A movable microchamber system with a gas curtain is disclosed. The microchamber system has a top member with a light-access feature and a stage assembly that supports a substrate to be processed. The stage assembly is disposed relative to the top member to define a microchamber and a peripheral microchamber gap. An inert gas is flowed into the peripheral microchamber gap to form the gas curtain just outside of the microchamber. The gas curtain substantially prevents reactive gas in the ambient environment from entering the microchamber when the stage assembly moves relative to the top member.