Database interpolation method for optical measurement of diffractive microstructures
AssigneeTokyo Electron Limited
InventorsKenneth C. Johnson, Fred E. Stanke
Life of this patent
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Abstract
A database interpolation method is used to rapidly calculate a predicted optical response characteristic of a diffractive microstructure as part of a real-time optical measurement process. The interpolated optical response is a continuous and (in a preferred embodiment) smooth function of measurement parameters, and it matches the theoretically-calculated optical response at the database-stored interpolation points.
Claims10
A method of evaluating a diffracting structure formed on a semiconductor sample comprising the steps of:
- creating a database, said database including interpolation points and associated theoretical optical response characteristics, each interpolation point corresponding to a sample parameter set and with the associated theoretical optical response characteristics being determined by applying a sample model to each of the parameter sets;
- measuring the actual optical response characteristics of the sample;
- and
- iteratively interpolating between the interpolation points using an interpolation model that defines a substantially continuous function which intersects with the interpolation points in order to derive a set of interpolated optical response characteristics that best fit the actual optical response characteristics to evaluate the sample.
A method of evaluating parameters of a diffracting structure formed on semiconductor samples comprising the steps of:
- calculating optical response characteristics for selected parameter sets, each set of parameters corresponding to an interpolation point;
- defining a continuous model of the optical responses as a function of the parameters that equals the optical responses at the interpolation points;
- measuring an optical signal of a sample;
- and
- evaluating the parameters of the sample by iteratively fitting the optical signal with the interpolation model.
Dependencies are inferred from the claim text.