U.S. patent application number 17/357146 was filed with the patent office on 2021-10-21 for mems-sensor.
The applicant listed for this patent is Infineon Technologies AG. Invention is credited to Alfons Dehe, Marc Fueldner, Bernd Goller, Ulrich Krumbein, Gunar Lorenz, Andreas Wiesbauer.
Application Number | 20210323813 17/357146 |
Document ID | / |
Family ID | 1000005682082 |
Filed Date | 2021-10-21 |
United States Patent
Application |
20210323813 |
Kind Code |
A1 |
Lorenz; Gunar ; et
al. |
October 21, 2021 |
MEMS-Sensor
Abstract
A MEMS sensor includes a housing with an interior volume,
wherein the housing has an access port to the interior volume, a
MEMS component in the housing, and a protection structure, which
reduces an introduction of electromagnetic disturbance radiation
with a wavelength in the range between 10 nm and 20 .mu.m into the
interior volume through the access port and reduces a propagation
of the electromagnetic disturbance radiation in the interior
volume.
Inventors: |
Lorenz; Gunar; (Muenchen,
DE) ; Dehe; Alfons; (Villingen Schwenningen, DE)
; Fueldner; Marc; (Neubiberg, DE) ; Goller;
Bernd; (Otterfing, DE) ; Krumbein; Ulrich;
(Rosenheim, DE) ; Wiesbauer; Andreas;
(Poertschach, AT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Infineon Technologies AG |
Neubiberg |
|
DE |
|
|
Family ID: |
1000005682082 |
Appl. No.: |
17/357146 |
Filed: |
June 24, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
16270219 |
Feb 7, 2019 |
|
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17357146 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B81B 7/0064 20130101;
B81B 7/02 20130101; B81B 2203/04 20130101; H04R 19/005 20130101;
B81B 3/0018 20130101; G01L 9/00 20130101; B81B 7/008 20130101; B81B
3/00 20130101; B81B 2201/0257 20130101; B81B 2207/091 20130101;
B81B 2207/11 20130101; H04R 1/023 20130101; H04R 2201/003 20130101;
B81B 2203/0127 20130101; H04R 19/04 20130101 |
International
Class: |
B81B 7/00 20060101
B81B007/00; B81B 3/00 20060101 B81B003/00; B81B 7/02 20060101
B81B007/02; H04R 19/04 20060101 H04R019/04; H04R 1/02 20060101
H04R001/02; G01L 9/00 20060101 G01L009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 1, 2018 |
DE |
102018203098.7 |
Claims
1. A MEMS sensor comprising: a housing with an interior volume,
wherein the housing comprises an access port to the interior
volume; a MEMS component affixed to an interior surface of the
housing, wherein a central portion of the MEMS component is over
the access port; and a protection structure affixed to an exterior
surface of the housing, wherein a central portion of the protection
structure is under the access port.
2. The MEMS sensor of claim 1, wherein the protection structure
comprises a protection layer.
3. The MEMS sensor of claim 1, wherein the protection structure
comprises a plastic or a silicone material.
4. The MEMS sensor of claim 1, further comprising first and second
contact connector areas affixed to an exterior surface of the
housing.
5. The MEMS sensor of claim 1, further comprising an integrated
circuit device affixed to an interior surface of the housing,
wherein the integrated circuit device is electrically coupled to
the MEMS component.
6. The MEMS sensor of claim 5, wherein the MEMS component and the
integrated circuit device are both affixed to a substrate of the
housing.
7. The MEMS sensor as claimed in claim 5, wherein the integrated
circuit device comprises a glop-top material layer.
8. A MEMS sensor comprising: a housing with an interior volume,
wherein the housing comprises a first access port to the interior
volume; a MEMS component affixed to an interior surface of the
housing, wherein a central portion of the MEMS component is over
the first access port; a carrier board affixed to an exterior
surface of the housing, wherein the carrier board comprises a
second access port under the first access port; and a protection
structure affixed to a top surface of the carrier board, wherein a
central portion of the protection structure is under the first
access port and over the second access port.
9. The MEMS sensor of claim 8, wherein the protection structure
comprises a protection layer.
10. The MEMS sensor of claim 8, wherein the protection structure
comprises a plastic or a silicone material.
11. The MEMS sensor of claim 8, further comprising first and second
contact connector areas affixed between the housing and the carrier
board.
12. The MEMS sensor of claim 8, further comprising an integrated
circuit device affixed to an interior surface of the housing,
wherein the integrated circuit device is electrically coupled to
the MEMS component.
13. The MEMS sensor of claim 12, wherein the MEMS component and the
integrated circuit device are both affixed to a substrate of the
housing.
14. The MEMS sensor as claimed in claim 12, wherein the integrated
circuit device comprises a glop-top material layer.
15. A MEMS sensor comprising: a housing with an interior volume,
wherein the housing comprises an access port to the interior
volume; a MEMS component affixed to an interior surface of the
housing, wherein a central portion of the MEMS component is over
the access port; and a protection structure partially embedded in
the housing, wherein the protection structure extends across the
access port.
16. The MEMS sensor of claim 1, wherein the protection structure
comprises a protection layer.
17. The MEMS sensor of claim 1, wherein the protection structure
comprises a plastic or a silicone material.
18. The MEMS sensor of claim 1, further comprising first and second
contact connector areas affixed to an exterior surface of the
housing.
19. The MEMS sensor of claim 1, further comprising an integrated
circuit device affixed to an interior surface of the housing,
wherein the integrated circuit device is electrically coupled to
the MEMS component, and wherein the integrated circuit device
comprises a glop-top material layer.
20. The MEMS sensor of claim 5, wherein the MEMS component and the
integrated circuit device are both affixed to a substrate of the
housing.
Description
[0001] This application is a divisional of U.S. patent application
Ser. No. 16/270,219, filed Feb. 7, 2019, which application claims
the benefit of German Application No. 102018203098.7, filed on Mar.
1, 2018, which applications are hereby incorporated herein by
reference.
TECHNICAL FIELD
[0002] Exemplary embodiments relate to a MEMS sensor or MEMS
assembly. In particular, exemplary embodiments relate to a
protection structure for a MEMS sensor for at least reducing the
influence of electromagnetic disturbance radiation with a
wavelength in the range between 10 nm and 20 .mu.m, for example, on
a MEMS component arranged in the housing and/or an integrated
circuit arrangement arranged in the housing.
