We developed radical beam sources with beam diameters larger than 100 mm intending to increase the productivity for thin film processes. Radical species were generated by using inductively coupled plasma generators driven by a RF (13.56 MHz) power supply. The relative density of oxygen radical was evaluated by OES (optical emission spectroscopy) peak at 845 nm, which is related to oxygen radiation from 3p3P to 3s3S, and the absolute density by Ag oxidization. The properties of the radical source depend strongly on the shape and volume of the plasma chamber and the configuration of the RF antenna. The maximum oxygen radical density is 1.24 x 10(15) atoms/cm(2) s at 100 mm from the end of beam source. It is two orders of magnitude higher than the ion density.