High accuracy beam placement for local area navigation
First Claim
1. A method for high accuracy beam placement and navigation to a feature of interest within a local area on a sample surface, comprising:
- loading a sample into a sample imaging system employing a moveable sample stage, and said sample imaging system including computer hardware and non-transitory computer memory storing computer instruction embodying a computer program;
acquiring a first image of a local area on the sample using the sample imaging system at a first field of view, the first field of view being large enough to insure that the location of a feature of interest is included in the image based considering the accuracy of the imaging system, the first image including the location of the feature of interest and one or more alignment points near the feature of interest, and said first image also having a resolution such that the image pixel size is equal to or smaller than the alignment points;
superimposing a coordinate system overlay on the first image, with the computer program, the coordinate system overlay representing idealized coordinates of features on the sample surface;
registering the first image with the coordinate system with the computer program using a plurality of alignment points in the first image and corresponding idealized elements in the coordinate system overlay;
after the image and the coordinate system have been registered, navigating the sample imaging system to the location of the feature of interest in the acquired first image using the known coordinates from the coordinate system;
identifying one or more transfer fiducials in the first image, wherein said transfer fiducials comprise unique visible features on the sample surface that can be easily identified;
recording the offset between the transfer fiducials and the feature of interest with the computer program;
acquiring a second image of the sample surface using the sample imaging system at a second field of view, said second field of view being smaller than the first field of view and including the feature of interest and the one or more transfer fiducials;
identifying the one or more transfer fiducials in the second image;
using the recorded offset between the transfer fiducials and the feature of interest to precisely navigate the sample of imaging system to the location of the feature of interest.
1 Assignment
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Accused Products
Abstract
An improved method of high accuracy beam placement for local area navigation in the field of semiconductor chip manufacturing. This invention demonstrates a method where high accuracy navigation to the site of interest within a relatively large local area (e.g. an area 200 μm×200 μm) is possible even where the stage/navigation system is not normally capable of such high accuracy navigation. The combination of large area, high-resolution scanning, digital zoom and registration of the image to an idealized coordinate system enables navigation around a local area without relying on stage movements. Once the image is acquired any sample or beam drift will not affect the alignment. Preferred embodiments thus allow accurate navigation to a site on a sample with sub-100 nm accuracy, even without a high-accuracy stage/navigation system.
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Citations
35 Claims
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1. A method for high accuracy beam placement and navigation to a feature of interest within a local area on a sample surface, comprising:
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loading a sample into a sample imaging system employing a moveable sample stage, and said sample imaging system including computer hardware and non-transitory computer memory storing computer instruction embodying a computer program; acquiring a first image of a local area on the sample using the sample imaging system at a first field of view, the first field of view being large enough to insure that the location of a feature of interest is included in the image based considering the accuracy of the imaging system, the first image including the location of the feature of interest and one or more alignment points near the feature of interest, and said first image also having a resolution such that the image pixel size is equal to or smaller than the alignment points; superimposing a coordinate system overlay on the first image, with the computer program, the coordinate system overlay representing idealized coordinates of features on the sample surface; registering the first image with the coordinate system with the computer program using a plurality of alignment points in the first image and corresponding idealized elements in the coordinate system overlay; after the image and the coordinate system have been registered, navigating the sample imaging system to the location of the feature of interest in the acquired first image using the known coordinates from the coordinate system; identifying one or more transfer fiducials in the first image, wherein said transfer fiducials comprise unique visible features on the sample surface that can be easily identified; recording the offset between the transfer fiducials and the feature of interest with the computer program; acquiring a second image of the sample surface using the sample imaging system at a second field of view, said second field of view being smaller than the first field of view and including the feature of interest and the one or more transfer fiducials; identifying the one or more transfer fiducials in the second image; using the recorded offset between the transfer fiducials and the feature of interest to precisely navigate the sample of imaging system to the location of the feature of interest. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 26, 27)
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20. A method for accurately locating a feature of interest on a sample in a particle beam system, comprising:
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loading a sample into a particle beam system employing a movable sample stage, and using the particle beam system to carry of the steps of; imaging a target area of the sample with a particle beam to obtain a first image, the target area including the location of a feature of interest and one or more additional visible alignment features having known coordinates, said first image being of a high enough resolution that the first image pixel size is no more than twice the size of any of said alignment features; superimposing a graphical representation of a coordinate system over the first image, the coordinate system using idealized geometric shapes to represent the locations of visible features within the target area; locating the one or more alignment features having known coordinates within the first image; determining an offset error between the superimposed coordinate system and the first image; aligning the coordinate system with the first image; locating within the first image one or more unique visible sample features on the surface of the sample to serve as transfer fiducials; recording the offset between the transfer fiducials and the location of the feature of interest; acquiring a second image of the sample with a particle beam at the location of the feature of interest, the second image having a smaller field of view than the first image; locating the transfer fiducials in the second image; locating the feature of interest within the second image using the recorded offset between the transfer fiducials and the feature of interest; using the location of the feature of interest to control the placement of a particle beam; and processing the sample using the particle beam. - View Dependent Claims (21, 22, 23, 24, 25, 28, 29, 30)
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31. A method for navigating a sample without relying on stage movements, the sample having a target area with a feature of interest and one or more alignment points, the method comprising loading the sample into a sample imaging system, said sample imaging system including a computer program embodied in computer instructions stored in non-transitory computer memory and executed on a computer hardware system for carrying out the following steps:
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acquiring a first image of the target area; overlaying the image with an idealized coordinate system of alignment points within the target area; locating one or more of the alignment points within the image near the feature of interest; aligning the idealized coordinate system with the image; locating one or more unique features on the sample within the target area but separated from the sample; recording the offset between the feature of interest and the unique features in the first image; acquiring a new image of the sample with a smaller field of view, the new image including the feature of interest; and locating the feature of interest in the new image. - View Dependent Claims (32)
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33. An apparatus for accurately locating a feature of interest on a sample, comprising:
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a moveable sample stage for supporting the sample; a particle beam column for producing a beam of particles to image the sample; and a computer-readable memory storing computer instructions, the instructions including a program for controlling the apparatus and causing the apparatus to carry out the steps of; (i) acquiring a first image of the target area; (ii) overlaying the image with an idealized coordinate system of alignment points within the target area; (iii) precisely locate one or more of the alignment points within the image near the feature of interest; (iv) aligning the idealized coordinate system with the image; (v) locating one or more unique features on the sample within the target area but separated from the sample; (vi) recording the offset between the feature of interest and the unique features in the first image; (vii) acquiring a new image of the sample with a smaller field of view, the new image including the feature of interest; (viii) locating the feature of interest in the new image; and (ix) using the location of the feature of interest to control the placement of a particle beam relative to the sample. - View Dependent Claims (34, 35)
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Specification