Single-component molecular resists containing bound photoacid generator functionality

A series of single-component molecular resists was designed, synthesized, characterized, and patterned using 100-keV e-beam lithography. An onium salt photoacid generator-based single-component resist system (referred to here as TAS) that creates a free photoacid upon exposure is shown to produce a low line edge roughness (LER) of 3.9 nm (3) but was limited in resolution due to photoacid diffusion. A different single-component molecular resist (referred to here as NBB) with a covalently bound nonionic photoacid generator, i.e., one in which the photoacid anion is bound to the resist core, was also synthesized. NBB was found to exhibit an improved resolution of 40 nm due to reduced photoacid diffusion while maintaining a good LER and line width roughness (LWR) of 3.9 nm and 5.6 nm, respectively. Despite the small size of NBB, it was found to exhibit a glass transition temperature of 82 °C. It also showed good adhesion, formed high-quality films, and showed no dark erosion during development. These compounds demonstrate that it is possible to form single-component molecular resists using both ionic and nonionic photoacid generators and that such small molecule resists can provide all the basic requirements to serve as functional chemically amplified resists.

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