Determination of lithography misalignment based on curvature and stress mapping data of substrates
View Patent ↗Provided are methods to be carried out prior to, while, and/or after performing a photolithographic process to a wafer that involve wafer misalignment assessment. The method involves obtaining curvature and/or deformation information of a surface of the wafer over a plurality of locations so as to obtain a curvature map of the wafer. The curvature map is processed to obtain a stress map of the wafer. The stress map is used to determine displacement of a layer of the wafer. The displacement information is used to determine a degree of misalignment in the photolithographic process.
1. A method, comprising, prior to, while, and/or after performing a photolithographic process to a wafer:
(a) measuring curvature information of a surface of the wafer over a plurality of locations so as to obtain a curvature map of the wafer;
(b) processing the curvature map to obtain a stress map of the wafer;
(c) using the stress map to determine displacement information for a layer of the wafer; and
(d) using the displacement information to determine a degree of misalignment in the photolithographic process.
2. The method of claim 1 , wherein step (a) is carried out optically.
3. The method of claim 1 , wherein step (a) is carried out through interferometry.
4. The method of claim 3 , wherein step (a) is carried out through full-field interferometry that simultaneously interrogates substantially the entire wafer surface.
5. The method of claim 4 , wherein step (a) is carried out using shearing interferometry.
6. The method of claim 1 , further comprising, before step (a), processing the wafer so as to form and/or alter the layer on the wafer surface.
7. The method of claim 6 , wherein the layer is formed via a deposition process.
8. The method of claim 1 , wherein the layer comprises a plurality of sublayers, and step (d) is carried out for a sublayer selected from the layer.
9. The method of claim 1 , wherein step (b) involves curvature change analysis.
10. The method of claim 1 , wherein step (b) involves lattice strain analysis.
11. The method of claim 9 , wherein step (b) involves X-ray diffraction and/or Raman spectroscopy.
12. The method of claim 1 , wherein step (b) involves computation of driving forces from gradients of in-plane stress components.
13. The method of claim 1 , wherein step (b) involves computation of interfacial shear stress from curvature change based on nonlocal analysis.
14. The method of claim 1 , wherein step (c) involves determining displacement information for the layer relative to a wafer structure of interest.
15. The method of claim 1 , wherein step (c) involves determining displacement information for the layer on the wafer relative to a reference point associated with the photolithographic process.
16. The method of claim 1 , wherein step (d) is carried out in a manner effective to determine whether the degree of misalignment in the photolithographic process falls within a misalignment tolerance budget.
17. The method of claim 16 , further comprising:
(e) performing or continuing the photolithographic process to the wafer only if step (d) reveals that the degree of misalignment falls within a misalignment tolerance budget for the wafer.
18. The method of claim 16 , further comprising:
(e) performing or continuing the photolithographic process to the wafer only if step (d) reveals that the degree of misalignment falls within a misalignment tolerance budget for the photolithographic process.
19. A method, comprising, prior to and/or while performing a photolithographic process to a wafer:
(a) measuring curvature information of a surface of the wafer over a plurality of locations so as to obtain a curvature map of the wafer;
(b) processing the curvature map to obtain a stress map of the wafer;
(c) using the stress map to determine to determine displacement information for a layer on the wafer;
(d) using the displacement information to determine a degree of misalignment in the photolithographic process; and
(e) performing or continuing the photolithographic process to the wafer only if step (d) reveals that the degree of misalignment would not lie outside a measure of tolerance for the photolithographic process.
20. The method of claim 19 , wherein step (e) occurs immediately after step (d).
21. The method of claim 19 , wherein the photolithographic process includes a plurality of subprocesses.
22. The method of claim 21 , wherein at least one subprocess involves inspecting the wafer.
23. The method of claim 21 , wherein at least one subprocess involves adding material to and/or removing material from the wafer.
24. The method of claim 21 , wherein at least one subprocess involves altering at least one portion of the wafer such that the at least one portion of the altered wafer exhibits a characteristic measurably different from that of the wafer in an prealtered state.
25. The method of claim 24 , wherein the at least one portion exhibits an altered electrical conductivity.
26. The method of claim 24 , wherein the at least one portion exhibits an altered microstructure.
27. The method of claim 24 , wherein the at least one portion of the wafer is annealed.
28. The method of claim 24 , wherein the at least one portion of the wafer exhibits a phase change, alloying, ionic chemical reaction, and/or covalent chemical reaction.
29. A method, comprising, prior to, while, and/or after performing a photolithographic process to a wafer:
(a) measuring deformation information of a surface of the wafer over a plurality of locations;
(b) processing the deformation information to obtain a stress and/or strain map of the wafer;
(c) using the stress and/or strain map to determine displacement information for a layer of the wafer; and
(d) using the displacement information to determine a degree of misalignment in the photolithographic process.
30. The method of claim 29 , wherein step (a) involves measuring curvature change.
31. The method of claim 30 , wherein step (a) involves measuring lattice strain.