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Imprint lithography has been shown to be an effective technique for replication of nano-scale features. Jet and
Flash Imprint Lithography (J-FIL) involves the field-by-field deposition and exposure of a low viscosity resist
deposited by jetting technology onto the substrate. 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 crosslinked 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. This work summarizes the results of defect inspections focusing on two key defect types; random non-fill
defects occurring during the resist filling process and repeater defects caused by interactions with particles on the
substrate.
Non-fill defectivity must always be considered within the context of process throughput. The key limiting
throughput step in an imprint process is resist filling time. As a result, it is critical to characterize the filling process by
measuring non-fill defectivity as a function of fill time. Repeater defects typically have two main sources; mask defects
and particle related defects. Previous studies have indicated that soft particles tend to cause non-repeating defects. Hard
particles, on the other hand, can cause either resist plugging or mask damage. In this work, an Imprio 500 twenty wafer
per hour (wph) development tool was used 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 seconds were achieved with non-fill defect levels of approximately 1.2/cm2.
Longevity runs were used to study repeater defects and a nickel contamination was identified as the key source of
particle induced repeater defects.
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