DETECTOR OF WAVELENGTH ABNORMALITY OF NARROW BAND OSCILLATION EXCIMER LASER

摘要

PURPOSE:To detect multiwavelength oscillation securely by a detector with a simple constitution and avoid the degradation of resolution when an excimer laser is employed as a light source of contract projection aligner by a method wherein the output power and central wavelength power of the laser are detected and the abnormality of the spectrum wavelength is detected by observing whether the ratio of those powers is within an allowable range or not. CONSTITUTION:The ratio of the output power and central wavelength power of an excimer laser is calculated from the output of a detector 301 of an oscillation center wavelength and central wavelength power and the output of a power monitor 202 and the ratio is observed to detect whether side peaks are created or not. If the side peaks are detected, a CPU 203 generates a wavelength abnormality signal. The wavelength abnormality signal is transmitted to an aligner (not shown in the figure). With this constitution, the wavelength abnormality of the spectrum of the oscillated laser beam can be detected easily and with a high reliability and the degradation of resolution can be avoided.