B a c kg r o u n d
Lithography
ASML reduces DUV overlay error to 1 nanometer In a balancing game between precision and productivity, ASML has increased the throughput to 295 wafers per hour, while reaching an overlay error milestone of 1 nanometer in its new Twinscan NXT:2050i. The first 15 systems have already been shipped.
Credit: ASML
René Raaijmakers
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SML’s engineers continue to improve the overlay in its most advanced immersion scanners. Since the introduction of the NXT:1950i platform in 2010, the overlay error dropped from 3 nanometers to 1.4 nanometers in the NXT:2000i two years ago. At the same time, the throughput increased from 175 to 275 wafers per hour. “As always in our industry, we needed to do better,” says Bart Paarhuis, who presented the latest overlay results on ASML’s most recent DUV system, the Twinscan NXT:2050i, 20
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at the online Bits&Chips High Tech Systems 2021 conference. “Customers requested additional improvements. The logic manufacturers want better DUV-to-EUV matching for their 3-nanometer node and our memory customers want better overlay when patterning successive layers on the same chip by the same DUV scanner. And everyone is asking for higher productivity.” To meet these requests, ASML introduced the NXT:2050i, with a new thermally improved wafer handler, a more accurate wafer stage, a more wear-resistant wafer
table, an improved light source, a new immersion hood for lower defectivity and a 2050 projection lens with reduced overlay fingerprint as main features. The reticle stage now has reduced distortion of the reticle during clamping. Also, many software improvements were made. For the development of this new immersion scanner, ASML collaborated with various teams and suppliers on the wafer handler (VDL), the wafer stage (VDL and Kyocera), the wafer table (Berliner Glass), the production of the immersion hood