BACKGROUND
[0003] Acoustic MEMS sensors, such as MEMS microphones or pressure
sensors, for example, are open components and exposed to the
ambient surroundings due to the functioning thereof in order, for
example, to be able to capture sound level changes, pressure
changes, etc., in the surroundings. Hence, such MEMS sensors are
often exposed to the external ambient electromagnetic radiation,
too. In general, MEMS sensors comprise a MEMS component such as a
MEMS microphone, for example, arranged on a substrate, said MEMS
component being surrounded by a housing. The housing should protect
the MEMS component from the ambient conditions. Often, the
substrate or the printed circuit board (PCB) and the cover (lid)
usually already have a protection by metallization or a metal
layer. By way of example, external electromagnetic radiation, such
as, for example, natural sunlight, artificial light, e.g., from
halogen spots, etc., infrared radiation, e.g., from IR remote
controls, etc., can penetrate into the housing through the sound
port, with a disturbance in the output signal of the MEMS component
possibly being caused by the introduced constant, or else pulsed,
radiation.
[0004] Thus, in summary, it is possible to note that acoustic
sensors, such as MEMS sound transducers or MEMS microphones, for
example, are susceptible to electromagnetic radiation that can
penetrate into the sensor, in particular through the sound port. On
account of electrical disturbances or interferences, this
electromagnetic disturbance radiation can lead to reduced
capability of the acoustic sensor. During practical operation,
signal artifacts may occur within the "audible" bandwidth (audio
bandwidth) of the sensor output signal.
SUMMARY
[0005] Since there is a constant need for MEMS sensor components
such as, for example, MEMS sound transducers, MEMS microphones or
MEMS pressure sensors, etc., which capture the desired measurement
results such as, for example, acoustic signals or pressure changes
with a sufficiently high accuracy in the field of the sensors,
there is a need for the influence of electromagnetic disturbance
radiation on the MEMS sensor or the MEMS component to be
reduced.
[0006] Such a need can be satisfied by the subject matter of the
present independent patent claims. Developments of the present
concept are defined in the dependent claims.
[0007] A MEMS sensor comprises a housing with an interior volume,
wherein the housing has an access port to the interior volume, a
MEMS component in the housing, and a protection structure, which is
embodied to at least reduce an introduction of electromagnetic
disturbance radiation X.lamda. with a wavelength in the range
.DELTA..lamda. between 10 nm and 20 .mu.m into the interior volume
through the access port and/or at least reduce a propagation of the
electromagnetic disturbance radiation X.lamda. in the interior
volume.
[0008] According to exemplary embodiments, the MEMS sensor, which,
for example, is embodied as an acoustic sound transducer or
pressure sensor, etc., has a MEMS component adjacent to an access
or sound port provided in the housing, wherein a protection
structure is provided on the housing in order to at least reduce
the influence of external electromagnetic disturbance radiation
with a wavelength in, for example, the visible range, UV range or
IR range on a MEMS component arranged in the housing and/or on an
integrated circuit device arranged in the housing. Thus, a
protection structure can be provided on the sound port of the
housing in order to at least reduce penetration of the
electromagnetic disturbance radiation into the interior volume
through the sound port. According to one exemplary embodiment, the
protection structure can also be arranged, alternatively or
additionally, within the interior volume of the housing in order to
at least reduce a propagation of the electromagnetic disturbance
radiation in the interior volume.
[0009] According to exemplary embodiments, the protection structure
can be effectively embodied on the sound port in such a way that
the sound port is substantially transmissive to an acoustic signal
and substantially opaque to the electromagnetic disturbance
radiation.
[0010] By way of example, the protection structure, as a protection
layer against electromagnetic disturbance radiation, can be
arranged spatially close to the sound port of the housing of the
sound transducer, wherein this protection layer has small acoustic
openings or perforation openings, for example, in order firstly to
allow the sound to substantially penetrate into the interior volume
of the housing of the MEMS sensor, i.e., allow at least 50%, 80% or
99% of said sound to penetrate, but, secondly, to be substantially
opaque to the electromagnetic disturbance radiation, i.e., stop at
least 50%, 80% to 99% of said electromagnetic disturbance
radiation. A protection structure that is opaque to the
electromagnetic disturbance radiation can have a reflecting or
absorbing embodiment in the predetermined wavelength range. A
protection structure or layer structure that reflects at least 50%,
80% or 99% of the incident disturbance radiation is considered to
be reflective.
[0011] According to one exemplary embodiment, the protection
structure can be further arranged within the interior volume of the
housing in order to absorb to the best possible extent the
(residual) electromagnetic disturbance radiation that has
penetrated into the interior volume. The protection structure or
layer structure that actually absorbs at least 50%, 80% or 99% of
the incident electromagnetic disturbance radiation can be assumed
to be absorbent.
[0012] Further, the protection layer can be arranged at
predetermined regions within the interior volume of the housing in
such a way as to protect the MEMS component arranged in the
interior volume, or else electric or integrated circuit elements
arranged therein, from the electromagnetic disturbance radiation by
virtue of the protection structure being arranged on the elements
and being embodied to be reflective or absorbent for the
electromagnetic disturbance radiation in the wavelength range.
[0013] By way of example, opaque glop-top materials can be used on
the component plane in order to protect sensitive ASIC structures,
wherein, depending on the specific geometries and the light source,
all sensitive regions on the ASIC are covered by the protection
structure in the form of glop-top material
(disturbance-radiation-opaque silicone). Moreover, the protection
structure can effectively prevent the MEMS component, i.e., the
MEMS chip or MEMS die, from taking up electromagnetic radiation
directly via the thermoelectric effect or else indirectly via the
thermomechanical or thermoacoustic effect. As a result,
interferences in the audible bandwidth range of the sensor output
signal can be prevented or at least reduced. By preventing
disturbances in the audio bandwidth of the sensor output signal, it
is possible to maintain a high signal-to-noise ratio (SNR) of the
MEMS sensor.
