U.S. patent application number 14/014510 was filed with the patent office on 2014-01-02 for micro-gripper.
This patent application is currently assigned to CARL ZEISS MICROSCOPY GMBH. The applicant listed for this patent is Frank ALTMANN, Christian GROSSE, Hilmar HOFFMEISTER, Detlef RIEMER, Michel SIMON. Invention is credited to Frank ALTMANN, Christian GROSSE, Hilmar HOFFMEISTER, Detlef RIEMER, Michel SIMON.
Application Number | 20140001361 14/014510 |
Document ID | / |
Family ID | 38289939 |
Filed Date | 2014-01-02 |
United States Patent
Application |
20140001361 |
Kind Code |
A1 |
GROSSE; Christian ; et
al. |
January 2, 2014 |
MICRO-GRIPPER
Abstract
A method is described for producing a micro-gripper, which
comprises a base body and a gripping body connected integrally to
the base body, which projects beyond the base body and provides a
receptacle slot on a free end area in such a way that a
micrometer-scale or sub-micrometer-scale object may be clamped in
the receptacle slot for gripping and holding, as well as a
micro-gripper according to the species.
Inventors: |
GROSSE; Christian; (Kollau,
DE) ; ALTMANN; Frank; (Halle, DE) ; SIMON;
Michel; (Reichardtswerben, DE) ; HOFFMEISTER;
Hilmar; (Aalen, DE) ; RIEMER; Detlef;
(Markkleeberg, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GROSSE; Christian
ALTMANN; Frank
SIMON; Michel
HOFFMEISTER; Hilmar
RIEMER; Detlef |
Kollau
Halle
Reichardtswerben
Aalen
Markkleeberg |
|
DE
DE
DE
DE
DE |
|
|
Assignee: |
CARL ZEISS MICROSCOPY GMBH
Jena
DE
|
Family ID: |
38289939 |
Appl. No.: |
14/014510 |
Filed: |
August 30, 2013 |
Current U.S.
Class: |
250/307 ;
294/99.1 |
Current CPC
Class: |
B25J 19/007 20130101;
B25J 7/00 20130101; H01J 37/20 20130101; B81C 99/002 20130101 |
Class at
Publication: |
250/307 ;
294/99.1 |
International
Class: |
B25J 7/00 20060101
B25J007/00; H01J 37/20 20060101 H01J037/20 |
Foreign Application Data
Date |
Code |
Application Number |
May 20, 2006 |
DE |
10 2006 023 768.4 |
Mar 9, 2007 |
EP |
PCT/EP2007/002109 |
Claims
1. A micro-gripper for clamping objects with dimensions less than
micrometer comprising: receptacle slot for gripping and holding the
objects between a first gripping element and a second gripping
element: the first gripping element including at least one first
material layer disposed on a first sacrificial layer; the second
griping element including the at least one first material layer
bonded to a second material layer at a base body of the
micro-gripper; the receptacle slot including ends respectively
comprising the at least one first and the second material layers
with the receptacle slot being disposed between the at least one
first material layer and the second material layer; and wherein the
base body and the gripping body are a planar body defined by two
flat overlapping planar body surfaces oriented parallel to one
another.
2. A micro-gripper, comprising a base body and a gripping body
connected integrally to the base body, which projects beyond the
base body and provides a receptacle slot on a free end area that a
micrometer-scale or sub-micrometer-scale object may be clamped in
the receptacle slot for gripping and holding, and wherein the base
body and the gripping body are a planar body, which is exclusively
defined by two flat planar body surfaces oriented parallel to one
another and overlapping and at least one first and one second
material layer are at least in an area directly bonded to one
another.
3. The micro-gripper according to claim 2, wherein: the planar body
surfaces completely overlap.
4. The micro-gripper according to claim 2, wherein: the planar body
surfaces correspond to a circular sector having a centerpoint angle
.alpha..ltoreq.180.degree. and the gripper body is located on a
circular sector tip which projects beyond the circular sector.
5. The micro-gripper according to claim 2, wherein: the planar body
surfaces correspond to a circular segment having a centerpoint
angle .alpha..ltoreq.180.degree. and the gripping body is located
in a center of a circular segment chord, projecting beyond the
circular segment.
6. The micro-gripper according to claim 2, wherein: the planar body
surfaces comprise a polygon and the gripping body project beyond a
peripheral edge of the polygon.
