To ensure that this range can be achieved during reactive pulsed magnetron sputtering on the present coating system, the process pressure is initially determined at different process gas settings and constant reactive gas flow (Table 2). The supply of argon and oxygen combined with the power control of the vacuum pumping system affects the final chamber pressure. For a first rough selection, an extra oxygen addition of 70 ml/min has been chosen. This acted as an initial guess for the choice of argon flow. In the real sputtering process, deviations are to be expected due to getter processes of the titanium atomization and the subsequently selected operating point. Table 2 shows the results of this experiment at constant addition of 70 ml/min oxygen and under variation of the argon flow. Here, the pure process pressure was recorded without the sputtering process being in progress. The turbomolecular pump was kept at a constant 60 % power. The argon flow was varied from 100 ml/min in 20 ml/min steps up to a maximum of 240 ml/min. Possible deviations in the real process were accepted at this point and the determination at this point was only used to generate suitable changes in the process pressure via the control of the argon flow. As an approach, the real experiments will proceed from lower range of process pressure to higher range process pressure.
Table 2: Determination of the absolute process pressure