Microscopic corner radius measurement system

• US 6,397,165 B1
• Filed: 06/07/2001
• Issued: 05/28/2002
• Est. Priority Date: 02/28/1997
• 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): SHAH, KAMINI S
• Application Number:
  US09/877,647
• Time in Patent Office: 355 Days
• Field of Search: 702/157,159,95 348/128 356/241,254,429,430 355/53,67-69
• US Class Current: 702/157
• CPC Class Codes: G01N 21/956 Inspecting patterns on the surface of objects contactless testing of electronic circuits G01R31/308; testing currency G07D; manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10
• CPC Class Codes: G03F 1/84 Inspecting

Abstract

A measurement tool connects to a microscope for identifying and measuring microscopic dimensions of features on a photographic mask such as area, diameter and corner radius. Dimensions of features having sizes of less than about twice the wavelength being used (less than 1 micron for visible light) are measured quickly and accurately. The radius of curvature is also determined at submicron sizes using a flux measurement. Determination of the expected flux of a perfect comer aids in the measurement.

Claims

1. A method of determining the radius of curvature of a microscopic corner feature located on a medium, said method comprising:

determining the location of the perfect corner of said corner feature;

calculating an expected flux value for a region of interest around said corner feature assuming that said corner feature were the perfect corner;

calculating an actual flux value for said corner region of interest around said corner feature;

calculating an eroded area flux value from said expected flux value and said actual flux value; and

calculating the radius of curvature of said corner feature using said eroded area flux value.

2. A method as recited in claim 1 wherein said radius of curvature is less than about twice the wavelength used in said method.

3. A method as recited in claim 1 wherein said step of determining the location of the perfect corner includes the sub-steps of:

defining a vertical and a horizontal region of interest across edges that define said corner feature; and

determining an X-Y coordinate position for said location of the perfect corner using said vertical and horizontal regions of interest.

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

defining said corner region of interest around said corner feature using rough approximations for the X-Y coordinate positions of said perfect corner location.

5. A method as recited in claim 1 wherein said step of calculating an expected flux value includes the sub-step of:

calculating an expected flux value for said region of interest around said corner feature using a background intensity and a foreground intensity of said corner region of interest.

6. A computer-readable medium comprising computer code for determining the radius of curvature of a microscopic corner feature located on a medium, said computer code of said computer-readable medium effecting the following:

determining the location of the perfect corner of said corner feature;

calculating an expected flux value for a region of interest around said corner feature assuming that said corner feature were the perfect corner;

calculating an actual flux value for said corner region of interest around said corner feature;

calculating an eroded area flux value from said expected flux value and said actual flux value; and

calculating the radius of curvature of said corner feature using said eroded area flux value.

7. A computer-readable medium as recited in claim 6 wherein said radius of curvature is less than about twice the wavelength used in said method.

8. A computer-readable medium as recited in claim 6 further comprising computer code for effecting the following:

defining a vertical and a horizontal region of interest across edges that define said corner feature; and

determining an X-Y coordinate position for said location of the perfect corner using said vertical and horizontal regions of interest.

9. A computer-readable medium as recited in claim 6 further comprising computer code for effecting the following:

defining said corner region of interest around said corner feature using rough approximations for the X-Y coordinate positions of said perfect corner location.

10. A computer-readable medium as recited in claim 6 further comprising computer code for effecting the following:

calculating an expected flux value for said region of interest around said corner feature using a background intensity and a foreground intensity of said corner region of interest.