METHOD FOR MEASURING A FOCUS DRIFT OF AN EXPOSURE APPARATUS

摘要

PURPOSE: A method for measuring a focus drift of an exposure apparatus is provided to reduce the time needed to measure the focus drift, by forming an overlay key for the focus drift in a scribe line of a semiconductor substrate having a real pattern, and by automatically measuring the focus drift in a real time through an overlay degree measurement using an overlay measuring system. CONSTITUTION: An overlay key for measuring a focus drift is formed in a scribe line of a chip. An overlay degree of the overlay key for measuring the focus drift is measured by an overlay measuring system. The focus drift is measured based upon the measured overlay degree. The measured focus drift degree is compared with a drift scope in a specification to determine whether to perform a process further.