| 摘要 |
PURPOSE:To foreknow the displacement of an oscillation wavelength and the deterioration of gas in a cavity by always measuring a wavelength distribution by providing a light source for generating an injected and synchronized laser light, and means for monitoring the spectral purity of the laser light. CONSTITUTION:A light source 1 for generating an injected and synchronized laser light and means 7 for monitoring the spectral purity of a laser light are provided. For example, a laser light irradiated from an excimer laser 1 is partly branched by a beam splitter 6. The branched laser light is incident to a locking monitor 7, and its locking efficiency (deviation) at this time is measured. When the measured value is lower than the minimum locking efficiency obtained for a sufficient resolution contrast, a controller 8 for controlling an exposure and gas exchange stops exposing in cooperation to execute gas exchange. Thus, it is always exposed by a laser light narrowed in its band in sufficiently high locking efficiency to improve the yield of manufacturing a semiconductor. |
