Defect reduction of high-density full-field patterns in jet and flash imprint lithography Lovejeet Singh Kang Luo Zhengmao Ye Frank Xu Gaddi Haase David Curran Dwayne LaBrake Douglas Resnick S.V. Sreenivasan
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J. Micro/Nanolith. MEMS MOEMS 10(3), 033018 (Jul–Sep 2011)
Defect reduction of high-density full-field patterns in jet and flash imprint lithography Lovejeet Singh Kang Luo Zhengmao Ye Frank Xu Gaddi Haase David Curran Dwayne LaBrake Douglas Resnick S.V. Sreenivasan Molecular Imprints Inc. 1807-C W. Braker Lane Austin, Texas 78758 E-mail:
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Abstract. Acceptance of imprint lithography for manufacturing will require demonstration that it can attain defect levels commensurate with the defect specifications of high-end memory devices. We summarize the results of defect inspections focusing on two key defect types: random nonfill defects occurring during the resist filling process and repeater defects caused by interactions with particles on the substrate. Nonfill defectivity must always be considered within the context of process throughput. The key limiting throughput step in an imprint process is resist filling time. Repeater defects typically have two main sources: mask defects and particle-related defects. Previous studies have indicated that soft particles tend to cause nonrepeating defects. Hard particles, on the other hand, can cause either resist plugging or mask damage. We use an Imprio 500 20– wafer per hour development tool to study both defect types. By carefully controlling the volume of inkjetted resist, optimizing the drop pattern, and controlling the resist fluid front during spreading, fill times of 1.5 s are achieved with nonfill defect levels of ∼1.2/cm2 . Longevity runs were used to study repeater defects, and a nickel contamination was identified as the C 2011 Society of Photo-Optical key source of particle-induced repeater defects. Instrumentation Engineers (SPIE). [DOI: 10.1117/1.3625635]
Subject terms: jet and flash imprint lithography; J-FIL; imprint lithography; imprint masks; templates; defectivity; nonfill defects; repeater defects. Paper 11070PR received May 11, 2011; revised manuscript received Jul. 19, 2011; accepted for publication Jul. 27, 2011; published online Sep. 14, 2011.
1 Introduction Imprint lithography has been shown to be an effective technique for replication of nanoscale features.1, 2 Jet and flash imprint lithography (J-FILTM ) involves the field-by-field deposition and exposure of a low-viscosity resist deposited by jetting technology onto the substrate.3–8 The patterned mask is lowered into the fluid, which then quickly flows into the relief patterns in the mask by capillary action. Following this filling step, the resist is cross-linked under UV radiation and then the mask is removed, leaving a patterned resist on the substrate. Acceptance of imprint lithography for manufacturing will require demonstration that it can attain defect levels commensurate with the defect specifications of high-end memory devices. Typical defectivity targets are on the order of 0.10/cm2 . Recent studies have marked excellent progress in reducing defects on the mask blank, patterned mask, and imprinted wafer. The master mask blank, which consists of a thin (
