US 7,248,375 B2 · Critical dimension analysis with simultaneous multiple angle of incidence measurements

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.

Claims16

Dependent claims

An apparatus for evaluating the geometry of a feature having a size significantly less than a micron formed on a sample comprising:

a laser for generating a probe beam that is directed substantially normal to the sample surface;
an optical element for focusing the probe beam to a spot overlapping the feature on the sample surface in a manner so that the rays within the probe beam create a spread of angles of incidence from zero to about 70 degrees and wherein the spot size on the probe beam on the sample is on the order of about one micron in diameter 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 output signals corresponding to a plurality of different angles of incidence;
and
a processor for analyzing the output signals generated by the detector according to a scatterometry model to evaluate the geometry of the feature on the sample.

2 more elements

A method for evaluating the geometry of a feature having a size significantly less than a micron formed on a sample comprising the steps of:

focusing a probe beam of radiation from a laser to a spot overlapping the feature on the sample surface in a manner so that the rays within the probe beam create a spread of angles of incidence from zero at the center out to about 70 degrees and wherein the spot size on the sample is on the order of one micron in diameter so that the probe beam is diffracted upon reflection;
monitoring the diffracted probe beam light and simultaneously generating a plurality of independent output signals corresponding to a plurality of different angles of incidence;
analyzing the output signals according to a scatterometry model to evaluate the geometry of the feature on the sample;
and
storing the results of the analysis.

2 more elements

An apparatus for evaluating the geometry of a feature having a size significantly less than a micron formed on a sample surface comprising:

a laser for generating a probe beam that is directed substantially normal to the sample;
an optical element for focusing the probe beam to a spot overlapping the feature on the sample surface in a manner so that the rays within the probe beam create a spread of angles of incidence from zero to about 70 degrees and wherein the spot size on the sample is on the order of about one micron in diameter so that the probe beam is diffracted upon reflection;
detector means for monitoring the diffracted probe beam light, said detector means simultaneously generating a plurality of independent output signals corresponding to a plurality of different angles of incidence;
and
a processor for analyzing the output signals generated by the detector according to a scatterometry model to evaluate the geometry of the feature on the sample.

2 more elements

Dependencies are inferred from the claim text.

Critical dimension analysis with simultaneous multiple angle of incidence measurements

Life of this patent

Critical dimension analysis with simultaneous multiple angle of incidence measurements

Life of this patent

Abstract

Claims16