Hydrogen 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-induced desorption spectroscopy (EBID). 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 three oxygen atoms (formula: HSiO3/2). For the first time, we have shown, via changes in the Si-H-2 peak at similar to 2200 cm(-1) in the Raman spectra and the release of SiHx products in EBID, that electron-beam-exposed material cross-links via a redistribution reaction. In addition, we observe the release of significantly more H-2 than SiH2 during EBID, which is indicative of additional reaction mechanisms. Furthermore, we compare the behavior of HSQ in response to both thermally and electron-beam induced reactions. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3425632]