U.S. patent application number 16/596317 was filed with the patent office on 2020-04-16 for mems device having a rugged package and fabrication process thereof.
The applicant listed for this patent is STMICROELECTRONICS S.R.L.. Invention is credited to Lorenzo BALDO, Marco DEL SARTO, Enri DUQI.
Application Number | 20200115224 16/596317 |
Document ID | / |
Family ID | 65031648 |
Filed Date | 2020-04-16 |
United States Patent
Application |
20200115224 |
Kind Code |
A1 |
DUQI; Enri ; et al. |
April 16, 2020 |
MEMS DEVICE HAVING A RUGGED PACKAGE AND FABRICATION PROCESS
THEREOF
Abstract
A MEMS device formed by a substrate, having a surface; a MEMS
structure arranged on the surface; a first coating region having a
first Young's modulus, surrounding the MEMS structure at the top
and at the sides and in contact with the surface of the substrate;
and a second coating region having a second Young's modulus,
surrounding the first coating region at the top and at the sides
and in contact with the surface of the substrate. The first Young's
modulus is higher than the second Young's modulus.
Inventors: |
DUQI; Enri; (Milan, IT)
; DEL SARTO; Marco; (Monza, IT) ; BALDO;
Lorenzo; (Bareggio, IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
STMICROELECTRONICS S.R.L. |
Agrate Brianza |
|
IT |
|
|
Family ID: |
65031648 |
Appl. No.: |
16/596317 |
Filed: |
October 8, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B81C 1/00325 20130101;
B81C 99/0005 20130101; B81C 2203/0154 20130101; B81B 2207/012
20130101; B81B 3/0018 20130101; B81C 2203/0136 20130101; B81B
7/0048 20130101; B81B 7/0058 20130101; B81C 2201/112 20130101; B81B
2201/0235 20130101 |
International
Class: |
B81C 1/00 20060101
B81C001/00; B81B 3/00 20060101 B81B003/00; B81C 99/00 20060101
B81C099/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 12, 2018 |
IT |
102018000009408 |
Claims
1. A MEMS device, comprising: a substrate having a surface; a MEMS
structure arranged on the surface; a first coating region having a
first Young's modulus, the first coating region on the surface of
the substrate and covering the MEMS structure; and a second coating
region having a second Young's modulus, the second coating region
covering the first coating region, wherein the first Young's
modulus is higher than the second Young's modulus.
2. The device according to claim 1, wherein the first Young's
modulus is between 20 GPa and 30 GPa, and the second Young's
modulus is between 100 MPa and 5 GPa.
3. The device according to claim 1, wherein the first coating
region comprises a polymeric resin.
4. The device according to claim 1, wherein the second coating
region comprises a polymeric rubber.
5. The device according to claim 1, wherein the MEMS structure is
electrically coupled to the substrate.
6. The device according to claim 1, wherein the MEMS structure
comprises: an ASIC die arranged on the surface of the substrate;
and a MEMS sensor die arranged on the ASIC die and electrically
coupled to the ASIC die.
7. A process comprising: coupling a MEMS structure to a surface of
a substrate; forming a first coating region on the first surface
and over the MEMS structure, the first coating region having a
first Young's modulus; and forming a second coating region over the
first coating region, the second coating region having a second
Young's modulus, wherein the first Young's modulus is higher than
the second Young's modulus.
8. The process according to claim 7, wherein the first Young's
modulus is between 20 GPa and 30 GPa, and the second Young's
modulus is between 100 MPa and 5 GPa.
9. The process according to claim 7, wherein the first coating
region comprises a polymeric resin.
10. The process according to claim 8, wherein the second coating
region comprises a polymeric rubber.
11. The process according to claim 7, wherein forming the first
coating region comprise: arranging a first molding matrix having a
first molding cavity on the surface of the substrate so that the
first molding cavity covers the MEMS structure; injecting a first
coating material into the first molding cavity to form the first
coating region; and removing the first molding matrix.
12. The process according to claim 11, wherein injecting the first
coating material comprises: exposing the first coating material to
a first injection temperature; and injecting the first coating
material at the first injection temperature into the first molding
cavity at a first transfer pressure.
13. The process according to claim 12, comprising, after injecting
the first coating material, curing the first coating material by
exposing the first coating material to a first curing temperature
for a first time period.
14. The process according to claim 13, wherein forming the second
coating region comprises: arranging a second molding matrix having
a second molding cavity on the surface of the substrate so that the
second molding cavity faces and surrounds the first coating region;
and injecting a second coating material into the second molding
cavity to form the second coating region.
