Techniques for optimized scatterometry

A machine-readable storage medium having instructions stored thereon which cause a data processing system to perform a method of computation in an optical measurement system to evaluate a diffracting structure, the method comprising:

• computing a finite-difference derivative of a field matrix with respect to first parameters, the field matrix comprising material boundary information and the first parameters comprising a parameter describing the material boundaries of the diffracting structure;
• computing an analytic derivative of a Jones matrix with respect to the first parameters using the finite-difference derivative of the field matrix with respect to the first parameters;
• computing a finite-difference derivative of the Jones matrix with respect to second parameters comprising a non-material boundary parameter;
• and
• determining values of parameters of the diffracting structure based on the analytic derivative of the Jones matrix with respect to the first parameters and the finite-difference derivative of the Jones matrix with respect to the second parameters.

An optical measurement system comprising:

• first logic for receiving optical reflectance measurements for a diffracting structure;
• a processor configured to evaluate the diffracting structure according to a method comprising:
• computing a finite-difference derivative of a field matrix with respect to first parameters, the field matrix comprising material boundary information and the first parameters comprising a parameter describing the material boundaries of the diffracting structure;
• computing an analytic derivative of the Jones matrix with respect to the first parameters using the finite-difference derivative of the field matrix with respect to the first parameters;
• computing a finite-difference derivative of the Jones matrix with respect to second parameters comprising a non-material boundary parameter;
• and
• determining values of parameters of the diffracting structure based on the analytic derivative of the Jones matrix with respect to the first parameters and the finite-difference derivative of the Jones matrix with respect to the second parameters.

A method of evaluating a diffracting structure associated with a sample illuminated by incident light, the method comprising:

• generating a transfer matrix having Taylor Series approximations for elements, the transfer matrix relating electric fields at a first layer of the sample with electric fields at a second layer of the sample, at least one of the Taylor Series approximations comprising a field matrix representing boundary conditions;
• decomposing the field matrix into two or more smaller matrices based on a symmetry between the incident light and the diffracting structure;
• computing spectral information for the first layer based on the Taylor Series approximation elements of the transfer matrix with the decomposed field matrix;
• and
• providing a model of the diffracting structure, the model associated with the spectral information.

A machine-readable storage medium having instructions stored thereon which cause a data processing system to perform a method of computation in an optical measurement system to evaluate a diffracting structure, the method comprising:

• generating a transfer matrix having Taylor Series approximations for elements, the transfer matrix relating electric fields at a first layer of the sample with electric fields at a second layer of the sample, at least one of the Taylor Series approximations comprising a field matrix representing boundary conditions;
• decomposing the field matrix into two or more smaller matrices based on a symmetry between the incident light and the diffracting structure;
• computing spectral information for the first layer based on the Taylor Series approximation elements of the transfer matrix with the decomposed field matrix;
• and
• providing a model of the diffracting structure, the model associated with the spectral information.

An optical measurement system comprising:

• first logic for receiving optical reflectance measurements for the diffracting structure;
• a processor configured to evaluate the diffracting structure according to a method comprising:
• generating a transfer matrix having Taylor Series approximations for elements, the transfer matrix relating electric fields at a first layer of the sample with electric fields at a second layer of the sample, at least one of the Taylor Series approximations comprising a field matrix representing boundary conditions;
• decomposing the field matrix into two or more smaller matrices based on a symmetry between the incident light and the diffracting structure;
• computing spectral information for the first layer based on the Taylor Series approximation elements of the transfer matrix with the decomposed field matrix;
• and
• providing a model of the diffracting structure, the model associated with the spectral information.