Particle concentrations over production tools during processing; a comparison of facilities worldwide

Examines eleven different worldwide semiconductor production facilities having various class levels (Class 10, Class 1 and Mini-environment or SMIF-System). It analyzes the effect of class level on the amount of contamination over the process tools during processing. A battery of tests measuring particulate levels were conducted. The tests include airborne particulate counts taken over an extended period of time (9-12 hours) in the vicinity of the wafers during processing. In addition, particle per wafer pass (PWP) data was collected. Statistical analysis is used to correlate the data from the different facilities, and the results are presented. Results show that the cleanroom cleanliness level over the process tools in conventional cleanrooms varies widely during processing. High particle counts were measured during particle-burst events, such as loading and unloading wafer cassettes into process equipment, cross contamination, maintenance activities, shift change and operator movement in the fab. The results show that the mini-environment facilities achieve and maintain a better cleanliness level over the process tools in comparison to conventional facility. Also, the number of particle-burst events are reduced when mini-environments are implemented.