Particle contamination is a major concern in clean manufacturing. We present a model that predicts the diffusional particle contamination probability on inverted surfaces under the influence of gravity and thermophoresis at low pressure level. The model follows an analytical-statistical approach that can be solved using common spreadsheet software; therefore, not requiring major computational resources. The model revealed that thermophoresis can effectively eliminate diffusional deposition. Assuming that a contamination probability of 0.1% is acceptable, a thermal gradient of 10 Kcm protects against the deposition of all particles 30 nm with an initial distance of 1 mm or more.
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This work was supported by the Deutsche Forschungsgemeinschaft (DFG) under Grant No. AS291/1-1. The financial support is gratefully acknowledged.