Methods and apparatuses are disclosed for rinsing the interface area of a liquid and air boundary after a substrate cleaning process using gas barrier. In some embodiments, a protective chuck having an inner gas ring and an outer liquid ring can be used to clean the area under the edge of the protective chuck. A gas flowing outward from the gas ring can enable a liquid to flow outward from the liquid ring, rinsing the outer portion of the protective chuck. The interface rinsing process can enable combinatorial processing of a substrate, providing multiple isolated processing regions on a single substrate with different material and processing conditions.