Dr Stefan Bäumer
- System architecture
- Optical design
- Optical Metrology
- Micro- optics
We have studied the benefit of using soft X-ray wavelengths (10-40 nm) and the benefit to use phase information compared to the current use of intensity information. The conclusion was that using phase information only helps when the roughness of the substrate is more than being found in practice.
The use of soft X-ray wavelengths increases the relative measurement signal from a particle. The maximum gain however is limited by the increased transparency of particles at shorter wavelengths. The main parameter in the measurement time is the available source power. The non-coherent EUV sources that have been developed as source for the EUV scanners now have the potential to provide enough photons.
The use of a non coherent EUV source to scan blanks for ≤10 nm particles has the benefit of the improved contrast of the small particles, enabling to reduce the lower limit in particle sizes that can be detected, compared to the current systems operating at a wavelength of 193 nm.
No tests have been performed, but could be scheduled when a new high power EUV source becomes available at TNO as part of the EBL2 test set-up.
Detection of 10 nm PSL particles on a smooth silicon surface (150 × 150 mm), with less than 1% particles missed and less than 10 false positives. This all within half a day.