advanced packaging

SEMI spoke with Thomas Fries, founder and CEO of FRT GmbH, about how hybrid metrology is shaping multi-sensor metrology tools to enhance measurement precision as the industry moves away from a single-sensor approach.Fries offered his views ahead of the SEMI MEMS Imaging Sensors Summit, 25 to 27 September 2019 in Grenoble, France. Join us at the event to meet experts from FRT Metrology and many other MEMS, imaging and sensors companies. Registration is open. SEMI: Metrology in front-end used to be straightforward. But then, as the number of tasks to be implemented increased, we moved to a multi-sensors approach. What drove this transition?Fries: I believe it´s more about software than about sensors. But of course the basis is the hardware. So, most metrology tools were designed around a specific sensor, e.g. a white light interferometer.A rigid frame, wafer fixtures, scanning tables etc. were then added to develop a complete system. In manufacturing more machinery was added, like handling systems, cleanroom equipment and more sensors, mainly for additive functions such as reading IDs or measuring temperature. The center was still the one and only sensor, being pimped more and more by some hardware features and a lot of software.SEMI: How are sensors and software shaping the way metrology is applied today?Fries: Today a huge number of optical sensors are available to provide various measurement options. But sometimes there are only very slight differences from one sensor to the other. A tiny variation may determine whether we solve a problem or end up fishing in troubled waters.And of course using different machines with those sensors requires high budgets for capital investment, used floor space, measuring time, etc. A multi-sensor platform solves all these problems. But again, it is the software that makes the real difference.SEMI: What lead to those advancements in metrology? What problems did they set out to solve?Fries: Metrology has been evolving ever since the measurement standards were established. The first challenge was to create a flexible mechanical platform that was also reliable and stable. All components were designed to be integrated into one system, mechanically, electrically and of course in the software.This level of integration requires not only an appropriate user interface, but also data formats and evaluation algorithms that leverage multi-sensor hardware. Today every metrology tool in the fab is justified by the application, not by specific sensors or specs. Of course the application leads to a set of specs, but the solution for the metrology task is realized within the software.New developments in metrology combine expertise in system design, physical knowledge in metrology and materials, mechanical engineering and also mathematical and software skills.The last step was the implementation of hybrid metrology functionality into a multi-sensor system that opens totally new doors in metrology. Before multi-sensors development, quite a few hitches could not be properly solved. SEMI: This is especially true when we consider applications in advanced packaging and MEMS manufacturing. What is in your opinion the main challenge?Fries: Specifically, in MEMS and advanced packaging we face multiple metrology challenges, as various processes run in one step and conditions on the wafer may vary quite often. In this case, a high degree of flexibility, up to the option to upgrade the metrology tool at any time or place, is a priceless advantage. Besides, cost effects for footprint, throughput and investment play a key role.A central task for nearly every customer application is to combine global measurements (complete wafer) and local measurements (per die) within one recipe. This is a perfect case for a multi-sensor platform. Measuring step heights and film thickness in one take is also an everyday routine. Combining those characteristics to measure hidden structures (hybrid metrology) is unique.SEMI: How will hybrid metrology enhance measurement precision and where do you expect the multi-sensor approach to be more applicable?Fries: The first advantage is the ability to measure properties that you cannot access directly. On top of that, all the previously mentioned features such as facing multiple metrology tasks, the combination of complete wafer and per die measurement are playing key roles. The precision of specific measuring tasks can be optimized by calibrating sensors against each other or combining results to get rid of noise or artefacts.MEMS and advanced packaging are natural playgrounds for hybrid metrology. But already today we see applications in high volume manufacturing in the 300mm fabs. As structures on wafers shrink, wafers are getting thinner and the whole process is becoming more and more complex. The classic one-sensor metrology tool is running out of gas. SEMI: What are your expectations regarding the summit in Grenoble, and for the future of the MEMS Sensors technology?Fries: FRT has always been very strong in MEMS and sensors and we have attended and exhibited at the SEMI MEMS Imaging Sensors Summit from the very beginning. The summit is always a very good meeting point for the community, and a perfect training session that gives participants extended updates in all fields. And of course, it grows our network and gives us the opportunity to show our latest products and applications.If you really want to know how the future of MEMS and sensors will look like, join the summit and don´t miss the chance to pass by the exhibition to meet FRT and many other industry leaders.Dr. Thomas Fries lives with his family close to Cologne. He is engaged in a variety of activities: as technical advisor to various ministries, supervisory board of PlanOptik AG, board and advisory board of IVAM, board member of COPT.NRW e. V., just to name a few. FRT supports many social projects as well as kindergartens and schools. Motorcycles and cars are still a great passion alongside his family.Serena Brischetto is senior marketing and communications manager at SEMI Europe.

