Compensation of phase change on reflection in white-light interferometry for step height measurement

We present a method for compensating for the phase change on reflection in scanning white-light inteferometry that practically permits precise three-d imensional profile mapping of composite target surfaces that comprise multi ple, dissimilar materials. The compensation method estimates the variation of phase change with the spectral distribution of the light source through a first-order approximation and then directly compensates for the measureme nt errors by performing two additional quasi-monochromatic phase-measuring interferometric measurements. Experimental results prove that the proposed compensation method is capable of reducing the measurement error in step he ight gauging to +/-5 nm or less. (C) 2001 Optical Society of America.