Shaped like a wafer, WaferSense Auto Vibration Sensors (AVS) can travel along an entire wafer path, collecting, recording and displaying exact vibration exposure. Placed either in standard cassettes, wafer stockers or in wafer boats that typically held 150 wafers in the 200 mm fab, the AVS moved through the entire diffusion tool, monitoring three-axis accelerations and vibrations at stocker locations with fans both on and off. Using Bluetooth technology, the wireless sensor provided wireless real-time data on tool vibration as it moved through the semiconductor process.
With companion software displaying data on a GUI, engineers were able to overlay vibration fingerprints and analyze vibration data. The diffusion furnace team ultimately identified excessive fan vibrations in wafer storage locations closest to the fans that caused wafers in these areas to “walk”, resulting in wafer handling problems and higher defects. Once identifying the cause of the wafer defects, engineers corrected wafer storage cassettes to prevent wafers from walking. The AVS’ data logging capabilities allowed the fab to establish new preventative maintenance requirements and process control standards for both the tools and engineers.
Detailed information on CyberOptics’ WaferSense products Auto Vibration Sensors is available online at http://www.cyberopticssemi.com/products/wafersense/avs .