Etching amount calculating method, storage medium, and etching amount calculating apparatus

A computer-readable storage medium storing a program for causing a computer to execute an etching amount calculating method for calculating an etching amount of a concave portion that is formed in a substrate using a mask film by etching the substrate, the etching amount calculating method comprising:

• an irradiating step of irradiating light on the substrate;
• a light receiving step of receiving superposed interference light resulting from superposition of at least interference light of reflected light from the mask film and reflected light from a bottom of the concave portion on other interference light;
• an interference wave calculating step of calculating a superposed interference wave from the received superposed interference light;
• a waveform extracting step of extracting a waveform in a predetermined time period from the superposed interference wave;
• a frequency analyzing step of carrying out a frequency analysis of the extracted waveform;
• an interference period detecting step of detecting a period of an interference wave produced from the reflected light from the mask film and the reflected light from the bottom of the concave portion from a frequency distribution obtained by the frequency analysis;
• an integrating and averaging step of repeating the interference wave calculating step, the waveform extracting step, the frequency analyzing step, and the interference period detecting step while shifting the predetermined time period by a predetermined time, and integrating and averaging the detected periods of the interference wave at each repetition;
• and
• an etching amount calculating step of calculating the etching amount of the concave portion based on the integrated and averaged periods of the interference wave.

An etching amount calculating apparatus that calculates an etching amount of a concave portion that is formed in a substrate using a mask film by etching the substrate, comprising:

• an irradiating unit that irradiates light on the substrate;
• a light receiving unit that receives superposed interference light resulting from superposition of at least interference light of reflected light from the mask film and reflected light from a bottom of the concave portion on other interference light;
• an interference wave calculating unit that calculates a superposed interference wave from the received superposed interference light;
• a waveform extracting unit that extracts a waveform of a predetermined time period from the superposed interference wave;
• a frequency analyzing unit that carries out a frequency analysis of the extracted waveform;
• an interference period detecting unit that detects a period of an interference wave produced from the reflected light from the mask film and the reflected light from the bottom of the concave portion from a frequency distribution obtained by the frequency analysis;
• an integrating and averaging unit that repeats the interference wave calculation, the waveform extraction, the frequency analysis, and the interference period detection while shifting the predetermined time period by a predetermined time, and integrates and averages the detected periods of the interference wave at each repetition;
• and
• an etching amount calculating unit that calculates the etching amount of the concave portion based on the integrated and averaged period of the interference wave.