Wafer Position Recognition Technology on Electrostatic Chucks

In semiconductor fabrication, precise wafer positioning is critical for achieving accurate doping, as even slight misalignments can result in significant performance issues during the final wafer acceptance test. Electrostatic chucks (ESCs) are widely utilized during the implantation process to securely hold wafers in place, relying on electrostatic forces to maintain stability and prevent movement. Ideally, wafers are centered on the ESCs; however, slight positional shifts may occur due to vacuum inconsistencies, transport irregularities, or notch misalignment. Recognizing and correcting wafer positioning are essential to ensuring process stability and yield. Despite its importance, no wafer positioning technology has been widely adopted in integrated circuit manufacturing. This paper introduces a wafer position recognition system designed for application on ESCs. Leveraging advanced imaging technology, the system employs a high-resolution camera to capture wafer images. By incorporating a triangular arrangement of calibration pins, a precise calibration area is established to facilitate accurate positioning. The system analyzes the gray values in four distinct zones along the wafer boundary to determine its exact position on the ESC. The proposed system effectively minimizes the risks of wafer misplacement, fall-off, or collision, thereby improving process stability, enhancing yield, and optimizing the overall efficiency of semiconductor fabrication processes.