IBM Unveils Vertical Transistors to Try to Keep Moore's Law Alive
The most advanced chips on the market resemble sprawling suburbs, with transistors arranged like blocks of houses on a slab of silicon. IBM is trying to level all the houses and replace them with apartment towers.
The technology giant on Tuesday introduced what it called a Vertical-Transport Field-Effect Transistor, or VTFET, which it said could double the speed of the FinFETs that have dominated the chip landscape for a decade. IBM said it saves space by arranging transistors perpendicular to the plane of a chip, with current traveling up and down instead of cascading through transistors sprawled out on the chip side by side.
IBM said the new transistor would open the door for companies to keep piling transistors into chips at the heart of everything from phones and laptops to data centers. The continuous cramming of these features on silicon wafers, called Moore’s Law, has been the chip industry's gospel for decades, leading to smaller, faster, and more efficient chips. But the pace of these engineering feats has been slowing for years now.
IBM said VTFET can deliver double the performance at the same power level as FinFET transistors scaled to the same process node due to improved electrostatic control and parasitics. Alternatively, it can support an 85% power reduction compared to FinFETs at an equivalent frequency, IBM said.
However, it could take years for firms to master the engineering and manufacturing feats behind VTFET.
IBM Research
IBM was previously one of the world’s most advanced chip manufacturers but it started to contract out its production to Samsung years ago. It remains a powerhouse in semiconductor research and runs a major research center in Albany, New York that produces test runs of chips, including its VTFET test chips. IBM has a joint development deal with Samsung, which collaborated on the VTFET, to use IBM’s innovations.
The company plans to make money by licensing the technology to other firms. Earlier this year, Intel CEO Pat Gelsinger announced its IBM 2.0 strategy, including a new agreement to partner with IBM on research.
The VTFET is IBM's second notable semiconductor innovation in recent months.
Earlier this year, IBM introduced what it said was the world's first chip based on 2-nm technology, which promises to be smaller and faster than the 5-nm chips used in high-end phones, such as Apple's iPhone 13. IBM said the 2-nm chip contains 50 billion transistors based on its nanosheet—or gate-all-around (GAA)—technology in a 150-mm2 area, giving it a density of over 330 million transistors per square millimeter.
The most advanced processors contain tens of billions of transistors arranged into logic gates. Electrons cascade between components called the "source" and "drain" contacts, forming a "channel" that conducts current. The channel determines how fast current flows and how much leaks out, which influences power efficiency. The "gate" starts and stops the flow, switching the transistor on and off to represent 1s and 0s.
The transistors used in the most advanced chips today are FinFETs. A fin-shaped ridge of silicon is placed in the transistor with the gate enveloping it, forming channels on three sides. The three-dimensional shape of the fin permits more current to flow during the "on" state and less current to leak out of a channel when a transistor is switched "off." This not only improves speed but also reduces the power siphoned by a chip.
Vertical Transistors
For decades, IBM and others have raced to cram smaller and smaller transistors on squares of silicon by reducing the gate pitch and scaling the interconnect wires between them. The physical space where all the components are placed is the contacted gate pitch (CGP). But as the most advanced of these switches are now smaller than a virus, they are running out of room to squeeze the parts into the finite area of the CGP.
With the VTFET, IBM said that it flipped the fin inside the transistor so that the source and the drain are placed perpendicular to the gate, dramatically improving density scaling. The transistors on a processor have to remain isolated from one another to reduce interference. Chip makers keep them apart by placing "isolation gates" between them. IBM said VTFET would get rid of these components, leaving room on the chip to cram in more transistors.
The vertical orientation means the device's gates, spaces, and contacts are no longer constrained in the same ways, giving companies more freedom to fine-tune the transistor's performance and power usage. IBM said companies can alter different aspects of the transistor to improve the drive current and leakage or keep capacitance in check. IBM said VTFET can also use larger source and drain contacts to increase the device’s current driving capacity.
IBM and Samsung have high hopes for the research. The companies said VTFET transistors could be used in ultra-efficient chips that could prolong a smartphone's battery life to more than a week, instead of a day.
"Today's technology announcement is about challenging convention,” said Mukesh Khare, head of IBM's semiconductor research.
