US 12,642,028 B2Granted

Methods for wet atomic layer etching of tungsten

AssigneeTokyo Electron Limited

InventorsTulashi Dahal, Kate Abel

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Abstract

Various embodiments of methods are provided for etching tungsten in a wet ALE process. The methods disclosed herein use a wide variety of techniques and wet etch chemistries to: (a) oxidize a tungsten surface and form a self-limiting, tungsten oxide passivation layer in a surface modification step of the wet ALE process, and (b) selectively remove the tungsten oxide passivation layer in a dissolution step of the wet ALE process. In the embodiments disclosed herein, ligand-assisted dissolution is used to selectively remove the tungsten oxide passivation layer without removing the unmodified tungsten surface underlying the tungsten oxide passivation layer. The ligand added to the dissolution solution prevents the dissolution solution from attacking and removing the unmodified tungsten surface.

Claims24

Dependent claims

A method of etching, the method comprising:

receiving a substrate having a tungsten (W) layer formed thereon, wherein a tungsten surface is exposed on a surface of the substrate;
exposing the surface of the substrate to a surface modification solution comprising an oxidizer dissolved in a non-aqueous solvent, wherein the oxidizer reacts with the tungsten surface to oxidize the tungsten surface and form a tungsten oxide passivation layer, which is self-limiting and insoluble in the non-aqueous solvent;
removing the surface modification solution from the surface of the substrate subsequent to forming the tungsten oxide passivation layer;
exposing the surface of the substrate to a dissolution solution comprising a ligand to selectively remove the tungsten oxide passivation layer, wherein the dissolution solution reacts with the tungsten oxide passivation layer to form soluble species, which are dissolved by the dissolution solution to expose an unmodified tungsten surface underlying the tungsten oxide passivation layer, wherein the ligand prevents the dissolution solution from attacking and removing the unmodified tungsten surface;
and
removing the dissolution solution and the soluble species from the surface of the substrate to etch the tungsten layer.

3 more elements

A method of etching a substrate using a wet atomic layer etching (ALE) process, the method comprising:

receiving the substrate, the substrate having a tungsten (W) layer formed thereon, wherein a tungsten surface is exposed on a surface of the substrate;
and
selectively etching the tungsten layer by performing multiple cycles of the wet ALE process, wherein each cycle comprises:
exposing the tungsten surface to a first etch solution comprising an oxidizer in a non-aqueous solvent to form a chemically modified W surface layer that is self-limiting and insoluble in the non-aqueous solvent;
rinsing the substrate with a first purge solution to remove the first etch solution from the surface of the substrate;
exposing the chemically modified W surface layer to a second etch solution to selectively dissolve the chemically modified W surface layer and expose an unmodified tungsten surface underlying the chemically modified W surface layer, wherein the second etch solution comprises a ligand that inhibits oxidation of the unmodified tungsten surface and prevents continuous etching of the tungsten layer;
and
rinsing the substrate with a second purge solution to remove the second etch solution from the surface of the substrate and etch the tungsten layer.

5 more elements

Dependencies are inferred from the claim text.