Mask absorber development to enable next generation EUVL
In next generation EUV imaging for foundry N5 dimensions and beyond, inherent pitch and orientation dependent effects on wafer level will consume a significant part of the lithography budget using the current Ta based mask. Mask absorber optimization can mitigate these so called mask 3D effects [1 3] Last year at the SPIE Photomask and EUVL conference [4,5] EUV mask absorber change is recognized by the community as key enabler of next generation EUV lithography. Through rigorous lithographic simulations we have identified regions, based on the material optical properties and their gain in imaging performance compared to the reference Ta based absorber [6] In addition, we have established a mask absorber requirement test flow to validate the candidate material to the full mask supply chain. In this paper we discuss in more detail Te and Ru based alloys which cover these different improvement regions. Candidate materials are evaluated on film morphology, stability during combined hydrogen and EUV loading, and thermal and chemical durability. The EUV optical constants are measured by EUV reflectometry, and preliminary results of plasma etching are shown to enable patterning.
Photomask Japan