TitleElectron beam exposure mechanisms in hydrogen silsesquioxane investigated by vibrational spectroscopy and in-situ electron beam induced desorption AbstractHydrogen Silsesquioxane (HSQ) is used as a high-resolution resist with resolution down below 10-nm half-pitch. This material or materials with related functionalities could have widespread impact in nanolithography and nanoscience applications if the exposure mechanism was understood and instabilities controlled. Here we have directly investigated the exposure mechanism using vibrational spectroscopy (both Raman and Fourier transform Infrared) and electron beam desorption spectroscopy (EBDS). In the non-networked HSQ system, silicon atoms sit at the corners of a cubic structure. Each silicon is bonded to a hydrogen atom and bridges 3 oxygen atoms (formula: HSiO 3/2 ). For the first time, we have shown, via changes in the Si-H 2 peak at ~2200 cm -1 in the Raman spectra and and the release of SiH x products in EBID, that electron-beam-exposed material crosslinks via a redistribution reaction. In addition, we observe the release of significantly more H 2 than SiH 2 during EBID, which is indicative of additional reaction mechanisms. Additionally, we compare the behavior of HSQ in response to both thermal and electron-beam induced reactions.