Three-dimensional wafer stacking using Cu–Cu bonding for simultaneous formation of electrical, mechanical, and hermetic bonds
Tan, Chuan Seng
Li, Hong Yu
Date of Issue2012
School of Electrical and Electronic Engineering
Wafer-on-wafer stacking is demonstrated successfully using bumpless Cu-Cu bonding for the simultaneous formation of electrical connection, mechanical support, and hermetic frame for 3-D IC application. The ohmic behavior of the Cu-Cu bond is verified. A daisy chain of at least 44 000 contacts at a 15-μm pitch is connected successfully and sustains thermal cycling. Postbonding delamination is found to be strongly affected by the wafer curvature and bond strength. The Cu-Cu hermetic seal ring shows a helium leak rate more than ten times lower than the reject limit (5 × 10-8 atm · cm/s based on MIL-STD-883E standard) without underfill. This provides a robust IC-to-IC connection density of 4.4 × 105 cm-2, suitable for future wafer-level 3-D integration.
DRNTU::Engineering::Electrical and electronic engineering
IEEE transactions on device and materials reliability
© 2012 IEEE.