Methodology for post-integration awareness in optical proximity correction
A method of creating an optical proximity correction (OPC) model and assessing the model through optical rule checking (ORC) includes the introduction of post-integration, i.e., post-metallization data. High density critical dimension scanning electron microscopy and backscattered electron scanning electron microscopy from a metallized structure are used during development and verification of the model to accurately predict post-integration behavior.
1. A method of verifying an optical proximity correction (OPC) rule set, comprising:
collecting critical dimension scanning electron microscope (CDSEM) data from a post-integration structure, wherein the post-integration structure includes:
a first metal level having a first conductive structure, and
a second metal level above the first metal level and having a second conductive structure horizontally separated from the first conductive structure;
constructing a post-integration OPC model using the post-integration CDSEM data;
performing optical rule checking (ORC) on the optical proximity correction (OPC) rule set using the post-integration OPC model to identify post-integration weak points within the structure, wherein at least one of the post-integration weak points includes a bridge defect between the first conductive structure and the second conductive structure;
verifying the post-integration weak points to create a verified OPC rule set; and
producing a photomask using the verified OPC rule set.
2. The method of claim 1 , wherein the CDSEM data comprises a backscattered critical dimension scanning electron microscope (BSE CDSEM) compositional image including the first metal level and the second metal level.
3. The method of claim 1 , wherein the post-integration CDSEM data corresponds to a metal trench pattern.
4. The method of claim 1 , wherein the first conductive structure includes a lower metal wire, and wherein the second conductive structure includes an upper via.
5. The method of claim 4 , wherein verifying the post-integration weak points comprises measuring a distance between a top surface of the lower metal wire and a bottom surface of the upper via within the structure.
6. The method of claim 5 , wherein the measured distance includes a horizontal component and a vertical component.
7. The method of claim 1 , wherein verifying the post-integration weak points utilizes at least one metrology technique selected from a group consisting of high energy critical dimension scanning electron microscopy, transmission electron microscopy and electron beam spectroscopy.
8. A method of verifying an optical proximity correction (OPC) rule set, comprising:
collecting image data from a post-integration structure, wherein the post-integration structure includes:
a first metal level having a first conductive structure, and
a second metal level above the first metal level and having a second conductive structure horizontally separated from the first conductive structure;
generating a post-integration OPC model using the image data of the post-integration structure;
performing optical rule checking (ORC) on the optical proximity correction (OPC) rule set using the post-integration OPC model to identify post-integration weak points within the structure, wherein at least one of the post-integration weak points includes a bridging region between the first conductive structure and the second conductive structure;
modifying the OPC rule set to correct for the identified post-integration weak points; and
producing a photomask using the modified OPC rule set.
9. The method of claim 8 , wherein the image data of the post-integration structure comprises a backscattered critical dimension scanning electron microscope (BSE CDSEM) image.
10. The method of claim 8 , wherein the image data of the post-integration structure corresponds to a metal trench pattern.
11. The method of claim 8 , wherein the first conductive structure includes a lower metal wire, and wherein the second conductive structure includes an upper via.
12. The method of claim 11 , further comprising verifying the post-integration weak points.
13. The method of claim 12 , wherein verifying the post-integration weak points comprises measuring a distance between a top surface of the lower metal wire and a bottom surface of the upper via within the structure.
14. The method of claim 13 , wherein the measured distance includes a horizontal component and a vertical component.
15. The method of claim 12 , wherein verifying the post-integration weak points utilizes at least one metrology technique selected from a group consisting of high energy critical dimension scanning electron microscopy, transmission electron microscopy and electron beam spectroscopy.