U.S. patent application number 13/912169 was filed with the patent office on 2014-02-20 for methods and apparatus for nanolapping.
The applicant listed for this patent is Victor B. Kley. Invention is credited to Victor B. Kley.
Application Number | 20140051333 13/912169 |
Document ID | / |
Family ID | 34437633 |
Filed Date | 2014-02-20 |
United States Patent
Application |
20140051333 |
Kind Code |
A1 |
Kley; Victor B. |
February 20, 2014 |
Methods and apparatus for nanolapping
Abstract
A lapping system for lapping portions of a workpiece. The
lapping system includes, a lap that is defined by a surface.
Portions of the surface are a lapping surface. The lapping surface
has a coating that enhances material removal from a workpiece in a
lapping process. The lapping system further includes, a scanning
probe microscope having a tip and a substrate. The scanning probe
microscope controls lapping motion of the lap and workpiece.
Inventors: |
Kley; Victor B.; (Berkeley,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kley; Victor B. |
Berkeley |
CA |
US |
|
|
Family ID: |
34437633 |
Appl. No.: |
13/912169 |
Filed: |
June 6, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12779879 |
May 13, 2010 |
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13912169 |
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11894592 |
Aug 20, 2007 |
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12779879 |
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10094411 |
Mar 7, 2002 |
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11894592 |
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12779879 |
May 13, 2010 |
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10094411 |
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11894592 |
Aug 20, 2007 |
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12779879 |
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11841698 |
Aug 20, 2007 |
8499621 |
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11894592 |
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11411985 |
Apr 25, 2006 |
7485856 |
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11841698 |
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10616453 |
Jul 8, 2003 |
7045780 |
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11411985 |
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09919780 |
Jul 31, 2001 |
6861648 |
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10616453 |
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09355072 |
Jul 21, 1999 |
6337479 |
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PCT/US98/01528 |
Jan 21, 1998 |
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09919780 |
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60274501 |
Mar 8, 2001 |
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60287677 |
Apr 30, 2001 |
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Current U.S.
Class: |
451/5 |
Current CPC
Class: |
B82Y 35/00 20130101;
G01Q 70/02 20130101; Y10S 977/86 20130101; Y10S 977/873 20130101;
Y10S 977/872 20130101; B24B 37/11 20130101 |
Class at
Publication: |
451/5 |
International
Class: |
B24B 37/11 20060101
B24B037/11 |
Claims
1. A lapping system for lapping portions of a workpiece, the system
comprising: a lap being defined by a surface, wherein portions of
the surface are a lapping surface; and wherein the lapping surface
has a coating; wherein the coating enhances material removal from a
workpiece in a lapping process; and a scanning probe microscope
having a tip and a substrate; wherein the scanning probe microscope
controls lapping motion of the lap and workpiece.
2. The lapping system of claim 1 wherein the lap is the tip and the
workpiece is the substrate.
3. The lapping system of claim 1 wherein the lap is the substrate
and the workpiece is the tip.
4-17. (canceled)
18. A lap having a lapping surface for lapping portions of a
workpiece, the lap comprising: a plurality of lap segments, wherein
each lap segment has a lapping surface; and wherein the lapping
surfaces of the lap segments are oriented to form the lapping
surface of the lap.
19-21. (canceled)
22. The lap of claim 20 wherein the lapping surface of the lap is a
track having a polygonal shape; and the track is bounded by a space
defined by a cube having edge dimensions of about 200 .mu.m or
less.
23. A method of fabricating a lap, the method comprising: cutting a
silicon wafer along the 110 crystallographic plane; etching a track
of a first shape in the silicon wafer, the track has a first
sidewall, a second sidewall, and a bottom surface, the first and
second of sidewalls being approximately perpendicular to a top
surface of the silicon wafer; cutting the silicon wafer in a
plurality of pieces; and arranging the plurality of pieces to form
the lap; wherein the lap has another track having second shape; and
the other track is a lapping surface
24. The method of claim 23 wherein the other track is bounded by a
space defined by a cube having edge dimensions of about 200 .mu.m
or less.
25-27. (canceled)
28. A lap having a lapping surface for imparting shape onto
portions of a workpiece, the lap comprising: a body; and a set of
surface portions bounding the body; wherein the lapping surface is
comprised of a subset of the surface portions; and the lapping
surface is bounded by a space defined by a space defined by a cube
having edge dimensions of about 200 .mu.m or less.
29. The lap of claim 28 and further comprising at least another
lapping surface comprised of a another subset of the surface
portions; wherein the other lapping surface is bounded by a space
defined by a cube having edge dimensions of about 200 .mu.m or
less.
30. The lap of claim 29 wherein the lapping surface forms a first
track and the other lapping surfaces forms a second track.
31-86. (canceled)
87. A lapping method for lapping portions of a workpiece, the
method comprising: controlling movement of the workpiece and a
first lap relative to each other with a scanning probe microscope;
controlling movement of the workpiece and a second lap relative to
each other with a scanning probe microscope; lapping the workpiece
into a first shape with the first lap; and lapping the workpiece
into a second shape with the second lap.
88-122. (canceled)
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/779,879, filed May 13, 2010, abandoned,
[0002] which is a continuation of U.S. patent application Ser. No.
11/894,592, filed Aug. 20, 2007, abandoned,
[0003] which is a continuation of U.S. patent application Ser. No.
10/094,411, filed Mar. 7, 2002, abandoned,
[0004] which claims priority from the following provisional
applications: [0005] U.S. Application No. 60/274,501, filed Mar. 8,
2001 by Victor B. Kley for "Scanning Probe Microscopy and
Nanomachining;" and [0006] U.S. Application No. 60/287,677, filed
Apr. 30, 2001 by Victor B. Kley for "Scanning Probe Microscopy and
Nanomachining "
[0007] U.S. patent application Ser. No. 11/894,592, filed Aug. 20,
2007, is a continuation-in-part of U.S. patent application Ser. No.
11/841,698, filed Aug. 20, 2007,
[0008] which is a continuation of U.S. patent application Ser. No.
11/411,985, filed Apr. 25, 2006, now U.S. Pat. No. 7,485,856,
[0009] which is a continuation of U.S. patent application Ser. No.
10/616,453, filed Jul. 8, 2003, now U.S. Pat. No. 7,045,780,
[0010] which is a continuation of U.S. patent application Ser. No.
09/919,780, filed Jul. 31, 2001, now U.S. Pat. No. 6,861,648,
[0011] which is a continuation of U.S. patent application Ser. No.
09/355,072, now U.S. Pat. No. 6,337,479,
[0012] which is a National Phase filing of PCT Patent Application
PCT/US98/01528, filed Jan. 21, 1998.
[0013] The disclosures of the above referenced applications are
incorporated by reference in their entirety for all purposes.
[0014] The following five U.S. patent applications were filed
concurrently with U.S. patent application Ser. No. 10/094,411 and
their disclosures are incorporated by reference in their entirety
for all purposes:
[0015] U.S. patent application Ser. No. 10/094,148, filed Mar. 7,
2002 by Victor B. Kley for "Method and Apparatus for Scanning in
Scanning Probe Microscopy and Presenting Results" now U.S. Pat. No.
6,752,008;
[0016] U.S. patent application Ser. No. 10/093,842, filed Mar. 7,
2002 by Victor B. Kley for "Nanomachining Method and Apparatus,"
now U.S. Pat. No. 7,196,328;
[0017] U.S. patent application Ser. No. 10/094,408, filed Mar. 7,
2002 by Victor B. Kley for "Active Cantilever for Nanomachining and
Metrology," now U.S. Pat. No. 6,923,044;
[0018] U.S. patent application Ser. No. 10/094,149, filed Mar. 7,
2002 by Victor B. Kley for "Low Friction Moving Interfaces in
Micromachines and Nanomachines," now U.S. Pat. No. 6,802,646;
and
[0019] U.S. patent application Ser. No. 10/093,947, filed Mar. 7,
2002 by Victor B. Kley and Robert T. LoBianco for "Method and
Apparatus for Tool and Tip Design for Nanomachining and
Measurement," now U.S. Pat. No. 6,787,768.
[0020] The disclosures of the following U.S. patents are
incorporated by reference in their entirety for all purposes:
[0021] 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";
[0022] 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"; and
[0023] 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."
[0024] The disclosure of the following published PCT application is
incorporated by reference in its entirety for all purposes:
[0025] 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
[0026] The present invention relates to the production of objects
via abrasive and/or chemical processes and more specifically
relates to the production of objects of a fine scale having a high
degree of refinement and accuracy using abrasive and/or chemical
laps.
[0027] Lapping is a process in which two objects in contact are
moved relative to one another such that the surface of one or both
is altered. A lapping process may include, for example, in the
production of a chair, the legs of the chair being shaped from a
piece of stock by a lap. A typical lap used for such a process is
sandpaper. Sandpaper typically has an abrasive material (such as
small bits of garnet crystal, ruby crystal, or aluminum oxide)
glued to its surface. To give shape to the stock and thereby turn
it into the desired chair leg, the lap is vigorously rubbed across
the surface of the stock thereby removing bits of the stock and
giving shape to the leg.
[0028] Other examples of lapping processes include the sharpening
of a knife blade with a lap. A typical lap used for such a process
is a whetstone. A whetstone is a natural or man-made stone having
an abrasive surface. The stone may have oil or water placed upon
its surface to encourage the formation of a slurry as the knife
blade is rubbed across the surface of the stone. The stone's
abrasive surface and the slurry remove bits of metal from the knife
blade as it is rubbed across the surface of the stone. If the knife
and stone are held a an appropriate angle as the knife is rubbed
against the stone, the knife will become sharpened.
[0029] The above described lapping processes work well in the
macroscopic realm. One may simply pick up a lap with one's hands
and give shape to an object with the lap. However, in the
microscopic realm, picking up a lap and giving shape to an object
with the lap is not as simple as taking a piece of sandpaper in
hand to lap a chair leg or using a whetstone lap a knife blade.
Accordingly, new lapping techniques and apparatus are desired to
shape objects in the microscopic realm.
[0030] 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.
BRIEF SUMMARY OF THE INVENTION
[0031] In accordance with the invention nanolapping methods and
apparatus include components for lapping shapes in portions of a
workpiece. In one aspect of the embodiments of the invention a
scanning probe microscope controls the relative lapping motion of a
lap and workpiece. In another aspect of the invention, laps are
fabricated from silicon wafers cut along the 100 crystallographic
plane. In another aspect of the invention, laps are fabricated from
silicon wafers cut along the 110 crystallographic plane. In still
another aspect of the invention, laps are coated with abrasive or
chemical reagents to enhance material removal from a workpiece in a
lapping process. In still yet another aspect of embodiments of the
invention, scanning techniques are provided to produce scan data
relating to a scanning tip.
[0032] 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.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] FIGS. 1A are 1B are schematic top and cross-sectional views
of a lap according to an embodiment of the present invention;
[0034] FIG. 1C is a schematic cross-sectional view of a lap
according to an embodiment of the present invention;
[0035] FIGS. 2A, 2B, and 2C show an example of a nanolapping
process according to an embodiment of the invention;
[0036] FIGS. 2D, 2E, and 2F show another example of a nanolapping
process according to another embodiment of the present
invention;
[0037] FIG. 2G shows a lap and a workpiece at an angular position
other than perpendicular;
[0038] FIG. 3A is a bottom view of a workpiece having an octagonal
shape;
[0039] FIG. 3B is a side view of the workpiece;
[0040] FIGS. 4A and 4B are schematic top and cross-sectional views
of lap according to an embodiment of the present invention;
[0041] FIG. 4C is a schematic cross-sectional view of a square lap
having tracks protruding above a top surface of a substrate
according to an embodiment of the present invention;
[0042] FIG. 4D shows a bottom view of a workpiece having a square
profile adopted by the workpiece subsequent to nanolapping along
the tracks of the lap of FIG. 4A or 4B;
[0043] FIGS. 5A and 5B are schematic top and cross-sectional views
of a lap having tracks of elliptical shape according to an
embodiment of the present invention;
[0044] FIG. 5C is a schematic cross-sectional view of a lap
according to an embodiment of the present invention;
[0045] FIG. 5D is a schematic bottom view of a workpiece having an
elliptical profile;
[0046] FIGS. 6A and 6B are cross-sectional views of two laps, each
having tracks with curved sidewalls and a relatively flat bottom
surface;
[0047] FIGS. 6C and 6D are cross-sectional views of two laps, each
having tracks with sidewalls that are relatively flat with bottom
surfaces that are curved;
[0048] FIG. 6E is a cross-sectional view of a lap having tracks
each having a top surface that is curved;
[0049] FIGS. 7A and 7B are schematic side and perspective views,
respectively, of a lap according to an embodiment of the
invention;
[0050] FIGS. 8A, 8B, and 8C are schematic side, perspective, and
top views, respectively, of a lap according to another embodiment
of the present invention;
[0051] FIG. 9 is a side view of a lap according to another
embodiment of the present invention;
[0052] FIGS. 10A, 10B, and 10C are schematic side, perspective, and
top views, respectively, of a lap according to an embodiment of the
present invention;
[0053] FIG. 10D shows a lap that may be rotationally and
transversely moved with respect to a doweled shape workpiece to
impart a thread type pattern onto the workpiece;
[0054] FIGS. 11A, 11B, and 11C are schematic side, bottom, and
perspective views, respectively, of a lap according to an
embodiment of the present invention;
[0055] FIGS. 11D and 11E are schematic side and bottom views,
respectively, of a lap according to another embodiment of the
present invention;
[0056] FIGS. 12A and 12B are schematic top and cross-sectional
views, respectively, of a lap made from a silicon wafer cut along
the 110 plane according to an embodiment of the present
invention;
[0057] FIG. 13A is a schematic top view of a lap having a hexagonal
track according to an embodiment of the present invention;
[0058] FIGS. 13B and 13C are a schematic top and side views of a
lap indicating locations at which the lap may be cut to form lap
segments that are arranged to form other laps;
[0059] FIG. 13D is a schematic top view of a lap segment;
[0060] FIGS. 14A and 14B are schematic top and cross-sectional
views of a lap having a hexagonal track according to an embodiment
of the present invention;
[0061] FIGS. 14C and 14D are a schematic top and side views of a
lap indicating locations at which the lap may be cut to form lap
segments that are arranged to form other laps;
[0062] FIG. 15 shows a nanolapping path of a workpiece around a
square lap according to an embodiment of the present invention;
[0063] FIG. 16 shows a nanolapping path of a workpiece around a
defect in the edge of a lap according to an embodiment of the
present invention;
[0064] FIG. 17 is a gross-scale cross-sectional side view of a
workpiece and a reference surface;
[0065] FIG. 18 is a flow chart highlighting the steps for
nanomeasurements in accordance with an embodiment of the present
invention;
[0066] FIGS. 19A and 19B are side views of a workpiece and a
reference surface;
[0067] FIG. 20 is a side view of a reference surface illustrating a
sampling of reference structures;
[0068] FIG. 21 is a flow chart highlighting feedback processing for
nanolapping in accordance with an embodiment of the present
invention; and
[0069] FIG. 22 is a schematic view of a scanning probe microscopy
system according to an embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Introduction
[0070] The following description sets forth lapping apparatus and
lapping methods according to embodiments of the invention.
Embodiments of the invention are used as either a tip or substrate
in a scanning probe microscope (SPM) to lap and thereby give shape
to portions of a workpiece.
[0071] The general functionality of the present invention is to
produce objects via abrasive and/or chemical operations and more
specifically to produce objects via abrasive and/or chemical
nanolapping. Most of the discussion will be with reference to lap
embodiments having a body with a surface, some or all portions of
the surface being a lapping surface. Alternatively, a body may have
surface portions providing multiple lapping surfaces. A lapping
surface, as referred to herein, is a contiguous set of surface
portions used to lap a workpiece. A lap body, also referred to
simply as a lap, may have surface portions that are polygonal,
curved, or combinations thereof. Further, the body may have surface
portions that protrude from or recessed into other surface
portions. Protruding and recessed surface portions may have further
surface portions, some or all of which are a lapping surface.
[0072] Surface portions of a body that form a lapping surface may
be relatively small. For example, the maximum lateral expanse of a
lapping surface along any given axis may be about 200 .mu.m or
less. Further, the volume defined by a three-dimensional lapping
surface will typically fit within a cubical space having dimensions
of about 200 .mu.m on a side or less. However, according to other
embodiments, a lapping surface may be relatively large, for
example, the maximum lateral expanse of a lapping surface along any
given axis may be more than 200 .mu.m, for example, 1 mm or more. A
body having a lapping surface is used in combination with a device
having relatively fine position control (e.g., a scanning probe
microscope), to provide very refined nanolapping of a workpiece,
(e.g., atomic level precision). Workpieces are also referred to as
"target objects," and "tools." A typical scanning probe microscope
provides for control of motion from the nanometer range down to the
angstrom level and below. Such fine control of motion provides for
very fine detail (e.g., atomic level detail) to be nanolapped onto
a workpiece. Whether a lap is relatively large, for example, larger
than a few millimeters, or relatively small, for example, smaller
than 5 .mu.m, workpieces of these scales may be nanolapped with the
aforementioned levels of precision.
[0073] Scanning probe microscopy (SPM) has been put to successful
use in the imaging of objects not otherwise resolvable by classical
optics techniques. Various SPM techniques, such as scanning
electron microscopy, scanning tunneling microscopy, and atomic
force microscopy have provided images down to the atomic level.
Further, SPM techniques have been used with some success in
manipulating objects at the atomic level. For example, individual
atoms of iron have been moved about on a substrate to create
letters that are tens of angstroms in height and width. While
creating letters and spelling out words in iron atoms is of limited
practicality, such atomic level manipulations provide an impetus to
create useful devices using SPM techniques.
[0074] Of greater utility than the creation of atomic scale
letters, is, for example, the creation of microscopic machines and
tools. For example, the creation of tools and machines having
dimensions of say, less than or equal to about 200 .mu.m along any
given axis, provide utility where other larger devices fail. For
example, microscopic mechanical memories may be of use in
environments, such as space, in which semiconductor based devices
have high fault rates due to high-energy cosmic radiation. Further,
microscopic mechanical machines may be of surgical use, reaching
areas of the body not otherwise accessible or manipulable by
traditional surgical tools and techniques. Methods and apparatus of
the present invention are directed toward such problems as well as
others and are described in detail below.
Embodiments with Polygonal and Curved Tracks
[0075] FIGS. 1A and 1B are schematic top and side views of a lap
100 according to a specific embodiment of the present invention.
Lap 100 is formed from a substrate 120 having various contours
formed therein. Lap 100 has a surface with octagonal tracks 105 and
110 formed as recesses in the surface below an upper surface 125.
Surface portions forming tracks 105 and 110 are variously
identified. Each track has eight segments, and certain features
will be denoted with a base reference numeral and an alphabetic
suffix "a-h" denoting the segment. Each of the tracks is shown as
having two sidewalls (denoted with base reference numerals 130 and
132) and a bottom surface 134. Thus outer sidewall 130 includes
sidewall segments 130a-130h, with segments 130a and 130e shown in
FIG. 1B. Similarly, inner sidewall 132 has sidewall segments
132a-132h, with segments 132a and 132e shown in FIG. 1B.
[0076] For consistency and clarity, a particular coordinate system
will be shown and referred to. FIG. 1A is considered to lie in the
x-y plane, and the z-axis will be considered to extend out of the
page. In accordance with standard symbology, an axis extending out
of the page will be denoted by a dot in a circle while an axis
extending into the page will be denoted by a + in a circle. The top
view of FIG. 1A thus shows lap 100 extending laterally in the x-y
plane, and the cross-sectional view (FIG. 1B) taken along line
1B-1B of FIG. 1A extends in the x-z plane. In most instances,
references to direction and orientation that mention an axis (e.g.,
the x-axis) or a plane (e.g., the x-y plane) should be considered
to include lines parallel to that axis, or planes parallel to that
plane.
[0077] The lapping surface of lap 100 may variously include, one or
more of tracks 105, 110, and all or portions of surface 125.
Typically, the dimensions of a lapping surface is set according to
a particular lapping to be achieved. For example, the height of
sidewall segments 130a-130h and 132a-130h (measured between top
surface 125 and bottom surface 134) are equal to about 200 .mu.m or
less. In accordance with various embodiments of the invention, the
height of the sidewall segments may be on the order of about 100
.mu.m or less, about 75 .mu.m or less, about 60 .mu.m or less,
about 50 .mu.m or less, or about 10 .mu.m or less. According to
other embodiments of the present invention, the height of the
sidewalls is about 1 .mu.m and the width of bottom surface is about
2 .mu.m to 4 .mu.m. However, according to other embodiment, a
lapping surface may be relatively large, for example, the height of
the sidewall segments may be greater than 200 .mu.m, for example, 1
mm or more.