7. The micro-gripper according to claim 4, wherein: the circular
sector has a circular radius adapted to a radius of a sample
retainer of a microscope, a SE microscope or TE microscope.
8. The micro-gripper according to claim 5, wherein: the circular
segment has a circular radius adapted to a radius of a sample
retainer of a microscope, a SE microscope or TE microscope.
9. The micro-gripper according to claim 7, wherein: the circular
radius is 1.5 mm.
10. The micro-gripper according to claim 8, wherein: the circular
radius is 1.5 mm.
11. The micro-gripper according to claim 2, wherein: the receptacle
slot has internal clamping faces which are parallel to, spaced
apart from, and overlapping one another.
12. The micro-gripper according to claim 9, wherein: the clamping
faces include a dimension of 10 nm to 10 .mu.m.
13. The micro-gripper of claim 12, wherein: the dimension is 50 nm
to 1 .mu.m.
14. The micro-gripper according to claim 11, wherein: the clamping
faces are rectangular or square.
15. The micro-gripper according to claim 9, wherein: the clamping
faces have a shape tapering in a direction toward the opening of
the receptacle slot.
16. The micro-gripper according to claim 10, wherein: the clamping
faces have a shape tapering in a direction toward an opening of the
receptacle slot.
17. The micro-gripper according to claim 9, wherein: the clamping
faces completely overlap.
18. The micro-gripper according to claim 10, wherein: the clamping
faces completely overlap.
19. The micro-gripper according to claim 2, wherein: the base body
and the gripping body comprise one of: plastic, ceramic, metal,
semimetal, or polysilicon.
20. The micro-gripper according to claim 2, wherein: the base body
and the gripping body include uniform material layers comprising
different materials.
21. A method of use of the micro-gripper according to claim 2
comprising accommodating, transporting, and holding material
samples during study in a TE microscope.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a Divisional application of U.S. Ser.
No. 12/301,641, filed Nov. 20, 2008, which, claims the benefit of
PCT/EP2007/002109, filed Mar. 9, 2007, which application is
incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to a micro-gripper for accommodating
and holding micrometer-scale or sub-micrometer-scale objects and to
a method for the production thereof.
[0004] 2. Description of the Prior Art
[0005] Micro-grippers are currently used in numerous fields in the
context of microsystem technology. Thus, micro-grippers are used,
for example, in microtechnology and nanotechnology for manipulation
and mounting or for joining extremely small objects. Further areas
of application for micro-grippers are found in physics, biology,
chemistry, and medicine, micro-grippers being used, for example, in
the context of the analysis and assaying of samples for
accommodating, gripping, and holding the samples.
[0006] The micro-grippers typically comprise a base body, which is
connected to two or more movable and/or elastic gripping elements,
which are used to accommodate and hold an object. At least one
actuator provided on the micro-gripper is typically provided for
the active actuation of the gripping elements, which moves the
gripping elements, which act toward one another. In micro-grippers
of this type, the gripping forces acting on the object may be
partially set or regulated by a corresponding activation of the
actuators. Micro-grippers without actuators are also known, in
which the accommodation and holding of an object does not occur
actively, but rather passively with exploitation of elastic
material properties. Micro-grippers of this type have at least two
opposing gripping elements spaced apart from one another, between
which an object may be clamped. The gripping elements are
elastically deformed by the clamping of an object between them, and
thus generate elastic retention forces reacting onto the
object.
[0007] It is to be noted here that for the following statements,
the term micro-gripper is restricted to the versions having only
two gripping elements.
[0008] Thus, an embodiment of a micro-gripper for micro-mounting is
disclosed in the publication DE 195 23 229 A1, which comprises a
base body, a piezotranslator fastened to the base body as a linear
actuator, and a microstructure body connected to the base body and
the piezotranslator. Two opposing gripping elements acting toward
one another and a mechanical lever transmission having bending
joints for the enlarging transmission of a linear movement of the
piezotranslator onto the gripping elements are constructively
unified in one component in the microstructure body. Upon a length
change of the piezotranslator, the elastic bending elements deform
and thus initiate a targeted movement of the gripping elements away
from or toward one another.
