Recently, the process of metallization in an electron‐beam evaporator has been shown to result in a buildup of trapped positive charge at the silicon‐sapphire interface during the fabrication of silicon‐on‐sapphire devices. This charge buildup can be attributed to radiation damage produced by x rays generated by electron impact on the aluminum to be evaporated. This paper gives the results of calculations of the radiation dose in the sapphire near the silicon‐sapphire interface due to the electron‐beam‐metallization process.