Method and apparatus for evaluating surface and subsurface features in a semiconductor
AssigneeTherma-Wave, Inc.
InventorsJon Opsal, Allan Rosencwaig, Walter L. Smith
Life of this patent
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Abstract
A method and apparatus are disclosed for evaluating surface and subsurface features in a semiconductor sample. In operation, a periodic energy source is applied to the surface of the semiconductor sample to generate a periodic electron-hole plasma. This plasma interacts with features in the sample as it diffuses. The plasma affects the index of refraction of the sample and the changing plasma density is monitored using a radiation probe. In the preferred embodiment, the radiation probe measures the plasma induced periodic changes of reflectivity of the surface of the sample to yield information about the sample, such as ion dopant concentrations, residue deposits and defects.
Claims34
An apparatus for evaluating surface and subsurface conditions in a semiconductor sample comprising:
- a periodic excitation source for supplying energy to the surface of the sample sufficient to create an electron-hole plasma having a density sufficient to cause changes in the optical reflectivity of the sample;
- a probe for emitting a beam of radiation of a fixed wavelength selected to allow focusing in the micron range;
- means for focusing the radiation probe beam to a radius in the micron range and for directing the focused probe beam within a portion of the surface of the sample which has been periodically excited in a manner such that said probe beam is reflected;
- means for monitoring the modulated intensity changes in said reflected probe beam resulting from the variations in the optical reflectivity of the sample due principally to the presence of the electron-hole plasma;
- and
- means for processing the measured intensity changes of the reflected probe beam to evaluate the sample.
A method for evaluating surface and subsurface conditions in a semiconductor sample comprising the steps of:
- supplying periodic energy to the surface of the sample to excite electrons and create an electron-hole plasma having a density sufficient to cause changes in the optical reflectivity of the sample;
- focusing a radiation probe beam to a radius in the micron range and directing the focused probe beam on a portion of the area on the surface of the sample which has been periodically excited in a manner such that the probe beam is reflected, said probe beam being of a fixed wavelength selected to allow focusing in the micron range;
- monitoring changes in the modulated intensity of the reflected probe beam resulting from the changes in the optical reflectivity of the sample due principally to the presence of the electron-hole plasma;
- and
- processing the monitored intensity changes of the probe beam to evaluate the sample.
An apparatus for evaluating surface and subsurface conditions in a semiconductor sample comprising:
- an intensity modulated laser energy beam for supplying energy to the surface of the sample sufficient to create an electron-hole plasma having a density sufficient to cause changes in the optical reflectivity of the sample;
- a laser probe for emitting a beam of radiation of a fixed wavelength selected to allow focusing in the micron range;
- means for focusing the radiation probe beam to a radius in the micron range and for directing the focused probe beam within a portion of the surface of the sample which has been periodically excited in a manner such that said probe beam is reflected;
- means for monitoring variations in the modulated intensity of said reflected probe beam resulting from changes in the optical reflectivity of the sample due principally to the presence of the electron-hole plasma;
- and
- means for processing the measured intensity changes of the reflected probe beam to evaluate the sample.
A method for evaluating surface and subsurface conditions in a semiconductor sample comprising the steps of:
- directing a periodic laser beam at the surface of the sample having an input energy sufficient to excite electrons and create an electron-hole plasma having a density sufficient to cause changes in the optical reflectivity of the sample;
- focusing a laser probe beam to a radius in the micron range and directing the focused probe beam on a portion of the area on the surface of the sample which has been periodically excited in a manner such that the probe beam is reflected, said probe beam being of a fixed wavelength selected to allow focusing in the micron range;
- monitoring changes in the modulated intensity of the reflected probe beam resulting from the changes in the optical reflectivity of the sample due principally to the presence of the electron-hole plasma;
- and
- processing the monitored intensity changes of the probe beam to evaluate the sample.
A method as recited in claim 48 wherein during said processing step, the changes of said probe beam are compared with predetermined changes of the probe beam associated with a known reference sample, whereby variations in the surface and subsurface conditions in the sample can be monitored.
Dependencies are inferred from the claim text.