Dynamic stiffness analysis of repetitive control and applied to Advanced Metrology Analyzer

Abstract

Advanced metrology analyzer is a powerful equipment for integrated circuits package metrology measurement include warpage, topography, in-plane and out-of-plane displacements, strains, and coefficient of thermal expansions, based on the principle of three dimensional digital image correlation methodology. Measure the metrology of several units in a strip substrate, wafer or panel of several monitor temperatures during the process temperature cycle for process and product analysis is a crucial technology for package thermal-stress analysis. It's a key technique to precise control the positions of the camera module for digital images capture repeat again and again by a motor controlled stage. Unfortunately, the position precision will shift due to the vibration disturbance. Fiducial mark for positioning is an extensive used method on special-purpose machine. However, advanced metrology analyzer is a general-purpose machine. It should measure various samples; meanwhile, the samples should do surface pretreatment to generate random speckles; fiducial mark is not suitable for this kind of machines. Fortunately, this could be done by enhancing the dynamic stiffness of the control system. The property of dynamic disturbances rejection is often called dynamic stiffness which is substituted for disturbance response. For dynamic stiffness enhancement, this paper presents a new method for synthesizing repetitive controllers capable of rejecting periodic vibration disturbance. Dynamic stiffness of the control system is analyzed. Direct and quadrature dynamic stiffness are defined for the controllers' design. A trade-off method between the choices of two controller's parameters is often necessary such that both the rejecting performance and stability can be achieved simultaneously. The positioning precision of advanced metrology analyzer is achieved by the proposed control design.