15. The process according to claim 14, wherein injecting the second
coating material comprises: exposing the second coating material to
a second injection temperature; and injecting the second coating
material at the second injection temperature into the second
molding cavity at a second transfer pressure.
16. The process according to claim 15, comprising, after injecting
the second coating material, curing the second coating material,
wherein curing the second coating material comprises exposing the
second curing material to a second curing temperature for a second
time period.
17. A method, comprising: arranging a plurality of MEMS structures
on a first surface of substrate; covering the plurality of MEMS
structures with a plurality of first coating regions, respectively,
the first coating regions having a first Young's modulus; covering
the plurality of first coating regions with a coating mass and
forming a packaged wafer, wherein the coating mass has a second
Young's modulus lower than the first Young's modulus; and dicing
the packaged wafer to form a plurality of MEMS devices.
18. The method according to claim 17, wherein the first Young's
modulus is between 20 GPa and 30 GPa, and the second Young's
modulus is between 100 MPa and 5 GPa.
19. The method according to claim 17, wherein the first coating
region is a resin and the second coating region is a rubber.
20. The method according to claim 17, wherein each MEMS device
comprises a respective MEMS structure, a respective first coating
region, and a respective second coating region derived from dicing
the coating mass.
Description
BACKGROUND
Technical Field
[0001] The present disclosure relates to a MEMS (Micro
Electro-Mechanical System) device and the fabrication process
thereof.
Description of the Related Art
[0002] As is known, electronic apparatuses comprising MEMS devices,
such as MEMS movement sensors, are increasingly widespread. For the
correct operation of such apparatuses, it is desired that MEMS
devices are capable of detecting movement variations in an accurate
and precise way in all operating conditions. Consequently, it is
desirable for MEMS devices to be sufficiently sturdy so as not to
break even when they are subjected to abrupt movements (for
example, as a result of the apparatus being dropped or undergoing
mechanical shock). Furthermore, it is desirable that their
performance not to be significantly affected by the above abrupt
movements.
[0003] In most cases, it is not desirable to increase the
robustness of MEMS devices by increasing their dimensions. In fact,
MEMS movement sensors may be modelled as mass-spring systems, the
resonance frequency thereof strictly depends on the geometry of the
mass-spring system. Since the resonance frequency is an important
parameter for determining the performance of the MEMS device, it is
not desirable to improve the robustness of the MEMS device by
modifying its dimensions since this would have an undesired impact
on performance.
[0004] Consequently, known solutions for increasing robustness
consist in providing mechanical stoppers operating outside of
and/or within the extension plane of the MEMS movement sensor.
[0005] For instance, the U.S. Pat. Pub. No. 2013/299923 describes a
micromechanical accelerometer comprising a seismic mass and a
semiconductor substrate (for example, silicon) having a reference
electrode. In particular, the seismic mass is moveable
perpendicular to the reference electrode; moreover, the seismic
mass comprises a flexible stopper operating in the movement
direction of the seismic mass.
[0006] In addition, to increase robustness, it is known to treat
the substrate by carrying out a slow etching step so as to maximize
the contact area in the event of abrupt movements.
[0007] Furthermore, it is known to package MEMS movement sensors in
resins capable of absorbing part of the acceleration due to the
sharp movements so as to increase further robustness of the MEMS
device.
[0008] However, known solutions have some disadvantages.
[0009] In fact, if subjected to repeated mechanical shocks with
high accelerations, mechanical stoppers of a MEMS movement sensor
undergo gradual damage and failure, causing failure of the
mechanical stoppers in the long run, which thus no longer protect
the MEMS movement sensor.
[0010] This is demonstrated by tumble tests carried out on single
MEMS devices. For this purpose, the tested MEMS devices are dropped
on a granite slab with different accelerations which depend on
different variables, such as the contact stiffness, the roughness
of the contact surface, the contact angle, the contact points or
areas and the air resistance. In detail, the acceleration acting on
the package of the MEMS device upon impact with the granite slab is
analytically estimated by the known Hertz theory (Eq. (1)):
a _ = v imp 6 R [ m ( 1 - v t 2 E t + 1 - v d 2 E d ) ] 2 5 ( 1 )
##EQU00001##
[0011] where .nu..sub.imp is the speed of impact; R is the radius
of the object, m is the mass of the MEMS sensor; .nu..sub.t and
.nu..sub.d are the Poisson's ratios of the granite slab and of the
MEMS device, respectively, and E.sub.t and E.sub.d are the Young's
modulus of the granite slab and of the MEMS device,
respectively.
