The present invention provides a system and method for measuring the surface properties of polishing pads using noncontact ultrasonic reflectance. An ultrasonic probe is located over the polishing surface and configured to both transmit an ultrasonic signal to the polishing surface and receive a modified...http://www.google.de/patents/US6684704?utm_source=gb-gplus-sharePatent US6684704 - Measuring the surface properties of polishing pads using ultrasonic reflectance
