Automated method for determining several critical dimension properties from scanning electron microscope by using several tilted beam or sample scans
First Claim
1. A method for extracting structural information on a workpiece by having a scanning electron microscope (SEM) scan the workpiece to acquire waveform information at a plurality of tilt angles, wherein the process of extracting the structural information extends beyond the resolution of the SEM, the method comprising the steps of:
- (a) setting an SEM beam to a first/next tilt angle;
(b) scanning across a region of the workpiece at the tilt angle to acquire a waveform;
(c) analyzing the waveform to extract a Distance between Extremal Slope Locations (DESL) value for each edge of interest;
(d) determining whether there are two acceptable DESL values for each structural edge by comparing each DESL value to a DESL threshold value;
wherein, if there are at least two of said DESL values that arc greater than said DESL threshold value, then sufficient information has been obtained, and else, returning to step a), and (e) determining the height and the sidewall angle of the structure on the workpiece, wherein when both of said DESL values are greater than at least 1.5 times the DESL threshold value, then a geometrical analysis extracts the height and sidewall angle of the structure on the workpiece, and when either of said two DESL values is smaller than at least 1.5 times said DESL threshold value, then the geometrical analysis is modified to include limitations in the resolution of the SEM.
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Abstract
To obtain data pertaining to the surface characteristics of a sample, a control method adjusts a tilted rastered E-beam to in SEM to a first/next tilt condition and navigates the SEM-beam to a sample site. The system performs a fine alignment step. Then the system scans a region of a sample to acquire a waveform. The system analyzes the waveform to determine the DESL value for each edge of interest. The system tests whether there is sufficient information available for each structural edge. If NO, the system repeats the above steps starting by changing the value of the tilt angle to acquire another waveform. If YES, the system determines the height and sidewall angles for each structural edge. Then the system reports the sidewall angle and the structure height for each edge of the structure under test. The system then corrects the critical dimension measurement determined from 0 degrees tilt scanning.
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Citations
17 Claims
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1. A method for extracting structural information on a workpiece by having a scanning electron microscope (SEM) scan the workpiece to acquire waveform information at a plurality of tilt angles, wherein the process of extracting the structural information extends beyond the resolution of the SEM, the method comprising the steps of:
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(a) setting an SEM beam to a first/next tilt angle;
(b) scanning across a region of the workpiece at the tilt angle to acquire a waveform;
(c) analyzing the waveform to extract a Distance between Extremal Slope Locations (DESL) value for each edge of interest;
(d) determining whether there are two acceptable DESL values for each structural edge by comparing each DESL value to a DESL threshold value;
wherein, if there are at least two of said DESL values that arc greater than said DESL threshold value, then sufficient information has been obtained, and else, returning to step a), and(e) determining the height and the sidewall angle of the structure on the workpiece, wherein when both of said DESL values are greater than at least 1.5 times the DESL threshold value, then a geometrical analysis extracts the height and sidewall angle of the structure on the workpiece, and when either of said two DESL values is smaller than at least 1.5 times said DESL threshold value, then the geometrical analysis is modified to include limitations in the resolution of the SEM. - View Dependent Claims (2, 3, 4)
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5. A method for making Scanning Electron Microscope (SEM) scans of a workpiece comprising:
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(a) setting an SEM beam to a first/next deflection tilt angle, (b) scanning across a region of the workpiece at the deflection tilt angle to acquire a waveform, (c) analyzing a waveform to determine a DESL value for each edge of interest, (d) determining whether there is sufficient information for each structural edge and if NO returning to step (a) and if YES proceeding to step (e), (e) determining height (H) and sidewall angle values for each structural edge, and (f) determining height (H) and sidewall angle for each structural edge; and
performing the calculations as follows;
- View Dependent Claims (6, 7, 8)
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9. A method for processing edge and sidewall data comprising:
fitting DESL (Distance between Extremal Slope Locations) to the data for all angles, beam and sample conditions by using the formula as follows;
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10. An apparatus for extracting structural information on a workpiece for having a scanning electron microscope (SEM) scan the workpiece to acquire waveform information at a plurality of tilt angles, wherein the process of extracting the structural information extends beyond the resolution of the SEM, the apparatus comprising
(a) means for setting an SEM bearn to a first/next tilt angle, (b) means for scanning across a region of the workpiece at the tilt angle to acquire a waveform; -
(c) means for analyzing the waveform to extract a Distance between Extremal Slope Locations (DESL) value for each edge of interest;
(d) means for determining whether there are two acceptable DESL values for each structural edge by comparing each DESL value to a DESL threshold value;
wherein, if there are at least two of said DESL values that are greater than said DESL threshold value, then sufficient information has been obtained, and else, returning to step a), and(e) means for determining the height and the sidewall angle of the structure on the workpiece, wherein when both of said DESL values are greater than at least 1.5 times the DESL threshold value, then a geometrical analysis extracts the height and sidewall angle of the structure on the workpiece, and when either of said two DESL values is smaller than at least 15 times said DESL threshold value, then the geometrical analysis is modified to include limitations in the resolution of the SEM. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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15. The apparatus of claim 11 including means for performing the calculations as follows:
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16. The apparatus of claim 11 including means for performing the calculations as follows:
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17. Apparatus for processing edge and sidewall data comprising:
means for fitting DESL (Distance between Extremal Slope Locations) to the data for all angles, beam and sample conditions by using the formula as follows;
Specification