Reduction of EUV resist damage by neutral beam etching

Area of Science:

• Materials Science
• Semiconductor Manufacturing
• Nanotechnology

Background:

• Extreme ultraviolet (EUV) lithography enables finer patterns than ArF immersion lithography due to its shorter wavelength (13.5 nm vs. 193 nm).
• Thin EUV resists are vulnerable to radiation damage during etching, leading to low etch resistance and poor selectivity.
• Hardmask materials like Si3N4 and SiO2 require precise etching for advanced semiconductor fabrication.

Purpose of the Study:

• To compare the radiation damage to EUV resist during hardmask etching using neutral beam etching (NBE) versus ion beam etching (IBE).
• To evaluate the etch selectivity of NBE and IBE for EUV resist and hardmask materials.
• To identify the optimal etching method for preserving EUV resist integrity and improving process efficiency.

Main Methods:

• Etching of hardmask materials (Si3N4, SiO2) using CF4 gas with both NBE and IBE techniques.
• Analysis of radiation damage to a 20 nm thick EUV resist, focusing on line edge roughness (LER) and critical dimension (CD) change.
• Measurement of root mean square (RMS) surface roughness of the etched EUV resist.
• Comparison of etching selectivity between hardmask materials and EUV resist for both NBE and IBE.

Main Results:

• NBE significantly reduced LER increase (by ~1/3) and CD change (by ~1/2) in EUV resist compared to IBE.
• The RMS surface roughness of EUV resist etched by NBE was approximately 2/3 of that etched by IBE.
• NBE demonstrated higher etching selectivity for hardmask materials (SiO2, Si3N4) over EUV resist compared to IBE.

Conclusions:

• NBE offers superior performance in minimizing radiation damage to thin EUV resists during hardmask etching.
• The enhanced etch selectivity with NBE is attributed to the absence of potential energy release from ion neutralization.
• NBE presents a promising alternative to IBE for advanced semiconductor lithography, improving pattern fidelity and process reliability.