Abstract: A platen supports a wafer during the deposition of tungsten, metal nitrides, other metals, and silicides in a chemicalvapor deposition reactor. A deposition control gas that includes a suitable inert gas such as argon or a mixture of inert and reactant gases such as argon and hydrogen is introduced through a restrictive opening into an ambient in the reactor. An exclusion guard aligned with the platen has an extension extending over a frontside peripheral region of the wafer. Deposition control gas is introduced under the exclusion guard extension and exits through a restrictive opening between the exclusion guard extension and a wafer frontside peripheral region. The restrictive opening provides a uniform pressure of deposition control gas at the edge and frontside of the wafer to prevent deposition on the wafer edge and backside.