Extreme Ultra Violet Lithography (EUVL) is one of promising candidates for next generation lithography, 32nm node
and beyond. Authors are developing EUV mask process targeting full field EUV exposure tool. Unlike the conventional
optical mask, EUV mask is reflective type mask. To reflect 13.5nm wavelength light, 40 pairs of Mo/Si multilayer
(ML) is used for reflective layer. Reflective layer is covered by capping layer. The capping layer protect reflective layer
from absorber etching, defect repair and environmental condition. Top of absorber layer is covered by low reflective
(LR) layer to achieve high contrast between the etched and not etched portion. Back side of EUV mask is covered by
conductive film for electrostatic chuck use. In this paper, we will report current process development status of EUV
mask for full field EUV exposure tool. Absorber patterning process including resist patterning and absorber etching
were developed. Thin resist use and small resist damage dry etching process achieved pattern resolution of 32nm node.
Defect inspection was also evaluated using DUV reticle inspection tool. Ta-based absorber on ruthenium (Ru) capped
ML blanks was used for this evaluation. Because, Ru material has high resistivity to absorber etching plasma, it enable
buffer layer less EUV mask structure. Ru also has better property on oxidation resistance compared to standard silicon
(Si) capping layer.
Extreme Ultra Violet Lithography (EUVL) is considered to be a major candidate for the Next Generation
Lithography. To achieve reflective optics, EUV mask consists of absorber layer, reflective multilayer (ML) with
protection capping layer. Buffer layer can be used for silicon capped EUV blanks to enhance the etch selectivity
against absorber etching.
It has been reported that Ruthenium (Ru) material has better property on oxidation resistance
compared to standard silicon (Si) capping layer. Ru capping layers have advantage for its high etch selectivity, which
enables buffer layer free EUV mask structure. However, thin Ru layers should be designed due to high EUV
This paper includes the evaluation of current process performance of Ta-based absorber process on Ru capped ML
blanks. It also includes resist patterning by EB writing, Ru capping layer etch effect as well as absorber patterning
with CD uniformity, linearity, Line Edge Roughness (LER) and selectivity between absorber and resist or Ru capping
layer. Inspection result is also included as a recent result.