764016

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Simultaneous optimization of dose and focus controls in advanced ArF immersion scanners Tsuyoshi Toki*a, Pavel Iziksonb, Junichi Kosugia, Naruo Sakasaia, Keiko Saotomea, Kazuaki Suzukia , Daniel Kandelb, John C. Robinson**d Yuji Koyanagic a Nikon Corporation, 201-9, Miizugahara, Kumagaya, Saitama, 360-8559, Japan b KLA-Tencor Corporation Israel, Haticshoret St., P.O.Box 143, Migdal Haemek 23100, Israel c KLA-Tencor Corporation Japan, 134 Godo-cho, Hodogaya-ku Yokohama, Kanagawa 240-0005, Japan d KLA-Tencor Corporation, One Technology Drive, Milpitas, California 95035, USA

ABSTRACT We have developed a new scheme of process control combining a CD metrology system and an exposure tool. A new model based on Neural Networks has been created in KLA-Tencor’s “KT Analyzer” which calculates the dose and focus errors simultaneously from CD parameters, such as mid CD and height information, measured by a scatterometry (OCD) measurement tool. The accuracy of this new model was confirmed by experiment. Nikon’s “CDU master” then calculated the control parameters for dose and focus per each field from the dose and focus error data of a reference wafer provided by KT Analyzer. Using the corrected parameters for dose and focus from CDU master, we exposed wafers on an NSR-S610C (ArF immersion scanner), and measured the CDU on a KLA SCD100 (OCD tool). As a result, we confirmed that CDU in the entire wafer can be improved more than 60% (from 3.36nm (3σ) to 1.28nm (3σ)). Keywords: lithography, process control, CDU, scatterometry, OCD measurement, Neural Network

1. INTRODUCTION ArF water immersion lithography is expected to be used down to 22nm hp node until EUVL becomes mature. The process margin is very small from 45nm hp node and double patterning techniques are required below 35nm hp. This is clearly shown in the ITRS roadmap for CDU (Figure 1).

5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 2018 [18nm ]

2017 [20nm ]

2016 [23nm ]

2015 [25nm ]

2014 [28nm ]

2013 [32nm ]

2012 [36nm ]

2011 [40nm ]

DRAM HP C D U (nm )

C D U (3sigm a) (nm )

50 45 40 35 30 25 20 15 10 5 0 2010 [45nm ]

D R A M 1/2 pitch (nm )

C D U requirem ent on IT R S

Y ear

Figure 1. CDU requirement trend based on ITRS 2009 [1].

*toki.tu@nikon.co.jp **John.Robinson@KLA-Tencor.com; phone 1 512-231-4221 Optical Microlithography XXIII, edited by Mircea V. Dusa, Will Conley, Proc. of SPIE Vol. 7640, 764016 · © 2010 SPIE · CCC code: 0277-786X/10/$18 · doi: 10.1117/12.846413

Proc. of SPIE Vol. 7640 764016-1 Downloaded from SPIE Digital Library on 12 Mar 2010 to 192.146.1.254. Terms of Use: http://spiedl.org/terms


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