Etching and thinning for the fabrication of lithographically patterned diamond nanostructures

Patent metadata

Field	Value
Publication number	US-2021399708-A1
Application number	US-202117466979-A
Country	US
Kind code	A1
Filing date	Sep 3, 2021
Priority date	Mar 6, 2019
Publication date	Dec 23, 2021
Grant date	—

Abstract

A back side of a diamond or other substrate is thinned using plasma etches and a mask situated away from the back side by a spacer having a thickness between 50 μm and 250 μm. Typically, a combined RIE/ICP etch is used to thin the substrate from 20-40 μm to less than 1 μm. For applications in which color centers are implanted or otherwise situated on a front side of the diamond substrate, after thinning, a soft graded etch is applied to reduce color center linewidth, particularly for nitrogen vacancy (NV) color centers.

First claim

We claim:

1 . A method of thinning a substrate, comprising:
situating a mask to be displaced from a back side of the substrate, the mask defining an aperture corresponding to an area of the back side of the substrate to be thinned; and exposing the back side of the substrate to the etch through the aperture defined in the mask.

2 . The method of claim 1 , wherein the etch is one or more of a reactive ion etch (RIE) and an inductively coupled plasma (ICP) etch.

3 . The method of claim 1 or claim 2 , wherein at least a portion of the etch includes a simultaneous RIE and ICP etch.

4 . The method of any of claims 1 - 3 , wherein the substrate is a diamond substrate, and further comprising:
defining a phononic crystal on a front side on the diamond substrate; and defining a plurality of surface mechanical resonators (SMRs) on the front side of the diamond substrate, the SMRs including one or more color centers.

5 . The method of any of claims 1 - 4 , wherein the color centers are nitrogen vacancy (NV) centers or silicon vacancy (SiV) centers, or a combination thereof.

6 . The method of any of claims 1 - 5 wherein the mask is displaced from the diamond substrate a distance of between 50 μm and 250 μm during back side etching.

7 . The method of any of claims 1 - 6 , further comprising situating a spacer between the mask and the back side of the substrate so that the mask is displaced from the back side of the diamond substrate.

8 . The method of any of claims 1 - 7 , wherein the spacer has a thickness of between 50 μm and 250 μm.

9 . The method of any of claims 1 - 8 , wherein the mask is defined in a sapphire substrate.

10 . A method, comprising:
thinning a back side of a substrate; and applying a graded soft etch to the thinned back side of the substrate.

11 . The method of claim 10 , wherein the substrate is a diamond substrate, and further comprising:
forming a plurality of nitrogen vacancy (NV) centers on the front side of the diamond substrate; and applying the graded, soft etch to the thinned back side of the diamond substrate to reduce a linewidth associated with the plurality of NV centers.

12 . The method of any of claims 10 - 11 , wherein the graded soft etch is a stepwise graded etch.

13 . The method of any of claims 10 - 12 , wherein the graded, soft etch includes at least an initial etch step having an etch rate of at least 5 nm/min.

14 . The method of any of claims 10 - 13 , wherein the graded, soft etch is a stepwise graded inductively coupled plasma (ICP) O 2 etch including at least an initial etch step at an initial ICP power level to produce an initial etch rate greater than 5 nm/min applied for an initial exposure time of at least 30 minutes and a final etch step at a final ICP power level that is less than ⅓ of the initial power level applied for a final exposure time of less than 15 minutes.

15 . The method of any of claims 10 - 14 , wherein the stepwise etch further comprises:
a first etch step applied after the initial etch step state, the first etch step associated with a first power level and a first etch rate of less than ¼ of the initial etch rate for a first exposure of less than ½ of the initial exposure time; and a second etch step applied after the first etch step state and prior to the final etch step, the second etch step associated with a second power level and a second etch rate that is less than the first etch rate for a second exposure time of less than ½ of the first exposure time.

16 . The method of any of claims 10 - 15 , wherein the graded, soft etch is a stepwise graded ICP O 2 etch that includes a series of etch steps associated with decreasing ICP powers.

17 . A device, comprising:
a diamond membrane of thickness that is less than 1 μm; a plurality nitrogen vacancy (NV) centers situated at a front side of the diamond membrane, wherein a linewidth of the NV centers is less than 330 MHz.

18 . The device of claim 17 , further comprising a phononic lattice situated on the front side of the diamond membrane and coupled to the NV centers.

19 . The device of claim 17 or claim 18 , where the thickness of the diamond membrane is less than 500 nm.

20 . The device of any of claims 17 - 19 , wherein the linewidth of the NV centers is less than 150 MHz.

21 . The method of any of claims 1 - 9 , further comprising applying a graded soft etch to the thinned back side of the substrate.

22 . The method of any of claims 1 - 9 and 21 , wherein the substrate is silicon, sapphire, quartz, GaAs, a III/V or II/VI semiconductor, glass, or fused silica.

Assignees

• Univ Oregon

Inventors

• Lekavicius Ignas
• Wang Hailin

Classifications

• H03H9/02055 Primary

  of the surface including the back surface · CPC title

• G03F7/2035

  simultaneous coating and exposure; using a belt mask, e.g. endless · CPC title

• G03F7/0042

  with inorganic or organometallic light-sensitive compounds not otherwise provided for, e.g. inorganic resists (G03F7/075 takes precedence) · CPC title

• C30B29/04 Primary

  Diamond · CPC title

• B82Y20/00

  Nanooptics, e.g. quantum optics or photonic crystals · CPC title