Design and performance evaluation of an interferometric controlled planar nanopositioning system

High technology applications for example in the semiconductor or the optical industry require positioning systems providing repeatability and uncertainty in the range of nanometers together with x-, y-travel ranges of several hundreds of millimeters. We contribute in this research by investigating the applicability of integrated planar direct drives for the realization of nanopositioning- and nanomeasuring machines (NPM/NMM). The paper introduces the concept of planar integrated direct drives and explains the engineering design of the realized system for a 100 mm circular travel range in x and y. It presents the drive system parameters and the arrangement and interaction of the main components. The results of the initial operation are presented with a special focus on the question how the closed loop system can be taken into operation with a free floating slider. The evaluation of the positioning performance leads to the result that a 2D servo error of less than exy = 1.3 nm is achieved at arbitrary positions within the travel range. As a result of repeated step response tests, the positioning resolution is 0.5 nm. The measurement of the coincidental z-movement of the aerostatically supported slider yields a z-vibration with a standard deviation of σz = 0.45 nm. Regarding the drive system these results represent the limit of what can be reached with this setup as the measured error motions are in the range of the noise of the fixed environment setup. By measuring the characteristics of the aerostatic slider support at the fully assembled system the present air bearing stiffness is determined and based on a FEM-simulation of the slider eigenfrequencies the influence on the force transfer behavior is expected to be only marginal.