While the physical realm of human activity contains an array of languages, the digital realm is founded on just one fundamental binary language: the 1s and 0s, also called the bits of data. Computers represent these bits as electrical signals and this forms the foundation of modern computing, communication, social media, robotics, and artificial intelligence. The 0s and 1s constantly shape the way we interact with technology and with each other on a daily basis – and the beating heart of this binary revolution is the semiconductor device.

What are semiconductors?

Semiconductors represent a distinct class of materials that possess some of the electrical properties of both conductors and insulators. Like a faucet can be used to control the flow of water, semiconductors can be used to control the flow of electric currents, and with exquisite precision.

The most important type of a semiconductor is the transistor. At the dawn of the era of modern electronics, the first integrated circuits featured four transistors. Together, they controlled the flow of currents in such a way that the circuits could perform simple arithmetic operations. Today, we have single chips boasting billions of transistors.

Fitting so many transistors on a tiny chip no bigger than a fingernail requires extreme precision and a microscopic eye for detail. For instance, the accuracy required is equivalent to dividing a strand of human hair into a thousand segments each of specific width, and further subdividing each segment into a hundred parts. This is why fabricating semiconductors involves cutting-edge technology and science.

How are semiconductors made?

The process starts with an engineer carefully selecting a silicon wafer as the foundation on which the semiconductor will be built. A team puts silicon, sourced from sand, through a meticulous purification process to separate it from other substances, until they have an ultra-pure wafer with impurity levels as low as a few parts per billion. (This percentage is comparable to an error of merely 1 cm when measuring the earth’s diameter.)

Next is the photolithography process – a crucial step that carves the circuit pattern on the wafer. The wafer is coated with a light-sensitive material called a photoresist. Then, a mask is held in front of the wafer and light is shined on it. The mask contains small gaps in the shape of the circuit pattern. The light passes through these gaps and erodes the underlying parts of the photoresist. As a result, the photoresist on the wafer ‘acquires’ the pattern of the transistor circuits.

Following photolithography, engineers use chemical and/or physical techniques to remove the uncarved parts of the photoresist, leaving behind the circuit’s structure on the silicon substrate.

Then they dope the semiconductor – i.e. deliberately add impurities to specific parts of the semiconductor to alter its electrical properties, and deposit thin layers of materials such as metals or insulators to the wafer’s surface to form electrical connections or insulate components. Then the resulting product is packaged – individual chips are separated, encapsulated, and tested to make sure they’re functional and reliable – and finally integrated into electronic devices.

What does the fabrication landscape look like?

Each step in semiconductor fabrication demands ultra-high precision and harnesses a blend of diverse scientific principles. For example, to make the most advanced transistors, the photolithography process requires a light source emitting electromagnetic radiation at a wavelength of 13.5 nm.

To achieve this, the High NA EUV machine made by the Dutch company ASML uses a cannon to shoot a 50-micrometre blob of liquid tin at 300 km/hr through a vacuum chamber, where laser beams blast it with enough energy to form a plasma that finally emits the requisite wavelength of radiation.

The semiconductor manufacturing process is characterised by specialisation, leading to an oligopoly controlled by companies specializing in specific domains. ASML, a spin-off of Philips, is in fact the sole provider of photolithography machines for cutting-edge semiconductor technology worldwide. The American firms Synopsys and Cadence dominate the software tools the engineers use to design circuits, while the silicon wafer sector is led by Japan’s Shin Etsu.

The market for the actual task of fabrication is led by Taiwan’s TSMC, with fabrication tools provided by Applied Materials and Lam Research, both headquartered in the U.S. The majority of intellectual property rights are held by British company Arm.

India boasts a leading role in chip design centred in Bengaluru. However, most of the intellectual property rights required to execute these designs are retained either by parent companies or by Arm, relegating India to being a mere user of their products. This setup is akin to the McDonald’s business model: while India may host numerous McDonald’s outlets, the recipe and supply chain are owned by a parent company headquartered in a different country.

How do semiconductors benefit us?

Smartphones and computers showcase the pinnacle of semiconductor technology but semiconductors influence nearly every facet of our lives. Semiconductors also power ‘smart’ air-conditioners’ ability to regulate the temperature as well as space telescopes’ ability to  capture both awe-inspiring and scientifically interesting images in the depths of the universe, and many other technologies in between.

Many of the solutions to the 21st century’s most important crises – including artificial intelligence, electric vehicles, space exploration, robotics, personalised healthcare, and environmental monitoring – bank on a steady supply of advanced semiconductors, underscoring their importance for the survival of the human race and its aspirations of equitability, sustainability, and justice.

Such semiconductor technology facilities foster innovation, create high-paying jobs, nurture the potential for deep-tech start-ups, and both draw from and feed into advances in materials science, computer engineering, big data, optics, chemical engineering, and chip design, to name a few.

Owing to their role in sectors like defence and automotives, semiconductors have also emerged as a focal point of geopolitical interest, with nations vying to establish semiconductor fabrication facilities within their borders and drawing industry leaders in with a plethora of incentives. The U.S. also imposed sanctions on Chinese tech companies, including bans on the acquisition of cutting-edge ASML equipment and high-end design software, for the same reason. In response, China has intensified efforts to bolster its domestic semiconductor production capabilities to meet local demand.

India, meanwhile, has been trying to use its expertise in design to establish semiconductor manufacturing plants. One hopes this strategic push plus the potential of our youth will translate to numerous opportunities for the country to seize the international semiconductor industry.

Awanish Pandey is an assistant professor at IIT Delhi with the Optics and Photonics Centre.

Computers denote data in bits – the famous 0s and 1s – using semiconductors. These are small physical devices that store these values and perform mathematical operations on them. The sum of all these operations is what allows the computer to compute.

