Cost effective probing in high volume manufacture of micro LEDs
AssigneeAttolight AG
InventorMatthew J. Davies
Life of this patent
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Abstract
A wafer having μLEDs is inspected using cathodoluminescence microscopes. A fast scan is enabled by splitting the CL beam into several beams and sensing the beams with point detectors. Optical filters are inserted in the optical path upstream of the detectors, such that each detector senses a different frequency band. The signals are ratioed and the ratios are compared to expected reference. Regions of extreme value are identified and, if desired, a high resolution scan is performed on the regions or a sample of the regions. Viability score is calculated for each identified region.
Claims20
A cathodoluminescence microscope for inspecting samples having a plurality of micro LED mesas formed therein, 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, splitter arrangement splitting the light beam into a plurality of split beams, a plurality of point detector, each positioned to receive one of the split beams, and a filter arrangement limiting the bandwidth of at least a subset of the plurality of split beams;
- and,
- a controller receiving output signals from the plurality of point detectors and generating ratios of paired output signals of the plurality of point detector.
A method for inspecting a wafer having a plurality of mesas for forming micro LED in each mesa, wherein each mesa having length of 100 microns or less, comprising:
- placing the wafer in a CL microscope;
- performing a first scan of the wafer at a first resolution to generate a plurality of CL beams;
- using a plurality of single point detectors to simultaneously detect the plurality of CL beams, wherein each of the point detectors is arranged to receive a different partial spectrum than the remaining point detectors;
- generating a plurality of detector ratios, wherein each of the detector ratios comprises a ratio of signals received from two of the point detectors;
- and
- comparing the detected ratios to expected ratios to determine properties of the mesas.
Dependencies are inferred from the claim text.