Lithographic performance of 193 nm single and bi-layer materials.

For 193nm lithography several resist options are available such as single layer in combination with anti-reflective layers, bi-layer and top surface imaging. Single layer resist materials are preferred by the industry because of their limited complexity. A bi-layer resist process however has its inherent resolution and processing latitudes advantage as the imaging takes place in a thin top resist layer. Both single layer and bi-layer resists havebeen evaluated in terms of lithographic performance such as resolution, linearity, process windows and proximity effect. While satisfactory results are obtained with the single layer resist, the bi-layer results are still superior. Critical step in the bi-layer process is the dry development in an oxygen plasma. The dry development step has been optimised. The bi-layer resist shows a resolution down to 0.12μm with wide processing latitudes, adequatereflection control and good dry etch resistance. The resolution and processing windows were even further increased by the use of off-axis illumination.