[0012] The Applicant has verified that, both by applying Eq. (1)
and with the aid of Finite-Element Modelling (FEM) simulations,
that a MEMS device having a package of 2.times.2 mm.sup.2 perceives
an acceleration of approximately 100,000 g in case of the apparatus
dropping in standard conditions, from approximately one meter of
height from the granite slab. These repeated accelerations may lead
to malfunctioning or failure of the MEMS device, thus rendering it
unusable.
[0013] This problem is particularly felt when handling the MEMS
device before assembling the package (in particular, fixing the
MEMS device to a supporting structure). In detail, when the MEMS
device is picked up by an automatic picker machine arranged on a
supporting surface on which it is fixed (pick-and-place operation),
impacts that lead to marked accelerations of the order, for
example, of tens of thousands of g may occur.
BRIEF SUMMARY
[0014] Embodiments are directed to a MEMS device and a fabrication
process thereof. In particular, the present disclosure relates to a
MEMS (Micro Electro-Mechanical System) device having a rugged
package and to the fabrication process thereof. More particularly,
reference is made hereinafter to a packaging process that uses an
injection molding system. Moreover, hereinafter reference is made
to MEMS devices comprising one or more MEMS sensors capable of
detecting movements (such as accelerometers), without this implying
any loss of generality.
[0015] In one embodiment, a MEMS device is provided, formed by a
substrate having a surface; a MEMS structure arranged on the
substrate surface; a first coating region, having a first Young's
modulus, surrounding the MEMS structure and in contact with part of
the surface of the substrate; and a second coating region having a
second Young's modulus, surrounding the first coating region and in
contact with part of the surface of the substrate. The first
Young's modulus is higher than the second Young's modulus.
[0016] The MEMS structure may be electrically coupled to the
substrate.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0017] For a better understanding of the present disclosure, an
embodiment thereof is now described, purely by way of non-limiting
example, with reference to the attached drawings, wherein:
[0018] FIG. 1 shows a block diagram of an injection molding
system;
[0019] FIGS. 2 to 5 show, in cross-section, successive steps of the
present fabrication process a MEMS device; and
[0020] FIG. 6 shows the plot of a characteristic quantity of a
coating region of the package of the present MEMS device.
DETAILED DESCRIPTION
[0021] FIG. 1 schematically illustrates an injection molding
system, hereinafter referred to as system 200.
[0022] In particular, the system 200 comprises a hopper 202, which
supplies a material to be injected in solid form (for example, in
the form of pellets); an injector 204, provided with a heater and
an injection system (not illustrated); and a molding chamber 206,
housing one or more wafers or devices to be processed and
comprising one or more molding matrices (not illustrated).
[0023] In use, in the molding chamber 206, the aforementioned one
or more molding matrices are fixed to the wafer or to the device to
be processed. In particular, the molding matrix or matrices have
one or more cavities, which define the desired shape for the
element to be molded on the wafer or on the device to be
processed.
[0024] The hopper 202 supplies the material to be injected to the
injector 204, which, through the heater, heats it up to the melting
point (or, in case of plastic materials, the point of vitreous
transition). The injection system of the injector 204 injects the
molten material into the molding chamber 206, in particular into
the one or more cavities of the molding matrix or matrices; in this
way, the one or more cavities of the molding matrix or matrices
is/are filled with the material that will constitute the element to
be moulded.
[0025] Once injection is completed, still within the molding
chamber, the injected material is subjected to a curing step and
starts to polymerize and solidify so that the desired moulded
element is obtained. When the moulded element has solidified, the
molding matrix is removed.
[0026] FIGS. 2-5 show successive fabrication steps of a plurality
of packaged and singulated MEMS devices (three whereof are
illustrated in FIG. 5). In particular, the present fabrication
process is obtained by using the system 200 of FIG. 1.
[0027] FIG. 2 illustrates a processing wafer 1 comprising a
substrate 5 (for example, a laminated substrate or a semiconductor
substrate, such as a silicon substrate), having a surface 5A. In
particular, the substrate 5 is adapted for a package of an LGA
(Land-Grid Array) type.
[0028] The substrate 5 carries, on the surface 5A, a plurality of
MEMS structures 10, such as three MEMS dice are illustrated in FIG.
2. In detail, each MEMS structure 10 is electrically connected to
the substrate 5 through a plurality of conductive tracks (not
illustrated).
