Directed Evaporation for Step Coverage
Original Publication Date: 1987-Apr-01
Included in the Prior Art Database: 2005-Feb-01
Step coverage is a generic problem in physical vapor deposition which is ordinarily a line-of-sight process. Integrated circuits are becoming increasingly 3-dimensional as their complexity increases and there is a practical need to coat surfaces uniformly even when they have complicated topography. In the absence of other influence the thickness of a deposit depends on the cosine of the angle between the surface normal and the line joining the source and the substrate, as shown in Fig. 1. This geometrical feature imposes a limitation on the slope of steps which may be covered by evaporation onto a multilayer device and thus limits the density of components and the speed of the circuit as a whole. A portion of the atoms electron beam evaporated from a source are ionized.