Pre-bonding method using self-alignment effect for multichip packaging

An efficient C2C/C2W oxide bonding technique using self-alignment effect of a pair of hydrophilic chip surfaces, which are activated by plasma, is applied to 3D stacking of multichip packaging in this work. Self-alignment and pre-bonding technique can provide high-speed bonding process and high-precision chip alignment accuracy simultaneously without high-precision chip manipulator. Through experiments, we could acquire high hydrophilic silicon surfaces using plasma surface activation and measured position errors and rotational error of aligned chips is smaller than 5 ¿m and 0.04 degrees respectively because of self-alignment effect between hydrophilic surfaces of chips. In addition, temporary bonding is formed successfully by secondary bonding between silanol groups (Si-OH) on the hydrophilic silicon chip surfaces when the DI water is evaporated by heating, which prevents contamination of bonding surface and helps of manipulation of multi-stacked chips easily.