Supporting future DRAM overlay and EPE roadmaps with the NXT:2100i

Abstract

The foundations of leading edge DRAM manufacturing are built on accurate EUV lithography exposures in close synergy with cutting-edge immersion layers as well as advanced patterning schemes (e.g. self-aligned multiple patterning). Final device yield critically depends on the subsequent and accurate stacking of multiple layers with device features of precise width and edge placement. To support the ever-decreasing requirements for both the EUV as well as the DUV, (edge) placement accuracy, scanner enhancements are required on both platforms.In this paper we report on the improvements of the NXT:2100i immersion scanner to further reduce the (edge) placement errors within the die (intra-field) and across the full wafer (inter-field). The NXT:2100i incorporates a new projection optics with built-in distortion manipulator that extends the intra-field correction capability for both X and Y directions. The external overlay interface is extended with the distortion manipulator degrees of freedom to handle high spatial frequent distortion data of a to-be-matched scanner or high spatial frequent overlay fingerprints measured by after develop or after etch metrology. Thermal conditioning of the reticle is improved with a fast conditioned internal reticle library resulting in lower reticle-to-reticle temperature variation. Improved lens metrology (aberrations) and reticle align accuracy (alignment/overlay) is achieved with a better integrated image sensor. Improved alignment accuracy and reduced alignment process dependencies for wafer alignment are realized with 12-colors parallel measurements and by adding more alignment marks measurements at the wafer measure side without throughput impact. In concert with the hardware components, various software algorithms are updated, yielding improved inter-and intra-field overlay setup and improved reticle heating induced overlay.We will detail the specific module performance items as well as the system performance of the NXT:2100i scanner, both in reference (DRAM relevant overlay) to DUV as well as to EUV scanners.

Impact of high-NA half-field to full-field overlay performance by Monte Carlo simulations

“…ASML offers different overlay improvement options depending on the full field scanner of choice. Deep Ultra Violet (DUV) scanners such as the NXT:2100 can be adjusted for up to 57 correctable overlay parameters with the OVO4 packages 7 . In comparison, an EUV scanner like the NXE:3600 can have two overlay packages, OVO2 and OVO3, enabling respectively 18 or 33 correctable overlay parameters.…”