WO2021005394A1

WO2021005394A1 - Pressure measurement sensor and manufacturing process of a differential pressure measurement sensor

Info

Publication number: WO2021005394A1
Application number: PCT/IB2019/000824
Authority: WO
Inventors: Patrice Rey; Takehiko Ogawa; Ryoichi Takayama
Original assignee: Commissariat A L'energie Atomique Et Aux Energies Alternatives; Panasonic Corporation
Priority date: 2019-07-09
Filing date: 2019-07-09
Publication date: 2021-01-14

Abstract

Pressure measurement sensor and manufacturing method for manufacturing MEMS and/or NEMS differential pressure measurement sensor assemblies, each assembly comprising one pressure sensor with at least one first membrane (304) and at least one second membrane (304), each suspended from a support substrate (302),and a connection substrate (354) bonded to the support substrate (302), through which the first (304) and second (306)membranes are subjected on one face to a first and second pressures to be detected. The manufacturing method comprises a step of manufacturing collectively several pressure sensors from a wafer and a step of manufacturing collectively several connection substrates from another wafer and the step of bonding the wafers prior to the separation of the pressure sensors.

Description

PRESSURE MEASUREMENT SENSOR AND MANUFACTURING PROCESS OF A

DIFFERENTIAL PRESSURE MEASUREMENT SENSOR

DESCRIPTION

TECHNICAL FIELD AND PRIOR ART

The present invention relates to process for manufacturing a microelectromechanical and/or nanoelectromechanical differential pressure measurement sensor and to a pressure measurement sensor.

A differential pressure measurement sensor makes it possible to measure a difference between two pressures, said two pressures being any pressures.

Document US9528895 describes a differential pressure measurement sensor comprising a first membrane subjected to a first pressure on one face and a reference pressure on another face, a second membrane subjected to a second pressure on one face and to the reference pressure on another face. A beam links the two membranes on the side of the faces subjected to the reference pressure, the beam being articulated on a support by a pivot link. Measurement means are sensitive to the movement of the beam caused by the difference in pressure seen by the two membranes.

The pivot link is shifted with respect to the rigid beam. It is distinct from the rigid beam and its cross-section is different from the cross-section of the rigid beam. This pivot link is connected to the rigid beam between the two areas to which the membranes are secured. The axis of the pivot link is orthogonal to the rigid beam.

The sensor offers great robustness since the measurement means are isolated in the cavities from the reference pressures, so they are not in contact with the exterior environment. The risks of short-circuit and/or of corrosion are avoided. Moreover, it makes it possible, by taking the same reference pressure for the two membranes, to measure directly the differential pressure. In fact, the implementation of the beam makes it possible to cancel static pressure in the measurement and thus provide a differential pressure value directly. The sensor according to the invention thus has an advantage in terms of measurement dynamic compared to differential pressure sensors implementing absolute pressure sensors.

This differential pressure sensor provides great performances. One face of the first membrane and one face of the second membrane are subjected to first and second pressures respectively. The face of the first membrane delimits partially a first space at the first pressure and the face of the second membrane delimits partially a second space at the second pressure. The first and second pressures are brought in the first and second spaces through connections to two locations between which the differential pressure is requested to be measured.

A lower substrate comprising two through holes is individually bonded to the support substrate of the sensor, the both through-hole are connected to connections providing first and second pressure. The distance between the through holes is the distance between the first and second membrane. It is, for example is between 100 pm and 300 pm.

Such a bonding is quite difficult to be carried out. Indeed depositing glue between the two membranes to ensure a perfect hermeticity between the two pressure ports is quite challenging because there is a risk for the glue to overflows towards the membranes. In addition the assembly process requires a precise control, because the devices can accept only few pm misalignment during the adhesion step.

DESCRIPTION OF THE INVENTION

It is consequently an aim of the present invention to offer a manufacturing process for packaging a differential pressure sensor which is easiest with respect to the manufacturing process of the prior art.

It is an additional aim of the present application to offer a pressure measurement sensor which can be made with an easier manufacturing process.

The above-recited aim is achieved by a manufacturing process in which the step of bonding the support substrate and the connection substrate is made prior to the wafer dicing step to separate the sensors from each other Thanks to the invention, the deposit of the bonding means is made collectively on a wafer commonly used in microelectronic, the manufacturing equipment used in microelectronic being able to define very small glue patterns accurately located.

Preferably the bonding means are made on the connection substrate.

The bonding means may be a glue or by an eutectic metal layer.

In other words, the bonding step of the connection substrate to the support substrate is a collective step and not an individual one.

The differential pressure measurement sensor comprises a support substrate with a first and second through holes, above which the first and second membranes are suspended respectively. In one embodiment, the sensor also comprises an additional substrate, called connection substrate, bonded to the support substrate, and configured to connect the each one of the first and second membrane to the first and second pressures respectively. The connection substrate comprises sealing means to isolate in a leak tight manner the first and second pressure from each other, these sealing means being made on the connection substrate prior to the assembly of the connection substrate and the support substrate.

Very advantageously the connection substrate is such that the pneumatic connection of the sensor to the outside is easiest than the prior art sensors. The macroscopic handling is simpler.

In one very advantageous embodiment, said connection substrate comprises also a first and second through passages which are designed such that, on the face of the connection substrate bonded to support substrate, one end of the first through passage intersects the first through hole and one end of the second though passage intersects the second through hole, and the second ends of the first and second through passages are separated from a distance greater than the distance between the through holes. This distance is for example between 1 mm to 5 mm.

In another embodiment, one through passage is made in the connection substrate to pneumatically connect one through hole to the outside, and a lateral passage is made between the support substrate and the connection substrate through which the other through hole is pneumatically connected to the outside. In another embodiments, both through holes are pneumatically connected to the outside through two lateral passages made between the support substrate and the connection substrate.

In other words, an additional substrate is used to increase the distance between the pressure inputs of the differential pressure sensor and this additional substrate allows. The distance between the membranes is quite small, but the overall outer dimensions of the sensor are great, about 1 mm to 5 mm. the inventors uses these great dimensions to achieve pneumatic connections suitable for macroscopic use.

Thanks to these use of an additional substrate, which is structured before being bonded to the measuring part of the sensor, there is less constraint in the choice of the distance between the pneumatic connections.

One subject-matter of the invention is a method for manufacturing a pressure measurement sensor assembly comprising:

a) manufacturing a set of pressure measurement sensors from a first wafer, each pressure measurement sensor comprising at least one semi-conductor layer, such that each pressure measurement sensor comprising at least one first membrane and at least one second membrane, each first and second membrane is suspended from a support substrate, the first membrane having a face subjected to a reference pressure and a second face subjected to a first pressure to be detected, the second membrane having a first face subjected to the reference pressure and a second face subjected to a second pressure to be detected, the support substrate comprising a first through hole and a second through hole above which the first membrane and the second membrane are suspended respectively,

a rigid beam of longitudinal axis articulated with respect to the substrate by a pivot link around an axis said pivot link being located in a plane parallel to the first membrane and the second membrane which is different from the plane of the first membrane and the second membrane, said beam being in contact via a first zone to the first membrane and via a second zone to the second membrane such that the pivot link is situated between the first zone and the second zone of the beam, a cap delimiting with the substrate on the side of the first faces of a first and second membranes at least one hermetic cavity

at least one movement sensor for measuring the movement of the rigid beam around the axis, said sensor being arranged at least in part on the substrate, said sensor being arranged in the at least one hermetic cavity,

b) manufacturing a set of connection substrates from a second wafer, in which bonding means for bonding each pressure measurement sensor to each connection substrate are made, said bonding means being configured to isolate in tight manner the first membrane from the second membrane,

c) Making pressure measurement assemblies by bonding the first wafer and the second wafer, such that for each pressure measurement sensor, the first membrane and the second membrane are isolated in a tight manner from each other, d) Separating each pressure measurement sensor assembly from each other.

Another subject-matter of the invention is a pressure measurement sensor comprising:

a support substrate having a first and a second through holes, a first and a second membranes suspended from a first side of the support substrate and covering the first and the second through holes respectively,

a connection substrate connected to a second side opposite to the first side of the support substrate,

a rigid beam articulated with respect to the support substrate by a pivot link located in a plane parallel to the first side of the support substrate,

a cap delimiting a hermetic cavity with the support substrate on the first side of the support substrate, and

a movement sensor for measuring the movement of the rigid beam, wherein:

the rigid beam is in contact via a first zone to the first membrane and via a second zone to the second membrane such that the pivot link is situated between the first zone and the second zone of the beam, the movement sensor is arranged in the hermetic cavity and at least in part on the support substrate,

the connection substrate delimits a portion of at least one of a first and a second pressure ports with the support substrate on the second side of the support substrate, and

the first and the second pressure ports lead to the first and the second through holes of the support substrate respectively.

a cap delimiting a hermetic cavity with the support substrate on the first side of the support substrate,

a movement sensor for measuring the movement of the rigid beam, and a case accommodating the support substrate, the first and the second membranes, the rigid beam the cap and the movement sensor, wherein:

the rigid beam is in contact via a first zone to the first membrane and via a second zone to the second membrane such that the pivot link is situated between the first zone and the second zone of the beam,

the movement sensor is arranged in the hermetic cavity and at least in part on the support substrate,

a portion of a second side opposite to the first side of the support substrate is fixed to the case with an adhesive member,

the adhesive member delimits a portion of at least one of a first and a second pressure ports with the support substrate on the second side of the support substrate, and the first and the second pressure ports lead to the first and the second through holes of the support substrate respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood by means of the description that follows and the appended drawings in which:

- figures 1A and IB are top and sectional views along the line A-A respectively of an example of embodiment of a differential pressure measurement sensor with detection by suspended piezoresistive strain gauge to which the invention applies,

- figure 1C is a schematic representation of a detail of the measurement means by suspended resonant strain gauge with capacitive excitation and piezoresistive measurement of the resonance of the gauge,

- figure ID is a schematic representation of a detail of the measurement means by suspended resonant strain gauge with capacitive excitation and capacitive measurement of the resonance,

- figures 2A and 2B are top and longitudinal sectional views along the line B-B respectively of an example of embodiment of a differential pressure measurement sensor with capacitive detection to which the invention applies,

- figure 3 is a top view of an example of embodiment of a pressure measurement sensor comprising a flexible articulation along the X axis and rigid along the Z axis between the membranes and the beam,

- figure 4 is a top view of an example of embodiment of a differential pressure measurement sensor in which the pivot axis of the beam is off centre and the membranes have different diameters,

- figures 5A and 5B are top and sectional views along the line C-C respectively of another example of embodiment of a differential pressure measurement sensor comprising stops,

- figure 5A' is a top view of a variant of the sensor of figure 5A in which the pivot link comprises a single beam subjected to torsional stress, - figure 6 is a top view of an example of embodiment of a differential pressure measurement sensor in which the pivot axis is obtained by beams working through bending,

- figures 7A and 7B are top and sectional views along the line D-D respectively of another example of embodiment of a differential pressure measurement sensor with a first example of embodiment of electrical contacts,

- figures 8A and 8B are top and sectional views along the line E-E respectively of another example of embodiment of a differential pressure measurement sensor with a second example of embodiment of electrical contacts,

- figure 9 is a top view of another example of embodiment of a differential pressure measurement sensor with detection by strain gauge in which several membranes are used to detect each pressure,

- figure 10 is a top view of another example of embodiment of a differential pressure measurement sensor with detection by strain gauge having elements for stiffening the membranes to limit parasitic deformations.

- figure 11 is a longitudinal sectional view of an assembly integrating a differential pressure measurement sensor according to the invention and an inertial sensor,

- figure 12A is a longitudinal sectional view of an embodiment of a sensor assembly according to the invention,

- figure 12B is a sectional view along plane A-A of the sensor of figure

12 A,

- figure 13A is a longitudinal sectional view of another embodiment of a sensor assembly according to the invention,

- figure 13B is a sectional view along plane B-B of the sensor of figure 13A,- figures 14A to 14N are top and longitudinal sectional views of different steps of forming a sensor assembly of figure 13Aaccording to an example of manufacturing method,

- figures 15A to 15E are diagrammatic representations of sectional views of different pressures sensors according to an embodiment, - figures 16A to 16D are diagrammatic representations of sectional views and side views different pressures sensors according to another embodiment

- figures 16A' to 16D' are example embodiments of tridimensional views of the support substrate of sensors 16A to 16D respectively.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

In the description that follows, the sensors are of MEMS and/or NEMS type, however they will be designated uniquely by the term "sensor" for reasons of simplicity.

