A transistor is the fundamental building block of an electronic chip. Essentially an on and off switch driven by electricity, a transistor's 'On' switch represents a binary 1 and an 'Off' switch represents a binary 0.
This binary language of 0s and 1s is the operating principle of modern electronics. The number of transistors on a chip and the latency of their communication links decide the speed, cost, capabilities, and power consumption of the chip, thereby determining the performance and affordability of the electronic gadgets that use the chip.
In 1965, Intel’s co-founder, Gordon Moore made an informed prediction that approximately every decade, the size of transistors would shrink and the number of transistors on an electronic chip would double, consequently reducing the chip’s power consumption, manufacturing cost, and increasing its speed and capability. In 1975, he revised the period from a decade to just two years.
This observation, famously known as Moore’s Law, has driven the electronics revolution of our modern age.
Almost half a century later, the current electronic chips consist of billions of miniature transistors—shrunken to just a few molecules—photolithographically built on a Silicon wafer. We are reaching the physical limit of how small the transistors can be, and by extension, reaching the limits of Moore’s Law.
We thus need to devise ways to either shrink the size of transistors even further or improve the chip’s performance while keeping the number of transistors unchanged.
Some options include using photonic chips instead of electronic chips (that is, using light instead of electricity as communication links), using molecular electronics that allow for making smaller and faster transistors, and using new chip manufacturing processes.
The speed of an electronic gadget is determined by the size of the transistors as well as the communication mechanism. At present, transistors use electrical signals (i.e. electrons moving from one place to another) to communicate.
Using photons instead of electrons, we could make transistors even faster since photons are much faster than electrons. Moving from electricity-based transistors to light-based transistors could be the key to faster gadgets.
Significant strides have been made in the field of photonic technology.
For instance, the research team at RMIT University, led by Dr. Alberto Peruzzo, demonstrated the use of photonic chips to process quantum information, which might aid the development of scalable quantum computers. However, the photonics industry is still in nascent stages. As of now, electronic devices perform far better than photonic devices in terms of size of components and manufacturing costs, so replacing electronics with photonics might not be a reality anytime soon.
If we find a way for photonic chips to complement, if not replace, electronic chips, that would be a non-trivial performance gain.
For example, the optoelectronic chip being designed by Ayar Labs uses light to transmit data but computes it electronically. The possible applications for the chip are for datacentres and supercomputers, and the startup predicts that using the optoelectronic chip will result in an energy reduction of 30 to 50 per cent over its pure electronics counterpart.
Cable network wires. Image courtesy of Unsplash.
Molecular electronics is a branch of nanotechnology that uses single molecules as building blocks for electronic devices. Because molecules are the smallest stable structures, single-molecular devices are the end goal for electronics miniaturisation.
Manufacturing monomer (single-molecule) devices is no easy feat, though. Several obstacles need to be overcome before molecular electronics wins the miniaturisation race. One such obstacle is the requirement for single-molecule devices to remain stable at room temperatures. This is a critical requirement for the devices to have any real-life applications.
The research team at Columbia University were successful in synthesising single-molecule devices that can remain stable at room temperatures, thereby enabling further progress in molecular electronics.
Another approach to use the benefits of molecular electronics is to use a string of molecules instead of single molecules. The research team at the Tokyo Institute of Technology found that polymers (a string of monomers) demonstrate better performance than individual monomers. These seem like a potential solution to our miniaturisation problem.
Advanced Photolithographic Techniques
Photolithography is a manufacturing technique used to produce electronic chips. It involves projecting ultraviolet light to transfer a circuit pattern from a photomask to a silicon wafer.
The current photolithography manufacturing process allows chip manufacturers like Intel to produce transistors at the size of 14nm across. Intel executives are hopeful that advanced photolithographic techniques combined with Silicon-substitute materials and reimagining the transistor design will enable them to reduce the size of transistors to as small as 5nm.
Intel chip affixed to motherboard. Image courtesy of Unsplash.
Although these breakthroughs in the fields of photonics, molecular electronics, and photolithographic manufacturing processes are promising, we don’t yet have a clear winner in the electronics miniaturisation race.
What we do know, however, is that humans will continue to innovate and come up with creative solutions to circumvent Moore’s Law: we might discover advanced algorithms or new materials to obtain better performance from the same number of transistors on a chip, or we might completely rethink the chip and transistor designs.
The end of Moore’s Law is not the end of our technological progress. Indeed, perhaps it is just a new beginning.