Method for fabricating micro optical elements using CMP
View Patent ↗A technique for fabricating the required surface shapes for micro optical elements, such as curved micro mirrors and lenses, starts with a simple, binary for example, approximation to the desired surface shape. Then polishing, e.g., chemical mechanical polishing (CMP), is used to form the smooth optical surface. Specifically, starting with a mesa or blind hole, with a mesa profile, a smooth mirror or lens structure is fabricated.
1. A method for fabricating micro-optical elements, comprising:
forming topographic features on a surface of an optical element substrate;
mechanically polishing the surface of the substrate to modify the features to produce curved optical surfaces on the optical element substrate; and
dicing the substrate into the optical elements.
2. A method as claimed in claim 1 , wherein the step of forming the topographic features comprises forming blind holes into the substrate.
3. A method as claimed in claim 1 , wherein the step of forming the topographic features comprises forming blind holes, having mesa profiles, into the substrate.
4. A method as claimed in claim 1 , wherein the step of forming the topographic features comprises forming a feature projecting from the substrate.
5. A method as claimed in claim 1 , wherein the step of forming the topographic features comprises forming mesas in the substrate.
6. A method as claimed in claim 1 , wherein the step of forming the topographic features comprises etching a blind holes into the sub skate to a depth of a material layer.
7. A method as claimed in claim 1 , wherein the step of forming the topographic features comprises etching blind holes into the substrate in a timed process.
8. A method as claimed in claim 1 , wherein the step of polishing the surface comprises performing chemical mechanical polishing of the surface.
9. A method as claimed in claim 1 , further comprising optically coating the surface after the polishing step.
10. A method as claimed in claim 9 , wherein the step of optically coating the surface comprises depositing a highly reflective layer on the surface.
11. A method as claimed in claim 9 , wherein the step of optically coating the surface comprises depositing an antireflective layer on the surface.
12. A method as claimed in claim 1 , further comprising optically coating the surface after the polishing step and before the dicing step.
13. A method as claimed in claim 1 , wherein the step of dicing the substrate comprises sawing the substrate.
14. A method as claimed in claim 1 , wherein the step of dicing the substrate comprises cleaving the substrate.
15. A method as claimed in claim 1 , wherein the step of forming the topographic features on the surface of the optical element substrate comprises forming the features on silicon or gallium phosphide wafer material.
16. A method for fabricating reflective micro-optical elements with a concave curvature, comprising:
forming blind holes into a surface of an optical element substrate;
mechanically polishing the surface of the substrate to modify the blind holes to produce curved, concave optical surfaces on the optical element substrate;
coating the optical element substrate with a reflective coating; and
dicing the substrate into the concave optical elements.
17. A method as claimed in claim 1 , wherein the step of dicing is performed in two directions to thereby separate a two dimensional array of optical elements into discrete optical elements.
18. A method as claimed in claim 1 , wherein sidewalls of the topographic features extend substantially orthogonally to the surface of the substrate.
19. A method as claimed in claim 16 , wherein the step of dicing is performed in two directions to thereby separate a two dimensional array of optical elements into discrete concave optical elements.
20. A method as claimed in claim 16 , wherein the sidewalls of the blind holes are substantially orthogonal to the surface of the substrate.