Design and Implementation of a RFID Based Real-Time Location-Aware System in Clean Room

Application of automated material handling system (AMHS) to the semiconductor manufacturing factories is one of the most important steps in the automation process of semiconductor business. All cassettes in the vehicle of the transportation facility can send their positioning information through this system. Nevertheless, some positioning information may still be interfered or get lost if there is any relocation of the cassette inside the effective ranges of AMHS by operators. In order to retrieve these lost cassettes only manpower is possible, and the relocation process is time wasting and inefficient. In this paper, we have implemented a clean room real-time location aware system (CRRLS) that is based on the technology of RFID (radiofrequency identification). The proposed system can reveal the positioning information of the cassette in the clean room by analyzing the received radio frequency energy information. Moreover, we establish a transmitting model of radio signal, and used this model to estimate distance between RFID tag and readers. A triangular positioning algorithm is developed to estimate the location and its 2-dimensional coordinate of the cassette. Furthermore, reusable RFID tags can save additional information sent by the transceivers and data of parameters for the production process to reduce the possibility of severe damage because of wrong parameters setting. As a result, competitive advantage of the semiconductor business can herewith greatly increase.