NOVELTY - The method involves loading substrates into a respective mobile chamber i.e. mobile transverse chamber (112), of a set of mobile chambers, where the mobile chambers are movable on a rail (114) positioned adjacent to a set of process modules (150, 152-1-152-5). The respective mobile chamber is moved along the rail. The respective mobile chamber is docked to a respective process module of the set of process modules. One of the substrates is conveyed from the respective mobile chamber to the respective process module. The respective mobile chamber is heated.    USE - Method for transferring a substrate e.g. photovoltaic substrate such as silicon substrate, glass substrate and metal plate, to a process module such as chemical vapor deposition chamber (CVD), plasma enhanced chemical vapor deposition (PECVD) chamber, atomic layer deposition (ALD) chamber, etching chamber, physical vapor deposition (PVD) chamber, annealing furnace, rapid thermal annealing (RTP) furnace, atmospheric pressure CVD chamber (APCVD), and evaporative coating chamber, during fabrication of semiconductor, flat panel display, and multi junction and single junction photovoltaic (PV) or tandem or multiple junction solar cell or single junction solar cells in a semiconductor industry, a solar industry and a photovoltaic industry.    ADVANTAGE - The method enables providing significant flexibility with respect to processing of large substrates, thus enabling complicated process recipes to be carried out all in one integrated system to enable parallel processing of substrates which require both long processing time and short processing time. The mobile transverse chamber can move between multiple process modules and conveys the substrates to one of the process modules while maintaining a desired gas environment. The mobile transverse chamber can independently maintain a desired gas condition during movement between the process modules and during conveyance of the substrates to the process modules. The method enables employing stacked process modules with associated stacked transverse substrate handlers, thus increasing throughput of the process and decreasing processing time.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a system for processing substrates, comprising mobile chambers.    DESCRIPTION OF DRAWING(S) - The drawing shows a front perspective view of a system for processing substrates.    Transverse substrate handler (110)    Mobile transverse chamber (112)    Rail (114)    Load lock chamber (120)    Entrance slits (122, 124)    Pre-heater (130)    Cool down racks (140)    Process modules (150, 152-1-152-5)