Detector configurations for optical metrology
AssigneeTherma-Wave, Inc.
InventorJon Opsal
Life of this patent
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Abstract
An apparatus is disclosed for obtaining ellipsometric measurements from a sample. A probe beam is focused onto the sample to create a spread of angles of incidence. The beam is passed through a quarter waveplate retarder and a polarizer. The reflected beam is measured by a detector. In one preferred embodiment, the detector includes eight radially arranged segments, each segment generating an output which represents an integration of multiple angle of incidence. A processor manipulates the output from the various segments to derive ellipsometric information.
Claims10
A method of evaluating the geometry of small structures having critical dimensions formed on a semiconductor wafer comprising the steps of:
- focusing a probe beam onto the surface of the wafer in manner to create a spread of angles of incidence at a plurality of planes of incidence;
- retarding the phase of one polarization state of the probe beam with respect to the phase of the other polarization state;
- interfering the two polarization states in the probe beam after the probe beam has been reflected from the surface of the sample;
- measuring the power of the reflected probe beam using a detector defined by a two dimensional array of detector elements, each element generating output signals;
- and
- evaluating the geometry of the structures using output signals from a plurality of detector elements corresponding to a plurality of angles of incidence and a plurality of planes of incidence.
A method of evaluating the geometry of small structures having critical dimensions formed on a semiconductor wafer comprising the steps of:
- focusing a probe beam onto the surface of the wafer in manner to create a spread of angles of incidence at a plurality of planes of incidence;
- retarding the phase of one polarization state of the probe beam with respect to the phase of the other polarization state;
- interfering the two polarization states in the probe beam after the probe beam has been reflected from the surface of the sample;
- measuring the power of the reflected probe beam using a detector defined by a two dimensional array of detector elements, each element generating output signals, with the output signals of the detector elements corresponding to a plurality of angles of incidence, a plurality of planes of incidence and a plurality of polarizations relative to the orientation of the structure on the wafer;
- and
- evaluating the geometry of the structures using output signals from a plurality of detector elements corresponding to a plurality of angles of incidence, a plurality of planes of incidence and a plurality of polarizations relative to the orientation of the structure on the wafer.
Dependencies are inferred from the claim text.