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 rate 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 simultaneously by analyzing the resulting photocurrent. By using this method, the rate to obtain a complete image of the surface potential distribution across a LAPS wafer can be drastically increased compared to the conventional mode, in which images are obtained by scanning the surface with one single light pointer. The technical feasibility of such a device is discussed and test measurements are presented.