NOVELTY - The method involves mounting (S1) a glass substrate in substrate holding unit arranged in interior of processing chamber. The interior of chamber is exhausted (S2). The inert gas selected from nitrogen, argon, and helium is supplied (S3) from the substrate holding surface side of the substrate holding unit to chamber interior. The process gas such as hydrogen fluoride gas is supplied (S4) on the processing chamber interior. The supply of the inert gas to the processing chamber interior is stopped (S8), after completion of etching (S6) of substrate using process gas.    USE - Method for processing surface of glass substrate (claimed) for film silicon solar battery used for generating electric power.    ADVANTAGE - since the inert gas is supplied to the processing chamber interior from the substrate holding surface side of the substrate holding unit, the wrapping of inert gas to the back surface of the substrate is suppressed. Hence, the need of additional process to be performed in the back surface of substrate is eliminated. Since the inert gas supplied to the processing chamber interior is selected from nitrogen, argon, and helium, the manufacturing cost of the substrate is reduced. The temperature fall of the substrate stage caused by the flow of inert gas through the inner surface of substrate holding unit is suppressed, thus the deterioration of etching distribution in glass substrate is prevented.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a substrate surface processing apparatus.    DESCRIPTION OF DRAWING(S) - The drawing shows the flowchart illustrating process of processing substrate surface. (Drawing includes non-English language text)    Step for mounting glass substrate in substrate holding unit (S1)    Step for exhausting interior of processing chamber (S2)    Step for supplying inert gas to processing chamber interior (S3)    Step for supplying process gas to processing chamber interior (S4)    Step for etching substrate (S6)    Step for stopping supply of inert gas to processing chamber interior (S8)