[0014] Consequently, according to exemplary embodiments, the
protection structure, for example with a layer-shaped embodiment,
can be arranged as part of the outer sound port, as integrated part
of the sound port, as part of the front cavity (of the front
volume), as part of the MEMS component, as part of the interior
region or interior volume of the housing, as part of the ASIC or
the ASIC arrangement, as part of the design of the housing and/or
as part of the design of a carrier board for assembling the
housing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Exemplary embodiments of apparatuses and/or methods are
described in more detail below in exemplary fashion, with reference
being made to the attached figures and drawings. In the
drawings:
[0016] FIG. 1 shows a schematic diagram in a cross-sectional view
of a MEMS sensor with an exemplary illustration of different
protection structures according to configurations A-G as per
exemplary embodiments;
[0017] FIG. 2 shows a schematic diagram in a cross-sectional view
of a MEMS sensor with a protection structure according to
configuration A as per one exemplary embodiment;
[0018] FIG. 3 shows a schematic diagram in a cross-sectional view
of a MEMS sensor with a protection structure according to
configuration A as per one exemplary embodiment;
[0019] FIG. 4 shows a schematic diagram in a cross-sectional view
of a MEMS sensor with a protection structure according to
configuration B as per one exemplary embodiment;
[0020] FIGS. 5a-5b in each case show a schematic diagram in a
cross-sectional view of a MEMS sensor with a protection structure
according to configuration C as per one exemplary embodiment;
[0021] FIG. 6 shows a schematic diagram in a cross-sectional view
of a MEMS sensor with a protection structure according to
configuration D as per one exemplary embodiment;
[0022] FIGS. 7a-7b, in each case show a schematic diagram in a
cross-sectional view of a MEMS sensor with a protection structure
according to configuration E as per one exemplary embodiment;
[0023] FIGS. 8a-8b in each case show a schematic diagram in a
cross-sectional view of a MEMS sensor with a protection structure
according to configurations F and G as per one exemplary
embodiment;
[0024] FIGS. 9a-9b in each case show a schematic diagram in a
cross-sectional view of a MEMS sensor with a protection structure
according to a configuration H as per one exemplary embodiment;
and
[0025] FIGS. 10a-10f show a plurality of graphical illustrations of
the optical properties of different materials for the protection
structure according to one exemplary embodiment.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0026] Before exemplary embodiments are described more closely in
detail in the figures below, reference is made to the fact that
identical, functionally identical or similarly acting elements,
objects, functional blocks and/or method steps are provided with
the same reference sign in the various figures such that the
description, illustrated in the various exemplary embodiments, of
these elements, objects, functional blocks and/or method steps is
interchangeable among one another or can be applied to one
another.
[0027] Various exemplary embodiments will now be described in more
detail, with reference being made to the attached figures, which
illustrate some exemplary embodiments. In the figures, the
strengths of lines, layers and/or regions may, for elucidation
purposes, not be illustrated true to scale.
[0028] Below, a MEMS sensor 100 with a MEMS component 110 and an
optional, integrated circuit device 120 (ASIC=application-specific
integrated circuit), which is electrically coupled to the MEMS
component 110, for example, is described on the basis of FIG. 1 in
the form of a schematic diagram in a cross-sectional view,
including an exemplary illustration of different protection
structures 140 according to different configurations A-G.
[0029] By way of example, the MEMS component 110 can be embodied as
a MEMS sound transducer. However, reference is made to the fact
that the explanations below are equally applicable to all MEMS
components, such as sound transducers, pressure sensors, etc.,
which are housed in a housing 130.
[0030] As illustrated in FIG. 1 in exemplary fashion, the MEMS
component 110 can be arranged in a housing 130 with an interior
volume V, with the housing 130 having an access or sound port 132
to the interior volume V, for example. The MEMS component 110 is
arranged in the housing, for example adjacent to the sound port
132. Now, the MEMS sensor 100 further has a protection structure
140, which is embodied to at least reduce penetration of
electromagnetic disturbance radiation X.lamda. with a wavelength in
a range .DELTA..lamda. between 10 nm and 20 .mu.m into the interior
volume V through the sound port 132 and/or to at least reduce a
propagation of the electromagnetic radiation X.lamda. in the
interior volume V.
[0031] As illustrated in FIG. 1, the protection structure 140 can
have or adopt a number of different configurations A-H, which are
specified together in an exemplary fashion in the schematic diagram
in FIG. 1. In respect of the different configurations A-H of the
protection structure 140 illustrated in FIG. 1, reference is made
to the fact that the protection structure 140 according to the
exemplary embodiments can be embodied individually in each case
according to one of the illustrated embodiments A-H, or else in a
combination of at least two (or else all) of the illustrated
embodiments A-H. According to exemplary embodiments, as illustrated
in FIG. 1, the protection structure 140 can be embodied as part of
the external sound port according to configuration A, as an
integrated part of the sound port according to configuration B, as
part of the front cavity (front volume) according to configuration
C, as part of the MEMS component according to configuration D, as
part of the interior housing according to configuration E, as part
of the circuit device (ASIC or ASIC arrangement) according to
configuration F, as part of the substrate design and/or the ASIC
arrangement according to configuration G and/or as part of a
carrier board in combination with the housing substrate according
to configuration H.
[0032] According to exemplary embodiments, the protection structure
or protection layer 140 can have at least one or more of the
properties set forth below. By way of example, the protection
structure 140 can have an acoustically transparent embodiment that
is reflective for the disturbance radiation in the desired
wavelength range, for example in a range .DELTA..lamda. between 10
nm and 20 .mu.m, and/or it can be embodied to be absorbent in the
desired frequency range of the electromagnetic disturbance
radiation. Consequently, the wavelength range .DELTA..lamda. of the
electromagnetic disturbance radiation can comprise visible light
(e.g., sunlight), UV (ultraviolet) light and/or IR (infrared)
light. By way of example, typical IR light sources are IR remote
controls, TOF (time-of-flight) sensors, etc. Consequently, the
protection structure 140 can be embodied to selectively reflect
and/or absorb a predetermined wavelength range of visible light, UV
radiation or IR radiation.
[0033] By way of example, a reflecting protection structure or
layer structure 140 can be embodied as a metal layer or as a
so-called Bragg reflector. By way of example, reflecting metal
materials in the form of a metal layer or a metal ply, e.g. a metal
ply applied by sputtering, applied on a base material can be
considered as reflecting materials. The thickness of such applied
metal plies can lie in the region of several atomic layers, i.e.,
for example, of the order of 0.1 nm or between 0.5 nm and 10 nm.
