As photomask minimum feature size requirements continue to shrink, resist resolution limitations and their tradeoffs
with exposure dose are critical factors. Recently, nearly every node needs a new electron beam resist, customized for
exposure dose requirements while simultaneously meeting resolution specifications. Intel Mask Operations has an active
program focused on screening new electron beam resists and processes. We discuss the performance metrics we use to
evaluate materials and discuss the relative capabilities of the latest resists. We present fundamental resist metrics
(resolution, LER and dose) as well as manufacturing process sensitivities.
High resolution sub resolution assist features (SRAFs) are challenging to pattern, especially on photomasks with pattern
density variations and beam corrections. This paper presents analysis techniques of SRAF resist resolution performance
and manufacturing robustness. Electron beam proximity effects and their correction methods impact aerial image
quality. Resist resolution and LER depend strongly on the aerial image, and these effects will be looked at theoretically
and experimentally with CDSEM and reflected die-to-die inspection techniques. A quantitative understanding of
resolution process latitude is important in SRAF patterning, especially when one considers beam corrections that are
used to compensate for effects like electron fogging and etch loading.