U.S. patent application number 12/624290 was filed with the patent office on 2010-07-29 for method and apparatus for micromachines, microstructures, nanomachines and nanostructures.
This patent application is currently assigned to General Nanotechnology LLC. Invention is credited to Victor B. Kley.
Application Number | 20100192268 12/624290 |
Document ID | / |
Family ID | 26974777 |
Filed Date | 2010-07-29 |
United States Patent
Application |
20100192268 |
Kind Code |
A1 |
Kley; Victor B. |
July 29, 2010 |
Method and Apparatus for Micromachines, Microstructures,
Nanomachines and Nanostructures
Abstract
Parts and structures are described for micro and nano machines
and the creation of macro structures with nano and micro layers of
special materials to provide improved performance.
Inventors: |
Kley; Victor B.; (Berkeley,
CA) |
Correspondence
Address: |
TOWNSEND AND TOWNSEND AND CREW, LLP
TWO EMBARCADERO CENTER, EIGHTH FLOOR
SAN FRANCISCO
CA
94111-3834
US
|
Assignee: |
General Nanotechnology LLC
Berkeley
CA
|
Family ID: |
26974777 |
Appl. No.: |
12/624290 |
Filed: |
November 23, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11842031 |
Aug 20, 2007 |
7631549 |
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12624290 |
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10981142 |
Nov 3, 2004 |
7266998 |
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11842031 |
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10305776 |
Nov 26, 2002 |
6813937 |
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10981142 |
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60334181 |
Nov 28, 2001 |
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Current U.S.
Class: |
850/53 |
Current CPC
Class: |
F05C 2203/06 20130101;
F05C 2203/0882 20130101; Y10S 977/873 20130101; G01Q 70/10
20130101; F04C 2/18 20130101; Y10T 74/20582 20150115 |
Class at
Publication: |
850/53 |
International
Class: |
G01Q 70/02 20100101
G01Q070/02 |
Claims
1. A cantilever assembly suitable for use in a scanning probe
microscope (SPM) comprising a holder and a lever extending from the
holder, the lever having a first major surface, the lever further
having an end portion distal the holder, the end portion having a
recessed region formed on the first major surface, the recessed
region being suitable for receiving an object or serving as a mount
point for an object, wherein the holder includes a major surface
having at least one recessed feature formed therein, the recessed
feature having an opening that at least partially occludes an
interior region of the recessed feature.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This Application is a Continuation Application of Ser. No.
11/842,031, filed Aug. 20, 2007, which is a Divisional Application
of Ser. No. 10/981,142, filed Nov. 3, 2004, which is a Divisional
Application of U.S. Pat. No. 6,813,937, issued Nov. 9, 2004, which
claims priority from U.S. Application No. 60/334,181, filed Nov.
28, 2001 by Victor B. Kley for "Cantilever, Nano & Micro Parts,
and Diamond Knives."
[0002] This application is related to the following seven U.S.
patent applications, the disclosures of each application is
incorporated by reference in its entirety for all purposes: [0003]
U.S. Pat. No. 7,196,328, issued Mar. 27, 2007 to Victor B. Kley for
"Nanomachining Method and Apparatus;" [0004] U.S. Pat. No.
6,923,044, issued Aug. 2, 2005 to Victor B. Kley for "Active
Cantilever for Nanomachining and Metrology;" [0005] U.S. patent
application Ser. No. 10/094,411, filed Mar. 7, 2002 by Victor B.
Kley for "Methods and Apparatus for Nanolapping;" and [0006] U.S.
Pat. No. 6,880,388, issued Apr. 19, 2005 to Victor B. Kley for
"Active Cantilever for Nanomachining and Metrology."
[0007] The following U.S. patents are incorporated by reference in
their entirety for all purposes: [0008] U.S. Pat. No. 6,144,028,
issued Nov. 7, 2000 to Victor B. Kley for "Scanning Probe
Microscope Assembly and Method for Making Confocal,
Spectrophotometric, Near-Field, and Scanning Probe Measurements and
Associated Images;" [0009] U.S. Pat. No. 6,252,226, issued Jun. 26,
2001 to Victor B. Kley for "Nanometer Scale Data Storage Device and
Associated Positioning System;" [0010] U.S. Pat. No. 6,337,479,
issued Jan. 8, 2002 to Victor B. Kley for "Object Inspection and/or
Modification System and Method;" [0011] U.S. Pat. No. 6,339,217,
issued Jan. 15, 2002 to Victor B. Kley for "Scanning Probe
Microscope Assembly and Method for Making Confocal,
Spectrophotometric, Near-Field, and Scanning Probe Measurements and
Associated Images;" [0012] U.S. Pat. No. 6,752,008 issued Jun. 22,
2004 to Victor B. Kley for "Method and Apparatus for Scanning in
Scanning Probe Microscopy and Presenting Results;" [0013] U.S. Pat.
No. 6,787,768 issued Sep. 7, 2004 to Victor B. Kley and Robert T.
LoBianco for "Method and Apparatus for Tool and Tip Design for
Nanomachining and Measurement;" and [0014] U.S. Pat. No. 6,802,646
issued Oct. 12, 2004 to Victor B. Kley for "Low Friction Moving
Interfaces in Micromachines and Nanomachines."
[0015] The disclosure of the following published PCT application is
incorporated by reference in its entirety for all purposes: [0016]
WO 01/03157 (International Publication Date: Jan. 11, 2001 based on
PCT Application No. PCT/US00/18041, filed Jun. 30, 2000 by Victor
B. Kley for "Object Inspection and/or Modification System and
Method."
BACKGROUND OF THE INVENTION
[0017] [05] The present invention relates to
micro-electromechanical systems (MEMS) and to Nano
Electromechanical Systems (NEMS.TM.). In particular, the present
invention is directed to forming parts and structures for micro and
nano machines and the creation of macro structures with nano and
micro layers of special materials to provide improved
performance.
[0018] In the foregoing listed related commonly owned issued
patents and pending patent applications, various methods,
apparatus, and techniques have been disclosed relating to
micromachining and nanomachining technology. In U.S. Pat. No.
6,923,044, various cantilever configurations are discussed, along
with possible uses in the fabrication of very small machines. In
U.S. Pat. No. 7,196,328, U.S. Pat. No. 6,787,768, and U.S. patent
application Ser. No. 10/094,411, tools and techniques for
performing micro and nano scale machining operations are discussed.
In U.S. Pat. No. 6,802,646, fabrication of MEMS components using
diamond as a construction material to substantially eliminate
stiction and friction is discussed.
[0019] The foregoing are fundamental technologies and techniques
that can be used to pave the way to the world of the very small,
where structures and machines are measured at micron and nanometer
scales. What is needed are improvements to existing tools to
facilitate their manufacture and to enhance their performance.
There is a need for additional tools to facilitate the creation of
ultra-small structures. Techniques and devices are needed for
making very small mechanical components and machines such as micro
and nano gears, bearings, journals, shafts, cutters, cams,
cantilevers, pumps, simple, complex and planetary gear assemblies,
latches, locks, calculators, angle drives, propellers, linear
motion translators, unique diamond coatings arrangements for knifes
and compensatory deformation of target surfaces to use the coating
induced stress to create the final form. It is desirable to have
useful nanostructures that can be fabricated by these tools which
can then serve as building blocks for larger micromachines.
BRIEF SUMMARY OF THE INVENTION
[0020] An embodiment of a new smaller and improved cantilever MEMS
design in accordance with the present invention is provisioned with
features to facilitate the use of cantilever scanning probe
microscopy. A cantilever design in accordance with the invention
also facilitates the use tools suitable for micro- and nano-scale
operations. A mounting plate to overcome present manufacturing
limits and improve the overall yields of cantilever assemblies
useful for direct nanomachining and metrology is disclosed.
[0021] Also disclosed is a geared pump in which the components use
properties of diamond and silicon to form a simple high pressure
gear pump which is capable of moving fluids from a reservoir
chamber to and through very narrow channels and passages. Such a
pump overcomes the present limitations of silicon MEMS pumps
including their inability to develop high force (pressure) to
overcome the Van der Waals and surface forces that inhibit fluid
flow in narrow channels and passages.
[0022] In accordance with another aspect of the present invention,
a diamond coating can be used to impart a desired shape to a
substrate. Further in accordance with the invention, certain macro
uses of a diamond coating can be applied to general surfaces to
produces structures such as micro-scale knives.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] A further understanding of the nature and advantages of the
present invention may be realized by reference to the remaining
portions of the specification and the drawings:
[0024] FIG. 1 is a schematic representation of a cantilever
assembly in accordance with an aspect of the present invention,
showing a perspective view and a top view;
[0025] FIGS. 1A-1C show variations of bonding channels according to
the invention;
[0026] FIGS. 2 and 2A-2C show schematic representations of
cantilever tip variations in accordance with the present
invention;
[0027] FIGS. 3 and 3A-3C are schematic representations of
variations of the cantilever according to the invention;
[0028] FIG. 4 is a schematic representation of a cantilever
mounting plate according to the present invention;
[0029] FIG. 5 is view of the mounting plate shown in FIG. 4 taken
along view line 5-5;
[0030] FIG. 6 is a schematic representation of gear pump according
to an aspect of the present invention;
[0031] FIGS. 7A-7C are additional detailed views of the gear
assembly shown in FIG. 6;
[0032] FIG. 8 illustrate the general steps for fabricating a knife
edge in accordance with an embodiment of the invention;
[0033] FIG. 9 schematically illustrates the shaping of a substrate
according to the invention; and
[0034] FIGS. 10A and 10B illustrate different knife-edge
embodiments.
DETAILED DESCRIPTION OF THE INVENTION
[0035] FIG. 1 shows a perspective view and a top view of a
cantilever assembly 102. A main body 112 serves as a mounting
portion of the cantilever assembly. A flexural member extending
from the main body constitutes a cantilever member 104. Recessed
features 106 are formed in the main body 112 and serve as bonding
channels. In accordance with the invention, the surface area of the
cantilever assembly is no greater than three square millimeters (3
mm.sup.2).
[0036] The recessed features facilitate mounting the cantilever
assembly to an intermediate mounting plate. In a particular aspect
of the invention, the recessed features can provide reliable
permanent bonding of the cantilever assembly to a larger support
structure. Turn to FIGS. 1A-1C for a moment. The views shown in
these figures are taken along view line 1-1 in FIG. 1. These views
highlight example profiles of the recessed feature 106 according to
the invention. In FIG. 1A, a schematic representation of the
interior surface 116 of the recessed feature represents a roughened
surface. This can be formed by chemical etching or reactive ion
etching (RIE) techniques. The roughened surface provides increased
surface area and "nooks-and-crannies" to achieve a secure bonding.
For example, adhesives or solder or other flowable bonding material
can be dispensed within the recessed feature and become securely
attach to the roughened surface. This bonding system provides a
secure bond without requiring the bonding material be applied past
the top surface 114 of the main body 112, thus avoiding interfering
with the scanning probe microscopy operations.
[0037] FIG. 1B shows another variation of the recessed feature 106.
This can be formed lithographically or by other known conventional
techniques. The profile shows an opening into the recessed feature
that has a dimension (D) smaller than an interior dimension (d) in
an interior region 118 of the recessed feature. FIG. 1C shows a
similar recessed feature that might have been formed using an
isotropic etch process. In both cases the opening dimension (D) is
smaller than an interior dimension (d). Stated more generally, in
accordance with these particular embodiments of the invention, the
opening 120 of the recessed feature at least partially occludes the
interior region 118 of the recessed feature.
[0038] Returning now to FIG. 1 it can be seen that the recessed
features 106 form a contiguous T-shape. It can be appreciated that
in other embodiments, discontinuous recessed features can be
formed. The particular pattern may be determined depending on the
particular structure of the cantilever assembly, or the particular
environment of the scanning probe microscopy system.
[0039] To complete the discussion of the detail shown in FIG. 1, a
lever arm 104 extends from the main body 112. This structure is a
flexible member and constitutes the cantilever of the cantilever
assembly 102. In one embodiment of the invention, the cantilever is
integral with the main body. For example, the cantilever assembly
can be fabricated from a silicon on insulator (SOI) wafer. The
cantilever 104 can be a lithographically defined structure. It can
be appreciated, however, that the cantilever can be a separately
fabricated member that is subsequently attached to the main body
during manufacture.
[0040] FIG. 2 schematically illustrates a cantilever 104 in
accordance with an aspect of the invention. A recessed region 202
is formed into a major surface 214a of the cantilever in an end
portion of the cantilever distal the main body 112. The recessed
region can be used to as a receptacle or mount point for receiving
a secondary object. As can be seen in the profile view of FIG. 2A,
for example, the recessed region is shown as a bowl-shaped recess.
However, such shape is not necessary. The recess can be formed to
take on a shape that is suitable for a particular
implementation.
[0041] The recessed region illustrated in FIG. 2 is shown with a
circular-shaped outline. However, it can be appreciated that other
outline shapes might be more suitable for attachment of a secondary
object. The shape can be a substantially continuous form; e.g.,
elliptical, ovoid, etc. The shape can be triangular, quadrangular,
pentagonal, and in general any regular or irregular polygonal
shape.
[0042] To facilitate the attachment of a secondary object, one or
more alignment features can be formed on the surface 214a. For
example, FIG. 2 shows four such alignment features 204a-204d,
though additional or fewer features can be provided if appropriate.
The side views shown in FIGS. 2A-2C illustrate that the features
can be recessed features or raised features. For example, FIG. 2A
shows that the features 204b-204d are raised surface features.
These can be formed, for example, by properly masking the surface
of the cantilever 104 and etching away a layer of the surface,
leaving only the raised features 204b-204d and revealing the
surface 214a. FIG. 2B shows that the alignment features 204b-204d
can be recessed features. FIG. 2C shows a mixture of raised
features 204b, 204d, and recessed features 204c, illustrating that
any combination of raised or recessed alignment features can be
formed, if needed. FIG. 2C also shows a suitably formed through
hole 222 which can further facilitate attachment of a secondary
object.
[0043] FIG. 3 shows a cantilever exemplar according to another
aspect of the present invention. The cantilever 104 may have a
series of etched through passages sufficiently large to ventilate
the cantilever and thus permit easy flow of air or other gases
through the cantilever. One or more perforations 302 or openings
can be formed through the cantilever. The number, size, shape, and
arrangement of openings can vary, depending on the requirements.
For example, increasing the air flow by use of this ventilation
scheme can reduce the total air resistance can and thus improve the
Q or signal to noise ratio of the cantilever when used in resonant
SPM scan such as non-contact scanning, intermittent contact
scanning, or tapping mode scanning operations. Openings can be used
to attain a desired flexibility (spring constant) in the
cantilever. The openings may serve to reduce the mass of the
cantilever, and so on. This cantilever design can improve signal to
noise when certain Scanning Probe Microscopy methods are used in
conjunction with the cantilever such as resonant non-contact Atomic
Force Microscopy, Lateral Force Microscopy, and Magnetic Force
Microscopy.
[0044] FIG. 3A shows an opening formed through the major surfaces
214a and 214b of the cantilever. FIG. 3B shows that the first
opening 302' can be out of alignment with respect to the second
opening 302'', if a particular need requires for such a
configuration.
[0045] Incidentally, FIG. 3A shows another mixed combination of
raised and recessed alignment features 204b-204d.
[0046] Perforations 302 can be formed such that the cantilever
possesses a lattice structure. FIG. 3C shows various cantilever
structures 104a, 104b, 104c having varying patterns of openings
312, 322, 332, respectively. These cantilever exemplars illustrate
that any pattern of perforations can be provided to accommodate
particular structural or operating characteristics of the
cantilever.
[0047] Incidentally, FIG. 3C shows alternative configurations of
recessed regions and alignment features. Recessed regions 302 can
be any shape; for example, the figure shows a elongate shaped
recessed region and a diamond shaped recessed region. The recessed
region can be off-center or not. The figure shows a square-shaped
through hole 322 as an example. The alignment features 322 can be
asymmetrically arranged, or may not even be required. It can be
appreciated from the various illustrated exemplars any
configuration of recessed regions and alignment features can be
provided to accommodate a particular application.
[0048] Cantilever assemblies 102 can be fabricated on different
sized wafers. The larger wafers tend to be thicker than smaller
wafers. Standard wafer sizes include 4, 6, 8, and 12 inch wafers,
although non-standard wafers could be used. A larger wafer allows
for higher production yields of cantilever assemblies. Cantilever
assemblies with large dimensions may require a thicker substrate
than a smaller sized cantilever assembly, thus requiring the use of
thicker wafers. The result is a range of thickness dimensions when
a family of cantilever assemblies are manufactured to accommodate
different uses.
[0049] FIG. 4 shows a mounting plate 402 having a compensating
recessed region 412 formed in the plate. The compensating recessed
region can be configured to accommodate dimensional differences
among cantilever assemblies and by so doing can maintain a
pre-selected positioning of the cantilever, measured for example
from the backside of a cantilever relative to a reference.
[0050] FIGS. 5A-5C show sectional views of the mounting plate 402
taken along view line 5-5 in FIG. 4. A cantilever assembly (not
shown) can be mounted on a principal surface 502 of the mounting
plate. However, in accordance with the invention, a recess is
formed with a plurality of interior surfaces, e.g., surfaces 504,
506, and 508, configured to receive cantilever assemblies of
varying dimensions. These surfaces comprise the compensating
recessed region 412 of the mounting plate. The dimensions W.sub.1,
H.sub.1 and W.sub.2, H.sub.2 of the receiving regions defined by
the surface can be determined depending on the range of dimensions
of the cantilever assemblies to be accommodated by the mounting
plate.
[0051] For example, FIG. 5B shows a cantilever assembly 102a shown
received in the region partially defined by surfaces 506, 508 of
the mounting plate 402. The backside 214b of the cantilever 104 is
measured relative to a reference surface, R. Typically, the
measurement is made relative to a surface to be scanned. As a
matter of convention the direction of the measurement can be
considered to be in the Z-direction. The distance is shown as
Z.sub.0. FIG. 5C shows a second cantilever assembly 102b having
different dimensions. The region partially delimited by surfaces
504 has an appropriate width dimension to receive the larger
cantilever. Moreover, the depth dimension (H.sub.1) is such that
the backside 214b of the cantilever 104b has a Z-direction
measurement of Z.sub.0.
[0052] Thus in operation, the body dimensions of a cantilever
assembly can be chosen along with the dimensions of a recess in the
mounting plate 402 to place the back side of the cantilever in the
same plane (relative to the Z-direction) regardless of its overall
part thickness without affecting the overall operation of the
entire instrument. It can be appreciated further that in addition
to variations in part thickness among cantilever assemblies,
variations in the Z-direction position of the cantilever 104
relative to its main body 112 among cantilever assemblies can be
compensated for in the same manner by properly adjusting the
Z-direction dimension (H) of the corresponding receiving region.
Thus, standard wafer thicknesses such as 525 microns, 625 microns
etc. can be accommodated without affecting the interchangeability
of the instrument. It can also be appreciated that non-flat
surfaces appropriately configured and dimensioned can be used
instead of or in combination with the flat surface exemplars shown
in FIGS. 5A-5C.
[0053] FIG. 6 schematically represents an illustrative embodiment
of a high pressure gear pump MEMS according to an aspect of the
present invention. A gear drive assembly 600 provides a driving
force to actuate gears in a gear box assembly 612. In the
particular embodiment shown in the figure, the gear drive exemplar
includes a translation section comprising a plurality of expanding
members 602 arranged in a lattice-like structure. A gear rack 604
is provided at a distal end of the lattice structure.
[0054] In a particular embodiment of the invention, the fabrication
of the gear drive 600 can be fabricated as disclosed in pending
U.S. patent application Ser. No. 10/094,408. Briefly, the gear
drive can be formed on a silicon on insulator (SOI) wafer. The
upper surfaces 600a and 600c are the silicon layer spaced apart by
a layer of insulation (not shown) from an underlying substrate
600b. The lattice structure can be defined photolithographically.
An isotropic etch process applied in the regions of the expanding
members 602 can remove the underlying insulation layer thus
creating a suspended lattice structure fixed at a region A. The
silicon layer is partitioned into two zones 600a and 600c. A ground
potential can be applied to one zone (e.g., 600c) and a voltage
source V can be applied to the other zone (e.g., 600a). A return
path segment of silicon 606 provides a return path for electric
current to complete the electrical circuit from the voltage source
V to ground. The flow of current will cause thermal expansion of
the translation section (expanding members 602) due to heat
generated by the flowing current. The expansion will occur in all
directions, however, the geometry of the lattice structure will
produce a more pronounced expansion in the direction along arrow
622. Removing the current will cause the translation section to
contract as cooling occurs, again along the direction of arrow 622.
Repeated application and removal of current can produce a
reciprocal motion 622 of the gear rack 604.
[0055] A pump room 632 houses a gear assembly 612. The gear rack
604 engages the gear assembly to drive the gears (FIG. 7A) by the
reciprocating motion 622 of the translation section. A fluid
reservoir 616 provides a source of fluid which can be pumped
through a suitably formed orifice 614 in the direction F. Fluid can
be provided from an external source to the reservoir through an
inlet 618. FIG. 6 represents the orifice 614 in schematic fashion,
illustrating the principle of the fluid pump. It can be appreciated
that a suitable connection or channel can be provided to deliver
the pumped fluid to a destination.
[0056] FIG. 7A shows a cutaway view of the pump room 632 view in
the direction of view line 7-7 shown in FIG. 6. A pump casing 712
houses the gear assembly 612 in a pump chamber 714. This views
shows a portion of zone 600c of the silicon layer. The gear
assembly comprise a first gear 702a and a driven gear 702b in mesh
with the first gear. Each gear has a gear shaft 704a and 704b,
respectively which is supported on bearing journals 716 formed on
the silicon layer 600c. The gear rack 604 is shown engaging the
driven gear. The reciprocating motion 622 will cause the gears to
rotate in a reciprocating fashion. To complete the description of
the figure, the return path segment 606 is shown. The areas of
contact where the gears mesh form high pressure points, thus
defining a high pressure area 722 in that region.
[0057] FIG. 7B shows a cutaway view of the pump room 632 seen from
the top. It can be seen that portions of material in zone 600a and
zone 600c of the silicon layer serve as journal bearings 716 on
which the gear shafts 704a and 704b are supported. The journal
bearings can be round or cylindrically shaped bearing surface, or
V-shaped surfaces (e.g., 55.degree. V-shapes). The gears 702a and
702b are placed on the journals within the pump chamber 714 of the
pump room, allowing the gears to turn multiple revolutions or less
then one revolution, depending on the stroke length of the gear
rack 604. In an particular embodiment, the gears can be inserted
into journals formed in the pump chamber. The pump casing 712 can
be provisioned with opposing journals and a suitable channel to
direct the high pressure flow can be placed over the pump chamber.
It can be appreciated, however, that many other arrangements are
possible.
[0058] From the top view, it can be seen that the chamber is in
fluid connection with the reservoir 616. Walls 714a and 714b of the
chamber 714 are closely spaced from the faces 706a, 706b
respectively of gears 702a and 702b, leaving substantially only the
gear teeth being exposed to the interior volume of the chamber. A
channel 724 fluidically couples an opening 724 in the chamber 714
to the orifice 614. The channel in a given particular embodiment
can be directed as appropriate to some other suitable structure or
destination. The channel can be about 50 microns to 1 nanometer in
width.
[0059] Fluid from the reservoir is picked up by the gear teeth when
the gears rotate. The fluid is forced by the action of the gear
teeth into the high pressure area 722. The channel 724 is aligned
with respect to the high pressure area allowing the high fluid
pressure present to escape via the channel 724. The constrained
spacing between the chamber walls 714a, 714b and the gear faces
706a, 706b creates a region of high flow resistance, thus
preventing significant flow of fluid back into the chamber from the
high pressure region and ensuring a flow of fluid through the
channel. It can be appreciated that the chamber walls do not have
to extend across the entire face of the gears. In the case of a
pump, it is sufficient that a region about the chamber opening 724
is sufficiently covered as to restrict the flow fluid from the
chamber opening back to the reservoir 714.
[0060] Referring to FIGS. 6 and 7A, it another aspect of the
invention an escape mechanism (not shown) can be employed to
selectively disengage the gear rack 604 from the gear assembly 612,
for example, by moving the rack up and down (arrow 624). Thus, for
example, the gear rack can be engaged during the forward (or
reverse) stroke of the reciprocal motion and the disengaged during
the reverse (or forward) stroke. This would cause each gear to
rotate continuously in one direction. However, in the currently
shown embodiment, the pump can be effective from just the back and
forth rolling of the gears when no such escape mechanism is used.
Also it can be appreciated that alternate drive mechanisms other
than the described thermal mechanism can be used to drive the gear
assembly. For example, a suitable electrostatic comb drive, a
piezoelectric drive, or a piezoresistive drive, a rotating
electrostatic motor, and other similar devices can be used.
Incorporating an escape mechanism to produce unidirectional gear
rotation, however, can be useful in other applications.
[0061] FIG. 7C shows additional detail of the gears 702a and 702b
comprising the gear assembly 612. In accordance with a particular
embodiment of the invention, the gears are made of an obdurate low
stiction material 752 (like diamond) interacting with another
similar material or with silicon. In the particular embodiment
shown, each gear 732, 734 can be a diamond gear with integral shaft
732a, 732b fabricated using nanolapping diamond coating techniques
more fully discussed in pending U.S. patent application Ser. No.
10/094,411 and in U.S. patent application Ser. No. 10/094,149. In
accordance with the invention, each gear has a maximum surface area
less than 1 mm.sup.2.
[0062] A diamond coating can also be provided onto a substrate to
form tools. The generalized fabrication sequence shown in FIG. 8
diagrammatically illustrates a substrate 802 having a coating of
diamond 812 formed thereon. The substrate material can be titanium
(or some tungsten-based compound), titanium aluminum vanadium (or
some other titanium-based compound), silicon, tungsten or any very
low cobalt metal ceramic carbide or nitride. The diamond coating
can have a thickness of 1-20 microns. An overcoat coating 804 can
be provided on the diamond coating. The overcoat coating can be
titanium or tungsten followed by an optional bonding layer 822
(indicated by phantom lines) such as nickel and an optional
companion substrate of (typically) titanium 824 (also indicated by
phantom lines).
[0063] A diamond edge can be formed by performing a sharpening
operation on the layered structure. As the tough matrix material of
metal(s) and/or ceramic(s) is removed during the sharpening process
the thin hard diamond film, which is already sufficiently thin as
to be very sharp, is exposed for the cutting operation. The
resulting diamond edge can then serve as the leading surface used
in a cutting operation. The quality and sharpness of an edge
depends on its hardness. The diamond layer provides the material to
present a superhard edge supported by a robust matrix of tough
metal(s) and/or ceramic(s), as indicated above.
