The teams of extreme ultraviolet photolithography (UVE) that manufactures the Dutch company ASML are extraordinarily sophisticated. In fact, they are those currently using TSMC, Samsung, Intel, Sy Hynix and Micron Technology for produce integrated avant -garde circuits. They are so complex that during the first phases of their design in the early 90s of the last century, ASML engineers They believed it was impossible.
However, everything changed in 1997. That year Jos Benschop, the leader of the research department, reassess whether UNVE technology was a viable option. After the first tests he realized that The German company Zeiss He was able to develop extraordinarily sophisticated mirrors that would be necessary to transport ultraviolet light. And he was not wrong. That was the real starting point of technology that has made it possible for our mobile phones and computers to have such advanced chips.
Zeiss’s feat arrived in the 90s
One of the most complex elements of UVE lithography machines is The ultraviolet light source. The company of American origin Cymer, although since 2013 it is not an independent company. That year ASML executives decided to buy it to accelerate the development of the technologies involved in UVE lithography. An interesting note: the ultraviolet light is responsible for transporting the geometric pattern described by the mask so that it can be transferred with a lot of precision to the surface of the silicon wafer.
Understanding what is the mask is simple: it is nothing other than a physical template that contains the design of the integrated circuit that is necessary to transfer to the Silicon wafer. In any case, there is another component without whose intervention It is not possible to carry out this crucial task. Other components, in plural, in reality, although all of them are of the same type. It is precisely the mirrors that Jos Benschop suspected in 1997 that Zeiss could produce.
The light of 11.4 nm was discarded because it forced to use beryllium in the mirrors and is a toxic chemical element
The role of the optical elements of this company in these lithography equipment is crucial. And it is because they are responsible for moving the UVE light with a wavelength of 13.5 nm from the source that is responsible for its emission to the mask contained in the geometric pattern that is necessary to translate into the silicon wafer. If the mirrors involved in the propagation of the UVE light are not manufactured with enormous precision the geometric pattern defined by the mask will be altered, and the chips will be damaged.
Interestingly, the choice of the wavelength of the UVE light used by these machines was a very delicate decision. Initially the engineers involved in their tuning had four possible options: 13.5 nm, 11.4 nm, 6.6 nm and 4.8 nm. These last two wavelengths were finally ruled out due to the limitations they imposed Organic photorestoning materials. The light of 11.4 Nm was also discarded because it forced to use beryllium in the mirrors, and is a toxic chemical element.
The wavelength of 13.5 Nm required to introduce molybdenum and silicon mirrors, but these elements do not pose any problem. This is the reason why UVE machines work with this light. In any case, this data clearly reflects the extraordinary level of precision with which it is necessary to manufacture the mirrors: Zeiss uses argon ions and other elements to polish layer per layer at the atomic level the mirrors, and then identifies and corrects the defects using a subnustric analysis technique. This last tool is capable of detecting defects with a lower precision than a nanometer (less than a millmillonieth part of a meter).
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Image | Zeiss
BIBLIOGRAPHY | ‘Focus: The Asml Way’by Marc Hijink
More information | Zeiss | Asianometry
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