Novel approach for precise control of oxide thickness

The control of gate oxide thickness has been very important for device characteristic and reliabilities in MOS transistor. The precise control of oxide thickness becomes more and more important, with continuous shrinkage of device dimension. Tighten SPC limits that mean the precise control of oxide thickness, make tool availability decrease. Because extra test run is necessary for adjustments of process time. The decrease of machines uptime will be serious problem in near future. We show the schemes for improvement of oxide thickness variation in use of multiple regression analysis and so on. Fluctuation in atmospheric pressure and process temperature, are main factors of thickness variation from process to process. New oxidation control system is fabricated to take atmospheric pressure and process temperature into account. This new system can download some process data and atmospheric data during the process. Oxidation time for target thickness is calculated in use of these data. Oxidation time is controlled from calculation value from process to process. This new system realizes precise control of oxide thickness without doing any test run.