Transient-Assisted Processing (TAP): A Path to Low-Emission Dry Etching in the Ångström-Node Era

Plasma etching is a major source of greenhouse gas emissions in integrated circuit manufacturing. While existing etching technologies have primarily been optimized for throughput or precision, the next generation of plasma etching must also meet sustainability objectives. This includes minimizing the ecological impact of processing while maintaining compatibility with high-volume manufacturing (HVM) and the ability to precisely pattern ultrathin, complex material stacks. This study explores the sustainability potential of the recently introduced transient-assisted processing (TAP) after providing a comprehensive overview of the key characteristic features of this approach. The work was demonstrated on a standard extreme ultraviolet (EUV) lithography stack, comprising photoresist, spin-on glass (SoG), amorphous carbon (aC), SiO2, and TiN, patterned with a 24 nm pitch line-space design. TAP was benchmarked against a reference process based upon the conventional reactive ion etching (RIE), in terms of gas consumption, direct emission measurements, and via full-fab environmental modeling. TAP reduces gas consumption by relying on short gas pulsing and achieves high gas utilization rates by leveraging outgassing phenomena and time-dependent neutral-to-ion ratios. It has achieved up to a 7× reduction in the consumption of high global warming potential (GWP) gases and measured CO2-equivalent emissions, with no compromise in etch fidelity or throughput. Environmental impact was further assessed using the imec.netzero virtual fab model, which confirmed the substantial reductions of direct emissions and highlighted the influence of the platform configuration and regional electricity mix on energy-associated emissions. A hybrid approach is then proposed, matching the processing time of the reference RIE process to the reduction of direct emissions from TAP.