Further, use can be made of so-called "Bragg filter structures" or
Bragg mirrors with a relatively high wavelength selectivity. By way
of example, Bragg mirrors consist of alternating, dielectric thin
layers with a low and high refractive index.
[0034] By way of example, an absorbing layer structure or
protection structure 140 can have a disturbance-radiation-opaque or
absorbing plastic or silicone material (e.g., dark or black
glop-top material).
[0035] Terms for layers or layer structures used within the scope
of the present description comprise both individual layers and
multi-ply layers (layer stacks), which together form a resultant
layer structure, for example.
[0036] The description of the light-opaque protection structures
140, i.e., the protection structures 140 reflecting or absorbing
electromagnetic disturbance radiation in the wavelength range
.DELTA..lamda., is equally applicable to all exemplary
embodiments.
[0037] In respect to the specific configuration of the protection
structure 140 according to configurations A-H, reference is made in
detail to the following description, with reference being made to
FIGS. 2 to 9a-9b.
[0038] Below, general, exemplary configurations of the MEMS sensor
100 are discussed further, said exemplary configurations being
equally applicable to the exemplary embodiments according to
configurations A-H of the protection structure 140 in subsequent
FIGS. 2 to 9a-9b and the associated description.
[0039] Now, for example, the housing 130 of the MEMS sensor 100 can
have a substrate 134 and a covering element 136, which can, at
least in regions, have an electrically conductive embodiment. Now,
for example, the carrier substrate 134 can have a conductive layer
structure (e.g., wiring plane) 138, which may be electrically
connected to the electrically conductively embodied portion of the
covering element 136, for example. Further, the carrier substrate
134 can have contact connector areas (solder pads) 139 in order to
mechanically and/or electrically connect the housing 130 to an
optional carrier board 150 which, for example, can have a sound
port 152 in turn. Now, for example, the carrier board 150 can have
a conductive layer structure (e.g., wiring plane) 154. The carrier
board 150 for the MEMS sensor 100 or the MEMS sensor module can be
embodied as a flex board or main board.
[0040] In an exemplary arrangement as a MEMS sound transducer, the
MEMS component 110 can subdivide the volume V into a front volume
V.sub.1 and a back volume V.sub.2, with the front volume V.sub.1
being situated in the region between the sound port 132 and the
MEMS sound transducer 110 and the back volume V.sub.2 being
situated in the interior volume V of the housing 130 on the side of
the MEMS sound transducer 110 lying opposite thereto.
[0041] Thus, according to one exemplary embodiment, the MEMS
component 100 comprises a MEMS sound transducer 110 with a membrane
structure 114 and an associated counter electrode structure 112,
and further an integrated circuit device 120, which is electrically
coupled to the MEMS sound transducer 110. On an upper surface
region 120-1, the circuit device 120 can have a radiation-absorbing
layer 122 with a light-opaque silicone glop-top material, for
example. Thus, silicone material (glop-top material) that is opaque
to the wavelength of the electromagnetic disturbance radiation can
be arranged on the upper surface region 120-1 of the electric
circuit device 120, for example. The circuit device 120 can be
further embodied to capture and output an audio output signal
S.sub.out of the MEMS sound transducer 110 on the basis of a
deflection of the membrane structure 114 in relation to the counter
electrode structure 112, brought about by the acoustic sound
pressure change .DELTA.P.
[0042] According to exemplary embodiments, the covering element 136
further can be embodied in electrically conductive fashion and can
be electrically coupled or connected to the conductive structure
138 of the substrate 134 in order to be able to electrically
connect the covering element 136 to a reference potential, e.g.,
ground potential, for example.
[0043] Thus, the MEMS component 110 can be embodied as a MEMS sound
transducer or MEMS microphone with the membrane structure 114 and
the assigned counter electrode structure 112, and can be
electrically coupled to the integrated circuit device 120 (ASIC) in
order to provide a corresponding audio output signal S.sub.out on
the basis of an incident acoustic sound pressure change .DELTA.P
and the deflection between the membrane structure 114 and the
counter electrode structure 112 resulting therefrom.
[0044] According to one exemplary embodiment, the MEMS component
110, which is embodied as a MEMS microphone, for example, can have
a further counter electrode structure (not shown in FIG. 1) and
consequently can be embodied as a dual backplate configuration,
i.e., in a configuration with two counter electrode structures and
the membrane structure lying therebetween.
[0045] According to a further exemplary embodiment, the MEMS
component 110, which is embodied as a MEMS microphone, can have a
further membrane structure (not shown in FIG. 1), which is
mechanically connected to the first membrane structure, for example
by mechanical connection elements (not shown in FIG. 1), in order
to form a so-called dual membrane configuration, i.e., a
configuration with two membrane structures and a counter electrode
structure lying therebetween.
[0046] A MEMS sensor 100 with the MEMS component 110 housed in the
housing 130 is now described below on the basis of FIG. 2, in the
form of a schematic diagram in a cross-sectional view, wherein the
protection structure 140 according to configuration A is embodied
on the sound port 132 of the substrate 134 in such a way that the
sound port 132 is transmissive to an acoustic signal .DELTA.P
(within a tolerance range) and opaque to the electromagnetic
disturbance radiation X.lamda. (within a tolerance range). The
protection structure 140 can have a reflecting or absorbing
embodiment for the electromagnetic disturbance radiation X.lamda.
in the wavelength range .DELTA..lamda.. The protection structure
140 that is reflective for the electromagnetic disturbance
radiation X.lamda. in the wavelength range can be embodied as a
reflecting layer element with a metal layer or a Bragg reflector.
Consequently, the protection structure 140 can be arranged on the
outer side of the housing 130 as a plate-shaped or layer-shaped
protection element and can at least partly, or else completely,
cover the sound port 132.
[0047] If the protection structure 140 with a layer-shaped
embodiment according to configuration A has a conductive
embodiment, the protection structure 140 can be further
electrically coupled or connected to the conductive structure 138
of the substrate 134 in order also to be able to electrically
connect the conductive protection structure 140 to the reference
potential, e.g., ground potential.
[0048] Now, a further exemplary embodiment of the protection
structure 140 according to configuration A is described in
exemplary fashion below on the basis of FIG. 3, which is in the
form of a schematic diagram in a cross-sectional view of the MEMS
sensor 100.
[0049] As illustrated in FIG. 3, the housing 130 or the carrier
substrate 134 of the housing 130 is arranged on the carrier board
150, i.e., electrically and/or mechanically connected to same,
wherein the carrier board 150 has the carrier board sound port 152.
