Mechanics and Tribology of MEMS Materials - prod.sandia.gov ...

Figure 6.2 Contact between an elastic sphere and a rigid flat in the presence of surface
forces: (a) the DMT model; (b) the JKR model; (c) the change in radius of
contact as a function of applied load ........................................................................54
Figure 6.3 LIGA processing produces distinct sidewall morphologies. (a) SEM image of a
microgear, (b) higher magnification micrograph showing typical texture of
sidewalls....................................................................................................................55
Figure 6.4 SEM of a LIGA Ni adhesion probe tip .....................................................................56
Figure 6.5 Typical load-displacement curves for a LIGA probe tip on a Ni LIGA disk ...........57
Figure 7.1 Surface micromachined device for quantifying friction between sidewall
surfaces. The electrostatic actuators in (a) are used to pull the movable beam in
contact with the fixed post shown in (b), and then rub the beam against the post ...60
Figure 7.2 MEMS die sitting on a flat ground in Pyrex rod, and this inside a Pyrex tube (a),
and these components inside a vial for radiation and thermal exposure in
controlled environments (b)......................................................................................62
Figure 7.3 Simulation results for thin ODTS (a) and PFTS (b) coatings at the GIF..................66
Figure 7.4 Results of XPS dose simulations, assuming a fluence of 1 Al Kα photon per
cm 2 ............................................................................................................................67
Figure 7.5 Water contact angle for Si(100) samples coated with ODTS, after exposure to
radiation (a) and heating to 300°C in various environments (b) ..............................68
Figure 7.6 Water contact angle for Si(100) samples coated with PFTS, after exposure to
radiation (a) and heating to 300°C in various environments (b) ..............................68
Figure 7.7 Detailed XPS spectra for elements present in ODTS films, normalized to
constant total intensity by element............................................................................70
Figure 7.8 Detailed XPS spectra for elements present in PFTS films, normalized to
constant total intensity by element............................................................................71
Figure 7.9 Displacement versus the square of applied voltage on oscillation actuator for asdeposited
ODTS and the same film exposed to 13%RH air at 300°C. The labels
on the displacement curves indicate the static friction coefficient, µS , calculated
based on the delay in displacement with applied voltage.........................................72
Figure 8.1 Cross section of a polycrystalline silicon (polySi) anchor on single crystal Si,
treated with selective tungsten. The silicon has been etched back to reveal the
thin layer of tungsten covering all surfaces ..............................................................76
Figure 8.2 Composition of polycrystalline surfaces treated with selective tungsten as a
function of time after deposition, while stored in a desiccator.................................77
Figure 8.3 Peak deconvolution and chemical assignments from the W 4F high resolution
XPS spectra...............................................................................................................78
Figure 8.4 Variation in the oxidation state of tungsten as a function of time after selective
tungsten deposition ...................................................................................................78
Figure 8.5 Friction coefficient versus oscillatory cycles (12 µm amplitude of sliding) for
selective tungsten coated MEMS sidewall tribometer, and a polycrystalline
silicon device treated with perfluorodecyltrichlorosilane (PFTS)............................79
Figure 8.6 Contact surfaces of selective tungsten coated sidewall tribometer after running
in air at 20% RH for 300,000 cycles. Image (a) shows the view of the post as
seen from behind the moving beam, (b) shows the wear spot on the post, and (c)
shows the corresponding contact location on the beam............................................79
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