Field of Expertise: Advanced Material Science | |
Johannes Kofler(1), Florian Kolb(1), Andreas Klug(1), Emil J.W. List Kratochvil(1,2) The authors present a novel sensitive and robust electron beam-lithography lift off process using a commercially available chemically amplified positive tone 40XT photo resist. Ultra high resolution with sub-30 nm structures was already demonstrated with a good repeatability and stability using common positive tone resists such as PMMA (poly(methylmethacrylate)). However, due to their low sensitivities (> 100 μC/cm²), their practicability is limited to applications requiring small exposure-areas. In contrast, positive tone chemically amplified resists as the presented 40XT have a high sensitivity (< 10 μC/cm²). The drawback of these resists is that they are susceptible to basic air contaminants (e.g. amines) and process time variations leading to instabilities. Process parameters which reduce these influences such as prolonged post exposure bakes and development times lead to a lower resolution (> 150 nm) and contrast. We demonstrate that this trade-off between process stability and resolution/contrast can be circumvented by a conductive PEDOT:PSS (poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)) protective top-coating. As a result, it was possible to obtain a robust and sensitive (< 10 μC/cm²) process while maintaining a high resolution with a width of 80 nm and a pitch of 100 nm. An additional benefit of this coating is that charging substrates can be structured without using a metal layer. |