Elements and parts having the same function and the same shape will be designated by the same references.

The differential pressure measurement sensor is intended to measure the pressure difference between the pressures PI and P2.

The sensors represented by figures 1A to 11 and described below are examples of sensors to which the invention applies.

Figures 1A and IB are top and sectional views respectively of an example of embodiment of a differential pressure measurement sensor, comprising a substrate 2, two separate membranes 4, 6 suspended from the substrate.

Each membrane 4, 6 is such that it deforms under the action of a pressure difference on its two faces.

In the example represented, the membrane 4 is subjected on one of its faces 4.1 to a reference pressure REF and on the other of its faces 4.2 to the pressure PI.

The membrane 6 is subjected on one of its faces 6.1 to the reference pressure REF and on the other of its faces 6.2 to the pressure P2.

In the example represented, the two membranes are subjected to the same reference pressure. But a sensor with different reference pressures does not go beyond the scope of the present invention.

In the example represented, a cavity 14 hermetic to gases is made in which reigns the reference pressure PREF. In the example represented, the membranes 4, 6 have the shape of a disc but they could have any other shape, such as a square shape, hexagonal shape... They could also have different shapes to each other. Preferably, the membranes are flat, preferably are coplanar and preferably are of same thickness.

A beam 8 of axis X is mounted articulated around a pivot link 10 of Y axis on the substrate. The Y axis is in the example represented perpendicular to the X axis. In the example represented, the beam is of rectangular section but it could be of trapezoidal section for example. The pivot link 10 is shifted with respect to the beam 8.

In the example represented, the pivot link 10 comprises two beams 10.1, 10.2 each connecting a lateral edge of the beam 10 to an anchoring pad forming advantageously an electrical contact 18. The two beams are aligned along the Y axis. The beams 10.1, 10.2 are subjected to torsional stress around the Y axis. The pivot link may comprise a single beam subjected to torsional stress as will be described below.

The beam 8 is solidly connected by each of its longitudinal ends 8.1, 8.2 to the face 4.1, 6.1 of the membrane 4, 6 respectively. The beam rigidly links the two membranes in comparison with the stiffness of the membranes. It may be envisaged that the beam is solidly connected to the membranes 4, 6 at the level of an intermediate zone between its longitudinal end and the axis of rotation Y.

It will be seen that in the case of measurement means with strain gauges, the greater the distances between the points of application of the forces on the beam and the greater the axis of rotation Y, the greater the sensitivity.

In the present application, for reasons of simplification, "substrate" is taken to mean the support substrate 2 and the layers arranged on said support substrate such as for example the layer(s) in which are formed the membranes and the beam 8.

A cap 12 is assembled on the substrate 2 on the side of the beam and defines with the substrate and the membranes the sealed cavity 14 in which is established the reference pressure REF. In the case where each of the membranes would be subjected on one face to a different reference pressure, the cap 12 would delimit two hermetic cavities with each membrane and the substrate. Advantageously, the cap 12 is sealed onto the substrate under vacuum by sealing, for example by eutectic sealing, anodic sealing, molecular sealing or SDB ("Silicon Direct Bonding"), molecular sealing or SBD using surface forces and Van der Waals forces),.., which makes it possible to obtain a good quality of vacuum, which is more reliable for example compared to plugging by deposition.

Moreover, this formation of the cavity or the cavities directly by sealing of the cap makes it possible to insert a getter material into the reference cavity or cavities, for example in the case where it is wished to have an intensive reference vacuum and which is stable over time.

The sensor also comprises means of measuring 16 the movement of the beam around the Y axis, which makes it possible to work back to the difference in this pressure P1-P2. The measurement means are shifted with respect to the membranes.

In the example represented, the measurement means are formed by two suspended strain gauges 20, situated on either side of the beam 8.

A gauge 20 is suspended between an anchoring pad 22 and an element 23.1 of Y axis aligned with the torsion beams 10.1, 10.2, projecting from a lateral edge of the beam. The other gauge 20 is suspended between an anchoring pad and electrical contact 22 and an element 23.2 of Y axis aligned with the torsion beams 10.1, 10.2, projecting from the other lateral edge of the beam 8.

The elements 23.1, 23.2 are fixed with respect to the beam 8 such that the rotation of the beam 8 corresponds to that of the elements.

