Feb. 20, 2008 – Nikon Corp. says it will have an “enhanced” version of its NSR-S610C ArF immersion scanner, optimized for double-patterning lithography process, ready for customers by 4Q08, billing the upgrade as a “low-risk solution” for developing double-patterning technology for use at the 32nm node.
Double-patterning — splitting the circuit pattern into two “coarser” patterns that can be printed separately and then combined — is gaining favor as a way to extend immersion litho from its “well-established” position in 45nm volume manufacturing down to 32nm, the company noted in a statement. Overlay accuracy is a particularly vexing challenge — combining two individual exposures “dramatically reduc[es] the overlay budget for each single exposure,” down to about 3nm-4nm.
With 32nm volume production generally expected between 2011-2013, chipmakers need to start developing double-pattering technology over the next year to have it ready, the company noted.
Feb. 21: Updated with more details about the planned upgrades to the NSR-S610C
Bernie Wood, Nikon director of marketing for Nikon’s North American litho subsidiary, indicated several changes to the S610C systems, which have been shipping since Feb. 2007. New interferometry lasers are located closer to the stage to improve accuracy and control; these interferometers can be impacted by variations in heat and airflow, so electrical units are being moved outside the tool or away from the chamber area, and airflow is being improved to produce a very uniform laminar flow, he told WaferNEWS. “Even the heat from the wafer loading system is controlled,” he said.
Other areas of improvement involve reducing vibration induced by the reticle and wafer stage. Wood noted that in Nikon’s new “Tandem” stage setup (one for exposures, one for calibrations) the calibration stage goes under the lens for each wafer exchange, enabling continual tool calibration.
Also, he revealed that Nikon is working on a new reticle stage with 6 degrees-of-freedom to improve accuracy, which will be incorporated into a new tool in 2009 for double patterning with “very low overlay and very high throughput.”
Wood also pointed to grid compensation software to address stage matching between tools (layer to layer matching), and “scanner match maker” (SMM), technology unveiled in Dec. 2007 by Nikon and KLA-Tencor, to help reduce distortion (improving tool-to-tool overlay) overlay errors in “mix and match” lithography setups. The S610C’s design also incorporates infrared aberration control (IAC) and a lens control system (iMAC) to reduce thermal and on-tool aberrations.