Make Better Devices In Less Time

The NanoFrazor has several unique features to fabricate novel nanodevices and nanostructures that are difficult or not possible with conventional nanolithography methods. This benefits the users of all NanoFrazor systems to:

  • Pioneer new science and technology
  • Trigger and realize new ideas and innovations
  • Generate new collaborations and funding sources easily

Furthermore, no vacuum or high voltage is necessary for the NanoFrazor systems which can be setup easily in any laboratory environment. This comparative simplicity and ease-of-use of the NanoFrazor, together with the rapid-prototyping capabilities add extra benefits to the users like:

  • Low threshold to quickly try out new ideas for processes and materials
  • Several iterations of device designs in less time due to the quick turnaround
  • Very little risk of downtime and maintenance delays

These benefits are possible due to the following unique technological key features of the NanoFrazor technology:

High-Resolution Direct-Write Nanolithography

The heated NanoFrazor tip directly evaporates the thermally responsive resist without requiring any development or proximity corrections. This enables patterning of complex shapes that are not possible with beam based nanolithography methods. The directly written shapes reflect the geometry of the cantilever tip.

A lateral resolution of 8 nm half-pitch has been demonstrated in PPA resist and a resolution below 25 nm half-pitch is achieved on a regular basis.

SEM image of 9 nm wide trenches with a half-pitch of 13.8 nm etched into Si. No “dose” correction was necessary either for the isolated parallel lines or for the sharp corners

High Speed

Evaporation of the resist by the heated NanoFrazor tip can take as little as 1 microsecond. This is around 1000 times faster than other tip-based lithography methods like local anodic oxidation or dip pen lithography which require milliseconds for each single write event. However, like any other serial high-resolution nanolithography method, the NanoFrazor can take a very long time to cover larger areas completely. We recommend applying Mix-and-Match lithography whenever appropriate.

Please contact us for more information about the integrated DLS Mix-and-Match laser writer options for the NanoFrazor.

Pattern with 40 nm pixel size written in less than 1 second. (Paul et al., Nanotechnology, 2010)

In-situ Topography Imaging

The NanoFrazor uses the same tip for both patterning and imaging the sample surface topography. The patented NanoFrazor imaging method is performed at a high speed of typically 1 mm/s with sub-nm vertical resolution and single nanometer lateral resolution. The topography can be imaged before, after or even during the patterning process.

The unique in-situ imaging capability saves the user a lot of time for metrology and inspection and enables novel concepts for lithography like Closed-Loop Lithography, Markerless Overlay and Correlation Stitching.

Topography image of single layer MoS2 flake buried under resist with overlay pattern in PPA with the NanoFrazor

Closed-Loop Lithography

The final shape of the written pattern is continuously measured and inspected during the NanoFrazor lithography process itself. Even tiny deviations from the target design are detected and used as input for immediate automated adjustments of the patterning parameters, like e.g. the applied electrostatic actuation force.

This unique and patented method, called Closed-Loop Lithography (CLL), provides robustness against external disturbances and guarantees a reliable patterning process.

Examples of 3D live demos with a NanoFrazor Explore at conferences. The 5 μm wide 3D pictures of visitors have been patterned and simultaneously imaged within 30 seconds

Markerless Overlay

Overlay – the accurate alignment of lithographic patterns relative to existing structures – is often one of the most critical challenges for device fabrication. Such existing structures can be lithographically defined like electrodes and optical waveguides, or located at unknown positions like randomly assembled nanowires and 2D material flakes.

The in-situ imaging capability of the NanoFrazor offers a very accurate overlay method that does not require sample alignment using artificial marker structures. As the topography from the existing structures buried under the resist layers can be easily detected, they themselves serve as a perfect reference for the alignment of NanoFrazor patterns relative to them.

Overlay accuracy better than 5 nm has been shown using the NanoFrazor.

Simple and accurate overlay of electrodes on a randomly assembled nanowire without damage from a charged particle beam

Correlation Stitching

To guarantee continuous patterning over areas larger than the piezo scan range, write fields must be stitched together. Accurate stitching between two subsequent write fields can be achieved with the NanoFrazor by imaging the surface before patterning the second write field. Cross correlation of the two images is then used to determine the misalignment between the two fields which can be corrected accordingly by the piezo stages while patterning the second field.

Stitching errors below 10 nm have been demonstrated using this method.

Reflective computer generated hologram with 100’000’000 pixels stitched from 100 fields of size 50 μm x 50 μm with no visible stitching errors

No Damage of Delicate Materials

Beam based lithography technologies like electron or ion beam lithography can permanently damage the sample. The resist absorbs only a small fraction of the high beam energy and the majority of the energy is actually absorbed by the underlying layers. Damages range from trapped charges in insulating layers and permanent crosslinks with organics to creation of vacancies, lattice defects, gas bubbles and implanted ions.

This contrasts with the NanoFrazor, where energy in the form of heat is largely absorbed by the top layer of the resist stack. Heating of the underlying substrate is negligible and delicate materials like 2D materials or topological insulators stay unharmed.

50 nm wide top gates overlaid on an InAs nanowire without exposure of the nanowire and the thin gate oxide by an electron beam (courtesy of IBM Research Zurich)

Wide Choice of Materials and Pattern Transfer Processes

The 2D and 3D patterns written into resist by NanoFrazor lithography can be transferred into almost any material using a wide choice of pattern transfer methods. SwissLitho and its collaborators optimized a wide range of such processes for the PPA resist. We are happy to support you in establishing the most suitable processes for your application at your facility.

For example, a simple lift-off process is commonly used for the fabrication of metal electrodes. Methods for direct transfer of the accurate 3D resist patterns include reactive ion etching, electroplating and soft molding.

For pattern transfer with very high lateral resolution and high aspect ratio, we recommend using a stack of thin hardmasks. Similar hardmask stacks are usually also used in the semiconductor industry for very high-resolution pattern transfer with optical DUV and EUV lithography. However, such hardmask processes are very difficult to apply with conventional beam based prototyping methods, because of issues with the charged particle beams and the insulating hardmask multilayers. The NanoFrazor doesn’t face this issue as no charged particle beams are used and so, hardmask multilayers are now commonly applied in combination with NanoFrazor lithography.

Features below 10 nm width and as dense as 11 nm half-pitch have been fabricated in Si using the hardmask approach.

Plasmonic antennae with around 10 nm gaps made with Au lift-off

Thermal Nanoscale Experiments

The temperature of the tip’s micro-heater can be controlled accurately between room temperature and up to around 1100°C. This allows a wide range of experiments besides the standard NanoFrazor lithography using evaporating resists.

Heated tips have been used in various ways for precise triggering of chemical reactions or phase transitions – often referred to as Thermochemical or Thermally Assisted Scanning Probe Lithography.

Have a look at our publications list for examples of this approach.