The protection structure 140, embodied in layer-shaped fashion in
an exemplary manner, is arranged between the sound port 132 of the
housing 130 and the carrier board sound port 152 of the carrier
board 150.
[0050] According to one exemplary embodiment, the electrically
conductive protection structure 140 can also be electrically
coupled or connected to an electrically conductive structure or
metallization plane 154 of the carrier board 150 in order to be
able to electrically connect the conductive protection structure
140, for example with a layer-shaped embodiment, according to
configuration A to the reference potential, e.g., ground
potential.
[0051] Now, an exemplary embodiment of the protection structure 140
according to configuration B is described in exemplary fashion
below on the basis of FIG. 4, which is in the form of a schematic
diagram in a cross-sectional view of the MEMS sensor 100.
[0052] As illustrated in FIG. 4, the protection structure 140 can
be embedded in the housing 130 or in the substrate 134 of the
housing 130 within the sound port 132 and can be embodied to be
transmissive to the acoustic sound signal .DELTA.P (within the
tolerance range) and opaque to the electromagnetic disturbance
radiation X.lamda. in the wavelength range .DELTA..lamda. (within
the tolerance range). The protection structure 140 can have a
reflecting or absorbing embodiment in relation to the
electromagnetic disturbance radiation X.lamda. in the wavelength
range .DELTA..lamda.. The protection structure 140 that is
reflective for the electromagnetic disturbance radiation X.lamda.
in the wavelength range can be embodied as a reflecting layer
element with a metal layer or a Bragg reflector. Consequently, the
protection structure 140 can be arranged on the outer side of the
housing 130 as a plate-shaped or layer-shaped protection element
and can at least partly, or else completely, cover the sound port
132.
[0053] If the protection structure 140 with a layer-shaped
embodiment according to configuration B has a conductive
embodiment, the protection structure 140 can be further
electrically coupled or connected to the conductive structure 138
of the substrate 134 in order also to be able to electrically
connect the conductive protection structure 140 to the reference
potential, e.g., ground potential.
[0054] Now, a MEMS sensor 100 with a further exemplary embodiment
of the protection structure 140 according to configuration "C" is
described in exemplary fashion below on the basis of FIGS. 5a-5b in
the form of a schematic diagram in a cross-sectional view.
[0055] As illustrated in FIGS. 5a-5b, the protection structure 140
according to configuration "C" with a layer-shaped embodiment, for
example, is arranged at the sound port 132 on the inner side of the
housing 130 facing the interior volume V.sub.1, wherein the sound
port 132 can be at least partly, or else completely, covered by the
protection structure 140. In the configuration of the protection
structure 140 illustrated in FIG. 5a, a protection layer structure
is arranged on the carrier substrate 134 within the interior volume
V or the front volume V.sub.1.
[0056] The protection structure 140 at the sound port 132 of the
housing 130 is embodied to be transmissive to the acoustic sound
signal .DELTA.P (within the tolerance range) and opaque to the
electromagnetic disturbance radiation X.lamda. in the wavelength
range .DELTA..lamda. (within the tolerance range). The protection
structure 140 can have a reflecting or absorbing embodiment for the
electromagnetic disturbance radiation X.lamda. in the wavelength
range .DELTA..lamda.. The protection structure 140 that is
reflective for the electromagnetic disturbance radiation X.lamda.
in the wavelength range can be embodied as a reflecting layer
element with a metal layer or a Bragg reflector. Consequently, the
protection structure 140 can be arranged on the outer side of the
housing 130 as a plate-shaped or layer-shaped protection element
and can at least partly, or else completely, cover the sound port
132. If the protection structure 140 with a layer-shaped embodiment
according to configuration C has a conductive embodiment, the
protection structure 140 can be further electrically coupled or
connected to the conductive structure 138 of the substrate 134 in
order also to be able to electrically connect the conductive
protection structure 140 to the reference potential, e.g., ground
potential.
[0057] In configuration "C" of the protection structure 140
illustrated in FIG. 5b, the protection structure 140 can have a
layer or layer structure that is opaque to the electromagnetic
disturbance radiation X.lamda., said layer or layer structure being
arranged on the inner side of the housing 130, i.e., arranged on
the carrier substrate 134 within the interior volume V or the front
volume V.sub.1, by a spacer element 142. Thus, the configuration of
the protection layer 140 illustrated in FIG. 5b can once again have
an acoustically transparent embodiment and an embodiment that
reflects the electromagnetic disturbance radiation X.lamda. in the
wavelength range .DELTA..lamda., e.g., as a metal layer and/or
Bragg reflector, and/or absorbs said electromagnetic disturbance
radiation, for example having a dark or black silicone material,
like the layer-shaped protection structure 140 illustrated in FIG.
5a.
[0058] According to a further exemplary embodiment, the protection
structure 140 with the layer-shaped embodiment according to
configuration "C" in FIG. 5b need not necessarily be acoustically
transparent as lateral acoustic openings can be realized through
the spacer element or the spacer elements 142 (on the sidewall
range of same) in order to obtain the acoustic transmissivity.
Consequently, the protection structure 140 can yield a separation
of the acoustic path into the interior volume V of the housing 130
from the "blocked" radiation path.
[0059] Now, a further exemplary embodiment of the protection
structure 140 according to configuration "D" is described in
exemplary fashion below on the basis of FIG. 6, which is in the
form of a schematic diagram in a cross-sectional view of a MEMS
sensor 100.
[0060] In the component or MEMS sound transducer 110 of the MEMS
sensor 100 illustrated in FIG. 6, reference is made to the fact
that the counter electrode structure 114 is arranged adjacent to
the front volume V.sub.1 or adjacent to the sound port 132.
Alternatively, the arrangement of the membrane structure 114 and
the counter electrode structure 112 can also be interchanged such
that the counter electrode structure 112 is also arranged adjacent
to the front volume V.sub.1 or the sound port 132. Consequently,
the counter electrode structure 112 or membrane structure 114
facing the sound port 132 can be referred to as a microphone layer
structure 112, 114 in general. Consequently, the protection
structure 140 is arranged at a surface of the microphone layer
structure 112, 114 of the MEMS component 110 facing the sound port
132 and embodied to be opaque, at least in regions, to the
electromagnetic disturbance radiation X.lamda. in the wavelength
range .DELTA..lamda. and, however, embodied to be transparent to
the acoustic signal .DELTA.P. Thus, the surface of the microphone
layer structure 112, 114 of the MEMS component 110 facing the sound
port 132 can be provided, at least in regions, with a reflecting
layer element as a protection structure 140 for reflecting
disturbance radiation or with a material that absorbs the
electromagnetic disturbance radiation as a layer structure 140.
