DUV Lithography

A computer chip consists of billions of tiny switches sitting on a thin slice of silicon. These switches aren’t built individually; instead, they’re exposed onto the wafer like a photograph. To do this, a stencil bearing the desired pattern is placed into a machine and light is shone through it. The light hits a light-sensitive layer, and wherever it strikes, that layer changes chemically. DUV lithography uses ultraviolet light for this purpose, meaning light with a shorter wavelength than the human eye can see. DUV stands for “Deep Ultraviolet” and refers to wavelengths of 248 and 193 nanometers.

The workhorse of chip manufacturing

Nearly every chip made today is produced using DUV machines. This applies equally to automotive electronics, washing machine controllers, memory chips, and graphics cards. Even the most advanced processors go through dozens of DUV steps, because only the very finest layers require a more expensive technology. DUV is thus the foundation of the entire electronics industry, not merely a preliminary stage.

DUV is also economically significant because the market for these machines is extremely narrow. The Dutch company ASML is the leading manufacturer, alongside the Japanese firms Nikon and Canon. A single modern DUV system costs between 20 and 80 million euros, depending on configuration. A chip factory doesn’t need just one of these—it often needs several dozen.

Politically, DUV machines have regularly made the news in recent years. The United States and the Netherlands have restricted the export of the most powerful models to China. Older DUV systems, however, may still be purchased by China, which is why there is constant dispute over where exactly to draw the line.

From stencil to transistor

The light source is a laser operating with a gas mixture. At 248 nanometers, this is krypton and fluorine; at 193 nanometers, it’s argon and fluorine. This light passes through the mask, i.e., the stencil bearing the circuit pattern. A highly sophisticated lens system then shrinks the image, usually to a quarter of the mask’s size. This produces structures far smaller than anything visible to the naked eye.

Physically, a simple rule of thumb applies: the shorter the wavelength, the finer the detail. At some point, 193 nanometers became the limit. The industry got around this with two tricks. The first involves filling the gap between the lens and the wafer with pure water, which focuses the light more tightly. This technique is called immersion lithography.

The second trick is called multi-patterning: the same spot is exposed multiple times with offset patterns. Two coarse exposures together yield a finer result than a single one. However, this costs time and increases the error rate. For the finest layers of modern chips, the industry therefore relies on EUV lithography, which operates at a wavelength of just 13.5 nanometers. EUV machines, however, are considerably more expensive and complex, which is why DUV isn’t disappearing.

Where DUV shows up in headlines and devices

You practically never see a DUV machine directly, since it sits in the cleanrooms of chip factories in Taiwan, South Korea, Japan, the United States, or Germany. Indirectly, its output is found in every smartphone, every laptop, and every car of the past few decades. When chips become scarce, as during the supply crisis starting in 2020, it’s often due to a lack of capacity in precisely these machines.

In business news, you’ll usually encounter DUV via the name ASML. Reports on this company’s order intake, export approvals, or delivery times are considered an early indicator for the entire semiconductor industry. A common misconception is to consider DUV outdated. In fact, DUV still accounts for the largest share of all exposure steps worldwide, and new factories order both technologies side by side.