Low-Temperature Cu-Cu Direct Bonding Using Pillar-Concave Structure in Advanced 3-D Heterogeneous Integration

Abstract

Low-temperature Cu-Cu bonding utilizing pillar and concave on silicon substrate with and without polymer layer is successfully implemented at 200 degrees C under atmospheric pressure. Finite-element method (FEM) simulations on stress and deformation generated during bonding process are also presented in order to discuss their influence on bonding result of several pillar diameters and of concave sidewall angles originating from the manufacturing process. The alteration of parameters in FEM simulations would also be investigated to enhance the bonding outcome. The parameters include the diameter of pillar, the sidewall angle of concave, the shape of the concave opening, the addition of extra polymer layer under Cu concave layer, the bonding temperature, and the pitch of the pillar-concave structure. The implementation of Cu-Cu bonding using pillar-concave structure could have a prospective effect on existing packaging methods in semiconductor industry with benefits of applicability to various sorts of substrates and low bonding temperature.