Abstract: In accordance with some embodiments described herein, a system for processing substrates includes two or more process modules, a substrate handling robot, a load lock chamber, and a transverse substrate handler. The transverse substrate handler includes mobile transverse chambers configured to convey substrates to process modules, wherein each mobile transverse chamber is configured to maintain a specified gas condition during the conveyance of the substrates. The transverse substrate handler further includes a rail for supporting the mobile transverse chambers, wherein the rail is positioned adjacent to entry of the process modules, and drive systems for moving the mobile transverse chambers on the rail.