Low-temperature rough-surface wafer bonding with aluminum nitride ceramics implemented by capillary and oxidation actions

Aluminum nitride (AlN) is a ceramic material with excellent dielectric and thermal properties, and it is used in the microelectron and energy fields. Despite polishing, the roughness (rms >10 nm) of AlN wafers fabricated by sintering fails to meet the surface requirements (rms <0.5 nm) for direct wafer bonding. However, rough-surface wafer bonding of paired AlN and AlN can be achieved with the following procedure: (1) rough surfaces are activated by oxygen plasma to introduce strong capillary action, (2) reactions of AlN and bonding species (OH) are promoted by clamping during storage and annealing and (3) low-temperature annealing (<150 degrees C) joins the two surfaces of AlN/AlN by synthesizing Al2O3 at the bonding interface. TEM and XPS results show that a transition layer exists between bonding surfaces wherein the concentration of nitrogen decreases while that of oxygen significantly increases.

Automated summary

Aluminum nitride is a ceramic material that is widely used in microelectronics and energy fields due to its excellent dielectric and thermal properties. This study demonstrates a procedure for achieving rough-surface wafer bonding of aluminum nitride by activating the surfaces, promoting reactions between aluminum nitride and bonding species, and joining the surfaces through low-temperature annealing.