Abstract: In some examples, an exclusion ring locates a substrate on a substrate-support assembly in a processing chamber. An example exclusion ring comprises an inner edge portion to cover an edge of a substrate in the processing chamber and an outer edge portion to support the exclusion ring on the substrate support assembly in the processing chamber. The outer edge portion may include an outer edge of the exclusion ring. A separation zone extending between the inner edge portion and the outer edge of the exclusion ring includes an undercut in an undersurface of the exclusion ring. In some examples, a cooling gas is directed at the exclusion ring while the exclusion ring is located at a station or during an indexing operation performed by the exclusion ring within a processing tool.