METHOD AND INSTRUMENT FOR MEASURING DEPTH OF ETCHING

摘要

PURPOSE:To increase the quantity of variation of a detection signal and to measure depth with high reliability by calculating the light intensity ratio of out-of-phase reflection diffracted light beams from the surface of a body to be inspected which has an etched part and counting the number of times of repetition of the intensity ratio. CONSTITUTION:Laser light from a coherent light source 1 is incident on the inspected surface of the object body 4 at right angles from a window 12 after being reflected by a mirror 2 and a half-mirror 3 based on cycles of the unevenness of etched parts and unetched parts of the inspected surface. The diffracted light beams of 0th order and 1st order are incident on detectors 5 and 6 after passing through the half-mirror 3. Light intensity signal from the detectors 5 and 6 are inputted to a subtracter 8 to calculate the intensity ratio of the light of 1st order to the light of 0th order. A calculator 9 counts the number of times of repetition of variation in intensity ratio from the intensity ratio. A controller 10 compares the number of times of repetition with a set value and controls a high frequency power source 15 so that etching is finished when the number of times reaches the set value.