Hybrid Bonding permanently bonds the surfaces of two wafers, dies, and/or chiplets. It is called “hybrid” because it combines two distinct types of bonds at the interface: a dielectric-to-dielectric covalent bond and a metal-to-metal fusion bond. The most commonly used process, DBI® (direct bond interconnect), was pioneered by Ziptronix in 2005 and is now owned by Adeia and licensed to several companies, including NHanced.
DBI hybrid bonding is today’s best technology for 2.5D and 3D advanced packaging. It creates a sturdy, seamless bond and enables very fine-grained interconnect. The process is performed in a cleanroom with semiconductor fab processes. The bonded parts behave like a single circuit; no ESD structures are needed.
1) Build metal interconnect into the surfaces to be bonded
2) Recess the metal slightly below the surface of the dielectric material
3) Polish dielectric surfaces atomically smooth
4) Activate dielectric surfaces to open oxygen bonds
5) Align the surfaces and bring them together, forming a van der Waals bond
6) Apply heat to form covalent dielectric bond
7) Increase heat to expand the metal under pressure, forming a fusion bond
This image shows two copper TSVs bonded end-to-end. The result is a monolithic copper TSV with twice the depth. This technique can create TSVs with very high aspect ratios.