Method of and apparatus for measuring thickness of thin film or thin layer

An apparatus for measuring a thickness of every layer of a thin film consisting of a single or multiple layers, comprising:

• means for casting a measurement light onto the thin film;
• means for observing a measured spectrum of an interference light of lights reflected by a front surface of the thin film, reflected by each boundary between the layers of the thin film, and reflected by a rear surface of the thin film, wherein the measured spectrum shows a cyclic curve;
• means for creating a constructed spectrum including a parameter, wherein the parameter has the same dimension as that representing the cyclic curve of the measured spectrum;
• means for calculating the least square error between the measured spectrum and the constructed spectrum;
• means for detecting the local minimum value of the least square error while changing the parameter within a predetermined range;
• and
• means for calculating the thickness of each layer of the thin film from the parameter yielding the local minimum value, using refractive indices of the substances constituting the layers.

A method of measuring a thickness of every layer of a thin film consisting of a single or multiple layers, comprising steps of:

• casting a monochromatic measurement light onto the thin film;
• observing a measured spectrum of an interference light of lights reflected by a front surface of the thin film, reflected by each boundary between the layers of the thin film, and reflected by a rear surface of the thin film while changing a wavelength of the measurement light, wherein the measured spectrum shows a cyclic curve;
• creating a constructed spectrum including a parameter, wherein the parameter has the same dimension as that representing the cyclic curve of the measured spectrum;
• calculating the least square error between the measured spectrum and the constructed spectrum;
• detecting a local minimum value of the least square error while changing the parameter within a predetermined range;
• and
• calculating the thickness of each layer of the thin film from the parameter yielding the local minimum value, using refractive indices of substances constituting the layers.

An apparatus for measuring a thickness of a thin film consisting of a single or multiple layers, comprising:

• means for casting a monochromatic measurement light onto the thin;
• means for measuring an intensity of an interference light of lights reflected by a front surface of the thin film, reflected by each boundary of the layers of the thin film, and reflected by a rear surface of the thin film;
• means for creating a measured spectrum with the measured intensity of the interferance light while changing the wavelength of the measurement light;
• means for creating a constructed spectrum including a parameter, wherein the parameter has the same dimension as that representing the cyclic curve of the measured spectrum;
• means for calculating the least square error between the measured spectrum and the constructed spectrum;
• means for detecting a local minimum value of the least square error while changing the parameter within a predetermined range;
• and
• means for calculating the thickness of each layer of the thin film from the parameter yielding the local minimum value, using refractive indices of the substances constituting the layers.