Thermal scanning probe lithography (t-SPL)
Being able to create nanometer accurate patterns and structures is at the heart of nanoscale science and technology.
We use a heated scanning probe tip to trigger locally the decomposition reaction of a thermally sensitive resist material. With each contact of the hot tip, a well-defined void is created, resulting in a pattern with high accuracy of its lateral and vertical dimensions.
“A unique feature of t‑SPL is the capability to write 3D profiles with nanometer accuracy in a single patterning run.”
—IBM scientist Armin Knoll
For 2D fabrication, we achieve <10 nm lateral resolution in the resist without it suffering from proximity effects. Linear speeds of up to 20 mm/s and pixel rates of up to 500 kHz have been demonstrated.
In t-SPL, the pattern is created and imaged on the fly, providing direct feedback of the lithography result to the user. The nanometer-precise imaging of the surface prior to patterning enables a sub-5-nanometer precise overlay to existing structures on the sample.
Using a dedicated transfer stack, we obtained high-resolution patterns with feature sizes down to 11 nm half pitch in substrate etching, metal lift-off or ion milling.
A unique feature of t‑SPL is the capability to write 3D profiles with nanometer accuracy in a single patterning run. We exploit this feature to gain control over objects in nanofluidic confinement.
Accurate Location and Manipulation of Nanoscaled Objects Buried under Spin-Coated Films
C. Rawlings, H. Wolf, J. L. Hedrick, D. J. Coady, U. Duerig, A. W. Knoll
ACS Nano, 9, 6188-6195 (2015).
We demonstrate, theoretically and experimentally, that after spin coating the resist topography is accurately obtained from a convolution operation of the existing topography with a symmetric Gaussian kernel whose parameters solely depend on the resist characteristics. We exploit this finding for a 3 nm precise overlay fabrication of metal contacts to an InAs nanowire with a diameter of 27 nm using thermal scanning probe lithography.
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IBM Research scientist
This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under Starting Grant No. 307079.
Single Nanometer Manufacturing
This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under Grant No. 318804.
Sub-20nm silicon patterning and metal lift-off using thermal scanning probe lithography
H. Wolf, C. Rawlings, P. Mensch, J. L. Hedrick, D. J. Coady, U. Duerig, A. W. Knoll
J. Vac. Sci. Technol. B, 33, 02B102 (2015).
We demonstrate that thermal scanning probe lithography (t-SPL) is capable of fabricating dense line patterns in silicon and metal lift-off features at sub-20 nm feature size. The dense silicon lines were written at a half pitch of 18.3 nm to a depth of 5 nm into a 9 nm polyphthalaldehyde thermal imaging layer by t-SPL. The patterns were transferred into silicon and were used for metal lift-off of high resolution patterns. A device application is demonstrated by fabricating 50 nm half pitch dense nickel contacts to an InAs nanowire.
Advanced scanning probe lithography
R. Garcia, A. W. Knoll, E. Riedo
Nat. Nanotech., 9, 577-587 (2014).
A review on state of the art scanning probe lithography methods.
Nanometer Accurate Markerless Pattern Overlay Using Thermal Scanning Probe Lithography
C. Rawlings, U. Duerig, J. Hedrick, D. Coady, A. Knoll
IEEE Transactions on Nanotechnology, 13, 1204-1212 (2014).
Thermal scanning probe lithography combines high-resolution patterning capabilities with the ability to read topography without causing resist exposure. As such, it is an ideal candidate for the implementation of markerless pattern overlay. We demonstrate theoretically and experimentally that alignment errors below 5 nm are possible for micron-sized features having an amplitude of just 4 nm. Further, we show that following proper calibration, a limiting overlay accuracy of 1.1 nm per axis is achievable.
Thermal probe mask-less lithography for 27.5 nm half-pitch Si technology
L. L. Cheong, P. Paul, F. Holzner, M. Despont, D. J. Coady, J. L. Hedrick, R. Allen, A. W. Knoll, U. Duerig
Nano Lett., 13, 4485-4491 (2013).
