Scanning x-ray microscopy investigations into the electron-beam exposure mechanism of hydrogen silsesquioxane resists

Abstract

Electron-beam exposed hydrogen silsesquioxane cross-linking chemistry is investigated by scanning transmission x-ray microscopy (STXM) and atomic force microscopy (AFM). Using STXM, a maximum in the chemical contrast is obtained by measuring the x-ray absorption at 535.4eV, corresponding to the 1sK-edge transition in oxygen. An area-dependent and dose-dependent chemical conversion is observed for feature sizes between 150nm and 10μm and doses between 0.4 and 40mC∕cm2. The activated (cross-linked) regions extend beyond the exposure zones, especially for higher dosed exposures. With AFM, thickness changes in the latent images (e-beam exposed but undeveloped) are observed, which also display a dependence on exposed area. Potential mechanisms, involving chemical diffusion outside the exposure zone, are discussed.