| 摘要 |
PURPOSE:To reduce temporal change in a laser light source, by dividing the laser light source into monitoring application and discriminating application by using a half mirror, and correcting the laser light beam for discrimination by the laser light beam for monitoring. CONSTITUTION:A part of the laser beam, which has hit a half mirror 3f, is transmitted and converged into a photoelectric transducing element 6b by a convex lens. The photoelectrically transduced voltage b1 [v] is used for monitoring a laser light source. The laser light beam, which is reflected by the half mirror is diffused and reflected by a semiconductor wafer when the surface of the semiconductor wafer is irregular, and the reflected light beam is transduced into electric quantity by a photoelectric transducer element 6a through paths 3e, 2d, and 6a. The voltage a1 v, which is transduced by the photoelectric transducer element 6a, is used as data intactly. The degradation of the laser light source gives the effect to a1 v and b1 v under the same condition. The value of a1divided by b1 is not affected by the degradation of the laser light source but becomes the value, which is changed only by the state of the surface of the semiconductor wafer. When the computed result is used as concave and convex data of the wafer surface, erroneous recognition due to the degradation of the laser light source can be avoided. |
