All about light and lasers in lithography (2024)

All about light and lasers in lithography (1)

From visible blue light to invisible extreme UV light, ASML’s lithography machines keep innovation in light and lasers moving forward

What is a light wavelength? Like waves in the sea, light travels as a series of peaks and troughs. The distance between the peaks is called a wavelength. The shorter the wavelength of light, the smaller the microchip features that can be printed in a lithography process.

Throughout ASML’s history, we’ve supported chip manufacturers in making the transition to new lithography wavelengths that make more advanced microchips possible. Each step forward required innovation in how the light is generated, from visible blue light to ASML’s exclusive extreme ultraviolet (EUV) technology.

Mercury lamps: from blue to UV

When ASML was founded, the state-of-the-art light source for lithography was the mercury vapor lamp. This generates light by passing electricity through a bulb that contains mercury. The current heats the mercury until it becomes a plasma that emits light of various wavelengths. The required wavelength was selected with an interference filter.

Our first lithography systems used this setup to create blue light with a wavelength of 436 nanometers (nm), known as the mercury g-line. They could print features as small as 1 micron (1,000 nm). To enable smaller features, we soon switched to invisible ultraviolet (UV) light with a wavelength of 365 nm. These later i-line systems pushed feature sizes below 1 micron, eventually reaching 220 nm.

All about light and lasers in lithography (2)

Lasers and DUV

In the mid-1980s, the industry demand for smaller features led to another shift to shorter wavelengths. And this time, a whole new way of making light was needed: lasers. In particular, deep ultraviolet (DUV) excimer lasers. These lasers use mixtures of gases that don’t normally combine. However, when enough energy is applied, atoms of the two gases join together to form excited temporary molecules (excimers). The excited molecules release excess energy as light whose wavelength depends on the gases used.

KrF: the DUV dawn

The first DUV systems used excimer lasers based on a combination of two elements: krypton and fluorine. These krypton-fluoride (KrF) lasers produce light with a wavelength of 248 nanometers (nm). 150 nm KrF systems shrank feature sizes from the 280 nm that was possible with previous i-line systems. Modern KrF systems can now produce features down to 80 nm.

Going deeper with ArF

Going even further into the UV spectrum, the next generation of DUV lithography systems use argon-fluoride (ArF) excimer lasers that produce light with a wavelength of 193 nm. This enabled features sizes of 38 nm to be printed.

Creating EUV light

EUV lithography, a technology entirely unique to ASML, uses light with a wavelength of 13.5 nanometers. This wavelength is more than 14 times shorter than DUV light.

EUV light occurs naturally in outer space. But to make EUV lithography possible, we needed to engineer a way to create such light within a system. So, we developed a radically new approach to generating light for lithography.

In our laser-produced plasma (LPP) source, molten tin droplets of around 25 microns in diameter are ejected from a generator at 70 meters per second. As they fall, the droplets are hit first by a low-intensity laser pulse that flattens them into a pancake shape. Then a more powerful laser pulse vaporizes the flattened droplet to create a plasma that emits EUV light. To produce enough light to manufacture microchips, this process is repeated 50,000 times every second.

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lithography principles

The science behind the chip
The Rayleigh creationRead moreLearn the equation that determines just how small the transistors on a microchip can be.
Measuring accuracyRead moreASML systems rely on data from sensors as well as diffraction-based and electron beam measurements to optimize chip production.
Pushing k1 furtherRead moreASML is pushing the fundamental physical concepts about how light interacts with matter to their absolute limit.

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All about light and lasers in lithography (10)EUV lithography systems

Providing highest resolution in high-volume manufacturing, ASML’s extreme ultraviolet lithography machines are pushing Moore’s Law forward.

All about light and lasers in lithography (11)DUV lithography systems

ASML's deep ultraviolet (DUV) lithography systems dive deep into the UV spectrum to print the tiny features that form the basis of the microchip.

All about light and lasers in lithography (12)Metrology & inspection systems

Delivering speed and accuracy, our metrology and inspection portfolio covers every step manufacturing processes, from R&D to mass production.

All about light and lasers in lithography (13)Computational lithography

ASML's industry-leading computational lithography products enable accurate lithography simulations that help to improve chip yield and quality.

All about light and lasers in lithography (2024)

FAQs

How are lasers used in lithography? ›

Laser interference lithography is a technique that takes advantage of the periodicity of the interference pattern between two or more light (laser) waves, using this as a way to expose a photoresist (similar to optical lithography).

