REACTIVE MAGNETRON SPUTTERING OF SILICON TO PRODUCE SILICON-OXIDE

Well controlled silicon dioxide films with refractive index 1.400-1.49 0 have been deposited at rates of up to 0.85 nm/s from a 100 mm diamet er polycrystalline silicon cathode, sputtered at 200 W of 40 kHz recti fied AC power in a reactive environment. This frequency used with cont rol of the partial pressure of the oxygen in the system from the catho de potential has demonstrated an ability to reactively sputter silicon oxide of high quality. Stress/stoichiometry curves showed a peak in s tress at a refractive index of 1.460 indicating both a dense structure and optimised SiO2. We have demonstrated a pulsing system for the adm ission of oxygen into the silicon sputtering system which is under the control of a signal derived from the voltage appearing on the cathode when sputtering at constant power. Such a signal indicates the sputte ring status of the target as to the degree to which the cathode is cov ered with oxide i.e. poisoned. By varying combinations of reactive gas flow rate and switching levels, different film compositions could be reproducibly and reliably obtained, The growing films could be subject ed to a externally-varied degree of argon-ion bombardment with a simpl e modification of the geometry of the unbalanced magnetron used for th e sputtering. The amount of ion bombardment with such a system was als o a function of the argon sputtering pressure that was used, Increased argon-ion bombardment resulted in more compressive stress in the film that was produced.