[0029] Each MEMS structure 10 comprises an ASIC
(Application-Specific Integrated Circuit) 11, extending over the
substrate 5, and a MEMS sensor 12, extending over the ASIC 11. In
particular, the ASIC 11 is made per se known manner and is
electrically and directly connected to the conductive paths of the
substrate 5 and/or to the MEMS structure 10, in a per se known
manner. The MEMS sensor 12 is a movement sensor, for example an
inertial sensor, such as an accelerometer or a gyroscope, obtained
in a per se known manner. The ASIC 11 and the MEMS sensor are made
of semiconductor material, such as silicon, using standard
semiconductor processing techniques.
[0030] With reference to FIG. 2, the processing wafer 1 is
subjected to a first injection molding step. To this end, the
processing wafer 1 is arranged in the molding chamber 206 of the
system 200 of FIG. 1.
[0031] As illustrated in FIG. 3, a first molding matrix 20 is fixed
on the surface 5A of the substrate 5. In particular, the first
molding matrix 20 comprises first molding structures 20A (three
whereof are illustrated in FIG. 3) that form respective first
molding cavities 20B. The first molding cavities 20B have, for
example, a frustopyramidal shape. Other shapes are, however,
possible. Each molding cavity 20B is delimited by a respective
molding structure 20A and by the surface 5A of the substrate 5 and
it is arranged at a respective MEMS structure 10 so that each MEMS
structure 10 is accommodated in a respective first molding cavity
20B, between the respective molding structure 20A and the surface
5A of the substrate 5.
[0032] A first coating material, of a polymeric type, such as resin
(for example, EME-G770HE manufactured by Sumitomo), supplied in
solid form (for example, pellets) by the hopper 202 to the injector
204 of the system 200, is brought to an injection temperature
T.sub.i in a range, for example, between 170.degree. C. and
180.degree. C. (for example, 175.degree. C.) by the heater of the
injector 204, to form a first molten polymeric agglomerate.
[0033] The first molten polymeric agglomerate is injected into the
molding chamber 206 by the injection system of the injector 204, at
a transfer pressure p.sub.tr in a range, for example, between 7 MPa
and 12 MPa (e.g., 8 MPa). Injection of the first molten polymeric
agglomerate leads to the filling of the first molding cavities 20B
of the first molding matrix 20, and enables complete coating of the
plurality of MEMS structures 10 and of the surface portions 5A of
the substrate 5 delimited by the first molding matrix 20, thus
forming first coating regions 25.
[0034] A first curing step is carried out, wherein the first
coating regions 25 are brought to a first curing temperature
T.sub.c1, for example in a range between 170.degree. C. and
180.degree. C. (in particular, 175.degree. C.) in a first curing
time t.sub.c1 of a duration a range, for example, between 70 s and
120 s (in particular, 90 s). The first curing step enables
cross-linking of the polymeric bonds of the first coating regions
25, enabling a transition phase from the molten state to the solid
state.
[0035] At the end of the first curing step, the processing wafer 1
is extracted from the molding chamber 206. Next, it is possible to
carry out a first post-molding curing step, for strengthening the
structure of the first coating regions 25. In particular, the first
coating regions 25 are heated in dedicated ovens, external to the
chamber 206, at a treatment temperature T.sub.pc in the range, for
example, between 170.degree. C. and 180.degree. C. (e.g.,
175.degree. C.) for a treatment time t.sub.pc longer than the first
curing time t.sub.c1, having a duration in the range, for example,
between 2 hrs and 8 hrs (in particular, 6 hrs). In this way, the
polymeric bonds of the first coating regions 25 are further
cross-linked, and hence strengthened.
[0036] Alternatively, the first post-molding curing step is carried
out in the molding chamber 206.
[0037] At the end of the above steps, the processing wafer 1 has a
plurality of first coating regions 25 that coat respective MEMS
structures 10.
[0038] By virtue of the use of a polymeric material, in particular
the above resin manufactured by Sumitomo, each first coating region
25 is compatible with the materials of the substrate 5, of the ASIC
11, and of the MEMS sensor 12, so as to limit the residual stresses
caused by interfacing different materials. Moreover, in the present
case, each first coating region 25 has a Young's modulus in the
range, for example, between 20 GPa and 30 GPa in standard
conditions of temperature and pressure (i.e., at 25.degree. C. and
1 atm).
[0039] With reference to FIG. 4, the processing wafer 1 is
subjected to a second injection molding.
