Characterization of Butyl Tin Photoresists with Electron Stimulated Desorption and Temperature Programmed Desorption
Performance enhancements of inorganic resists may transform next generation photolithography. These resists combine the potential for high-resolution patterning, while having high-sensitivity to extreme ultraviolet (EUV) radiation. Incorporating high-absorption coefficient elements with radiation sensitive ligands can significantly improve resist sensitivity. Upon EUV exposure a range of low-energy electrons (Ekin < 90 eV) are produced in the resist. These low-energy electrons drive chemistries that induce relative solubility differences between the exposed and unexposed regions. In this presentation, we discuss the patterning mechanisms for thin film n-butyl tin oxide hydroxide (BuSnOOH), which is a model organotin-based inorganic photoresist. We have characterized thermal and electron induced decomposition of BuSnOOH by temperature programmed desorption (TPD) and electron stimulated desorption (ESD), respectively. From the TPD studies, we find a desorption peak at ~653 K, which is due to decomposition of BuSnOOH, and the resulting desorption of the butyl ligand. A series of thermal desorption energy curves were obtained by inversion of the Polanyi Wigner TPD model, and we estimated that the butyl group desorption energy was 2.15eV - 2.7 eV for a range of prefactor values. This energy roughly corresponds to the dissociation energy for the Sn-C bond (2.05 eV). From the ESD studies, we find that the main desorption product is also related to the butyl group. We found that low-energy electrons (Ekin = 80eV) are very effective for the dissociation of the Sn-C bond. Desorption cross sections, obtained from the ESD data, were determined to be ~4.2 × 10-14 cm2. For both TPD and ESD we find that both thermal and electron stimulated chemistries are associated with breaking the Bu-Sn bond. We will describe how the combination of TPD and ESD allows us to gain mechanistic insights for organotin-based inorganic resists.