IBM has unveiled "what it says is the world's first sub-1-nanometer chip technology," reports ZDNet, "designed to pack nearly 100 billion transistors on a fingernail-size die, roughly doubling the density of IBM's earlier 2-nm test chip, first shown in 2021... Today, the smallest, most powerful chips top out at about 80 billion transistors."


At the heart of the announcement is NanoStack. This is a three-dimensional, nanosheet-based transistor design that scales vertically, or along the z-axis, by stacking and staggering CMOS devices. Unlike today's nanosheet architectures, which IBM also pioneered and which are being adopted by leading foundries at 3 nm and 2 nm, NanoStack bonds two nanosheet transistors into a single vertical structure, with each tier optimized independently and contacted from opposite sides. Each transistor in the demonstrated structure uses three sub-5 nm-thick nanosheets, about "15 silicon atoms" across, separated by roughly 9 nm spacers. Two such devices are then bonded vertically using an ultra-thin dielectric process IBM describes as a key innovation. Because the top and bottom devices can use different channel materials, dielectrics, and metals, IBM argues NanoStack is less a single trick and more a transistor platform that can be extended through multiple generations: 7 angstrom (Å), 5 Å, 3 Å, and potentially down to 1 Å in its internal roadmap.

An angstrom, by the by, is one ten-billionth of a meter. In terms of chips, an angstrom is a tenth of a nanometer. "This is the world's first sub-1 nanometer chip technology with a new transistor architecture," said Jay Gambetta, Director of IBM Research and IBM Fellow, during a press briefing. "We're not just making smaller transistors, we're reinventing how chips are built to deliver dramatically more power and energy efficiency...." Based on internal benchmarking against its 2 nm node, the company said its new chips will deliver up to 50% higher performance at the same power, or up to 70% lower power for the same performance. Big Blue also highlighted a 40% improvement in the scaling of static random-access memory (SRAM) cell area relative to its 2 nm technology.

This is a change IBM described as a "step the industry hasn't seen in over a decade" and one that could be particularly important for AI accelerators that live or die on on-chip memory bandwidth... According to Huiming Bu, IBM's VP of silicon technology R&D, NanoStack is a new paradigm. It's moving chips to scaling fully into three dimensions and giving the industry at least "another decade" of logic advances as it crosses from nanometers into angstroms... The 40% SRAM density bump could also help architects push caches and on-die memory closer to compute units, cutting data movement overhead in training and inference workloads.


IBM sees a path to production use "in as early as the next 5 years", according to the article, and "expects NanoStack to eventually underpin CPUs, GPUs, mobile SoCs, and SRAM arrays."

IBM's VP of silicon technology R&D says the new innovation "can improve performance by 50% compared to the best available chip today, and at the same time can reduce power by 70%."

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