WAVEGUIDE MIRROR AND METHOD OF FABRICATING A WAVEGUIDE MIRROR

• US 20190302366A1
• Filed: 03/28/2019
• Published: 10/03/2019
• Est. Priority Date: 03/29/2018
• Status: Active Grant

• Current Assignee: Rockley Photonics Limited
• Original Assignee: Rockley Photonics Limited
• Inventors: Nykanen, Henri, Drake, John Paul, Kho, Evie, Lerose, Damiana, Makela, Sanna Leena, Nagra, Amit Singh
• Granted Patent: US 10,641,962 B2
• Time in Patent Office: Days
• CPC Class Codes: G02B 2006/12061 Silicon
• CPC Class Codes: G02B 2006/12104 Mirror; Reflectors or the like
• CPC Class Codes: G02B 2006/12176 Etching
• CPC Class Codes: G02B 2006/12178 Epitaxial growth
• CPC Class Codes: G02B 6/12004 Combinations of two or more optical elements
• CPC Class Codes: G02B 6/125 Bends, branchings or intersections
• CPC Class Codes: G02B 6/136 by etching
• CPC Class Codes: G02B 6/26 Optical coupling means G02B6/36, G02B6/42 take precedence
• CPC Class Codes: G02B 6/4214 the intermediate optical element having redirecting reflective means, e.g. mirrors, prisms for deflecting the radiation from horizontal to down- or upward direction toward a device G02B6/4246 takes precedence

Abstract

A mirror and method of fabricating the mirror, the method comprising: providing a silicon-on-insulator substrate, the substrate comprising: a silicon support layer; a buried oxide (BOX) layer on top of the silicon support layer; and a silicon device layer on top of the BOX layer; creating a via in the silicon device layer, the via extending to the BOX layer; etching away a portion of the BOX layer starting at the via and extending laterally away from the via in a first direction to create a channel between the silicon device layer and silicon support layer; applying an anisotropic etch via the channel to regions of the silicon device layer and silicon support layer adjacent to the channel; the anisotropic etch following an orientation plane of the silicon device layer and silicon support layer to create a cavity underneath an overhanging portion of the silicon device layer; the overhanging portion defining a planar underside surface for vertically coupling light into and out of the silicon device layer; and applying a metal coating to the underside surface.

Claims

1. A method of fabricating a mirror, the method comprising:

providing a silicon-on-insulator substrate, the substrate comprising;

a silicon support layer;

a buried oxide (BOX) layer on top of the silicon support layer; and

a silicon device layer on top of the BOX layer;

creating a via in the silicon device layer, the via extending to the BOX layer;

etching away a portion of the BOX layer starting at the via and extending laterally away from the via in a first direction to create a channel between the silicon device layer and silicon support layer;

applying an anisotropic etch via the channel to regions of the silicon device layer and silicon support layer adjacent to the channel;

the anisotropic etch following an orientation plane of the silicon device layer and silicon support layer to create a cavity underneath an overhanging portion of the silicon device layer;

the overhanging portion defining a planar underside surface for vertically coupling light into and out of the silicon device layer; and

applying a metal coating to the underside surface.

2. The method of claim 1, wherein the etchant used in the anisotropic etch is one of:

TMAH, KOH or CsOH.

3. The method of claim 1, wherein the step of applying the metal coating to the underside surface is carried out by atomic layer deposition (ALD).

4. The method of claim 1, wherein the silicon device layer is {100} oriented.

5. The method of claim 1, wherein the step of creating a via in the silicon device layer includes:

etching a via in the silicon device layer, the via extending from the upper surface of the silicon device layer down to the interface between the silicon device layer and the BOX layer, the via having a base and two sidewalls; and

applying a protective nitride layer to a region of the base.

6. The method of claim 5, wherein the step of etching away a portion of the BOX layer includes a step of first applying an additional protective patterning layer over the nitride layer.

7. A silicon photonic mirror comprising:

a silicon support layer;

a buried oxide (BOX) layer on top of the silicon support layer; and

a silicon device layer on top of the BOX layer;

a cavity extending through the silicon device layer, BOX layer and a region of the silicon support layer;

the walls of the cavity including a planar underside surface defined by an overhanging portion of the silicon device layer, the planar underside surface for vertically coupling light into and out of the silicon device layer; and

a metal surface applied to the planar underside surface.

