Critical dimension analysis with simultaneous multiple angle of incidence measurements
First Claim
1. An apparatus for evaluating the geometry of a periodic structure formed on a sample comprising:
- an incoherent light source for generating a probe beam;
an optical element for focusing the probe beam to a spot on the sample surface in a manner so that the rays within the probe beam create a spread of angles of incidence and wherein the spot size on the sample is larger than the spacing between the features of the periodic structure so that the probe beam is diffracted upon reflection;
a detector array for monitoring the light of the probe beam diffracted from the periodic structure, said detector array simultaneously generating a plurality of independent output signals corresponding to a plurality of different angles of incidence; and
a processor for evaluating the geometry of the periodic structure on the sample based on the output signals generated by the detector.
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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.
423 Citations
84 Claims
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1. An apparatus for evaluating the geometry of a periodic structure formed on a sample comprising:
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an incoherent light source for generating a probe beam;
an optical element for focusing the probe beam to a spot on the sample surface in a manner so that the rays within the probe beam create a spread of angles of incidence and wherein the spot size on the sample is larger than the spacing between the features of the periodic structure so that the probe beam is diffracted upon reflection;
a detector array for monitoring the light of the probe beam diffracted from the periodic structure, said detector array simultaneously generating a plurality of independent output signals corresponding to a plurality of different angles of incidence; and
a processor for evaluating the geometry of the periodic structure on the sample based on the output signals generated by the detector. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. An apparatus for evaluating the geometry of a periodic structure formed on a sample comprising:
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an incoherent light source for generating a probe beam;
an optical element for focusing the probe beam to a spot on the sample surface in a manner so that the rays within the probe beam create a spread of angles of incidence and wherein the spot size on the sample is larger than the spacing between the features of the periodic structure so that the probe beam is diffracted upon reflection;
detector means for monitoring the light of the probe beam diffracted from the periodic structure, said detector means for simultaneously generating a plurality of independent output signals corresponding to a plurality of different angles of incidence; and
a processor for evaluating the geometry of the periodic structure on the sample based on the output signals generated by the detector. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32)
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33. A method for evaluating the geometry of a periodic structure formed on a sample comprising the steps of:
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focusing a probe beam of incoherent radiation to a spot on the sample surface in a manner so that the rays within the probe beam create a spread of angles of incidence and wherein the spot size on the sample is larger than the spacing between the features of the periodic structure so that the probe beam is diffracted upon reflection;
monitoring the light of the probe beam diffracted from the periodic structure and simultaneously generating a plurality of independent output signals corresponding to a plurality of different angles of incidence; and
evaluating the geometry of the periodic structure on the sample based on the output signals. - View Dependent Claims (34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46)
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47. An apparatus for evaluating the geometry of a periodic structure formed on a sample comprising:
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a light source for generating a probe beam;
an optical element for focusing the probe beam to a spot on the sample surface in a manner so that the rays within the probe beam create a spread of angles of incidence and wherein the spot size on the sample is larger than the spacing between the features of the periodic structure so that the probe beam is diffracted upon reflection;
a detector array for monitoring the light of the probe beam diffracted from the periodic structure, said detector array simultaneously generating a plurality of independent output signals corresponding to a plurality of different angles of incidence;
a movable stage for supporting the sample and permitting relative movement between the sample and the probe beam so that output signals can be generating as a function of position; and
a processor for evaluating the geometry of the periodic structure on the sample based on the output signals generated by the detector. - View Dependent Claims (48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61)
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62. A method for evaluating the geometry of a periodic structure formed on a sample comprising the steps of:
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focusing a probe beam of radiation to a spot on the sample surface in a manner so that the rays within the probe beam create a spread of angles of incidence and wherein the spot size on the sample is larger than the spacing between the features of the periodic structure so that the probe beam is diffracted upon reflection;
translating the sample with respect to the probe beam;
monitoring the light of the probe beam diffracted from the periodic structure and simultaneously generating a plurality of independent output signals corresponding to a plurality of different angles of incidence as a function of position of the probe beam with respect to the periodic structure; and
evaluating the geometry of the periodic structure on the sample based on the output signals. - View Dependent Claims (63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74)
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75. An apparatus for evaluating the geometry of a periodic structure formed on a sample comprising:
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a light source for generating a probe beam;
an optical element for focusing the probe beam to a spot on the sample surface in a manner so that the rays within the probe beam create a spread of angles of incidence and wherein the spot size on the sample is larger than the spacing between the features of the periodic structure so that the probe beam is diffracted upon reflection;
detector means for monitoring the light of the probe beam diffracted from the periodic structure, said detector means simultaneously generating a plurality of independent output signals corresponding to a plurality of different angles of incidence;
means for create relative movement between the sample and the probe beam so that output signals can be generating as a function of position; and
a processor for evaluating the geometry of the periodic structure on the sample based on the output signals generated by the detector. - View Dependent Claims (76, 77, 78, 79, 80, 81, 82, 83, 84)
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Specification