U.S. patent application number 14/049910 was filed with the patent office on 2014-05-22 for method for producing an integrated circuit pointed element, and corresponding integrated circuit.
This patent application is currently assigned to STMICROELECTRONICS (ROUSSET) SAS. The applicant listed for this patent is STMICROELECTRONICS (ROUSSET) SAS. Invention is credited to Virginie Bidal, Pascal Fornara, Yoann Goasduff, Abderrezak Marzaki.
Application Number | 20140138814 14/049910 |
Document ID | / |
Family ID | 47429930 |
Filed Date | 2014-05-22 |
United States Patent
Application |
20140138814 |
Kind Code |
A1 |
Marzaki; Abderrezak ; et
al. |
May 22, 2014 |
Method for Producing an Integrated Circuit Pointed Element, and
Corresponding Integrated Circuit
Abstract
A method for producing an integrated circuit pointed element is
disclosed. An element has a projection with a concave part
directing its concavity towards the element. The element includes a
first etchable material. A zone is formed around the concave part
of the element. The zone includes a second material that is less
rapidly etchable than the first material for a particular etchant.
The first material and the second material are etched with the
particular etchant to form an open crater in the concave part and
thus to form a pointed region of the element.
Inventors: |
Marzaki; Abderrezak;
(Marseille, FR) ; Goasduff; Yoann; (Fuveau,
FR) ; Bidal; Virginie; (Fuveau, FR) ; Fornara;
Pascal; (Pourrieres, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
STMICROELECTRONICS (ROUSSET) SAS |
Rousset |
|
FR |
|
|
Assignee: |
STMICROELECTRONICS (ROUSSET)
SAS
Rousset
FR
|
Family ID: |
47429930 |
Appl. No.: |
14/049910 |
Filed: |
October 9, 2013 |
Current U.S.
Class: |
257/735 ;
438/611 |
Current CPC
Class: |
B81B 2201/018 20130101;
B81B 2203/0361 20130101; G01V 7/04 20130101; H01H 37/04 20130101;
B81C 1/00111 20130101; H01L 28/82 20130101; B81B 2201/0235
20130101; H01H 37/32 20130101; H01H 37/42 20130101; H01L 28/88
20130101; B81B 2201/0242 20130101; B81B 3/001 20130101; B81B
2203/04 20130101; H01H 61/013 20130101; H01L 29/4238 20130101; H01H
9/02 20130101; H01L 21/32139 20130101 |
Class at
Publication: |
257/735 ;
438/611 |
International
Class: |
H01L 23/482 20060101
H01L023/482; H01L 21/48 20060101 H01L021/48 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 16, 2012 |
FR |
1260912 |
Claims
1. A method for producing an integrated circuit pointed element,
the method comprising: forming an element having a projection with
a concave part directing its concavity towards the element, the
element comprising a first etchable material; forming a zone around
the concave part of the element, the zone comprising a second
material that is less rapidly etchable than the first material for
a particular etchant; and etching the first material and the second
material with the particular etchant to form an open crater in the
concave part and thus to form a pointed region of the element.
2. The method according to claim 1, wherein forming the zone
comprises forming a layer of the second material above and around
the at least one concave part and removing a portion of the layer
of the second material so as to abrade a crown of the concave
part.
3. The method according to claim 2, wherein forming the crater
comprises simultaneously etching the first material and the second
material.
4. The method according to claim 3, further comprising removing the
second material after the etching of the first material and of the
second material.
5. The method according to claim 1, wherein the element and the
projection comprise the same first material.
6. The method according to claim 5, wherein forming the element
comprises forming a support comprising a block and performing a
compliant deposition of a layer of the first material on the
support, part of the layer overlapping the block forming the
projection.
7. The method according to claim 1, wherein forming the element
comprises forming an element having a plurality of projections,
wherein the first material and of the second material are etched so
as to form an open crater in each concave part and thus to form
several pointed regions.
8. The method according to claim 7, wherein forming the element
comprises forming a support comprising a plurality of blocks and
performing a compliant deposition of a layer of the first material
over the support, part of the layer overlapping the blocks forming
the projections.
9. A device, comprising an element of an integrated circuit having
at least one projection, the element comprising a pointed region in
an upper part and a base in a lower part, the pointed region
limiting an open crater and broadening out from a pointed end
towards the base.
10. The device according to claim 9, wherein an external wall of
the pointed region exhibits a concave profile extending from the
opening of the crater and directing its concavity towards the
crater.
11. The device according to claim 9, wherein the crater exhibits a
hollowed part at a foot of an internal wall of the pointed
region.
12. The device according to claim 9, further comprising a support
possessing a block, wherein the element is located above the
support.
13. The device according to claim 12, wherein the pointed region is
auto-aligned with the block.
14. The device according to claim 9, wherein the projection and a
remainder of the element comprise one and the same first
material.
15. The device according to claim 9, wherein the element comprises
a plurality of projections, each projection having a pointed
region.