[0078] To achieve a lapping result, a workpiece is shaped by
nanolapping, (i.e., rubbing the workpiece against the lapping
surface of the lap). As the workpiece is rubbed against the lapping
surface of the lap, material is removed from the workpiece. The
removal of material from the workpiece imparts the contour of a
lapping surface to the workpiece. For example, a workpiece 135 may
first be rubbed against outer sidewalls 130a, giving shape to one
side of the workpiece and then the workpiece may be rubbed against
inner sidewall 132a, giving shape to another side of the workpiece.
A workpiece may also be rubbed against bottom surface 134 to give
shape to the bottom of the workpiece.
[0079] Typically, the angles between the sidewalls and the bottom
surface are also set according to a particular lapping to be
achieved. The angles between the outer sidewalls 130a-130h and the
bottom surface are approximately equal as are the angles between
the inner sidewalls 132a-132h and the bottom surface. Each of the
angles may be in the range of less than 180.degree. to less than
1.degree.. According to a specific embodiment, the angles between
the outer sidewalls and the bottom surface are about 70.degree. and
the angles between the inner sidewalls and the bottom surface are
about 93.degree.. FIG. 1B shows a cross-sectional view of lap 100
revealing four of these angles designated 137a, 139a, 139e, and
137e. According to the specific embodiment, angles 137a and 137e
are each about 93.degree. and angles 139a and 139e are each about
70.degree.. Other cross-sectional views of trenches 105 and 110
would reveal similar angular relationships for the other outer and
inner sidewalls and the bottom surface.
[0080] The tracks 105 and 110 are shown as recessed below top
surface 125. Other track configurations of the present invention
protrude from the surface of the substrate. For example, FIG. 1C
shows a cross-sectional view of an octagonal lap 100' having tracks
105' and 110' with surface portions protuberating above a top
surface 125' of a substrate 120. A top view of lap 100' is
essentially the same as that shown in FIG. 1A. Similar to lap 100,
the lapping surface of lap 100' may include, for example, the
surface portions of tracks 105' and 110' and possibly all or
portions of top surface 125'.
[0081] FIGS. 2A, 2B, and 2C show an example of a time-ordered
sequence of a lapping process according to an embodiment of the
invention. Workpiece 135 lapped against lap 100 is shown at various
steps of a lapping process. The direction of rubbing is
perpendicular to the plane of the page, i.e., along the y-axis. As
the workpiece is successively rubbed in a side-to-side motion
against outer sidewall 130a, bottom surface 134, and top surface
125, the shape of the workpiece is altered. Workpiece 135 is shown
to assume the contour of the surface portions as the workpiece is
rubbed. For example, if angle 137a between outer sidewall 130a and
bottom surface 134 is 70.degree., then the interior angle 140 of
workpiece 135 will also be 70.degree..
[0082] FIGS. 2D, 2E, and 2F show another example of a time-ordered
sequence of a lapping process according to an embodiment of the
invention. Similar to the example shown in FIGS. 2A-2C, FIGS. 2D-2F
show various steps of a lapping process as the steps may appear at
various points of time. Workpiece 135 is rubbed in a side-to-side
motion along sidewalls segment 132a and bottom surface 134. The
workpiece assumes the contour of the surface portions as is it
lapped. For example, if angle 139a between edges 132a and 134 is
93.degree., then interior angle 142 of the workpiece will be
93.degree..
[0083] FIGS. 2A-2F show lap 100 positioned approximately
perpendicular to workpiece 135. However, according to embodiments
of the present invention, laps and workpieces may be set at a
variety of angles with respect to each other. For example, FIG. 2G
shows lap 100 and a workpiece 135 at an angular position other than
perpendicular. Either the lap or the workpiece may be rotated to
achieve this position. As laps and workpieces may be set at a
variety of angles with respect to each other, a single lap may be
used to impart a further variety of profiles onto a workpiece other
than that achieved for relatively perpendicular positioning.
[0084] As described above, the lapping direction shown in each of
FIGS. 2A-2G is along a y-axis of the lap. However, according to the
present invention, nanolapping is not limited to one axis of a lap.
Nanolapping may be along each of the x, y, and z-axes or along
combinations thereof. For example, referring again to FIG. 1A,
workpiece 135 may be lapped against each of sidewall segments
130a-h and top surface 125. As workpiece 135 is lapped against
sidewall segments 130a-h and top surface 125, the workpiece will
assume not only the angular profile shown in FIGS. 2A-2C, but also
the octagonal shape of track 105. FIG. 3A is a bottom view of
workpiece 135 having an octagonal shape assumed by the workpiece
after to being lapped against each of sidewall segments 130a-h.
FIG. 3B is a cross-sectional view of workpiece 135 taken through
line 3B-3B of FIG. 3A. Each of the eight bottom edges of the
workpiece will have interior angles 140 (two of which are shown in
FIG. 3B) that correspond to the angles between sidewall segments
130a-h and bottom surface 134.
[0085] FIGS. 4A and 4B are schematic top and cross-sectional views,
respectively, of a lap 400 according to another embodiment of the
present invention. A similar reference numeral scheme will be used
as that of FIGS. 1A-1C. This embodiment differs from the embodiment
of FIGS. 1A-1C in that it has square tracks 405 and 410 recessed in
a substrate 120 having a top surface 425.
[0086] Each track has an outer sidewall 430 and an inner sidewall
432. Each sidewall has four segments that include sidewall segments
430a-430d and sidewall segments 432a-432f. The cross-sectional view
shown in FIG. 4B taken along line 4B-4B show sidewall segments 430a
and 430c and sidewall segments 432a and 432c. The lapping surface
may include, for example, the sidewalls and bottom surfaces or the
sidewalls and bottom surfaces and all or portions of top surface
425.
[0087] Lap 400 has similar dimensions as that of lap 100. For
example, the height of sidewall segments 430a-430d and 432a-430d
(measured between top surface 425 and bottom surface 434) may be
equal to about 200 .mu.m or less. In accordance with various
embodiments of the invention, the height of the sidewall segments
may be on the order of about 100 .mu.m or less, about 75 .mu.m or
less, about 60 .mu.m or less, about 50 .mu.m or less, or about 10
.mu.m or less. According to other embodiments of the present
invention, the height of the sidewalls is about 1 .mu.m to 2 .mu.m
and the width of bottom surface is about 2 .mu.m to 4 .mu.m.
Alternatively, the height of the sidewall segments may be greater
than about 200 .mu.m to provide nanolapping for relatively larger
workpieces. Additionally, the angles between sidewall segments
430a-430b and bottom surface 434 and the angles between sidewall
segments 432a-432f and bottom surface 434 may range from less than
180.degree. to less than 1.degree.. According to a specific
embodiment, angles between sidewall segments 430a-430d and bottom
surface 434 are each about 70.degree. and angles between sidewall
segments 432a-432d and bottom surface 434 are each about
93.degree..
[0088] Tracks 405 and 410 are shown as recessed below top surface
425. Other track configurations of the present invention protrude
from the surface of the substrate. For example, FIG. 4C is a
schematic cross-sectional view of a square lap 400' having tracks
405' and 410' with surface portions protruding above a top surface
425' of a substrate 120. A top view of lap 400' is essentially the
same as that shown in FIG. 4A. Similar to lap 100, the lapping
surface of lap 400' may include, for example, the surface portions
of tracks 405' and 410' and possibly all or portions of top surface
425'.
[0089] According to methods of the present invention, laps 400 and
400' are used to produce workpieces having angled shapes such as
square or rectangular shapes. For example, rubbing a workpiece 435
along sidewall segments 430a-430d will produce a workpiece having a
square or rectangular profile as viewed from the bottom of the
workpiece. A square profile is typically achieved by nanolapping a
workpiece an equal number of times against each of the sidewall
segments. FIG. 4D shows a bottom view of a workpiece 435 having a
square profile adopted by the workpiece subsequent to nanolapping
along the tracks of lap 400 or 400'. A rectangular shaped workpiece
can be formed typically by nanolapping the workpiece, for example,
along sidewall segment 430a and 430c more than along sidewall
segment 430b and 430d. However, some workpieces shaped by
nanolapping may have nonuniform hardness. In other words, the
hardness of the workpiece varies along different axes the
workpiece. Accordingly, to lap a workpiece into a square profile,
more rubbing is performed along relatively harder sides than along
relatively softer sides. For example, diamond has hardnesses that
vary substantially along different crystal axes. Given surface
portions of diamond are as much as 10-100 times harder than other
crystal surface portions. Accordingly, nanolapping a diamond
workpiece into a square may require 10-100 more lapping strokes
along some surface portions than along other surface portions.
[0090] According to another method of the present invention, a lap
is used to locate the relatively harder and softer sides of a
workpiece. According to the method, a workpiece having a known
shape is rubbed against a lapping surface. The known shape is
compared to the shape of the workpiece after having been lapped.
The sides of the workpiece exhibiting the greatest amount of
material removal (i.e., wear) are the relatively softer sides. The
sides of the workpiece exhibiting the least amount of material
removal are the relatively harder sides. For example, a 100 cut
diamond workpiece has four or eight hard directions depending on
the orientation of the diamond. The 100 cut diamond workpiece
having a known shape is rubbed against a lapping surface and
compared to the known shape of the prelapped diamond workpiece. The
four or eight hard sides of the diamond are then identified as
those exhibiting the least amount of material removal while the
softer sides of the diamond workpiece are identified as those sides
exhibiting the most amount of material removal.
[0091] FIGS. 5A and 5B are schematic top and cross-sectional views,
respectively, of a lap 500 according to another embodiment of the
present invention. This embodiment differs from the embodiment of
FIGS. 1A-1C in that it has elliptical tracks 505 and 510 recessed
in a substrate 120 having an upper surface 525. This embodiment is
one example of laps having generally curved shaped lapping
surface.
[0092] Similar to laps shown in FIGS. 1B and 2B, the tracks of lap
500 are recessed below top surface 525 of substrate 520. Unlike the
laps shown in FIGS. 1A and 2A, each track has a single segment that
includes a single outer sidewall and a single inner sidewall in
addition to a bottom surface. For example, track 505 has a single
outer sidewall denoted 530, a single inner sidewall denoted 532,
and a bottom surface 534. Lap 500 has similar dimensions to those
of lap 100. FIG. 5B shows outer sidewall 530 and inner sidewall 532
in a cross-sectional view taken along line 5B-5B of FIG. 5A.
