Metrology method and apparatus, and device manufacturing method
An approach is used to estimate and correct the overlay variation as function of offset for each measurement. A target formed on a substrate includes periodic gratings. The substrate is illuminated with a circular spot on the substrate with a size larger than each grating. Radiation scattered by each grating is detected in a dark-field scatterometer to obtain measurement signals. The measurement signals are used to calculate overlay. The dependence (slope) of the overlay as a function of position in the illumination spot is determined. An estimated value of the overlay at a nominal position such as the illumination spot's center can be calculated, correcting for variation in the overlay as a function of the target's position in the illumination spot. This compensates for the effect of the position error in the wafer stage movement, and the resulting non-centered position of the target in the illumination spot.
1. A method of determining a property of a target comprising at least one periodic structure, the target formed by a lithographic process on a substrate, the method comprising:
illuminating the substrate with a beam of radiation, having an illumination region on the substrate with a size larger than at least one periodic structure of the target;
detecting radiation scattered by the at least one periodic structure at a plurality of positions in the illumination region; and
calculating a value of the property of the target corresponding to a nominal position of the at least one periodic structure in the illumination region when the radiation was detected, by using the detected radiation and correcting for variation of the property as a function of the at least one periodic structure's position in the illumination region.
2. A method of determining a property of a target comprising at least one periodic structure, the target formed by a lithographic process on a substrate, the method comprising:
illuminating the substrate with a beam of radiation, having an illumination region on the substrate with a size larger than at least one periodic structure of the target;
detecting radiation scattered by the at least one periodic structure at a plurality of positions in the illumination region; and
calculating a value of the property of the target corresponding to a nominal position of the at least one periodic structure in the illumination region when the radiation was detected, by using the detected radiation and correcting for variation of the property as a function of the at least one periodic structure's position in the illumination region;
determining a dependence of a scattering property obtained from the detected radiation as a function of position in the illumination region; and
determining the position offset of at least one of the at least one periodic structure,
wherein the calculating includes using the determined dependence and the determined position offset.
3. A method of determining a property of a target comprising at least one periodic structure, the target formed by a lithographic process on a substrate, the method comprising:
illuminating the substrate with a beam of radiation, having an illumination region on the substrate with a size larger than at least one periodic structure of the target;
detecting radiation scattered by the at least one periodic structure at a plurality of positions in the illumination region; and
calculating a value of the property of the target corresponding to a nominal position of the at least one periodic structure in the illumination region when the radiation was detected, by using the detected radiation and correcting for variation of the property as a function of the at least one periodic structure's position in the illumination region,
wherein the detecting is performed while at least one of the illumination region and the target are moved relative to each other along a path with the at least one periodic structure passing fully through the illumination region; and
integrating at least one measurement signal along the path,
wherein the calculating includes using the at least one integrated measurement signal.
4. An inspection apparatus configured for determining a property of a target comprising at least one periodic structure, the target formed by a lithographic process on a substrate, the inspection apparatus comprising:
an illumination arrangement operable to illuminate the substrate with a beam of radiation, having an illumination region on the substrate with a size larger than at least one periodic structure of the target;
a detection arrangement operable to detect radiation scattered by the at least one periodic structure at a plurality of positions in the illumination region; and
a computational arrangement operable to calculate a value of the property of the target corresponding to a nominal position of the at least one periodic structure in the illumination region when the radiation was detected, by using the detected radiation and correcting for variation of the property as a function of the at least one periodic structure's position in the illumination region.
5. An inspection apparatus configured for determining a property of a target comprising at least one periodic structure, the target formed by a lithographic process on a substrate, the inspection apparatus comprising:
an illumination arrangement operable to illuminate the substrate with a beam of radiation, having an illumination region on the substrate with a size larger than at least one periodic structure of the target;
a detection arrangement operable to detect radiation scattered by the at least one periodic structure at a plurality of positions in the illumination region; and
a computational arrangement operable to:
determine a dependence of a scattering property obtained from the detected radiation as a function of position in the illumination region;
determine the position offset of at least one of at least one the periodic structure; and
calculate a value of the property of the target corresponding to a nominal position of the at least one periodic structure in the illumination region when the radiation was detected, by using the detected radiation and correcting for variation of the property as a function of the at least one periodic structure's position in the illumination region using the determined dependence and the determined position offset.
