In-situ method for measuring the endpoint of a resist recess etch process

An in-situ method for measuring the endpoint of a resist recess etch process for DRAM trench cell capacitors of ground rules of about 0.175 μm and smaller to determine the buried plate depth on a semiconductor wafer thereof, comprising:

• a) placing a FTIR device on the etch chamber;
• b) illuminating the surface of a semiconductor wafer during etching to a resist recess depth with IR radiation from said FTIR device;
• c) detecting reflection spectra from the illuminated surface of said semiconductor wafer with a photoconductive IR detector;
• d) performing a frequency analysis of the reflection spectra and providing a corresponding plurality of wave numbers in response thereto;
• and
• e) utilizing calculating means coupled to the photoconductive IR detector to calculate the resist recess depth at the illuminated portion of the wafer from said plurality of wave numbers corresponding to said refection spectra.