[0061] According to configuration "D" of the protection structure
140, the protection structure 140 itself is part of the MEMS
component 100. According to one exemplary embodiment, the
microphone layer structure in the form of the counter electrode
structure 112 and/or the membrane structure 114 can be coated with
a metal layer that is reflective for the electromagnetic
disturbance radiation in the wavelength range .DELTA..lamda.. The
metal layer or metal ply can be applied to the microphone layer
structure 112, 114, for example by sputtering. According to a
further exemplary embodiment, the arrangement with the membrane
structure 114 and/or the counter electrode structure 112 can be
embodied as a Bragg reflector in each case or can be embodied, for
example, as a Bragg resonator together with the interposed air gap
115. The explanations made above are equally applicable if use is
made of a so-called "double membrane configuration" or a double
counter electrode configuration of the MEMS component 110.
[0062] According to a further exemplary embodiment, the microphone
layer structure 112, 114, such as the counter electrode structure
112 and/or the membrane structure 114, for example, can have a
material that absorbs the radiation of the electromagnetic
disturbance radiation X.lamda. or an additional radiation-absorbing
layer.
[0063] Now, a further exemplary embodiment of the protection
structure 140 according to configuration "E" is described below on
the basis of FIGS. 7a-7b, which are in the form of a schematic
diagram in a cross-sectional view of a MEMS sensor 100.
[0064] As illustrated in FIGS. 7a-7b, the protection structure 140
according to configuration "E" is arranged on a surface region
136-1 of the housing 130, facing the interior volume V, in the form
of an absorbing layer or layer structure and it has an absorbing
embodiment in relation to the electromagnetic disturbance radiation
X.lamda., for example in the wavelength range .DELTA..lamda.. The
absorbing protection structure or layer structure 140 according to
configuration "E" can consequently be arranged on the inner surface
region 136-1 of the covering element 136, at least in regions.
[0065] As illustrated in FIG. 7a, the protection structure 140 is
only arranged on the inner upper side of the covering element 136,
while the layer structure 140 in FIG. 7b is arranged on the entire
interior surface region 136-1 of the covering element 136.
[0066] According to one exemplary embodiment, the layer structure
140 with a layer-shaped embodiment can also be arranged on the
interior surface region 134-1 of the carrier substrate 134, at
least in regions or else completely, in addition or as an
alternative to the arrangement on the surface region 136-1 (not
shown in FIGS. 7a-7b).
[0067] Further, the protection structure 140 with a layer-shaped
embodiment according to configuration "E" can have different layer
thicknesses in different interior surface regions 136-1 of the
covering element 136; i.e., proceeding from the first layer
thickness di of approximately 10 .mu.m, e.g., between 5 and 20
.mu.m, in a first surface region, it can further have an increased
second layer thickness d2 of approximately 20 .mu.m, e.g., between
10 and 50 .mu.m, with d2>d1, in a further surface region
adjacent to the integrated circuit device 120, for example.
[0068] According to the exemplary embodiments of the layer
structure 140 according to configuration "E", illustrated in FIGS.
7a-7b, the layer structure 140 is part of the interior housing 130.
The layer structure or protection layer 140 is arranged, at least
in regions, on the inner surface 134-1, 136-1 of the carrier
substrate 134 and of the covering element 136 of the housing 130,
respectively. According to one exemplary embodiment, the layer
structure 140, embodied as an absorbing layer, can be embodied as a
dark or black silicone material (glop-top material) in the relevant
wavelength range .DELTA..lamda. of the electromagnetic disturbance
radiation X.lamda.. According to further exemplary embodiment, the
lateral dimension (area) and/or vertical dimension (thickness) of
the protection structure 140 embodied in layer-shaped manner can be
varied further in order to be able to adapt the protection function
as effectively as possible. Thus, the protection structure 140 with
the layer-shaped embodiment can be arranged on the inner surface
134-1, 136-1 of the housing 130, either in regions or completely.
Further, the thickness of the protection structure 140 with a
layer-shaped embodiment can have different embodiments at different
interior surface regions of the housing 130 in order to effectively
obtain the protective effect in relation to the electromagnetic
disturbance radiation.
[0069] Now, further exemplary embodiments of the protection
structure 140 according to configurations "F" and "G" are described
in exemplary fashion below on the basis of FIGS. 8a-8b, which are
in the form of a schematic diagram in a cross-sectional view of the
MEMS sensor 100.
[0070] As illustrated in FIGS. 8a-8b, the MEMS sensor further has
the integrated circuit 120 in the interior volume V of the housing
130, e.g., on the carrier substrate 134, wherein the protection
structure 140 according to configurations F and G is arranged at
least on a portion of the surface, e.g., the upper surface 120-1,
the side face 120-2 or the base (adjacent to the carrier substrate
134) of the integrated circuit device 120, and embodied to be
opaque to electromagnetic disturbance radiation X.lamda. in the
predetermined wavelength range .DELTA..lamda..
[0071] According to one exemplary embodiment, the protection
structure 140 further can have a layer-shaped embodiment and, at
the base region 120-3, the integrated circuit device 120 can be
arranged neighboring or adjacent to the carrier substrate 134 of
the housing 130, at least in regions.
[0072] Thus, the protection structure 140 with a layer-shaped
embodiment can have a reflecting and/or absorbing embodiment for
the electromagnetic disturbance radiation X.lamda. in the
wavelength range .DELTA..lamda.. Thus, the protection structure 140
can at least partly, or else completely, cover the surface region
120-1, 120-2, 120-3 of the integrated circuit device 120, wherein
the protection structure 140 has a layer-shaped embodiment and an
embodiment that is opaque to the electromagnetic disturbance
radiation X.lamda.. In particular, the layer structure 140 can have
a layer-shaped embodiment and can be arranged on the sidewall
region 120-2 of the integrated circuit device 120, as is
illustrated in FIGS. 8a-8b, for example.
