Method of forming a sample image and charged particle beam apparatus
An object of the present invention is to provide a sample image forming method and a charged particle beam apparatus which are suitable for realizing suppressing of the view area displacement with high accuracy while the influence of charging due to irradiation of the charged particle beam is being suppressed. In order to attain the above object, the present invention provide a method of forming a sample image by scanning a charged particle beam on a sample and forming an image based on secondary signals emitted from the sample, the method comprising the steps of forming a plurality of composite images by superposing a plurality of images obtained by a plurality of scanning times; and forming a further composite image by correcting positional displacements among the plurality of composite images and superposing the plurality of composite images, and a charged particle beam apparatus for realizing the above method.
1. A charged particle beam apparatus comprising:
a charged particle source;
a deflector for scanning a charged particle beam emitted from said charged particle source; and
a detector for detecting secondary signals emitted from a scanned region of said charged particle beam, a sample image being formed based on said secondary signals detected by said detector, which further comprises:
a control unit for forming a plurality of images based on said detected secondary signals, sharpening said formed images, detecting positional displacement between said sharpened images, and superposing images so as to correct the detected positional displacement.
2. A charged particle beam apparatus according to claim 1 , wherein said plurality of images are formed by a unit of two-dimensional scanning performed by said deflector.
3. A charged particle beam apparatus according to claim 1 , wherein said plurality of images are acquired in different timing.
4. A charged particle beam apparatus according to claim 1 , wherein an image shift deflector for shifting a scanning region of said charged particle beam and a sample stage for moving a sample are provided, wherein said control unit detects directions of positional displacements among said sharpened images, and operates said image shift deflector and said sample stage so that said scanning region is positioned toward directions canceling said positional displacements.
5. A charged particle beam apparatus according to claim 1 , wherein said control unit shifts said scanning region using said image shift deflector and said sample stage when an amount of said positional displacement is larger than a preset value, and shifts said scanning region using said image shift deflector when an amount of said positional displacement is smaller than a preset value.
6. A charged particle beam apparatus comprising:
a charged particle source;
a deflector for scanning a charged particle beam emitted from said charged particle source; and
a detector for detecting secondary signals emitted from a scanned region of said charged particle beam, a sample image being formed based on said secondary signals detected by said detector, which further comprises:
a control unit for forming a plurality of images on the basis of said detected secondary signals and forming composite images of said formed images, wherein number of pixels of said formed images before being superimposed is larger than number of pixels of said composite images.
7. A charged particle beam apparatus according to claim 6 , wherein said plurality of images are formed by a unit of two-dimensional scanning performed by said deflector.
8. A charged particle beam apparatus according to claim 6 , wherein said plurality of images are acquired in different timing.
9. A charged particle beam apparatus according to claim 6 , wherein an image shift deflector for shifting a scanning region of said charged particle beam and a sample stage for moving a sample are provided, wherein said control unit detects directions of positional displacements among said composite images, and operates said image shift deflector and said sample stage so that said scanning region is positioned toward directions canceling said positional displacements.
10. A charged particle beam apparatus according to claim 6 , wherein said control unit shifts said scanning region using said image shift deflector and said sample stage when an amount of said positional displacement is larger than a preset value, and shifts said scanning region using said image shift deflector when an amount of said positional displacement is smaller than a preset value.