This whole week had been going so smoothly, I should have known I was due at least one mishap along the way. It happened on the beginning of Day 5. My challenge was to navigate the Swiss/French train system and get myself from Geneva to Annecy, France, for my morning visit with Nicolas Launay and tour of the Tegal France R&D facility. To my knowledge, there were only two morning trains and I was planning to take the second one, which left Geneva at 8:05 and arrived in Annecy at 9:25. I arrived at the Geneva station in plenty of time to buy my ticket and have a coffee before boarding, or so I thought. Then I was told by the ticket agent that I was at the wrong station. The right one was 30 minutes away by taxi, and I had about 25 minutes to get there before the train would leave. Without a back-up plan, I decided to give it a shot. Thank goodness my taxi driver knew the back way, and the ticket agent was wrong. I arrived in plenty of time, purchased my ticket en route, and arrived on time. So it was with great relief to see Launay holding the Tegal sign. He gallantly took matters from there, deciding that my trip back would be easier if he just drove me all the way back to Geneva. The day just got better from there.
Formerly Alcatel Micromachining, Tegal France’s facility is located in the picturesque region of the Rhone Alps, not far from Chamonix. (It’s hard to believe high tech happens tucked in these idyllic locations, but I have the photos to prove it.) This division of the globally-positioned Tegal Corp. serves as the heart of the company’s R&D for MEMS and 3D etch applications. It’s proximity to and close relationship with Leti is part of the reason why, as the government of France’s generosity when it comes to funding technology projects. Launay mentioned that Tegal is involved in several such projects at the moment, but couldn’t quite share the details yet.
In general, Tegal France is charged with leveraging its predecessor’s achievements in etching tools for the 200mm MEMS and compound semiconductor markets into the rapidly emerging 3D IC market, and specifically TSV etching processes. As part of this effort, the company introduced its ProNova 200mm tool into the market in July, 2009. The next-generation tool development is already in progress at the Annecy facility. I was honored to learn that I’m the first journalist to get a live tour of the R&D lab.
As with other opportunities this week, seeing the real thing in action really helped to complete the picture in my mind about how TSVs are formed. At Leti, we had seen a fully installed AMM tool from the front. But all the inner workings are enclosed in a self-contained environment. Here, I saw the process module in both prototype and final production versions, as well as the final cluster assembled – in this case with one module that used the standard ICP plasma source, and the other with the new ProNova plasma source in order to perform the comparison processes.
I was also fortunate to finally get a lesson in how plasma etch works to create TSVs. According to R&D project manager, Pierrick Godinat, the advantage of etching with plasma is that you can achieve whatever shape you want. Photoresist acts as a mask to preserve the silicon you want to keep, and allows for smaller design features. Launay explained that the concentration of fluorine used in the process controls the depth of the via. He also explained that while etch rate is important to increasing throughput, increased scalloping due to the way the flourine silcon etches away the silcon in x and y directions as well as the z can be an issue as it makes conformal deposition of insulation, barrier and seed layers difficult using traditional dry process. (At this point, it occurs to me that Alchimer’s AquiVia approach seems a likely solution to this issue).
Over a lovely lunch in a nearby restaurant and the ride back to Geneva, Launay explains more about what it’s like work in this industry in this particular part of the world. It occurs to me that 4 of the 4 companies I just visited each address one step of the 3D TSV process flow: Soitec for W2W bonding and thinning with it’s Smart Stacking technology, SET for C2W die bonding processes, Tegal France for via etch, Alchimer for insulation/barrier/seed layer; and Replisaurus for via fill. With the research and development resources available through partnerships nearby at Leti, and ST Microelectronics investing in bringing these technologies to market, this region of France has really become a hotbed of microelectronics.