Measurement system and measurement method

Patent metadata

Field	Value
Publication number	US-10002743-B2
Application number	US-201515305740-A
Country	US
Kind code	B2
Filing date	Apr 21, 2015
Priority date	Apr 25, 2014
Publication date	Jun 19, 2018
Grant date	Jun 19, 2018

Abstract

For scanning electron beams and measuring overlay misalignment between an upper layer pattern and a lower layer pattern with high precision, electron beams are scanned over a region including a first pattern and a second pattern of a sample, the sample having the lower layer pattern (the first pattern) and the upper layer pattern (the second pattern) formed in a step after a step of forming the first pattern. The electron beams are scanned such that scan directions and scan sequences of the electron beams become axial symmetrical or point-symmetrical in a plurality of pattern position measurement regions defined within the scan region for the electron beams, thereby reducing measurement errors resulting from the asymmetry of electric charge.

First claim

The invention claimed is:

1. A measurement system comprising:
a charged particle beam system configured to scan a charged particle beam on a substrate which includes a first pattern and a second pattern formed in a layer above the first pattern; and
a controller configured to control the charged particle beam system to scan the charged particle beam on the substrate according to a predetermined measurement recipe which specifies a scan region including a center of point-symmetry on the substrate, a plurality of measurement regions on the substrate which are symmetrical about the center of point-symmetry, a scan sequence of the charged particle beam which is symmetrical about the center of point-symmetry, and scanning directions of the scan sequence,
wherein the charged particle beam is scanned across the measurement regions a plurality of times according to the scan sequence and the scanning directions thereof to alternate between scanning the charged particle beam in odd-numbered scans on a first side of the center of point symmetry and in even-numbered scans on a second side of the center of point symmetry opposite the first side to obtain an image of the first and second patterns in the measurement regions; and
a processor programmed to:
measure relative positions of the first and second patterns in each of the measurement regions from the obtained image, and
determine an overlay misalignment of the first and second patterns in the scan region from the measured relative positions,
wherein the overlay misalignment is determined for a first axial direction and a second axial direction perpendicular to the first axial direction from the obtained image.

2. The measurement system according to claim 1 , wherein the scanning of the charged particle beam in the odd-numbered scans on the first side of the center of point symmetry have a same scanning direction, and the scanning of the charged particle beam in the even-numbered scans on the second side of the center of point symmetry have a same scanning direction opposite to the scanning direction in the odd-numbered scans.

3. The measurement system according to claim 1 , wherein the scanning of the charged particle beam in the odd-numbered scans on the first side of the center of point symmetry alternate in opposite scanning directions, and the scanning of the charged particle beam in the even-numbered scans on the second side of the center of point symmetry alternate in opposite scanning directions, and
wherein a first of the odd-numbered scans and a first of the even-numbered scans are in opposite directions.

4. The measurement system according to claim 1 , wherein the odd-numbered scans and the even-numbered scans are in parallel and diverge from the center of point-symmetry.

5. The measurement system according to claim 1 , wherein the odd-numbered scans and the even-numbered scans are in parallel and converge towards the center of point-symmetry.

6. The measurement system according to claim 1 , wherein the scanning directions form a predetermined angle with respect to one of the first and second patterns.

7. The measurement system according to claim 1 , wherein the processor is further programmed to:
calculate amounts of overlay misalignment in the measurement regions from the measured relative positions of the first and second patterns in each of the measurement regions, and
display differences in the calculated amounts of overlay misalignment in the measurement regions which are symmetrical with each other about the center of point-symmetry.

8. The measurement system according to claim 7 , wherein the processor is further programmed to:
calculate the overlay misalignment of the scan region as an overall amount of overlay misalignment in the scan region from the respective amounts of overlay misalignment in the measurement regions which are symmetrical with each other about the center of point-symmetry.

9. A measurement system comprising:
a charged particle beam system configured to scan a charged particle beam on a substrate which includes a first pattern and a second pattern formed in a layer above the first pattern; and
a controller configured to control the charged particle beam system to scan the charged particle beam on the substrate according to a predetermined measurement recipe which specifies a scan region including a symmetry axis on the substrate, a plurality of measurement regions on the substrate which are symmetrical about the symmetry axis, a scan sequence of the charged particle beam which is symmetrical about the symmetry axis, and scanning directions of the scan sequence parallel to a first axial direction,
wherein the charged particle beam is scanned across the measurement regions a plurality of times according to the scan sequence and the scanning directions thereof to alternate between scanning the charged particle beam in odd-numbered scans on a first side of the symmetry axis and in even-numbered scans on a second side of the symmetry axis opposite the first side to obtain an image of the first and second patterns in the measurement regions; and
a processor programmed to:
measure relative positions of the first and second patterns in each of the measurement regions from the obtained image, and
determine an overlay misalignment in a second axial direction of the of the first and second patterns in the scan region from the measured relative positions.

10. The measurement system according to claim 9 , wherein the scanning of the charged particle beam in the odd-numbered scans on the first side of the symmetry axis have a same scanning direction, and the scanning of the charged particle beam in the even-numbered scans on the second side of the symmetry axis have the same scanning direction as the odd-numbered scans.

11. The measurement system according to claim 9 , wherein the odd-numbered scans and the even-numbered scans converge towards the symmetry axis.

12. The measurement system according to claim 9 , wherein the processor is further programmed to:
calculate amounts of overlay misalignment in the measurement regions in the second axial direction from the measured relative positions of the first and second patterns in the second axial direction, and
display differences in the calculated amounts of overlay misalignment in the measurement regions.

13. The measurement system according to claim 9 , wherein the processor is further programmed to:
calculate the overlay misalignment of the scan region as an overall amount of overlay misalignment in the scan region from the respective amounts of overlay misalignment in the measurement regions.

14. A measurement method comprising:
scanning a charged particle beam on a substrate, which includes a first pattern and a second pattern formed in a layer above the first pattern, according to a predetermined measurement recipe which specifies a scan region including a center of point-symmetry on the substrate, a plurality of measurement regions on the substrate which are symmetrical about the center of point-symmetry, a scan sequence of the charged particle beam which is symmetrical about the center of point-symmetry, and scanning directions of the scan sequence,
wherein the charged particle beam is scanned across the measurement regions a plurality of times according to the scan sequence and the scanning directions thereof to alternate between scanning the charged particle beam in odd-numbered scans on a first side of the center of point symmetry and in even-numbered scans on a second side of the center of point symmetry opposite the first side to obtain an image of the first and second patterns in the measurem

Assignees

• Hitachi High Tech Corp

Inventors

• Hotta Shoji
• Kawada Hiroki
• Inoue Osamu

Classifications

• G03F7/70633

  Overlay, i.e. relative alignment between patterns printed by separate exposures in different layers, or in the same layer in multiple exposures or stitching · CPC title

• G06T2207/10061

  from scanning electron microscope · CPC title

• G06T7/13

  Edge detection · CPC title

• H01J37/28 Primary

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

• H01J2237/2803

  characterised by the imaging method · CPC title