16. An integrated circuit, comprising: a support; and an element
having a projection disposed over the support, the element
comprising a pointed region in an upper part and a base in a lower
part, the pointed region limiting an open crater and broadening out
from a pointed end towards the base.
17. The integrated circuit according to claim 16, wherein the
integrated circuit comprises a capacitor that includes two
electrodes separated by a dielectric layer, at least one of the
electrodes being formed with the element.
18. The integrated circuit according to claim 16, wherein the
integrated circuit comprises an interconnection part comprising
several metallization levels separated by an isolating region, the
element being metallic and situated on one of the metallization
levels.
19. The integrated circuit according to claim 18, further
comprising a mechanical system for electrical switching within the
interconnection part, the mechanical system including the
element.
20. The integrated circuit according to claim 19, the mechanical
system comprising a first deformable assembly in a housing, the
first deformable assembly including a beam held in at least two
different places by at least two arms secured to edges of the
housing, the beam and the arms being metallic and situated within
one and the same metallization level, the mechanical system further
including an electrically conducting body.
21. The integrated circuit according to claim 20, wherein the first
deformable assembly has a first configuration when it has a first
temperature and a second configuration when at least one of the
arms has a second temperature different from the first
temperature.
22. The integrated circuit according to claim 21, wherein the beam
is remote from the body in the first configuration and in contact
with the body and immobilized by the body in the second
configuration so as to be able to establish or prohibit an
electrical link passing through the body and through the beam,
wherein the first deformable assembly is activatable to pass from
one of the configurations to another.
23. The integrated circuit according to claim 22, wherein the
mechanical system further comprises a release mechanism configured
to release a beam immobilized by the body and comprising the
element, the pointed region being directed towards the body.
24. The integrated circuit according to claim 23, wherein the
mechanical system further comprises a generator configured to
generate an electrostatic field at a level of the pointed
region.
25. The integrated circuit according to claim 18, further
comprising a mechanical system for detecting spatial orientation
and/or change of orientation of the integrated circuit, the
mechanical system disposed within the interconnection part and
comprising the element and a housing whose walls comprise metallic
portions produced within various metallization levels.
26. The integrated circuit according to claim 25, wherein the
housing comprises a floor wall and a ceiling wall and wherein the
mechanical system includes a metallic piece housed in the housing
and mobile inside the housing, a check mechanism with the housing
providing an evolution zone for the metallic piece and comprising
at least two electrically conducting elements disposed at a
boundary of the evolution zone.
27. The integrated circuit according to claim 26, wherein the floor
or ceiling walls incorporate the element and direct the pointed
region towards the metallic piece inside the evolution zone, the
piece being configured so as, under the action of gravity, to come
into contact with the electrically conducting elements in response
to a given spatial orientation of the integrated circuit.
28. The integrated circuit according to claim 27, further
comprising a detector configured to detect an electrical link
passing through the piece and the electrically conducting elements.
Description
[0001] This application claims priority to French Patent
Application 1260912, which was filed Nov. 16, 2012 and is
incorporated herein by reference.
TECHNICAL FIELD
[0002] The invention relates to integrated circuits and, in
particular embodiments, to the formation of tips in and/or on an
integrated circuit.
BACKGROUND
[0003] The tip effect is used in certain devices, especially to
increase the field effect.
[0004] Thus, it is known, in charge-storage nonvolatile memories,
to create tips on the polysilicon floating gate, so as to
facilitate the injection of carriers into the upper gate.
[0005] It is possible in this regard to cite U.S. Pat. Nos.
5,783,473, 6,410,957 and 6,635,922 as well as the following
articles:
[0006] "An Analytical Model for Optimization of Programming
Efficiency and Uniformity of Split Gate Source-Side Injection
Superflash Memory", Huinan Guan, IEEE Transactions on Electron
Devices, vol. 50, No. 3, March 2003,
[0007] "A Novel 3 Volts-Only, Small Sector Erase, High Density
Flash EPROM", Sohrab Kianian et al., 1994 Symposium on VLSI
Technology Digest of Technical Papers, 1994 IEEE,
[0008] "Tunneling Phenomenon in Superflash.RTM. Cell", A. Kotov et
al., 2002 IEEE Nonvolatile Memory Technology Symposium, p.
110-115.
[0009] The formation of the tips of the floating gate comprises an
oxidation of the polysilicon of this floating gate.
SUMMARY
[0010] The conventional method is limited to the fabrication of
tips on a polysilicon region in the part of the integrated circuit
customarily designated by the person skilled in the art under the
acronym "FEOL" (Front End Of Line) and requires a significant
thermal budget.
[0011] According to one mode of implementation, it is proposed to
produce tips in an integrated circuit, both in the FEOL part and in
the interconnection part situated above this FEOL part and commonly
designated by the person skilled in the art under the acronym
"BEOL" (Back End Of Line), while preserving substantially the same
thermal budget as that used customarily for producing an integrated
circuit, and without being limited to polysilicon.
