Defect reduction of high-density full-field patterns in jet and flash imprint lithography

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 key source of particle-induced repeater defects.