Microscopic feature dimension measurement system

• US 6,539,331 B1
• Filed: 09/08/2000
• Issued: 03/25/2003
• Est. Priority Date: 09/08/2000
• Status: Expired due to Term

• Current Assignee: Kla-Tencor Technologies Corporation (KLA Corporation)
• Original Assignee: Peter J. Fiekowsky
• Inventors: Fiekowsky, Peter J.
• Primary Examiner(s): Barlow, John
• Assistant Examiner(s): LE, JOHN H
• Application Number:
  US09/657,920
• Time in Patent Office: 928 Days
• Field of Search: 702/95, 702/159, 356/237, 356/241, 356/429, 356/430, 356/431, 355/53, 355/67, 355/68, 355/69, 355/71, 250/563, 250/559.42, 250/559.48, 250/559.49, 250/560, 250/572, 430/5
• US Class Current: 702/159
• CPC Class Codes: G03F 1/86 by charged particle beam [CPB]

Abstract

A measurement tool connects to an automatic inspection machine for measuring microscopic characteristics of features on a photographic mask. Widths of densely packed lines are measured for features having sizes of less than about the wavelength of the examining radiation. A simulated intensity profile is subtracted from the actual measured intensity profile to obtain an error profile. The error profile provides edge position corrections which adjust the originally estimated edge positions. A new, simulated intensity profile is created and the process is repeated until the error profile is deemed acceptable. The line width is measured by measuring between the estimated edge positions. The opacity of a feature is determined and used for correcting dimension measurements. A formula determines the opacity based upon the contrast, the measured dimension and the single data point. Width or height of an irregular feature is calculated accurately. Dimension of the feature is determined using the peak width data and the peak width standard deviation.

Claims

1. A method of measuring a dimension of a microscopic feature in the presence of an interfering feature, the distance between said feature to be measured and said interfering feature is less than about 1.5 times the wavelength used to measure said feature, said method comprising:

receiving an image of a region of interest, said region of interest including an image of said feature to be measured and an image of an edge of said interfering feature;

determining an intensity profile for said region of interest;

calculating estimated edge positions for the edges of said feature to be measured and said interfering feature;

creating a simulated intensity profile for said region of interest based upon said estimated edge positions;

determining an error intensity profile representing the difference between said intensity profile and said simulated intensity profile; and

calculating new estimated edge positions using said error intensity profile, whereby the dimension of said microscopic feature may be calculated using said new estimated edge positions.

2. A method as recited in claim 1 further comprising repeating the following until an error is acceptable:

recreating a simulated intensity profile for said region of interest based upon said newly calculated estimated edge positions;

determining an error intensity profile representing the difference between said intensity profile and said recreated simulated intensity profile; and

calculating new estimated edge positions using said error intensity profile.

3. A method as recited in claim 1 wherein said element of creating a simulated intensity profile includes the sub-steps of:

convolving reference edge profiles to obtain an individual simulated profile for each of said feature to be measured and for said interfering feature; and

adding said individual simulated profiles of said feature and said interfering feature to create said simulated intensity profile.

4. A method as recited in claim 1 further comprising:

creating a simulated interfering edge profile;

subtracting said simulated interfering edge profile from said intensity profile to obtain an isolated intensity profile of said feature to be measured; and

determining said dimension of said feature to be measured using said isolated intensity profile.

5. A method as recited in claim 1 wherein said feature is a line and said dimension is the width of said line.

6. A method as recited in claim 1 wherein said feature is present on a mask used to manufacture a semiconductor device.

13. A mask used in the manufacture of semiconductor devices, said mask resulting from a method of measuring a dimension of a microscopic feature in the presence of an interfering feature, wherein said method is as recited in any of claims 1 through 12.

14. A semiconductor device, said semiconductor device resulting from a method of measuring a dimension of a microscopic feature in the presence of an interfering feature on a mask, wherein said method is as recited in any of claims 1 through 12.

7. A method of measuring a dimension of a microscopic feature in the presence of an interfering feature, the distance between said feature to be measured and said interfering feature is less than about 1.5 times the wavelength used to measure to said feature, said method comprising:

receiving an intensity profile for a region of interest, said region of interest including an image of said feature to be measured and an image of an edge of said interfering feature;

estimating edge positions for the edges of said feature to be measured and said interfering feature;

creating a simulated intensity profile for said region of interest based upon said estimated edge positions;

calculating edge positions errors for the edges of said feature to be measured and said interfering feature using said intensity profile and said simulated intensity profile; and

calculating new estimated edge positions using said edge positions errors, whereby the dimension of said microscopic feature may be calculated using said new estimated edge positions.

8. A method as recited in claim 7 further comprising repeating the following until said edge positions errors are acceptable:

recreating a simulated intensity profile for said region of interest based upon said newly calculated estimated edge positions;

recalculating edge positions errors for the edges of said feature to be measured and said interfering feature using said intensity profile and said recreated simulated intensity profile; and

calculating new estimated edge positions using said edge positions errors.

9. A method as recited in claim 7 wherein said element of creating a simulated intensity profile includes the sub-steps of:

convolving reference edge profiles to obtain an individual simulated profile for each of said feature to be measured and for said interfering feature; and

adding said individual simulated profiles of said feature and said interfering feature to create said simulated intensity profile.

10. A method as recited in claim 7 further comprising:

creating a simulated interfering edge profile;

subtracting said simulated interfering edge profile from said intensity profile to obtain an isolated intensity profile of said feature to be measured; and

determining said dimension of said feature to be measured using said isolated intensity profile.

11. A method as recited in claim 7 wherein said feature is a line and said dimension is the width of said line.

12. A method as recited in claim 7 wherein said feature is present on a mask used to manufacture a semiconductor device.