[0012] According to one aspect, a method for producing an
integrated circuit pointed element comprises formation of an
element possessing at least one projection having a concave part
directing its concavity towards the element and comprising a first
etchable material. The material can be, for example, polysilicon or
a metallic material such as aluminum. A formation around the
concave part of a zone comprises a second material less rapidly
etchable than the first material, for example a material used in
the so-called "BARC" (Bottom Anti Reflective Coating)
anti-reflection layers, or else a resin or indeed a carbonaceous
layer.
[0013] The method also comprises an etching of the first material
and of the second material so as to form an open crater in the
concave part and thus to form a pointed region of the element.
[0014] Thus, according to this aspect, the formation of tips is
obtained simply by etching two materials at the level of a concave
projection, and, the selectivity of etching as well as the duration
of etching make it possible to adjust the depth and the width of
the crater, thereby making it possible to adjust the height of the
tips as well as the opening of the pointed region. The use of
etching(s) makes it possible to avoid a significant thermal budget
for the formation of these tips.
[0015] Moreover, these production steps can be performed at any
site of the integrated circuit, be it in the FEOL part or in the
BEOL part, and with any materials, provided that the materials used
are etchable.
[0016] According to one mode of implementation, the formation of
the zone comprising the second material, comprises a formation of a
layer of the second material above and around the at least one
concave part, and a removal, for example by a mechanochemical
polishing, of a part of this layer so as to abrade the crown of
this concave part, and the formation of the crater then comprises
the simultaneous etching of the first material and of the second
material.
[0017] It is also possible, after the etching of the first material
and of the second material, to remove the second material, so as to
release the exterior of the pointed region.
[0018] Preferably, the element and the at least one projection
comprise the same first material. Stated otherwise, the element and
its projection or projections are formed of one and the same
material.
[0019] In this case, according to one mode of implementation, the
formation of the element comprises a formation of a support, made
for example of silicon or else silicon oxide, comprising at least
one salient block and a compliant deposition of a layer of the
first material on the support, the part of the layer overlapping
the at least one block forming the at least one projection.
[0020] In this case, the projection can take the form of a dome,
autoaligned on the subjacent salient block.
[0021] According to one mode of implementation, it is possible to
form an element possessing several projections and to form the zone
comprising the second material around each concave part and between
two adjacent concave parts. An etching of the first material and of
the second material is then undertaken so as to form an open crater
in each concave part, and thus to form several pointed regions.
[0022] The formation of the element can comprise a formation of a
support comprising several salient blocks and a compliant
deposition of a layer of the first material on the support, the
part of the layer overlapping the blocks forming the
projections.
[0023] According to another aspect, a device comprises at least one
element of an integrated circuit having at least one projection,
comprising in its upper part a pointed region limiting an open
crater whose opening is smaller than the distance, reckoned at the
level of the bottom of the crater, between two points of the
external wall of the pointed region that are substantially opposite
with respect to the center of the crater. Stated otherwise, the
pointed region broadens out in the direction of its base the
further one recedes from the center of the crater.
[0024] According to one embodiment, the external wall of the
pointed region exhibits a concave profile extending from the
opening of the crater and directing its concavity towards the
crater.
[0025] The crater can exhibit a hollowed part at the foot of the
internal wall of the pointed region.
[0026] According to one embodiment, the device furthermore
comprises a support possessing at least one salient block, and the
element is then situated above the support with the pointed region
autoaligned with the block.
[0027] According to one embodiment, the at least one projection and
the remainder of the at least one element comprise one and the same
first material.
[0028] The at least one element can comprise several projections,
each possessing a pointed region.
[0029] According to another aspect, there is proposed an integrated
circuit comprising at least one device such as defined
hereinabove.
[0030] The integrated circuit can comprise for example at least one
capacitor, at least one electrode of which is formed by the at
least one pointed element of the device.
[0031] According to one embodiment, the at least one element of the
device is metallic and is situated on at least one of the
metallization levels of the interconnection part (BEOL) of the
integrated circuit.
[0032] The use of pointed elements, in particular metallic, in an
integrated circuit can find numerous applications.
[0033] Thus, in addition to an application to a capacitor, a
pointed element such as this can be used to release a beam of a
mechanical system for electrical switching or else to reduce the
contact area, and therefore the risk of sticking, of a body moving
on a plane wall, such as for example in a system for detecting
orientation of the integrated circuit.
[0034] More precisely, according to one embodiment, the integrated
circuit comprises, within the interconnection part (BEOL), a
mechanical system for electrical switching comprising in a housing
at least one first thermally deformable assembly including a beam
held in at least two different places by at least two arms secured
to edges of the housing. The beam and the arms are metallic and
situated within one and the same first metallization level. The
system also comprises an electrically conducting body. The first
assembly has at least one first configuration when it has a first
temperature and a second configuration when at least one of the
arms has a second temperature different from the first temperature.
The beam is remote from the body in one of the configurations and
in contact with the body and immobilized by the body in the other
configuration so as to be able to establish or prohibit an
electrical link passing through the body and through the beam. The
first assembly is activatable to pass from one of the
configurations to another. The mechanical system furthermore
comprises a release mechanism configured to release a beam
immobilized by the body and comprising the at least one pointed
element whose at least one pointed region is directed towards the
body, as well as a way to generate at the level of the at least one
pointed region an electrostatic field.
[0035] According to another embodiment, the integrated circuit can
comprise, within the interconnection part, at least one mechanical
system for detecting spatial orientation and/or change of
orientation of the integrated circuit. This mechanical system
comprises a housing whose walls comprise metallic portions produced
within various metallization levels. The housing comprises a floor
wall and a ceiling wall. The detection system also comprises a
metallic piece housed in the housing and mobile inside the housing.
A check mechanism is defines an evolution zone inside the housing
for the metallic piece and comprises at least two electrically
conducting elements disposed at the boundary of the evolution zone.
At least one of the floor and ceiling walls incorporates the at
least one element directing its pointed region towards the metallic
piece inside the evolution zone. The piece is configured so as,
under the action of gravity, to come into contact with the at least
two electrically conducting elements, in response to at least one
given spatial orientation of the integrated circuit. The system
also comprises a detector to detect an electrical link passing
through the piece and the at least two electrically conducting
elements.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] Other advantages and characteristics of the invention will
be apparent on examining the detailed description of wholly
non-limiting modes of implementation and embodiments, and the
appended drawings in which:
[0037] FIGS. 1 to 11 illustrate various modes of implementation and
embodiments of a device and of an integrated circuit according to
the invention,
[0038] FIGS. 12 to 17 illustrate another embodiment of an
integrated circuit according to the invention, and
[0039] FIGS. 18 and 19 illustrate another embodiment of an
integrated circuit according to the invention.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0040] In FIG. 1, the reference SP designates a support or
substrate, (for example silicon, polysilicon, silicon oxide,
etc.).
[0041] As will now be seen in greater detail, a pattern comprising
hollows and salient blocks (or bumps) will be produced in this
support.
[0042] In this regard, as illustrated in FIG. 1, the location of
the hollows of the pattern is defined in a conventional manner by a
photolithography step using a photosensitive resin A.
[0043] Next, an etching of the support SP is undertaken in a
conventional manner between the resin pads so as to form the
hollows CRX of the pattern (FIG. 2).
[0044] After removal of the resin blocks, the support SP is
obtained. As illustrated in FIG. 3, the support SP comprises
salient blocks BLC separated by hollows CRX.
[0045] Next, as illustrated in FIG. 4, a layer CH1 of a first
material B is formed on the support SP. The layer CH1 comprises
projections formed above and autoaligned with the subjacent salient
blocks BLC. In this example, the projections are in the form of
domes DM.
[0046] This layer CH1 therefore forms an element ELM resting on the
support SP and comprising several projections DM.
[0047] This element ELM and its projections DM are formed of a
first etchable material B which may be for example silicon,
polysilicon, silicon dioxide, silicon nitride, or else a metal such
as aluminum or tungsten, without this list being exhaustive.
[0048] By way of indication, when the first metal forming the layer
CH1 is aluminum, the deposition of this metal can be a Physical
Vapor Deposition (termed "PVD deposition"). When the first material
is an oxide, it is then possible to use a Chemical Vapor Deposition
(termed "CVD deposition").
[0049] Such depositions are conventional and known per se.
[0050] In the following step, illustrated in FIG. 5, a layer CH2 of
a second material C is formed on the structure obtained in FIG. 4.
The second material C is also etchable and in this example
possesses a planar upper surface. This formation can be performed
in various ways, for example by depositing a planarizing material
or else by performing a compliant deposition of this material C
followed by a mechanochemical polishing.
[0051] By way of nonlimiting example, it is possible to use as
planarizing material a material used in the so-called BARC
anti-reflection layers. Thus, it is possible to use, for example, a
material of the type SiO.sub.xN.sub.y. When oxide is used as
material C, it is possible to deposit it by a so-called HDP (High
Density Plasma) method or else to perform a compliant oxide
deposition followed by a mechanochemical polishing.
[0052] Be that as it may, the second material C should be able to
be etched less rapidly than the first material B.
[0053] Indeed, it is this difference in etching speed or this
selectivity of etching, that will allow the creation of a pointed
region in each dome DM.
[0054] More precisely, on the basis of the structure illustrated in
FIG. 5, a removal of the upper part of the layer CH2 is undertaken,
so as to abrade the crown of each concave part, as illustrated in
FIG. 6. At this juncture, around each concave part DM and between
two adjacent concave parts is a zone Z1 filled with the second
material C.
