NOVELTY - The door (219) comprises a reflective body arranged between two cover plates of transparent material and configured to reflect light and heat energy into each of the first and second substrate processing modules. The door is: arranged between the first and second substrate processing modules coupled to one another in a linear arrangement; and selectively movable, via an actuator coupled to the door, between an open position that fluidly couples the first and second substrate processing modules to a closed position that isolates the first substrate processing module from the second module.    USE - The door is useful in an inline substrate processing tool (claimed) such as cluster substrate processing tool and indexed inline substrate processing tool that is useful for epitaxial silicon deposition in a solar cell fabrication process, where the door is a gate barrier.    ADVANTAGE - The energy and cost efficient inline substrate processing tool allows high precursor utilization, provides simple automation, and has a relatively simple reactor design having high throughput and process quality, flexibility and simple manufacturability.    DETAILED DESCRIPTION - The door (219) comprises a reflective body arranged between two cover plates of transparent material and configured to reflect light and heat energy into each of the first and second substrate processing modules. The door is: arranged between the first and second substrate processing modules coupled to one another in a linear arrangement; and selectively movable, via an actuator coupled to the door, between an open position that fluidly couples the first and second substrate processing modules to a closed position that isolates the first substrate processing module from the second substrate processing module. The door, when in the closed position, forms a seal with the first and second substrate processing modules that prevents cross contamination or mixing of process gases between the first and second substrate processing modules. The reflective body is fabricated from one of a reflective material or a non-reflective material coated with a reflective coating. An INDEPENDENT CLAIM is included for an inline substrate processing tool.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic cross sectional view of modules and associated doors of a substrate processing tool.    Enclosure (202)    Window (214)    Door (219)    Transparent quartz plates (240)    Sealing surface. (250)