Thermal cantilevers originating from the IBM Millipede project are the core of the NanoFrazor technology. The cantilevers feature a heatable ultra-sharp tip and an integrated distance and topography sensor. This, along with a fast and precise electrostatic actuation mechanism allows for high speed and high resolution 2D and 3D patterning and imaging.

All NanoFrazor cantilevers are made of silicon. The fabrication of the NanoFrazor cantilevers is optimized to achieve ultra-sharp tips, accurate tip temperature control, fast actuation and high imaging sensitivity. The design, working principle and fabrication process is very different from AFM cantilevers and hence the NanoFrazor cantilevers are not compatible with any AFM.

At SwissLitho, we use multi-physics simulations of the electrical, thermal and mechanical properties in order to continuously improve the performance of the cantilevers for the diverse patterning and imaging applications.

The temperature of the resistive tip heater can be set up to 1100°C with a resolution of one Kelvin . The cantilever starts to distort above this temperature. The temperature calibration for a new cantilever is automatically performed in less than one second using the electrical characteristics of the tip heater and a fit from our multi-physics simulations. We published the details on this calibration scheme recently in the Journal of Applied Physics.

The unique integrated distance and topography sensor is a crucial feature of the NanoFrazor operation. It allows for fast and high-resolution imaging of the surface topography. Furthermore, it ensures that the distance of the tip from the surface is maintained constant during patterning. The heat conduction based cantilever sensor is automatically calibrated within one second using the well-calibrated Z piezo scanner as a reference.

Key Features of the NanoFrazor Cantilevers

  • Ultra-sharp silicon tips (as small as 2 nm in radius)
  • Fast and accurate tip heater up to 1000°C
  • Integrated sensitive distance and topography sensor
  • Fast and accurate electrostatic actuation
  • Parallel fabrication of full wafers with 450 cantilevers keeps the cost per cantilever low
  • Very easy and fast manual cantilever exchange and calibration
TEM image of a NanoFrazor tip with a radius of less than 2 nm (courtesy of Tevis Jacobs, University of Pittsburgh)

Monopede HPL

The Monopede HPL is the standard NanoFrazor cantilever. Today’s design of the HPL is the result of more than 20 years of improvements at IBM Research and since 2012, also at SwissLitho. The HPL has been optimized to enable reliable high resolution and high speed for both patterning and imaging.

Optical image of a Monopede HPL cantilever with a glowing tip

Monopede BSE

The Monopede BSE cantilever has been developed in recent years to enable fast and accurate patterning even on electrically insulating substrates. In contrast to the standard HPL cantilever, where patterning on electrically insulating substrates is possible only with some workarounds like using heat pulses as actuation instead of the fast and accurate electrostatic actuation – the BSE provides a stable solution with the integration of a backside electrode. Therefore, there is no need to contact the sample electrically, enabling a wider range of applications.

The BSE cantilevers are currently in the testing phase and will be available for all SwissLitho customers soon.

SEM image of a Monopede BSE cantilever

Decapede

Arrays of cantilevers is the obvious approach for increased throughput and faster and automated tip exchange. The Decapede array and the corresponding operation scheme was developed within the framework of the European project Single Nanometer Manufacturing. Proof-of-principle of patterning and imaging with the Decapede array has been successfully demonstrated.

The NanoFrazor Explore and the NanoFrazor Professional will receive the possibility for an optional upgrade to use the Decapedes.

SEM image of the Decapede

Millipede

IBM demonstrated an array of 4096 thermal cantilevers bonded onto a CMOS chip. This device, the so called “Millipede memory” was designed to write, read and erase data with ultra-high data storage density. An approach similar to the Millipede memory could be applied also for NanoFrazor lithography in order to scale up throughput tremendously.

This approach is only envisioned for industrial manufacturing applications with the NanoFrazor Industrial.

SEM image of the cantilever array in the IBM Millipede memory

NanoFrazor Cantilever Characteristics





Monopede HPL
Cantilever
Dimensions (l x w x t)67 μm x 76 μm x 0.45 μm
Resonance frequency1105 kHz +/- 5%
Stiffness10.27 N/m +/- 10%
Tip Dimensions
Radius of apex< 10 nm
Height of tip cone775 nm +/- 50 nm
Tip Heater
Size4 μm x 2 μm x 0.45 μm
Temperature rangeroom temperature - 1100 °C
Temperature resolution1 K
Thermal time constant6 μs
Distance & Topography Sensor
Sensor resolution< 0.5 nm
Sensor bandwidth150 kHz
Electrostatic Actuation
Capacitive counter electrodevia sample2
Mechanical pull-in / pull-out time< 2 μs
Resolution of deflection< 1 nm
Max deflection300 nm
Time for exchange and calibration 1 min

1 Values based on finite element simulations

2 Actuation also possible on insulating samples using pulsed heating