상압 플라즈마를 이용한 고속 실리콘 웨이퍼 직접접합 공정

In order to achieve a high speed and high quality silicon wafer bonding, the room-temperature direct bonding using atmospheric pressure plasma and sprayed water vapor was developed. Effects of different plasma fabrication parameters, such as flow rate of N2 gas, flow rate of CDA (clear dry air), gap between the plasma head and wafer surface, and plasma applied voltage, on plasma activation were investigated using the measurements of the contact angle.
Influences of the annealing temperature and the annealing time on bonding strength were also investigated. The bonding strength of the bonded wafers was measured using a crack opening method. The optimized condition for the highest bonding strength was an annealing temperature of 400oC and an annealing time of 2 hours. For the plasma activation conditions, the highest bonding strength was achieved at the plasma scan speed of 30 mm/sec and the number of plasma treatment of 4 times. After optimization of the plasma activation conditions and annealing conditions, the direct bonding of the silicon wafers was performed. The infrared transmission image and the cross sectional image of bonded interface indicated that there is no void and defects on the bonded wafers. The bonded wafer exhibited a bonding strength of average 2.3 J/m2.