[0055] Next, as illustrated in FIG. 7, a selective, isotropic or
anisotropic, etching GRV of the material B and of the material C is
undertaken so as to open in each concave projection DM, a crater
CRT.
[0056] By way of indication, the selectivity of the etching can be
of the order of 1 for 2 or of 1 for 4.
[0057] Thus, for example, when the first material B is polysilicon
and the second material C is a material of BARC type, it is
possible to use plasma etching using a ClHBrO.sub.2 plasma. This
etching is typically performed at 60.degree. C. and the selectivity
is then of the order of 1/2.
[0058] When the first material B is aluminum, and the second
material C is also a material of BARC type, a BCl.sub.3ArO.sub.2
plasma can be used as plasma for the etching. This time the etching
is performed at 40.degree. C. and here again the selectivity is of
the order of 1/2.
[0059] It should be noted that to pass from the structure of FIG. 5
to that of FIG. 6, that is to say to remove the upper part of the
layer CH.sub.2 of the second material C, it is possible either to
use specific etching and then to use selective etching when in the
situation of FIG. 6, or else to use right from the outset the
etching which will be used to selectively remove the materials B
and C.
[0060] When the structure is in the state illustrated in FIG. 6,
the selective etching GRV hollows out the first material B more
deeply than the second material C, creating at the start a narrow
crater. Next, as the material C of each zone Z1 is etched, an
additional part of the dome DM is uncovered, and then etched by the
etching GRV. Thus, in tandem with the etching operation GRV, the
crater CRT is hollowed out and widened. The dimensions of the
crater therefore depend on the selectivity of etching and the
duration of etching.
[0061] On completion of the etching operation GRV, the structure
illustrated in FIG. 7 is obtained, in which the pointed element ELM
comprises the lower part of the layer CH1, crenellated, as well as
concave projections DM comprising, in their upper part, a pointed
region RGP whose internal wall PIT limits a crater CRT. Moreover,
the opening OV of the crater is smaller than the distance d,
reckoned at the level of the bottom of the crater, between two
points of the external wall PXT of the pointed region which are
substantially opposite with respect to the center of the
crater.
[0062] The pointed region RGP broadens out therefore from the
pointed end towards the base the further one recedes from the
center of the crater.
[0063] The external wall PXT of the pointed region exhibits here a
concave profile extending from the opening OV of the crater while
directing its concavity towards the crater.
[0064] Moreover, the pointed region RGP is autoaligned with the
subjacent salient block BLC of the support SP, that is to say the
axis of symmetry of the block BCL coincides exactly or nearly with
the axis of symmetry of the pointed region RGP.
[0065] In general, it is possible thereafter to undertake total
removal of the material C situated in the zones Z2 between the
pointed regions. This can be performed by a totally selective
etching aimed this time at etching the material C without etching
the material B.
[0066] It is also possible in certain applications, as will be seen
in greater detail hereinafter, to also remove by a selective
etching operation, the support SP supporting the element ELM so as
for example to form a metallic beam in the BEOL part of an
integrated circuit.
[0067] In FIG. 8, the support SP comprises active zones ZA, of
silicon or polysilicon, mutually separated by isolating regions
RIS, for example of the shallow trench type (STI: Shallow Trench
Isolation). Each active zone is surmounted by a gate oxide OX. The
isolating regions RIS have been slightly etched in such a way that
the active regions ZA surmounted by the gate oxides OX form the
salient blocks leading to the formation of the domes of the layer
CH1 of the first material.
[0068] The layer CH1 is surmounted by the layer CH2. In the example
described here, the layer CH1 can be polysilicon while the layer
CH2 is here again for example a material of BARC type.
[0069] In a manner analogous to what was described hereinabove, the
etchings of the materials of the layers CH1 and CH2 are undertaken
so as to form in the layer CH1 pointed regions RGP delimiting
craters CRT, the pointed regions RGP being autoaligned with the
subjacent active zones.
[0070] It will thus be possible, after subsequent etching
treatments, to delimit gates equipped with tips. As a variant,
these etching treatments making it possible to delimit the gates
can be performed before the formation of the tips.
[0071] It is seen in FIG. 10 that the etching of the zones RIS has
caused a hollowed profile CRP between the edge of the active zone
ZA and the edge of the isolating region RIS. Therefore, on account
of the compliant deposition of the layer CH1 and the selective
etching, the crater CRT exhibits a hollowed part CR1 at the foot of
the internal wall of the pointed region.
[0072] By way of indication, the method makes it possible to obtain
heights of tips of from 300 to 400 Angstroms without this range of
values being limiting.
[0073] It is possible, as illustrated in FIG. 11, to produce within
an integrated circuit a capacitor CDS. At least one of whose
electrodes, here the lower electrode, comprises a pointed
element.
