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Rocking Brownian motors achieve directional motion in highly diffusive environments by combining an inherently asymmetric static potential energy landscape and an oscillating “rocking” force [1, 2]. Our nanofluidic imple- mentation [3] features a confining wall with a ratchet-type nano-topography and AC electric fields as driving force. The potential energy landscape is due to electrostatic interactions between the charged particles and wall surfaces in close proximity. Based on this scheme, we have developed a nanoparticle size-separation device [4]. Along the particle transport direction, one of the confining walls features a sawtooth-like topography with a superimposed slope. In turn, we obtain a ratchet-shaped potential with increasing potential energy barrier heights caused by the decreasing nanofluidic gap. A sharp drop in particle current occurs as the potential barriers increase. The drop happens the later, the smaller the particle size. This allows for a sequential separation of the particle suspension into multiple sub-populations. The device was modeled by solving the Fokker-Planck equation. We show that the physics of the separation mechanism is governed by the energy landscape under forward tilt of the ratchet. The separation resolution is thus only dependent on the applied force. Experimentally, we demonstrate the separation of spherical gold particles of nominal 80 and 100 nm diameters with an applied voltage of 3.5 V and a sorting time of 20 s. We achieve a resolution of 2 nm, in accordance with our simulation results.

In the presented work solvent-free film preparation from molecular glass resists, the evaluation of the patterning performance using thermal scanning probe lithography (tSPL) and an efficient etch transfer process are demonstrated. As the presented materials have a high tendency to crystallize and thus form crystalline films of bad quality when processed by solution casting, two component mixtures prepared by coevaporation were investigated. Stable amorphous films were obtained by selecting compatible material pairs for the coevaporation. One optimized material pair is based on trissubstituted, twisted resist materials with a distinct difference in molecular design. Here a high resolution tSPL prepared pattern of 18 nm half pitch in a 10 nm thick film is demonstrated. A further optimization is reported for “small” cubic silsequioxane molecules. Again single component films show independent to applied film preparation techniques bad film forming properties due to the high crystallinity of the symmetric cubic silsequioxane molecules. But coevaporation of the phenyl substituted octaphenylsilsequioxane combined with the fully aromatic 2,2',7,7'-tetraphenyl-9,9'-spirobi[fluorene] results in stable amorphous thin films. tSPL investigations demonstrate the patternability by writing high resolution line features of 20 nm half pitch. An important advantage of such a silicon rich resist material is that it can be directly converted to SiO2, yielding to a patterned hardmask of SiO2. This proof of principle is demonstrated and an efficient pattern transfer of 60 nm half pitch line into the underlying HM8006 is reported.

In the presented work solvent-free film preparation from tailored molecular glass resists, their thermal analysis, the characterization of etch resistance for plasma etching transfer processes, and the evaluation of the patterning performance using scanning probe lithography (SPL) tools, in particular electric field and thermal based SPL, are demonstrated. Therefore a series of fully aromatic spiro-based and tris-substituted twisted resist materials were systematically investigated. The materials feature very high glass transition temperatures of up to 173 °C, which allows solvent-free thin film preparation by physical vapor deposition (PVD) due to their high thermal stability. The PVD prepared films offer distinct advantages compared to spin coated films such as no pinholes, defects, or residual solvent domains, which can locally affect the film properties. In addition, PVD prepared films do not need a post apply bake (PAB) and can be precisely prepared in the nanometer range layer thickness. An observed sufficient plasma etching resistance is promising for an efficient pattern transfer even by utilizing only 10 nm thin resist films. Their lithographic resolution potential is demonstrated by a positive and a negative tone patterning using electric field, current controlled scanning probe lithography (EF-CC-SPL) at the Technical University of Ilmenau or thermal scanning probe lithography (tSPL) investigations at the IBM Research - Zurich. High resolution tSPL prepared patterns of 11 nm half pitch and at 4 nm patterning depth are demonstrated.

