Characterization of an Ultraviolet and a Vacuum-Ultraviolet Irradiance Meter with Synchrotron Radiation
Ping-Shine Shaw, R Gupta, Keith R. Lykke
We have constructed and characterized a simple probe that is suitable for accurate measurements of irradiance in the ultraviolet (UV) to vacuum UV spectral range. The irradiance meter consists of a PtSi detector located behind a precision 5 nm aperture. The irradiance meter was characterized at various wavelengths ranging from 157 nm to 325 nm, encompassing many of the important industrial application wavelengths, using the continuously tunable synchrotron radiation from SURF III. The calibration of the spectral irradiance responsivity was performed by scanning the irradiance meter with a probe beam and measuring the response of the irradiance meter on a grid with regular spacing. The angular response of the irradiance meter was also determined and shown to be suitable for applications such as photolithography. In addition, the stability of detectors at short wavelengths has been a major drawback in the past. We studied the radiation damage using a 157 nm excimer laser and found that the irradiance meter can endure more than 100 J/cm2 of 157 nm radiation before noticeable change occurs in its responsivity. Many industrial applications such as UV curing, photolithography, or semiconductor chip fabrication that require accurate measurement of the irradiance would benefit from having such a stable, accurate UV irradiance meter.