Increasing bonded wafer yield by acoustic micro imaging (AMI)

A major defect concern in fusion-bonded wafer pairs, as well as in wafers b onded by other methods, is the presence of a void or micro-voids between th e two wafers. Although a void may be very small in area and extremely thin, it can still have devastating impact on device performance. Among companie s involved in bonding wafers, usually for MEMS or analogue device applicati ons, the tolerance for such voids is zero.