• Calculate one-sigma relative EUV photon-counting noise from the expected detected photon count in an exposure or measurement element.
• Compare fabrication or device scenarios while holding coefficients and unit conventions constant.
• Check a hand calculation before moving to a higher-fidelity process, circuit, or TCAD model.

N is the Poisson mean, so an expected count may be fractional even though every observed count is an integer. Increasing N by a factor of four halves the relative one-sigma count fluctuation.

• The formula assumes independent Poisson photon arrivals. It is not a prediction of critical-dimension variation, line-edge roughness, resist stochastic defects, detector read noise, source drift, or total process variation; quantum efficiency must already be reflected in the detected count N.
• Use parameters measured for the same material, geometry, temperature, and operating regime whenever the result informs engineering work.

• EUV Photon Fluence to Dose

  Convert photon fluence to incident energy dose when you need mJ/cm² rather than the analytic relative count fluctuation.

• Poisson Distribution Sampler

  Generate discrete Poisson count samples for simulation instead of reporting only the analytic one-sigma percentage.