A New Method of Non-Contact Measurement for Microtopography in Semiconductor Wafer Implementing a New Optical Probe Based on the Precision Defocus Measurement

In this paper, a new method of non-contact measurement has been developed for 3D topography for a semiconductor wafer, implementing a new optical probe based on precision defocus measurement. The developed technique consists of the new optical probe, precision stages, and the measurement/control system. The basic principle of the technique is to use the reflected slit beam from the specimen surface to measure the deviation of the specimen surface. The defocusing distance can be measured by the reflected slit beam, where the defocused image is measured by the proposed optical probe, giving very high resolution. A distance measuring formula has been proposed for the developed probe, using the laws of geometric optics. A precision calibration technique has been applied, giving about 10 nm resolution and 72 nm four-sigma uncertainty. In order to quantitise the micro pattern on the specimen surface, some efficient analysis algorithms have been developed to analyse the 3D topography pattern and some parameters of the surface. The developed system has been successfully applied to measure the wafer surface, demonstrating the line scanning feature and the excellent 3D measurement capability.