Semiconductor Production Apparatus

A semiconductor production apparatus for etching a semiconductor wafer arranged in a container and having a film on the surface thereof, by use of a plasma generated in the container, comprising:

• a detector which detects a temporal change of a quantity of an interference light for at least two wavelengths obtained from the surface of the wafer for a predetermined time period of an etching process of the wafer;
• and
• a determining device which determines an etching quantity of the wafer, which varies as long as the etching process proceeds, based upon a particular change arising in the interference light of plural pairs of wavelengths, the plural pairs of the wavelengths corresponding to the etching quantities, respectively, and the particular change being detected by using detected results obtained from the detector.