UV NIL shows excellent resolution capability with remarkable low line edge roughness, and has been attracting pioneers in the industry who were searching for the finest patterns.
We have been focused on the resolution improvement in mask making, and with a 100keV acceleration voltage spot beam EB writer process, we have achieved down to 16nm resolution, and have established a mask making process to meet the requirements of the pioneers. Usually such masks needed just a small field (several hundred microns square or so).
At the same time, UV NIL exploration has reached the step of feasibility study for mass production, and full chip field masks have been required, though the resolution demand is not as tough as for the extremely advanced usage mentioned above. The 100kV EB writers are adopting spot beams to generate the pattern and have a fatally low throughput if we need full chip writing. So for full chip masks, we have started the adoption of 50keV variable shaped beam (VSB) EB writers, which are used in current 4X photomask manufacturing
In this paper, we will show latest results both with the 100kV spot beam writer and the 50keV VSB EB writers.
With the 100kV spot beam writer, we achieved 16nm resolution, but found that to achieve further improvement, an innovation in pattern generation method or material would be inevitable.
With the 50kV VSB writers, we could generate full chip pattern in a reasonable time, and by choosing the right patterning material and process, we could achieve resolution down to 32nm. Our initial results of 32nm class NIL masks with full chip field size will be shown and resolution improvement plan to further technology nodes will be discussed.
Eventually, NIL is coming closer to production stage. We will also start the discussion about the infrastructures necessary for NIL mask manufacturing in this paper.