This final ITRS report is titled ITRS 2.0. The name reflects the idea that improvements in computing are no longer driven from the bottom-up, by tinier switches and denser or faster memories. Instead, it takes a more top-down approach, focusing on the applications that now drive chip design, such as data centers, the Internet of Things, and mobile gadgets.
The new IEEE roadmap—the International Roadmap for Devices and Systems—will also take this approach, but it will add computer architecture to the mix, allowing for “a comprehensive, end-to-end view of the computing ecosystem, including devices, components, systems, architecture, and software,” according to a recent press release.
Transistor miniaturization was still a part of the long-term forecast as recently as 2014, when the penultimate ITRS report was released. That report predicted that the physical gate length of transistors—an indicator of how far current must travel in the device—and other key logic chip dimensions would continue to shrink until at least 2028. But since then, 3D concepts have gained momentum. The memory industry has already turned to 3D architectures to ease miniaturization pressure and boost the capacity of NAND Flash. Monolithic 3D integration, which would build layers of devices one on top of another, connecting them with a dense forest of wires, has also been an increasingly popular subject of discussion.
The new report embraces these trends, predicting an end to traditional scaling—the shrinking of chip features—by the early 2020’s. But the idea that we’re now facing an end to Moore’s Law “is completely wrong,” Gargini says. “The press has invented multiple ways of defining Moore’s Law but there is only one way: The number of transistors doubles every two years.”
Moore’s Law, he emphasizes, is simply a prediction about how many transistors can fit in a given area of IC—whether it’s done, as it has been for decades, in a single layer or by stacking multiple layers. If a company really wanted to, Gargini says, it could continue to make transistors smaller well into the 2020s, “but it’s more economic to go 3-D. That’s the message we wanted to send.”