# US 12,009,176 B2 · Method and system for generating a diffraction image

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- Number: US 12,009,176 B2
- Document ID: US12009176B2
- Status: Granted
- Kind: B2
- Application number: 18/321,442
- Filed: 2023-05-22
- Published: 2023-09-21
- Granted: 2024-06-11
- Earliest claimed: 2021-07-13
- Assignees: FEI Company
- Applicants: FEI Company
- Inventors: Bart Buijsse; Bart Jozef Janssen
- Web page: https://patentgrep.com/patent/US12009176B2

## CPC

- G01N 23/20058: Measuring diffraction of electrons, e.g. low energy electron diffraction [LEED] method or reflection high energy electron diffraction [RHEED] method
- H01J 37/265: {Controlling the tube; circuit arrangements adapted to a particular application not otherwise provided, e.g. bright-field-dark-field illumination}
- G01N 23/205: using diffraction cameras
- H01J 37/295: Electron or ion diffraction tubes
- H01J 2237/04: Means for controlling the discharge
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H)

## Abstract

Method and system for generating a diffraction image comprises acquiring multiple frames from a direct-detection detector responsive to irradiating a sample with an electron beam. Multiple diffraction peaks in the multiple frames are identified. A first dose rate of at least one diffraction peak in the identified diffraction peaks is estimated in the counting mode. If the first dose rate is not greater than a threshold dose rate, a diffraction image including the diffraction peak is generated by counting electron detection events. Values of pixels belonging to the diffraction peak are determined with a first set of counting parameter values corresponding to a first coincidence area. Values of pixels not belonging to any of the multiple diffraction peaks are determined using a second, set of counting parameter values corresponding to a second, different, coincidence area.

## Claims

### Claim 1

A method comprising:
irradiating a sample with an electron beam;
acquiring multiple frames from a detector;
identifying multiple diffraction peaks in the multiple frames; and
generating a diffraction image including the multiple diffraction peaks from the multiple frames by counting electron detection events, wherein values of pixels belonging to at least a first diffraction peak of the multiple diffraction peaks are determined using a first set of counting parameter values corresponding to a first coincidence area, and values of pixels not belonging to the first diffraction peak are determined using a second set of counting parameter values corresponding to a second, different, coincidence area, and an intensity of the first diffraction peak is determined based on a first dose rate of the first diffraction peak estimated in a counting mode.

### Claim 2 (depends on 1)

The method of claim 1, wherein estimating the first dose rate of the first diffraction peak in the counting mode includes estimating the first dose rate based on an event rate of electron detection events corresponding to the first diffraction peak.

### Claim 3 (depends on 1)

The method of claim 1, wherein an intensity of at least a second diffraction peak of the multiple diffraction peaks is determined based on a second dose rate of the second diffraction peak estimated in an integrating mode.

### Claim 4 (depends on 3)

The method of claim 3, wherein estimating the second dose rate of the second diffraction peak in the integrating mode includes estimating the second dose rate based on an accumulated signal corresponding to the second diffraction peak from the multiple frames and a detector conversion efficiency.

### Claim 5 (depends on 4)

The method of claim 4, wherein the intensity of the second diffraction peak is determined further based on a third dose rate of the second diffraction peak estimated in the counting mode.

### Claim 6 (depends on 3)

The method of claim 3, wherein different regions of the diffraction image include noises of different statistical distributions.

### Claim 7

A charged particle microscope, comprising:
an electron source for generating an electron beam;
a sample holder for positioning the sample;
a pixelated detector for receiving electrons from the sample; and
a controller including a non-transitory memory for storing computer readable instructions, by executing the instructions with a processor, the controller is configured to:
irradiate the sample with the electron beam;
acquire multiple frames with the detector;
estimate a first dose rate of at least a diffraction peak in the acquired frames in a counting mode;
responsive to the first dose rate not greater than a threshold dose rate, generate a diffraction image including the diffraction peak by counting electron detection events, wherein values of pixels belonging to the diffraction peak are determined using a first set of counting parameter values corresponding to a first coincidence area, and values of pixels not belonging to any of the multiple diffraction peaks are determined using a second set of counting parameter values corresponding to a second, different, coincidence area;
responsive to the first dose rate higher than a threshold dose rate, estimate a second dose rate of the diffraction peak in an integrating mode;
determine a best estimated dose rate of the diffraction peak based on the first dose rate and the second dose rate; and
generate the diffraction image, wherein an intensity of the diffraction peak is determined based on the best estimated dose rate.

### Claim 8 (depends on 7)

The charged particle microscope of claim 7, wherein acquire multiple frames with the detector includes continuously reading out from multiple detector pixels multiple times before resetting the detector; and obtain the multiple frames by subtracting consecutive readouts.

### Claim 9 (depends on 7)

The charged particle microscope of claim 7, wherein determine a best estimated dose rate of the diffraction peak based on the first dose rate and the second dose rate includes: determine an initial dose rate; determining a first DQE corresponding to the initial dose rate in the counting mode; determining a second DQE corresponding to the initial dose rate in the integrating mode; calculating a weighting factor based on the first DQE and the second DQE; and determining the best estimated dose rate by calculating a weighted sum of the first dose rate and the second dose rate using the weighting factor.