Step coverage in the vacuum deposition of thin metal films

Abstract

In the vacuum deposition of thin metal films the details of the film coverage over surface steps are an important consideration in many technological applications. A theory is presented which describes the relationship between the target (or emitter) and receiver (or substrate) geometry, which allows for the calculation of geometric shadowing effects between points on the receiver plane. The theory is used to formulate a computer simulation of the deposition of a film over a step on the receiver surface. The simulation has been applied to a particular case of low-voltage triode sputtering. The results are discussed in terms of the step geometry, position on the receiver table, and receiver-to-target distance. The calculations are compared with experimental observations. A generalization of the theory to other types of vacuum deposition is considered which includes extended target systems (such as conventional sputtering systems) and small target systems with substrate motion (such as electron beam deposition with planetary motion). The effects of substrate temperature are discussed.