What is the light source for lithography? ›

Mercury lamps: from blue to UV

When ASML was founded, the state-of-the-art light source for lithography was the mercury vapor lamp. This generates light by passing electricity through a bulb that contains mercury. The current heats the mercury until it becomes a plasma that emits light of various wavelengths.

What is the wavelength of light in lithography? ›

The commonly used deep ultraviolet excimer lasers in lithography systems are the krypton fluoride (KrF) laser at 248 nm wavelength and the argon fluoride laser (ArF) at 193 nm wavelength. The primary manufacturers of excimer laser light sources in the 1980s were Lambda Physik (now part of Coherent, Inc.)

What are the applications of laser in photolithography? ›

Since our lasers generate the light that photolithography scanners use to image patterns on silicon wafers, increased accuracy helps to create wafer improvements.

How does the laser printing process work? ›

First, the laser printer reads the electronic data that makes up the information or image that you want to print and beams this onto a photo-sensitive drum. The information on the drum is then transferred to paper using static electricity to position tiny particles of powdered toner in the correct pattern.

What is the principle of lithography? ›

A lithography (more formally known as 'photolithography') system is essentially a projection system. Light is projected through a blueprint of the pattern that will be printed (known as a 'mask' or 'reticle').

Why yellow light is used in lithography? ›

In a photolithographic environment, a so-called “yellow room,” there is usually a yellow light to prevent the initiation of a photoreaction of PR; this light is made by filtering the wavelength regions shorter than 500 nm and using only yellow emitting materials.

What laser is used in EUV? ›

Summary of key features
EUVArF immersion
Light sourceCO2 laser + Sn plasmaArF excimer laser
Wavelength bandwidth5.9%<0.16%
Secondary electrons produced by absorptionYesNo
OpticsReflective multilayers (~40% absorbing per mirror)Transmissive lenses
16 more rows

What are the components of lithography? ›

The lithography machine is a complex structural equipment, and its main components include several major parts which consists of the laser light source, the objective lens system, the table system, the mask table system, the mask transfer system, the silicon transfer system, and the exposure system.

What is the difference between EUV and VUV? ›

Vacuum ultraviolet comprises wavlengths between 200-nm and 10-nm. Extreme ultra-violet (euv) is simply a name for the shorter-wavelength section of the vacuum ultraviolet, usually that part of the vuv spectrum that is shorter than 120-nm.

What are the different types of lithography? ›

Technologies
Lithography typeMaterialsWrite method
Optical lithographyPhotoresistUV exposure
Electron beam lithographyPMMAE-beam exposure
Soft LithographyPDMSMechanical
Direct Write LithographyPhotoresist/PMMAMechanical

What is the limit of lithography? ›

The physical limit lithography is k1 = 0.25. Smaller critical dimension can be achieved by using a combination of smaller light wavelength and larger numerical aperture (NA), while pushing k1 as close as possible to the physical limit.

Are lasers used in lithography? ›

Laser lithography is a versatile technique for the creation of microstructures such as microelectromechanical systems (MEMS) and integrated circuits. It works on the same principles as photolithography but developments in laser technologies have meant that laser-based manufacturing has become increasingly popular.

Why UV light is used in photolithography? ›

By spin coating, the substrate is first coated with a thin film of photoresists. Using UV light, projected through a mask onto the photoresist film, the exposed area is changed and exposed or not exposed area can be selectively removed, leaving a pattern on the substrate [50,81,82].

Why do we use semiconductor lasers? ›

Semiconductor lasers offer numerous advantages, including their small size, high reliability, lightweight, low power consumption, and long lifespan. In addition, they operate on the low-voltage constant current mode, which reduces the likelihood of power failures, ensures safe operation, and lowers maintenance costs.

How is laser used in 3D printing? ›

SLS 3D printing uses a high-power laser to sinter small particles of polymer powder into a solid structure based on a 3D model. Printing: The powder is dispersed in a thin layer on top of a platform inside of the build chamber.

How are lasers used in material processing? ›

In general, the assortment of the laser materials processing comprises cutting, drilling, welding, surface hardening, alloying, cladding, rapid prototyping, laser-assisted forming, ablation, and shot peening.

How are lasers used with latent prints? ›

The laser beam is used to fluoresce certain properties of perspiration, body oils, and foreign substances in latent print residues. Detection occurs when residues absorb the laser light and re-emit it in wavelengths longer than the illuminating source.

How are lasers used in semiconductor manufacturing? ›

In the instance of deburring, semiconductor lasers use their thin and precise beam to remove excess material without damaging any of the product. On the other hand, removing coating for analyzing a defective mold also allows manufacturers to see a defect without disassembling and damaging the product.

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