Direct Measurement of 185 nm Radiation from Low-Pressure Mercury Lamps Using Diamond-Based Vacuum Ultraviolet Sensors

We present experimental results that show the importance of the direct measurement of the irradiance of 185 nm radiation from low-pressure mercury (Hg) lamps in vacuum ultraviolet (VUV)/O3 surface dry cleaning. It was found that the contact angles of water droplets on glass substrates can be correlated with the accumulated irradiance of the 185 nm radiation, not that from the 254 nm radiation that is conventionally monitored for the dry cleaning process control. Because the diamond-based VUV sensors are sensitive only to the 185 nm radiation, they could be a useful monitoring tool for controlling the VUV dry cleaning process in which low-pressure Hg lamps are used.