A semiconductor substrate processor includes a substrate transfer chamber and a plurality of substrate processing chambers connected therewith. An interfacial structure is received between at least one of the processing chambers and the transfer chamber. The interfacial structure includes a substantially non-metallic, thermally insulative mass of material interposed between the one processing chamber and the transfer chamber. The mass is of sufficient volume to effectively reduce heat transfer from the processing chamber to the transfer chamber than would otherwise occur in the absence of said mass of material. An interfacial structure includes a body having a substrate passageway extending therethrough. The passageway includes walls at least a portion of which are substantially metallic. The body includes material peripheral of the walls which is substantially non-metallic and thermally insulative. The substantially non-metallic material has mounting openings extending at least partially therein.