Abstract: In this paper we discuss an optical metrology technique for the determination of optimum lithography parameters through an interrogation of the latent image. This technique, called the Lithography Process Monitor (LPM), involves illuminating a latent image grating with a laser beam. The intensity of the orders diffracted from the grating has been shown to be directly related to the photoactive compound (PAC) concentration profile, and consequently, to the profile of the developed resist. We have developed a method of modeling the intensity in the diffracted orders by using lithography simulation software in conjunction with rigorous coupled wave diffraction analysis. Experiments have been conducted with both positive and negative resist. In addition, we have been able to determine the 'absolute' location of the top of the photoresist with respect to the stepper focal reference and determine film thickness variations on the wafer.!17
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