In semiconductor production plants a highly clean state is required. In a plant building, through which air is forcibly circulated, a clean room in a low or medium cleanliness state is formed using a filter. A plurality of processing units are provided in the clean room and held in a high cleanliness...http://www.google.com/patents/US4923352?utm_source=gb-gplus-sharePatent US4923352 - System for manufacturing semiconductor under clean condition
