Dislocation type and density discrimination in semiconductor materials using cathodoluminescence measurements
AssigneeAttolight AG
InventorsMarc Fouchier, Christian Monachon
Life of this patent
Estimating the term…
Abstract
A cathodoluminescence microscope and method are used to identify and classify dislocations within a semiconductor sample. At least two CL polarized images are concurrently obtained from the sample. The images are added together to obtain a total intensity image. A normalized difference of the images is taken to obtain a degree of polarization (DOP) image. The total intensity and DOP images are compared to differentiate between edge dislocations and screw dislocations within the sample. Edge dislocation density and screw dislocation density may then be calculated.
Claims20
A cathodoluminescence microscope for simultaneously generating two polarization complemented images of a scanned area of a semiconductor sample, wherein the two images are inherently registered both spatially and temporally, comprising:
- an electron beam column having an electron source, a magnetic lens for focusing electrons emitted from the electron source to thereby form an electron beam, and a scanner scanning the electron beam over the sample;
- a light objective collecting light emitted from the sample in response to the scanning of the electron beam and forming a light beam;
- an imaging section comprising a focusing lens, a polarizing beam splitter splitting the light beam into a first polarized beam and a second polarized beam, a first light detector receiving the first polarized beam and a second light detector receiving the second polarized beam;
- and,
- a controller forming the two polarization complemented images from a first signal receiving from the first light detector and a second signal receiving from the second light detector.
A computer program stored in a storage device that, when executed by a computer causes the computer to execute steps implementing the method comprising:
- receiving a first electrical signal corresponding to a polarized cathodoluminescence beam and a second electrical signal corresponding to the polarized cathodoluminescence beam and having ninety degrees polarization rotation with respect to the first electrical signal;
- adding the first and second electrical signals to generate an intensity image of a scanned area of a sample;
- taking a normalized difference of the first and second electrical signals to generate a degree of polarization (DOP) image of the area;
- determining coordinates of center point of each contrasted spot appearing in the intensity image;
- for each of the coordinates, inspecting a corresponding zone in the DOP image to determine whether an indication of stress appears within the zone;
- and for each indication of stress classifying the corresponding contrasting spot as an edge dislocation.
A method of operating a cathodoluminescence microscope to detect defects within a semiconductor sample, comprising:
- scanning an area of the sample with an electron beam;
- collecting cathodoluminescence light emitted from the area during the scanning and forming a light beam from the cathodoluminescence light;
- passing the light beam through a polarizer beam splitter to obtain two polarized beams having ninety degrees polarization rotation with respect to each other;
- using two light detectors to simultaneously generate two electrical signals corresponding to the two polarized beams;
- adding the two signals to form an intensity image of the area;
- taking a normalized difference of the two signals to form a degree of polarization (DOP) image of the area;
- for each contrasting spot appearing in the intensity image, inspecting a corresponding zone in the DOP image and when an indication of stress appears within the zone in the DOP image, classifying the corresponding contrasting spot as an edge dislocation.
Dependencies are inferred from the claim text.