On-product particle measurements for polysilicon process control

Reduction of test wafer use for the polysilicon diffusion process provides multiple benefits to the high-volume 200 mm processing line through cost savings and improved efficiency. Implementation of on product measurements for this process has required a number of changes in both philosophy and methodology. Polysilicon, which finds increased applications in semiconductor processing, requires in-line monitoring of both film thickness and on film particles. Historically, these measurements have been performed on separate test wafers included with product wafers during polysilicon processing. When these measurements are instead performed directly on product wafers, a number of benefits accrue, including reduced test wafer cost, reduced storage requirements, and reduced use of human resources necessary to process and reclaim test wafers. We show the necessary steps to implement on-product measurements with concern for overall manufacturing efficiency and the need to maintain appropriate control. Results on particle measurements on the Tencor 7600 Surfscan are presented