Ultra-Thin Resists for Advanced Lithography

The continuous reduction of feature sizes in integrated circuits (IC) is driving the development of advanced lithographic techniques that enable patterning of sub-100-nm features with good fidelity and process margins. Requirements for printing these sub-100-nm features includes tight control of critical dimensions (CD), line edge roughness, and resist profiles. Reduction in exposure wavelengths to 157 nm and extreme ultraviolet (EUV) is pushing the development of new families of resist systems and the use of thin imaging layers that overcome the high absorption by materials of 157-nm and EUV radiation. In addition, thin imaging techniques may provide benefits for low-k1 and high-NA lithography using 193-nm radiation. The use of ultra-thin resists (UTR) introduces new concerns for resist properties including the possibility for increased defectivity and the reduction in etch resistance. In this paper, we describe results of studies using ultra-thin resist integrations to build working devices. These investigations have shown that UTR are not inherently limited by defectivity, and working devices with high yield have been fabricated using UTR integrations on multiple levels.