[0009] The production of the microstructure body is performed from
a (100) silicon wafer polished on both sides having a thickness of
240 .mu.m using the known structuring processes, lithography, and
anisotropic etching. The microstructure body is subsequently
fastened on the base body, a silicon substrate, using adhesive in
such a way that only selected small contact areas between the
microstructure body and the base body are glued, the bending
elements and the gripping elements being axially displaceable along
the contact faces. The production of the microstructure body from
silicon, especially its good ability to be micro-structured and the
lack of plastic deformation of silicon, is especially emphasized as
the essential advantage of the described micro-gripper. In
addition, the possibility exists of attaching piezoelectric, for
example, piezoresistive layers to the gripping elements, in
particular to their particular gripping faces, to convert the
gripping force into an electrical signal and thus to adapt the
gripping force to the object to be gripped. Further embodiments of
micro-grippers which use piezosystems as actuators may be inferred,
for example, from the publications DE 196 48 165 A1 and DE 101 14
551 C1.
[0010] In addition to piezo systems, other elements or principles
are also used to move the gripping elements. Thus, a micro-gripper
may be inferred from the publication DE 197 15 083 A1, in which
flat coils or permanent magnets of an electromagnetic drive are
integrated in a yielding gripping mechanism. The closing of the
gripping elements is caused by applying an external magnetic field.
The publications US 2004/0004364 A1, US 2002/0061662 A1, and U.S.
Pat. No. 5,149,673 A, in contrast, describe micro-grippers whose
gripping elements may be moved using electrostatic attractive or
repulsive forces. Finally, a nanogripper is disclosed in the
publication US 2005/0029827 A1, in which the gripping elements may
be moved by exploiting electro-thermal material properties. The
gripping elements are connected via a jointed mechanism to elements
which heat as a result of a current flux, expand, and cause a
movement of the gripping elements via the jointed mechanism.
[0011] The grippers cited up to this point all have the
disadvantage that it is necessary to feed electrical or magnetic
energy to the actuator to grip and hold objects. If this is
interrupted or disturbed, a failure of the gripper occurs, that is,
the object may detach from the micro-gripper in an undesired way.
In addition, the necessary electrical adaptation of the
micro-gripper in the required dimensions in the micrometer range is
complex and costly.
[0012] In particular, any contamination of the sample by the
micro-gripper, for example, by a material transfer from a preceding
sample to the next sample, is to be prevented for applications of
micro-grippers in the scope of material analysis of
micrometer-scale or sub-micrometer-scale samples. Therefore, for
example, to grip and hold samples in the context of study, in
particular using electron microscopes, such as transmission
electron microscopes (TEM) or scanning electron microscopes (SEM),
new micro-grippers are used for each sample. Because micro-grippers
are only intended for a single use for purposes of this type, they
are to be producible cost-effectively as mass produced products.
Nonetheless, they must fulfill all the requirements to ensure
reliable gripping and holding in such applications. The
micro-grippers described above are not or are not optimally
suitable for this purpose for the cited reasons, however.
[0013] In addition to the micro-grippers having actuators described
above, a micro-gripper is described in the publication US
2002/0166976 A1, which is particularly also suitable for use for
gripping and holding a sample in the context of studies using TEM.
The micro-gripper described therein comprises a rod-shaped or
cylindrical elongate body, which has one or more receptacle slots
open on three sides on one end in such a way that a sample may be
clamped in the receptacle slot. The accommodation and holding of
the sample is based, as described above, on the elastic deformation
of the material surrounding the receptacle slot and the restoring
force thus caused, which acts on the clamped sample.
[0014] The following method may be inferred from the cited document
for producing the micro-ripper. A piece of linear tungsten wire
having a wire diameter of 50 .mu.m is used as the starting
material. In a first method step, an end area of the tungsten wire
is initially processed using electropolishing or an etching method
in such a way that the tungsten wire tapers in this end area toward
the wire end to a diameter of a few micrometers. In a second work
step, a receptacle slot open on three sides toward the end of the
tapered area is worked out of the now conically tapering end area
of the tungsten wire using an ion beam incident perpendicularly to
the longitudinal axis of the tungsten wire. In a third method step,
in addition to the first receptacle slot, for example, a second
receptacle slot rotated by 90.degree. thereto may be worked out by
a further application of the ion beam. At least two or four
gripping elements, between which an object may be clamped, thus
arise in the tapered end area of the tungsten wire. The receptacle
slot has a width of 2 .mu.m and a depth of 30 .mu.m according to
one exemplary embodiment.
