Abstract: A method of measuring the overlay offset of a resist pattern formed on a semiconductor wafer is disclosed. An aligner outputs wafer-by-wafer measured alignment data. A scattering of the wafer-by-wafer alignment data is calculated. If the scattering is greater than a preselected value, all the wafers of a lot brought to a measuring step are tested. If the scattering is smaller than the preselected value, only sample wafers are tested. Whether or not sampling should be effected is automatically determined.

Abstract: A position detecting method of detecting the position of a position-detected object through analysis of the detected signal waveform obtained by detecting a reflected scattered light of a laser beam applied to the position-detected object, comprises a step of calculating an approximate line for approximating a base level on the basis of the portion corresponding to the area other than the alignment mark in the detected signal waveform, a step of calculating a specified straight line on the basis of the points on the detected signal waveform at each slice level obtained by scanning the portion corresponding to the alignment mark in the detected signal waveform at a plurality of slice levels, and a step of detecting the position of the alignment mark by the use of the approximate line for the base level and the specified straight line.

Abstract: A sensor for detecting the end point of etching is secured to a wafer chuck and a light projector and light receiver of an infrared photosensor which is used as the sensor for detecting the end point for aluminum etching rotates in synchronization with the rotation of a wafer during the etching process and the end point of etching is judged by a judgement circuit which receives a signal from the sensor for detecting the etching end point. In a spin etcher for the wafer, the sensor constantly monitors the same location on the wafer and thus prevents misjudgment of the end point of etching by an unstable waveform of the end-point detection signal.