EQUIVALENT-CIRCUIT MODEL FOR LARGE-AREA AC MAGNETRON SPUTTERING OF DIELECTRICS

Some important circuit considerations for ac reactive magnetron sputte ring of dielectrics are addressed. We start with a simplified circuit model of a discharge appropriate to the ultrasonic frequency range. Th e model predicts that a power supply with sufficient secondary leakage inductance acts as a constant current source. The model accurately re presents the wave form of the current observed in practice. A large sp ike observed on the rising edge of the voltage waveform is not predict ed by the model. Results are presented for reactive sputtering of sili con-dioxide thin films from cylindrical silicon targets employing a du al magnetron rotatable cathode powered with an sc power supply operati ng at about 30 kHz. Single layer SiO2 films were produced over a perio d of more than 150 h. The lateral film thickness variation was less th an +/-3% and refractive index stability was +/-0.004 at 545 nm. Sample s coated after 150 h of continuous cathode operation exhibited small d ensities of arc-related film inclusions. (C) 1997 Published by Elsevie r Science B.V.