Keeping Pace with Moore’s Law with Active Substrates And Neuromorphic Computing

New Semiconductors Needed

The semiconductor industry has constantly grown in importance over the last few decades, moving from industrial mainframe computers to an essential part of virtually every machine and device today.

This growth has been driven by semiconductors' increasing complexity and miniaturization. However, due to the fundamental physical properties of silicon, silicon-based semiconductors are starting to reach some limits.

Luckily, silicon is by far not the only material displaying semiconductor properties, aka the ability to switch from a state where it works as an insulator (not letting electricity flow) and a conductor (letting electricity flow).

New research reveals new insights into the fundamental physics of innovative semiconductor materials like vanadium dioxide and previously unsuspected semiconductor properties of titanium dioxide.

The research was conducted by a multi-disciplinary research effort carried out by researchers at the Pennsylvania State University, Cornell University, Argonne National Laboratory, Georgia Institute of Technology, and Germany's Paul Drude Institute of Solid State Electronics in Berlin.

Vanadium & Moore’s Law

What makes vanadium dioxide a prime candidate for new semiconductor technology is the ability of vanadium to switch between metal — the “1” state — and insulator — the “0” state — in only a trillionth of a second.

This is a phenomenon known as “undergoing metal-insulator transitions.” The speed of the metal-insulator transition should allow for faster and smaller electronics compared to classical silicon-based electronics.

This is essential if we want to see the semiconductor industry keep up with Moore’s Law.

Formulated in 1965, Moore’s Law is the empirical law that the semiconductor industry increases the number of transistors on a chip by 100% every two years. This has stayed true for decades since, but the fundamental limits on silicon chips mean that new types of materials will soon be needed to keep it true.

Moore's law is an application to the semiconductor industry of 1936 Wright's law, which states that manufacturing costs will reduce up to 15% for every doubling in production (initially developed for the aeronautical industry).

Wright's law is more a rule about the economy of scale and industrial efficiency when ramping up production. Meanwhile, Moore's law is more about technological innovation and is driven by progress in understanding fundamental physics and nanometer-scale engineering.

New Insights

Advanced Methods

Until now, vanadium dioxide has only been analyzed and observed as an isolated component. While useful, this limited the understanding of what would actually happen in a semiconductor relying on vanadium dioxide.

In their publication in Advanced Materials (“In-Operando Spatiotemporal Imaging of Coupled Film-Substrate Elastodynamics During an Insulator-to-Metal Transition”), the researchers made several new discoveries.

They used X-ray diffraction microscopy to observe changes in real-time and with precision at the atomic level.

And they applied the vanadium dioxide on top of a titanium dioxide substrate, like it would be in a real semiconductor chip, instead of studying it in isolation.

Source: Advanced Materials

This was a massive endeavor, with the study itself taking more than 10 years and involving many research teams and a multi-disciplinary approach.

“By bringing these experts together and pooling our understanding of the problem, we were able to go far beyond our individual scope of expertise and discover something new.” – Roman Engel-Herbert, Director of the Paul Drude Institute of Solid State Electronics in Berlin

Vanadium Movements

The researchers observed for the first time that the vanadium dioxide bulged upward when changing to a metal. This went contrary to theoretical predictions which assumed that it would shrink.

Source: Advanced Materials

They discovered that a previously unsuspected effect from missing oxygen atoms was responsible for the swelling of the material.

“These neutral oxygen vacancies hold a charge of two electrons, which they can release when the material switches from an insulator to a metal. The oxygen vacancy left behind is now charged and swells up, leading to the observed surprising swelling in the device.”

Pr. Venkatraman Gopalan, Pennsylvania State University

Titanium Substrate’s Unexpected Activity

A quasi-dogma in semiconductor manufacturing is that only the thin film of semiconductor material on top of the substrate is active when submitted to a current. The substrate itself is an electrically and mechanically passive material.

In this study, the researchers discovered this is not the case for vanadium dioxide semiconductors.

Instead, the previously thought to be inert titanium dioxide swells as well, from the same mechanism involving missing oxygen atoms.

In addition, the top layer of titanium dioxide behaved like vanadium dioxide, acting also like a semiconductor.