Thermal scanning probe lithography is used for creating lithographic patterns with 27.5 nm half-pitch line density in a 50 nm thick high carbon content organic resist on a Si substrate. A line-edge roughness after transfer of 2.7 nm (3σ) has been achieved. The patterns have also been transferred into 50 nm deep structures in the Si substrate with excellent conformal accuracy.
Nanoscale Contact-Radius Determination by Spectral Analysis of Polymer Roughness Images
A. W. Knoll
Langmuir, 29, 13958-13966 (2013).
In spite of the long history of atomic force microscopy (AFM) imaging of soft materials such as polymers, little is known about the detailed effect of a finite tip size and applied force on the imaging performance on such materials. Here we exploit the defined scaling of roughness amplitudes on amorphous polymer films to determine the contact radius of the imaging tip.
Rapid turnaround scanning probe nanolithography
P. Paul, A. Knoll, F. Holzner, M. Despont, U. Duerig
Nanotechnology, 22, 275306 (2011).
We present a complete lithography and metrology system based on thermomechanical writing into organic resists. Metrology is carried out using a thermoelectric topography sensing method. More specifically, we demonstrate a system with a patterning pixel clock of 500 kHz, 20 mm s − 1 linear scan speed, a positioning accuracy of 10 nm, a read-back frequency bandwidth of 100 000 line-pairs s − 1 and a turnaround time from patterning to qualifying metrology of 1 min. Thus, we demonstrate a nanolithography system capable of implementing rapid turnaround.
Field stitching in thermal probe lithography by means of surface roughness correlation
P. Paul, A. Knoll, F. Holzner, U. Duerig
Nanotechnology, 23, 385307 (2012).
A novel stitching method is presented which does not require special purpose alignment markers and which is particularly adapted to probe lithographic methods, enabling the writing of large patterns exceeding the size limitations imposed by high precision scan stages. The technique exploits the natural roughness of polymeric resist surfaces as a fingerprint marker for the sample position. The method has been put to the test in a thermal probe lithography experiment by writing a composite pattern consisting of five 10 μm × 10 μm fields which are seamlessly joined together. The observed stitching error of 10 nm between fields is dominated by inaccuracies of the scanning hardware used in the experiment and is not fundamentally limited by the method per se.
Probe-Based 3-D Nanolithography Using Self-Amplified Depolymerization Polymers
A. W. Knoll, D. Pires, O. Coulembier, P. Dubois, J. L. Hedrick, J. Frommer, U. Duerig
Adv. Mater., 22, 3361-3365 (2010).
3D patterning by means of probe-assisted thermal decomposition has been achieved on phthalaldehyde polymer films with 1 nm vertical resolution and 40 nm lateral resolution. Highly efficient patterning is enabled by a self-amplified depolymerization mechanism. Pixel writing speeds on the order of microseconds are demonstrated.
Nanoscale Three-Dimensional Patterning of Molecular Resists by Scanning Probes
D. Pires, J. L. Hedrick, A. De Silva, J. Frommer, B. Gotsmann, H. Wolf, M. Despont, U. Duerig, A. W. Knoll
Science, 328, 732-735 (2010).
We present a scanning probe lithography method based on the local desorption of a glassy organic resist by a heatable probe. We demonstrate patterning at a half pitch down to 15 nanometers without proximity corrections and with throughputs approaching those of Gaussian electron beam lithography at similar resolution. These patterns can be transferred to other substrates, and material can be removed in successive steps in order to fabricate complex three-dimensional structures.
Wear-less floating contact imaging of polymer surfaces
A. Knoll, H. Rothuizen, B. Gotsmann, U. Duerig
Nanotechnology, 21, 185701 (2010).
An atomic force microscopy (AFM) technique is described combining two operating modes that previously were mutually exclusive: gentle imaging of delicate surfaces requiring slow dynamic AFM techniques, and passive feedback contact mode AFM enabling ultra-fast imaging.
Probe-Based Nanolithography: Self-Amplified Depolymerization Media for Dry Lithography
O. Coulembier, A. Knoll, D. Pires, B. Gotsmann, U. Duerig, J. Frommer, R. Miller, P. Dubois, J. Hedrick
Macromolecules, 43, 572-574 (2009).
We present a polymeric material that has a low ceiling temperature where one degradation event is amplified via an unzipping of the entire chain.