MIRROR POLISHING OF SILICON-WAFERS .3. DEVELOPMENT OF BOWL FEED AND DOUBLE SIDE POLISHING MACHINE WITH IN-SITU THICKNESS MONITORING OF SILICON-WAFERS

A bowl feed double side polishing machine has been developed to produce silicon wafers with precise thicknesses in the mirror polishing process. This machine can intermittently detect the thicknesses of silicon wafers during polishing by means of ultrasonic waves passed through a hole of the lower polishing plate that then echo off both the bottom and top surfaces of the wafers. This machine is able to measure the thickness of wafers to within lum in accuracy. Precise wafers with 125mm diameters could be polished to less than 3mum in thickness deviation and within 2mum in total flatness without any surface defects using this polishing machine.