This new discovery will be crucial in building prototypes of commercial vanadium dioxide semiconductors.

Applications

Quicker, Better Semiconductors

Vanadium dioxide is considered a very promising material to carry semiconductor technology to the next level, due to a few fundamental characteristics:

• The Insulator-To-Metal (IMT) occurs at an extreme speed of a trillionth of a second, opening the way for ultra-fast calculations.
• Vanadium dioxide has strongly correlated electronic effects. In simple terms, this means that repulsion between electrons cannot be ignored, as is currently done in silicon-based electronics.
  • This, in turn, opens the possibilities of novel functionalities such as high-temperature superconductivity and enhanced magnetic properties.

Neuromorphic Computing

The discovery of the positive feedback process due to vacancy ionization from the missing oxygen atoms should reduce IMT time even further.

This has very important consequences, as it makes vanadium dioxide potentially able to be the right material for a new type of calculation called neuromorphic computing.

Neuromorphic computing is a method where computer systems that take inspiration from the brains of living systems with neurons.

This differs from the neural networks currently used by AI and LLMs that try to mimic neurons, but still relies on classic silicon transistors and is mostly software-based machine learning.

So, neuromorphic chips could learn at the hardware level. And instead of binary output (0s and 1s), they would produce spikes of signal.

Source: Tech Target

Thanks to its very quick Insulator-To-Metal transition, vanadium dioxide with an active substrate of titanium dioxide could be used to create Mott neuron-like spiking oscillators able to replicate at the hardware level biological neurons.

Overview

Vanadium dioxide semiconductors, neuromorphic computing, and Mott neuron-like spiking oscillators are at the very edge of material science and semiconductor design, probably at least a decade before reaching commercial viability.

This decade's time frame is exactly when we should expect silicon-based semiconductors to start failing in keeping Moore's law valid.

There is nothing in Moore's law that says semiconductors need to be silicon-based. It is rather an empirical observation that as long as there is a demand for more powerful chips, researchers keep learning more about semiconductor physics at a smaller and smaller scale.

Considering that we are now studying vanadium and titanium dioxides, in real-time and at the atomic level, it seems reasonable to expect Moore's law to hold and materials like vanadium to be the next step in semiconductor design.

And of course, other innovative ways of computing could also help keep Moore's law on track, like photonics or quantum computing.

Advanced Semiconductors Companies

1. Intel

Intel is a giant in the semiconductor sector and has evolved over the years from a founder of the industry to a scientific and innovation leader, losing the top spot of manufacturing volume to companies like Taiwan's TSMC.

Intel is a leader in neuromorphic computing, including through its Loihi 2 chip.

Source: Intel

It also created the Intel Neuromorphic Research Community, which includes Pennsylvania State University, involved in this recent vanadium dioxide research, as well as 75+ other research groups.

Source: Intel

Intel is also very active in mimicking biological sense through replicating the way our brain works (itself a branch of neuromorphic computing), something we discussed further in our article “Biomimetic Olfactory Chips: Are Artificial Intelligence and E-Noses the Next Canary in a Coal Mine?”

Overall, research from Intel Lab is at the forefront of semiconductor innovation, including AI, quantum computing, neuromorphic computing, etc. (we discuss Intel advances in quantum computing in our article “The Current State of Quantum Computing”).

2. IBM

Another historical pioneer in computing, semiconductors, and chip design, International Business Machines Corporation (IBM) is also investigating neuromorphic computing.

It is also developing SyNAPSE: Scalable energy-efficient neurosynaptic computing, supported by Defense Advanced Research Programs Agency (DARPA), to combine “nanoscience, neuroscience, and supercomputing to simulate and emulate the brain's abilities for sensation, perception, action, interaction and cognition “.

It is equally at the forefront of the development of quantum computers. For example, it developed its 127-qubit “Eagle” quantum computer, which was followed by a 433-qubit system known as “Osprey and the 1,121 superconducting qubit quantum processor “Condor”.

Source: All About Circuits

Together with Intel, IBM is among the companies most aggressively pushing for new forms of computing technologies, like quantum and neuromorphic computing, and is likely to benefit from the progress made in understanding the fundamental atomic physics of materials like vanadium dioxide.