Nanobridge Stencil Enabling High Resolution Arbitrarily Shaped Metallic Thin Films on Various Substrates

Abstract

Stencil lithography (SL), which uses a perforated membrane as a reusable shadow mask to locally add material patterns on substrates provides a simple but versatile approach for the fabrication of functional devices on a large variety of substrate materials by physical vapor deposition (PVD). Mechanical stress induced by the accumulation of condensed material on the thin stencil membrane during the PVD step leads to stencil bending and breaking, therefore, suspended stencil membranes with arbitrary openings are, in practice, not possible. Here, a new approach to remedy this limitation is reported by introducing auxiliary bridges in stencils. These bridges prevent the suspended membrane from bending out of plane, thereby enabling aperture openings to have almost arbitrary geometry. These bridges are sufficiently narrow so that they do not entirely block the material deposition by PVD and thus create a continuous material pattern by taking advantage of the blurring effect. The successful metal deposition through the designed nanobridge stencil on a wide range of substrate materials underlines the usability and the versatility of the proposed stencil design. The work presented here provides a versatile fabrication method to produce arbitrarily shaped metal patterns that were previously impossible due to the topological constraints of nanostencils.

Stencil-Based Selective Surface Functionalization of Silicon Nanowires in 3D Device Architectures for Next-Generation Biochemical Sensors

“…Using a spacer-embedded stencil allows us to investigate blurring with much lower stencil–die gaps (as low as 10 μm for the current case). This surpasses the blurring investigations previously reported with Kapton tape spacers with a minimum thickness of 25 μm Figure d provides a detailed picture of the evolution of blurring as a function of h as well as w .…”

“…Blurring is defined as the unintended enlargement of the feature size patterned on the die compared to the dimensions of the stencil aperture. It is a function of the stencil–die gap, evaporation source size, evaporation source to stencil aperture distance, and type of substrate material. ,, To analyze specifically the effect of spacer thickness as an SL component, a series of different spacer thicknesses were employed on blank Si dice using the same e-beam evaporation equipment and configuration. Hence, any geometric blurring observed during the process is entirely dependent on the stencil–die gap.…”

“…Conventional approaches for the use of a spacer to maintain a safe stencil−substrate gap include employing Kapton tapes 55 or photoresists 56 or generating protrusions on the stencil by etching. 57 Moreover, these approaches need coating/removal of single-use photoresist or Kapton tape onto each substrate every time SL is conducted onto it to maintain the stencil− substrate gap.…”

“…This surpasses the blurring investigations previously reported with Kapton tape spacers with a minimum thickness of 25 μm. 55 Figure 5d provides a detailed picture of the evolution of blurring as a function of h as well as w. Although h is fixed to 10 μm for all SL work on NWs, a further reduction in h can be the most practical way forward to improve the pattern resolution for a given stencil geometry.…”