Oct 26, 2010
Simplified high-resolution nanoimprint lithography
Nanoimprint lithography (NIL) is a powerful alternative to optical lithography for manufacturing nanoscale devices. Researchers from aBeam Technologies and the Molecular Foundry at Lawrence Berkeley National Laboratory have developed a simple imprint process to replicate sub-15 nm patterns across six inch wafers and transfer them into functional materials. Numerous applications from nanophotonics to nanofluidics will benefit from this low-cost technique for scaling down and developing new devices.
In a collaborative project led by aBeam Technologies for developing a new class of ultra-minaturized spectrometers, researchers Christophe Peroz and Scott Dhuey of Lawrence Berkeley National Laboratory's Molecular Foundry have devised an imprint process to replicate photonic chips at low cost.
The fabrication of templates is reduced to one single step, by using electron beam lithography (EBL) to directly pattern spin-on-glass (HSQ), which gives high-resolution patterning and avoids extra etching steps. The pattern replication is performed with a stepper UV-NIL – Imprio 55 from Molecular Imprints. Resist films are first spin-coated and slightly baked on 6 inch wafers.
Imprinting is performed at low pressure and ambient temperature, taking less than two minutes to replicate a pattern requiring more than 12 hours using EBL. In addition, this pattern can then be replicated across the entire wafer.
This process allows imprinting feature sizes from 10 µm to 14 nm. The high fidelity between the template and imprinted structures is verified with a difference in line edge roughness of less than 0.5 nm (3σ deviation value). Having minimal residual layer thickness and maximum homogeneity below the pattern is key in transferring the patterns from resist into functional material. The residual layer thickness is easily tuned to a minimum of less than 5 nm and a variation of approximately 3 nm across the wafer. This result is demonstrated in the pattern transfer via plasma etching of the smallest features sizes (13 nm) reported in the literature.
Nano-spectrometers and more
The technique has been used to fabricate nano-spectrometers (presented at the MNE 2010 Conference) and is suitable more generally for fabricating photonics and nanofluidic chips at low cost and high throughput.
More information can be found in the journal Nanotechnology.
About the author
This work was led by Dr Christophe Peroz and Scott Dhuey at the Molecular Foundry, Lawrence Berkeley National Laboratory, in Berkeley, California, US. The nanoimprint technology was developed by C Peroz, senior scientist at aBeam Technologies Inc., and S Dhuey, senior scientific engineer at the Molecular Foundry. Resist materials were provided by Dr Marko Volger, manager at Micro Resist Technologies GmBH. Dr Ying Wu, a postdoctoral scholar for Oxford Instruments, and Dr Deirdre Olynick, staff scientist at the Molecular Foundry, performed the silicon plasma etching. This work was also supported by Dr Stefano Cabrini, director of the Nanofabrication Facility at the Molecular Foundry. Work at the Molecular Foundry was supported by the Office of Science, Office of Basic Energy Sciences, of the US Department of Energy under contract no. DE-AC02- 05CH11231.