6. An inspection apparatus configured for determining a property of a target comprising at least one periodic structure, the target formed by a lithographic process on a substrate, the inspection apparatus comprising:
an illumination arrangement operable to illuminate the substrate with a beam of radiation, having an illumination region on the substrate with a size larger than at least one periodic structure of the target;
a detection arrangement operable to detect radiation scattered by the at least one periodic structure at a plurality of positions in the illumination region; and
a computational arrangement operable to calculate a value of the property of the target corresponding to a nominal position of the at least one periodic structure in the illumination region when the radiation was detected, by using the detected radiation and correcting for variation of the property as a function of the at least one periodic structure's position in the illumination region;
a movement arrangement operable to move at least one of the illumination region and the target relative to each other, and
wherein the detection arrangement is further operable to detect radiation while at least one of the illumination region and the target are moved relative to each other along a path with the at least one periodic structure passing fully through the illumination region; and
wherein the computational arrangement is further operable to integrate at least one measurement signal along the path and to calculate the value of the property of the target using the at least one integrated measurement signal.
7. A lithographic system comprising:
a lithographic apparatus comprising:
an illumination optical system arranged to illuminate a pattern;
a projection optical system arranged to project an image of the pattern onto a substrate; and
an inspection apparatus configured for determining a property of a target comprising at least one periodic structure, the target formed by a lithographic process on a substrate, the inspection apparatus comprising:
an illumination arrangement operable to illuminate the substrate with a beam of radiation, having an illumination region on the substrate with a size larger than at least one periodic structure of the target;
a detection arrangement operable to detect radiation scattered by the at least one periodic structure at a plurality of positions in the illumination region; and
a computational arrangement operable to calculate a value of the property of the target corresponding to a nominal position of the at least one periodic structure in the illumination region when the radiation was detected, by using the detected radiation and correcting for variation of the property as a function of the at least one periodic structure's position in the illumination region,
wherein the lithographic apparatus is arranged to use the determined property from the inspection apparatus in applying the pattern to further substrates.
8. A method of manufacturing devices wherein a device pattern is applied to a series of substrates using a lithographic process, the method comprising:
inspecting at least one target comprising at least one periodic structure formed as part of or beside the device pattern on at least one of the substrates, the inspecting comprises:
illuminating the substrate with a beam of radiation, having an illumination region on the substrate with a size larger than at least one periodic structure of the target;
detecting radiation scattered by the at least one periodic structure at a plurality of positions in the illumination region; and
calculating a value of the property of the target corresponding to a nominal position of the at least one periodic structure in the illumination region when the radiation was detected, by using the detected radiation and correcting for variation of the property as a function of the at least one periodic structure's position in the illumination region; and
controlling the lithographic process for later substrates in accordance with the result of the inspection method.
9. A method comprising:
illuminating a substrate with a beam of radiation, having an illumination region on the substrate with a size larger than at least one periodic structure of a target on the substrate;
detecting radiation scattered by the at least one periodic structure at a plurality of positions in the illumination region; and
calculating a value of the property of the target corresponding to a nominal position of the at least one periodic structure in the illumination region when the radiation was detected, by using the detected radiation and correcting for variation of the property as a function of the at least one periodic structure's position in the illumination region.
10. A method comprising:
illuminating a substrate with a beam of radiation, having an illumination region on the substrate with a size larger than at least one periodic structure of a target on the substrate;
detecting radiation scattered by the at least one periodic structure at a plurality of positions in the illumination region; and
calculating a value of the property of the target corresponding to a nominal position of the at least one periodic structure in the illumination region when the radiation was detected, by using the detected radiation and correcting for variation of the property as a function of the at least one periodic structure's position in the illumination region;
determining a dependence of a scattering property obtained from the detected radiation as a function of position in the illumination region; and
determining the position offset of at least one of the at least one periodic structure,
wherein the calculating includes using the determined dependence and the determined position offset.
