Optical proximity correction serif measurement technique
First Claim
1. A method of determining the relative area of a serif of a feature present on a photomask, said method comprising:
- identifying a feature having a serif;
determining an intensity profile for a region of interest encompassing said feature with said serif;
summing differences between data points on said profile and a constant value to calculate a flux value; and
calculating a relative area of said serif from said flux value, whereby said relative area is useful for evaluating the quality of said photomask.
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Accused Products
Abstract
An OPC feature measurement technique accurately measures serif area of OPC features, feature separation and line symmetry, and is especially useful for measuring dimensions which are less than about the wavelength of the examining radiation. The relative area of serifs present on a line end is measured by first defining a region of interest around the line end and then an intensity profile is created. The differences between data points on the profile and a constant value are summed in order to calculate a flux value. The flux value is divided by the intensity range to determine an area. The separation distance between a line end and another feature is determined by first defining a region of interest that spans the separation distance between the two features. Next, an intensity profile is created. The differences between data points on the profile and a constant value are summed to calculate a flux value. The separation distance between the features is calculated from the flux value. The asymmetry of serifs of a line present on a photomask is determined by first defining two regions of interest: a shank region of interest that includes the shank of the line and an end region of interest that includes the end of the line. Intensity profiles are created for both regions of interest. The profiles are created by summing values in a longitudinal direction with respect to the line. Finally, an asymmetry area value for the serifs is calculated using the end intensity profile and a centroid of the shank region of interest. The effective diameter, the separation distance and the asymmetry area are useful for evaluating the quality of the photomask.
39 Citations
17 Claims
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1. A method of determining the relative area of a serif of a feature present on a photomask, said method comprising:
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identifying a feature having a serif;
determining an intensity profile for a region of interest encompassing said feature with said serif;
summing differences between data points on said profile and a constant value to calculate a flux value; and
calculating a relative area of said serif from said flux value, whereby said relative area is useful for evaluating the quality of said photomask. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of determining a separation distance between two features present on a photomask, said method comprising:
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defining a region of interest that spans the separation distance between said two features, a portion of each end of said region of interest being fully encompassed by one of said features;
determining an intensity profile for said region of interest;
summing differences between data points on said profile and a constant value to calculate a flux value; and
calculating the separation distance between said features from said flux value, whereby said separation distance is useful for evaluating the quality of said photomask. - View Dependent Claims (8, 9, 10, 11, 12)
defining said region of interest such that said one end of said region is fully encompassed within said line end.
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9. A method as recited in claim 8 wherein the separation distance is less than about twice the wavelength of the examining radiation.
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10. A mask used in the manufacture of semiconductor devices, said mask resulting from a method of determining a separation distance between two features present on a photomask, wherein said method is as recited in any of claims 7 through 9.
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11. A semiconductor device, said semiconductor device resulting from a method of determining a separation distance between two features present on a photomask, wherein said method is as recited in any of claims 7 through 9.
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12. A method as recited in claim 7 wherein the radius of each of said two features is less than about twice the wavelength of the examining radiation.
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13. A method of determining the asymmetry of serifs of a line present on a photomask, said method comprising:
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identifying a line having a line end with at least one serif;
defining a shank region of interest that includes the shank of said line and an end region of interest that includes the end of said line;
determining intensity profiles for both regions of interest, said shank and end profiles being determined by summing values in a longitudinal direction with respect to said line;
calculating an asymmetry area value for said serifs using said end intensity profile and a centroid of said shank region of interest, whereby said asymmetry area is useful for evaluating the quality of said photomask. - View Dependent Claims (14, 15, 16, 17)
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Specification