Reducing the impact of charged particle beams in critical dimension analysis

Patent metadata

Field	Value
Publication number	US-9316492-B2
Application number	US-201414454748-A
Country	US
Kind code	B2
Filing date	Aug 8, 2014
Priority date	Aug 8, 2014
Publication date	Apr 19, 2016
Grant date	Apr 19, 2016

Abstract

Measuring a feature on a wafer, the feature including at least two edges. Scanning the wafer with an electron beam over the length of a first scan interval that includes at least a portion of a first edge of the feature. Preventing the electron beam from illuminating the wafer while moving the scan position of the electron beam across a portion of the wafer to a second scan interval that includes at least a portion of a second edge of the feature. Scanning the wafer with an electron beam over the length of the second scan interval. Determining a distance between the first and second edges of the feature.

First claim

What is claimed is:

1. A method for measuring a feature on a wafer using, the feature including at least two edges, the method comprising:
scanning the wafer with an electron beam over the length of a first scan interval that includes at least a portion of a first edge of the feature;
preventing the electron beam from illuminating the wafer while moving the scan position of the electron beam across a portion of the wafer to a second scan interval that includes at least a portion of a second edge of the feature;
scanning the wafer with the electron beam over the length of the second scan interval; and
determining a distance between the first and second edges of the feature.

2. A method in accordance with claim 1 , wherein determining a distance further comprises:
receiving a signal representative of emissions from the feature and/or wafer caused by the interaction of the electron beam and the feature and/or wafer;
analyzing the signal to determine most likely locations for the first and second edges of the feature; and
determining a distance between the most likely locations for the first and second edges of the feature.

3. A method in accordance with claim 1 , wherein scanning the wafer over the length of the first and/or second scan interval further comprises:
aligning the electron beam to the start of the scan interval, wherein aligning includes one or more of: aligning the electron beam to alignment structures on the wafer and indexing over to the start of the scan interval; aligning the electron beam based on design and coordinate information associated with the wafer.

4. A method in accordance with claim 2 , wherein the first and/or second scan intervals are determined based on one or more of: a likelihood of accuracy, above a threshold value, in detecting in the analyzed signal a characteristic signal peak or signal trough associated with an inner or outer feature edge; the cross-sectional dimensions of the scanning electron beam; the feature edge geometry; the analyzed data indicates an intensity peak (or trough) with a departure above a threshold value from the minimum (or maximum) intensity values of the remaining signal data in the interval; a percentage of the signal development range.

5. A method for measuring a feature on a wafer, the method comprising:
aligning an electron beam to the start of a first scan interval that includes a first edge of the feature;
illuminating the wafer with the electron beam when the scan position of the electron beam is at the start of the first scan interval;
scanning the wafer over the length of the first scan interval;
preventing the electron beam from illuminating the wafer when the scan position of the electron beam reaches the end of the first scan interval;
aligning the electron beam to the start of a second scan interval that includes a second edge of the feature;
illuminating the wafer with the electron beam when the scan position of the electron beam is at the start of the second scan interval;
scanning the wafer over the length of the second scan interval; and
preventing the electron beam from illuminating the wafer when the scan position of the electron beam reaches the end of the second scan interval.

6. A method in accordance with claim 5 , further comprising:
receiving a signal representative of emissions from the feature and/or wafer caused by the interaction of the electron beam and the feature and wafer;
analyzing the signal to determine most likely locations for the first and second edges of the feature; and
determining a distance between the most likely locations for the first and second edges of the feature.

7. A method in accordance with claim 5 , wherein aligning the electron beam to the start of the first scan interval and/or aligning the electron beam to the start of the second scan interval comprises one or more of: aligning the electron beam to alignment structures on the wafer and indexing over to the start of the first and/or second scan interval; aligning the electron beam based on design and coordinate information associated with the wafer.

8. A method in accordance with claim 6 , wherein the first and/or second scan intervals are determined based on one or more of: a likelihood of accuracy, above a threshold value, in detecting in the analyzed signal a characteristic signal peak or signal trough associated with an inner or outer feature edge; the cross-sectional dimensions of the scanning electron beam; the feature edge geometry; the analyzed data indicates an intensity peak (or trough) with a departure above a threshold value from the minimum (or maximum) intensity values of the remaining signal data in the interval; a percentage of the signal development range.

9. A method for measuring a feature on a wafer, the feature including at least two edges, the method comprising:
scanning the wafer with an electron beam in a first scan interval that includes at least a portion of a first edge of the feature;
preventing the electron beam from illuminating the wafer while moving the scan position of the electron beam across a portion of the wafer to a second scan interval that includes at least a portion of a second edge of the feature;
scanning the wafer with the electron beam in the second scan interval; and
determining a distance between the first and second edges of the feature, based on a signal representative of emissions from the feature and/or wafer caused by the interaction of the electron beam and the feature and/or wafer.

10. A method in accordance with claim 9 , wherein determining a distance further comprises:
receiving the signal representative of emissions from the feature and/or wafer caused by the interaction of the electron beam and the feature and/or wafer;
analyzing the signal to determine most likely locations for the first and second edges of the feature; and
determining a distance between the most likely locations for the first and second edges of the feature.

11. A method in accordance with claim 9 , wherein scanning the wafer over the length of the first and/or second scan interval further comprises:
aligning the electron beam to the start of the scan interval, wherein aligning includes one or more of: aligning the electron beam to alignment structures on the wafer and indexing over to the start of the scan interval; aligning the electron beam based on design and coordinate information associated with the wafer.

12. A method in accordance with claim 10 , wherein the first and/or second scan intervals are determined based on one or more of: a likelihood of accuracy, above a threshold value, in detecting in the analyzed signal a characteristic signal peak or signal trough associated with an inner or outer feature edge; the cross-sectional dimensions of the scanning electron beam; the feature edge geometry; the analyzed data indicates an intensity peak (or trough) with a departure above a threshold value from the minimum (or maximum) intensity values of the remaining signal data in the interval; a percentage of the signal development range.

Assignees

• IBM

Inventors

• Peterson Kirk D
• Shao Dongbing

Classifications

• H10P74/203

  Structural properties, e.g. testing or measuring thicknesses, line widths, warpage, bond strengths or physical defects · CPC title

• H01J37/28 Primary

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

• G01B15/04 Primary

  for measuring contours or curvatures · CPC title

• H01J2237/2817

  Pattern inspection · CPC title

• H01J2237/2816

  Length · CPC title