When the semiconductor industry received the eagerly awaited annual update of the International Technology Roadmap for Semiconductors (ITRS) at the end of March 2014, it got—as usual—a bit of NIST as well. Numerous NIST staff served in key roles that helped shape the new edition.
The ITRS is a closely watched consensus assessment of the semiconductor industry's technology requirements for the next 15 years. Semiconductor manufacturers established their industrial roadmap for manufacturing in the early 90s in order to forecast future gaps in manufacturing technology, and potential solutions to them, so that manufacturing of computer chips would keep pace with Moore's Law - the doubling of information processing power every 18 months at a constant cost to the consumer. These advances in computational power for the most part came as a result of scaling, reducing the size of the transistors, which are the basic components of computer chips.
Several NIST staff members serve on various ITRS Technical Working Groups (TWGs) covering 12 specific topics which are presented as chapters in the final document. In addition, there are five cross-topic groups, in two of which NIST staff are active. It is within the TWGs that consensus is achieved on the state of the industry, future directions, and potential roadblocks. The TWG chairs lead these meetings, communicate with the members in the interim between meetings, and seek additional expertise from others in their fields. Three of these TWG chairs (George Orji, Michael Gaitan, and Herbert Bennett) reside within the Semiconductor and Dimensional Metrology Division (SDMD) of PML.
PML's George Orji is co-chair of the Metrology Technology TWG of the ITRS for this new 2013 edition, working alongside Alain Diebold of State University of New York, Albany. While Orji has been involved in the ITRS since 2005, this was his first year co-chairing a TWG.
"My role as the co-chair is to coordinate the writing of the roadmap together with Alain Diebold and also to seek information from people here at NIST and across industry," Orji explains.
The new chapter on Metrology Technology includes an inaugural section on 3D Nanometrology. The inclusion of this section was deemed necessary because of the increased importance of 3D stacked integrated circuits in the industry.
"This alone is driving the industry," Orji says. "It's not just about measuring things that are planar anymore. It's also about measuring things that are on the sidewalls, measuring the different shapes, and using the full 3D information to get your results. You need a wide variety of tools to do this and you need to find out how the tools will work with each other. We came up with a fairly long section, listing exactly what is required, what the specifications are, and what parameters are being measured."
Michael Gaitan, a Project Leader in PML, is chair and editor of the MEMS TWG, which is affiliated with both the ITRS and iNEMI (International Electronics Manufacturing Initiative) and works closely with the MEMS Industry Group. Influenced by the emergence of wearable devices (e.g., fitness wristbands) and portable medical diagnostic devices, the 2013 update of the MEMS chapter features the concept of a "Functional Integration Path" to industrial growth.
"This work is important because the industry is nearing the end of Moore's Law, as defined by device scaling," Gaitan says. "Such functional integration is already happening in many consumer products."
While the ITRS has served the semiconductor industry well for over 20 years, scaling is expected to reach its physical limits in the next few years. The industry is looking at two options to continue its manufacturing growth: creating new nanotechnologies that can surpass those limits in scaling; and integration of new functions such as sensors, radio, power devices, etc., together on the computer chips. The path of integrating new functions, which we already see happening in consumer electronics and smart phones, is referred to by the industry as Heterogeneous Integration, also called "More than Moore."
At its last meeting held in April in Bad Nauheim, Germany, the ITRS leadership has begun implementing a strategic plan to refocus itself to address this evolution of semiconductor manufacturing in to what they refer to as "ITRS 2.0." This process involves the development of new focus teams, such Heterogeneous Systems and Components, which rely heavily on the Assembly and Packaging, RF and Analog Mixed Signal, and MEMS TWGs.
Through the paradigm of heterogeneous integration, the industry expects to continue its trend of growth but in a different way; instead of using the strategy of scaling to add more power to computer chips, it expects to use heterogeneous integration to add more functions. Imagine, for example, a complete smart phone, except for the display, on a single chip. The goal of this process is to predict the gaps in device technologies, manufacturing, packaging, and testing that need to be solved in order for manufacturers to be able to make such products.
Like Orji, Gaitan has the challenge of pulling content from multiple TWG members and bringing it together into a polished chapter for the 2013 edition of the roadmap.
"These sections are written by different authors with different writing styles, which I then merge together into a cohesive document," Gaitan explains. "I lead the writing of the introduction sections, the conclusions, the executive summary, and this year I added a new section on Wearable Technologies and the concept of Functional Integration."
PML's Herbert Bennett is chair of the RF (Radio Frequency) and AMS (Analog/Mixed Signal) TWG of the ITRS. Bennett has long been an advocate of coordinating roadmapping efforts in this field, co-founding the TWG on RF and AMS Technologies for Communications back in 2001. Among the new infrastructure challenges singled out by Bennett's 2013 TWG is the need for the RF and AMS community to form an industry group, similar to what the MEMS community has in the MEMS Industry Group.
"They need an international trade association or consortium," Bennett says. "Having such an industry group will decrease the time to meet the technical RF and AMS requirements for a successful Internet of Smart Things and for the hardware components needed in advanced communications systems."
Other highlights in the 2013 RF and AMS chapter include discussions on 1) the co-integration of active and passive devices that if not addressed adequately may lead to increased costs and more difficult process controls for high volume, high quality manufacturing 2) the difficulties associated with increasing the functionality of power amplifiers, and 3) the first time use of computer simulations to forecast the performance figures of merit in the ITRS technology requirements tables for RF and AMS technologies.
Additional NIST participation in the ITRS is strong as well, with the SDMD's Yaw Obeng and Kin (Charles) Cheung contributing to the writing of the Emerging Research Devices and the Process Integration, Devices, and Structures chapters, respectively. Outside of PML, the Material Measurement Laboratory has active participation in many areas of research covered by the ITRS, including metrology, emerging materials, and front end processes.
"The ITRS is an important source of information to facilitate strategic planning within MML because it represents industry consensus from a major sector of the U.S. economy," explains Laurie Locascio, the MML Director.
PML's George Orji sees long-term benefits of continuing his leadership with the ITRS: "Knowing what the requirements are helps NIST researchers to know where to focus their research efforts," he explains. "And our participation in the ITRS helps with the dissemination of our work. You could do the best 3D nanometrology possible, but it doesn't matter if no one in the industry knows about it!"
 The ITRS is sponsored by the European Semiconductor Industry Association (ESIA), the Japan Electronics and Information Technology Industries Association (JEITA), the Korean Semiconductor Industry Association (KSIA), the Taiwan Semiconductor Industry Association (TSIA), and the United States Semiconductor Industry Association (SIA).