Mirror Polishing of Silicon Wafers (4th Report)

A bowl feed double side polishing machine has been newly developed to produce silicon wafers with precise thickness in the mirror polishing process. This machine can detect intermittently the thickness of silicon wafers during polishing by means of ultrasonic waves passing through a hole of the lower polishing plate, and being reflected as echoes on both the bottom and the top surfaces of wafers. This machine is able to measure the thickness of wafers within 1 μm accuracy. Precise wafers with 125 mm diameter could be polished less than 3 μm thickness deviation and within 2 μm flatness without any surface defects using the developed polishing machine.