Method and means for optical detection of charge density modulation in a semiconductor
AssigneeStanford University
InventorsHarley K. Heinrich, David M. Bloom
Life of this patent
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Abstract
Disclosed is a technique for probing dynamic sheet charge density variations in integrated semiconductor devices. Using a specially designed non-invasive Nomarski phase contrast interferometer a sheet charge density sensitivity of 2.6.times.10.sup.8 e/cm.sup.2 / .sqroot.Hz is extracted from experimental data for 1 mA of detected photocurrent. The charge density sensitivity makes possible .mu.V signal level detection in an active device, and with digital signals the corresponding signal/noise level is sufficiently high that multi-mega-baud data can be captured in real time.
Claims7
A method of determining charge density in a region of a silicon body comprising the steps of
- polarizing a laser beam,
- splitting the polarized beam into two orthogonally polarized beams,
- applying the two orthogonally polarized beams to the semiconductor body with one beam being directed to said region,
- recombining reflections of the two orthogonally polarized beams after passing through the semiconductor body, and
- detecting the recombined beam by photodiode means to obtain an intensity modulated signal indicative of differential charge density.
A method of determining charge density in a region of a semiconductor body comprising the steps of
- polarizing a laser beam,
- spatially modulating said laser beam over the surface of a semiconductor body,
- obtaining a reflection of said spatially modulated laser beam after passing through said semiconductor body, and
- detecting differential relative phase of said reflected wave as indicative of charge density.
Apparatus for determining charge density in a region of a semiconductor body comprising
- means for producing a laser beam,
- polarizer means for receiving said laser beam,
- birefringent beam splitter means for splitting said polarized beam into two orthogonally polarized beams,
- lens means for applying the two orthogonally polarized beams to the semiconductor body with one beam being directed to said region,
- means for directing reflections of the two orthogonally polarized beams after passing through the silicon body back to said birefringent beam splitter thereby combining the two beams, and
- means for detecting the recombined beams to obtain an intensity modulated signal indicative of charge density.
An optical interconnect comprising
- means for generating a laser beam having a fixed wavelength,
- a semiconductor body having an active device region adjacent to a major surface and a dielectric layer on said major surface, said dielectric layer having a step in thickness over the active device region, said step being one-quarter of said fixed wavelength,
- means for directing a laser beam through said step in said dielectric layer and said active device region,
- a single mode optical fiber positioned to receive said beam after passing through said step in said dielectric layer and said semiconductor body and said active device region, and
- a photodiode detector for receiving said laser beam as passed by said optical fiber.
A method of detecting charge density in an active device region in a semiconductor body comprising
- generating a laser beam having a fixed wavelength,
- providing first and second etalons in spaced alignment, said spacing being an integral multiple of one-half wavelength of said laser beam,
- positioning said semiconductor body between said first and second etalons in axial alignment for axially receiving said laser beam, and providing a
- detector means for receiving and detecting said laser beam as passed through one of said etalons.
Dependencies are inferred from the claim text.