Simulation-assisted metrology image alignment
A method for aligning a measured image of a pattern printed on a substrate with a design layout. The method includes: obtaining a design layout of a pattern to be printed on a substrate and a measured image of the pattern printed on the substrate; performing a simulation process to generate a plurality of simulated contours of the design layout for a plurality of process conditions of a patterning process; identifying a set of disfavored locations based on the simulated contours; and performing an image alignment process to align the measured image with a selected contour of the simulated contours using locations other than the set of disfavored locations.
1 . A non-transitory computer-readable medium having instructions that, when executed by a computer system, are configured to cause the computer system to at least:
obtain a design layout of a pattern to be printed on a substrate and a measured image of the pattern printed on the substrate;
perform a simulation process to generate simulated contours of the design layout for a plurality of process conditions of a patterning process;
identify a set of disfavored locations based on the simulated contours, wherein the identification of a disfavored location is based on (a) a deviation between the location and a corresponding location on a contour of the measured image meeting or crossing a first threshold, (b) a process condition variation at the location meeting or crossing a second threshold, (c) a determination that the simulated contours are asymmetric at the location, or (d) a determination that one or more of the simulated contours are broken at the location; and
perform an image alignment process to align the measured image with a selected contour of the simulated contours using locations other than the set of disfavored locations.
2 . The computer-readable medium of claim 1 , wherein the instructions are further configured to cause the computer system to:
determine a parameter associated with the measured image based on the image alignment process, and
adjust, based on the parameter, at least one selected from: the design layout, a patterning device having the design layout, or the patterning process.
3 . The computer-readable medium of claim 1 , wherein the instructions configured to cause the computer system to perform the simulation process are further configured to cause the computer system to generate each of the simulated contours for a different process condition.
4 . The computer-readable medium of claim 3 , wherein each of the process conditions includes a lens effect of an apparatus used to print the pattern on the substrate and/or a resist effect of a resist on the substrate.
5 . The computer-readable medium of claim 1 , wherein the instructions configured to cause the computer system to perform the simulation process are further configured to cause the computer system to:
obtain a mask design layout by performing an optimal proximity correction process on the design layout, and
generate the simulated contours based on the design layout and the mask design layout.
6 . The computer-readable medium of claim 1 , wherein the selected contour corresponds to a nominal process condition.
7 . The computer-readable medium of claim 1 , wherein the instructions are further configured to cause the computer system to: identify a set of favored locations on the simulated contours based on (a) a deviation between a location on the simulated contours and corresponding location on a contour of the measured image satisfying a third threshold, (b) a process condition variation at a location on a contour satisfying a fourth threshold, or (c) a determination that the simulated contours are symmetric at a location on the simulated contours, and
wherein the instructions configured to cause the computer system to perform the alignment process are further configured to cause the computer system to perform the image alignment process between the measured image and the selected contour at a plurality of locations on the simulated contours, wherein the plurality of locations includes the set of favored locations.
8 . The computer-readable medium of claim 7 , wherein the instructions configured to cause the computer system to perform the alignment process are further configured to cause the computer system to exclude the set of disfavored locations from the plurality of locations for the image alignment process.
9 . The computer-readable medium of claim 1 , wherein the instructions are further configured to cause the computer system to:
perform a measurement to obtain a deviation between the selected contour and a contour of the measured image at a set of favored locations, and
adjust the selected contour at the set of favored locations for reducing the deviation, wherein the adjustment generates an adjusted selected contour.
10 . The computer-readable medium of claim 9 , wherein the instructions are further configured to cause the computer system to perform the image alignment process between the measured image and the adjusted selected contour at the set of favored locations.
11 . The computer-readable medium of claim 9 , wherein the instructions are further configured to cause the computer system to:
perform a simulation process to generate a predicted measured image from the adjusted selected contour, and
perform the image alignment process between the measured image and the predicted measured image at the set of favored locations.
12 . The computer-readable medium of claim 1 , wherein the instructions are further configured to cause the computer system to:
perform a simulation process to generate a predicted measured image from the selected contour, and
perform the image alignment process between the measured image and the predicted measured image at a set of favored locations.
13 . The computer-readable medium of claim 12 , wherein the instructions are further configured to cause the computer system to:
adjust the predicted measured image to reduce a deviation between a contour of the predicted measured image and a contour of the measured image at the set of favored locations, wherein the adjustment generates an adjusted predicted measured image, and
perform the image alignment process between the measured image and the adjusted predicted measured image at the set of favored locations.
14 . The computer-readable medium of claim 1 , wherein the measured image is obtained using an image capture device.
15 . An apparatus comprising:
a memory storing a set of instructions; and
at least one processor configured to execute the set of instructions to cause the apparatus to at least:
obtain a design layout of a pattern to be printed on a substrate and a measured image of the pattern printed on the substrate;
perform a simulation process to generate simulated contours of the design layout for a plurality of process conditions of a patterning process;
identify a set of favored locations based on the simulated contours, wherein the identification of a favored location is based on (a) a deviation between a location on the simulated contours and corresponding location on a contour of the measured image satisfying a third threshold, (b) a process condition variation at a location on a contour satisfying a fourth threshold, or (c) a determination that the simulated contours are symmetric at a location on the simulated contours; and
perform an image alignment process to align the measured image with a selected contour of the simulated contours using locations including the set of favored locations.
16 . A non-transitory computer-readable medium having instructions that, when executed by a computer system, cause the computer system to at least:
obtain a design layout of a pattern to be printed on a substrate and a measured image of the pattern printed on the substrate;
perform a simulation process to generate simulated results of the design layout for a plurality of process conditions of a patterning process;
identify a set of locations for image alignment based on the simulated results, wherein the identification of a location to be within the set of locations is based on (a) a deviation between the location and a corresponding location on a contour of the measured image meeting or crossing a first threshold, (b) a process condition variation at the location meeting or crossing a second threshold, (c) a determination that simulated contours of the simulated results are asymmetric at the location, (d) a determination that simulated contours of the simulated results are symmetric at the location, or (e) a determination that one or more of simulated contours of the simulated results are broken at the location; and
perform an image alignment process between the measured image and the design layout by aligning the measured image with a selected result of the simulated results using the set of locations.
17 . The computer-readable medium of claim 16 , wherein the instructions are further configured to cause the computer system to perform a simulation process to generate a predicted measured image from the selected result, and
wherein the instructions configured to cause the computer system to perform the image alignment process are further configured to cause the computer system to align the measured image with the predicted measured image using the set of locations.
18 . The computer-readable medium of claim 17 , wherein the instructions are further configured to cause the computer system to:
adjust the predicted measured image to reduce a deviation between a contour of the predicted measured image and a contour of the measured image at the set of locations, wherein the adjustment generates an adjusted predicted measured image, and
perform the image alignment process between the measured image and the adjusted predicted measured image at the set of locations.
19 . The computer-readable medium of claim 16 , wherein the instructions are further configured to cause the computer system to:
determine a parameter associated with the measured image based on the image alignment process, and
adjust, based on the parameter, at least one selected from: the design layout, a patterning device having the design layout, or the patterning process.
20 . The computer-readable medium of claim 19 , wherein the instructions are further configured to cause the computer system to:
determine a parameter associated with the measured image based on the image alignment process, and
adjust, based on the parameter, at least one selected from: the design layout, a patterning device having the design layout, or the patterning process.