Critical dimension analysis with simultaneous multiple angle of incidence measurements
First Claim
1. An apparatus for evaluating the geometry of one or more geometrical features on the surface of a wafer having at least one dimension significantly less than a micron comprising:
- a light for source for generating a probe beam;
an optical element for focusing the probe beam to a spot overlapping the feature on the wafer surface in a manner so that the rays within the probe beam create a spread of angles of incidence and so that the probe beam is diffracted upon reflection;
a detector array for monitoring the diffracted probe beam light, said detector array simultaneously generating a plurality of independent first output signals corresponding to a plurality of different angles of incidence;
a measurement module selected from one of a broadband reflectometer and a broadband ellipsometer, said measurement module for optically inspecting the feature and generating a plurality of second output signals; and
a processor for evaluating the geometry of the feature on the wafer based on a combination of the first and second output signals.
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Abstract
A method and apparatus are disclosed for evaluating relatively small periodic structures formed on semiconductor samples. In this approach, a light source generates a probe beam which is directed to the sample. In one preferred embodiment, an incoherent light source is used. A lens is used to focus the probe beam on the sample in a manner so that rays within the probe beam create a spread of angles of incidence. The size of the probe beam spot on the sample is larger than the spacing between the features of the periodic structure so some of the light is scattered from the structure. A detector is provided for monitoring the reflected and scattered light. The detector includes multiple detector elements arranged so that multiple output signals are generated simultaneously and correspond to multiple angles of incidence. The output signals are supplied to a processor which analyzes the signals according to a scattering model which permits evaluation of the geometry of the periodic structure. In one embodiment, the sample is scanned with respect to the probe beam and output signals are generated as a function of position of the probe beam spot.
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Citations
24 Claims
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1. An apparatus for evaluating the geometry of one or more geometrical features on the surface of a wafer having at least one dimension significantly less than a micron comprising:
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a light for source for generating a probe beam; an optical element for focusing the probe beam to a spot overlapping the feature on the wafer surface in a manner so that the rays within the probe beam create a spread of angles of incidence and so that the probe beam is diffracted upon reflection; a detector array for monitoring the diffracted probe beam light, said detector array simultaneously generating a plurality of independent first output signals corresponding to a plurality of different angles of incidence; a measurement module selected from one of a broadband reflectometer and a broadband ellipsometer, said measurement module for optically inspecting the feature and generating a plurality of second output signals; and a processor for evaluating the geometry of the feature on the wafer based on a combination of the first and second output signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method for evaluating the geometry of one or more geometrical features on the surface of a wafer having at least one dimension significantly less than a micron comprising the steps of:
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focusing a probe beam of radiation to a spot overlapping the feature on the wafer surface in a manner so that the rays within the probe beam create a spread of angles of incidence and so that the probe beam is diffracted upon reflection; monitoring the diffracted probe beam light and simultaneously generating a plurality of independent first output signals corresponding to a plurality of different angles of incidence; measuring the feature using a measurement module selected from one of a broadband reflectometer and a broadband ellipsometer and generating a plurality of second output signals; and evaluating the geometry of the feature on the wafer based on the first and second output signals. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification