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Micromechanical Devices with Low Friction, Wear and Corrosion Using DLC Protective Films

IP.com Disclosure Number: IPCOM000105874D
Original Publication Date: 1993-Sep-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 2 page(s) / 83K

Publishing Venue

IBM

Related People

Gambino, RJ: AUTHOR [+5]

Abstract

Micromachining using photolithographic techniques has produced a number of demonstration devices such as rotary motors, linear actuators, valves, sensors, pumps, etc. Most of these devices have been made of silicon and take advantage of the differential etching of Si and 'SiO' sub 2 or the anisotropic etching of Si. The problem with many of these devices is that they do not work reliably because of friction. The friction is sensitive to moisture so it mainly comes from the strong van der Waals bonding of hydroxyl-terminated surfaces such as Si or 'SiO' sub 2. The sliding friction between the moving parts will also cause wear which will significantly reduce the lifetime of the device.

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Micromechanical Devices with Low Friction, Wear and Corrosion Using DLC Protective Films

      Micromachining using photolithographic techniques has produced
a number of demonstration devices such as rotary motors, linear
actuators, valves, sensors, pumps, etc.  Most of these devices have
been made of silicon and take advantage of the differential etching
of Si and 'SiO' sub 2 or the anisotropic etching of Si.  The problem
with many of these devices is that they do not work reliably because
of friction.  The friction is sensitive to moisture so it mainly
comes from the strong van der Waals bonding of hydroxyl-terminated
surfaces such as Si or 'SiO' sub 2.  The sliding friction between the
moving parts will also cause wear which will significantly reduce the
lifetime of the device.  Furthermore, these devices are used in
situations where they are subjected to corrosive gases or liquids,
and because of their small size they cannot tolerate very much
corrosion and still function mechanically.

      The present invention proposes coating all contacting surfaces
with diamond-like amorphous carbon (DLC) to provide a hard,
hydrophobic, low-friction, and wear-resistance surface.  This coating
can be deposited during the fabrication of the device and is capable
of being selectively etched [1].  The same coating can be applied to
all surfaces of the device exposed to corrosive environments.  The
adhesion of DLC to silicon has been shown to be excellent [2,3].

      The following example will serve to illustrate the process used
to fabricate a DLC-coated device.  The example is an improvement on
the prior art [4] process used to make a rotary motor consisting of a
rotor on a central shaft.

1.  A silicon substrate is coated with 'SiO' sub 2 which is patterned
    and etched using a photoresist stencil and etching in buffered
    HF.

2.  DLC is deposited as a blanket coating followed by a blanket
    coating of polycrystalline Si (poly Si).  A photoresist stencil
    is used to define the washer shaped structure of the rotor
    supported on the 'SiO' sub 2.  The etching is done by Si R...