Wafer bonding has been an enabling process step for the development of MEMS devices and SOI more than 20 years ago: the availability of production wafer bonding equipment have trigger the development of many innovative devices, including inertial sensors, pressure sensors, SOI substrates, CMOS image sensors… and in the future memory 3D stacking, logic and memory integration in 3D…
EV Group (EVG) has been the first equipment maker to enter such market and is now by fare the leading equipment provider for permanent wafer bonding. According to Yole Développement new report on “Permanent wafer bonding technology and market trends”, the equipment market will be multiplied by a factor of 5 in value in the next 6 years, with more than 16 millions of 8’’ equivalent wafer to be produced in 2018. EVG will explain us how the company reached that level of market shares and what could be the evolutions of the business for the next 5 years.
Discover the details of EVG activities in MEMS and microphone in the interview of Paul Lindner, Executive Technology Director at EVG.
Yole Développement: How do you explain the success of your position in the permanent bonding market?
Paul Lindner: We are following a long term strategy focusing on customer relationships and technical leadership. Every day we challenge ourselves to improve the value of our systems for our customers. We have regular discussions with our customers about how our equipment can support them better in the future. We continually seek to improve all aspects of wafer bonding: equipment, process, yield and cost-of-ownership.
One cornerstone of our strategy is the process compatibility from R&D systems and high volume manufacturing equipment. In the R&D systems we use the exact same components and control systems as in the HVM systems just with a reduced degree of automation. This guarantees that a process which has been developed in R&D can be easily transferred into production.
Another cornerstone of our strategy is our open application lab approach. We give our customers access to our newest generation equipment in our application labs in Austria, USA and Japan. Together with our process engineering team of more than 50 experienced engineers our customers develop new processes in our application lab. We have class 10 cleanrooms, which enables our customers to run product qualification lots and even pilot line production in our applications labs.
Last but not least as equipment manufacturer we have a very strong focus on superior equipment technology. We have continual improvement programs targeting technical and cost-of-ownership improvements. At the same time we are very open for technical innovations and new product developments – stay tuned for some exciting news later this year.
EVG gemini automated production wafer bonding system (Courtesy of EV Group)
YD: What are the dominant permanent bonding technologies today? For which application are they applied?
PL: For MEMS especially automotive sensors glass frit bonding and anodic bonding are widely used. For consumer MEMS applications metal based bonding e.g. eutectic bonding is very popular as it allows to reduce the dimensions of the sealing rings significantly. Fusion wafer bonding is the preferred technology for engineered substrates and backside illuminated image sensors. For optically transparent packages adhesive bonding is very popular.
YD: According to you, what will be the most promising permanent bonding technology? For which applications would it be attractive?
PL: Wafer bonding covers a wide variety of applications e.g. hermetic or semi-hermetic cavity packaging, optically transparent packaging, MEMS-to-ASIC integration and 3D stacking just to name a few. In order to fulfill the requirements for these different applications - not just technically but also from the yield and cost-of-ownership point of view - we will still see a variety of wafer bonding technologies in the future.
YD: What is the status of EVG in Advanced Packaging and what changes do you expect in the future?
PL: For Advanced Packaging the total process integration is of highest importance to achieve high yields and low cost-of-ownership. EVG covers a large number of unit processes like temporary bonding / debonding to a carrier for thin wafer processing, resist coating, developing and stripping, spray coating for topography and TSV conformal coating, lithography, chip-to-wafer bonding and of course wafer-to-wafer bonding. Together with our partners we cover the entire process chain. Due to this breadth of processes we understand the interplay from one equipment to another, how a process change in one tool impacts the process in the next tool.
Image sensor packaging was a huge success story for wafer bonding as a technology and for wafer level packaging in general as it enabled dramatic cost and yield improvements. Backside illuminated image sensors and more recently stacked image sensors are the technical frontrunners for wafer-to-wafer stacking for3D IC technology development. Wafer-to-wafer stacking will play a significant role also for other 3D IC devices in the future.
YD: What will be for you the major evolutions of the permanent bonding business in the coming years?
PL: In the past fusion wafer bonding was primarily used for SOI wafer manufacturing and some MEMS applications. In recent years fusion wafer bonding became a mainstream CMOS manufacturing technology as it is a key process step for backside illuminated image sensors.
Fusion wafer bonding is a room temperature process. This enables the best alignment accuracy of less than <300nm (3s), very fast cycle times and very high yield as the bond can be inspected and if necessary reworked prior to annealing. In addition fusion wafer bonding allows a better process standardization compared to other processes, which makes it attractive for foundries.
Hybrid wafer bonding is a subcategory of fusion bonding which allows to establish the mechanical bond and the electrical interconnects at the same time. We expect strong demand for hybrid bonding in the next couple of years.
Another important application area are engineered substrates, where wafer bonding very often allows higher quality and lower cost compared to epitaxial growth. The best known examples are SOI wafers. The same manufacturing approach can be used e.g. for GaN-on-Si, SiC-on-Si or InP-on-Si.
EVG operator (Courtesy of EV Group)
YD: What is your analysis of the permanent bonding competitive landscape?
PL: No comment!
YD: How will EVG maintain its leadership against TEL, which is currently merging with AMAT, top-tier semiconductor equipment suppliers?
PL: Our market leadership is a consequence of our technology leadership and broad application know how. The focus on early market entry, EVG’s “Triple i” strategy, and new applications gets us around “me too” situations and entry hurdles like established solutions. 20% of revenue reinvestment into R&D and high vertical integration (including our own machining capability) grows our intellectual property every year and further strengthens our partnership with loyal customers.
YD: Yole Développement evaluates the 2013 sales of EVG at >70% of total market for permanent wafer bonding equipment, did we make the right evaluation?
PL: Yes. We could grow our market share year after year in wafer bonding in general and particularly in production wafer bonding systems.
YD: How many permanent bonders did you ship in 2013?
PL: No comment!
YD: What is the roadmap of EVG in term of permanent wafer bonding technologies? In particular, what is the status of Cu-Cu bonding at room temperature and Transit Liquid Phase emerging technologies at EVG today in terms of dynamic?
PL: EVG’s development roadmap covers all of the currently used wafer bonding technologies as well as new technologies. A general theme for all processes is the cycle time reduction. Hybrid bonding e.g. SiO2/Cu-to-SiO2/Cu is an elegant way to achieve the fast cycle times of fusion bonding while at the same time enabling Cu-Cu interconnects without the need for solder.
For packaging applications the reduction of the real estate consumption for the sealing rings is a very important topic. Metal based wafer bonding is very attractive for thin sealing rings, but we also developed an innovative technology to deposit thin adhesive rings.
An important topic for cavity encapsulation is high vacuum encapsulation, which we are addressing by equipment improvements as well as by enabling new bonding techniques like transient liquid phase bonding.
Paul Lindner is EV Group’s Executive Technology Director, heading the R&D, product management, quality management, business development and process technology departments with a clear customer orientation. Paul joined the company in 1988 as mechanical design engineer and has since pioneered various semiconductor and MEMS processing systems which set industry standards.