Scanning charged particle microscope
First Claim
1. A scanning charged particle microscope comprising:
- a charged particle beam source for producing a charged particle beam;
a charged particle beam optical system for focusing the charged particle beam;
a beam deflecting apparatus for causing the focused charged particle beam to perform raster scanning across a sample having a pattern thereon such that each raster scan line is inclined relative to a direction of a boundary of the pattern; and
a control unit for changing a focal point of the focused beam for each raster scan line, comparing an image definition between successive raster scan lines, and determining an in-focus point based on the comparison.
1 Assignment
0 Petitions
Accused Products
Abstract
The present invention sets out to provide a scanning charged particle microscope equipped with a rapid control function capable of extrapolating an in-focus point from image information for a single frame and an automatic focusing system capable of reliably and precisely carrying out a focusing operation for a horizontal pattern image. The automatic focusing system provided in the scanning charged particle microscope of the present invention is provided with means for changing a focal point each raster scan line, and control means for comparing image information each scanning line and extrapolating focusing positions. The scanning line can then be made to be an inclined scanning line that is a combination of a horizontal component and a vertical component with respect to a chip array on a semiconductor wafer. Further, a method is adopted comprising a first step of reliably taking in a coarse in-focus point and a second step of detecting the in-focus point with a high degree of precision.
-
Citations
15 Claims
-
1. A scanning charged particle microscope comprising:
- a charged particle beam source for producing a charged particle beam;
a charged particle beam optical system for focusing the charged particle beam;
a beam deflecting apparatus for causing the focused charged particle beam to perform raster scanning across a sample having a pattern thereon such that each raster scan line is inclined relative to a direction of a boundary of the pattern; and
a control unit for changing a focal point of the focused beam for each raster scan line, comparing an image definition between successive raster scan lines, and determining an in-focus point based on the comparison. - View Dependent Claims (2, 3, 4, 5)
- a charged particle beam source for producing a charged particle beam;
-
6. A method for performing automatic focusing in a scanning charged particle microscope which irradiates and scans a charged particle beam over a sample having a pattern thereon and obtains a sample image, comprising the steps of:
-
scanning the charged particle beam across the pattern in such a manner that each scan line is inclined relative to a boundary of the pattern;
changing a focal point of the charged particle beam for each scan line;
comparing image definition between images obtained for each scan line; and
obtaining a position where the clearest image definition is obtained as an in-focus point. - View Dependent Claims (7, 8, 9, 10, 11)
-
-
12. A scanning charged particle microscope for irradiating and scanning with a charged particle beam semiconductor chips arranged in a two-dimensional matrix extending in first and second directions on a semiconductor wafer to obtain a sample image, comprising:
-
scanning means for performing raster scanning of the semiconductor chips with the charged particle beam in such a manner that each scan line is inclined relative to the first and second directions of the semiconductor chips on the semiconductor wafer;
focal point changing means for changing a focal point for each scan line; and
control means for comparing an image definition between successive images obtained for each scan line and determining an in-focus point therefrom. - View Dependent Claims (13, 14, 15)
-
Specification