An In-Depth Look at Leti’s Common Lab with SPTS

When a research institute is evaluating different options for technology partnerships, what tips the scales in favor of one supplier over another? In the case of the recently announced common lab agreement between Leti and SPP Technology Process Systems (SPTS) to further develop processes for high aspect ratio TSVs, it was a matter of finding the ideal mix of key elements that included an established history, a strong technology and equipment portfolio, a willingness to adapt and work together, and the added bonus of a powerhouse parent company.

“It’s an attractive proposition for us.” explained Mark Scannell, program manager, 3D integration at Leti. “We’d previously worked with STS and liked its equipment and technology. But Leti develops processes that are used by the entire industry. Larger industry players prefer to work with larger players.  With SPP’s (Sumitomo Precision Products) backing, we have the technologies we’ve always liked with the weight of a larger company behind them.”

It helped to have a whole family of processes that work together. For some specific developments Leti had already decided to go with STS or Aviza based on their respective tools and processes before the merger happened. “The greater entity of SPTS has greater development capacity that goes beyond the original capacities of each company,” notes Scannell. “We’re very happy to work with a company willing to go further in development. When we pull all the original components together, the sum is greater than the parts.”

The common lab agreement was signed by Dr. Laurent Malier, CEO of Leti and Dr. Susumu Kaminaga, President of SPP and Chairman of SPTS at the LetiDay event in Tokyo, Oct. 6th.

According to Scannell, the goal of the common lab is to focus on advanced copper TSVs, including via mid and via last processes. (Via first is only viable with polysilicon due to the high temperature processes).  While the main focus of the work is development of TSV etch and dry deposition processes (PVD and CVD) for isolation/barrier/seed to achieve desired cost, temperature, and aspect ratio; the Holy Grail is to be able to work with a thick enough wafer to eliminate the handling problem. While Scannell emphatically stressed that the project’s objective isn’t to achieve a specific aspect ratio, he says for some applications he’d like to be able to handle wafers without carriers, which requires keeping  the wafer thick enough so its sound for regular handling; around 250µm (50:1 AR) should do it.

All the work will be done on 300mm tools, says Scannell, and will involved adapting and improving existing ideas while also adding some new approaches in research. Coming from a MEMS background, SPTS is open to looking at things from a not-yet-standardized perspective, which is a bonus. So far, Leti has taken delivery of a Pegasus etch tool and a multi-chamber CVD tool.  The PVD tool will round out the set in December.  The tools installed are the “most modern” the companies have; some with the latest chambers available and some even with “Alpha” chambers.  Scannell explained that the “latest” chambers will be used to improve or optimize existing processes while the Alpha chambers will be used to develop new processes and adapt hardware to suit.

“Leti has a lot of ideas with deposition and haven’t been able to carry them out,” he explained. “SPTS is very open to making hardware adaptations to suit new processes. For us, it’s very nice to work with someone of that philosophy and mentality.”

While the official start of the agreement is January 1st, work is already underway, says Scannell.  Next in store for Leti is the official inauguration of the 300mm tool line, which will take place on January 18th; looking forward hearing more about it.