At the Japan’s big earthquake in 2011, the plasma etching tools have received the big damages from the earthquake. Most of the etching tools were not able to be used normally. Many particles were contaminated to the wafers during etching process because the chambers were corroded by the outgassed acids during shutdown for several days. Just when the big earthquake attacked to the plant, some etching tools were on maintenance (doing wet cleaning). Because the technicians had to escape out of the clean room with leaving the tools as it is, some halogen gasses (fluorine, chlorine, bromine and so on) were outgassed from the process chambers. These gasses were combined with humidity in the room and became kinds of acids. In the process modules, the metal components were mostly corroded by the halogen-outgas related acids. Especially, as the gas feeding lines were contaminated, a lot of defects were created by the particles. In fact, a lot of particles were counted on wafers because of the corrosion related particle contaminations. By wet wiping of the process chambers, there were some good effects to the particle reduction but it was NOT completed. So, we checked and replaced many parts such as gas feeding line with using some special techniques. After that, the particle level was recovered to normal. The surface particle monitor was used to check the in situ particle level and worked effective. For checking the particles in the gas line, we suggest new method to observe the particles by using a wafer and creating a shockwave in the gas line. Since we already had the reference data which was obtained before the earthquake, we could compare between the normal condition and the current condition from the viewpoint of chamber contamination.There is another serious problem such as RF reflection alarms. This alarm means that the RF power cannot be supplied to the tool appropriately. As we changed some chamber parts, polished contacting areas and also changed the software parameters, and then, the RF reflection alarms were eliminated completely. The static chamber impedance measurement was also done to check the electric property. We also recorded the normal condition of the plasma chamber before the earthquake. So, we could compare between the normal condition and the current condition from the viewpoint of chamber electricity. If we want to manage the risks of corrosion by the earthquake, not only the surface particle count but also the static chamber impedance and the conditions of metal parts should be recorded periodically during the normal situation.