Atomic nitrogen generation system for reactive deposition of thin films

The atomic form of nitrogen may be very effective in the formation of nitrides in reactive thin film deposition. One of the compounds of great interest to the optoelectronic industry is gallium nitride, a potential material for manufacturing blue light emitting diodes and color displays. A system for the generation of atomic nitrogen at low gas flow and high efficiency, needed for reactive deposition of gallium nitride by the ICB technique, has been built. Its operation is based on the dissociation of molecular nitrogen in a microwave cavity at the frequency of 2.45 GHz. To prevent the high purity gas from becoming contaminated no electrodes come into contact with the plasma discharge. A method of measuring the effective yield of atomic nitrogen is also described. A high atomic nitrogen concentration of 1.2% at low gas flow has been achieved. The relationship between gas flow rate, dissociation efficiency, and the vacuum requirements of the deposition process is discussed.