Technical Tidbits from IWLPC and MSEC 2017

Technical Tidbits from IWLPC and MSEC 2017

It’s been a busy few weeks for me as I attended both the International Wafer Level Packaging Conference (IWLPC), October 24-26, 2017 at the DoubleTree in San Jose and SEMI-MSIG’s MEMS and Sensors Executive Congress, October 31-Nov. 2, at the Hayes Mansion in San Jose. In addition to taking in some great keynotes and technical sessions, I had the opportunity to meet with several companies to find out what’s new.

TSV Sightings by SystemPlus Consulting
Through-silicon vias (TSVs) are starting to show up all over the place, particularly in MEMS applications, to SystemPlus Consulting’s Romain Fraux. While TSVs still make up only 8% of interconnects used in advanced wafer level packages (12% use bumps, many still use wire bonds), its appearance in Apple’s fingerprint sensor resulted in the production of 150K 300mm TSV wafers. Fraux reports this is the highest volume production of TSV middle and is manufactured by TSMC. MCube is also using TSMC’s via middle. There are several companies using a TSV last approach. One example is, HuaTian, which is using TSVs its system-in-package (SiP) module for fingerprint cards under glass, based on Tessera’s MVP technology. Although it’s not the same kind of TSV being used by Apple, it allows for the removal of wire bonding, noted Fraux.

Xperi’s Update on Die-to-Wafer Hybrid Bonding
I’ve seen numerous wafer-to-wafer direct bond interconnect (DBI®) presentations at IWLPC, IMAPS, MSEC, ECTC, the MEMS and 3D Summits, and all the other acronym-based conferences that take place throughout the year. So it was with interest that I listened to Guillian Gau presenting Xperi’s recent development work adapting DBI for die-to-wafer processes at IWLPC 2017.

Xperi has demonstrated 3D die-to-wafer stacking in a 4-die stack. Underfill and solder balls have been eliminated, and thermocompression bonding is replaced by DBI. Both sides of the die have a bondable surface. Gau said they have achieved success bonding a multilayer stack without TSVs. The next step is to use die with TSVs.

The greatest challenge, according to Gau, was keeping the wafer die surface clean during the dicing process. Wafer-to-wafer is easier because it’s easier to keep clean, she explained. Dicing is a dirty process because it generates particles. To overcome this, Xperi performs a special wafer coating step prior to dicing to keep the particles from sticking. “Both stealth and saw dicing can meet the bonding requirements,” she said. “We want it to work with the existing infrastructure.”

Throughput is another important consideration. The bonding process is simple: just activate the dielectric surface with plasma, and drop the die in place. The demonstration work was performed on both a Toray die bonder and Datacon flip chip bonder to compare different alignment accuracy. The Toray tool placed 2400 die per hour at ±2µm. The Datacon flip chip bonder placed 6000 dies per hour ±7µm.  In comparison, traditional TCB achieves throughputs of 90-379 die per hour, depending upon whether non-conductive film or non-conductive paste is used.

Gao reported that they had good results with four die stacks using DBI, with good joints and no bond line. The next step is to build it using TSV die in a high-volume manufacturing environment.

UnitySC Opens Software Development Lab in Austin
After reading the announcement of UnitySC’s opening of its new software development lab and customer support demo lab, I caught up with the Philippe Gastaldo, Product and R&D Director, UnitySC, at IWLPC, who filled me in on the details.

According to Gastaldo, the Grenoble-based advanced process control company has experienced rapid growth, with over 130 metrology and inspection systems for heterogeneous integration in the field, and more than 70 employees. He explained that it’s the software, not the hardware, that is the key element to UnitySC’s process control solutions. “The user interface is particularly important for high volume manufacturing,” he explained.” We need to be sure about reliability, user-friendliness, and tool standards. We don’t want to be weak in the software space.” Because of this, 75% of the employees work on software development, and expanding that area is critical for company growth.

In addition to innovative software that supports the complete UnitySC product line, the team will work on numerous other projects including proprietary data stream analysis to yield precise measurements, surface mapping, and defect categorization. Developing next-generation automatic defect classification software that improves definition methodologies and defect identification is also on the list, as well as data visualization software that facilitates improved data and product analysis. The US office will also serve as a customer support demo lab for its customers that work on US defense applications. Gastaldo said bringing this demo lab close to US customers will allow for increased capacity and reduced cycle time.

