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Lithography explained
Lithography is the step in chip making that prints circuit patterns onto a silicon wafer using light, and it is the technology that most defines how small and dense a chip can be. It works by projecting a pattern through precise optics onto a light-sensitive coating, then developing that coating into a stencil for the steps that follow. Lithography systems are the most complex and expensive tools in any fab, and Tata Electronics signed a lithography partnership with ASML, the global leader, reported around 17 May 2026 for the Dholera fab.
Last checked 2026-08-11 · every figure below carries its source
What lithography does
Lithography is the patterning step, the moment in chip making when the design of a circuit layer is transferred onto the wafer. Every other step needs lithography to tell it where to act. Etching needs to know where to remove material, doping needs to know where to add atoms, and metal wiring needs to know where to run. Lithography defines all of that by printing a pattern. The name comes from an old printing technique, and the principle is similar. A pattern is used to selectively expose a surface, creating an image that guides later work. In a fab, this printing is repeated for every layer of the chip, and a modern chip has many layers, so lithography is performed dozens of times on a single wafer. Because it decides the size of the features that can be printed, lithography sets the limit on how advanced a chip can be, which is why it is treated as the crown jewel of fab technology.
How the printing works
The process begins by coating the wafer with a thin, even layer of photoresist, a chemical that changes when exposed to light. The pattern for the current layer is held on a mask, a kind of stencil. Light is shone through the mask and focused by a system of extremely precise lenses or mirrors onto the wafer, projecting a sharp, shrunken image of the pattern onto the photoresist. Wherever the light strikes, the photoresist changes chemically. The wafer is then developed, which washes away either the exposed or unexposed resist depending on the type used, leaving behind a patterned stencil on the wafer surface. That stencil protects some areas and exposes others for the next step, such as etching or ion implantation. Once that step is done, the remaining resist is stripped and the wafer is cleaned, ready for the next layer to be coated and printed all over again.
Why smaller light means smaller chips
The size of the features lithography can print depends heavily on the wavelength of light used, along with the quality of the optics. In simple terms, shorter wavelengths of light can resolve finer details, just as a fine-tipped pen draws thinner lines than a broad marker. Over the decades, the industry moved to ever shorter wavelengths of ultraviolet light to keep shrinking features, using clever optical tricks to push each generation further than its wavelength would suggest. The most advanced chips today use extreme ultraviolet lithography, which employs a far shorter wavelength and requires astonishingly sophisticated mirrors and vacuum systems, since that light is absorbed by almost everything, including air and glass lenses. Mature and specialty nodes, like those planned at Dholera, use well-established ultraviolet lithography rather than the extreme ultraviolet systems reserved for the leading edge, which keeps the technology proven and the cost more manageable.
Why lithography tools are so special
Lithography systems are widely regarded as the most complex machines ever mass produced, and they are the single most expensive class of tool in a fab, with advanced systems costing tens of millions of dollars each. Their difficulty comes from the need to project a pattern with nanometre precision, repeatedly, across a wafer, aligning each new layer to the ones beneath it with almost no error. This demands extraordinary optics, motion systems that position the wafer with incredible accuracy, and stable environments free of vibration and temperature swings. The industry for the most advanced lithography is highly concentrated, with ASML of the Netherlands being the recognised global leader, and the only supplier of extreme ultraviolet systems. Securing a relationship with such a supplier is a major milestone for any new fab, because without capable lithography a fab simply cannot produce competitive chips. It is the bottleneck around which much of the industry is organised.
Lithography at the Dholera fab
For the Dholera fab, lithography capability is central, and Tata Electronics signed a lithography partnership with ASML, the global leader, reported around 17 May 2026 and now confirmed on Tata Electronics' own press page rather than resting on a press MoU alone. This matters because it gives the fab access to proven patterning technology and the support that comes with it. The Dholera fab targets mature and specialty nodes across a reported 28 to 110 nm range, starting at 55 nm and 90 nm before moving to 28 nm, which use established ultraviolet lithography rather than the extreme ultraviolet systems reserved for the leading edge. That is an appropriate match for the fab's product focus of power-management integrated circuits, display drivers, microcontrollers and high-performance computing logic. Installing and qualifying lithography tools is one of the demanding steps that follows the cleanroom fit-out, part of the path toward the fab's first trial silicon target of around December 2026.
Lithography and the road to first silicon
Because lithography defines every layer, getting the lithography tools installed, calibrated and qualified is one of the gating tasks between a completed fab building and actual chip production. Each tool must be moved into the certified cleanroom, connected to power, ultrapure water and specialty gases, and then tuned until it can print patterns to specification and align them precisely to previous layers. Only when the lithography and the other process tools are qualified can full wafer lots run through the complete flow to yield first silicon. At Dholera, with structural work reported complete and cleanroom fit-out and equipment move-in underway as of mid-2026, the sequence points toward the first trial silicon target of around December 2026, with commercial-scale production reported for about mid-2028. No source confirms a chip has been produced yet, so these remain targets. The ASML partnership is a key enabling piece of that timeline rather than a guarantee of any particular date.