[0074] More precisely, in this example, the pointed element ELM
comprises a substrate SP, of for example silicon dioxide,
surmounted by the first layer CH1, of for example polysilicon,
comprising several pointed regions and forming the lower electrode
of the capacitor CDS. A dielectric layer CH3 is thereafter
deposited on the layer CH1 and the second electrode CH4 of the
capacitor, for example also of polysilicon, is thereafter deposited
on the dielectric layer CH3.
[0075] A capacitor having an increased inter-electrode area
relative to a capacitor whose two electrodes are plane is therefore
obtained. And, for equal capacitive value, it is therefore possible
to reduce the surface area of the capacitor on the silicon, for
example of the order of several tens of percent.
[0076] Reference is now made more particularly to FIGS. 12 to 17 to
illustrate an application of a pointed element to a mechanical
switching system disposed in the interconnection part PITX (or
BEOL) of an integrated circuit.
[0077] An exemplary mechanical switching system is described in
French patent application No. 1161410.
[0078] Certain characteristics thereof are now recalled
hereinafter.
[0079] Referring to FIG. 12, which includes FIGS. 12A and 12B, it
is seen that the mechanical switching system or switch CMT here
comprises a first assembly ENS1 produced within one and the same
metallization level Mi of the interconnection part PITX of the
integrated circuit CI.
[0080] This part PITX is situated above the substrate SB.
[0081] The switch CMT is in this example metallic, for example
aluminum.
[0082] The switch CMT here comprises an assembly ENS1 in the form
of an asymmetric cross. This assembly ENS1 comprises a first arm
BR1A and a second arm BR1B secured to a beam PTR, also dubbed the
"central pointer", at two locations EMPA and EMPB respectively
situated on two opposite faces of the beam PTR. These two locations
EMPA and EMPB are spaced a distance d apart.
[0083] FIG. 12A shows the switch CMT, and more particularly the
assembly ENS1 encapsulated in an isolating region RIS while FIG.
12B shows the same assembly after etching of the isolating region
so as to release the arms BR1A and BR1B as well as the beam
PTR.
[0084] The assembly ENS1, thus released, therefore extends inside a
housing LG resulting from the removal of the isolating region RIS,
the two arms BR1A and BR1B being secured to the edges BDA and BDB
of the housing.
[0085] It was shown in the article by R. Vayrette et al. entitled:
"Residual stress estimation in damascene copper interconnects using
embedded sensors", Microelectronics Engineering 87 (2010) 412-415,
that after de-encapsulation of an assembly of this type, there is
stress relaxation, which causes a residual longitudinal deformation
of the arms causing a deviation a of the pointer, here
clockwise.
[0086] More precisely, assuming an arm of constant width Wa, the
deviation a is expressed by the following formula:
a = d L L 0 ( L - L 0 ) d 2 ( 2 L - L 0 ) + 4 3 W a 2 L 0
##EQU00001##
where L.sub.0 is the length of the arm after relaxation,
[0087] L.sub.0 is equal to
L 1 + .sigma. E ##EQU00002##
where .sigma. designates the residual mean longitudinal stress and
E the Young's modulus of the material.
[0088] .sigma. is determined experimentally on the basis of
measurements performed on test structures exhibiting various values
of d and various values of Wa.
[0089] According to the applications which will be envisaged, and
especially according to the precision desired, for example in the
case of temperature detection, it will be possible to take account
or not take account of this residual deviation a of the pointer
PTR.
[0090] In this regard, and in a general manner, knowing the thermal
expansion coefficient of the material forming the expansion arms,
the geometry of the arms, especially their length and their width
as well as their thickness, and the spacing d between the two
fixing points, it is readily possible to simulate, especially by
calculations of moments of forces, the deviation of the pointer PTR
during a temperature rise or a temperature fall.
[0091] In the embodiment illustrated in FIG. 13 and FIG. 14, the
arms BR1A and BR1B of the assembly ENS1 are fixed in the vicinity
of a first end zone of the beam PTR, the other end zone ZXT of this
beam PTR being free. The switch CMT moreover comprises an
electrically conducting body CPS here comprising a cantilever beam
PTL secured to a part BDC of an edge of the housing LG, as well as
a metallic appendage VX situated at the free end of the beam
PTL.
[0092] As seen more particularly in FIG. 14, the beam PTR (as well
as the arms BR1A and BR1B of the assembly ENS1) is produced within
a first metallization level, namely here the metallization level N
while the cantilever beam PTL of the body CTS is produced within
another metallization level different from the first metallization
level, in this instance the metallization level N+1.
[0093] Moreover, the appendage VX of the body CPS is produced
within the level of vias, situated between the metallization levels
N and N+1. The appendage VX is produced in a manner analogous to
that used for producing the vias in the BEOL part of the integrated
circuit. That said, the appendage VX comprises a part VXA extending
between the two metallization levels N and N+1, and prolonged by an
end part VXB extending in part within the first metallization level
N. This end part VXB broadens out towards the cantilever beam
PTL.
