High rate reactive sputtering process control

Abstract Reactive sputtering is usually a slow process because the reactive gas interacts with the target, and in this poisoned state the deposition rate drops off. Pulsing the reactive gas led to improvements in the reactive deposition rate. At fast pulsing rates (0.2 s on, 0.2 s off), the reactive deposition rate for TiN is almost the same as that for metallic titanium, but control of the process is difficult. Implementation of a closed-loop feedback control system using the nitrogen peak height (partial pressure) from a mass spectrometer as the control signal to the reactive gas mass flow controller brought the process under control and also removed the need for pulsing. The closed-loop control system is not dependent on the sputtering system pumping throughput, and it has such good control that it can move up and down the knee of the hysteresis curve without the target becoming fully poisoned. Multiple gases can also be controlled, and using a derivative of this process it is possible to compensate for the deleterious effects of water vapor outgassing during the coating run.