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