Modeling of an ARS sensor system in spatial and time domain

Abstract

Scatterometry is a powerful and fast measurement method to measure surfaces and its properties. The backscattered light from a coherently illuminated surface contains information about integral surface topography constants, material properties, surface defects and contamination. In this paper a generic system model of an angle resolved light scatter sensor (ARS sensor) will be discussed and exemplified by using the sensor system LARISSA (Large Dynamic Range Intelligent Scatter Sensor Approach). The system model consists of two parts - firstly in spatial domain and secondly in time (or frequency) domain. The part of the system model in spatial domain contains the characteristics of the optical map of the scattered light onto a detector system. The optical map will be discussed by using an elliptical mirror optics with regard to aberration effects. The part of the system model in time (or frequency) domain contains the characteristics of the conversion of scattered light into quantized signals. The basic steps of the conversion process will be considered. Furthermore, the characteristics in time domain of a single CMOS detector (photo diode) with logarithmical intensity characteristics will be discussed to estimate the opto electronic bandwidth limitation and the minimal exposure time for different applications. Based on the system model basic performance limits will be summarized and further design steps of the sensor system LARISSA will be outlined. This paper is a continuation of a previous paper.