The effect of target-substrate coupling on reactive direct current magnetron sputtering

Summary From a consideration of the reactive gas flow rates and of the reactive gas partial pressure a criterion for process stability in reactive direct current magnetron sputtering is derived. By a discussion of this stability criterion the methods of self-stabilization and stabilization through high pump speed are deduced. If the gas discharge is considered as a getter pump with a reactive gas pressure dependent pumping rate S Dis ( p R ), the stability criterion includes a term — d S Dis /d p R which describes the degiee of target-to-substrate coupling (TSC). From this the method of stabilization through reduction of TSC, i.e. through decoupling, is deduced. The relationship of process stability, TSC and film properties is discussed and exemplified by the system CrSi-O 2 . Coating of large areas and plasma-assisted deposition call for strong TSC, which may be contradictory to the stability criterion. An active closed-loop control circuit, e.g. using the plasma emission intensity signal (PEM control), has to be employed for process stabilization.