8. The silicon photonic mirror of claim 7, wherein the planar underside surface forms an angle of 54.7 degrees relative to the top surface of the silicon device layer.

9. The silicon photonic mirror of claim 7, wherein the walls of the cavity include no more than one overhanging portion of the silicon device layer.

10. A method of fabricating a mirror, the method comprising:

providing a silicon-on-insulator substrate, the substrate comprising;

a silicon support layer;

a buried oxide (BOX) layer on top of the silicon support layer; and

a silicon device layer on top of the BOX layer;

creating a via in the silicon device layer, the via extending to the BOX layer;

etching away a portion of the BOX layer starting at the via and extending laterally away from the via in a first direction to create a channel between the silicon device layer and silicon support layer;

applying an anisotropic etch via the channel to regions of the silicon device layer and silicon support layer adjacent to the channel;

the anisotropic etch following an orientation plane of the silicon device layer and silicon support layer to create a cavity underneath an overhanging portion of the silicon device layer;

the overhanging portion defining a planar underside surface;

wherein the step of creating a via in the silicon device layer includes;

etching a via in the silicon device layer, the via extending from the upper surface of the silicon device layer down to the interface between the silicon device layer and the BOX layer, the via having a base and two sidewalls; and

applying a protective nitride layer to a region of the base before etching away the portion of the BOX layer.

11. A silicon photonic mirror comprising:

a silicon support layer;

a buried oxide (BOX) layer on top of the silicon support layer; and

a silicon device layer on top of the BOX layer;

a cavity extending through the silicon device layer, BOX layer and a region of the silicon support layer;

the walls of the cavity including no more than one planar underside surface defined by an overhanging portion of the silicon device layer, the planar underside surface for vertically coupling light into and out of the silicon device layer.

12. A method of fabricating a mirror, the method comprising:

providing a silicon-on-insulator substrate, the substrate comprising;

a silicon device layer on top of a BOX layer;

creating a V-groove in the silicon device layer, the V-groove extending to the BOX layer and having a first angled wall and a second angled wall;

providing a reflective coating to just one of the two angled walls of the V-groove to create a mirrored surface; and

growing silicon on top of the reflective surface to fill the V-groove, the interface between the grown silicon and the reflective surface forming the reflective surface of the mirror.

13. The method of claim 12, wherein the step of creating a V-groove includes:

an initial step of providing an opening in an oxide layer, the oxide layer located directly on top of the device layer; and

a subsequent step of applying an anisotropic etch to the silicon device layer via the opening.

14. The method of claim 12, wherein the reflective coating is an oxide layer.

15. The method of claim 12, wherein the reflective coating comprises a metal layer and an oxide layer;

the surface of the mirror being located at the interface.

16. The method of claim 12, wherein the silicon grown to fill the V-groove is epitaxial silicon.

17. The method of claim 12, wherein the silicon grown to fill the V-groove is poly-silicon or amorphous silicon.

18. The method of claim 12, further comprising the step of applying a nitride layer on top of the silicon that has been grown to fill the V-groove.

19. A silicon photonic mirror comprising

a silicon device layer on top of a BOX layer;

a V-groove within the silicon device layer, the V-groove extending to the BOX layer and having a first angled wall and a second angled wall;

a reflective coating on no more than one of the two angled walls of the V-groove; and

silicon on top of the reflective surface which fills the V-groove, the interface between the grown silicon and the reflective surface forming the reflective surface of the mirror.

20. The silicon photonic mirror of claim 19, wherein the reflective coating is an oxide layer.

21. The silicon photonic mirror of claim 19, wherein the reflective coating comprises a metal layer and an oxide layer;

the surface of the mirror being located at the interface.

22. The silicon photonic mirror of claim 19, wherein the silicon which fills the V-groove is epitaxial silicon.

23. The silicon photonic mirror of claim 19, wherein the silicon which fills the V-groove is epitaxial silicon, is poly-silicon or amorphous silicon.

24. The silicon photonic mirror of claim 19, further comprising a nitride layer on top of the silicon that has been grown to fill the V-groove.