US Patent 11994800 Dose reduction of patterned metal oxide photoresists

Embodiments of the present disclosure generally relate to a multilayer stack used as a mask in extreme ultraviolet (EUV) lithography and methods for forming a multilayer stack. In one embodiment, the method includes forming a carbon layer over a film stack, forming a metal rich oxide layer on the carbon layer by a physical vapor deposition (PVD) process, forming a metal oxide photoresist layer on the metal rich oxide layer, and patterning the metal oxide photoresist layer. The metal oxide photoresist layer is different from the metal rich oxide layer and is formed by a process different from the PVD process. The metal rich oxide layer formed by the PVD process improves adhesion of the metal oxide photoresist layer and increases the secondary electrons during EUV lithography, which leads to decreased EUV dose energies.