Materials innovation has always been vital to the semiconductor industry. In the past, it was high-κ gate dielectrics. Today, Cobalt is seen as a replacement for Tungsten in middle-of-line (MOL) contacts.What materials innovation will the future bring?A likely answer is Graphene, the wonder material discovered in 2004.Graphene is one atomic layer of carbon, the thinnest and strongest material that has ever existed. It is 200 times stronger than steel and the lightest material known to man (1 square meter weighing around 0.77 mg). It is an excellent electrical and thermal conductor at room temperature with an electron mobility of ~ 200,000cm2.V-1.s-1. At one atomic layer, graphene is flexible and transparent. Other notable properties of Graphene are its uniform absorption of light across the visible and near infrared spectrum and its applicability towards spintronics-based devices.Graphene and Moore’s LawMoore’s Law scaling can be broken down into 4 key areas: Lithography FET Advanced Packaging (2.5D and 3D IC) Interconnect Material Solutions for upcoming nodes are starting to emerge in the first two areas (EUV and Nanowire- or Nanosheet-based FET respectively). Graphene play an important role in the latter two areas. For advanced packaging, Graphene can be used as a heat spreader (to lower overall thermal resistance), or as an EM shield (to lower crosstalk) as part of a 3D IC package.Active Graphene device layers can potentially be stacked on top of each other using a low-temperature transfer process ( 400°C) to allow for a dense heterogeneous “memory near compute” configuration. This is an area DARPA is actively researching as part of its new $1.5 billion Electronics Resurgence Initiative.Regarding interconnects, Copper interconnects are running out of steam and becoming a major IC bottleneck (projected 40% total delay for 7 nm node). Graphene’s high electron mobility and thermal conductivity make it an attractive interconnect material for MOL and back-end-of-line (BEOL), especially at line widths 30 nm.Graphene Device ApplicationsGraphene-based semiconductor applications are already starting to hit the market. A fully integrated optical transceiver (with a Graphene modulator and photodetector) operating at 25 Gb/s/channel was on display at the recent Mobile World Congress in Barcelona. San Diego-based Nanomedical Diagnostics is selling a medical device that uses a Graphene biosensor. Europe-based Emberion is building Graphene optoelectronic sensors that might find a home in LIDAR applications, where there is currently a focus on improving sensing in low-light conditions.What will the overall Graphene roadmap in the semiconductor industry look like? The history of ion implantation serves as a good example of how a fundamental scientific discovery moves from the lab to the foundry floor.The dominant view in the semiconductor industry at the time was that ion implantation would not work in practice (vs. thermal diffusion) and that, if it did, it would only marginally improve the manufacturing yields of existing products. There was nothing obvious about the transfer of ion bombardment techniques from nuclear physics research to semiconductor production.Varian (led by British physicist Peter Rose) built a new, advanced ion implant tool that Mostek (DRAM manufacturer based in Texas) was able to use to create MOS ICs with clear competitive advantages. The successful collaboration between Varian and Mostek was the turning point in the development of ion implantation as a major semiconductor manufacturing process. Over the next few years, semiconductor firms used ion implantation in a growing number of process steps and, by the late 1970s, it became one of the main processes used in semiconductor manufacturing.Likewise, the Graphene world needs to work closely with the semiconductor industry to develop the tools and techniques required to solve fundamental issues around Graphene growth (good uniformity over large area, low defect density) and Graphene transfer (high throughput, CMOS compatible). It is only then will we fully realize a future that includes 2D materials.The first step in this process is cross-industry education and initiating the dialogue between semiconductor industry and graphene companies. The National Graphene Association will be hosting the largest gathering of graphene companies and commercial stakeholders at the Global Graphene Expo Conference, October 15-17, 2018, in Austin, Texas.Learn more about graphene at the upcoming Global Graphene Expo Conference with dedicated panels of experts and investors, and roundtable discussions on how Graphene will impact the semiconductor industry. The event promo code is SEMINGA. About the AuthorAnand Chamarthy is the CEO and Co-Founder of Lab 91, an Austin-based startup that is working towards Graphene/CMOS integration at the foundry level. Anand can be reached at [email protected]. About the National Graphene AssociationThe National Graphene Association is the main organization and body in the U.S. promoting and advocating for commercialization of graphene and addressing critical issues such as standards and policy development.