Electrical contacts 25 are advantageously in the anchoring plots making it possible to supply the strain gauges. In a variant, it could be envisaged to form electrical contacts separate from the anchoring pads and the formation of a connection between the electrical contacts and the gauges.

In the example represented, the electrical contact 25 is formed on the rear face of the substrate 2. It corresponds to the contact pads 22, 16, 18. In order to simplify the representation, it is shifted. But it is in practice formed directly in line with each of the electrical contacts of the sensor. The electrical contact on the rear face is a through contact or via or TSV (Through Silicon Via). When the beam 8 pivots around the Y axis, the strain gauges 20 are deformed. The beam transforms the differential deflection of the membranes into a strain on the gauges. The differential deflection is amplified thanks to the beam forming a lever arm.

The strain amplified by the beam 8 then applies on the longitudinal ends of the gauges

The bending stiffness of the beam outside of the plane of the substrate of the beam 8 is preferably at least 10 times greater than the compressive stiffness of the gauge(s), which makes it possible to avoid a deformation of the beam and a reduction of the deformation transmitted to the beam. In the example represented, the gauges 20 are arranged on either side of the axis of rotation Y and of the beam 8. The measurement means could only comprise a single strain gauge. The implementation of two strain gauges makes it possible to carry out differential measurements, rendering the device less sensitive to external variations, for example to temperature variations.

Advantageously, the gauge(s) have a nanometric section, which makes it possible to have a higher concentration of strain and thus enhanced sensitivity.

In figures 1A and IB, the strain gauges are of piezoresistive type. The variation in resistance due to the strain that is applied to them makes it possible to deduce the movement of the beam around the Y axis and thus the pressure difference P1-P2.

The gauges are oriented such that their sensitive axis is substantially parallel to the beam and thus that it is substantially orthogonal to the axis of rotation of the linking arm. They are arranged advantageously as near as possible to the axis of rotation Y such that the axis of rotation Y is close to the point of application of the strain on the gauges. In fact, the amplification of the strain by the lever arm is all the greater when the axis of rotation is close to the point of application of the strain on the gauge.

Furthermore, the neutral line of each gauge is arranged above or below the axis of rotation of the transmission arm. To achieve this, the gauges may have a thickness less than that of the torsion and/or bending beam. For example to obtain this lower thickness from the same layers, it is possible to deposit an over-thickness on said beams.

In figures 1C and ID may be seen examples represented schematically of resonant type strain gauges.

In figure 1C, the resonant gauge 120 is suspended between the torsion beam 10.1 and the anchoring pad 22 forming electrical contact. An excitation electrode 24 is provided along one side of the resonant gauge 120 to place it in vibration. Piezoresistive means of measuring the vibration of the resonant gauge 120 are provided. It is in the example represented a piezoresistive gauge 26 suspended between the resonant gauge 120 and an anchoring pad 28 comprising advantageously an electrical contact.

The excitation electrode places in vibration the resonant gauge 120 and the variation in the vibration frequency due to the strain that is applied to the resonant gauge 120 is measured by the piezoresistive gauge 26.

In figure ID, the detection of the variation in the vibration frequency of the resonant gauge 220 is realised in a capacitive manner. The measurement means comprise an excitation electrode 24 and a detection electrode 30 forming with the resonant gauge 220 a variable capacitance capacitor. The measurement of the variation in capacitance is a function of the variation in the vibration frequency of the resonant beam 220 which depends on the strain that is applied thereto.

The operation of the pressure measurement sensoroffigures lAand lB will now be described.

When a pressure difference arises between the face 4.2 of the membrane 4 and the face 6.2 of the membrane 6, a force FI is applied to the end 8.1 of the beam, proportional to the pressure PI, and a force F2 is applied to the end 8.2 of the beam proportional to the pressure P2. In considering that the forces are of different intensities but of same direction, for example towards the inside of the reference pressure cavity, the beam 8 tips around the Y axis. If PI is greater than P2, the beam pivots counter-clockwise and if P2 is greater than PI, the beam pivots clockwise. This tipping has the effect of applying a strain to the strain gauges 20, 20. This strain is amplified due to the lever-arm effect. The strain undergone by the gauges 20, 20 is then measured with the means described above. These measurements then make it possible to determine the pressure difference between PI and P2.

