The diffuse light method has been part of the semiconductor industry for many years, especially in the front-end field. OptoSurf was able to apply its extensive experience of diffuse light sensors to applications on semiconductor surfaces. The main application in the back-end field is the measurement of roughness and ripple on silicon wafers rectified at backside. Today, the back of the pad is ground to less than 50 \u03bcm in thickness. After polishing, the roughness should not be greater than Ra = 1 \u2013 3 nm.<\/p>\n
Using the OS 500 sensor, a rotary vacuum chuck and linear motion of the sensor, a 12-inch wafer is fully scanned in less than 30 seconds. Correlation functions show that the measurements are completely consistent with white light interferometers or confocal microscopes. The measurement of entire wafer surfaces with the WaferMaster measuring device has the advantage that local roughness differences are visible and at the same time warping (macro geometry) as well as corrugation (nano topography) can be measured.<\/p>\n