The FAST route to the Top of the TSV Mountain
While on a recent visit to UnitySC in Grenoble, France, I spent some time visiting with a semiconductor process equipment company that shares the same cleanroom space: KOBUS. Named for a genus of the African antelope for its elegance and speed, the company has developed a unique approach to deposition for through silicon via (TSV) metallization processes (barrier, seed and fill) combining the performances expected from atomic layer deposition (ALD) with the speed of chemical vapor deposition (CVD). They call it fast atomic sequential technology (FAST).
Like UnitySC, Kobus was formed as a result of Fogale Group’s acquisition of Altatech, comprising its former CVD division. Although I’ve written about the company and FAST technology previously, I was eager to pay a visit and learn more from CEO Julien Vitiello, who started developing this technology under the Altatech brand, and is excited to see it through as KOBUS, with solutions for SiO2 liners, TiN barrier, and Cu seed for the next generation of high aspect ratio TSVs. Future applications will expand into other advanced packaging areas, as well as LED and microdisplay markets.
This FAST chamber is the result of ten years of R&D, noted Vitiello. It is a hybrid module that combines the pulsing capabilities of ALD inside a CVD reactor design to get the best of both worlds, delivering ALD performance levels for thick and conformal deposition (Figure 2). The added value is that the cost-of-ownership is the same range as competitor’s CVD tools. The tool is ready to be installed in volume manufacturing environment.
“Since 2007, as Altatech we put ten platforms and 20 chambers that ran the previous generation of FAST into customer locations. We worked in collaboration with these customers to fine tune the process development and consolidate the new chamber,” noted Vitiello. “What we are releasing as KOBUS is the top of the mountain for us.”
Vitiello explained that generally, performing a conformal ALD process takes a long time. CVD is a chemical approach that is faster but generally results in a less conformal film. The idea was to combine the capabilities to unleash breakthroughs in performance using standard semiconductor technology.
“In 2015 our focus was on making specialty equipment and demonstrating our performance for the TSV market,” said Vitiello. “Now we are focusing on where we are different. FAST technology is our differentiator; nobody else has what we have. “
They are working with some of the big R&D centers to demonstrate the application side to the customer, as well as with TSV makers to support increased aspect ratios or decreased diameters of next generation TSVs. For standard TSV makers, the key driver is that FAST allows them to lower integration cost, using the same materials and pushing the technology further. The FAST solution can already help reduce integration cost, vs using physical vapor deposition (PVD) and CVD.
“Using a PVD tool for advanced packaging processes becomes complex and costly. This why people are facing a wall with PVD. The chamber isn’t designed for TSV processes,” said Vitiello.
The FAST chamber, on the other hand, can perform barrier, isolation and seed layer processes using a cluster tool, thanks to its open process capability.
While it wasn’t designed for fill processes, Vitiello says it can handle it, but it only makes sense for certain TSV schemes, depending on the diameter and depth of the TSV.
The tool’s flexibility creates opportunity and opens up potential, which is what the advanced packaging market is looking for, he added. They can do more with this toolset than with others. While some processes will be more advanced than needed, it still eliminates the need for multiple tools.
For those following a TSV roadmap that is blocked because of the incumbent technology, which is limited and expensive in terms of integration, FAST process tools can be adapted to customer needs, thanks to an expanded process window. This allows the designer more flexibility in TSV design.
“If you can make the TSV you want, what will that do for your product? What would your dream TSV be if you aren’t limited by the tools?” said Vitiello. “That’s where Kobus FAST technology comes in.”
As the visit to KOBUS coincided with my birthday, Vitiello graciously presented me with a bottle of wine from his family’s vineyard. I promised I wouldn’t drink it until I finished this post…just in time for the weekend! Cheers, everybody! ~ FvT