Scatterometry for samples with non-uniform edges
AssigneeTherma-Wave, Inc.
InventorsYia-Chung Chang, Hanyou Chu, Jon Opsal
Life of this patent
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Abstract
A method for simulating the optical properties of samples having non-uniform line edges includes creating a model for the sample being analyzed. To simulate roughness, lines within the model are represented as combinations of three dimensional objects, such as circular or elliptical mesas. The three-dimensional objects are arranged in a partially overlapping linear fashion. The objects, when spaced closely together resemble a line with edge roughness that corresponds to the object size and pitch. A second method allows lines within the model to vary in width over their lengths. The model is evaluated using a suitable three-dimensional technique to simulate the optical properties of the sample being analyzed.
Claims25
A method for optically inspecting a sample, the method comprising:
- illuminating the sample with a probe beam;
- measuring the diffraction resulting from the interaction of the probe beam and the sample;
- defining a model of the sample, the model including a first series of three-dimensional shapes that define the edge of a line within the sample;
- evaluating the model in three dimensions to predict the diffraction resulting from the interaction of the probe beam and the sample;
- and
- adjusting and reevaluating the model to minimize the difference between the predicted and measured data.
A method of evaluating the roughness of a line edge on a wafer comprising the steps of:
- obtaining optical measurement data from the wafer;
- comparing the measured data to calculated data, the calculated data based on a model that includes the scattering effects from an array of holes or mesas and wherein the spacing between the holes or mesas in the models is selected so that the holes or mesas overlap to approximate an undulating edge;
- and
- adjusting the model to minimize the difference between the calculated and measured data.
A method for optically inspecting a sample, the method comprising:
- illuminating the sample with a probe beam;
- measuring the diffraction resulting from the interaction of the probe beam and the sample;
- defining a model of the sample, the model including at least one line having a width defined to vary over the length of the line;
- evaluating the model in three dimensions to predict the diffraction resulting from the interaction of the probe beam and the sample;
- and
- adjusting and reevaluating the model to minimize the difference between the predicted and measured data.
An apparatus for evaluating a wafer having one or more lines formed on the surface thereof comprising:
- a light source for generating a probe beam;
- a detector for detecting light from the probe beam diffracted from the wafer and generating measurement signals;
- and
- a processor for comparing the measurement signals to theoretical data, said theoretical data being generated using a model of the sample, said model including a representation of a line having edge roughness, said representation being based on a series of overlapping three-dimensional geometrical features.
An apparatus for evaluating a wafer having one or more lines formed on the surface thereof comprising:
- a light source for generating a probe beam;
- a detector for detecting light from the probe beam diffracted from the wafer and generating measurement signals;
- and
- a processor for comparing the measurement signals to theoretical data, said theoretical data being generated using a model of the sample, said model including a representation of a line having edge roughness, said representation being based on a line having a width which varies over the length thereof and being defined by a superposition of periodic functions.
Dependencies are inferred from the claim text.