Fabrication of diffraction gratings

Patent metadata

Field	Value
Publication number	US-11733533-B2
Application number	US-202217745457-A
Country	US
Kind code	B2
Filing date	May 16, 2022
Priority date	Jun 28, 2018
Publication date	Aug 22, 2023
Grant date	Aug 22, 2023

Abstract

The systems and methods discussed herein are for the fabrication of diffraction gratings, such as those gratings used in waveguide combiners. The waveguide combiners discussed herein are fabricated using nanoimprint lithography (NIL) of high-index and low-index materials in combination with and directional etching high-index and low-index materials. The waveguide combiners can be additionally or alternatively formed by the directional etching of transparent substrates. The waveguide combiners that include diffraction gratings discussed herein can be formed directly on permanent transparent substrates. In other examples, the diffraction gratings can be formed on temporary substrates and transferred to a permanent, transparent substrate.

First claim

What is claimed is:

1. A method of patterning a substrate, comprising:
forming a hardmask layer on a first side of a substrate, wherein the substrate is formed from a transparent material and is defined by a normal plane along a width of the substrate;
forming, on the hardmask layer, a patterned layer;
etching the patterned layer and the hardmask layer to expose the first side of the substrate;
removing the patterned layer;
etching the first side of the substrate to form a first plurality of angled mesas in the first side of the substrate, wherein each angled mesa of the first plurality of angled mesas is etched at an angle from 20 degrees to 70 degrees relative to the normal plane;
subsequently, removing the hardmask layer; and
forming a second plurality of angled mesas on a second side of the substrate, the second plurality of angled mesas being at a different angle than the first plurality of angled mesas.

2. The method of claim 1 , wherein forming the hardmask layer on the first side of the substrate comprises using chemical vapor deposition (CVD), physical vapor deposition (PVD), or atomic layer deposition (ALD).

3. The method of claim 1 , wherein the transparent material comprises a glass or a polymer.

4. The method of claim 1 , wherein forming the patterned layer comprises using nanoimprint.

5. The method of claim 1 , wherein nanoimprint lithography is used in the forming of the second plurality of angled mesas on the second side of the substrate.

6. A method of forming a diffraction grating, comprising:
forming a first hardmask layer on a target stack, wherein the target stack is formed on a first side of a first substrate;
etching a plurality of openings in the first hardmask layer;
etching the target stack to form a first plurality of angled mesas in the target stack on the first side of the first substrate, wherein each angled mesa of the first plurality of angled mesas is etched at a first angle from 20 degrees to 70 degrees relative to a normal plane;
removing the first substrate from the etched target stack;
attaching the etched target stack to a first side of a second substrate;
forming a second hardmask layer on a second side of a second substrate, wherein the second substrate comprises a transparent material and is defined by a normal plane along a width of the second substrate;
forming a patterned layer on the second hardmask layer;
etching the patterned layer and the second hardmask layer to expose the second side of the second substrate;
removing the patterned layer;
etching the second side of the second substrate; and
forming, in response to the etching, a second plurality of angled mesas in the second side of the second substrate, wherein each angled mesa of the second plurality of angled mesas is etched at a second angle from 20 degrees to 70 degrees relative to the normal plane.

7. The method of claim 6 , wherein forming the first hardmask layer comprises using nanoimprint lithography (NIL) to deposit the first hardmask layer as a pattern, wherein the pattern comprises a third plurality of mesas and a plurality of angled troughs in between adjacent mesas of the third plurality of mesas.

8. The method of claim 6 , wherein forming the patterned layer comprises using nanoimprint lithography.

9. The method of claim 6 , wherein the second substrate is a transparent substrate.

10. The method of claim 6 , wherein the target stack is bonded to the first substrate via a de-bonding layer, wherein removing the first substrate comprises detaching the first substrate from the target stack via the de-bonding layer.

11. The method of claim 10 , wherein forming the patterned layer comprises using nanoimprint lithograph.

12. The method of claim 6 , further comprising etching each of the target stack and the second side of the second substrate using directional etching.

13. The method of claim 12 , wherein directional etching comprises:
positioning a first portion of the target stack in a path of an ion beam, the ion beam being at the first angle relative to the normal plane of the first substrate, wherein etching the first portion of the target stack comprises exposing the first portion of the target stack to the ion beam to form the first plurality of angled mesas at the first angle; and
rotating the first substrate about a central axis perpendicular to the normal plane to a predetermined rotation angle.

14. The method of claim 13 , further comprising positioning a second portion of the target stack in the path of the ion beam after rotating the first substrate to the predetermined rotation angle; and
etching the second portion of the target stack to form a third plurality of mesas by exposing the second portion of the target stack to the ion beam.

15. A method of forming diffraction gratings, comprising:
forming a hardmask layer on a target stack, wherein the target stack is formed on a first side of a first substrate;
etching a plurality of openings in the hardmask layer;
etching the target stack to form a first plurality of angled mesas in the target stack on the first side of the first substrate, wherein each angled mesa of the plurality of angled mesas is etched at an angle 20 degrees to 70 degrees relative to a normal plane;
forming a hardmask layer on a second side of the first substrate, wherein the first substrate is defined by a normal plane along a width of the first substrate;
forming a patterned layer on the hardmask layer;
etching the patterned layer and the hardmask layer to expose the second side of the first substrate;
removing the patterned layer; and
etching the second side of the first substrate.

16. The method of claim 15 , wherein forming the patterned layer comprises using nanoimprint lithography.

17. The method of claim 15 , further comprising: forming, in response to the etching, a plurality of angled mesas in the second side of the first substrate.

18. The method of claim 17 , wherein each angled mesa of the plurality of angled mesas is etched at an angle from 20 degrees to 70 degrees relative to the normal plane.

19. The method of claim 18 , wherein forming the hardmask layer on the first substrate comprises using chemical vapor deposition (CVD), physical vapor deposition (PVD), or atomic layer deposition (ALD).

20. The method of claim 15 , wherein the first substrate is optically transparent and comprises a glass or a polymer.

Assignees

• Applied Materials Inc

Inventors

• Godet Ludovic
• Mcmillan Wayne
• Meyer Timmerman Thijssen Rutger

Classifications

• G03F7/0002 Primary

  Lithographic processes using patterning methods other than those involving the exposure to radiation, e.g. by stamping · CPC title

• G02B6/136

  by etching · CPC title

• G02B5/1857 Primary

  using exposure or etching means, e.g. holography, photolithography, exposure to electron or ion beams · CPC title

• G02B6/124

  Geodesic lenses or integrated gratings · CPC title

• G02B27/0944 Primary

  Diffractive optical elements, e.g. gratings, holograms (gratings per se G02B5/18; holograms used as optical elements per se G02B5/32) · CPC title