non-implanted wafers, and wafers with an intentional 60 nm thick SiO₂ at the bond interface. The results show that directly bonded silicon bond frames of 200 and 400 μm widths can be conductive and show ohmic behavior while they also have sufficient yield and bond strength for application as device seals in industrial products.