Fast measurement of the thickness and group refractive index distribution of solid plates by line-field dispersive interferometry.

Real-time measurement of the thickness and group refractive index is crucial for semiconductor devices. In this paper, we proposed a fast synchronous method for measuring the thickness and group refractive index distribution of solid plates based on line-field dispersive interferometry. The proposed method measured the line-field distribution in an illuminated region through a single step. A low-cost spectrometer calibration method using an eight-channel dense wavelength division multiplexer was developed for verification. The line-field distribution of a three-step silicon wafer was successfully measured within 3.3 ms. The combined uncertainties for the geometrical thickness and group refractive index were <50 nm and 4 × 10-4, respectively.

Grating-Corner-Cube-Based Roll Angle Sensor.

This paper presents a specifically designed grating-corner-cube sensor for precise roll angle measurements. Owing to the diffraction characteristics of the transmission grating and reflection characteristics of the corner cube, two spatially separated parallel beams are naturally constructed. Through differential detection of the positions of two parallel beams, we experimentally demonstrate the possibility of a precise roll angle measurement at a high refresh rate. A performance evaluation of the proposed technique indicates a stability of 0.46 arcsec over 5 min. Compared with a commercial autocollimator over a range of 500 arcsec, the residuals are maintained within ±2 arcsec with a standard deviation of 1.37 arcsec. Furthermore, a resolution of 0.8 arcsec can be achieved using the proposed method. The developed compact roll angle sensor has potential applications in academic and industrial fields.