Origin of particles during reactive sputtering of oxides using planar and cylindrical magnetrons

Particles generated during reactive magnetron sputtering cause defects in optical thin films, which may lead to losses in optical performance, pinholes, loss of adhesion, decreased laser-induced damage thresholds and many more negative effects. Therefore, it is important to reduce the particle contamination during the manufacturing process. In the present paper, the origin of particles during the deposition of various oxide films by midfrequency pulsed reactive magnetron sputtering was investigated. Several steps have been undertaken to decrease the particle contamination during the complete substrate handling procedure. It was found that conditioning of the vacuum chamber can help to decrease the defect level significantly. This level remains low for several hours of sputtering and increases after 100 hours of process time. Particle densities of SiO(2) films deposited with cylindrical and planar dual magnetrons at different process parameters as well as different positions underneath the target were compared. It was observed that the process power influences the particle density significantly in case of planar targets while cylindrical targets have no such strong dependence. In addition, the particle contamination caused by different cylindrical target materials was analyzed. No major differences in particle contamination of different cylindrical target types and materials were found.