So why did they decide to locate the center in the US, and specifically, Austin? Austin, TX offered many things that Europe didn’t: Proximity to other high-tech businesses, a highly-educated and established base of software developers with semiconductor knowledge, and attractive cost of living and quality of life for the workers. Gastaldo said that the more rapid hiring process in the US allowed unity to hire four employees in the first month, and by three months had on boarded an eager, experienced, twelve-person workforce.

Lam Research Completes Coventor Acquisition
Back in August, semiconductor process tool giant, Lam Research, completed its acquisition of Coventor, a provider of simulation and modeling solutions for semiconductor and MEMS processes. Like the last spring’s acquisition of Mentor by Siemens, this news had me scratching my head a bit. As far as I know, big tool companies usually gobble up small ones, and the same goes for big design tool companies. This is a new twist in industry consolidation, so I was eager to get more details. I had my chance at MSEC 2017, where I sat down with Coventor’s Steve Breit, and Lam’s MEMS team, Michelle Bourke, and David Haynes to learn more.

The explained the arrangement like this: A subsidiary of Lam Research, Coventor will continue to operate as a separate business and will continue to service its clients, including other equipment manufacturers. The purpose of the acquisition was mainly to allow for better collaboration where both Lam and Coventor have identified synergy with customers. Together, they increase their value proposition by enabling three-way alliances.

Breit explained that Coventor’s vision is to provide smarter process control with virtual fabrication through simulation and modeling. The company’s unique proposition is 3D virtual fabrication that captures the whole process stack. Working with Lam provides us new opportunities in design for manufacturing, allowing us to consider a devices’ manufacturability in a more sophisticated manner that’s never been done before, he explained.

Particularly for Lam’s MEMS business, Haynes says this opens doors to more fabless and fab-lite manufacturing partnerships. “MEMS one-device-one-process approach hasn’t made it easy to move products quickly into the foundry,” he said. This type of consolidation reflects the increased level of maturity in the MEMS industry and need for standardization.

Access to Coventor tools allows Lam to offer customers integrated modeling with process knowledge to help improve cycle time, device performance, and reduce cost, explained Bourke. For example, to prove hardware performance, its necessary to make a real product. Depending on the complexity of the product and the process node, which without modeling can require 2-3 iterations. With modeling, it is possible to be more precise in the first iteration, because the modeling provides a better understanding of process variables, which are tied to performance specifications.   

Update on the NeoSpectra
In September, I wrote about Si-Ware’s NeoSpecrtra NIR FT IR Spectral Sensor, winner of SEMI Europe’s MEMS and Sensor Summit Technology Showcase. Just to recap, this device has been dubbed “the world’s first spectrometer on a chip,” this device takes the ability to test blood, urine, skin cells, food samples, and more outside of the lab and into the field. At MSEC, Henri Heckman, Soilcares, presented an agricultural case study, in which the first generation of the device (Figure 1) was put to work in a handheld spectrometer for soil testing. According to Si-Wares’s Scott Smyser, at $3000, this device cost orders of magnitude less than a lab interferometer with similar performance. Heckman’s objective is to bring the knowledge from a lab into the hands of farmers worldwide, to improve soil fertility. If we can improve soil fertility worldwide, we can then increase crop yields, and feed the growing population. This is particularly critical in regions like Africa and Asia Pacific. Other potential applications for the NeoSpectra is for inline measurement for food or pharmaceutical processing, and for medical diagnostic purposes, such as a smart toilet in nursing homes for urinalysis.

Smyser also showed me gen 2 of this device, the NeoSpectra Micro™ and explained in a little more detail, the magic behind this tiny spectrometer. The company has shrunken all the optical components that are in a Michelson interferometer, onto a Si chip. Gen 2 is targeted for consumer applications, for example in smart refrigerators for testing food freshness.

That pretty much exhausts my coverage of these two events. If I missed your latest cool widget or company announcement, try to catch me next time! Next week I’ll be at SEMICON Europa and Productronica in Munich.  ~ FvT