Atomic layer etching for smoothing of arbitrary surfaces

Patent metadata

Field	Value
Publication number	US-12217968-B2
Application number	US-202117224037-A
Country	US
Kind code	B2
Filing date	Apr 6, 2021
Priority date	Apr 6, 2020
Publication date	Feb 4, 2025
Grant date	Feb 4, 2025

Abstract

A method for etching a surface including obtaining a substrate comprising a material; reacting a surface of a substrate with a reactant, comprising a gas or a plasma, to form a reactive layer on the substrate, the reactive layer comprising a chemical compound including the reactant and the material; and wet etching or dissolving the reactive layer with a liquid wet etchant of solvent that selectively etches or dissolves the reactive layer but not the substrate.

First claim

What is claimed is:

1. An apparatus:
a reactor tool comprising a source of a reactant for reacting with a surface of a substrate so as to form a reactive layer on the substrate, wherein the reactant comprises is generated by a plasma, the substrate comprises a material comprising a semiconductor, a metal, or a dielectric, and the reactive layer comprises a chemical compound including the reactant and the material; and
an etching tool comprising a source of a liquid wet etchant for removing the chemical compound; and
a computer tool comprising a non-transitory computer readable medium storing a plurality of instructions, the plurality of instructions comprising:
outputting the reactant in the reactor tool,
transferring the substrate between the reactor tool and the etching tool, and
outputting the liquid wet etchant in the etching tool to remove the chemical compound at a higher rate than the material so as to smoothen the surface of the substrate and form the surface having a root mean square surface roughness of less than 1 nm.

2. The apparatus of claim 1 , wherein:
the reactive layer comprises at least one of:
protrusions having sidewalls and the removing comprising wet etching the protrusions laterally through the sidewalls so as to planarize the surface and remove or shrink the protrusions, the protrusions having a height or width in a range of 1-100 nm; or
valleys having sidewalls and the removing comprising wet etching the valleys laterally through the sidewalls so as to planarize the surface and remove or connect the valleys.

3. The apparatus of claim 1 , wherein the reactant comprises at least one of a halogen that halogenates the surface, a sulphide so as to form the reactive layer comprising a sulphide, hydrogen or a hydride so as to form the reactive layer comprising a hydride, or a nitride or nitrogen or nitrogen containing species so as to form the reactive layer comprising a nitride.

4. The apparatus of claim 1 , wherein the reactant forms the reactive layer comprising a salt.

5. The apparatus of claim 1 , further comprising a computer controlling output of the reactant and the wet etchant suitable for smoothing the material comprising a semiconductor comprising a III-V material or a metal comprising copper.

6. The apparatus of claim 1 , further comprising a computer controlling output of the reactant and the wet etchant so as to form the reactive layer forming a polycrystalline metal including grain boundaries so that the wet etching is isotropic so as to remove grain boundaries in both lateral and vertical directions.

7. The apparatus of claim 1 , further comprising
the: computer programmable to:
(a) instruct the output of the reactant so as to form the reactive layer; and
(b) instruct the output of the liquid wet etchant, wherein:

the step (a) forming the reactive layer further comprises at least one of:
a pre-cleaning step prior to forming the reactive layer, or
an activating step so as to make the reactive layer more amenable for the removing, and the computer is programmable to instruct repeating the step (a) prior to performing step (b).

8. The apparatus of claim 7 , wherein the computer is programmable to instruct that the step (b) is performed only once.

9. The apparatus of claim 1 , further comprising a tool configured to contact the liquid wet etchant with the reactive layer and so that the liquid wet etchant removes the reactive layer using a self-limiting process.

10. The apparatus of claim 9 , wherein the tool comprises a bath or tank comprising the liquid wet etchant or a spray system spraying the liquid wet etchant.

11. The apparatus of claim 9 , further comprising a tool configured to control contact of the liquid wet etchant on the reactive layer so as to controllably wet etch the reactive layer.

12. An apparatus, comprising:
a source of a reactant reacting with a surface of a substrate so as to form a reactive layer on the substrate, wherein the reactant is in gaseous form or is generated by a plasma, the substrate comprises a material, and the reactive layer comprises a chemical compound including the reactant and the material;
a source of a treatment that removes the chemical compound at a higher rate than the material; and
a computer programmable to:
(a) instruct output of the reactant so as to form the reactive layer;
(b) instruct performance of the treatment, and
(c) instruct a repeat of steps (a) and (b) so as to perform a first cycle and a second cycle each comprising the step (a) and the step (b), wherein:

the second cycle forms the reactive layer having a thickness that is thinner as compared to the reactive layer formed in the first cycle, so that the treatment in the second cycle removes the reactive layer with a finer resolution as compared to in the first cycle.

13. The apparatus of claim 12 , further comprising a conveyor conveying the substrate between a first region wherein the reactant reacts with the surface of the substrate, and a second region wherein the treatment removes the reactive layer.

14. The apparatus of claim 12 , further comprising: one or more reactor tools;
one or more etching tools;
a load lock chamber for loading the substrate comprising the material into the apparatus;
a transfer chamber for transferring the substrate between the load lock, the reactor tools, and the etching tools;
one or more arms positioned to transfer the substrate between the load lock, the reactor tools, and the etching tools; and
a computer programmable to:
(a) instruct the one or more arms to move the substrate to one of the reactor tools and controlling the one of the reactor tools so as to form the reactive layer; and′
(b) instruct the one or more arms to move the substrate to one of the etching tools and controlling the one of the etching tools so as to perform the treatment comprising a wet etch of the reactive layer.

15. The apparatus of claim 12 , wherein the reactant comprises at least one of a halogen that halogenates the surface, a sulphide so as to form the reactive layer comprising a sulphide, hydrogen or a hydride so as to form the reactive layer comprising a hydride, a nitride or nitrogen or nitrogen containing species so as to form the reactive layer comprising a nitride, or oxygen or an oxide so as to form the reactive layer comprising an oxide.

16. The apparatus of claim 12 , further comprising one or more chambers comprising first regions, wherein the chambers each comprise a vacuum or a pressure below atmospheric pressure during the reacting.

17. The apparatus of claim 12 , further comprising:
one or more reactor tools each comprising a first region, an outlet connected to a source of the reactant, the outlet for outputting the reactant towards the substrate in the first region, and electrodes and/or coils or wires electrically connected to a voltage supply for accelerating the reactant comprising charged particles towards the substrate; and
one or more etching tools each comprising a bath, tank, or spray system, wherein:
the treatment comprises a liquid wet etchant,
the spray system comprises a spray nozzle for spraying the reactive layer with the wet etchant, and
the spray system comprises or is coupled to a reservoir containing the wet etchant.

18. The apparatus of claim 12 , wherein the treatment smoothens the surface of the substrate and forms the surface having a root means squared (RMS) surface roughness of less than 1 nm for an optical, mechanical, or assembly application.

19. The apparatus of claim 12 , further performin

Assignees

• California Inst Of Techn

Inventors

• Greer Harold Frank

Classifications

• H10P95/064

  the removal being chemical etching · CPC title

• H10P95/04

  Planarisation of conductive or resistive materials · CPC title

• H10P72/0422

  for wet etching · CPC title

• H10P72/33

  into and out of processing chamber · CPC title

• H10P72/32

  between different workstations · CPC title