Viscoelastic Properties of Nanoscale Organic Thin Films and its Correlation with Lithographic Performance

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

Keywords: nanocoating, viscoelasticity, transport, lithography

Summary:

One of the important applications of nanoscale organic thin films is in the advanced lithography. To be able to print features as small as 10nm, 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 characterization of viscoelastic properties in thin films using tools such as ellipsometer, quartz crystal microbalance (QCM), atomic force microscope (AFM) and vibrational spectroscopy. We will illustrate the importance of the viscoelastic properties of thin films to their performance in advanced lithography.