Method of electromagnetic modeling of finite structures and finite illumination for metrology and inspection

A non-transitory machine-readable storage medium having instructions stored thereon which cause a computer to perform a method of evaluating a diffracting structure, the method comprising:

• providing a scatterometry model for the diffracting structure using an optical metrology system;
• computing, with the optical metrology system, spectral information for the scatterometry model of the diffracting structure, including:
• computing background electric or magnetic fields of an environment of the diffracting structure,
• computing scattered electric or magnetic fields from the diffracting structure using a scattered field formulation based on the computed background fields, and
• computing spectral information for the scatterometry model of the diffracting structure based on the computed scattered fields;
• measuring spectral information for the diffracting structure using the optical metrology system, including illuminating the diffracting structure with a light source, and measuring spectral information for the diffracting structure with a detector;
• comparing the computed spectral information for the scatterometry model with the measured spectral information for the diffracting structure;
• and
• in response to a good model fit based on the comparison between the computed spectral information and the measured spectral information, determining a physical characteristic of the diffracting structure using the scatterometry model of the diffracting structure.

An optical measurement system comprising:

• a light source to illuminate a diffracting structure;
• a detector to measure spectral information for the diffracting structure;
• first logic to receive the measured spectral information for the diffracting structure;
• and
• second logic to:
• provide a scatterometry model of the diffracting structure;
• compute spectral information for the scatterometry model, including computing background electric or magnetic fields of an environment of the diffracting structure based on a model of the diffracting structure, computing scattered electric or magnetic fields from the diffracting structure using a scattered field formulation based on the computed background fields, and computing spectral information for the scatterometry model of the diffracting structure based on the computed scattered fields;
• compare the computed spectral information for the scatterometry model with the measured spectral information for the diffracting structure;
• and
• in response to a good model fit based on the comparison between the computed spectral information and the measured spectral information, determine a physical characteristic of the diffracting structure using the scatterometry model of the diffracting structure.