Patterns written by the NanoFrazor into polyphthalaldehyde (PPA) can be transferred into other materials using standard clean room processes. PPA as a resist has a good etch resistance for reactive-ion etching (RIE), which is an efficient way to transfer the written patterns into materials like silicon.

Below are 5 different methods of pattern transfer using the NanoFrazor technology.

2D Etch Transfer

Applications of 2D etch transfer are, for example, semiconductors, as high resolution (< 20 nm half-pitch possible), high aspect-ratio (amplification in depth up to 50x) and low line edge roughness (< 3 nm, 3σ) are required.

The etch process involves multiple steps of RIE (e.g. oxygen and fluorine) steps using a 3-layer stack (e.g. PPA, SiO2, JSR HM8006). In a single RIE step, patterns can be transferred into silicon with a subsequent depth amplification. A tri-layer stack is recommended to achieve even better depth amplification, vertical walls or undercuts. A SiO2 hardmask and a cross-linked polymer below the PPA resist have proven to allow a depth amplification by 50x. High-resolution structures in PPA have been transferred by RIE and achieved an exceptionally low 1σ-line edge roughness below 1 nm.

3D Etch Transfer

Applications for 3D etch-transfer are, for example, stamps for nanoimprint lithography (NIL), optical devices or multilevel data storage.

The 3D structure is first written directly into the PPA, followed by RIE (e.g. fluorine). During the transfer into the substrate (e.g. Si), the 3D shape is stretched proportional to the etch contrast (which is, for example, 1:3 in the case of SF6).

With the CTI Project Nano2Micro we aim at increasing the etch contrast to increase the achievable depth range to the few-micrometer range.

Lift Off

Typical usage scenarios for lift-off are metals, contacting of nanowires or other devices in combination with overlay.

When a resolution below 20 nm is required, a 3-layer stack on top of the substrate (e.g. PPA, SiO2, PMMA) is recommended. After RIE (e.g. oxygen and fluorine), metal deposition is followed by lift-off. An alternative, simple lift-off scheme uses PMGI (polymethylglutarimide) resist below the PPA. Instead of RIE, only wet development has to be used for the desired undercut, greatly reducing general equipment demands for creating sub-100 nm metal structures.

Self Assembly

One application for self-assembly is the accurate placement of nanoparticles (e.g. quantum dots) onto substrates and their integration into devices in combination with overlay.

In the process, shape-matching traps in the PPA are created using the NanoFrazor. Using capillary assembly, particles from a colloidal suspension are trapped. After sublimation of the PPA on a hot-plate, the nanoparticles are transferred to substrate.

3D Plating

The applications for 3D plating are plasmonic devices and creating  molds for injection molding.

During the process, the 3D structure is first written the PPA on a substrate, followed by electroplating of e.g. nickel. Afterwards, the mold with the inverted 3D structure is separated from the substrate and can be further used for replication by e.g. injection molding.