Extreme ultraviolet lithography

Extreme ultraviolet lithography, or EUV, is a specialized technique used in the manufacture of semiconductor chips used in cell phones, cars, and many other electronic devices. Semiconductor chips—also known as microchips or simply chips—function as the brain of electronic devices, controlling their various functions. The EUV process uses ultraviolet light to pattern very fine circuit features on silicon wafers. This allows manufacturers to put more information on chips and make them smaller. Smaller chips enable manufacturers to make smaller devices and fit more chips into devices to provide additional functions.

Background

Ultraviolet, or UV, refers to a type of electromagnetic radiation with a very short wavelength and high frequency. It is generated by the sun and some artificial light sources, such as tanning beds and arc welders. This form of light energy cannot be seen or detected by other human senses, and too much of it can be harmful. Short-term overexposure to UV light causes sunburns. Long-term overexposure is a known factor in premature skin aging and skin cancer, as well as some forms of blindness.

Lithography is a technique that was used to create art, long before it became part of the manufacture of electronic microchips. It is a process for making prints in which the creator uses a flat surface, such as a stone or metal plate, that is treated with a substance that helps form the design. The substance—in art, it is often an oil-based product—creates a mask that protects part of the flat surface from paint or ink while allowing the paint or ink to coat the rest of it. This is similar to how someone painting a room uses painter’s tape—which was originally called masking tape—to protect areas that are not to be painted and create straight lines or other patterns. EUV lithography uses a reflective substance as the mask and ultraviolet light in place of the paint or ink.

Prior to the development of the integrated circuit in the late 1950s, electronic devices used a variety of larger, bulkier technologies. For example, early radios and televisions had vacuum tubes, or glass tubes that controlled the flow of electricity by means of electrodes contained within the tube’s vacuum chamber. Early televisions, radios, and computers used these; the vacuum tubes for one computer built in the 1940s required an entire building.

Then, in the late 1940s, the transistor was invented. Transistors were much smaller semiconductor devices that controlled and switched electronic signals. They did not require heavy glass vacuum tubes, which enabled the devices that used them to be much smaller and more compact. Among the first uses for transistors were in portable radios and calculators. The development of microchips shrank the size of these electronic brains even further, until technology reached the point where many cell phones contain radios, calculators, cameras, and computers—plus phones—in a pocket-sized format.

Overview

EUV lithography represents a significant improvement over previous lithography processes used to produce chips. Older technology used light measuring 193 nanometers to expose circuit patterns during chip manufacturing. The EUV technology uses ultraviolet light’s extremely short wavelength of 13.5 nanometers. As a result, the etchings created by EUV are much finer, enabling more of this to be fitted onto a chip. This means the chips are not only faster and more powerful than their predecessors but smaller as well. A newer form of the technology, called High-NA (high numerical aperture) EUV, uses improved optics to create even smaller circuit features.

The multistep EUV process begins with applying light-reactive chemicals to a silicon chip. Portions of this chip are also treated with a reflective mask that deflects light away from the masked portions of the chip. The chip is then placed in a high-vacuum chamber because ultraviolet light is easily absorbed by anything near it, including air. The vacuum, combined with specialized mirrors, helps to focus the EUV light.

Next, a carbon dioxide laser is fired at a stream of microscopically small droplets of molten tin that fall at the rate of 50,000 per second. This creates plasma that generates ultraviolet light at the 13.5-nanometer wavelength necessary for the process to work. The EUV light is projected onto the treated wafer through an optical system that uses specialized multilayer mirrors and a reflective mask. This focuses the EUV light into a very fine beam that exposes the unmasked areas of the light-sensitive coating. The beam is focused with extreme accuracy; it would be the equivalent of shining a flashlight from Earth and illuminating something the size of a coin on the moon.

History

Research into EUV technology began in the 1980s. Researchers in several countries, including the United States, the Netherlands, and Japan, experimented with combining soft x-ray technology with the lithography process and devised the earliest form of the EUV process. In 2001, ASML Holdings, a Dutch multinational corporation founded in the 1980s, established a department within the company to begin developing a prototype device to use EUV lithography to make chips. The first customer-ready prototypes, called Alpha Demo Tools, were shipped to research facilities in the United States and Belgium in 2006.

The specialized manufacturing process requires a cleanroom, or specialized facility with filtration and cleaning systems to keep the creation of airborne particles and other contaminants to an absolute minimum. In 2007, ASML began construction on the first cleanroom dedicated to EUV lithography. Three years later, an Asian research facility received its first research and development model of an EUV lithography device called the NXE:3100.

As the value of EUV lithography in the chip making process came to be known, ASML partnered with chip manufacturers in a co-investment program. In 2012, companies such as Intel and Samsung made a five-year financial commitment to develop EUV technology and gained equity in ASML. The following year, these companies received ASML’s NXE:3300B EUV lithography system. Additional models were released as the technology was refined, all developed and manufactured by ASML. Mass production of chips using the technology in consumer devices began in 2019. ASML remained the only source of EUV lithography equipment throughout that time. The technology became an important tool for manufacturing many of the world's most advanced semiconductor chips.

According to Grand View Research, the extreme ultraviolet lithography market in the United States was about $9.42 billion in 2023 and was expected to grow at a compound annual growth rate of 17.3 percent from 2024 to 2030. This growth was fueled by the demand for small, efficient semiconductor devices in consumer electronics, which have decreased in size. Demand for chips used in artificial-intelligence systems also contributed to growth in the EUV lithography market.

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