[0040] In particular, after removing the first molding matrix 20, a
second molding matrix 30 is arranged on the surface 5A of the
substrate 5 of the processing wafer 1. The second molding matrix 30
comprises a second molding structure 30A, which covers the entire
surface 5A of the substrate 5, and forms a second molding cavity
30B having, for example, a cylindrical shape. The second molding
cavity 30B is delimited by the further molding structure 30A and by
the surface 5A. Thus, the second molding cavity 30B accommodates
the MEMS structures 10 and the respective first coating regions
25.
[0041] Next, a second coating made of polymeric material, such as
rubber (for example, Sylgard 567 manufactured by Dow Corning), is
supplied in liquid form (in particular, in case of Sylgard 567, a
first and a second liquid component, mixed with each other) from
the hopper 202 to the injector 204 of the system 200. In
particular, the injector 204, through the heater, brings or exposes
the second coating material up to the injection temperature
T.sub.i. In this way, the second coating material is molten (in
particular, rendered plastic), to form a second molten polymeric
agglomerate.
[0042] Next, the second molten polymeric agglomerate is injected by
the injection system of the injector 204 into the molding chamber
206, in particular into the second molding cavity 30B, at the
transfer pressure p.sub.tr. Injection into the second molding
cavity 30B of the second molten polymeric agglomerate fills the
second molding cavity 30B and completely coats the surface 5A and
the first coating regions 25 of the MEMS structures 10, to form a
coating mass 35.
[0043] Next, the coating mass 35 is subjected to curing step. In
particular, the coating mass 35 is cured for a second curing time
t.sub.c2, of a duration, for example, of 180 min, at a second
curing temperature T.sub.c2, for example equal to 70.degree. C.
Alternatively, the second curing time t.sub.c2 is approximately 120
min and the second curing temperature T.sub.c2 is approximately
100.degree. C. In both cases, the curing process here also enables
cross-linking of the polymeric bonds of the coating mass 35.
[0044] At the end of the second curing step, it is possible to
carry out a second post-molding curing step so that the polymeric
bonds of the coating mass 35 are further cross-linked, and thus
strengthened. The second post-molding curing step is similar to the
first post-molding curing step previously described with reference
to the first coating regions 25.
[0045] By virtue of the used material and to the described
treatment processes, the coating mass 35 is compatible with the
substrate 5 and the first coating regions 25 so that the residual
stresses due to interfacing are limited. Moreover, the coating mass
35 has a Young's modulus lower than the Young's modulus of the
first coating regions 25, for example between 100 MPa and 5 GPa,
e.g., 500 MPa, in standard conditions of temperature and pressure
(i.e., at 25.degree. C. and 1 atm).
[0046] At the end of the first and second molding processes, a
processed wafer 50 is obtained, which (FIG. 5) is diced, in a per
se known manner, so as to obtain a plurality of MEMS devices 100,
each having an own first coating region 25 and an own second
coating region 37, deriving from dicing of the coating mass 35.
[0047] The MEMS devices 100 efficiently absorb the impacts and/or
mechanical shocks to which they could be exposed during their
operating life and protect the delicate internal structures (ASIC
11 and MEMS sensor 12). In particular, since each first coating
region 25 has a high Young's modulus (i.e., a low flexibility), the
first coating regions 25 mechanically protect and strengthen the
internal structures, minimizing the thermo-mechanical stress
between the materials of the first coating region 25 and the
internal structures, as well as the substrate 5. Moreover, since
the material of the second coating region 37 has a Young's modulus
lower than the Young's modulus of the first coating region 25 (and
hence more flexible), the second coating region 37 is able to
efficiently absorb the impact caused by possible mechanical
shocks.
[0048] Thus, the first and second coating regions 25, 37 are
designed so as to decouple the mechanical stresses deriving from an
external impact and deriving from interfacing between the different
materials forming the MEMS device 100.
[0049] In this connection, the Applicant determined the plot of the
acceleration as a function of the Young's modulus of the second
coating region 37 of one of the MEMS devices 100 obtained according
to the fabrication process described previously. This plot is shown
in FIG. 6 and denoted by the reference A. In particular, the plot A
was obtained analytically from Eq. (1), the abscissae representing
the Young's modulus of the material of the second coating region 37
(term E.sub.d of Eq. (1)) and the ordinates representing
acceleration .
