READING METHOD FOR SERIAL CODE

PURPOSE:To omit a straight line reading mechanism and to minimize the reading time of serial codes by scanning the serial codes arrayed on a straight line is the direction of a prescribed circular arc and correcting the obtained data. CONSTITUTION:The serial bar codes 2 are arrayed on the back side of a semiconductor wafer 1 and then scanned and read at a fixed angular speed along a circle 3 concentrical to the circle of the wafer 1. In this case, the codes 2 set along the tangent of a circular arc so that the middle point of the code 2 serves as a contact with the circular arc. Then DELTAx=(r.DELTAtheta)Xcostheta is satisfied, where the width of each code component is referred to as DELTAx together with the radius of a circular arc 11 as (r), the angle secured between the code component measured by the scan in the circular arc direction and the center of the arc 11 as DELTAtheta, and the angle between the code component and the middle point of the code as theta respectively. Then the correction is applied so as to obtain the code data when a circular arc 12 is scanned in the straight line direction. In a circular arc scan mode a bar code reading sensor is set at a prescribed position distant from the rotational center by the radius (r) when a wafer is rotated for wafer positioning in production of a semiconductor.