Sub-100 nm lithography requires more understanding of photoresist material properties and processing conditions to achieve necessary critical dimension control of patterned structures. As resist thickness and feature linewidth decrease, fundamental material properties of the confined resist polymer can deviate from bulk values and impact important processing parameters such as the postexposure bake (PEB) temperature. The significance of these confinement-induced deviations on image or linewidth spread have just been reported recently. Using a high throughput combinatorial method, we employed temperature and thickness gradients to characterize the spatial extent of the reaction-diffusion process in a model chemically amplified photoresist system as a function of PEB temperatrue and protected polymer thickness. Bilayer samples were prepared by flow coating or spin casting and measured by interferometer and AFM.The velocity of the reaction front was significantly reduced with decreasing thickness of the protected polymer layer when its thickness was less than 60 nm or with decreasing PEB temperature under indentical processing conditions. Some disadvantages of combinatorial methods were also discussed.
Citation: Polymeric Materials: Science & Engineering
Pub Type: Journals
chemically amplified resist, combinaorial method, film thickness, post exposure bake