Stitching methods using multiple microlithographic expose tools
View Patent ↗A method for producing a measurement structure for measuring alignment of patterns formed in one or more layers of patternable material uses multiple exposure tools having different resolution limits and maximum expose field sizes. The measurement structure includes multiple complementary and coincident parts. An abutting field pattern is exposed and stitched in a layer of patternable material using a first exposure tool and a first mask. The abutting field pattern includes a first portion of the multiple complementary parts. A periphery pattern is exposed in the same layer or in a different layer of patternable material using a second exposure tool and a second mask. The periphery pattern includes a second portion of the multiple complementary parts. A maximum expose field of the first exposure tool is smaller than the maximum expose field of the second exposure tool.
1. A method for producing a completed measurement structure using (i) a first exposure tool having a first maximum expose field, (ii) a second exposure tool having a second maximum expose field larger than the first maximum expose field, (iii) a first mask defining one or more unit-cell patterns and one or more first-alignment-feature patterns proximate the one or more unit-cell patterns, and (iv) a second mask defining a periphery pattern for at least partially surrounding a plurality of the unit-cell patterns and, proximate the periphery pattern, one or more second-alignment-feature patterns, the method comprising:
utilizing the first exposure tool, exposing a layer of photosensitive material through the first mask in a plurality of different locations such that, after the first exposure, each subsequent exposure exposes, a) in the layer of photosensitive material, one of the unit-cell patterns abutting at least one of the previous unit-cell patterns thereby forming an abutting field pattern in the layer of photosensitive material and exposes, b) in the layer of photosensitive material, one of the first-alignment-feature patterns overlapping at least one of the previous first-alignment-feature patterns, thereby forming a partially complete measurement structure in the layer of photosensitive material;
utilizing the second exposure tool, exposing the layer of photosensitive material through the second mask to form the periphery pattern in the layer of photosensitive material at least partially surrounding the abutting field pattern, the exposure through the second mask exposing one of the second-alignment-feature patterns to overlap the at least two overlapping first-alignment-feature patterns; and
developing the layer of photosensitive material to remove a portion thereof, wherein unremoved portions of the layer of photosensitive material where the second-alignment-feature pattern overlapped the at least two overlapping first-alignment-feature patterns defines the completed measurement structure.
2. The method as in claim 1 , wherein (i) the photosensitive material comprises positive photoresist, and (ii) developing the photosensitive material removes the portion thereof exposed to light through at least one of the first mask or the second mask.
3. The method as in claim 1 , wherein (i) the photosensitive material comprises negative photoresist, and (ii) developing the photosensitive material removes the portion thereof not exposed to light through the first mask or the second mask.
4. The method as in claim 1 , wherein a numerical aperture of the first exposure tool is between 0.35 and 1.0.
5. The method as in claim 1 , wherein a numerical aperture of the second exposure tool is less than 0.35.
6. A method for producing a completed measurement structure in a first layer of photosensitive material and a second layer of photosensitive material disposed over a substrate using (i) a first exposure tool having a first maximum expose field, (ii) a second exposure tool having a second maximum expose field larger than the first maximum expose field, (iii) a first mask defining one or more unit-cell patterns and one or more first-alignment-feature patterns proximate the one or more unit-cell patterns, and (iv) a second mask defining a periphery pattern for at least partially surrounding a plurality of the unit-cell patterns and, proximate the periphery pattern, one or more second-alignment-feature patterns, the method comprising:
forming the first layer of photosensitive material over the substrate;
utilizing the first exposure tool, exposing the first layer of photosensitive material through the first mask in a plurality of different locations such that, after the first exposure, each subsequent exposure exposes, a) in the first layer of photosensitive material, one of the unit-cell patterns abutting at least one of the previous unit-cell patterns thereby forming an abutting field pattern in the first layer of photosensitive material, and exposes, b) in the first layer of photosensitive material, one of the first-alignment-feature patterns overlapping at least one of the previous first-alignment-feature patterns, thereby forming a partially complete measurement structure in the first layer of photosensitive material;
developing the first layer of photosensitive material to remove portions thereof;
forming the second layer of photosensitive material over the developed first layer of photosensitive material;
utilizing the second exposure tool, exposing the second layer of photosensitive material through the second mask to form the periphery pattern in the second layer of photosensitive material at least partially surrounding the abutting field pattern defined in the first layer of photosensitive material, the exposure through the second mask exposing one of the second-alignment-feature patterns to overlap the at least two overlapping first-alignment-feature patterns defined in the first layer of photosensitive material; and
developing the second layer of photosensitive material to remove portions thereof, wherein unremoved portions of the second layer of photosensitive material where the second-alignment-feature pattern overlapped the at least two overlapping first-alignment-feature patterns defined in unremoved portions of the first layer of photosensitive material together defines the completed measurement structure.
7. The method as in claim 6 , further comprising determining offsets for the first and second exposure tools based on alignment of the first-alignment-feature patterns and the second-alignment-feature patterns within the measurement structure.
8. The method as in claim 6 , wherein (i) the first and second layers of photosensitive material comprise positive photoresist, and (ii) developing the first and second layers of photosensitive material removes the portions thereof exposed to light through at least one of the first mask or the second mask.
9. The method as in claim 6 , wherein (i) the first and second layers of photosensitive material comprise negative photoresist, and (ii) developing the first and second layers of photosensitive material removes the portions thereof not exposed to light through the first mask or the second mask.
10. The method as in claim 6 , wherein a numerical aperture of the first exposure tool is between 0.35 and 1.0.
11. The method as in claim 6 , wherein a numerical aperture of the second exposure tool is less than 0.35.