Proceedings Article | 19 March 2015
Lokesh Subramany, Woong Jae Chung, Karsten Gutjahr, Miguel Garcia-Medina, Christian Sparka, Lipkong Yap, Onur Demirer, Ramkumar Karur-Shanmugam, Brent Riggs, Vidya Ramanathan, John Robinson, Bill Pierson
Proc. SPIE. 9424, Metrology, Inspection, and Process Control for Microlithography XXIX
KEYWORDS: Metrology, Optical parametric oscillators, Scanners, Error analysis, Control systems, Process control, High volume manufacturing, Semiconducting wafers, Yield improvement, Overlay metrology
With the introduction of N2x and N1x process nodes, leading-edge factories are facing challenging demands of shrinking design margins. Previously un-corrected high-order signatures, and un-compensated temporal changes of high-order signatures, carry an important potential for improvement of on-product overlay (OPO). Until recently, static corrections per exposure (CPE), applied separately from the main APC correction, have been the industry’s standard for critical layers [1], [2]. This static correction is setup once per device and layer and then updated periodically or when a machine change point generates a new overlay signature. This is a non-ideal setup for two reasons. First, any drift or sudden shift in tool signature between two CPE update periods can cause worse OPO and a higher rework rate, or, even worse, lead to yield loss at end of line. Second, these corrections are made from full map measurements that can be in excess of 1,000 measurements per wafer [3]. <p> </p>Advanced overlay control algorithms utilizing Run-to-Run (R2R) CPE can be used to reduce the overlay signatures on product in High Volume Manufacturing (HVM) environments. In this paper, we demonstrate the results of a R2R CPE control scheme in HVM. The authors show an improvement up to 20% OPO Mean+3Sigma values on several critical immersion layers at the 28nm and 14 nm technology nodes, and a reduction of out-of-spec residual points per wafer (validated on full map). These results are attained by closely tracking process tool signature changes by means of APC, and with an affordable metrology load which is significantly smaller than full wafer measurements.
