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 limit 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 pre-production EUV machine, the NXE:3100, uses two different sources for EUV light. In the "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 second EUV source technology is called "laser-assisted discharge plasma" (LDP). LDP sources use a strong electrical current through a tin vapor to generate EUV photons.
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. EUV also has a credible path to a resolution of less than 10 nanometers.
What issues are still unsolved?
The fundamental technological hurdles have been overcome, but further progress is needed to bring EUV into high-volume production. ASML’s NXE:3100 EUV machine is a pre-production tool; chip makers will primarily use it to become experts in using the technology and to develop the right chip production processes for their fabs, while ASML and its partners continue to improve the technology for it to be ready for high-volume chip production.
For manufacturers to move on to high-volume manufacturing, EUV tools will have to operate at a higher throughput than the first systems offer. The main issue here is the power of the light source: more power means higher throughput. Mask and resist are additional areas where progress has been made but needs to continue.
What resolution has been achieved with EUV?
Lines and spaces of 24 nanometers were achieved on ASML’s Alpha Demo Tool in 2010. The NXE:3100 has printed lines and spaces of 13 nanometers in a single exposure, and it has also been shown to be capable of 9 nanometer resolution using spacer double patterning.
When will EUV ship?
EUV has already arrived in our customers’ fabs. All six NXE:3100s have been shipped. The fundamental technology works: The NXE:3100 shows resolution and overlay that are in line with what is required for manufacturing chips in volume. ASML’s customers are now exposing wafers to develop processes. As of the first quarter of 2013, the NXE:3100 systems have exposed more than 30,000 wafers at customer sites.
For the successor system, the NXE:3300B, we already have 11 orders. We are preparing the shipments and installations of the first two NXE:3300B EUV systems, which will happen in Q2 and Q3 2013. These systems will be used by customers to validate EUV lithography in preparation for its adoption in high-volume manufacturing.
How will EUV be introduced into volume chip production?
In the past, chip makers have tended to introduce new technology as they switch one from so-called manufacturing “node” to the next. (“Node” here refers to the production of chips with certain feature sizes, for example 32 nanometers or 22 nanometers, using a particular manufacturing technology.) Chip makers would convert all so-called "critical layers" — the layers on a chip that require the highest resolution and precision — to the new technology.
ASML expects chip makers to introduce EUV in a different, more gradual fashion. Chip makers are expected to use EUV for the most difficult of the critical layers first. When productivity increases — in other words, when EUV systems can process more wafers per hour or per day, making them more economical — additional layers will be converted to EUV.
This means that EUV and immersion lithography will co-exist in the production of the most advanced chips.
How many EUV systems has ASML sold?
Apart from the two prototype machines (see above), ASML had orders for six NXE:3100 systems, all of which have been shipped. ASML has received 11 orders for the following model, NXE:3300B.
Page updated on 2013-4-17 7:35