H2-assisted slanted etching of high refractive index material

• US 10,502,958 B2
• Filed: 10/30/2018
• Issued: 12/10/2019
• Est. Priority Date: 10/30/2017
• Status: Active Grant

• Current Assignee: META Platforms Technologies LLC (Meta Platforms, Inc. (f/k/a Facebook, Inc.))
• Original Assignee: Facebook Technologies, LLC (Meta Platforms, Inc. (f/k/a Facebook, Inc.))
• Inventors: Mohanty, Nihar Ranjan
• Primary Examiner(s): Ferguson, Dion
• Assistant Examiner(s): Sathiraju, Srinivas
• Application Number:
  US16/174,305
• Publication Number:
  US 20190129180A1
• Time in Patent Office: 406 Days
• Field of Search: None
• CPC Class Codes: G02B 2027/0109 comprising details concerning the making of holograms
• CPC Class Codes: G02B 2027/0178 Eyeglass type eyeglass details G02C
• CPC Class Codes: G02B 27/0172 characterised by optical features
• CPC Class Codes: G02B 6/122 Basic optical elements, e.g. light-guiding paths
• CPC Class Codes: G02B 6/34 utilising prism or grating G02B6/293 takes precedence
• CPC Class Codes: H01J 27/022 Details
• CPC Class Codes: H05H 1/16 using externally-applied electric and magnetic fields
• CPC Class Codes: H05H 1/4652 using inductive coupling means, e.g. coils

Abstract

Techniques for fabricating a slanted structure are disclosed. In one embodiment, a method of fabricating a slanted structure in a material layer includes injecting a first reactive gas into an reactive ion source generator, generating a plasma that includes reactive ions in the reactive ion source generator, extracting at least some of the reactive ions from the plasma to form a collimated reactive ion beam towards the material layer, and injecting a second reactive gas onto the material layer. The collimated reactive ion beam and the second reactive gas etch the material layer both physically and chemically to form the slanted surface-relief structure. In some embodiments, the first reactive gas includes a low-molecular-weight gas (e.g., H₂ or He). In some embodiments, a surface layer of the internal cavity of the reactive ion source generator includes a layer of an oxide material (e.g., aluminum oxide or Y₂O₃).

Claims

1. A method of fabricating a slanted surface-relief structure in a material layer, the method comprising:

injecting a first reactive gas into an reactive ion source generator, wherein the first reactive gas comprises a low-molecular-weight gas;

generating a plasma in the reactive ion source generator, the plasma including reactive ions;

extracting at least some of the reactive ions from the plasma to form a collimated reactive ion beam towards the material layer; and

injecting a second reactive gas onto the material layer,

wherein the collimated reactive ion beam and the second reactive gas etch the material layer both physically and chemically to form the slanted surface-relief structure.

2. The method of claim 1, further comprising:

rotating the material layer based on a desired slant angle of the slanted surface-relief structure.

3. The method of claim 1, wherein the first reactive gas comprises at least one of CF₄, CHF₃, CH₂F₂, CH₃F, C₄F₈, C₄F₆, C₂F₆, C₂F₈, NF₃, CLF₃, N₂O, N₂, O₂, SF₆, C₁₂, BCl₃, HBr, Hz, Ar, He, or Ne.

4. The method of claim 1, wherein the material layer includes a semiconductor substrate, a SiO₂ layer, a Si₃N₄ material layer, a titanium oxide layer, an alumina layer, a SiC layer, a SiO_xN_y layer, an amorphous silicon layer, a spin on carbon (SOC) layer, an amorphous carbon layer (ACL), a diamond like carbon (DLC) layer, a TiO_x layer, an AlO_x layer, a TaO_x layer, or a HFO_x layer.

5. The method of claim 1, wherein extracting at least some of the reactive ions from the plasma to form the collimated reactive ion beam comprises:

applying an extraction voltage on an extraction grid adjacent to the reactive ion source generator; and

applying an acceleration voltage on an acceleration grid to extract and accelerate at least some of the reactive ions,

wherein the extraction grid and the acceleration grid are aligned; and

wherein the acceleration voltage is lower than the extraction voltage.

6. The method of claim 1, wherein the second reactive gas comprises at least one of CF₄, CHF₃, N₂, O₂, SF₆, Cl₂, BCl₃, or HBr.

7. The method of claim 1, wherein:

the slanted surface-relief structure comprises a slanted surface-relief optical grating.

8. The method of claim 7, wherein:

the slanted surface-relief optical grating comprises a plurality of ridges; and

a leading edge of each ridge is parallel to a trailing edge of the ridge.

9. The method of claim 8, wherein:

a slant angle of the leading edge and a slant angle of the trailing edge are greater than 30 degrees with respect to a surface normal of the material layer.

10. The method of claim 8, wherein a difference between a length of the leading edge and a length of the trailing edge is less than 10% of the length of the trailing edge.

11. The method of claim 7, wherein:

a depth of the slanted surface-relief optical grating is greater than 100 nm.

12. The method of claim 7, wherein:

a duty cycle of the slanted surface-relief optical grating is greater than 60%.

13. The method of claim 1, wherein:

the first reactive gas comprises H₂;

the reactive ions include H⁺ ions;

the material layer includes a SiO_mN_n layer or a Si₃N₄ layer; and

the H⁺ ions react with the SiO_mN_n layer or the Si₃N₄ layer to form a SiH_xN_y layer.

14. The method of claim 13, wherein the collimated reactive ion beam and the second reactive gas react with the SiH_xN_y layer to generate SiF₄, NH₃, and HCN gases.

15. A chemically assisted reactive ion beam etching (CARIBE) system for fabricating a slanted surface-relief structure in a material layer, the CARIBE system comprising:

an reactive ion source generator configured to generate a plasma using a first reactive gas, the plasma including reactive ions, and the first reactive gas including a low-molecular-weight gas;

one or more aligned collimator grids configured to extract and accelerate at least some of the reactive ions in the plasma to form a collimated reactive ion beam towards the material layer; and

a gas ring configured to inject a second reactive gas onto the material layer,

wherein the collimated reactive ion beam and the second reactive gas etch the material layer both physically and chemically to form the slanted surface-relief structure in the material layer.

16. The CARIBE system of claim 15, wherein:

the reactive ion source generator includes an internal cavity configured to enclose the plasma; and

a surface layer of the internal cavity includes an oxide material.

17. The CARIBE system of claim 16, wherein the oxide material includes Y₂O₃ or aluminum oxide.

18. The CARIBE system of claim 15, further comprising:

a neutralizer configured to inject an electron beam into the collimated reactive ion beam to neutralize the collimated reactive ion beam.

19. The CARIBE system of claim 15, wherein:

the reactive ion source generator comprises an inductively coupled plasma generator.

20. The CARIBE system of claim 15, wherein:

the first reactive gas comprises at least one of CF₄, CHF₃, CH₂F₂, CH₃F, C₄F₈, C₄F₆, C₂F₆, C₂F₈, NF₃, CLF₃, N₂O, N₂, O₂, SF₆, H₂, Cl₂, BCl₃, HBr, Ar, He, or Ne; and

the second reactive gas comprises at least one of CF₄, CHF₃, N₂, O₂, SF₆, Cl₂, BCl₃, or HBr.