Scanning electron microscopy by photovoltage contrast imaging
AssigneeThe United States of America as represented by the Secretary of the Navy
InventorLarry D. Flesner
Life of this patent
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Abstract
A process and apparatus are disclosed for remotely determining electrical properties of a semiconductor. A surface of the semiconductor is simultaneously irradiated with an electron beam to generate secondary electrons from the irradiated surface and with a modulated light beam. Secondary electrons emitted by the semiconductor are filtered by an electron energy analyzer. An electron detector receives the filtered electrons and provides an output corresponding to electrical properties of the irradiated area. The output is provided to a computer which calculates the difference in output between periods when the semiconductor is being illuminated with the light beam and when it is not so illuminated. The time dependence of the output may also be measured.
Claims25
An apparatus for determining electrical properties of a semiconductor, comprising:
- first means for irradiating said semiconductor with an electron beam so that secondary electrons having energy spectra are emitted from said semiconductor;
- second means for illuminating said semiconductor with a modulated light beam and for inducing a photovoltaic effect in said semiconductor so that said energy spectra of said secondary electrons may be modified in accordance with said electrical properties of said semiconductor;
- third means positioned to receive said secondary electrons emitted from said semiconductor for selectively filtering said secondary electrons based on said energy spectra of said secondary electrons;
- fourth means positioned to receive said filtered secondary electrons for detecting said filtered secondary electrons and for providing an output functionally related to a quantity of said detected secondary electrons;
- and
- fifth means operably coupled to receive said output of said fourth means for synchronizing detection of said filtered secondary electrons to a first period when said semiconductor is being illuminated by said light beam and to a second period, alternate to said first period, when said semiconductor is not being illuminated by said light beam, and for determining a change of said output between said first and second periods.
A process for determining electrical properties of a semiconductor, comprising the steps of:
- irradiating said semiconductor with an electron beam so that secondary electrons having energy spectra are emitted from said semiconductor;
- illuminating said semiconductor with a modulated light beam to induce a photovoltaic effect in said semiconductor so that said energy spectra of said secondary electrons may be modified in accordance with said electrical properties of said semiconductor;
- selectively filtering said secondary electrons based on said energy spectra of said secondary electrons;
- detecting said filtered secondary electrons in a first period when said semiconductor is being illuminated by said light beam and in a second period, alternate to said first period, when said semiconductor is not being illuminated by said light beam;
- providing an output functionally related to a quantity of said detected secondary electrons;
- and
- determining a change of said output between said first and second periods.
Dependencies are inferred from the claim text.