Method and apparatus for evaluating surface and subsurface features in a semiconductor
DCFirst Claim
1. 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 shorter than the wavelength corresponding to the band-gap energy of the sample;
means for directing the radiation 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.
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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.
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Citations
34 Claims
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1. An apparatus for evaluating surface and subsurface conditions in a semiconductor sample comprising:
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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 shorter than the wavelength corresponding to the band-gap energy of the sample; means for directing the radiation 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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for evaluating surface and subsurface conditions in a semiconductor sample comprising the steps of:
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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; directing a radiation 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 and shorter than the wavelength corresponding to the band-gap energy of the sample; 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. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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18. An apparatus for evaluating surface and subsurface conditions in a semiconductor sample comprising:
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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 shorter than the wavelength corresponding to the band-gap energy of the sample; means for directing the radiation 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. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. A method for evaluating surface and subsurface conditions in a semiconductor sample comprising the steps of:
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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; directing a laser 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 and shorter than the wavelength corresponding to the band-gap energy of the sample; 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. - View Dependent Claims (29, 30, 31, 32, 33, 34)
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Specification