[0093] Tracks 505 and 510 are shown as recessed below top surface
525. Other track configurations of the present invention protrude
from the surface of the substrate. For example, FIG. 5C shows a
cross-sectional view of an elliptical lap 500' having tracks 505'
and 510' with surface portions protuberating above a top surface
525' of a substrate 120. A top view of lap 500' is essentially the
same as that shown in FIG. 5A. Similar to lap 100, the lapping
surface of lap 500' may include, for example, surface portion of
tracks 505' and 510' and possibly all or portions of top surface
525'.
[0094] According to methods of the present invention, laps 500 and
500' are used to produce workpieces having curved shapes such as
elliptical shapes or other round shapes. For example, rubbing a
workpiece 535 along outer sidewall 530 will produce a workpiece
having an elliptical profile as viewed from the bottom of the
workpiece. FIG. 5D shows a bottom of view of a workpiece 535 having
an elliptical profile adopted by the workpiece subsequent to
nanolapping along one of the tracks of lap 500 or 500'.
[0095] The lap embodiments described above are shown as having
tracks having octagonal, square, and elliptical shapes. However,
according to other embodiments of the present invention, a lap may
have tracks of generally arbitrary shapes, including other
polygonal shape (e.g., heptagonal) or curved shape (e.g.,
circular). Alternatively, a lap may have a combination of straight
and curved sections. For example, a track may be generally square,
such as lap 400A, however the corners of the lap may be
rounded.
[0096] Laps 100, 400, and 500 (FIGS. 1, 4, and 5) each have two
tracks. Laps according to the present invention may have laps with
fewer or more than two tracks. For example, lap 100 instead of
having two octagonal tracks 105 and 110, may have six, seven, or
more tracks. Laps having numerous tracks provide for greater lap
wear. For example, if one track becomes worn, another track may be
used. Further, laps having numerous tracks of different sizes, such
as tracks 105 and 110 of lap 100, may be used in a greater variety
of SPMs having different ranges of motion. This will be discussed
in further detail below. Further yet, fabricating a lap having
multiple tracks does not introduce significant manufacturing costs
above and beyond a lap having a single track. This also will be
discussed in further detail below.
[0097] Laps 100, 400, and 500 (FIGS. 1, 4, and 5) each have two
tracks that are similarly shaped. However, the present invention
provides laps having tracks of different shapes. For example, a lap
may have a square track nested in or alongside an elliptical track.
Providing tracks with different shapes provides a larger number of
shapes that can be imparted onto a workpiece than a lap having
tracks of a single shape.
[0098] FIGS. 6A and 6B are cross-sectional views of laps 600a and
600b, respectively, according to embodiments of the present
invention. Lap 600a has tracks 605a and 610a, each with convex
sidewalls 620a and relatively flat bottom surfaces 624a. Lap 600b
has tracks 605b and 610b each with concave sidewalls 620b and
relatively flat bottom surfaces 624b. The laps described above have
tracks with relatively flat bottom surfaces, however, laps of the
present invention are not limited to having relatively flat
bottoms.
[0099] FIGS. 6C and FIG. 6D are cross-sectional views of laps 600c
and 600d, respectively, according to embodiments of the present
invention. Lap 600c has tracks 605c and 610c, each with relatively
flat sidewalls 620c and concave bottom surfaces 624c. Lap 600d has
tracks 605d and 610d each with relatively flat sidewalls 620d and
convex bottom surfaces 624d.
[0100] FIG. 6E shows a cross-sectional view of a lap 600e according
to an embodiment of the present invention. Lap 600e has tracks 605e
and 610e each protruding above top surface 625e. The top surfaces
628e of each of the tracks 605e and 610e have concave surfaces. The
sidewalls 622e are relatively flat.
[0101] While a top view of laps 600a-600e is not shown, the
profiles of the tracks from a top view, may include any of the
profiles discussed above, such as polygonal, round, or combinations
thereof. Each of the tracks 605a-605e and 610a-610e are shown to
have relatively flat surface portions and curved surface portions,
but it should be understood, the tracks may have all curved surface
portions, or other combinations of curved and straight surface
portions.
Embodiments with Polygonal and Curved Surface Portions
[0102] FIGS. 7A and 7B are schematic side and perspective views,
respectively, of a lap 700 according to an embodiment of the
invention. Lap 700 is a right solid. In other words, the various
surface portions of the lap meet at right angles. Each of sidewalls
710, 712, 714, and 716 is perpendicular to top surface 720 and
bottom surface 722 and perpendicular to its adjacent sidewalls. All
surface potions of lap 700 may be portions of a lapping surface or
selected surface portions may be portions of a lapping surface. For
example, sidewalls 710, 712, 714, and 716 may collectively
constitute a lapping surface or the sidewalls and the top surface
may constitute a lapping surface.
[0103] Typically, the heights of the sidewalls are set according to
a given lapping process to be achieved, for example, the height of
the sidewalls may be in the range of about 200 .mu.m to about 0.25
.mu.m. According to a specific embodiment the sidewall heights are
about 17 .mu.m. However, according to other embodiments, the
sidewall heights may be larger, for example greater than about 200
.mu.m for nanolapping relatively larger workpieces. A workpiece may
be shaped by lap 700 either by rubbing the workpiece in an
up-and-down motion along a sidewall or side-to-side along a
sidewall. Rubbing the workpiece against a sidewall of the lap
transfers the profile of the lap to the workpiece. The top and
bottom surfaces may also be a lapping surface. A workpiece lapped
along a sidewall and say the top surface of the lap will assume not
only the sidewall profile but will also assume the profile of the
top surface and the edge joining these lapping surface
portions.
[0104] As previously discussed, the sidewalls of lap 700 are
perpendicular to top and bottom surfaces 720 and 722, respectively,
and to adjacent sidewalls, but it should be understood that laps
according to the present invention may have other useful
geometries. For example, the interior angles 740, 742, 744, and 746
of top surface 720 may be a variety of angles other than
90.degree.. According to embodiments of the present invention, the
interior angles may range from acute angles of about 1.degree. or
less to angles approaching 180.degree.. For example, according to a
specific embodiment of the present invention, angles 740 and 744
are each about 60.degree. and angles 742 and 746 are each about
120.degree..
[0105] FIGS. 8A, 8B, and 8C are schematic side, perspective, and
top views, respectively, of a lap 800 according to another
embodiment of the present invention. The surface portions of lap
800 include four sidewalls 810, 812, 814, 816, top surface 820, and
bottom surface 822. Each of the sidewalls and/or top surface and/or
bottom surface may be a portion of the lap's lapping surface. The
sidewalls are each beveled with respect to their adjacent
sidewalls. Each sidewall is also beveled with respect to the top
and bottom surfaces. According to embodiments of the present
invention, the sidewall height (i.e., distance between the top and
bottom surfaces) may be from about 200 .mu.m to about 0.25 .mu.m.
According to a specific embodiment of the invention, the sidewall
height is about 17 .mu.m. Each of the interior angles 840, 842,
844, and 846 of the top surface is set according to a lapping
result to be achieved. According to embodiments of the present
invention, the interior angles may range from acute angles of about
1.degree. or less to obtuse angles approaching 180.degree..
According to a specific embodiment of the present invention, angles
840 and 844 are each about 60.degree. and angles 842 and 846 are
each about 120.degree..
[0106] The relative lapping motion between a workpiece and a
lapping surface may be in the up-and-down direction (indicated by
double-headed arrow 870) along sidewalls 810, 812, 814, and 816, or
may be side-to-side (indicated by double-headed arrow 872) along
the sidewall and/or top and/or bottom surfaces 820 and 822,
respectively. Further, lapping motions can be a combination of
up-and-down and side-to-side motions. A workpiece rubbed against
the sidewall portions of the lap surface will adopt the sidewall
profile, for example a beveled lapping surface will produce a bevel
on the workpiece. A workpiece rubbed successively along each of the
sidewalls of the lap will adopt not only the beveled profile of the
sidewalls, but also the polygonal shape of the top and bottom
surfaces. A workpiece rubbed against a sidewall and, for example,
the top surface of the lap will adopt the shape of the sidewall and
top surface. FIG. 8A shows a workpiece 735 having adopted the
profile of sidewall 810 and top surface 820.
[0107] A workpiece may also be lapped against adjacent sidewalls of
lap 800, for example sidewalls 812 and 814. FIG. 8C shows a
workpiece 874 having adopted the profile of sidewalls 812 and 814.
Successively rubbing sidewall 810 and 812 at radial increments
about a center of the workpiece 874 may form, for example, a simple
gear shape, as shown in FIG. 8C. A gear shape may be lapped onto
various portions of a workpiece, for example, section 760 of
workpiece 735 may have a gear shaped lapped thereon.
[0108] While laps 700 and 800 are shown to have four sidewalls and
a top and bottom surface, other polygonal shaped laps may be of
use. For example, according to embodiments of the present
invention, laps may have sidewalls and/or top and bottom surfaces
of triangular, pentagonal, or other polygonal shapes.
[0109] FIG. 9 is a side view of a lap 900 according to another
embodiment of the present invention. Lap 900 has a stepped
pyramidal surface profile. The surface portions forming the stepped
pyramidal feature include, sidewalls 905, 910, 920, 925, and 930
that provide the vertical components of the stepped shape and top
surfaces 907, 912, 922, 927, 932 and bottom surface 940 that
provide the horizontal components of the stepped shape. Lap 900
provides several surface and edge profiles, for example, acute
angle 960, right angle 965, obtuse angle 970, and rounded edge 975.
The various lapping surface profiles of lap 900 reduce the number
of laps required to build up a complex profile on a workpiece. For
example, referring to FIGS. 7A and 8A, workpiece 735 is shown to
have profiles imparted from both lap 700 and lap 800. For example,
a bottom section 760 of workpiece 735 is shaped by lap 700, while a
middle section 762 of the workpiece is shaped by lap 800. However,
lap 900 can be used to provide both the bottom and middle profiles
by positioning workpiece 735 at various positions with respect to
lap 900 during different stages of a lapping operation.