[0073] Further, the layer-shaped protection structure 140 on the
sidewall region 120-2 of the integrated circuit device 120 can
extend into the housing 130 or into the carrier substrate 134 as
far as a metallization structure 138 arranged there, as is
illustrated in FIG. 8b, for example. In this way, unwanted input
coupling of electromagnetic disturbance radiation into the
semiconductor material of the integrated circuit 120 via the
material of the carrier substrate 134 can also be suppressed
laterally, for example, by virtue of the metallization structure or
metallization plane 138 arranged in the carrier substrate 134
additionally facilitating vertical shielding in relation to the
disturbance radiation X.lamda., for example.
[0074] Thus, the carrier material or the solder mask of the carrier
substrate 134 can be transparent to certain wavelengths of the
external electromagnetic disturbance radiation, for example, while
the embedded metal layer 138 in the carrier substrate 134 is opaque
to the electromagnetic disturbance radiation in general. The
protection structure 140 with the layer-shaped embodiment on the
sidewall region 120-2 of the integrated circuit, which is formed
into the material of the carrier substrate 134 as far as the
metallization structure 138 arranged there, can provide effective
electromagnetic shielding of the side region 120-2 and the lower
side 120-3 of the integrated circuit arrangement 120. Further, the
protection structure 140 with the layer-shaped embodiment
illustrated in FIG. 8a can be embodied on the base region 120-3 of
the integrated circuit device 120, adjacent to the housing, as an
effective electromagnetic shield on the lower side of the
integrated circuit device 120.
[0075] According to exemplary embodiments, the protection structure
140, embodied as a protection layer, according to configurations F
and G can be embodied to be reflective for the predetermined
frequency range of the disturbance radiation, i.e., as metal layer
or a Bragg reflector, for example, or embodied to be absorbent for
the frequency range of the disturbance radiation, e.g., in the form
of the disturbance-radiation-opaque silicone material, as
illustrated in FIGS. 8a-8b in exemplary fashion.
[0076] Further, the layer-shaped protection structure 140 according
to a configuration F can be embodied laterally into the material of
the carrier substrate 134 and, for example, as far as the
metallization plane 138 on the sidewall region 120-2 of the
integrated circuit device 120. This configuration F of the
layer-shaped protection structure 140 on the sidewall region 120-2
of the integrated circuit device 120 can be obtained by virtue of
adding a depression or a groove into the carrier substrate 134 or
the solder mask, on which the integrated circuit device 120 (ASIC)
is arranged or which surrounds the integrated circuit device 120
(ASIC), and so the protection structure 140 embodied as a
protection layer can extend on the side face 120-2 of the
integrated circuit device 120 as far as the conductive layer 138 in
the carrier substrate 134, as illustrated in FIG. 8b.
[0077] Now, a further exemplary embodiment of the protection
structure 140 according to configuration "H" is described in
exemplary fashion below on the basis of FIGS. 9a-9b, which are in
the form of a schematic diagram in a cross-sectional view of the
MEMS sensor 110.
[0078] As illustrated in FIGS. 9a-9b, the MEMS sensor 100, at the
carrier substrate 134 of the housing 130, is mechanically and
optionally electrically coupled to a further carrier board 150,
wherein the carrier board 150 has a sound port 152. As illustrated
in FIGS. 9a-9b, the sound port 152 of the carrier board 150 is
arranged laterally offset (parallel to the main surface 134-1 of
the carrier substrate 134) by the distance .DELTA.z from the sound
port 132 in the carrier substrate 134 of the housing 130 in order
to provide the protection structure 140 as an "indirect" sound path
into the interior volume V of the MEMS sensor 100 through the
carrier board 150 and the carrier substrate 134. As a result of the
lateral offset .DELTA.z of the port 152 in the carrier board 150 in
relation to the sound port 132 of the housing 130, the direct
disturbance radiation access (light access) into the interior
volume of the housing 130 can be blocked, while the interior volume
V.sub.1 of the housing 130 remains acoustically open or accessible
to the sound pressure changes .DELTA.P. The carrier board 150 and
the carrier substrate 134 can consequently have off-centered sound
ports 132, 152 for blocking direct disturbance radiation into the
interior volume V.sub.1, as illustrated in FIGS. 9a-9b.
[0079] As illustrated further in FIG. 9b, the sound ports 132, 152
of the carrier substrate 134 and of the carrier board 150 that are
arranged off center in relation to one another can have a conical,
i.e., widening, embodiment (e.g., in a direction toward one
another). As illustrated in FIG. 9b, the sound port 152 of the
carrier board 150 has a conical cross section, i.e., widening cross
section, from the exterior surface region 150-1 to the second
interior surface region 150-2, while the sound port 132 in the
carrier substrate 134 has a conical cross-sectional profile, i.e.,
a widening cross-sectional profile, proceeding from the first
surface region 134-1 adjacent to the interior volume V in the
direction of the second surface region 134-2. Improved airflow and
hence an improved transmission of the sound pressure change
.DELTA.P to the front volume V.sub.1 in the housing 130 of the MEMS
sensor 100 can be achieved by the conical configuration of the
sound ports 132, 152 in the carrier substrate 134 and carrier board
150.
[0080] Optical properties of materials, such as absorbing
materials, for example, which can be used in exemplary fashion for
the protection structure 140, which has an embodiment opaque to
electromagnetic disturbance radiation, are discussed below.
According to exemplary embodiments, the MEMS sensor 100 has a
protection structure 140, which is embodied to at least reduce a
penetration of electromagnetic disturbance radiation X.lamda. with
a wavelength in a range .DELTA..lamda. between 10 nm and 20 .mu.m
into the interior volume V through the sound port 132 and/or at
least reduce a propagation of the electromagnetic radiation
X.lamda. in the interior volume V. An absorbing layer or protection
structure 140 can have a disturbance-radiation-opaque or absorbent
material, for example.
[0081] According to one exemplary embodiment, the protection
structure 140 can have an absorbent layer material which has a high
light-blocking coefficient and a low reflection coefficient such
that, for example, it is possible to avoid a plurality of light
reflections in the back volume or in the back volume of the MEMS
component. "Super-black" surfaces, such as, for example, etched
nickel-phosphor-based coatings or carbon-nanotube-based layers,
such as e.g. vantablack, can be used, for example, for such
applications according to the present concept. The light absorption
of such coating materials substantially exceeds a value of 99% at
all angles of incidence of the electromagnetic disturbance
radiation. By way of example, typical thicknesses of such coating
layers or layer materials are below 10 .mu.m, for example 0.1 to 10
.mu.m, and can be applied to practically any surface material.
