A novel design of multi-light LAPS based on digital compensation of frequency domain

In this report, a method which can significantly increase the measurement r ate of the light-addressable potentiometric sensor (LAPS) is suggested. By illuminating the LAPS simultaneously at several positions, of which each is illuminated with a light pointer modulated with a different frequency, the surface potential at all illuminated regions can be measured simultaneousl y by analysing the resulting photocurrent. By:using this method, the rate t o obtain a complete image of the surface potential distribution across a LA PS wafer can be drastically increased compared to the conventional mode, il l which images are obtained by scanning the surface with one single light p ointer. The technical feasibility of such a device is discussed and test me asurements an presented. (C) 2001 Elsevier Science B.V. All rights reserved .