[0015] The micro-gripper disclosed in US 2002/0166976A1 has the
disadvantage that it is not technically possible by the specified
production method to produce the faces adjoining the receptacle
slot, that is, the internal clamping faces on the gripping
elements, exactly parallel to one another. Rather, by applying the
ion beam to produce a receptacle slot, the receptacle slot is wider
on the side facing toward the ion beam than on the side facing away
from the ion beam. The clamping faces defining the slot which are
thus generated are therefore not oriented parallel to one another.
This finally results in an uneven distribution of clamping forces
on the object to be held and has the danger that objects clamped
between the clamping faces may shift in relation to the
micro-gripper. Furthermore, the described method is only suitable
in a limited way, and/or not at all for mass production, because
exact fixing and positioning of the tungsten wire is required
individually for each micro-gripper, before the processing using
the ion beam may be performed, which makes the production method
time-consuming and costly.
[0016] A production method of partially movable microstructures
based on a dry-chemical etched sacrificial layer may be inferred
from DE 195 22 004, the sacrificial layer, which typically
comprises polyimide, being applied directly to a substrate layer,
on which, completely spaced apart from the substrate layer by the
sacrificial layer, a later partially movable micro-structured
material layer is applied, for example, in further implementation
as a cantilever with or without additional tip. For the purposes of
the partial movement capability, the sacrificial layer located
between the cantilever layer and the substrate layer is only
partially removed in the course of a dry-chemical etching method,
so that a residue of sacrificial layer remains in existence as a
type of spacer.
SUMMARY OF THE INVENTION
[0017] Proceeding from the described prior art, it is the object of
the present invention to specify a method for producing a
micro-gripper as well as a micro-gripper, in which the
disadvantages described above are avoided. The micro-gripper is
particularly to be cost-effectively producible as a mass-produced
product, have opposing clamping faces which are oriented parallel
to one another on the gripping elements in the idle state, and be
suitable for accommodating, transporting, and holding material
samples in the context of their study in a TEM or SEM.
[0018] The invention specifies a method for producing a
micro-gripper, which comprises a base body and a gripping body
connected integrally to the base body, which projects beyond the
base body and provides a receptacle slot on a free end area in such
a way that a micrometer-scale or sub-micrometer-scale object may be
clamped in the receptacle slot for gripping and holding. The method
is essentially distinguished in that the base body and the gripping
body are produced using a material deposition method with
implementation of at least one shared first material layer and one
shared second material layer, and the material layers are
implemented as essentially flat and are bonded to one another. The
invention further is a micro-gripper which is distinguished in that
the base body and the gripping body are implemented as a uniform
planar body, which is defined by two essentially flat overlapping
planar body surfaces oriented parallel to one another.
[0019] Features advantageously of the invention may be inferred
from the description, in particular with reference to the exemplary
embodiments.
[0020] An essential concept of the invention is the production of a
micro-gripper using a material deposition method with
implementation of at least two flatly implemented material layers
which are bonded to one another. Methods for depositing material
are known in manifold forms to those skilled in the art. For the
production according to the invention of a micro-gripper, methods
from thin-film technology are especially suitable, by which the
materials may be applied in thin layers, having layer thicknesses
to below 1 .mu.m, to a substrate. In particular, physical vapor
deposition methods (PVD), that is, vapor deposition or sputtering,
chemical vapor deposition methods (CVD), and methods derived
therefrom, such as low-pressure CVD (LPCVD) or plasma-enhanced CVD
(PECVD), or galvanic methods come into consideration for the
deposition of the layers on the substrate. The layers thus
deposited may be subsequently structured by masking or lithography
methods having subsequent material abrasion by applying
wet-chemical etching, reactive ion etching (RIE), sputter etching,
ion beam etching, or plasma etching. Alternatively to the
subsequent structuring of a layer already applied, the structuring
of an applied layer may also be achieved by targeted local material
deposition. Furthermore, by depositing a so-called sacrificial
layer between two material layers and later removing the
sacrificial layer, for example, by wet-etching methods, a nearly
arbitrary three-dimensional structuring may be achieved on the
material layers applied to the substrate. One skilled in the art is
familiar with these technologies and their application.
[0021] If a method described or known in the context of thin-film
technology is used for the production according to the invention of
a micro-gripper, the production method for the micro-gripper
comprises the following method steps in a simple case.
