Advanced process control: basic functionality requirements for lithography

Lithography in a high volume, state of the art manufacturing facility must have suitable systems in place to maintain control of critical device parameters such as pattern overlay (OL), and critical dimension (CD) on all parts manufactured. Methods of control such as litho cell qualification, wafer send ahead, extended tool preventive maintenance, and SPC alone are not only no longer sufficient to achieve the zero tolerance process budgets used at present, but are also detrimental to the cost effectiveness of current manufacturing. In order to achieve both the zero tolerance budgets and cost effective manufacturing, methods of advanced process control (APC) must be applied.