Low temperature Si3N4 direct bonding

Extremely strong bonds can be formed between smooth, clean layers of Si3N4 at temperatures ranging between 90 and 300 °C. These bonds have been formed between Si3N4 layers deposited on various substrates with deposition temperatures as low as 300 °C. The bond is initially formed at room temperature and subsequently annealed at temperatures ranging between 90 and 300 °C. Thus, the materials bonded in this manner are never exposed to temperatures higher than 300 °C. This low temperature bond greatly expands the range of applications of direct bonding which had heretofore been restricted by the temperatures of 700 to 1000 °C required by conventional wafer bonding.