[0022] In a first method step, a flat substrate surface is
provided. A silicon substrate is preferably suitable for this
purpose because of its good surface planarity. In a second method
step, a first sacrificial layer is applied to the substrate
surface. In the third method step, the first material layer is
applied to the first sacrificial layer. In the fourth method step,
the application (and possibly the structuring) of the second
sacrificial layer on the first material layer is performed, at
least on a local area of the first material layer. The predominant
part of the first material layer is typically not covered by the
second sacrificial layer. The second sacrificial layer corresponds
in its external dimensions in its application to the one local area
to the receptacle slot to be produced on the gripping body, so that
the receptacle slot is exposed after a removal of the second
sacrificial layer in this area. In the fifth method step, the
second material layer is applied to the second sacrificial layer
and the areas of the first material layer not covered by the second
sacrificial layer. In the simplest case, the first and the second
material layers are bonded to one another directly with the
exception of the one local area. In the sixth method step, the
first and second sacrificial layers are removed. The removal of the
second sacrificial layer implements the receptacle slot, the
removal of the first sacrificial layer detaches the now completely
produced micro-gripper from the substrate. Wet-chemical etching
methods are suitable in particular for removing the sacrificial
layers.
[0023] As a result of method steps 1-6, a micro-gripper is
obtained, which is distinguished in that the base body and the
gripping body of the micro-gripper are implemented as a uniform
planar body, which is defined by two essentially flat planar body
surfaces oriented parallel to one another and overlapping. The
external free surfaces of the first and second material layers
correspond to the planar body surfaces.
[0024] The receptacle slot on the gripping body preferably has two
internal clamping faces situated parallel to one another, spaced
apart from one another, and overlapping. The clamping faces
preferably have a distance of 10 nm to 10 .mu.m, in particular 50
nm to 1 .mu.m to one another.
[0025] The lateral dimensioning of the planar body surfaces, and
thus the lateral shaping of the base body, the gripping body, and
finally also the clamping faces in the receptacle slot, are
performed by a corresponding structuring of the layers arising in
the context of the material deposition method described. As
described above, the desired structuring of a layer may be
performed by a local, that is, laterally appropriately defined
deposition of the layer or by an appropriate lateral structuring of
an already deposited layer. Corresponding structuring methods are
known to those skilled in the art. By such a structuring of the
layers, it is possible in particular to predefine the lateral
dimensioning of the micro-gripper to be produced nearly arbitrarily
and thus adapt the shape of the base body, the gripping body, and
the clamping faces to the desired requirements.
[0026] By a corresponding structuring of the layers during the
production method, micro-grippers, whose planar body surfaces
completely overlap one another, are preferably produced.
Furthermore, micro-grippers are preferably produced using the
method according to the invention which are dimensioned and
designed in such a way that they may accommodate and hold samples,
which are to be studied using a TEM or SEM, for example, and which
may be inserted directly into a commercially available sample
retainer of a TEM or SEM. Micro-grippers in which the planar body
surfaces correspond to a circular sector having a centerpoint angle
.alpha..ltoreq.180.degree. and the gripping body is situated
projecting beyond a circular sector tip of the circular sector or
whose planar body surfaces correspond to a circular segment having
a centerpoint angle .alpha..ltoreq.180.degree. and the gripping
body is situated on the circular segment chord, in particular in
the center of the circular segment chord, projecting beyond the
circular segment, and the circular segment or the circular sector
has a circle radius which is adapted to the radius of a sample
retainer of a microscope, in particular an SEM or TEM, are
particularly suitable for TEM/SCM applications of this type. For
SEM or TEM, the radius of the sample retainer is typically 1.5
mm.
[0027] In addition, the planar body surfaces may correspond to a
polygon, the gripping body being situated projecting beyond a
peripheral edge of the polygon, or may have further arbitrary
shapes.
[0028] The shape and relative position of the clamping faces on the
receptacle slot is also determined by the structuring of the first
and second material layers. The clamping faces preferably
correspond to a polygon, in particular a rectangle or square, and
completely overlap one another. For special applications, clamping
faces which taper in the direction of the opening of the receptacle
slot are also suitable in particular. Depending on the desired
application, arbitrary further clamping face shapes are also
possible by a corresponding structuring of the first and second
material layers.
[0029] Several further advantageous embodiments are now to be
specified for the production method described up to this point.
Thus, the following materials may be used for the sacrificial
layers: plastic, metal, or in particular silicon oxide. The
following materials may be used for the material layers: plastics,
ceramic, metal, semimetal, or in particular polysilicon. The use of
the specified materials for the sacrificial layers or the material
layers is not arbitrary, however. Appropriate material combinations
which are suitable for described material deposition and
sacrificial layer technologies are known to one skilled in the art.