[0094] In FIG. 13, the assembly ENS1 is in a first configuration,
for example when it is at ambient temperature. During a rise in
temperature of the integrated circuit, and consequently of the
assembly ENS1, the arms BR1A and BR1B of the assembly expand and
therefore, the end ZXT of the beam PTR undergoes a motion MVT1 that
is manifested here by a sagging. Moreover, the cantilever beam PTL
of the body CPS expands and its free end, supporting the appendage
VX, moves according to a motion MVT2.
[0095] Therefore, and having regard to the fact that the amplitude
of these motions can readily be calculated as indicated hereinabove
as a function especially of the geometry of the arms and of the
coefficients of expansion of the materials, the spacing ED between
the end ZXT of the beam PTR and the via VX, in the first
configuration, is determined in such a way that beyond a certain
temperature, the assembly ENS1 takes a second configuration in
which, as illustrated in FIG. 14, the end zone ZXT of the beam PTR
comes from the other side of the via VX, thus being immobilized and
hooked by the via VX of the body CPS.
[0096] Passage of the end zone ZXT of the beam PTR from one side to
the other of the via VX is rendered possible especially by the
beveled shape of the end part VXB of the via VX and also by the
fact that the beam PTL mounted cantilever fashion, will inflect
when the end zone ZXT comes into contact with the beveled part VXB
of the via VX, and allow, by this raising, passage of the zone ZXT
on the other side of the via.
[0097] Once the zone ZXT has passed the other side of the via
(second configuration) the via VX can descend again and hook the
zone ZXT by being in contact with the latter.
[0098] And, in this second configuration, the beam PTR of the
assembly ENS1 cannot naturally return to its first configuration
even if the temperature returns to the initial temperature since
the beam PTR is locked by the via VX.
[0099] In the second configuration, it therefore becomes possible
to establish an electrical link passing through the body CPS and
through the beam PTR.
[0100] Check mechanism MCTL, disposed for example in another part
of the integrated circuit, can thus test the establishment or
otherwise of this electrical link.
[0101] In this regard, it will be possible to use any conventional
and known means. The mechanism MCTL can for example comprise a
generator able to generate a supply voltage on the edge BDA of the
housing LG and verify, for example with the aid of logic circuits,
that the current thus generated is indeed present at the level of
the edge BDC of the housing, the edges BDA and BDC being
electrically insulated.
[0102] Whereas in the embodiment illustrated in FIGS. 13 and 14,
the switch CMT possessed a naturally irreversible state, as
explained hereinabove, it is possible, as illustrated in FIGS. 15,
16 and 17, to provide for the switch furthermore to comprise a
mechanism MLB configured to release a beam immobilized by the body
CPS.
[0103] In the example illustrated in FIGS. 15 to 17, the mechanism
MLB here comprise, as illustrated in FIG. 16, a first arm BRS1
formed by a via, and a second arm BRS2 formed here by a metallic
portion situated at the metal level N and by two vias disposed
either side of this metallic portion.
[0104] The arms BRS1 and BRS2 are secured to the beam PTL in the
vicinity of the end opposite from that to which the appendage VX is
linked.
[0105] These arms BRS1 and BRS2 make it possible to immobilize the
beam PTL and to permit simply as will be seen hereinafter, vertical
sagging.
[0106] In addition to these arms BRS1 and BRS2, the mechanism MLB
also comprise, as illustrated in FIG. 16, another beam PLB held
fixed at its right end, for example by way of a via. This beam PLB,
produced at the metal level N, comprises in its left part a
metallic, for example aluminum, pointed element ELM having a
structure analogous to that which was described with reference to
FIG. 7 for example. It will be noted here that the element ELM is
ridded here of the subjacent support that served for its formation,
as well as of the second material that served for the formation of
the pointed regions. The pointed regions RGP are directed towards
the beam PTL of the body CPS.
[0107] The mechanism MLB also comprise a mechansim GENB able to
generate a potential difference between the beam PTL and the beam
PLB and thus to create at the level of the tips of the pointed
element ELM an electrostatic field so as to create a repulsion
effect which will make it possible to inflect the beam PTL upwards
(motion MVT4). And, it is seen in FIG. 17 that on account of the
sagging of the beam PTL, the beam PTR is freed from its
immobilization constraints by the appendage VX and therefore
returns to its initial configuration (motion MVT3).
[0108] The switch CMT is then as it were reinitialized and can be
used again to for example detect the crossing of a temperature
threshold or a surge.
[0109] The switch CMT and especially the assembly ENS1 as well as
the body CPS are produced by carrying out conventional steps for
fabricating metallization levels and vias. The levels of vias are
also used to form a protection wall for the oxide etching which
will allow de-encapsulation of the assembly ENS1 and of the body
CPS.
[0110] Moreover, the beam PLB and especially the element ELM is
produced in a manner analogous to what was described hereinabove
with reference to FIGS. 1 to 7 by using for example as subjacent
support silicon dioxide etched so as to form a pattern of salient
blocks allowing the production of the aluminum layer and its
projections.
