Scanning Transmission Electron Microscope and Method of Image Generation

Patent metadata

Field	Value
Publication number	US-2018337019-A1
Application number	US-201715824047-A
Country	US
Kind code	A1
Filing date	Nov 28, 2017
Priority date	Nov 28, 2016
Publication date	Nov 22, 2018
Grant date	—

Abstract

There is provided a scanning transmission electron microscope capable of producing plural types of STEM (scanning transmission electron microscopy) images using a single detector. The electron microscope ( 100 ) has an electron source ( 10 ) emitting an electron beam, a scanning deflector ( 13 ) for scanning the beam over a sample (S), an objective lens ( 14 ) for focusing the beam, an imager ( 22 ) placed at a back focal plane of the objective lens ( 14 ) or at a plane conjugate with the back focal plane, and a scanned image generator ( 40 ) for generating scanned images on the basis of images captured by the imager. The scanned image generator ( 40 ) operates to form electron diffraction patterns from the electron beam passing through positions on the sample by the scanning of the electron beam, to capture the electron diffraction patterns by the imager so that plural images are produced, to integrate the intensity of each pixel over an integration region that is set based on the size of an image of a transmitted wave in a respective one of the produced images for each of the produced images such that the signal intensity at each position on the sample is found, and to generate the scanned images on the basis of the signal intensities at the positions on the sample.

First claim

The invention claimed is:

1 . A scanning transmission electron microscope adapted to produce scanned images by scanning an electron beam over a sample, said scanning transmission electron microscope comprising:
an electron source for emitting an electron beam; a scanning deflector for scanning the emitted electron beam over the sample; an objective lens for converging the electron beam emitted from the electron source; an imager placed at a back focal plane of the objective lens or at a plane conjugate with the back focal plane; and a scanned image generator for generating the scanned images on the basis of images captured by the imager, wherein the scanned image generator operates to form electron diffraction patterns from the electron beam passing through positions on the sample by scanning of the electron beam, to capture the electron diffraction patterns by the imager so that plural images are produced, to integrate the intensity of each pixel over an integration region that is set based on the size of an image of a transmitted wave within a respective one of the produced images such that the signal intensity at each position on the sample is found for each of the produced images, and to generate the scanned images on the basis of the signal intensities at the positions on the sample.

2 . The scanning transmission electron microscope as set forth in claim 1 , wherein the image of said transmitted wave in the image captured by said imager appears as a disk, and wherein the size of the image of the transmitted wave is the diameter of the disk.

3 . The scanning transmission electron microscope as set forth in claim 1 , wherein said scanned image generator operates to measure the size of the image of said transmitted wave from the image captured by said imager and to set said integration region on the basis of the measured size of the image of the transmitted wave.

4 . The scanning transmission electron microscope as set forth in claim 1 , wherein during the operation for finding the signal intensity at each position on the sample, said scanned image generator finds the signal intensity at each position on the sample for each of the plural set integration regions, and where during the operation for generating the scanned images, the scanned image generator generates the scanned images corresponding to the plural integration regions.

5 . The scanning transmission electron microscope as set forth in claim 1 , wherein said integration regions are inside the image of said transmitted wave and are circular regions whose centers lie at the center of the image of the transmitted wave.

6 . The scanning transmission electron microscope as set forth in claim 1 , wherein said integration regions are inside the image of said transmitted wave and are annular regions whose centers lie at the center of the image of the transmitted wave.

7 . The scanning transmission electron microscope as set forth in claim 1 , wherein said integration regions are outside and surround the image of said transmitted wave and are annular regions whose centers lie at the center of the image of the transmitted wave.

8 . The scanning transmission electron microscope as set forth in claim 1 , wherein said integration regions are inside the image of said transmitted wave and are two regions which are symmetrical with respect to the center of the image of the transmitted wave.

9 . The scanning transmission electron microscope as set forth in claim 1 , further comprising:
a first deflector for deflecting the electron beam incident on said sample; a second deflector for deflecting the electron beam incident on said imager; and a processor for controlling the first and second deflectors, wherein the processor operates to control the first deflector such that the azimuthal angle of the electron beam incident on the sample is scanned, to obtain an accumulation image consisting of an accumulation of images each containing a transmitted wave and diffracted waves in a respective one of electron diffraction patterns produced at different values of the azimuthal angle, to extract the image of the transmitted wave from the accumulation image, and to control the second deflector on the basis of the position of the extracted image of the transmitted wave such that the image of the transmitted wave is placed at the center of the image captured by the imager.

10 . A method of generating images in a scanning transmission electron microscope by scanning an electron beam incident on a sample and producing scanned images, said method comprising the steps of:
forming electron diffraction patterns from the electron beam that is caused to pass through positions on the sample by the scanning of the electron beam; capturing the electron diffraction patterns by an imager to thereby produce plural images; integrating the intensity of each pixel of the produced images over an integration region that is set based on the size of an image of a transmitted wave in a respective one of the produced images for each of the produced images to find the signal intensity at each position on the sample; and generating the scanned images on the basis of the signal intensities at the positions on the sample.

Assignees

• Jeol Ltd

Inventors

• Sagawa Ryusuke

Classifications

• G01N2223/102

  beta or electrons · CPC title

• G01N23/20058

  Measuring diffraction of electrons, e.g. low energy electron diffraction [LEED] method or reflection high energy electron diffraction [RHEED] method · CPC title

• H01J37/28 Primary

  with scanning beams {(H01J37/268, H01J37/292, H01J37/2955 take precedence)} · CPC title

• G01N2223/418

  electron microscope · CPC title

• G01N2223/0565

  diffraction of electrons, e.g. LEED · CPC title