Extreme ultraviolet (EUV) lithography using an intervening layer or a multi-layer stack with varying mean free paths for secondary electron generation

A method for patterning a substrate, comprising:

• depositing a first layer on a substrate, the first layer comprising Si or SiON and having a first thickness of 3 nm or 6 nm, wherein the first layer includes a first mean free path for secondary electrons;
• depositing a second layer on the first layer, the second layer comprising Sn or SnO2 and having a second thickness, wherein the second thickness is 2 nm or 4 nm when the first thickness is 3 nm or 6 nm, respectively, and wherein the second layer includes a second mean free path for secondary electrons that is lower than the first mean free path;
• and
• depositing a photoresist layer on the second layer, the photoresist layer comprising chemically amplified organic photoresist material, wherein the first and second mean free paths converge in the photoresist layer.