Fabrication of metallic optical metasurfaces

Patent metadata

Field	Value
Publication number	US-10968522-B2
Application number	US-201815943350-A
Country	US
Kind code	B2
Filing date	Apr 2, 2018
Priority date	Apr 2, 2018
Publication date	Apr 6, 2021
Grant date	Apr 6, 2021

Abstract

The disclosure provides a method for fabricating a metallic optical metasurface having an array of hologram elements. The method includes forming a first copper layer protected with a conducting or dielectric barrier layer over a backplane structure by a damascene process. The first copper layer comprises a plurality of nano-gaps vertically extending from the backplane structure. The plurality of nano-gaps is filled with a dielectric material. The method also includes removing the dielectric material and a portion of the conducting or dielectric barrier layer to expose the portions in the nano-gaps of the first copper layer. The method may further include depositing a dielectric coating layer over the top portion and exposed side portions of the first copper layer to form a protected first copper layer, and filling the gaps with an electrically-tunable dielectric material that has an electrically-tunable refractive index.

First claim

What is claimed is:

1. A method for fabricating a metallic optical metasurface having an array of hologram elements, comprising:
forming a first copper layer with a conducting or dielectric barrier layer over a backplane structure by a damascene process, wherein the first copper layer comprises a plurality of nano-gaps vertically extending from the backplane structure, wherein the plurality of nano-gaps is filled with a dielectric material, wherein the conducting or dielectric barrier layer is between the first copper layer and the backplane structure, and also between the first copper layer and the dielectric material;
removing the dielectric material and a portion of the conducting or dielectric barrier layer to form exposed side portions in the nano-gaps of the first copper layer;
depositing a dielectric coating layer over the top portion and the exposed side portions in the nano-gaps of the first copper layer to form protected nano-gaps of first copper layer; and
filling the protected nano-gaps with an electrically-tunable dielectric material that has an electrically-tunable refractive index.

2. The method of claim 1 , wherein the dielectric barrier layer or the dielectric coating layer comprises a material selected from a group consisting of SiN, SiC, SiCN, Al 2 O 3 , HfO 2 , SiO 2 , and optically transparent materials that are barriers to copper diffusion.

3. The method of claim 1 , wherein the conducting barrier layer comprises one or more of tantalum, tantalum nitride, and a combination.

4. The method of claim 1 , wherein the first copper layer comprises a plurality of copper pillars vertically extending from the backplane structure.

5. The method of claim 4 , the step of removing the dielectric material further comprising:
etching the dielectric material to form the nano-gaps between adjacent copper pillars by a chemical etchant at a first etching rate; and
etching by the chemical etchant at a second etching rate to remove the portion of the conducting or dielectric barrier layer in the nano-gaps and the top portion of the first copper layer.

6. The method of claim 5 , wherein the chemical etchant is a buffered oxide etchant.

7. The method of claim 1 , wherein the electronically-tunable dielectric material is one of a liquid crystal material, electro-optic (EO) polymer material, or chalcogenide Glasses.

8. The method of claim 1 , further comprising encapsulating the tunable dielectric material with an optically transparent material.

9. The method of claim 8 , wherein the optically transparent material comprises a glass or a polymer.

10. The method of claim 1 , further comprising removing the electrically-tunable dielectric material to expose the top portion of the protected first copper layer; and encapsulating the electrically-tunable dielectric material and the top portion of the protected first copper layer with an optically transparent material.

11. The method of claim 10 , wherein the optically transparent material comprises a glass or a polymer.

12. The method of claim 1 , further comprising forming the backplane structure over a substrate.

13. The method of claim 1 , wherein the backplane structure comprises a dielectric spacer between the first copper layer and a second copper layer.

14. The method of claim 13 , wherein the dielectric spacer comprises at least one thin chemically resistant layer and at least a thick low-k dielectric layer between the first copper layer and the second copper layer.

15. The method of claim 1 , wherein the backplane structure is selected from a group consisting of a full backplane structure, a partial backplane structure, a notch backplane structure, and a Bragg reflector backplane structure.

16. The method of claim 15 , wherein the partial backplane structure comprises a dielectric spacer between the first copper layer and a second copper layer having copper patches under each pair of adjacent copper pillars.

17. The method of claim 16 , wherein the copper patches have a width equal to a pitch of a metallic hologram element in the full backplane structure.

18. The method of claim 15 , wherein the notch backplane structure comprises a dielectric spacer having a notch between the first copper layer and a second copper layer, wherein the notch is under the gap between adjacent copper pillars.

19. The method of claim 15 , wherein the Bragg reflector backplane structure comprises a plurality of dielectric layers having alternating first and second dielectric indexes.

20. The method of claim 1 , wherein the dielectric material is selected from a group consisting of SiN, SiCN, SiC, Al 2 O 3 , HfO 2 , and SiO 2 .

21. A method for fabricating an optical metasurface, comprising:
forming a plurality of copper pillars with a conducting barrier layer over a backplane structure by a damascene process, wherein a plurality of nano-gaps between the plurality of copper pillars is filled with a dielectric material, wherein the conducting barrier layer is between the plurality of copper pillars and the backplane structure, and also between the plurality of copper pillars and the dielectric material, wherein the backplane structure comprises a stack of dielectric layers;
removing the dielectric material in the nano-gaps, at least the top layer of the stack of the dielectric layers, and the conducting barrier layer to expose side portions in the nano-gaps and a bottom portion underneath the plurality of copper pillars;
depositing a dielectric coating layer over the top portion, the exposed side portions in the nano-gaps between the plurality of copper pillars, and the bottom portion to form protected copper pillars; and
filling the nano-gaps and the space underneath the protected copper pillars with an electrically-tunable dielectric material that has an electrically-tunable refractive index.

22. The method of claim 21 , wherein the dielectric coating layer comprises a material selected from a group consisting of SiN, SiC, SiCN, Al 2 O 3 , HfO 2 , SiO 2 , and optically transparent materials that are barriers to copper diffusion.

23. The method of claim 22 , wherein the conducting barrier layer comprises Ta and/or TaN.

Assignees

• Akselrod Gleb M
• Josberger Erik Edward
• Weidman Mark C
• Elwha Llc

Inventors

• Akselrod Gleb M
• Josberger Erik Edward
• Weidman Mark C

Classifications

• G02F2202/36

  Micro- or nanomaterials · CPC title

• B82Y40/00

  Manufacture or treatment of nanostructures · CPC title

• G02B1/002

  made of materials engineered to provide properties not available in nature, e.g. metamaterials · CPC title

• G02B5/203

  having holographic or diffractive elements (diffraction gratings per se G02B5/18; holographic elements per se G02B5/32; generating the spectrum using diffraction elements G01J3/18) · CPC title

• G03H2225/32

  Phase only · CPC title