Research On The Data Analysis And Processing System Of Step Height Measurements By Stylus Method

The measurement of step height of surface plays a very important role in the surface metrology. On the one hand, the definition of meter can be trace to the source via the step height in the surface measurement technology; On the other hand, the problems of measurement of step height occur almost everywhere in the industrial domain that relies mainly on semiconductor manufacturing. Step height is an important parameter.A data analysis and processing system is built for the surface features and the step height measurement based on the stylus-measurement theory. The analysis and evaluation of step height via computer is achieved in this system.Firstly, a computer samples the surface profile signal. Secondly, the surface roughness is extracted though a digital filter, and then the surface roughness can be evaluated. In this thesis, the maximum differentiation of the height is used for the accurate anchor of the edge of the step, and then the width of the step is calculated. Based on the results of the edge anchor, several segments of the height data are selected and linear polynomial fitting are done using least square approximant on these segments separately. Then, the step height is calculated with some algorithms: the ISO algorithm adopted by ISO 5436 and the two-sided algorithm used at NIST (the National Institute of Standards and Technology). A balance method is advanced to solve the tilting problem on the height measurement. The analysis of a set of test data shows that all of the algorithms are acceptable, and using the balance method can get a more accurate result. Finally, the calibration of the system is discussed, and the uncertainty of the system is analyzed.