Roy, S. C., Guan, C. G., Venkataraman, N., Lee, W., & Singh, N. (2023, December 5). Cu and barrier CMP process development with fine 1μm Cu bond pad and 2.5 μm pitch for Wafer-to-wafer Hybrid Bonding. 2023 IEEE 25th Electronics Packaging Technology Conference (EPTC). https://doi.org/10.1109/eptc59621.2023.10457780
Abstract:
Fine pitch hybrid bonding is evolving as a vital
advanced permanent bonding in 3D IC technology for its low cost and providing shorter global
interconnect length. Chemical mechanical planarization (CMP) is a critical process step for
realizing uniform Cu dishing control all over the wafer for successful W2W hybrid bonding. In this
paper, we have investigated the effect of various CMP conditions using a three- step CMP process,
on Cu dishing, intra-die oxide planarity, and surface roughness and have attempted to understand
the dishing control mechanism for our developed CMP process. Atomic force microscopy has been used
to characterize the dishing and non-uniformity of the wafers. We have demonstrated controlled
dishing <3 nm, intra-die oxide planarity <0.6 nm, and Cu/oxide surface roughness <0.3 nm for 1 µm
Cu bond pad size and fine pitch ~2.5µm. Our analysis indicates that the balanced combination
of HPP and LPP with polish time control for Cu and barrier polishing helps to control the Cu pad
dishing and achieve high uniformity all over the wafer. Our study outlines a way for the
optimization of Cu and barrier CMP processes for
fine-pitch Cu pads for hybrid bonding applications.
License type:
Publisher Copyright
Funding Info:
This research / project is supported by the GlobalFoundries Singapore - Stacked BSI Sensor Project
Grant Reference no. : NA