The invention provides an apparatus for excluding unwanted deposition at the edge of a substrate which prevents excess purge gas from flowing over the surface of the substrate at the region adjacent a notch on a substrate. Another aspect of the invention provides a wider purge gas channel that prevents excess purge gas from flowing over the surface of the substrate. Still another aspect of the present invention provides a purge gas guide that includes a notch therein to prevent excess purge gas from adversely affecting deposition at the vicinity of the substrate notch.