The suitability of strontium and barium fluoride as electron beam resist materials has been studied. Their sensitivity to high energy electron beams was measured, and the exposure mechanisms were described using scanning transmission electron microscopy. The effect of crystallite size and film composition on the exposure and development conditions of these inorganic resist systems were investigated. Finally, these resists were directly used as etch masks on gallium arsenide, and their performance was evaluated. Both barium and strontium fluoride were found to be sensitive negative resists, requiring exposure doses of 25–100 μC/cm2. The resolution of pure strontium and barium fluoride is limited by the grain size of the original fluoride deposits. The resolution and development conditions were improved by deposition of a mixture of barium and strontium fluoride (of approximately 50 at. % BaF2 in SrF2), which yielded line resolutions of better than 100 nm. All of these fluorides are extremely resistant to reactive ion etching with halogen containing gases and can be used as etch masks to pattern GaAs.