Imprint lithography has been shown to be an effective method for replication of nanometer-scale structures from a
template mold. Step-and-Flash Imprint Lithography (S-FILTM) employs a UV-photocurable imprint liquid, which
enables imprint processing at ambient temperature and pressure. The use of a transparent fused silica template facilitates
precise overlay. With this combination of capabilities, NIL is a multi-node technique that is suitable for advanced
prototyping of processes and devices to meet the anticipated needs of the semiconductor industry. However, since the
technology is 1X, it is critical to address the infrastructure associated with the fabrication of templates. An essential part
of this infrastructure is the capability to identify and repair template defects. Fused silica imprint templates are typically
produced from photomask substrates, and it is straightforward to make use of the tools and processes that have been
developed to repair commercial photomasks. However, the optical properties of the repaired region are of secondary
importance because S-FIL patterning is based on direct transfer of topography (rather than indirect transfer of an optical
image). As in conventional photolithography, both additive and subtractive repairs are required to correct a variety of
defect types. Repair techniques that are based on electron-beam induced chemical reactions have demonstrated the
capability to perform both additive (deposition) and subtractive (etching) processes at high resolution. This work is a
demonstration that electron-beam directed additive repair is capable of repairing fused silica template structures with
sub-100 nm resolution.
In order for Step and Flash Imprint Lithography S-FIL or any other imprint lithography to become truly viable for manufacturing, certain elements of the infrastructure must be present. In particular, these elements include; fast and precise Electron Beam (E-beam) pattern writing, ability to inspect, and a methodology to repair. The focus of this paper will be to investigate repair of clear and opaque defects on S-FIL templates using Focused Ion Beam (FIB) and Electron beam technologies. During this study, FEI's Accura XT FIB mask repair system was used to selectively mill opaque line edge defects as small as 45 nm in the Cr-based and 30 nm in the quartz-based patterns. Repairs to the Cr pattern achieved a placement offset of 8.8 nm with a one sigma value of 11.4 nm. Additionally, a series of trench cuts were made perpendicular through line segments to determine the minimum cut resolution. In an effort to repair clear defects within chrome patterns, studies were performed to deposit carbon or a proprietary metallization using either FEI's FIB platform or E-beam mask repair research tool. This paper will discuss the repair strategy used and include characterization of repairs through Scanning Electronic Microscopy (SEM) and Atomic Force Microscopy (AFM) imaging. Furthermore, repair efficiency was determined by assessing the ability of the repair to hold up through the remainder of the template fabrication process and ultimately pattern transfer of imprinted features.
Recently, the International Roadmap for Semiconductors (ITRS) has included imprint lithography on its roadmap, to be ready for production use in 2013 at the 32 nm node. Step and Flash Imprint Lithography (S-FILTM) is one of the promising new methods of imprint lithography being actively developed. Since S-FIL is a 1X printing technique, fabrication of templates is especially critical. S-FIL has previously demonstrated the ability to reliably print high resolution line/space and contact hole features into a silicon-rich etch barrier material. Beyond printing with S-FIL however, there is the requirement to develop low or zero bias, high selectivity dry etch processes needed to transfer printed images into the substrate. In this study, the feasibility and methodology of imprinting sub-80 nm contacts, and pattern transferring this image into an underlying oxide layer is demonstrated. Critical parameters such as e-beam dose and etch biases associated with template pillar fabrication, and biases associated with pattern transfer processes for sub-80 nm 1:1 and 1:2 pitch contacts are discussed. Wafer imprinting was done on 200 mm wafers using Molecular Imprints Inc., Imprio 100TM system.