LithographyMVP
Depth of focus
Estimate focus tolerance with DOF = k₂·λ/NA² — and see the resolution trade-off.
Inputs
Result
Enter values and calculate to see the result.
Interpretation
Enter a wavelength, numerical aperture, and k₂ factor.
Formula
DOF = k₂ · λ / NA²
Educational, scalar estimate.
Variables
| Symbol | Variable | Unit |
|---|---|---|
| DOF | Depth of focus | m (shown as nm) |
| k₂ | Process factor | dimensionless |
| λ | Exposure wavelength | m |
| NA | Numerical aperture | dimensionless |
Assumptions & validity
This tool assumes:
- DOF = k₂·λ/NA² — first-order scalar optics only.
- NA appears squared, so focus margin falls fast as NA rises.
- Real usable focus is reduced by wafer non-flatness and topography.
Worked example
λ = 193 nm, NA = 1.35, k₂ = 0.5.
DOF = 0.5 × 193 nm / 1.35² ≈ 53 nm