Rotational Laps
[0110] FIGS. 10A, 10B, and 10C are schematic side, perspective, and
top views, respectively, of a lap 1000 according to an embodiment
of the present invention. Lap 1000 has top and bottom surfaces 1006
and 1008, and sidewalls 1010 and 1015 joined by a rounded surface
1020. The lapping surface of lap 1000 may include, for example,
portions or all of the sidewalls and/or rounded surface and/or top
surface and/or bottom surface. Lap 1000 is of use to impart curves
or other shapes to a workpiece 1035. For example, a curved surface
may be imparted to a workpiece 1035 by moving the workpiece up and
down as indicated by the double-headed arrow 1040. Alternatively, a
curved shape may be imparted to workpiece 1035 by rotating the lap
with respect to the workpiece as indicated by double-headed arrow
1045. Other lapping motions may also be of use, for example,
combinations of rotational and up and down motions. For example,
lap 1000 may be rotationally and transversely moved with respect to
a dowel-shaped workpiece 1060 to impart a thread pattern to the
workpiece as shown in FIG. 10D.
[0111] FIGS. 11A, 11B, and 11C are schematic side, bottom, and
perspective views, respectively, of a lap 1100 according to an
embodiment of the present invention. Lap 1100 has a cylindrical
shape that includes a sidewall 1110 and a bottom surface 1115. As
shown, the sidewall and bottom surfaces are perpendicular to each
other. Lap 1100 is deployable in a variety of ways to give shape to
a workpiece. FIG. 11C shows a number of techniques for shaping a
workpiece 1135 with lap 1100. For example, the right portion of
FIG. 11C shows lap 1100 to have a rotational degree of motion as
indicated by dash arrow 1140. Bottom surface 1115, while in
rotational lapping contact with workpiece 1135 will lap a circular
recess in the surface of the workpiece. Slowly lowering the lap
into the recess will further deepen the recess resulting in a hole,
indicated by dashed lines 1160.
[0112] Sidewall 1110 may also be used to lap a workpiece. For
example, the left side of FIG. 11C shows sidewall 1110 in lapping
contact with sidewall 1170. In such a configuration, the lap may be
variously manipulated to lap the workpiece 1135. For example, the
lap may be in rotational contact with the workpiece or the lap may
be moved up and down with respect to the workpiece, as indicated by
double-headed arrow 1152. Additionally, the lap may be swept
side-to-side across sidewall 1170 of the workpiece as indicated by
double-headed arrow 1157. Or, the lap may be in lapping contact
through a combination of the aforementioned degrees of motion. For
example, the lap may be in rotational lapping contact with the
workpiece and simultaneously be swept side-to-side across the
workpiece. According to an embodiment of the present invention, the
diameter of the lap is about 200 .mu.m or less, or is about 50
.mu.m or less, or is about 25 .mu.m or less. According to a
specific embodiment of the present invention, the diameter of lap
1100 is about 5 nm.
[0113] FIGS. 11D and 11E are side and bottom views, respectively,
of a lap 1102 according to another embodiment of the present
invention. Lap 1102 has a round sidewall 1105 and a bottom surface
1110. This embodiment differs from the embodiment shown in FIGS.
11A-11C in that the bottom surface 1110 has a curved profile as
viewed from the side and has a circular profile as viewed from the
bottom. Lap 1102 is deployable in variety of ways to lap a
workpiece. For example, lap 1102 may have a rotational degree of
freedom about the y-axis as indicated by double-headed arrow 1145.
The lap may have a similar rotational degree of freedom about the
x-axis. Further, lap 1102 may also be translatable along the z-axis
as indicated by double-headed arrow 1150. Rotating lap 1102 about
the y-axis and lowering it along the z-axis, while in lapping
contact with a workpiece 1135, will produce a curved indentation
1133 into the workpiece. According to embodiments of the present
invention, lap 1102 has a diameter of about 200 .mu.m or less. In
accordance with various embodiments of the invention the diameter
of the cylinder may be on the order of about 100 .mu.m or less, or
is about 50 .mu.m or less, or is about 25 .mu.m or less. According
to a specific embodiment of the present invention, the diameter of
the bottom surface as viewed from the bottom is about 5 nm.
[0114] While laps 1100 and 1102 are shown to have flat and curved
bottom surfaces, respectively, it should be understood, that the
bottom surfaces of these laps may have a variety of shapes, such as
conical, frusto conical, hemispherical, and the like. Laps with
conical ends are of use, for example, to impart a bevel shape, or
v-groove shape to a workpiece. Further, while the sidewalls of laps
1100 and 1101 are shown to be relatively smooth, the sidewalls may
have various contoured shapes that protrude from or are recessed
into the sidewalls.
[0115] Rotational motions previously described may be achieved by
use of active cantilevers described in co-owned copending U.S.
patent application Ser. No. 10/094,408, entitled "Active Cantilever
for Nanomachining and Metrology," now U.S. Pat. No. 6,923,044,
incorporated herein by reference in its entirety for all purposes.
Active cantilevers of the aforementioned application provide
rotational degrees of motion for scanning probe microscope (SPM)
tips. Laps previously described may be each be a tip of an SPM
(described in detail below) and each may be the tip of an SPM
having an active cantilever.
Laps Embodiments Formed From 110 Cut Silicon Wafers
[0116] FIGS. 12A and 12B are schematic top and cross-sectional
views, respectively, of a lap 1200 made from a silicon wafer cut
along the 110 plane according to an embodiment of the present
invention. Lap 1200 has a single straight track 1205 formed as a
recess in the wafer having a top surface 1225. Track 1205 is shown
to have two sidewalls 1230 and 1232 and a bottom surface 1234. FIG.
12B is a cross-sectional view taken along line 12B-12B of FIG. 12A
showing the profile of track 1205. Sidewalls 1230 and 1232 are
approximately parallel to a crystal plane of the wafer and are
approximately parallel to each other. As the sidewall are
approximately aligned with crystal planes of the wafer, the
sidewalls are relatively flat (e.g., approximately atomically
flat). Further, each sidewall is also approximately perpendicular
to top surface 1225 as the crystal plane is approximately
perpendicular to the wafer surface.
[0117] Track 1205 has similar dimensions as those of lap 100 shown
in FIG. 1A. For example, the height of sidewall segments (measured
between top surface 1225 and bottom surface 1234) 1230 and 1232 are
equal to about 200 .mu.m or less. In accordance with various
embodiments of the invention the height of the sidewall segments
may be on the order of about 100 .mu.m or less, about 75 .mu.m or
less, about 60 .mu.m or less, about 50 .mu.m or less, or about 10
.mu.m or less. According to other embodiments of the present
invention, the height of the sidewalls is about 1 .mu.m to 2 .mu.m
and the width of bottom surface is about 2 .mu.m to 4 .mu.m.
[0118] A workpiece may be lapped along sidewalls 1230 and 1232 to
produce a workpiece having two relatively parallel surfaces. Lap
1200 may also be used to produce workpieces with other profiles,
such as triangular, square, or other profiles. To lap such shapes,
the lap and workpiece are variously positioned. For example, to lap
a triangle, lap 1200 is placed in a first position to form a first
side of the triangle, then in a second position to form a second
side of the triangle, and finally in a third position to form a
third side of a triangle. Either the lap or the workpiece or both
may be positioned to achieve the desired lapping orientations.
[0119] Lap 1200 may also be used to lap curved profiles onto a
workpiece. To lap a curved profile onto a workpiece, either the lap
or the workpiece are rotated while the lap and workpiece are in
lapping contact. For example, to produce circular shaped
workpieces, the lap and workpiece may be rotated 360.degree. with
respect to each other. To produce curved surfaces, other than
circles, the lap or workpiece may be rotated through an angle less
than 360.degree.. For example, lap 1200 may be rotated trough
90.degree. to produce a partially rounded surface.
[0120] FIG. 13A is a schematic top view of a lap 1300 having a
hexagonal track 1305 according to an embodiment of the present
invention. Lap 1300 is comprised of six lap segments 1340a-1340f.
The six lap segments can be constructed from another lap, for
example, lap 1200 shown in FIG. 12A. FIGS. 13B and 13C show top and
side views, respectively, of lap 1200 with dashed lines 1352, 1354,
1356, and 1358 indicating location at which lap 1200 may be cut to
form segments 1340a-1340f. FIG. 13D shows a single segment 1340a of
lap 1300 to be constructed.
[0121] As the sidewalls of lap 1200 are approximately parallel to a
crystal plane and relatively flat (e.g., approximately atomically
flat), so too are the inner and outer sidewalls of lap 1300.
Accordingly, lap 1300 laps relatively smoother workpieces than laps
having the same hexagonal shape but having surface portions not
aligned with crystal planes. For example, a lap having a hexagonal
track may be formed from a contiguous silicon wafer cut along the
110 plane. However, the sidewalls forming the hexagonal track will
not all align with crystal planes and so the lap will have
relatively rougher (i.e., less flat) sidewalls than the sidewalls
of lap 1300.
[0122] FIGS. 14A and 14B are schematic top and cross-sectional
views, respectively, of lap 1400 having a hexagonal track 1405
according to another embodiment of the present invention. This
embodiment differs from the embodiment of FIG. 13A in that it has
sets of sidewalls that are not parallel.
[0123] Hexagonal track 1405 comprises six segments, each having an
associated pair of sidewalls, 1403a/1432a, 1430b/1432b,
1430c/1432c, 1430d/1432d, 1430e/1432e, and 1430f/1432f. Each
segment of track 1405 shares a common bottom surface 1434. FIG. 14B
is a cross-sectional view taken along line 14B-14B of FIG. 14A. The
cross-sectional view shows two segments of track 1405: one segments
defined by sidewalls 1430b, 1432b and surface 1424; and another
segment define by 1430e, 1432e, and surface 1424.
[0124] Lap 1400 comprises six segments denoted 1440a-1440f. Each of
the six segments is cut from a lap, such as lap 1200 shown in FIG.
12A. FIGS. 14C and 14D show top and side views, respectively, of
lap 1200 with dashed lines 1462, 1464, 1466, and 1438 indicating
locations at which the lap may be cut to make segments 1440a-1440f.
FIG. 14D show dashed lines 1262, 1264, 1266, and 1268 askew from
perpendicular to lap surface 1230.
[0125] From a top view, lap 1400 has a profile similar to lap 1300
shown in FIG. 13A. However, unlike lap 1300, track 1405 has sets of
sidewalls that are not parallel. The cross-sectional view shown in
FIG. 14B shows outer and inner sidewalls 1430b and 1432b parallel
with each other and outer and inner sidewalls 1430e and 1432e
parallel with each other. However, sidewalls 1430b and 1432b are
not parallel with sidewalls 1430e and 1432e.