[0111] Reference is now made to FIGS. 18 and 19 to illustrate a use
of a pointed element in a system for detecting the spatial
orientation and/or the change of this orientation of an integrated
circuit. An exemplary system for detecting orientation and/or
change of orientation is described in French patent application No.
FR1252988.
[0112] Certain characteristics thereof are recalled here.
[0113] Referring to FIG. 18, it is seen that the system DIS for
detecting spatial orientation and/or the change of orientation of
the integrated circuit CI is produced within several metallization
levels (here three metallization levels M.sub.i-1, M.sub.i,
M.sub.i+1 and two levels of vias V.sub.i-1, V.sub.i) of the
interconnection part RITX (BEOL) of the integrated circuit CI. The
metal is for example aluminum.
[0114] The system DIS comprises a housing or cavity CV whose walls
comprise metallic portions produced within various metallization
levels.
[0115] In the present case, the system DIS comprises a floor wall
PLCH produced at the metallization level M.sub.i-1, a ceiling wall
PLFD produced at the metallization level M.sub.i+1 and a lateral
wall PLT comprising metallic portions produced at the metallization
level M.sub.i and vias produced at the levels of vias V.sub.i-1 and
V.sub.i.
[0116] The system DIS also comprises a metallic piece 1 housed in
the housing CV and mobile inside this housing.
[0117] The system DIS also comprises a check mechanism, for example
pillars PLR, defining inside the housing an evolution zone ZV for
the metallic piece and comprising less two electrically conducting
elements, for example the pillars PLR, disposed at the boundary of
the evolution zone.
[0118] The metallic piece 1 is configured so as, under the action
of gravity, to come into contact with the pillars PLR in response
to at least one given spatial orientation of the integrated
circuit.
[0119] The integrated circuit also comprises detection mechanism
MDT configured to detect an electrical link passing through the
piece and the electrically conducting elements PLR.
[0120] This mechanism MDT is, in the example described, connected
to the pillars PLR by a connection CNX which can be produced in
various ways, for example by way of vias and of metallic tracks at
different levels of the integrated circuit.
[0121] Moreover, in certain cases, it may be necessary to
electrically insulate the pillars PLR from the bottom wall and
floor wall PLCH and PLFD. In this case, an insulating space ESP is
made around the metallic portion of the wall PLCH which supports a
pillar PLR.
[0122] The mechanism MDT, supplied between a supply voltage Vdd and
earth, are of conventional and known structure. It is possible in
this regard to use any appropriate logic circuit.
[0123] The mechanism MDT has been represented in a schematic manner
outside the integrated circuit. This could actually be the case if
this mechanism MDT is produced as a distinct component of the
integrated circuit. Of course, this mechanism MDT could also be
integrated into the integrated circuit CI.
[0124] Initially, the piece 1 is in this example a metallic portion
of the metallization level Mi, encapsulated in an isolating region
part. After removal of this isolating region part, so as to form
the cavity CV, the piece 1 becomes mobile and, in the case
illustrated in FIG. 18, falls by gravity onto the floor wall
PLCH.
[0125] When the integrated circuit is in a horizontal position, as
illustrated in FIG. 18, the piece 1 and the pillars PLR are
mutually arranged in such a way that the piece 1 does not come into
contact with at least two pillars PLR. No electrical link is
detected by the detection mechanism MDT. This is consequently
representative of a flat integrated circuit CI.
[0126] On the other hand, if the integrated circuit CI is tilted,
the piece 1 will then under the action of gravity slide on the
floor wall PLCH so as to contact at least two pillars PLR. An
electrical link between these two pillars PLR will be able to be
detected by the mechanism MDT. As a function of the location of the
pillars PLR with which the piece 1 has come into contact, it is
then possible to detect that the integrated circuit CI has taken a
given orientation, or at the very least an orientation included in
a given range of orientations.
[0127] So as to limit a risk of sticking of the piece 1 on the
floor wall PLCH and consequently to favor the sliding of the piece
1 on this floor wall, it is particularly advantageous, as
illustrated in FIG. 19, to provide for this floor wall PLCH to
incorporate a pointed element ELM directing its pointed regions
towards the metallic piece 1 inside the evolution zone ZV. The
element ELM is ridded of the subjacent support that served for its
formation as well as of the second material that served for the
formation of the pointed regions.
[0128] Here again the system DIS is produced with conventional
steps for fabricating metallization levels and vias. The levels of
vias are also used to form a protection wall for the oxide etching
which will allow the formation of the cavity CV.
[0129] Moreover, the element ELM of the floor PLCH is produced in a
manner analogous to what was described hereinabove with reference
to FIGS. 1 to 7 by using for example as subjacent support silicon
dioxide etched so as to form a pattern of salient blocks allowing
the production of the aluminum layer and its projections.
* * * * *