ASML is the world's leading provider of lithography systems for the semiconductor industry. Headquartered in Veldhoven, the Netherlands, ASML employs more than 7,000 people.
What is EUV?
EUV stands for “extreme ultraviolet” and refers to the light source that is used in the lithography machine. The previous generation of lithography machines used light in the "deep ultraviolet" spectrum. Ultraviolet light has a shorter wavelength than visible light. With a wavelength of only 13.5 nanometers, EUV sits in the spectrum between visible light and X-ray.
Why do we need EUV?
For the past decades, the semiconductor industry has been driven by what is called “Moore’s Law”. It goes back to Intel co-founder Gordon Moore, who observed in the 1960s that the amount of transistors that could be fit on a chip of a given size at an acceptable cost doubled roughly every year. (He later revised the period to two years.)
The entire semiconductor industry operates to this model, which requires chip makers to pack transistors more tightly with every new generation of chips, shrinking the size of transistors. Smaller transistors mean that semiconductor lithography machines must be able to print finer features with every new generation of chips as well.
Since lithography is an optical technology, one of the things that limits the resolution of the equipment is the wavelength of the light that is used. Shortening the wavelength of the light means higher resolution and smaller features. Lithography machines have gone from using ultraviolet light with a wavelength of 365 nanometers to “deep ultraviolet” light of 248 nanometers and 193 nanometers, improving the resolution at every step. EUV is the next step, with light of a wavelength of 13.5 nanometers. (An analogy is painting: we use a smaller brush to paint the finer details)
What makes EUV so challenging?
The technological challenges that had to be overcome to make EUV a reality were enormous. ASML has spent as much R&D money on EUV as on the previous two generations (ArF dry and ArF immersion) combined.
To begin with, EUV photons are difficult to produce. ASML’s EUV systems use a "laser-produced plasma" (LPP) source: a high-energy laser fires on a microscopic droplet of molten tin and turns it into plasma, emitting EUV light, which then is focused into a beam.
The glass of a lens would immediately absorb the EUV photons, so the machine has to use mirrors instead. The mirrors must be extremely flat. If one of the mirrors were to be blown up to the size of Germany, the biggest bump would be less than 1 millimeter high. The mirrors are coated with hundreds of layers, which are as thin as 3 nanometers — about a dozen atoms. In fact, even air absorbs EUV light, so the exposure of the wafer must happen in a large vacuum chamber.
What are the benefits for chip makers?
The current lithography technology has been pushed further than many would have thought possible even five years ago, but this has come at the cost of increasing complexity and shrinking margins of error. The industry has had to reach deep into a bag of tricks to continue shrinking feature sizes. Double Patterning in particular is costly because it increases the amount of lithography exposures per wafer, and thus either reduces fab output or requires more equipment. With EUV, chip makers will return to the former situation in which they expose a critical layer in just one single step.
Page updated on 2014-9-30 15:55