[0126] Each of laps 1300 and 1400 is a specific embodiment of a lap
according to the present invention sharing hexagonal shaped tracks.
However, the laps are illustrative of a process by which laps
having a variety of shapes may be made. The process of cutting a
lap, such as lap 1200, may entail cuts along any angle. The process
of cutting a lap and rearranging the segments provides for the
creation of laps of various shapes. For example, triangular,
quadrilateral, pentagonal, and the like. In general, any arbitrary
non-uniform polygonal shape can be made.
Lap Material
[0127] According to an embodiment of the present invention, laps
are formed from substrates such as wafers. Suitable wafer materials
include those that may be shaped by well known semiconductor
fabrication techniques. For example, suitable wafers include those
in which a lapping track may be formed by wet and/or dry etching
techniques. Wet etching includes processes in which a wafer is
masked and immersed in a liquid reagent. The reagent chemically
removes the unmasked portions of the wafer. Wet etching produces
relatively smooth surface portions and is generally of use for
surface portions (e.g., track sidewalls) having heights of 3 .mu.m
or greater. Surface portions of lesser height tend to be undercut
by wet etch processes.
[0128] Dry etching includes processes in which a gaseous species is
made reactive in a plasma. The reactive gas chemically binds with
unmasked portions of a wafer forming a new chemical species,
thereafter the resultant chemical species is desorbed from the
wafer surface, and hence alters the wafer's surface. Wet etching
produces relatively smoother surfaces portions than dry etch
techniques. However, dry etch techniques are generally useful for
geometries in which wet etch techniques tend to undercut. For
example, dry etch is generally useful for producing tracks having
sidewall heights less than about 3 .mu.m, e.g., 1-2 .mu.m.
[0129] Referring again to FIG. 1B, recessed tracks 105 and 110 may
be formed by masking the areas surrounding the area where the
tracks are to be formed and etching the track into the wafer.
Referring again to FIG. 1C, raised tracks 105' and 110' can be made
by a similar yet varied masking technique. The area where tracks
are to be formed are masked (instead of the area surrounding the
tracks) and the wafer surface is wet or dry etched until the
desired track height is revealed. Dry and wet each techniques are a
cost effective methods for producing laps having a single track or
multiple tracks as each may be produced for relatively
insignificant cost differences.
[0130] Wafer material suitable for wet and dry etching include, for
example, silicon, silicon nitride, silicon dioxide, and various
types of glass (i.e., fluorine glass). Those of ordinary skill in
the art will recognize other useful material from which laps may be
made.
[0131] According to an embodiment of the present invention, silicon
wafers that are cut along the 100 crystallographic plane are etched
to produce laps. Silicon having this orientation is well suited for
laps having tracks such as those shown in FIGS. 1A, 4A, and 5A. The
tracks in each of these laps can be characterized as having surface
portions with a variety of angles with respect to the
crystallographic planes of the silicon wafer. Silicon wafers that
are cut along the 100 crystallographic plane can be etched at these
angles while maintaining relatively flat surface portions. To
produce a lap having relatively flatter surface portions (e.g.,
approximately atomically flat) silicon is etched along its crystal
planes. For example, for silicon wafers that are cut along the 100
crystallographic plane, one of the crystal planes is oriented
approximately 35.degree. from the surface normal of the wafer.
Trenches having surface portions approximately parallel to this
crystal plane are typically flatter than surface portions askew to
the crystal plane.
[0132] According to another embodiment of the present invention,
silicon wafers cut along the 110 crystallographic plane can be
etched to produce laps. Silicon wafers having this crystallographic
orientation have crystal planes approximately parallel to the
surface normal of the wafer. Accordingly, relatively flat surface
portions (e.g., approximately atomically flat) may be etched
approximately parallel to the crystal planes. Surface portions
etched at angles askew from the crystal planes produce relatively
rougher (i.e., less flat) surfaces. Laps having lapping surfaces
aligned with a crystal plane impart onto a workpiece relatively
smoother surfaces than a workpiece shaped from laps having a
lapping surface not aligned with a crystal plane.
[0133] According to an embodiment of the present invention, laps
may be used in combination to shape a workpiece. A lap having
relatively less flat, (i.e., rougher) surface portions are used to
roughly shape a workpiece. Laps having relatively flatter surface
portions are used to finely shape a workpiece once roughly shaped.
According to another embodiment of the present invention, laps
having relatively flatter surface portions are used to restore an
edge of a worn workpiece.
[0134] The above discussion has been primarily of laps formed from
silicon wafers;
[0135] however, other substances may be of use to make laps. For
example, carbon based materials may be used to make laps. According
to embodiments of the present invention, diamond, diamond like
carbon, and various carbides (e.g., titanium carbide) are used to
make laps. For example, diamond rods may be used to make laps such
as those shown in FIGS. 11A-11E. Those of skill in the art will
know of other material suitable from which to construct laps, such
as cubic boron nitride and other hard crystals.
Lap Coatings
[0136] According to an embodiment of the present invention laps are
coated to enhance material removal from a workpiece during
nanolapping. Coatings are generally categorized into two groups,
abrasive and chemical. Abrasive coatings mechanically remove
material from a workpiece and generally do not chemically react
with the removed material. Chemical coatings react with the surface
of a workpiece thereby removing material from the surface.
[0137] According to an embodiment of the present invention, diamond
like carbon (DLC) is coated onto a lap. Diamond like carbon is both
hard and relatively chemically inert at low temperatures. Coated
onto a lap, diamond like carbon forms a relatively fine
abrasive.
[0138] Diamond like carbon can be coated onto a lap via a vacuum
arc process such as plasma enhanced chemical vapor deposition or
via ion beam techniques. Those of skill in the art will know other
useful coating processes for DLC. Coating thickness of DLC vary
from about 70 nanometers to about 100 nanometers. Selected surfaces
of a lap may be coated with DLC or all of the surfaces may be
coated. For example, tracks formed in a wafer may be coated while
other masked portions, for example a top surface, of the lap are
not coated.
[0139] According to another embodiment of the present invention,
diamond is coated onto laps. Diamond can be grown on a DLC layer.
Diamond coatings vary from about 70 nanometers to about 100
nanometers to about 5 .mu.m. Diamond coated onto a lap forms a
relatively fine abrasive, although the coating is generally more
course than DLC.
[0140] The discussion above provides examples of two coatings, DLC
and diamond, that may be coated onto a lap to create an abrasive
surface. However, numerous other substances may be coated onto a
lap to create the abrasive surface. For example, cubic boron
nitride is a relatively hard substance that may be used as an
abrasive coating. Other examples of useful abrasive coatings
include various types of carbides, (e.g., titanium carbide). Those
of skill in the art will know of other useful substances that can
be coated onto a lap to form an ordinary abrasive surface.
[0141] According to an embodiment of the present invention,
chemically reactive coatings are deposited on a lap's surfaces.
Chemically reactive coatings include those chemically bonding to
the atoms of a workpiece and thereafter removing the atoms from the
workpiece.
[0142] According to one embodiment of the present invention,
aggressive carbide formers can be coated onto laps. Aggressive
carbide formers chemically react with workpieces having carbon,
(i.e., diamond). Aggressive carbide formers include, for example,
iron, nickel, chromium, iron, titanium, manganese, tungsten, and
the like. Each of these elements has an affinity for carbon and
form stable carbon compounds when rubbed against a workpiece having
carbon. Aggressive carbide formers are of use for lapping, for
example, workpieces made of diamond, carbide, and diamond like
carbon.
[0143] Aggressive carbide formers more readily bond with carbon at
elevated temperatures than at relatively lower temperatures.
However, if temperatures are excessively high, a lap and workpiece
will gall each other. The temperature point at which two surfaces
gall each other is often referred to as the flash temperature.
According to an embodiment of the present invention, chemical
lapping can be performed below the flash temperature. According to
a further embodiment of the present invention, chemical lapping can
be performed in a temperature range from about 200.degree. C. to
about 300.degree. C.
Scanning Probe Microscope Tips and Substrates
[0144] According to an embodiment of the present invention, the
previously described laps, are used in conjunction with a scanning
probe microscope (SPM) to give shape to a workpiece. An SPM
typically operates by sweeping a tip in a raster pattern across the
surface of a substrate. As the tip is swept across the substrate,
various microscopy techniques may be used to generate an image of
the surface of the substrate. Examples of SPM techniques include,
scanning electron microscopy, scanning tunneling microscopy, atomic
force microscopy, and the like.
[0145] According to an embodiment of the present invention, a lap
may be an SPM tip or may be a substrate. The workpiece to be shaped
may also be an SPM tip or a substrate. For example, a substrate
that serves as a lap may be placed under an SPM tip. In such a
configuration, the SPM tip is the workpiece to be shaped. In an
alternative configuration the lap may be the SPM tip and placed
over the workpiece. In such a configuration, the substrate is the
workpiece to be shaped. An SPM tip that changes the structure of a
substrate is often referred to as a "tool," "tool tip," or
"toolpiece" while the term "tip" is often used in reference to
imaging. However, for convenience sake, tips, tools, tool tips, and
toolpieces will both be referred to as "SPM tips" or simply
"tips."
[0146] In a typical SPM, stacked sets of piezoelectrics control the
movement the substrate and/or tip. Typically, a separate stacked
set of piezoelectrics control motion along each of the Cartesian
axes. For example, one stacked set of piezoelectrics may control
motion of a tip or substrate along an SPM's x-axis, a second set of
stacked piezoelectrics may control motion of a tip or substrate
along an SPM's y-axis, and a third set of piezoelectrics may
control motion of a tip or substrate along an SPM's z-axis.
