Recently it has become common to use dry vacuum pumps in semiconductor manufacturing processes. One problem with this application, however, is that etching by-products (e.g., aluminum trichloride, AlCl3) often deposit in the pumps. We have therefore studied these deposition processes and techniques to prevent deposits from forming. Our results indicate that the gas passage temperature must be kept above the sublimation temperature of the substance passing through the pump (e.g., AICl3) to prevent deposits from forming. To accomplish this, we modified the cooling jacket construction and changed the coolant from water to oil. The modified cooling jacket resulted in more uniform temperatures than with the previous cooling jacket. Considering AlCl3, the gas passage temperature was raised by about 50-degrees-C in order to keep the gas above the sublimation temperature of AlCl3. The modified pump was operated with a test semiconductor apparatus. A small amount of deposit was found after one year of equivalent running time, but it was not enough to interfere with proper operation of the pump. The same pump was also successfully demonstrated with a silicon nitride chemical vapor deposition process.