We have powerful computers almost everywhere around us thanks to a technology called semiconductor lithography – the science of printing intricate circuits with extreme precision.

There are machines that automate this process, at a cost of anywhere between Rs 800 crore and Rs 1,600 crore. Only one company, ASML, headquartered in the Netherlands, makes them, giving it an absolute monopoly in a market worth $125 billion and rendering it the technology company with the highest market value in Europe.

In February, ASML unveiled its new ‘High NA EUV’ machine. It costs $350 million (Rs 2,900 crore) apiece and is as big as a double decker bus. Industry analysts say the machine ups ASML’s competition with Intel in the market for the most advanced semiconductors, to power the next generation of computers and smartphones.

This machine uses extreme ultraviolet (EUV) photolithography, a next-generation technology, to make the semiconductors. Here, simply speaking, the mould of the circuits of a transistor – a type of semiconductor – are transferred to a silicon wafer coated with a light-sensitive material called a photoresist. When light is shined on the photoresist, the mould solidifies and its gaps can be filled with wires to form the transistor.

What is the Rayleigh scattering criterion?

The smallest feature size that can be moulded on the silicon wafer is governed by a physics principle called the Rayleigh scattering criterion. According to this criterion, the size of the feature to be projected on the wafer is proportional to the wavelength of light used and inversely proportional to the aperture of the lens that collects light before projecting it onto the wafer.

The proportionality with the wavelength of light includes a factor called ‘k’. Its value depends on many factors, including the operating temperature and the chemical properties of the photoresist, but has a maximum value of 0.25. In the inverse proportionality, the aperture indicates the amount of light that can be collected and focused on the wafer: the greater the aperture, the smaller the feature size.

In most cases, engineers have reduced the smallest size imprinted on the wafer by reducing the wavelength of the light shined on the photoresist. Around four decades ago, for example, chip-manufacturing companies used light of wavelength 436 nanometres (nm); the latest machines of today use 13.5 nm light, which lies in the extreme-ultraviolet (EUV) part of the electromagnetic spectrum.

Just before EUV machines, chip-makers relied on deep UV light (193 nm wavelength) to project intricate patterns onto the wafers.

How is EUV light produced?

When this process is repeated multiple times across the whole wafer, the end product is an integrated circuit, a.k.a. a chip. The dominant way to make more powerful chips throughout history has been to increase the number of transistors crammed on the chip. This in turn requires the size of the transistors to become smaller, motivating innovation in reducing the wavelength of the light used to make the moulds. But this is much easier said than done.

Consider the process that the ASML machine (likely) uses to produce 13.5-nm light. First, a gun shoots a spherical droplet of liquid tin, around 50 micrometres wide (half the width of a strand of hair), at nearly 300 km/hr into the machine. In flight, a laser strikes the tin and deforms its shape into a pancake. This tin pancake is still in flight when another intense laser beam strikes it, transforming it into a hot, ionised gas with a temperature 40-times higher than that on the surface of the Sun. At this juncture, the gas emits EUV light that the machine collects for use.

This entire process – from the gun to the emission – happens 50,000-times per second to produce EUV light of sufficient intensity. That is, the guns shoot 50,000 tin droplets per second and there are twice as many laser shots to modify it. This process also unfolds within a vacuum because virtually anything, even air, absorbs EUV radiation, leaving less for the machine.

How precise is the machine?

The mirrors used to collect and reflect the generated light are a marvel as well. Crafted by the German company Zeiss, they boast the smoothest surfaces ever created by humans. Approximately 30 cm wide, their surfaces are so flawless that if scaled to the size of Uttar Pradesh, the tallest bump on each surface would be a mere 1 mm high. This is a level of imperfection lower than the size of a single atom.

Similarly, the mirrors reflect EUV light with such precision that if aimed from the earth, they could strike a cricket ball on the moon and not miss by more than the width of a strand of hair.

Finally, this light has to be guided to the silicon wafer with similar precision, which requires the wafer to be moved in increments as big as the smallest features to be printed on it. To achieve this, the stage holding the wafer floats on a magnetic field, to avoid any friction-induced compromise in precision. Ultra-sensitive sensors then adjust the wafer’s position 20,000 times per second, with an accuracy nearing just 50 picometers. This is like adjusting the earth’s position in space by a distance of one fingernail at a time.

All these 20,000 adjustments are executed with an acceleration greater than that of any F1 car or a fighter jet, to increase the device’s production efficiency.

What is the machine’s value?

As such, ‘High NA EUV’ doesn’t represent a single achievement but a collection of multiple achievements, brought together to push the boundaries of computing just enough to create the next generation.

Our future is being constantly reshaped by artificial intelligence, robots, intelligent automobiles, high-quality digital communication, powerful gadgets, and space exploration. These innovations are not only transforming the way we live and work but also opening new possibilities that were once in the realm of science fiction. The fundamental enablers of these revolutions are semiconductor chips, which carry out the enormous numbers of calculations required to materialise these technologies.

By continuously making these chips smaller, faster, and more efficient, we have gone from just four transistors in the first integrated circuit in 1948 to more than 19 billion in the chip we use in our smartphones. This innovation is driven by Moore’s law, which describes the expectation that the number of transistors on a microchip will double approximately every two years.

Lithography machines also have strategic ramifications. For example, ASML is not allowed to sell its lithography machines to China along with other components, to prevent researchers in the Asian country from potentially reverse-engineering them. So these machines underscore the fact that major technological breakthroughs can provide highly skilled jobs as well as strengthen a country’s standing in the geopolitical arena.

Awanish Pandey is an assistant professor at IIT Delhi with the Optics and Photonics Centre.