Patent ID: 7259866

Claim:
A semiconductor fabricating method for etching a semiconductor wafer, comprising the steps of: placing the semiconductor wafer having a film thereon inside of a chamber; generating plasma inside of the chamber; detecting a quantity of interference lights for each of at least two wavelengths obtained from a surface of the wafer for a predetermined time period during the etching of the wafer; detecting a first time point at which the detected quantity of the interference lights for one of the two wavelengths becomes a maximum and a second time point at which the detected quantity of the interference lights for the other wavelength becomes a minimum; determining a state of the etching based on a result of comparing a predetermined value with an interval between the first time point and the second time point, wherein both the first and second time points are detected by using outputs of a detector for detecting a quantity of the interference lights; and controlling the etching in accordance with a result of the determining.