[0147] The range of motion of a typical SPM tip is about 200 .mu.m
to less than one angstrom along each of the Cartesian axes. More
generally stated, for a typical SPM, a substrate and an SPM tip can
be moved relative to each other by about 200 .mu.m to less than
about one angstrom, along the SPM's x, y, and z-axes. Some SPMs
have maximum ranges of motion less than 200 .mu.m, with typical
maximum ranges being about 100 .mu.m, 75 .mu.m, 50 .mu.m, 25 .mu.m,
and 10 .mu.m. According to an embodiment of the present invention,
lap dimensions are made to accommodate the typical ranges of motion
of an SPM tip. For example, referring to FIG. 1A, the width of
octagon track 105 along a widest lateral dimension (width D) or
narrowest lateral dimension (width C), can be 100 .mu.m or less, or
about 75 .mu.m or less, or about 60 .mu.m or less, or about 50
.mu.m or less, or about 25 .mu.m or less, or about 10 .mu.m or
less. According to other embodiments of the present invention, the
width of square track 405A of lap 400 (shown in FIG. 4A) between
opposite corners (width B) or between opposite surfaces (width C),
can be about 100 .mu.m or less, or about 75 .mu.m or less, or about
60 .mu.m or less, or about 50 .mu.m or less, or about 25 .mu.m or
less, or about 10 .mu.m or less. According to still other
embodiments of the present invention, the broadest expanse (width
B) or narrowest expanse (width C) of elliptical track 505 of lap
500 (shown in FIG. 5A) can be about 100 .mu.m or less, or about 75
.mu.m or less, or about 60 .mu.m or less, or about 50 .mu.m or
less, or about 25 .mu.m or less, or about 10 .mu.m or less. Laps
shown in FIGS. 13A and 14A have similar dimensions.
[0148] As discussed above, piezoelectrics provide very fine control
of the range of motion of an SPM tip with respect to a substrate.
For example, tip control may be less than about one angstrom. This
fine control provides for removal of material from a workpiece
during a single lapping stroke of as little as one atom or
molecular species, and as little as one layer of atoms or species
from a workpiece. Accordingly, the present invention provides for
the production workpieces having approximately atomic level
precision. For example, a workpiece to be formed into a knife edge
may be sharpened to approximately an atomic-scale sharpness.
Nanolapping Methods
[0149] Laps may have defects along various portions of a surface.
Defects may include, for example, pits, bumps, undercuts, and the
like. Pits or bumps may form, for example, in a silicon substrate
during the etching process. Surface portions that align along
planes other than crystal planes more readily form pits and bumps
than surface portions aligning with the crystal planes.
Additionally, defects tend to form along inside corners more
frequently than along other lap features. According to an
embodiment of the present invention, during a lapping process, a
workpiece is disengaged from a lapping surface near corners and
defects, and the workpiece is reengaged with the lapping surface
once the workpiece is moved beyond the corner or defect.
[0150] FIG. 15 shows a lapping path 1505 around a square lap 1500
according to an embodiment of the present invention. As shown,
lapping path 1505 indicates that a workpiece (not shown) is
disengaged from the sidewalls 1512, 1514, 1516, and 1518 in the
proximity of the corners 1522, 1524, 1526, and 1528. A workpiece
disengaged at a corner, is translated around the corner, and is
then reengaged with the sidewalls beyond the corner. Accordingly,
the workpiece is not affected by any possible defect existing in
the corners. This method is not limited to square laps, but may be
applied to other laps having corners.
[0151] FIG. 16 shows a lapping path 1605 around a defect 1645
occurring in the sidewall 1620 of a lap 1600 according to an
embodiment of the present invention. As shown, lapping path 1605
indicates that a workpiece will be disengaged from sidewall 1620 in
the proximity of the defect, and translated around the defect. The
workpiece reengages with the sidewall beyond the defect. This
aspect of the invention ensures that a workpiece is not affected by
lap defects during a lapping process.
Workpiece Location and Placement
[0152] Of significance in lapping relatively small workpieces
(e.g., about 100 .mu.m or less) is knowing the location of the
workpiece once made and placing the workpiece in a desired
location. Workpieces of such small scale once lost are difficult to
find. If a workpiece is chipped off during a lapping process,
Brownian motion may keep the workpiece aloft and carry it away to
locations where the workpiece may be difficult to find. Even if a
workpiece is in a known location, picking the object up and moving
it to another known location can also be difficult. According to a
lapping method of the present invention a workpiece is lapped to
have known fracture zones. For example, FIG. 10D shows a threaded
workpiece 1060 having a known fracture zone 1065. Fracture zone
1065 is located between threaded portion 1070 and stock portion
1075. The threaded section coupled to the stock section may be
positioned by SPM controls to a known location and separated from
the stock along the fracture zone once positioned.
[0153] Various techniques may be deployed to separate the threaded
portion from the stock portion at the fracture zone. For example,
the workpiece may be subjected to a torque causing the fracture
zone to mechanically fail. Alternatively, the fracture zone may be
heated causing it to mechanically fail or mechanically weaken due
to local thermal expansion. Weakening the fracture zone provides
that a relatively lower torque may be applied to the workpiece to
separate the threaded portion from the stock portion. According to
another alternative, the fracture zone may be heated in the
presence of a chemical reagent that etches more vigorously the
relatively warmer than cooler portions of the workpiece (e.g.,
diamond workpiece in oxygen) thus etching through the fracture
zone.
[0154] The fracture zone may be heated by various techniques, for
example a low frequency current can be passed through a conductive
workpiece (e.g., boron doped diamond, P or N doped silicon, all
metals) to heat the fracture zone. Low frequency current heats the
portions of the workpiece having the highest resistance, i.e.,
portion of the workpiece with the smallest cross section (e.g.,
fracture zone). Alternatively, a high frequency current may be
passed through a workpiece heating the fracture zone. High
frequency current tends to travel across surfaces heating portions
of the workpiece having the smallest surface area (e.g., fracture
zone). According to another alternative, the fracture zone may be
shaped such that heat passed through the workpiece builds up in
fracture zone causing the fracture zone to be relatively warmer
than other portions of the workpiece.
[0155] A chemical reagent can similarly be applied to a workpiece
having an approximately uniform temperature such that the fracture
zone is etched through prior to other portions of the workpiece.
Subsequent to the fracture zone being etched through, the workpiece
may be washed or the chemical reagent neutralized.
Nanomeasurements
[0156] Having produced the micron- and submicron-scaled shapes in
accordance with the various lapping techniques discussed above, it
might be desirable to confirm certain features of the shape by
making a series of nanomeasurements. More generally, it might be
desirable to be able to verify micron- and submicron-scaled
structures regardless of how they were made. For example, it might
be desirable to confirm that a given shape has certain dimensional
features. It might be desirable to make nanomeasurements during the
lapping process to gauge the progress of the lap. The measurements
might be useful in providing feedback to inform the nanolapping
process in order that appropriate adjustments can be made as
needed.
[0157] FIG. 17 shows a highly schematized representation of a
workpiece 1702 having an arbitrary shape 1714 formed thereon. The
shape 1714 can be produced by the nanolapping techniques discussed
above. Typically, a nanolapping operation is performed to produce a
shape having a predetermined form. However, the actual shape may
not always be known; breakage may occur during the nanolap, or
unexpected material behavior may cause unpredictable lapping.
Consequently, specific features of shape 1714, while having a
generally known (expected) shape, will not always be known with
certainty.
[0158] According to an embodiment of the invention, the shape, as
shown in FIG. 17, is formed such that it is disposed at a free end
of a segment 1712 of the workpiece 1702, the workpiece having a
fixed end 1716. This arrangement facilitates utilizing the
workpiece 1702 as a scanning probe, where the segment 1712 serves
as a cantilever and the shape 1714 being the scanning tip of the
probe. This tip will be referred to as an "unknown scanning tip,"
since the specific structure of the shape is not known, though it
has an expected shape. As will be discussed below, the
nanomeasurement technique of this aspect of the invention can
reveal specific structural features of the unknown scanning
tip.
[0159] FIG. 17 further shows a cross-sectional view of a substrate
1722 having a reference surface 1724. A plurality of reference
structures 1732-1738 formed on the reference surface are shown in
cross-section. The reference structures shown are merely typical
examples provided for illustrative purposes. For example, the
structure 1732 is a mushroom-shaped structure having a T-shaped
cross-sectional view. Structure 1734 is a cone-shaped structure.
Structures 1736 and 1738 are knife-edge structures. A first
knife-edge 1736 is shown disposed at an arbitrary angle. A second
knife-edge 1738 is shown disposed in perpendicular relation to the
reference surface 1724. As will become clear, any arbitrarily
shaped reference structure can be suitable for purposes of making
nanomeasurements.
[0160] FIG. 18 is a high level flow chart illustrating the process
of making nanomeasurements according to embodiments of the
invention. FIGS. 19A and 19B are sequence diagrams illustrating
generally the scanning sequence. Thus, referring to FIGS. 18 and
19A, a workpiece 1902 having a shape formed thereon, which features
are only approximately known, is obtained in a step 1802. As
mentioned above, the workpiece can be the product of a nanolap
operation performed in accordance with the invention, or can be
obtained in other ways. The workpiece 1902 is utilized as scanning
probe 1932 which has a generally unknown scanning tip 1934 disposed
at a free end of a cantilever 1936. The tip is "unknown" in that
its specific surface features are only approximately known.
[0161] Next, in a step 1804, the scanning probe 1932 is scanned
across a reference surface 1924 having one or more reference
structures 1942, 1944 formed thereon. As can be seen in FIG. 19A,
the scan proceeds in the direction indicated by the arrow 1916. Due
to the atomic forces between the unknown scanning tip 1934 and the
reference tip 1943, interactions arise as the tips pass each other.
In one embodiment of the invention, the scanning is an AFM-type
scan (atomic force microscopy), where the interactions manifest
themselves as deflections of the cantilever 1936, scanning probe
1932, or scanning tip 1934. The scanning can be contact mode
scanning or non-contact mode scanning In another embodiment of the
invention, the scanning is an STM-type scan (scanning tunneling
microscopy), where the interactions manifest themselves as
fluctuations in a tunneling current between the unknown scanning
tip 1934 and the reference tip 1943.
[0162] In a step 1806, the interaction is detected to produce scan
data during the scan. In the case of an AFM scan, the deflections
of the cantilever can be detected optically, electrically (e.g.,
with piezoelectric materials), or by other conventional and known
techniques to produce deflection signals indicative of the amount
of cantilever deflection. Similarly, tunneling current fluctuations
in an STM scan can be detected by known techniques to produce data
indicative of changes in the magnitude of the tunneling current
which occur during the scan.