Further, polymer materials that can be processed further or
technically modified by virtue of particle filler materials, such
as, e.g., ferrite grains or carbon, being introduced into the
polymer matrix in order to set the optical properties of the
coating of the desired wavelengths, i.e., for example, in the
relevant wavelength range .DELTA..lamda. of the electromagnetic
disturbance radiation X.lamda., can be used as absorbent layer
materials for the protection structure 140.
[0082] The graphical illustrations of FIGS. 10a and 10b illustrate
the absorption depth and the reflectance of brass in an exemplary
manner, which can be used, for example, as covering or capping
material for the covering element 136 of the housing 130. Even
though brass material has high light absorption properties (see
FIG. 10a), brass material further also has a very high reflectance
of, e.g., approximately 90% (see FIG. 10b), which, for example, may
cause interfering multiple reflections of the disturbance
radiation, e.g., light, into the back volume or within the back
volume of the MEMS component 100.
[0083] According to one exemplary embodiment, pyrolytic carbon, for
example, can be used as layer material of the layer structure 140,
with FIGS. 10c-10f showing different optical parameters of this
material in exemplary fashion for the purposes of optimizing the
coating material of the layer structure 140 according to one
exemplary embodiment. By way of example, FIG. 10c shows a
reflectance of pyrolytic carbon as a function of the angle of
incidence of the electromagnetic disturbance radiation, with a
distinction being made between S-polarized light, P-polarized light
and unpolarized light. FIG. 10d plots the absorption depth of
pyrolytic carbon against the wavelength. FIG. 10e shows the damping
of perpendicularly incident light on a 100 nm thick layer made of
pyrolytic carbon. FIG. 10f shows the light blocking of pyrolytic
carbon at a light wavelength of 940 nm.
[0084] As may be gathered from the graphical illustrations in FIGS.
10c-10f, pyrolytic carbon, in the relevant wavelength range
.DELTA..lamda. of electromagnetic disturbance radiation X.lamda.,
exhibits both a good light absorption behavior and a lower
reflectance at different angles of incidence of the electromagnetic
disturbance radiation or light. Further, what can be gathered from
the graphical illustrations of FIGS. 10e-10f is that a layer
thickness of the order of a few .mu.m, for example in a range of 1
to 10 .mu.m or of 2 to 5 .mu.m, or even smaller, e.g., in a range
of 50 to 500 nm or 80 to 200 nm or approximately 100 nm, suffices
to obtain almost complete damping of the incident light, which is
not reflected by the layer material. In this context, reference is
made to the fact that the graphical illustrations of the damping in
FIGS. 10c-10f relate to the non-reflective component of the
incident light of the incident electromagnetic disturbance
radiation.
[0085] The different configurations of the protection structure 140
illustrated above on the basis of FIGS. 1 to 10f facilitate an
effective protection in relation to electromagnetic disturbance
radiation or in the wavelength range .DELTA..lamda. between 10 nm
and 20 .mu.m such that it is possible to obtain MEMS sensors 100,
such as, e.g., MEMS sound transducers or MEMS microphones, that are
insensitive to electromagnetic disturbance radiation.
[0086] While exemplary embodiments are suitable for various
modifications and alternative forms, accordingly exemplary
embodiments of same are shown by way of example in the figures and
described thoroughly here. It goes without saying, however, that
the intention is not to limit exemplary embodiments to the specific
forms disclosed, rather on the contrary the exemplary embodiments
are intended to cover all modifications, counterparts and
alternatives that fall within the scope of the disclosure.
Throughout the description of the figures, identical reference
signs refer to identical or similar elements.
[0087] It goes without saying that if one element is designated as
"connected" or "coupled" to another element, it can be connected or
coupled directly to the other element or intermediate elements can
be present. If, in contrast, one element is designated as
"connected" or "coupled" "directly" to another element, no
intermediate elements are present. Other expressions used for
describing the relationship between elements should be interpreted
in a similar way (e.g. "between" vis-a-vis "directly between",
"adjacent" vis-a-vis "directly adjacent", etc.). Furthermore, the
formulation "at least one" element should be understood to mean
that one element or a plurality of elements can be provided.
[0088] Although some aspects have been described in association
with a MEMS sensor or MEMS assembly, it goes without saying that
some aspects also constitute a description of the corresponding
production method with corresponding method steps for producing a
MEMS assembly. In this regard, providing a block or a component
should also be understood as a method step or a feature of a method
step of a corresponding method. Some or all of the method steps can
be carried out by a hardware apparatus (or using a hardware
apparatus), such as using a microprocessor, a programmable computer
or an electronic circuit. In some exemplary embodiments, some or a
plurality of the most important method steps can be carried out by
such an apparatus.
[0089] In the detailed description above, in some instances
different features have been grouped together in examples in order
to rationalize the disclosure. This type of disclosure ought not be
interpreted as the intention that the claimed examples have more
features than are expressly indicated in each claim. Rather, as
represented by the following claims, the subject matter can reside
in fewer than all features of an individual example disclosed.
Consequently, the claims that follow are hereby incorporated in the
detailed description, wherein each claim can be representative of a
dedicated separate example. While each claim can be representative
of a dedicated separate example, it should be noted that although
dependent claims refer back in the claims to a specific combination
with one or more other claims, other examples also comprise a
combination of dependent claims with the subject matter of any
other dependent claim or a combination of each feature with other
dependent or independent claims. Such combinations shall be
encompassed, unless an explanation is given that a specific
combination is not intended. Furthermore, the intention is for a
combination of features of a claim with any other independent claim
also to be encompassed, even if this claim is not directly
dependent on the independent claim.
[0090] Although specific exemplary embodiments have been
illustrated and described herein, it will be apparent to a person
skilled in the art that a multiplicity of alternative and/or
equivalent implementations can be substituted for the specific
exemplary embodiments shown and illustrated there, without
departing from the subject matter of the present application. This
application text is intended to cover all adaptations and
variations of the specific exemplary embodiments described and
discussed herein. Therefore, the present subject matter of the
application is limited only by the wording of the claims and the
equivalent embodiments thereof.
* * * * *