Acid Diffusion and Lithographic Performance

Y.-Q. Rao, R. Sharma, M. Clark, P. Agarwal
The Dow Chemical Company, US

Keywords: acid diffusion, resist, TOF-SIMS

Summary:

As electronics devices continue to shrink and the information density continues to rise, the device structure continues to move to ever smaller dimension. To be able to print features as small as 10nm, extreme UV lithography (EUV) is being pursued. In EUV, a chemical amplification scheme, thin resist (less than 100 nm) and extremely short wavelength (~13.5 nm) light are being explored. In a chemical amplification resist, a photo acid generator (PAG), quencher base (QB) and resist polymer are mixed together to form a thin film on the substrate. Several complicated phenomena, miscibility, thin film densification, acid diffusion, and water diffusion and swelling, all contribute to the lithographic performance significantly. On the other hand, the glass transition and viscoelasticity, which dictate the polymeric behavior, do not follow the traditional bulk properties of the material because the treatment of the materials itself as the whole system breaks down as the physical dimension of the material is approaching its structural dimension (the thickness of a film less than 100 nm). In this talk, we will discuss the effect of acid diffusion and viscoelastic properties in resist films on their lithographic performance.