# US 11,307,357 B2 · Overcoating slanted surface-relief structures using atomic layer deposition

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- Number: US 11,307,357 B2
- Document ID: US11307357B2
- Status: Granted
- Kind: B2
- Application number: 16/660,463
- Filed: 2019-10-22
- Published: 2020-07-02
- Granted: 2022-04-19
- Earliest claimed: 2018-12-28
- Assignees: Facebook Technologies, LLC
- Applicants: Facebook Technologies, LLC
- Inventors: Nihar Ranjan Mohanty
- Web page: https://patentgrep.com/patent/US11307357B2

## CPC

- G02B 6/34: utilising prism or grating {(G02B6/293 takes precedence)}
- B29D 11/00663: {Production of light guides}
- B29D 11/00769: {Producing diffraction gratings}
- B29D 11/00865: {Applying coatings; tinting; colouring (printing, marking or copying processes B41M; identification in general G09F3/00; producing decorative effects in general B44C; positioning or marking of lenses B24B13/0055)}
- C23C 16/045: {Coating cavities or hollow spaces, e.g. interior of tubes; Infiltration of porous substrates}
- C23C 16/22: characterised by the deposition of inorganic material, other than metallic material
- C23C 16/45525: {Atomic layer deposition [ALD]}
- C23C 16/56: After-treatment
- G02B 5/1847: {Manufacturing methods}
- G02B 27/0081: {with means for altering, e.g. enlarging, the entrance or exit pupil}
- G02B 27/0172: {characterised by optical features}
- G02B 6/0011: {the light guides being planar or of plate-like form}
- G02B 2027/0112: {comprising device for genereting colour display}
- G02B 2027/0174: {holographic}
- G02B 2027/0178: {Eyeglass type (eyeglass details G02C)}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- B29D: PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE (making granules B29B9/00; making preforms B29B11/00)
- C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04)

## Abstract

Techniques for overcoating slanted structures and devices obtained using the techniques are disclosed. In some embodiments, a method of forming an overcoat layer on a surface-relief structure on a substrate includes receiving the substrate with the surface-relief structure. The surface-relief structure includes a plurality of ridges slanted with respect to the substrate, and a plurality of grooves each between two adjacent ridges. The method further includes depositing, in each cycle of a plurality of cycles, a uniform layer of an overcoat material on surfaces of the plurality of ridges and bottoms of the plurality of grooves. The deposited layers of the overcoat material and the plurality of ridges collectively form a light-coupling structure on the substrate. A surface of the overcoat layer is planar.

## Claims

### Claim 1

A method of forming an overcoat layer on a surface-relief structure on a substrate, the method comprising:
receiving the substrate with the surface-relief structure, wherein the surface-relief structure comprises:
a plurality of ridges slanted with respect to the substrate; and
a plurality of grooves each between two adjacent ridges; and
in each cycle of a plurality of cycles,
depositing a uniform layer of an overcoat material on surfaces of the plurality of ridges and bottoms of the plurality of grooves,
etching the uniform layer of the overcoat material deposited on top surfaces of the plurality of ridges at a first removal rate to remove at least a portion of the uniform layer of the overcoat material deposited on the top surfaces of the plurality of ridges; and
etching the uniform layer of the overcoat material deposited on the bottoms of the plurality of grooves at a second removal rate that is lower than the first removal rate to keep at least a portion of the uniform layer of the overcoat material deposited on the bottoms of the plurality of grooves,
wherein layers of the overcoat material deposited in the plurality of cycles fill the plurality of grooves and, together with the plurality of ridges, form a slanted grating on the substrate, the slanted grating configured to couple light into or out of the substrate.

### Claim 2 (depends on 1)

The method of claim 1, wherein the uniform layer of the overcoat material deposited in each cycle comprises one atomic layer of the overcoat material.

### Claim 3 (depends on 1)

The method of claim 1, wherein a top surface of the overcoat layer is planar.

### Claim 4 (depends on 1)

The method of claim 1, wherein a top surface of the overcoat layer comprises a plurality of planar surface portions and a plurality of concave surface portions forming a plurality of dips having a depth lower than a depth of the plurality of grooves.

### Claim 5 (depends on 4)

The method of claim 4, wherein the plurality of dips is aligned with the plurality of grooves.

### Claim 6 (depends on 4)

The method of claim 4, wherein a ratio of a depth of the overcoat layer from top surfaces of the plurality of ridges to the top surface of the overcoat layer to the depth of the plurality of dips ranges between 40:1 and 2:1.

### Claim 7 (depends on 1)

The method of claim 1, wherein a ratio of a depth of the overcoat layer from top surfaces of the plurality of ridges to a top surface of the overcoat layer to a depth of the plurality of grooves ranges between 1:2 and 1:100.

### Claim 8 (depends on 1)

The method of claim 1, wherein the surface-relief structure is characterized by a period varying across the substrate or a duty cycle varying across the substrate.

### Claim 9 (depends on 1)

The method of claim 1, wherein the plurality of ridges each have a slant angle that is at least 45°.

### Claim 10 (depends on 1)

The method of claim 1, wherein the plurality of grooves each have a depth that is at least 100 nm.

### Claim 11 (depends on 1)

The method of claim 1, wherein the uniform layer of the overcoat material deposited in each cycle comprises two or more atomic layers of the overcoat material.

### Claim 12 (depends on 1)

The method of claim 1, wherein the at least a portion of the uniform layer of the overcoat material removed from the top surfaces of the plurality of ridges comprise all of the overcoat material deposited on the top surfaces of the plurality of ridges.

### Claim 13 (depends on 1)

The method of claim 1, wherein a refractive index of the overcoat material is different from a refractive index of the plurality of ridges.

### Claim 14 (depends on 1)

The method of claim 1, wherein the overcoat material comprises at least one of hafnium oxide, titanium oxide, tantalum oxide, tungsten oxide, zirconium oxide, gallium sulfide, gallium nitride, gallium phosphide, silicon, silicon nitride, silicon oxide, alumina, porous silica, a polymer with a refractive index higher than the substrate, or a fluorinated monomer or polymer having a refractive index lower than the substrate.

### Claim 15 (depends on 1)

The method of claim 1, wherein the plurality of ridges comprise at least one of amorphous silicon, silicon oxide, silicon nitride, silicon carbide, silicon oxynitride (SiOxNy), spin on carbon (SOC), amorphous carbon, diamond like carbon (DLC), titanium oxide, aluminum oxide, tantalum oxide, or hafnium oxide.

### Claim 16 (depends on 1)

The method of claim 1, wherein the substrate comprises a waveguide.