The pairing of sacrificial layers made of silicon oxide and
material layers made of polysilicon has proven especially
suitable.
[0030] However, the first and the second material layers may also
comprise different materials and thus provide the micro-gripper
according to the invention with special mechanical, electrical,
magnetic, or chemical properties because of the different material
properties of the first and the second material layers.
[0031] Furthermore, it may be advantageous for reasons of method
technology to apply one or more intermediate layers to the
substrate surface before the application of the first sacrificial
layer to the substrate surface. For stabilization and protection,
the possibility additionally exists of applying one or more
stabilization or protective layers to the second material
layer.
[0032] The simultaneous production of a plurality of micro-grippers
on one or more planar substrates is possible in particular using
the method according to the invention. Not only may manufacturing
costs thus be reduced, but rather achievements of the object may
also be implemented which, with high manufacturing precision, allow
nearly arbitrary shaping of the flatly implemented micro-grippers,
with shaping which is easy to change. The micro-grippers according
to the invention are suitable in particular for accommodating,
transporting, and holding material samples in the context of their
study in a TEM or SEM.
BRIEF DESCRIPTION OF THE INVENTION
[0033] The invention is explained for exemplary purposes hereafter
without restriction of the invention on the basis of exemplary
embodiments with reference to the drawings. In the figures:
[0034] FIG. 1 shows an example of a micro-gripper;
[0035] FIGS. 2a, b show accommodation of an object using the
micro-gripper;
[0036] FIGS. 3a, b show the layer buildup of a micro-gripper;
[0037] FIGS. 4a-g show method steps for producing a
micro-gripper;
[0038] FIG. 5 shows isolation of a TEM sample from a substrate
(prior art);
[0039] FIG. 6 shows a micro-gripper having TEM sample;
[0040] FIGS. 7a, b show a micro-gripper having base bodies designed
in the shape of a circular sector; and
[0041] FIG. 8 shows a micro-gripper having a base body designed in
a semicircle.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0042] FIG. 1 shows a perspective view of a micro-gripper 8
produced according to the invention, which is implemented as a
planar body. The planar body 8 comprises a first material layer 3
and a second material layer 4, which is bonded to the first
material layer 3. The planar body 8 may be divided into a base body
area having the associated planar body surface part 7 and a
gripping body area having the gripping elements 1 and 2, between
which the receptacle slot 6 is located. Furthermore, a continuous
gap 6a running transversely to the gripping elements 1, 2 is
provided in the connection area between base body and gripping body
in the micro-gripper 8 shown. This gap is used for improved
introduction of forces which arise by an elastic deformation of the
gripping elements 1, 2 into the material layers 3 and 4. Thin webs
5 are provided on the right side of the micro-gripper 8 shown for
fastening the micro-gripper on the substrate 9. The background for
this is that during the etching process, in which the sacrificial
layers are removed, the danger exists that the micro-gripper 8 may
detach in an uncontrolled way from the substrate 9 and be lost.
This is prevented by the thin webs 5, via which the micro-gripper
still remains connected to the substrate after the etching of the
sacrificial layers, as explained in greater detail hereafter.
[0043] The planar body surface 7 is used as an adapter face, for
example, for receiving the micro-gripper in a handling system
(transport manipulator), or for inserting it into the receptacle
unit of an analysis device (SEM, TEM). In the present case, it has
the form of a polygon. The planar body surface may, however, be
dimensioned optimally in accordance with the specified requirements
in the context of the production method.
[0044] FIGS. 2a and 2b show the mode of operation of the
micro-gripper 8. The gripping body area of the micro-gripper 8
having the gripping elements 1, 2 and the receptacle slot 6 lying
between the gripping elements 1, 2, as well as a material sample 10
on which a bevel 11 is provided, are shown. To accommodate the
material sample 10 using the micro-gripper 8, according to FIG. 2a,
the micro-gripper 8 having the gripping elements 1, 2 is guided
from above to the bevel 11 of the material sample 10. The bevel 11
is used for an optimum friction lock between the gripping elements
1, 2 and the material sample 10. Fundamentally, such a bevel is not
necessary, however. FIG. 2b shows that the gripping elements 1, 2
are pushed over the bevel 11 of the material sample and thus spread
apart. An elastic deformation of the gripping elements 1, 2 is
caused by the spreading, which generates a retention force on the
bevel by reaction. Because of this retention force and the friction
forces acting between the clamping faces of the gripping elements
1, 2 and the bevel 11, holding of the material sample is
achieved.
