This is part of a series of short interviews, based on face-to-face meetings at SEMICON West 2013.
Sitting down with EV Group execs to talk about the company’s latest achievements and contributions to the 3D IC cause has become an annual SEMICON West tradition. In fact, I’ve probably spent more time with this team than any other in the 3D space because I’ve visited the headquarters in Schaerding twice, and the North American headquarters in Tempe AZ on a fairly regular basis, since I’m based in Phoenix. You’d think by now we’d run out of new things to discuss, but nothing could be further from the truth. There’s always something going on there.
This year, our discussion focused on the details of EVG’s latest technology innovations being showcased at SEMICON West, including the introduction of its next generation of its EVG®40NT automated measurement system, which is designed to work in concert with the company’s GEMINI® FB fusion wafer bonding system to support the manufacture of next-generation 3D-integrated CMOS image sensors. Additionally, the company introduced its LowTemp™ debonding platform, which features three high-volume-production room-temperature debonding process types and is supported by a supply chain of seven qualified adhesive suppliers to enable greater manufacturing flexibility.
Marcus Wimplinger, Director Business Unit Technology Development and IP at EV Group, explained the latest update to the 40NT system, which involves software integration between the measurement system and the bonder to provide 100% alignment accuracy inspection of fusion-bonded wavers.
Here’s how it works: wafers are fusion-bonded in the bonder, which is placed next to the measurement system. Alignment is checked before passing the wafers on to the final batch anneal step, allowing for re-work if necessary.
According to Wimplinger, the target application is backside illuminated (BSI) CMOS image sensors, which uses via-last technology, and doesn’t require a temporary bond/debond (TB/DB) step because thinning takes place after the permanent bond and anneal. Since we’re dealing with full thickness wafers, if they are misaligned, they can be separated, rebonded and rechecked. After annealing, one of the wafers is thinned, which is why there’s no need for TB/DB.
BSI image sensor technology is a true 3D technology, because the photodiode is on the top wafer, and signal processing is on the lower wafer. It uses next-generation via last processes, which results in higher density vias, but only around the perimeter of the image sensor chip. The interconnect between the wafers is a face-to-face bond without TSVs – Ziptronix Direct Bond Interconnect (DBI) is one way to accomplish this, said Wimplinger. The TSVs around the edge connect the images sensor to the outside world.
We also talked about EVG’s latest temporary bond/debond work focused on expanding options for room temperature debonding, which has become the latest TB/DB Holy Grail. The company now offers three process solutions: ZoneBond, UV laser debond, and a new multi-layer debond process. Seven adhesive suppliers qualified for this family of debonding, including Shin Etsu, JSR, Hitachi Dupont, Brewer Science, Dow Corning, and others.
Why so many options? “There’s no solution that fits all,” explained Hermann Waltl, executive sales and customer support director at EV Group. “There are different requirements based on topography, cost of ownership, etc. We consult with the customer to determine the requirements and make recommendations based on our product family.” He added that there are different process modules and different adhesives suited to individual requirements. The idea is to leverage these across the product families.
In addition to this, EVG also announced a three-year common lab agreement with Leti to optimize temporary- and permanent-bonding technologies related to 3D TSV integration and all direct bonding heterostructures. The lab focuses on hardware, software and process development including a new covalent bonding process, ComBond, that has a new equipment platform where handling is done in a high vacuum atmosphere, explained Waltl. While this process initially targets MEMS and compound semiconductor applications, Waltl says its also compelling for integrating Si photonics in 3D systems, and could put EVG “ahead of the pack” in this area.
So like I said – at EVG, there’s never a dull moment. ~ F.v.T.