Non-destructive thickness measurement of semiconductor wafer

摘要

A method for the non-destructive testing of the thickness of a semiconductor wafer (100) whose first principal surface (102) is brought into contact with a similar and supporting silicon wafer (107) whose contacting surface has a nickel plated layer (106) of high magnetic permeability. The opposite surface (104) of the wafer (100) under test carries a flat pick-up coil (108) whose inductance varies inversely with its separation from the nickel layer (106) and is therefore a measure of the wafer (100) thickness. The coil (108) forms an element of an oscillator circuit whose frequency changes can be readily correlated with the wafer (100) thickness with considerable accuracy.