Etching system and method of controlling etching process condition

An etching system comprising:

• a light source configured to irradiate incident light into a target wafer;
• a light intensity measuring unit configured to measure light intensity according to a wavelength of interference light generated by interference between reflected light beams from the target wafer;
• a signal processor configured to detect a first time point at which a first extreme value in an intensity of first interference light having a first wavelength is generated and a second time point at which a second extreme value in an intensity of second interference light having a second wavelength different from the first wavelength is generated;
• and
• a controller configured to compare a time difference between the first and second time points with corresponding reference time points and control a process condition according to the comparison result.

An etching system comprising:

• a light source configured to irradiate light into a target wafer;
• a light intensity measuring unit configured to measure light intensity of at least one interference light generated by reflected light beams from the target wafer;
• a signal processor configured to detect a time point corresponding to an extreme value of light intensity of the at least one interference light;
• and
• a controller configured to compare the time point corresponding to the extreme value of light intensity detected from the signal processor with a second time point and control a process condition according to the comparison result.