Atomic layer etching for smoothing of arbitrary surfaces

Patent metadata

Field	Value
Publication number	US-2021313185-A1
Application number	US-202117224037-A
Country	US
Kind code	A1
Filing date	Apr 6, 2021
Priority date	Apr 6, 2020
Publication date	Oct 7, 2021
Grant date	—

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 . A method for etching a surface, comprising:
(a) obtaining a substrate comprising a material; (b) 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 (c) wet etching the reactive layer with a liquid wet etchant that selectively etches the reactive layer but not the substrate.

2 . The method of claim 1 , wherein the reactive layer comprises protrusions having sidewalls and the wet etching etches the protrusions laterally through the sidewalls so as to planarize the surface and remove or shrink the protrusions.

3 . The method of claim 2 , wherein the protrusions have a height and width in a range of 1-100 nm.

4 . The method of claim 1 , wherein the reactive layer comprises valleys having sidewalls and the wet etching etches the valleys laterally through the sidewalls so as to planarize the surface and remove or connect the valleys.

5 . The method of claim 4 , wherein the valleys have a height and width in a range of 1-100 nm.

6 . The method 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, a nitride or nitrogen 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.

7 . The method of claim 1 , wherein the reactant forms the reactive layer comprising a salt.

8 . The method of claim 1 , wherein the reactant comprises an oxidizer that oxidizes the surface to form the reactive layer comprising an oxide.

9 . The method of claim 1 , wherein the reactant comprises an oxidizer that chlorinates the surface to form the reactive layer comprising a chloride.

10 . The method of claim 1 , wherein the reactant comprises an oxidizer that oxidizes the surface to form the reactive layer comprising a fluoride, bromide, nitride, or sulphide.

11 . The method of claim 1 , wherein the material comprises a semiconductor, a metal, or a dielectric.

12 . The method of claim 1 , wherein the material comprises silicon dioxide, copper, cobalt, tungsten, tin, silicon, a III-V material, or a II-VI material.

13 . The method of claim 1 , wherein the reacting comprises projecting the reactant onto the surface or exposing the surface to the reactant whose energy is below that required for physical sputtering of the surface using the reactant, so that the material is not ejected from the substrate.

14 . The method of claim 13 , further comprising performing the reacting for a duration and projecting the reactant at the surface with an energy so as to form the reactive layer having a thickness of 30 nm or less.

15 . The method of claim 1 , where an additional activation step is performed so as to make the reactive layer more amenable for removal in the subsequent wet etching step.

16 . The method of claim 1 , where the substrate temperature is at below a point where the reacted layer volatility is low

17 . The method of claim 16 where the reacted layer is involatile.

18 . The method of claim 1 , further comprising repeating steps (b) and (c) so as to perform a plurality of etching cycles each comprising the step (b) and the step (c), wherein:
the cycles include a first cycle and a second cycle subsequent to the first cycle, the second cycle forms the reactive layer that is thinner as compared to the reactive layer formed in the first cycle, so that the wet etching in the second cycle etches the reactive layer with a finer resolution as compared to the wet etching in the first cycle.

19 . The method of claim 18 , wherein the plurality of etching cycles form the substrate having an atomic scale surface roughness and/or wherein the plurality of etching cycles form the substrate having a root means squared (RMS) surface roughness of less than 1 nm.

20 . The method of claim 1 , wherein the reacting is under conditions such that the reactive layer is involatile or has low volatility so as to prevent evaporation of the reactive layer, and/or wherein the reacting is at a pressure of 10 Torr or less and the wet etching is at a pressure in a range of 500-1000 Torr.

21 . The method of claim 1 , wherein the wet etching dissolves or etches the entire reactive layer and the method further comprises performing a thermal treatment of the wet etched substrate and or the reactive layer.

22 . An apparatus for etching a substrate, comprising:
one or more reactor tools reacting a reactant with a surface of a substrate so as to form a reactive layer on the substrate, wherein the reactant comprises a gas or plasma, the substrate comprises a material, and the reactive layer comprises a chemical compound including the reactant and the material; and one or more etching tools selectively etching the reactive layer using a liquid wet etchant.

23 . The apparatus of claim 22 , further comprising a conveyor conveying the substrate between the reactor tools and the etching tools, wherein the etching tools and/or the reactor tools operate at or near atmospheric pressure.

24 . The apparatus of claim 22 , further comprising:
a load lock chamber for loading the substrate comprising a 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: (a) instructing the one or more arms to move the substrate to one of the reactor tools and controlling the reactor so as to form the reactive layer; and′ (b) instructing the one or more arms to move the substrate to one of the etching tools and controlling the one or the etching tools so as to wet etch the reactive layer, wherein the computer: instructs a repeat of steps (a) and (b) so as to perform a plurality of etching cycles each comprising the step (a) and the step (b), wherein: the cycles include a first cycle and a second cycle subsequent to the first cycle, the second cycle forms the reactive layer that is thinner as compared to the reactive layer formed in the first cycle, so that the wet etching in the second cycle etches the reactive layer with a finer resolution as compared to the wet etching in the first cycle.

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