[0045] The micro-gripper from FIG. 1 is shown in the production
phase after the sacrificial layers have been removed in FIGS. 3a
and 3b. FIG. 3a first shows a view of the micro-gripper 8. The
micro-gripper 8 is connected via the webs 5 to a retention area 20.
Because the retention area 20 is connected fixed to the substrate 9
(not shown) even after the removal of the sacrificial layers, the
micro-gripper 8 completely detached from the substrate 9 is still
held by the retention area 20 via the webs 5. Unintended detachment
or loss of the micro-gripper 8 after the removal of the sacrificial
layers may thus be prevented. The webs 5 only have to be cut
through to isolate the micro-gripper. The number, configuration,
and cross-section (width and height) of the webs 5 are essentially
directed according to the retention force, which is to be absorbed
by the webs. FIG. 3b shows a section through the layer buildup
along section line A-A'. It may be seen clearly that the substrate
9 is still connected fixed to the retention area 20 even after
removal of the sacrificial layers. The micro-gripper 8 comprises
the first material layer 3 and the second material layer 4, which
are connected to one another. The removed sacrificial layers have
exposed the receptacle slot 6 and the gap 6a. The micro-gripper 8
is connected to the retention area 20 via the webs 5, which are
formed on the first material layer.
[0046] FIGS. 4a-4g explain the method for producing the
micro-gripper shown in FIGS. 3a and 3b on the basis of the
step-by-step layer buildup in a cross-sectional illustration along
section line A-A' of FIG. 3a.
[0047] FIG. 4a In a first method step, an intermediate layer 12a
and 12b is applied to a flat substrate 9 made of silicon. This
intermediate layer 12a comprises silicon nitride and is used as an
electrical insulator, the intermediate layer 12b comprises
polysilicon and is used as a starting layer. A first sacrificial
layer 13 made of silicon oxide is now deposited on this
intermediate layer 12. The first sacrificial layer 13 is
subsequently masked. This is performed by applying a photoresist
layer or a similar mask. The masking shape may be worked out by
exposure using an electron beam or using UV light, for example.
[0048] FIG. 4b After the masking has been finished, the first
sacrificial layer 13 is removed at the exposed points using
reactive ion etching (RIE). FIG. 4b shows that the sacrificial
layer 13 is removed at least in the area on which the later
retention area 20 is to be produced.
[0049] FIG. 4c The first material layer 3 made of polysilicon is
then deposited on the first sacrificial layer 13. The first
material layer 3 is also, as described above, provided with a mask
in the desired form and etched by RIE, for example.
[0050] FIG. 4d A second sacrificial layer 14 is applied to the
first material layer 3. This is also provided with a mask and
etched in the desired form. The second sacrificial layer 14
remaining on the first material layer 3 corresponds in its
geometric shapes 14a, 14b, 14c to the receptacle slot 6, the gap
6a, and the interruption of the second material layer 4 at the web
5 (compare FIG. 4e). If a larger cross-section of the web 5 is
desired, the shape 14c may also be dispensed with.
[0051] FIG. 4e The second material layer 4 made of polysilicon is
deposited, masked, and correspondingly etched on the second
sacrificial layer 14. As recognizable in FIG. 4e, the second
material layer 4 is interrupted at the web 5 by the structuring of
the second material layer 4. This is the case if an excessively
large aspect ratio is expected, that is, the height of the web is
greater than the width of the web. In the event of a desired larger
cross-section of the web 5, the shape 14c is dispensed with, and
the second material layer is applied directly to the web. In this
case, the width of the web is not to be less than the height of the
two layers, however.
[0052] FIG. 4f A metal layer 15 is deposited on the second material
layer 4 for stabilization. The metal layer 15 is also structured
accordingly. This deposited metal layer 15 may also be used as a
starting layer for further galvanic depositions. Instead of a metal
layer 15, other materials, such as plastics or semimetals, may also
be used for this purpose.
[0053] FIG. 4g The last method step for producing the micro-gripper
8 comprises removing the first and second sacrificial layers 13, 14
by an etching solution. The selection for removing the sacrificial
layers 13, 14 is directed according to the material which the
sacrificial layers 13, 14 comprise, of course.
