Etching process for micromachining crystalline materials and devices fabricated thereby
View Patent ↗The present invention provides an optical microbench having intersecting structures etched into a substrate. In particular, microbenches in accordance with the present invention include structures having a planar surfaces formed along selected crystallographic planes of a single crystal substrate. Two of the structures provided are an etch-stop pit and an anisotropically etched feature disposed adjacent the etch-stop pit. At the point of intersection between the etch-stop pit and the anisotropically etched feature the orientation of the crystallographic planes is maintained. The present invention also provides a method for micromachining a substrate to form an optical microbench. The method comprises the steps of forming an etch-stop pit and forming an anisotropically etched feature adjacent the etch-stop pit. The method may also comprise coating the surfaces of the etch-stop pit with an etch-stop layer.
1. A method for micromachining crystalline substrate, comprising:
providing a crystalline substrate;
directionally etching an etch-stop pit into the substrate;
conformally coating the etch-stop pit with a mask material resistant to a selected anisotropic wet etchant for the substrate; and
anisotropically wet etching an area adjacent to the etch-stop pit with the selected etchant to provide an anisotropic feature in the substrate surface.
2. The method according to claim 1 , wherein the wet etched area abuts a selected portion of the mask.
3. The method according to claim 1 , wherein the etch-stop pit extends into the anisotropic feature.
4. The method according to claim 1 , wherein the anisotropic feature comprises a groove and wherein the etch-stop pit comprises a first sidewall portion that intersects the groove end at a non-orthogonal angle relative to a longitudinal axis of the groove so that at least a portion of a wedge-shaped end portion of the groove is absent.
5. The method according to claim 1 , wherein at least a portion of the anisotropic feature is disposed externally to the etch-stop pit.
6. The method according to claim 1 , wherein at least a portion of the etch-stop pit is disposed externally to the anisotropic feature.
7. The method according to claim 1 , wherein the substrate comprises an upper surface and wherein the etch-stop pit extends into the substrate from the upper surface.
8. The method according to claim 1 , wherein the substrate comprises an upper surface and wherein the anisotropic feature extends into the substrate from the upper surface.
9. The method according to claim 1 , wherein the directional etching comprises at least one of plasma etching, reactive ion etching, or ion milling.
10. The method according to claim 1 , wherein the wet etching comprises etching with at least one of TMAH, KOH, or EDP.
11. The method according to claim 1 , wherein the substrate comprises single crystal silicon.
12. The method according to claim 1 , wherein the mask material comprises at least one of an oxide and a nitride of the substrate material.
13. The method according to claim 1 , wherein the conformal coating comprises thermally oxidizing the surfaces of the etch-stop pit.
14. The method according to claim 1 , comprising removing the mask material.
15. A micromachined crystalline substrate comprising:
a first anisotropically etched groove disposed in a substrate, the groove comprising an end; and
a directionally-etched etch-stop pit comprising a first sidewall portion that intersects the groove end at a non-orthogonal angle relative to a longitudinal axis of the groove so that at least a portion of a wedge-shaped end portion of the groove is absent.
16. The micromachined crystalline substrate according to claim 15 , wherein the first sidewall portion intersects the groove end at a non-orthogonal angle relative to a longitudinal axis of the groove so that a wedge-shaped end portion of the groove is absent.
17. The micromachined crystalline substrate according to claim 15 , wherein the etch-stop pit extends into the groove.
18. The micromachined crystalline substrate according to claim 15 , wherein the etch-stop pit comprises a vertical sidewall.
19. The micromachined crystalline substrate according to claim 15 , wherein at least a portion of the anisotropic feature is disposed externally to the etch-stop pit.
20. The micromachined crystalline substrate according to claim 15 , wherein at least a portion of the etch-stop pit is disposed externally to the anisotropic feature.
21. The micromachined crystalline substrate according to claim 15 , wherein the substrate comprises an upper surface and wherein the etch-stop pit extends into the substrate from the upper surface.
22. The micromachined crystalline substrate according to claim 15 , wherein the substrate comprises an upper surface and wherein the anisotropic feature extends into the substrate from the upper surface.
23. The micromachined crystalline substrate according to claim 15 , wherein the etch-stop pit comprises a triangular cross-sectional shape.
24. The micromachined crystalline substrate according to claim 15 , comprising a fiber disposed in the groove and the etch-stop pit.
25. The micromachined crystalline substrate according to claim 15 , wherein the substrate comprises single crystal silicon.
26. The micromachined crystalline substrate according to claim 15 , wherein the groove comprises a V-groove.
27. The micromachined crystalline substrate according to claim 15 , comprising a second anisotropically etched groove disposed in the substrate, wherein the etch-stop pit is disposed between the first groove and second groove, and wherein the etch-stop pit comprises a second sidewall portion that intersects the second groove end at a non-orthogonal angle relative to a longitudinal axis of the second groove so that at least a portion of a wedge-shaped end portion of the second groove is absent.
28. A micromachined crystalline substrate comprising:
a first anisotropically etched groove disposed in a substrate;
a second anisotropically etched groove in the substrate that intersects the first groove to provide a convex coiner location; and
a directionally-etched etch-stop pit disposed at the convex corner location.
29. A micromachined crystalline substrate comprising an anisotropically etched pit in the substrate, and an etch-stop pit comprising a U-shaped portion, the etch-stop pit intersecting the wet pit.
30. The micromachined crystalline substrate of claim 28 , wherein the etch-stop pit comprises an unetched region interior to the U-shaped portion.
31. A micromachined crystalline substrate comprising:
an anisotropically etched groove disposed in a substrate;
a directionally-etched etch-stop pit disposed within the groove; and
a wedge-shaped protrusion disposed within the groove and adjacent to the etch-stop pit.
32. A micromachined crystalline substrate comprising an anisotropically etched pit and an etch-stop pit circumscribing the anisotropically etched pit.