The Fraunhofer Institute for Laser Technology ILT in Aachen and the Institute for Applied Optics and Precision Engineering IOF in Jena are developing lithographic techniques for manufacturing microchips with a thickness of just few atoms.
The research is being carried out as part of a project called ‘Beyond EUV’, which runs to the end of 2016. It is anticipated that the new chips could lead to even higher storage capacity for cloud applications and big data processes, as well as for mind-controlled prosthetic limbs or more personalised medicine.
EUV lithography is a technology that works by using extreme ultraviolet (EUV) radiation at a wavelength of 13.5nm, which is generated by evaporating a droplet of tin with a high-power laser. By harnessing the emitted EUV radiation, it is possible to produce structures with a size of 10nm or less.
Fraunhofer ILT scientists have been researching technology that uses radiation with a wavelength of 6.7nm. Instead of tin, they are working with targets made of gadolinium or terbium alloys, as these facilitate correspondingly shorter wavelengths.
EUV lithography functions use reflective optics, meaning the used mirrors have to meet extremely precise requirements. Currently, the thickness of mirror coatings must be correct to around 10 picometres - less than the diameter of an atom.
Every percentage point of reflectivity matters when generating EUV radiation. In the case of mirrors for 13nm radiation, it is possible to achieve a reflectivity of around 65 per cent using alternating films of silicon and molybdenum. With mirrors for 6.7nm radiation, experts from Fraunhofer IOF have developed special systems using lanthanum and boron compounds. Here, too, they are attempting to reach the theoretical limit of around 70 per cent.
As part of the research, the two Fraunhofer teams have developed a new optical system that characterises the EUV radiation source. This system enables factors such as light output to be measured to a high degree of spatial and spectral resolution. The output power of the radiation source is now enough to carry out trials on new mirror coatings or light-sensitive varnishes.
These new lithographic techniques will make it possible to produce structures with a thickness of just a few atoms. There are already lots of ideas for how to use integrated circuits formed from such structures: alongside even higher storage capacity for cloud applications and big data processes, they could also be used for mind-controlled prosthetic limbs or more personalised medicine.