Patent ID: 8825448

Claim:
A spectroscopic reflectometer for use with a sample, the spectroscopic reflectometer comprising: a head comprising: a light source; a photo-detector; and an internal reflection mechanism; and a reflectance calculation unit; wherein the light source is structured to project a measurement light the sample and introduce reflection light from the sample irradiated by the measurement light; the photo-detector is structured to detect an intensity of the reflection light, having its light receiving part placed in a position at which the reflection light introduced into the head arrives; the internal reflection mechanism has a constant light reflectance and is placed in a position at which a part of the measurement light arrives, and is structured such that the reflection light reflected by the internal reflection mechanism reaches the light receiving part of the photo-detector within the head; the reflectance calculation unit comprises a memory structured to store a first output value from the photo-detector, a second output value from the photo-detector, a third output value from the photo-detector, a fourth output value from the photo-detector, a fifth output value from the photo detector; and a sixth output value from the photo-detector; the first output value is an output value of the photo-detector in a state of substantially no light being introduced; the second output value that is an output value of the photo-detector when the sample is a dark sample that substantially reflects no light; the third output value is an output value of the photo-detector when a calibration sample of a known light reflectance is used as the sample; the fourth output value is an output value of the photo-detector in a state of substantially no light being introduced; the fifth output value is an output value of the photo-detector when the dark sample is used as the sample; and the sixth output value is an output value of the photo-detector when an inspection work to be measured is used as the sample; the photo-detector and the reflectance calculation unit are structured to measure and store the first output value, the second output value, and the third output value during a subordinate period in which variation in the output value of the photo-detector is substantially negligible; the photo-detector and the reflectance calculation unit are structured to measure and store the fourth output value, the fifth output value, and the sixth output value during a main measurement period in which variation in the output value of the photo-detector is substantially negligible; and the reflectance calculation unit comprises a processor structured to calculate light reflectance of the inspection work based on the first output value, the second output value, the third output value, the fourth output value, the fifth output value, and the sixth output value stored in the memory.