Extreme ultraviolet lithography (EUVL) is a leading lithography technology for the next generation of semiconductor chips. Due to the lack of any useable common membrane pellicles, different approaches have to be considered in order to protect the EUV photomasks from particle contamination during all handling steps, i.e. during shipping and storage at atmospheric pressure as well as during exposure in dedicated lithography tools at low pressure (e.g. 50 mTorr). In this manuscript we present the evolution of schemes for protecting the very valuable EUVL masks from nanoparticle contamination. The proposed protection schemes are (1) maintaining the critical mask surface upside down to avoid gravitational settling of particles onto the mask; (2) use of a cover plate to reduce the volume from where particles might reach the surface; (3) apply thermal and/or electrical gradient to expose particles to a repelling thermophoretic and/or electrophoretic force and (4) use of a particle trap, surrounding the mask.
Bibliographical noteFunding Information:
This research is supported by Intel Corporation. The financial and technical support is gratefully acknowledged. The authors would like to thank Dr. Kevin Orvek and Dr. Arun Ramamoorthy for very fruitful discussions.
- EUVL mask
- Nanoparticle contamination