Ziptronix Inc. today announced that its Direct Bond Interconnect (DBI) hybrid bonding has been implemented by Fermi National Accelerator Laboratory (Fermilab) to improve the performance of high-end 3D sensor arrays, which are used for particle detection in large-scale particle physics and x-ray imaging experiments. This is an example of three-layer DBI hybrid bonding in a 3D imaging chip, using DBI wafer-to-wafer and die-to-wafer processes.
The demonstrator, a vertically integrated x-ray photon imaging chip (VIPIC) detector, was developed by a collaboration of scientists and engineers from Fermilab, Brookhaven National Laboratory and AGH University from Poland. DBI hybrid bonding technology enables versatile new designs for pixelated radiation detectors. Fermilab and Brookhaven are national laboratories funded by the U.S. Department of Energy.
“Implementing DBI hybrid bonding enables us to design sophisticated combinations of sensors and readout electronics,” said Ron Lipton, Staff Scientist, Fermilab. “By enabling vertical signals through stacked sensor, readout and processing layers, we can design large-scale arrays that are side-edge buttable with high fill factor.”
The process flow for manufacturing the VIPIC involves using wafer-to-wafer DBI hybrid bonding to bond two ASIC wafers containing through silicon vias (TSVs). The bonded wafer pair is thinned to expose the TSVs on one side, then singulated. The singulated die stacks are then bonded to an x-ray sensor wafer using die-to-wafer DBI hybrid bonding. Subsequent thinning of the other side of the bonded wafer pair allows backside connections to the 3-layer assembly.
“This is an advanced three-layer imaging chip manufactured using DBI hybrid bonding,” said Paul Enquist, CTO, Ziptronix. “Electrical data shows that this approach achieves lower noise, higher bandwidth and higher gain due to lower capacitive load when compared with parts stacked using bumping. This increases the sensitivity of the 3D image sensors, making them ideal for use in high-end applications.”
DBI hybrid bonding is a conductor/dielectric bonding technology that includes a variety of metal/oxide/nitride combinations, uses no adhesives and is CMOS foundry compatible. It allows for stronger bonds and finer-pitch interconnect over traditional thermocompression bonding since bonding occurs at both the conductive and dielectric materials, versus just the conductor. Bonding therefore takes place over the entire surface area, eliminating the need for underfill as well as significantly reducing the overall height of the structure.