HIGH-SCAN RATE POSITIONER FOR SCANNED PROBE MICROSCOPY

摘要

In recent years, high-speed atomic force microscopy (AFM) has been the subject of new focus [1, 2, 3]. The high resolution capability makes AFMs a promising technology for dimensional metrology of artifacts such as semiconductor integrated circuits and photomasks. Further, to allow cost-effective use of an AFM in on-line measurement processes, it is necessary to achieve high imaging rates, and thereby high scan rates of the AFM tip. We report here on an initial design effort and prototype of a novel two degree of freedom (2 DOF) scanner for the fast scan (x-axis) and vertical (z-axis) for a high-speed, high-accuracy AFM. Our ultimate design goal is to scan a 50μm × 50μm area of 10~6 pixels with a 10μm vertical range at a 1 Hz rate. The desired sensor noise is 1 nm in the horizontal scan axes, and 0.2 nm in the vertical surface-following axis. The scanner is intended for imaging targets such as selected areas on semiconductor wafers. The relatively large mass of such targets requires that the approximately 200g accelerations of the fast scan axis be allocated to the tip scanning mechanism. We also allocate the vertical height-following function to the scanner vertical axis due to its potentially achievable high bandwidth.