Europeans Collaborate on LOCSS Project

-- Semiconductor International, 8/1/1999

A European consortium has developed equipment to stock and sort wafers as they wait in the fab between process steps, until the next process system becomes free to accept them. The Logistical Center for Sorting and Stocking (LOCSS) equipment maximizes time use between process steps to improve cost effectiveness and yield, while avoiding processing errors.

Partners in the consortium include the equipment maker ACR GmbH (Niedereschach, Germany), the Fraunhofer Institute for Production Techniques and Automation (Stuttgart, Germany) and the semiconductor manufacturers Mitel (Plymouth, U.K.), Thesys (Erfurt, Germany) and Atmel (Heilbronn, Germany). ACR has minimized the cost of producing the equipment by developing relationships with leading semiconductor producers and equipment makers to produce integrated systems that offer complete automation solutions. The IPA is primarily responsible for specifying links with the automation environment and cleanliness testing.

The consortium's prototype, fully automatic system has storage for up to 30 SMIF pods, with an extra four positions for wafer sorting and two ports for input and output of pods. The wafer sorter equipment has an integrated air cleaning system, plus ionizers to protect against electrostatic discharges and electromagnetic attraction of particles onto exposed wafers. This is of special importance when large wafers are being handled. The storage and wafer manipulation systems requires less than 4.4 m² of footprint. The system is expandable in units of 10 storage positions. The consortium is mainly using SMIF, so the first system is designed to handle pods; but it is intended to accommodate either SMIF or open cassettes. Filtration efficiencies of 99.99996% at 0.12 µm are essential, and the air flow and placement of mechanical devices is designed to ensure minimal particle contamination of wafers.

'The prototype is designed for 200 mm SMIF, with a 300 mm variant planned,' said Michael Gadd of ACR Automation UK Ltd. (Plymouth, UK). 'The ultra-clean integrated sorter avoids manual handling. ... It provides fully automated SMIF storage and wafer sorting in a footprint normally taken by a wafer stocker alone. A full cost-of-ownership model is available to compare the costs of this system with other alternatives. It is a good example of what a small company can achieve under the European Union collaborative programs.'