Process for etching trenches in an integrated optical device

• US 20060068554A1
• Filed: 09/19/2005
• Published: 03/30/2006
• Est. Priority Date: 09/17/2004
• Status: Abandoned Application

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Montanini, Pietro, Gelmi, Ilaria, Mottura, Marta, Germani, Giovanna
• Application Number:
  US11/230,292
• Publication Number:
  US 20060068554A1
• Time in Patent Office: Days
• US Class Current: 438/296
• CPC Class Codes: H01L 21/0332 characterised by their composition, e.g. multilayer masks, materials
• CPC Class Codes: H01L 21/0334 characterised by their size, orientation, disposition, behaviour, shape, in horizontal or vertical plane
• CPC Class Codes: H01L 21/31116 by dry-etching
• CPC Class Codes: H01L 21/31144 using masks

Abstract

The described process allows trenches to be etched in a structure comprising a support substrate and a multilayer, formed on the substrate, for the definition of wave guides of an integrated optical device and comprises a selective plasma attack in the multilayer through a masking structure that leaves uncovered areas of the multilayer corresponding to the trenches to be etched. Such a masking structure is obtained by forming a mask of metallic material on the multilayer that leaves uncovered the areas corresponding to the trenches to be etched and forming a mask of non-metallic material, for example photoresist, on it that leaves uncovered regions comprising at least part of the areas and an edge portion of the mask of metallic material.

Claims

1. Process for etching trenches in a structure comprising a support substrate and a multilayer, formed on the substrate, comprising a core layer and coating layers for the definition of wave guides of an integrated optical device, the process comprising a selective plasma attack in the multilayer through a masking structure that leaves uncovered areas of the multilayer corresponding to the trenches to be etched and being

wherein the masking structure is obtained with the following successive operations:

forming a mask of metallic material on the multilayer that leaves uncovered the areas corresponding to the trenches to be etched and

forming a mask of non-metallic material that leaves uncovered regions comprising at least part of the areas corresponding to the trenches to be etched and an edge portion of the mask of metallic material.

2. Process for etching trenches according to claim 1, wherein the operation of forming the mask of non-metallic material leaves uncovered regions comprising the areas corresponding to the trenches to be etched and an edge portion of the mask of metallic material.

3. Process for etching trenches according to claim 1, wherein the mask of metallic material leaves uncovered further areas of the multilayer not corresponding to the trenches to be etched.

4. Process for etching trenches according to claim 1, wherein the operation of formation of the mask of non-metallic material is preceded by operations for the formation of other structures of the integrated optical device.

5. Process for etching trenches according to claim 1, wherein the non-metallic material comprises a photoresist.

6. Process for etching trenches according to claim 1, wherein the attack comprises a low-density plasma attack.

7. Process for etching trenches according to claim 1, wherein the attack comprises a high-density plasma attack.

8. A method, comprising:

forming on a material a metallic first mask that exposes a region of the material;

forming on the first mask a second mask that exposes a section of the region and a portion of the first mask that is contiguous with the section of the region; and

forming a trench in the exposed section of the material.

9. The method of claim 8, further comprising:

forming on a substrate a first optical layer having a first index of refraction;

forming on the first layer a second optical layer having a second index of refraction; and

forming on the second layer a third optical layer having a third index of refraction, the first, second, and third layers composing the material.

10. The method of claim 8, further comprising removing the first and second masks after forming the trench.

11. The method of claim 8 wherein forming the first mask comprises forming the first mask only within predetermined distance from a perimeter of the region.

12. The method of claim 8 wherein forming the second mask comprises forming the second mask such that the second mask exposes the entire region of the material and exposes a portion of the first mask that is contiguous with multiple sides of the region.

13. The method of claim 8 wherein forming the second mask comprises forming the second mask such that the second mask exposes a section that is smaller than the entire region of the material and exposes only a portion of the first mask that is contiguous with fewer than all sides of the section.

14. The method of claim 8 wherein forming the second mask comprises forming the second mask such that the second mask exposes a section that is smaller than the entire region of the material and exposes only a portion of the first mask that is contiguous with a single side of the section.

15. The method of claim 8 wherein forming the trench comprises anisotropically etching the exposed section of the material.

16. The method of claim 8 wherein forming the trench comprises plasma etching the exposed section of the material.

17. The method of claim 8 wherein forming the second mask comprises forming the second mask from a non-metallic material.

18. A structure, comprising:

an optical path having a surface and through which an optical signal can propagate; and

a trench disposed in the path, having a first side wall that is substantially perpendicular to the surface, and having a bottom that is substantially flat and substantially parallel to the surface.

19. The structure of claim 18 wherein the trench further comprises a second side wall that is substantially perpendicular to the surface of the optical path.

20. The processor of claim 18 wherein the trench further comprises a second side wall that forms an angle other than 90°

with the surface of the optical path.

21. The structure of claim 18 wherein the trench further comprises a second side wall that is substantially perpendicular to the surface of the optical path and that is substantially parallel to the first side wall.

22. The structure of claim 18 wherein the optical path comprises:

a first optical layer having a first index of refraction;

a second optical layer disposed on the first optical layer and having a second index of refraction; and

a third optical layer disposed on the second optical layer, having a third index of refraction, and having a surface that forms the surface of optical path.

23. The structure of claim 22 wherein the first index of refraction substantially equals the third index of refraction.

24. The structure of claim 22 wherein:

the first index of refraction substantially equals the third index of refraction; and

the second index of refraction is greater than the first and third indices of refraction.

25. The structure of claim 22 wherein the trench is disposed at an end of the optical path.

26. An integrated circuit, comprising:

an optical path having a surface and through which an optical signal can propagate; and

a trench disposed in the path, having a first side wall that is substantially perpendicular to the surface, and having a bottom that is substantially flat and substantially parallel to the surface.

27. An electronic system, comprising:

an integrated circuit having,

an optical path having a surface and through which an optical signal can propagate, and

a trench disposed in the path, having a first side wall that is substantially perpendicular to the surface, and having a bottom that is substantially flat and substantially parallel to the surface.