Extreme ultraviolet (EUV) lithography patterning methods utilizing EUV resist hardening

A device, comprising:

• a multi-layer lithographic stack disposed on a substrate, wherein the multi-layer lithographic stack comprises an extreme ultraviolet (EUV) resist mask, and wherein the EUV resist mask comprises patterned openings which expose portions of an upper surface of an underlying layer of the multi-layer lithographic stack;
• an etch-resistant layer embedded in upper horizontal surfaces of the EUV resist mask, wherein the etch-resistant layer is formed by a controlled surface treatment that is configured to implant a species into upper horizontal surfaces of the EUV resist mask and not on vertical sidewall surfaces of the patterned openings of the EUV mask, and thereby form the etch-resistant layer that is embedded in only the upper horizontal surfaces of the EUV resist mask, wherein the etch-resistant layer comprises a first thickness;
• and
• a hardened layer embedded in the exposed portions of the upper surface of the underlying layer of the multi-layer lithographic stack, wherein the hardened layer is formed as a result of implanting the species into the exposed portions of the upper surface of the underlying layer of the multi-layer lithographic stack, wherein the hardened layer has a second thickness which is less than the first thickness;
• wherein a difference in the thicknesses of the etch-resistant layer and the hardened layer is configured to enable patterning of the underlying layer of the multi-layer lithographic stack using the surface-hardened EUV resist mask and using an anisotropic dry etch process to punch-through the hardened layer in the exposed portions of the upper surface of the underlying layer of the multi-layer lithographic stack and etch away remaining exposed portions of the underlying layer of the multi-layer lithographic stack without completely removing the etch-resistant layer in the upper horizontal surfaces of the EUV resist mask.