A chemical vapor deposition reactor and a method of wafer processing are provided. The reactor can include a reaction chamber having an interior and an entry port for insertion and removal of substrates, a gas inlet manifold communicating with the interior of the chamber for admitting process gasses to form a deposit on substrates held within the interior, a shutter mounted to the chamber, and one or more cleaning elements mounted within the chamber. The shutter can be movable between (i) a run position in which the cleaning elements are remote from the exhaust channel and (ii) a cleaning position in which the one or more cleaning elements engage with the shutter so that the cleaning elements remove deposited particles from the shutter upon movement of the shutter to the cleaning position.