As the industry acknowledges that Moore’s Law has hit its twilight years, to be replaced by a system-level approach to achieving performance, power, and cost requirements, there’s been a question lurking behind the scenes: what will all this mean for the ITRS Roadmap—an industry icon that has kept us on the straight and narrow for decades, supporting maintenance of the pace of progress for the industry since its first incarnation as Microtech 2000 in 1991.
Back in April 2014, the ITRS announced it would be reorganizing to better suit the needs of the industry. As that reorganization approaches completion, a number of articles have been posted on this topic recently, by Pete Singer, in Solid State Technology, and here on 3D InCites, by Bill Martin of E-System Design. To go deeper into the topic, get the back-story, and see how it will impact the commercialization of 3D integration technologies, I interviewed Bill Bottoms, who has been involved in the ITRS pretty much from day one.
The Back Story
According to Bottoms, the whole point of the ITRS Roadmap was to keep ahead of the curve, so to speak, and identify and addressing potential roadblocks to Moore’s Law. But it was about a lot more than perpetuating Moore’s Law. “Moore’s Law doesn’t involve packaging or manufacturing equipment; we had to solve problems across the supply chain so that the economic cycle could continue at that rate,” he said; “that rate” being a doubling of transistors on a chip every 18 months to two years at the same cost.
Initially launched by the SIA in 1991 as the National Technology Roadmap for Semiconductors (NTRS), it evolved into the International Technology Roadmap for Semiconductors in 1998 represented by five geographical regions – the USA, Korea, Taiwan, Japan, and Europe. The organization was divided into Technical Working Groups (TWGs) which eventually grew in number to 17, each focusing on a key element of the technology and associated supply chain. Traditionally, the ITRS roadmap was updated in even years, and completely revised in odd years. During his ITRS tenure, Bottoms has been part of the Emerging Research Materials TWG, the Emerging Research Device TWG, and chair of the Assembly and Packaging TWG.
Forces for Change
Bottoms identified five driving forces that signified a need for changing the ITRS Roadmap, in order for it to continue to be useful for the industry.
First, Moore’s Law is reaching its limits. “Even if we can push the physics, the end of Moore’s Law has nothing to do with technology,” explained Bottoms. “It’s purely economic. Pushing the technology is very expensive, and even if we can make it smaller, we won’t get the same performance benefits.” As the CMOS paradigm is running out, Bottoms sees two complementary paths to follow – one involves going into the 3rd dimension to meet performance and power requirements, and the second path involves finding a new switch (other than CMOS) that is just at the beginning of its scaling, that can continue the Moore’s Law paradigm.
Second is the reality that what is driving the industry is changing. Its no longer government needs, or mainframe computers, or even personal computing. What is driving the industry today, explained Bottoms, is mobile and wireless computing, as well as the emerging Internet of Things and migration to the cloud for data and applications. Unlike with hard-wired electronics, these drivers have to take other elements into consideration, such as battery size and life, latency and having enough bandwidth.
The third driver is related to the first, and the realization that we can’t achieve necessary requirements by CMOS scaling. “Even though we can shrink the geometries, we don’t get the performance and cost advantages,” noted Bottoms.
He explained that althoughsome data transfer isn’t latency dependent, many types of data conmmunication can’t afford latency delays. The components and the architecture of the global network must be able to accommodate both requirements at low cost that must reduce each year. Heterogenenous integration and system in package (SiP) using 3D integration is the only way we can accomplish the required performance and cost advantages.
The fourth driver has to do with sharing pre-competitive information. As we get closer to the limits of physics, there are only four or five companies that can afford the investment required to continue shrinking CMOS. “These companies have their own roadmaps defined to the end of CMOS,” explained Bottoms. “They don’t need the ITRS. They already know what’s coming. They don’t want to share it and they don’t need us to tell them about it. They are focused on issues related to continued scaling and CMOS, and much of what we’re putting in the first generation ITRS is already in their history books.”
The last driver to reorganize the ITRS roadmap to version 2.0 is the desire to retain technical strength and knowledge for the industry. “We don’t want to lose all these people who have learned to work together,” said Bottoms. “While we know we have to refocus, we need to retain as much of the technical strength of ITRS 1.0 s we can, because its critical to maintain the path of progress. We don’t want to lose the technical cooperation across the world.”
ITRS Roadmap 2.0
The concept of ITRS 2.0 was first introduced in April of 2014. The plan was to take all the elements included in the 17 TWGs and map them into seven focus topics:
- System integration
This is a design-focused topic that examines architectures, and how to integrate heterogeneous blocks.
- Outside System Connectivity
Focuses on wireless technologies, how they work, and how to choose the best solution.
- Heterogeneous Integration
“This topic will do most of the heavy lifting,” said Bottoms. The focus will be on integration of separately manufactured technologies into a new unit so that they function better than the individual pieces do separately. Any new devices have to be put close together in a package. We have to make sure it’s protected. Additionally, some of the package will have to be open to the outside environment, such as cameras and microphone components. These could have conflicting requirements.
- Heterogeneous Components
Focuses on different devices that form heterogeneous systems, such as MEMS, power generation, and sensing devices.
- Beyond CMOS
The focus is on devices that provide electronics but aren’t CMOS based, such as spintronics, memristors, and others.
- More Moore
Because there is still work to be done, this group will take on the continued shrinking of CMOS.
- Factory Integration
Focus will be on the new tools and processes to produce heterogeneous integration of all these things.
3D Integration’s Role
Bottoms said it’s important to recognize that things like TSVs and 3D ICs did not play a role in the demise of the ITRS Roadmap, because they’ve been on the roadmap for years. They will play a bigger role in ITRS 2.0 as these technologies are critical to high density heterogeneous integration. “Every CMOS camera uses TSVs,” he noted. Bottoms says that the big issue is developing technologies for cost reduction rather than cost increase. “If TSV interconnect is not cheaper than wire bond, it won’t be adopted,” he said. However he is confident that ultimately TSVs and new joining technologies will be cheaper than wire bonds and therefore become the interconnect of choice for high density electronics. This will require changes in equipment, materials and processes for fabricating TSVs and joining layers for 3D assembly.
ITRS 2.0 will impact the commercialization of 3D integration technologies for one simple reason, said Bottoms, they will be successful in pointing out the roadblocks – it could be simple, like the need to lower cost, or the need for a zero-residue adhesive, or yield issues. These are things the ITRS is dealing with right now in 3D Integration. Companies interested in using 3D integration have an incentive. The ITRS aims to understand the challenge adequately, and focus research around the world as a pre-competitive activity in order to get people to cooperate and work collectively.
“There are projects underway that hopefully will be introduced to the world during the first half of 2015 demonstrating some of the required innovations,” said Bottoms. He also said that 2015 will be a pivotal year for 3D, and expects we will be in volume production for some applications by the end of 2015.
Overall, Bottoms is looking forward to a warm reception of ITRS 2.0. “I think our first effort (focus groups) will make timely contributions. It will be received well,” he said. Publication of the first ITRS 2.0 Roadmap is planned for the end of 2015 or early 2016. Rather than publishing a 2014 roadmap, each focus group published a white paper. These seven papers will be available soon. We’ll be sure to let you know when and where you can find them. ~ F.v.T.