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Photo-Microlithography Fabrication of the Parts of a Micro-Mechanical Calculator
Abstract
A scanning photo-lithography process is developed to miniaturize mechanical calculators down to 40 μm in diameter for their calculating micro-gears. Our first moulding process span the dimensions from 1 mm to 60 μm for the micro-gears. Down to 100 μm, the planar calculator construction can still be based on a micro-manipulation of the moving parts under an optical microscope. Below and to reach the 10 μm, a double photo-lithography process was developed on a specific graphite/SiO2/Si wafer for mastering surface frictions. After a baking at 120 °C, the photo-resist becomes the material constitutive of all the moving micromechanical pieces. Only the rotation micro-axles remain metallic to ensure their good anchoring to the surface. A 2-digits micro-calculator is fabricated. In base 10, the carry propagation is demonstrated.
A planar molecular Pascaline mechanical calculator design is presented based on existing molecule gears which have 6 teeth consisting each of a tert-butyl group at the end of a shaft consisting of a phenyl group. The central phenyl-core is mounted on a single copper ad-atom which is the physical rotation axle on the superconducting Pb(111) surface. In order to construct such a planar molecular calculator, it is essential to realize two key mechanisms: the gearing that is in our design the molecular interlock across a monoatomic step edge and the carry function. Experimental results using the atom/molecule manipulation capability of one low temperature scanning tunneling microscope (LT-STM) of a unique LT-UHV 4-STM instruments demonstrate the feasibility of the above two mechanisms. Experiments with 2.2 nm in diameter large molecule gears are also presented with the same tert-butyl end tooth. They confirm that mutual tert-butyl groups of molecule gears on a terrace with the different heights of the monoatomic step on Pb(111) interlock and gear across the step edge, even if it is imperfect. In addition, experiments using a carry molecule gear containing one shaft with one phenyl group extended also confirmed that the carry mechanism works on the same Pb(111) terrace.KeywordsMolecular Pascaline mechanical calculatorMolecule gear trainCarry molecule gearMonoatomic stepped surfaceLT-UHV 4-STMSingle molecule manipulation
On a native graphite surface, 15 nm-thick solid-state nanogears are nanofabricated with a 30 nm outer diameter and six teeth. The nanogears are manipulated one at a time by the tip of an atomic force microscope using the sample stage displacements for the manipulation and recording of the corresponding manipulation signals. For step heights below 3.0 nm, nanogears are manipulated up and down native graphite surface step edges. In the absence of a central shaft per nanogear, gearing between nanogears is limited to a few 1/12 turns for six teeth. When the graphite step is higher than 3 nm, a rack-and-pinion mechanism was constructed along the edge with a 90 nm nanogear pinion.
Surface micromachining is characterized by the fabrication of
micromechanical structures from deposited thin films. Originally
employed for integrated circuits, films composed of materials such as
low-pressure chemical-vapor-deposition polycrystalline silicon, silicon
nitride, and silicon dioxides can be sequentially deposited and
selectively removed to build or “machine” three-dimensional
structures whose functionality typically requires that they be freed
from the planar substrate. Although the process to accomplish this
fabrication dates from the 1960's, its rapid extension over the past few
years and its application to batch fabrication of micromechanisms and of
monolithic microelectromechanical systems (MEMS) make a thorough review
of surface micromachining appropriate at this time. Four central issues
of consequence to the MEMS technologist are: (i) the understanding and
control of the material properties of microstructural films, such as
polycrystalline silicon, (ii) the release of the microstructure, for
example, by wet etching silicon dioxide sacrificial films, followed by
its drying and surface passivation, (iii) the constraints defined by the
combination of micromachining and integrated-circuit technologies when
fabricating monolithic sensor devices, and (iv) the methods, materials,
and practices used when packaging the completed device. Last, recent
developments of hinged structures for postrelease assembly,
high-aspect-ratio fabrication of molded parts from deposited thin films,
and the advent of deep anisotropic silicon etching hold promise to
extend markedly the capabilities of surface-micromachining technologies
Molecular dynamics (MD) simulation has been widely applied in various complex, dynamic processes at atomistic scale, because an MD simulation can provide some deformation details of materials in nano-processing and thus help to investigate the critical and important issues which cannot be fully revealed by experiments. Extensive research with the aid of MD simulation has provided insights for the development of nanotechnology. This paper reviews the fundamentals of nano-machining from the aspect of material structural effects, such as single crystalline, polycrystalline and amorphous materials. The classic MD simulations of nano-indentation and nano-cutting which have aimed to investigate the machining mechanism are discussed with respect to the effects of tool geometry, material properties and machining parameters. On nano-milling, the discussion focuses on the understanding of the grooving quality in relation to milling conditions.
This paper summarizes the results of the process optimization for SU-8 films with thicknesses 5 μm. The influence of soft-bake conditions, exposure dose and post-exposure-bake parameters on residual film stress, structural stability and lithographic resolution was investigated. Conventionally, the SU-8 is soft-baked after spin coating to remove the solvent. After the exposure, a post-exposure bake at a high temperature T PEB 90 • C is required to cross-link the resist. However, for thin SU-8 films this often results in cracking or delamination due to residual film stress. The approach of the process optimization is to keep a considerable amount of the solvent in the SU-8 before exposure to facilitate photo-acid diffusion and to increase the mobility of the monomers. The experiments demonstrate that a replacement of the soft-bake by a short solvent evaporation time at ambient temperature allows cross-linking of the thin SU-8 films even at a low T PEB = 50 • C. Fourier-transform infrared spectroscopy is used to confirm the increased cross-linking density. The low thermal stress due to the reduced T PEB and the improved structural stability result in crack-free structures and solve the issue of delamination. The knowledge of the influence of different processing parameters on the responses allows the design of optimized processes for thin SU-8 films depending on the specific application.
Direct transfer of Au nano-islands from a MoS2 stamp to an SiH surface
- J Deng
- C Troadec
- H K Kim
- C Joachim