[0054] The micro-grippers 8 produced according to the method
according to FIGS. 4a-g may be used for accommodating and holding
objects in the micrometer-range and sub-micrometer-range. A special
application of the micro-gripper is the accommodation of
electron-transparent samples for their subsequent study in a TEM or
SEM. Samples of this type are prepared out of a material to be
studied using the so-called focused ion beam technology (FIB
technology) known to those skilled in the art.
[0055] The typical methods for accommodating a TEM sample 40 of
this type shown in FIG. 5 use a needle 41, which is fastened to the
TEM sample 40 using material deposition. The micro-gripper 8
produced according to the invention, in contrast, allows an
electron-transparent sample 40 produced using FIB technology to be
accommodated using the gripping elements 1, 2 in an FIB preparation
facility corresponding to FIGS. 2a and 2b.
[0056] FIG. 6 shows the micro-gripper 8 and the TEM sample 40
clamped between the gripping elements 1, 2. The TEM sample 40 may
be transferred directly into the TEM and is immediately available
in the correct position for study using the electron beam 53. The
essential advantage of this procedure is that the complicated
so-called lift out process used up to this point is replaced by the
one-time gripping of the TEM sample 40 by the micro-gripper. After
the accommodation of the TEM sample 40, it may be studied together
with the micro-gripper in the TEM. If necessary, after the TEM
sample is accommodated by the micro-gripper, postprocessing of the
TEM sample in the FIB preparation facility is possible.
[0057] Because the width of the receptacle slot 6 of the
micro-gripper 8 may only be varied within a specific range, the TEM
sample 40 is dimensioned using the FIB technology in such a way
that the sample thickness required for holding is achieved on the
later contact face to the micro-gripper 8. The remaining area of
the TEM sample is prepared to the electron transparency required
for the TEM study.
[0058] FIGS. 7a and 7b show a further advantageous embodiment of
the micro-gripper 8 according to the invention. In this example,
the micro-gripper 8 is used in connection with a half ring 70,
which has an internal radius and an external radius. The
micro-gripper 8 has a planar base body in the form of a circular
sector, the gripping body having the TEM sample 40 being situated
on the circular sector tip projecting beyond the circular sector.
The radius of the circular sector of the base body shape is greater
than the internal radius of the half ring 70. The external radius
of the happening 70 and the radius of the circular sector of the
base body are ideally equal. The micro-gripper 8 is accommodated
with the aid of a device, such as a vacuum pipette, and fastened as
shown to the half ring 70 using an adhesive. This half ring 70 may
comprise different materials which are used in TEM analysis. The
gripping elements 1, 2 project beyond the half ring, so that this
configuration is suitable for accommodating TEM samples 40 from a
substrate. FIG. 7b shows a detail enlargement of the acceptance of
such a TEM sample 40 from an appropriately prepared substrate. Of
course, micro-grippers having other shapes may also be fastened to
the half ring 70. The external shape of the base body therefore
does not necessarily have to be similar to a circular section.
[0059] FIG. 8 shows an embodiment of the micro-gripper 8 according
to the invention in which the base body is implemented having a
semicircular planar body surface 7. The radius R of this semicircle
is dimensioned in such a way that the micro-gripper 8 may
subsequently be directly transferred into the sample retainer of
the TEM. The micro-gripper 8 is first held by a receptacle device
31 and the acceptance of the TEM sample 40 is thus performed. This
configuration allows the direct transfer of the micro-gripper 8
into the sample retainer of the TEM, without an additional
adaptation to a semicircular ring having to be performed. If
circular sectors having centerpoint angles <180.degree. are used
instead of the semicircular shape, the retention of the
micro-gripper in the sample retainer of the TE microscope proves
difficult, because the micro-gripper may slip laterally and is thus
not engaged correctly by the clamping nut of the sample
carrier.
LIST OF REFERENCE NUMERALS
[0060] 1, 2 gripping elements [0061] 3 first material layer [0062]
4 second material layer [0063] 5 web [0064] 6, 6a receptacle slot,
gap [0065] 7 planar body surface in the area of the base body
[0066] 8 micro-gripper, flat body [0067] 9 substrate [0068] 10
material sample [0069] 11 bevel [0070] 12 intermediate layer [0071]
13 first sacrificial layer [0072] 14, 14a-c second sacrificial
layer [0073] 15 metal layer, stabilization layer [0074] 20
retention area [0075] 31 receptacle device [0076] 40 TEM sample
[0077] 53 electron beam [0078] 70 half ring
* * * * *