Anas Ghailane¹, Tommaso Sgrilli², Lara Maroto Diaz², Patricia Killen², Victor Bellido Gonzalez², Dermot Monaghan^2
1Avaluxe Coating Technology GmbH & Ko KG, Fürth, Germany
²Gencoa Ltd, Liverpool, United Kingdom
Gas control during reactive sputtering strongly influences the deposition rate and film properties of the compound being deposited. Reactive gases can trap the target in poisoned mode unless the partial pressures of the reactive gas(es) are individually monitored and controlled at high speed. The dynamics of a reactive sputtering system typically requires a closed-loop feedback speed of control in the 10’s of msec range. Active feedback control reacts and adjusts the reactive gas flow control valves within 1 msec. Depending upon gas line lengths and system size, the gas will then take typically between 10-100 msecs to enter the area in-front of the sputter target. With a closed loop feedback control time of <100msec most reactive processes can be maintained at high rate and with good control in the ‘transition’ region.
An important part of the control system is the choice of ‘sensor’ to provide feedback from the process of the effect of the reactive gas changes. The sensor signal is the ‘input’ to the controller and a fast and stable input signal makes achieving good control more straightforward.
The different control sensors of the Speedflo from Gencoa are explained and examples of depositions controlled by the Speedflo to achieve specific properties are presented.