[0050] The Applicant noted that, by decreasing the Young's modulus
of the second coating region 37, the acceleration significantly
decreases. Consequently, the acceleration perceived by each tested
MEMS device 100 is lower than the impact acceleration perceived by
a MEMS device without the second coating region 37; moreover, the
height of fall where the acceleration is equal to 100,000g
increases. Consequently, the second coating region 37 imparts the
MEMS devices 100 a greater robustness.
[0051] The Applicant then conducted further reliability tests and
tests on the occurred adhesion of the second coating region 37,
including a test of mechanical stress as reliability test and a
peeling test as an adhesion test of the second coating layer 37. In
the mechanical-stress test, a test wafer and a reference wafer were
used.
[0052] Initially, the test and reference wafers were optically
analyzed using known instruments (such as instruments of optical
analysis, infrared analysis, X-ray analysis, tomography or SEM
analysis), so as to verify the structural homogeneity thereof.
[0053] Next, the test wafer was indented with a needle probe having
a tip with a diameter equal to, for example, 0.6 mm, for a testing
time t.sub.t equal to, for example, 96 hrs, to detect the
penetration rate, as well as the penetration limit, of the needle
probe in the second coating region 37 of the test wafer.
[0054] In the executed indentation tests, the Applicant noted that
the needle probe penetrates at a rate of 0.1 mm/s and reaches a
penetration limit equal to 50% of the thickness of the second
coating region 37; moreover, these results were obtained in any
point of the second coating region 37.
[0055] Next, the test wafer was again analyzed and compared at an
optical level with the reference wafer so as to verify the presence
or absence of evident indentations in the second coating region 37
of the test wafer. The Applicant noted that there were no clear
differences between the reference wafer and the test wafer after
indenting the test wafer. Consequently, the second coating region
37 is able to efficiently respond to an external mechanical stress,
minimizing the negative effects thereof; moreover, this
characteristic is substantially present on the entire surface of
the aforementioned second coating region 37.
[0056] In the peeling test, here of a chemical type, in the
beginning the MEMS device 100 under analysis was treated with
chemical solutions of a known type, such as nitric acid.
[0057] Next, the Applicant attempted to detach the second coating
region 37 from the surface 5A of the substrate 5 and from the first
coating region 25 and noted that the second coating region 37
detached in an uneven way, tearing. This result implies that the
second coating region 37, obtained according to the fabrication
process described previously, has a good adherence both to the
surface 5A and to the first coating region 25.
[0058] The present MEMS manufacturing device and the corresponding
process have various advantages.
[0059] In particular, the presence of two coatings with different
Young's moduli enables the reduction of the negative effects of
impacts and/or mechanical shocks, so that the MEMS device is
sturdy, albeit in the absence of stoppers that are subject to
deterioration. In fact, as mentioned above, the first coating
region 25 (less flexible) minimizes the thermo-mechanical stress
between the materials of the substrate 5 and of the second coating
region 37, and the second coating layer (more flexible) is able to
absorb the impact waves (and hence, the impact acceleration)
generated by this impact. In other words, the thermomechanical
stress between the materials and the stress deriving from an impact
are decoupled by virtue of the greater flexibility of the second
coating region 37 with respect to the first coating region 25.
[0060] In addition, the coating regions 25, 37 do not modify the
electrical or detection characteristics of the MEMS device 100,
which thus has a practically unvaried performance.
[0061] Furthermore, the present fabrication process enables
formation of coating regions with a good degree of adhesion, and
thus the characteristics of the MEMS device 100 are not degraded
over time.
[0062] Moreover, the present fabrication process is simple to
implement.
[0063] Finally, it is clear that modifications and variations may
be made to the MEMS device and to the corresponding fabrication
process described and illustrated herein, without thereby departing
from the scope of the present disclosure.
[0064] For instance, the MEMS sensor 12 of the MEMS device 100 may
be of any type.
[0065] Moreover, each MEMS structure 10 may comprise more than one
MEMS movement sensor 12.
[0066] In addition, the materials forming the first and second
coating regions 25, 37 may be different from the ones used in the
fabrication process described previously; in particular, the choice
of the materials may depend, for example, upon the application
field and the geometry of the MEMS device.
[0067] The various embodiments described above can be combined to
provide further embodiments. These and other changes can be made to
the embodiments in light of the above-detailed description. In
general, in the following claims, the terms used should not be
construed to limit the claims to the specific embodiments disclosed
in the specification and the claims, but should be construed to
include all possible embodiments along with the full scope of
equivalents to which such claims are entitled. Accordingly, the
claims are not limited by the disclosure.
* * * * *