EUV InsightChoosing a zirconium filter thickness
Compare calculated transmission through freestanding zirconium films at 13.5 nm, with explicit density, interface and illumination assumptions.
A thickness choice should start with a transmission requirement and the conditions under which the filter will be used. The table below isolates one variable: the thickness of a single freestanding zirconium film.
A single-film comparison at 13.5 nm
These calculations use vacuum on both sides, density 6.52 g/cm³, normal incidence, unpolarized illumination and smooth interfaces. There is no silicon layer, oxide or supporting mesh. Each row is a separate calculation using the same optical constants.
| Zr thickness (nm) | Transmission (%) | Reflection (%) | Absorption (%) |
|---|---|---|---|
| 25 | 91.46 | 0.16 | 8.38 |
| 50 | 83.91 | 0.02 | 16.08 |
| 100 | 70.39 | 0.05 | 29.56 |
| 150 | 59.05 | 0.08 | 40.87 |
| 200 | 49.55 | 0.09 | 50.36 |
Choosing a thickness for your requirements
Compare the transmission column with your optical budget. A thinner modeled film can transmit more EUV, but this calculation does not establish mechanical strength, handling reliability or lifetime. Those requirements need their own evidence.
Also inspect the spectrum around the target wavelength. A value at 13.5 nm does not describe out-of-band rejection or a source with a broad emission spectrum.
Reproduce the calculation
- Open the 100 nm Zr example below.
- Keep the substrate disabled and the incidence angle at 0°.
- Change the layer thickness to one of the table values.
- Read the transmission at the 13.5 nm target.
If the physical filter has an oxide or additional layer, include it explicitly using appropriate optical data. Do not compensate for omitted structure by treating a fitted thickness as a direct thickness measurement.
Calculated examples use the bundled optical reference tables, not measured samples. Zr/Si/Mo example-data fingerprint: 92954053bf1c26ab. Assumptions and data sources.