The presented work deals with molecular glass resist materials based on (i) calix[4]resorcinarene resist systems, (ii) twisted fully aromatic biscarbazole-biphenyl materials, and (iii) fully aromatic spiro resist materials as new promising materials for Scanning Probe Lithography (SPL). Because of the non-chemically amplified resist nature and the absence of corresponding material diffusion, the novel SPL resists have the potential to increase the patterning resolution capabilities at a simultaneous reduction of the edge roughness (LER). In addition, these low molecular weight molecular glasses offer the advantage of solvent-free film preparation by physical vapor deposition (PVD). The PVD prepared films offer a number of advantages compared to spin coated ones such as no more pinholes, defects, or residual solvent domains, which can locally affect the film properties. These high-quality PVD films are ideal candidates for the direct patterning by SPL tools. Presented highlights are the thermal scanning probe lithography (tSPL) investigations at IBM Research - Zurich and the patterning by using electric field, current controlled scanning probe lithography (EF-CC-SPL) at the Technical University of Ilmenau. Further investigations on film forming behavior, etch resistance, and etch transfer are presented. Owing to the high-resolution probe based patterning capability in combination with their improved etch selectivity compared to reference polymeric resists the presented molecular glass resists are highly promising candidates for lithography at the single nanometer digit level.

Thermal Scanning Probe Lithography (tSPL) is an AFM based patterning technique, which uses heated tips to locally evaporate organic resists such as molecular glasses [1] or thermally sensitive polymers.[2][3] Organic resists offer the versatility of the lithography process known from the CMOS environment and simultaneously ensure a highly stable and low wear tip-sample contact due to the soft nature of the resists. Patterning quality is excellent up to a resolution of sub 15 nm,[1] at linear speeds of up to 20 mm/s and pixel rates of up to 500 kHz.[4] The patterning depth is proportional to the applied force which allows for the creation of 3-D profiles in a single patterning run.[2] In addition, non-destructive imaging can be done at pixel rates of more than 500 kHz.[4] If the thermal stimulus for writing the pattern is switched off the same tip can be used to record the written topography with Angstrom depth resolution. We utilize this unique feature of SPL to implement an efficient control system for reliable patterning at high speed and high resolution. We combine the writing and imaging process in a single raster scan of the surface. In this closed loop lithography (CLL) approach, we use the acquired data to optimize the writing parameters on the fly. Excellent control is in particular important for an accurate reproduction of complex 3D patterns. These novel patterning capabilities are equally important for a high quality transfer of two-dimensional patterns into the underlying substrate. We utilize an only 3-4 nm thick SiOx hardmask to amplify the 8±0.5 nm deep patterns created by tSPL into a 50 nm thick transfer polymer. The structures in the transfer polymer can be used to create metallic lines by a lift-off process or to further process the pattern into the substrate. Here we demonstrate the fabrication of 27 nm wide lines and trenches 60 nm deep into the Silicon substrate.[5] In addition, the combined read and write approach ensures that the lateral offset between read and write field is minimized. Thus we achieve high precision in marker-less stitching of patterning fields. A 2D cross-correlation technique is used to determine the offset of a neighboring patterning field relative to a previously written field with an accuracy of about 1 nm. We demonstrate stitching of 1 μm2 fields with ~5 nm accuracy and stitching of larger 10x10 μm2 fields with 10 nm accuracy.[6]

Heated tips offer the possibility to create arbitrary high-resolution nanostructures by local decomposition and evaporation of resist materials. Turnaround times of minutes are achieved with this patterning method due to the high-speed direct-write process and an in-situ imaging capability. Dense features with 10 nm half-pitch can be written into thin films of organic resists such as self-amplified depolymerization (SAD) polymers or molecular glasses. The patterning speed of tSPL has been increased far beyond usual scanning probe lithography (SPL) technologies and approaches the speed of Gaussian shaped electron beam lithography (EBL) for

A high-resolution probe based patterning method is presented using organic resists that respond to the presence of a hot tip by local material desorption. Thereby arbitrarily shaped patterns can be written in the organic films in the form of a topographic relief. The patterning process is highly reproducible and repeatable enabling the creation complex relief structures with arbitrary texture also in the vertical dimension. The patterns can be readily transferred into silicon using standard RIE technology. The new technique offers a cost-effective and competitive alternative to high-resolution electron-beam lithography in terms of both resolution and speed.