Ablation of Si-containing Polymers: Application to X-ray Lithography

X-ray-induced ablation of Si-containing polymers is investigated for application to the surface-imaging process in X-ray lithography. Polysilanes, polystyrene, and polymethacrylates are chosen for this study. Ultraviolet (UV) and Fourier-transfer infrared (FTIR) spectra are observed and all of the polymers are found to have positive tone characteristics against soft X-ray exposure. Based on measurements of remaining film thickness after exposure, polymethacrylates are found to have a high self development sensitivity. However, copolymerization gives no improvement in sensitivity. Oxygen reactive ion etching (O2-RIE) rates of these polymers are also measured and found to depend on the Si content of the polymer. A bilayer resist using the polymer as a surface imaging resist is patterned by X-ray exposure and subsequent dry etching. Applicability of Si-containing X-ray resist to self-development is presented.