Stephen Hsu, Senior Fellow at ASML

Stephen Hsu

Getting the best imaging out of lithography scanners

“Every crisis we face also presents an opportunity. It’s up to us how to investigate the problems involved and try to come up with solutions.”

Stephen Hsu has made significant contributions to the computational lithography software used by ASML customers to get the best imaging out of their DUV and EUV scanners.

Over the years, Stephen has contributed to resolution-enhancement techniques (RET), source-mask optimization (SMO) as well as optical proximity correction (OPC). He also teaches an advanced lithography short course internally at ASML and externally at SPIE, and mentors junior engineers.

Get to know Stephen
  • ASML employee since 2000

  • Named a Fellow in 2017

  • Named a Senior Fellow in 2022

  • Based in San Jose, United States

Key contributions

  • DUV, EUV and High-NA EUV source-mask optimization

  • EUV scanner wavefront matching

  • Published more than 100 technical papers on lithography and resolution enhancement techniques


Imaging physics, optimization algorithms, resolution enhancement techniques


Holds 52 US patents across 39 ASML patent families