[0064] Referring to FIGS. 10A and 10B for a moment, the resulting
sandwich can result in two kinds of knife. A first knife assembly
1052 illustrated in FIG. 10A comprises a diamond layer 1014 forming
a very thin blade having a sharp edge by virtue of the diamond
layer being thin. The diamond edge can be covered by a thin (1 to 3
micron) layer of titanium and/or tungsten.
[0065] Alternatively, a second knife assembly 1054 shown in FIG.
10B comprises an optional thick substrate 1024 which can be glued
or thermally bonded to the over coated titanium and nickel layer to
form a rugged cutting edge with the diamond layer 1034. In this
particular embodiment, the diamond layer is rigidly protected in
the middle of the knife assembly by the metal layers. However, the
metal must be carefully sharpened and shaped to insure that the
diamond is properly exposed to serve as a superhard edge.
[0066] Returning to FIG. 8, if the coated substrate 802 is too thin
the diamond film may through shrinkage (or expansion) induce a
warping effect on the substrate. The substrate can be preformed to
exhibit a complementary warped shape in order to compensate for the
expected the warpage due to the diamond layer. Alternatively, the
substrate can be coated on the back of the side to provide a
reverse warping effect (bending forces in the opposite direction)
and then coated with titanium or tungsten.
[0067] Depending on the coating material and its expansion
coefficient with respect to the surface to be coated, it is
possible to selectively produce either an expansion induced warp or
a contraction induced warp. For example, suppose a non-expanding or
low-expansion rate glass is coated onto a high expansion piece of
copper at an elevated temperature T.sub.A. Then as the system
cools, the contracting copper will compress the glass and may bend
or shatter it. If the glass bond and the glass is weak enough (thin
enough) and the copper relative to the glass is strong or thick
enough, the glass may curve its edges inward toward the copper
center. In the case of diamond on silicon, a very thin layer
diamond (for example, a diamond layer a hundred times thinner than
the silicon substrate) can cause bending of the silicon toward the
center of the diamond layer as the materials cool, due to different
coefficients of expansion of diamond and silicon, and due to the
very high molecular bond strength diamond as compared to the bond
strength of silicon.
[0068] FIG. 9 schematically illustrates this aspect of the
invention with a generic "pre-shaped" substrate that is suitable
for deposition of a diamond layer to produce a desired shape (or
surface contour) while taking into account the thermal cooling
induced warping effect of diamond layer. A starting substrate
material 902 can be formed to possess a predefined shape or surface
contour. It can be understood that the pre-shaping can be performed
by any of a number of conventional techniques; e.g., machining,
grinding, chemical etching, and so on.
[0069] It is noted that the starting substrate material needs not
be pre-stressed. However, it can be appreciated that a
pre-stressing step can be performed so that when the re-shaping
takes place, the stress of the re-shaped substrate can be
compensated, either by adding more stress or reducing it as needed
for a particular application.
[0070] A diamond deposition 922 step is performed to produce a
diamond layer 912 atop the substrate. Techniques for forming a
suitable coating of diamond are known. As can be expected, the
diamond layer will stress the substrate 902 as it crystallizes,
thus pulling the pre-shaped form of the substrate 902 into a new
shape 902'. It is noted that the final shape need not be a flat
surface, though a flat surface may be desirable. It can be
appreciated that any desired surface contour can be achieved by
properly pre-shaping the starting substrate material and depositing
the diamond layer and varying its thickness to obtain a certain
degree of re-shaping effect.
[0071] It can be appreciated that additional diamond layers can be
provided to further effect shaping of the surface contour due to
the warping effect of the diamond layers. For example, a diamond
coating can be deposited on a first surface of the substrate,
followed by another diamond coating deposited on the surface
opposite the first surface, to compensate for the warping of the
first diamond layer. Selected areas on a first side of substrate
can be treated to form one or more diamond coatings at those
selected surface areas, to effect control of contour shape.
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