11. A method comprising:
illuminating a substrate with a beam of radiation, having an illumination region on the substrate with a size larger than at least one periodic structure of a target on the substrate;
detecting radiation scattered by the at least one periodic structure at a plurality of positions in the illumination region; and
calculating a value of the property of the target corresponding to a nominal position of the at least one periodic structure in the illumination region when the radiation was detected, by using the detected radiation and correcting for variation of the property as a function of the at least one periodic structure's position in the illumination region,
wherein the detecting is performed while at least one of the illumination region and the target are moved relative to each other along a path with the at least one periodic structure passing fully through the illumination region;
integrating at least one measurement signal along the path, and
wherein the calculation includes using the at least one integrated measurement signal.
12. An inspection apparatus comprising:
an illumination arrangement configured to illuminate a substrate with a beam of radiation, having an illumination region on the substrate with a size larger than at least one periodic structure of a target on the substrate;
a detection arrangement configured to detect radiation scattered by the at least one periodic structure at a plurality of positions in the illumination region; and
a computational arrangement configured to calculate a value of the property of the target corresponding to a nominal position of the at least one periodic structure in the illumination region when the radiation was detected, by using the detected radiation and correcting for variation of the property as a function of the at least one periodic structure's position in the illumination region.
13. An inspection apparatus comprising:
an illumination arrangement operable to illuminate a substrate with a beam of radiation, having an illumination region on the substrate with a size larger than at least one periodic structure of a target on the substrate;
a detection arrangement operable to detect radiation scattered by the at least one periodic structure at a plurality of positions in the illumination region; and
a computational arrangement operable to:
determine a dependence of a scattering property obtained from the detected radiation as a function of position in the illumination region;
determine the position offset of at least one of at least one the periodic structure; and
calculate a value of the property of the target corresponding to a nominal position of the at least one periodic structure in the illumination region when the radiation was detected, by using the detected radiation and correcting for variation of the property as a function of the at least one periodic structure's position in the illumination region using the determined dependence and the determined position offset.
14. An inspection apparatus comprising:
an illumination arrangement operable to illuminate a substrate with a beam of radiation, having an illumination region on the substrate with a size larger than at least one periodic structure of a target on the substrate;
a detection arrangement operable to detect radiation scattered by the at least one periodic structure at a plurality of positions in the illumination region;
a computational arrangement operable to calculate a value of the property of the target corresponding to a nominal position of the at least one periodic structure in the illumination region when the radiation was detected, by using the detected radiation and correcting for variation of the property as a function of the at least one periodic structure's position in the illumination region; and
a movement arrangement operable to move at least one of the illumination region and the target relative to each other,
wherein: the detection arrangement is further operable to detect radiation while at least one of the illumination region and the target are moved relative to each other along a path with the at least one periodic structure passing fully through the illumination region;
and the computational arrangement is further operable to integrate at least one measurement signal along the path and to calculate the value of the property of the target using the at least one integrated measurement signal.
15. A lithographic system comprising:
a lithographic apparatus comprising:
an illumination optical system arranged to illuminate a pattern;
a projection optical system arranged to project an image of the pattern onto a substrate; and
an inspection apparatus comprising,
an illumination arrangement configured to illuminate a substrate with a beam of radiation, having an illumination region on the substrate with a size larger than at least one periodic structure of a target on the substrate;
a detection arrangement configured to detect radiation scattered by the at least one periodic structure at a plurality of positions in the illumination region; and
a computational arrangement configured to calculate a value of the property of the target corresponding to a nominal position of the at least one periodic structure in the illumination region when the radiation was detected, by using the detected radiation and correcting for variation of the property as a function of the at least one periodic structure's position in the illumination region,
wherein the lithographic apparatus is arranged to use the determined property from the inspection apparatus in applying the pattern to further substrates.
16. A method of manufacturing devices wherein a device pattern is applied to a series of substrates using a lithographic process, the method including inspecting at least one target comprising at least one periodic structure formed as part of or beside the device pattern on at least one of the substrates using an inspection method comprising:
illuminating a substrate with a beam of radiation, having an illumination region on the substrate with a size larger than at least one periodic structure of a target on the substrate;
detecting radiation scattered by the at least one periodic structure at a plurality of positions in the illumination region; and
calculating a value of the property of the target corresponding to a nominal position of the at least one periodic structure in the illumination region when the radiation was detected, by using the detected radiation and correcting for variation of the property as a function of the at least one periodic structure's position in the illumination region, and
controlling the lithographic process for later substrates in accordance with the result of the inspection method.