In recent years, Raman spectrometry devices, in which spectrometry is performed for Raman scattered light, have been widely used (Patent literature 1). For example, in the evaluation of a manufacturing process for semiconductor devices such as Si, a stress is measured by using a Raman microscope. The stress is obtained based on the peak position(s) of a Raman spectrum. To obtain a stress in the order of 100 MPa, it is necessary to determine the peak position with relatively high accuracy, e.g., accuracy in the order of 0.1 cm−1. In order to determine the peak position without being affected by fluctuations in the room temperature and the like, a method using an argon laser plasma line as a reference light is disclosed (Patent literature 2).
The configuration of Patent literature 2 is explained with reference to FIG. 8, Laser light emitted from a laser light source 201 is expanded by a beam expander 202. Then, the laser light passes through a half mirror 203 and enters an objective lens 204. The objective lens 204 concentrates the laser light on a measurement sample 221. Then, Raman scattered light generated on the measurement sample 221 is incident on the half mirror 203 through the objective lens 204. The half mirror 203 reflects the Raman scattered light toward a lens 205. The lens 205 concentrates the Raman scattered light onto a slit 206 of a spectroscope 207. Then, the Raman scattered light, which has passed through the slit 206, is dispersed by the spectroscope 207 and detected by a CCD detector 208, in this way, it is possible to measure a Raman spectrum. Then, the temperature is obtained based on the peak position of the Raman spectrum.
However, in this method, it is necessary to use a relatively large argon laser, and thus causing a problem that downsizing of the apparatus is very difficult. As another method, a method for obtaining reference light by splitting laser light is disclosed (Patent literature 3). In this method, the peak position is obtained by using a reference light. Further, the method uses shutters that are used to block the exciting light and the reference light respectively.