[0163] FIG. 19A illustrates that scanning across the reference
structure 1942 will produce signals indicative of the interaction
between the reference tip 1943 and a bottom surface 1935 of the
scanning tip 1934, as the scanning tip is scanned to a position
indicated in phantom 1934'. Incidentally, it is noted that the
relative motion between the scanning probe 1932 and the reference
surface 1924 can be achieved in various known ways. The scanning
probe can be moved about while keeping the substrate 1922
stationery. The scanning probe can be kept stationery and the
substrate translated to effect scanning Both the scanning probe and
the substrate can be translated in a coordinated effort to effect
scanning
[0164] FIG. 19B shows the unknown scanning tip 1934 having been
moved proximate another reference structure 1944. The reference
structure 1944 is configured to permit detecting a side surface
1937 of the unknown scanning tip when the scanning probe 1932 is
translated in the direction indicated by the arrow 1918. Here, a
reference tip 1945 on the reference structure 1944 interacts with
the side surface 1937 to produce signals indicative of the
interaction when the scanning tip 1934 is scanned along the
indicated direction.
[0165] In a step 1808, an image or other information relating to
the unknown scanning tip 1934 can be produced from the scan signals
collected in step 1806. In a conventional scan, the scanning tip
has known dimensional features, and the surface has unknown
features. The image produced from the scan data using the
conventional data processing techniques reveals the unknown surface
features. In accordance with the embodiments of the present
invention, the same data processing techniques can be applied by
combining the collected scan data with "known" (predetermined) data
about the surface features of the reference surface 1924 to produce
information (typically an image) relating to the unknown scanning
tip 1934.
[0166] As is well known in the art and in practice, using known
reference standards it is possible to determine the shape,
curvature, and dimensions of the tip/workpiece by convolution with
known shapes, points and/or edges over which the tip/workpiece is
scanned. This makes the tip/workpiece convolve with the surface or
reference structure which produces the z signal (at a given scanned
x,y position) which is the data point. Not unlike the action of an
optical lens to create the 2D Fourier Transform of the object on
which the lens is focused, the convolution is a property of the
physics of the arrangement in an SPM.
[0167] In accordance to an embodiment of the invention, the
nanomeasure takes measurements with respect to a known reference
shape, point and/or edge of specific elements of the nanotool to
determine if the target measure has been obtained. This is similar
to a machinist making a measure of a shaft being turned on a
conventional macro lathe into a target cylinder of target diameter.
The machinist merely measures one (or more) diameters along the
developing cylinder in order to guide his next cut. The nanolap
system uses similar checks in one or more dimensions of the stock
part and/or tip/workpiece.
[0168] FIG. 20 shows reference structures 2034, 2036, and 2042
which are merely examples used to illustrate the kinds of surface
features comprising a reference surface 2024. The known surface
features comprise predetermined structures having preset features
of known dimensions. Thus, for example, consider the
mushroom-shaped structure 2032. If such a structure is called for,
it can be fabricated or formed with known specific dimensions. Its
cap 2042 would have a known diameter D.sub.1 (typically in units of
.ANG., angstroms) and is spaced apart from the surface 2024 by a
distance H. The edge of the cap would have a known shape and a
corresponding known edge dimension D.sub.2. Similarly, the cone
structure 2034 would have known a tip dimension D.sub.3, including
perhaps the height of the cone, the diameter and so forth. A
knife-edge structure 2036, if needed, could be formed with a known
tilt angle 0.degree. relative to the reference surface, and possess
a specific known edge-shape and edge dimension D.sub.4. Also,
separation distances D.sub.5 between the various reference
structures may can be controlled. In sum, the reference surface and
its features (e.g., arbitrarily shaped reference structures) can be
formed with predetermined shapes having preset measurements.
[0169] It can be appreciated from the foregoing that a reference
surface having known surface features (i.e., reference structures)
can be designed to provide a "reverse imaging" capability to reveal
the surface features of an unknown scanning tip. The specific
features and structures comprising the reference surface will be
driven by the expected shape of the unknown scanning tip. It should
be clear that the particular shapes of the reference structures are
not limited to the example shapes disclosed herein. Virtually any
reference structure of arbitrary shape has the potential of being
an appropriate structure, depending on the expected shape of the
unknown scanning tip. This aspect of the invention is particularly
suited to the disclosed nanolap procedure wherein arbitrary micron
and submicron-sized shapes are lapped into a workpiece.
Verification of the lapped shape can be made by utilizing the
workpiece as a scanning probe where the lapped shape serves as the
unknown scanning tip.
[0170] In another embodiment of the invention, the nanomeasurement
technique can be used in a feedback loop to guide the nanolapping
operation. FIG. 21 shows a high level flow chart illustrating the
basic steps of this embodiment of the present invention. In a step
2102, a nanolap operation is performed to lap a shape into a
workpiece. The shaped portion of the workpiece can be utilized as
an unknown scanning tip to scan a reference surface having various
known surface features, in a step 2104. Next, in a step 2106,
information collected during the scan is processed to produce
information about the shaped portion. The produced information can
be used to determine, in a decision step 2107, whether to proceed
with another nanolap operation or to terminate the operation. If a
decision is made to continue with a subsequent nanolap operation,
then in a step 2108, parameters of the nanolap operation can be
adjusted based on the produced information. Processing then
continues with step 2102, and the cycle repeated until a decision
to terminate the processing is made.
[0171] FIG. 22 shows an illustrative embodiment of the present
invention by way of a generalized block diagram, illustrating an
atomic force microscopy system 2200 that is adopted for
nanolapping. An atomic force scanning probe 2202 is the workhorse
of the nanolapping system. A typical probe comprises a cantilever
and a tip (the lap) disposed at the free end of the cantilever.
Various lap shapes and configurations suitable for nanolapping are
disclosed above.
[0172] The probe 2202 can be coupled to a first translation stage
2204. The first translation stage can provide movement of the probe
in the X-Y plane. By convention, the X-Y plane is the plane
parallel to the major surface of a workpiece 2232. Thus, the probe
can be positioned in the X-Y position relative to the workpiece by
the first translation stage. The first translation stage can also
provide movement of the probe in the Z-direction and thus position
the probe in three-dimensional space relative to the workpiece.
Translation stages are known and well understood devices.
Typically, they are piezoelectric devices.
[0173] Alternatively, a second translation stage 2206 can be
provided. The workpiece 2232 can be affixed to the second
translation stage to provide X-Y motion of the workpiece relative
to the probe 2202. Furthermore, the second translation stage can
provide motion of the workpiece in the Z direction relative to the
probe.
[0174] The relative motion between the probe 2202 and the workpiece
2232 can be achieved by any of a number of techniques. The probe
can be translated in three dimensions while maintaining the
workpiece in a stationary position. Conversely, the workpiece can
move relative to a stationary probe. Both the probe and the
workpiece can be moved in a coordinated fashion to achieve rapid
positioning. The first translation stage 2204 might provide only
X-Y motion, while Z-axis positioning is provided by the second
translation stage 2206; or vice-versa. These and still other
combinations of concerted motions of the probe and the workpiece
can be performed to effect relative motion between the probe and
the workpiece.
[0175] The nanolapping system has two configurations: (1) The
system can be configured to perform nanolapping, wherein the
scanning probe 2202 is equipped with a scanning tip configured as a
lap and a shape is lapped into the workpiece 2232 in the various
ways discussed above. (2) The system can be configured for
nanomeasurements, wherein the workpiece is now the scanning probe.
The shape that was lapped into the workpiece is the scanning tip,
albeit an "unknown" scanning tip. A substrate (e.g., see FIG. 17)
having a reference surface 1724 with known features such as
reference structures 1732, 1734, 1736, and 1738 is scanned by the
unknown scanning tip in the manner discussed above.
[0176] An excitation source 2214 delivers an excitation energy to
the probe 2202 to make the probe do work. The excitation energy can
be any form of energy suitable to drive the probe. For example, a
typical scanning probe used in atomic force microscopy comprises a
cantilever formed of a piezoelectric material. The piezoelectric
material can be driven by an electrical excitation energy. However,
alternative probe architectures might use a bi-metal construction
that is driven by thermal energy. Surface acoustic waves (SAW) can
also be used as the excitation energy.
[0177] A detection module 2216 is coupled to detect atomic
interactions between the atoms which constitute the probe tip and
the constituent atoms of the surface being scanned. Many detection
techniques are known. For example, if the probe is operated in AFM
(atomic force microscopy) mode, the cantilever is deflected by the
interatomic forces acting between the tip and the surface as the
tip is scanned across the surface. The deflections can be measured
optically. For piezoelectric cantilevers, the deflections can be
measured by measuring changes in the electrical characteristics of
the cantilever. Measurement signals indicative of the amount of
deflection can be analyzed with known analytical techniques to
produce data representative of the atomic scale topography of the
surface.
[0178] A generalized controller 2212 can be configured to provide
various computer-based functions such as controlling the components
of the nanolapping system, performing data collection and
subsequent analysis, and so on. Typically, the controller is some
computer-based device; for example, common architectures are based
on a microcontroller, or a general purpose CPU, or even a custom
ASIC-based controller.
[0179] Appropriate control software is provided to operate the
computing components to perform the foregoing functions. For
example, control signals coordinate the components of the
nanolapping system to effect nanolapping operations disclosed
herein. It is understood that the generalized controller functions
can be allocated to other system components to meet particular
system requirements and constraints for a given implementation. For
example, data analysis functionality can easily be off-loaded to
another computer. The nanolapping system 2200 can have a network
connection to a larger system. It is well within the capability of
persons of ordinary skill in the relevant arts to produce the
appropriate programming code needed to perform the control
sequencing and delivery of control signals to coordinate the
various components of the nanolapping system 2200 to effect the
processing discussed below.
[0180] A user interface 2222 is provided to allow a user to
interact with the system. The "user" can be a machine user. A
machine interface might be appropriate in an automated environment
where control decisions are provided by a machine.
[0181] A data store 2252 contains various information to facilitate
nanolapping operations and for overall operation of the nanolapping
system. The data store contains the programming code that executes
on the controller 2212, described in the flow charts of FIGS. 18
and 21. Other kinds of information include parameters for setting
up the nanolapping system to perform a nanolapping operation. The
data store shown in the figure can be any appropriate data storage
technology, from a single disk drive unit to a distributed data
storage system.
Conclusion
[0182] While the above is a thorough description of specific
embodiments of the invention, various modifications, alternative
constructions, and equivalents may be used. For example, laps may
be made from quartz or other hard crystalline substances. Further,
laps may be of use not only to shape workpieces but may be used to
reshape a previously shaped workpiece, or a workpiece that is worn
from use. For example, a finely sharpened knife made from, say
diamond, by a lapping process, may be resharpened by nanolapping,
once the knife has been dulled from use. Therefore, the above
description should not be taken as limiting the scope of the
invention as defined by the following claims.
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