Abstract: A cleaning end point detecting apparatus detects an end point of a cleaning process in which contamination attached to an inner wall of a reaction chamber is removed by introducing a cleaning gas into the chamber to produce a cluster cloud and detached particles. An irradiating unit irradiates a laser beam onto the cluster cloud and the detached particles within the reaction chamber to produce a scattered laser beam. A monitoring unit monitors the scattered laser beam as a two-dimensional image information. A judging unit judges the end point of the cleaning process on the basis of the two-dimensional image information. Preferably, the judging unit judges, as the end point of the cleaning process, a time instant when neither the detached particles nor the cluster cloud are detected on the basis of the two-dimensional image information.

Abstract: A method for processing a substrate includes the steps of determining an allowable margin of process condition such that a substrate is processed without forming particles, selecting a process condition of a substrate for a production process such that the process condition falls in the allowable margin in the production process, and carrying out a processing of the substrate in the production process at the selected process condition, wherein the step of determining the allowable margin includes the steps of introducing an optical beam to an atmosphere in which the substrate is processed in the step of determining the allowable margin, and detecting scattering of the optical beam.