| 摘要 |
<p>A linearly polarized light comprised of two linearly polarized components that are orthogonal to each other, with split optical frequencies, is directed toward a film causing one of the optical polarization components to lag behind the other due to an increase in the optical path in the film for that component. A pair of detectors receives the beam reflected from the film layer and produces a measurement signal, and the beam prior to incidence on the film layer and generates a reference signal, respectively. The measurement signal and reference signal are analyzed by a phase detector for phase shift. The detected phase shift is then fed into a thickness calculator for film thickness results. A grating interferometer may be included with the heterodyne reflectometer system with a grating, which diffracts the reflected beam into zeroth- and first-order bands, which are then detected by separate detectors. A detector receives the zeroth-order beam and generates another measurement signal. Another detector receives the first-order beam and generates a grating signal. The measurement signal from the grating and reference signal may be analyzed by a phase detector for phase shift, which is related to the thickness of the film. Additionally, the zeroth-order beam measurement signal is analyzed with the grating signal by a phase detector for detecting a grating phase shift induced by the grating. The refractive index for the film can then be calculated directly from grating phase shift and the heterodyne phase shift for the grating pitch, and the beam's wavelength and incidence angle on the film of the measurement apparatus. Using the refractive index and heterodyne phase shift, the film's thickness is determined. Conversely, a film thickness calculation may be derived independent of the film's refractive index using from the actual corrected grating phase shift and corrected heterodyne phase shift.</p> |
