Extreme ultraviolet (EUV) lithography currently dominates the frontier of semiconductor fabrication. Photoresists must satisfy increasingly strict pattern fidelity requirements to realize the significant enhancements in resolution offered by EUV technology. Traditional chemically amplified resists (CARs) have hit a barrier in the form of the resolution, line edge roughness, and sensitivity trade-off. This has been compounded by a lack of understanding of the chemical mechanism associated with the EUV process. Here, we synthesize a series of novel EUV photoresists based on a self-immolative, acid-labile poly­(acetal) system. These systems are shown to be commercially viable under current EUV requirements. Careful study of the resists’ degradation pathways has enabled the identification of a remarkable photoacid generator (PAG) that functions as both an acid generator and base quencher, enabling further improvements over previous resists. density functional theory calculations reveal, for the first time, the connection between the PAG activation barrier and resist sensitivity and suggests why attempts to use electron-beam lithography to predict EUV performance have failed.

The resolution, line edge roughness, and sensitivity (RLS) trade-off has fundamentally limited the lithographic performance of chemically amplified resists. Production of next-generation transistors using extreme ultraviolet (EUV) lithography depends on a solution to this problem. A resist that simultaneously increases the effective reaction radius of its photogenerated acids while limiting their diffusion radius should provide an elegant solution to the RLS barrier. Here, we describe a generalized synthetic approach to phthalaldehyde derivatives using sulfur­(VI) fluoride exchange click chemistry that dramatically expands usable chemical space by enabling virtually any non-ionic photoacid generator (PAG) to be tethered to phthalaldehyde. The resulting polymers represent the first ever PAG-tethered self-immolative resists in an architecture that simultaneously displays high contrast, extraordinary sensitivity, and low roughness under EUV exposure. We believe this class of resists will ultimately enable researchers to overcome the RLS trade-off.

Manipulation. All reactions were carried out using a standard glovebox or Schlenk techniques under nitrogen or argon gas.All polymerization reactions were performed using Schlenk techniques with reaction temperature controlled by dry ice/acetone bath. All silicon wafers were cleaned by hot Piranha solution before coating.

No abstract