In the case where the reference pressure is the same for the two membranes, the differential pressure measurement sensor makes it possible to supply the differential pressure P1-P2 directly.

The differential pressure measurement sensor makes it possible to measure pressure differences whether the pressures PI and P2 are greater than or less than or equal to PREF.

The amplification of the strain by the lever arm will be all the greater when the length of the arm between the point of application of the force by the membranes and the axis of rotation Y is high, when the axis of rotation is close to the point of application of the strain on the gauges. The smaller the section of the gauges (thickness, width), the higher will be the strain.

Thus, the sensitivity of the sensor is increased. It is thus possible to offer more efficient sensors or then to reduce the size of the sensors, for example by reducing the surface area of the membranes, while maintaining the same performance.

In figures 2A and 2B may be seen another example of embodiment of a differential pressure measurement sensor in which the detection is of capacitive type. These means are shifted with respect to the membranes.

This sensor differs from that of figures 1A and IB in that the measurement means 316 are of capacitive type.

In a preferred manner, it is a differential measurement. To achieve this, a variable capacitance capacitor is provided on each arm of the beam 8 on either side of the axis of rotation Y, supplying two capacitance measurements. The beam 8 bears a moving electrode 318 common to the two differential capacitance capacitors; two fixed electrodes 320 (represented in dotted lines) are provided on the substrate facing the moving electrode 318 on the two arms of the beam. Each fixed electrode is connected to an electrical contact 322 connected to a polarisation source and the contact of the moving electrode 318 takes place via the contact of the beam, for example at the level of the embedding of the torsion axis (plot 18 in figure 1A). The moving electrodes 318 have an out of plane movement and move away or come closer to the fixed electrodes 320. Advantageously the moving electrode 318 is arranged at the longitudinal end 8.1, 8.2 of the beam 8 the furthest from the Y axis in order to have an increased movement of the moving electrode with respect to the fixed electrode and thus increased measurement sensitivity.

In a variant, a single variable capacitance capacitor on one or the other of the arms could be provided.

The amplification of the movement of the moving electrode (with respect to the fixed electrode) by the lever arm will be all the higher when:

- the length of the arm between the point of application of the force by the membrane and the axis of rotation is small,

- the moving electrode is far from the axis of rotation Y.

In this example, the beam is solidly connected to the membranes in an intermediate zone between the axis of rotation Y and the longitudinal ends 8.1, 8.2.

When the membranes 4, 6 are deformed, the beam carries with it the moving electrodes, which move with respect to the fixed electrodes. The air gap distance between the electrode pairs varies, each variation in air gap is representative of the differential strain applied by the membranes and thus the pressure difference P1-P2. In the case of capacitive detection, the realisation of a differential measurement is easy.

Thanks to the implementation of the beam 8, the movement of of the moving electrode(s) may be amplified compared to that of the membranes 4, 6. Thus, for a given pressure difference, the variation in capacitance is increased. The sensitivity of the differential pressure measurement sensor is thus enhanced.

Advantageously, the variable capacitance capacitor(s) may also be used as actuation means to carry out a "self-test" or a self-calibration of the sensor. The implementation of these electrodes can also make it possible to enslave in position the membranes, and enable an enslaved measurement mode. This type of actuation ("self- test" function, enslavement) may advantageously be coupled to the piezoresistive detection mode described previously.

In figure 6 may be seen a variant of embodiment of the pivot link 10, in which the pivot link 410 is formed by means of beams working through bending. To achieve this, the beam comprises a hollowing out 412 in the zone where the pivot link is to be formed. The hollowing out forms a window comprising two opposite edges 412.1,

412.2 perpendicular to the X axis. Two beams 410.1, 410.2 substantially aligned along the X axis connect an embedding pad 414 to the two edges 412.1, 412.2. The beams 410.1,

410.2 are dimensioned such that the axis of rotation Y is situated on the anchoring block.

The beam 8 comprises two lateral projections 423.1, 423.2 aligned with the Y axis to which are suspended the strain gauges 420 of measurement means. The piezoresistive or resonant measurement means are similar to those described in relation with figures 1A to ID. More than two bending beams, for example four, may be implemented. Moreover, this link to bending beam may apply to a sensor with capacitive detection.

In figure 3 may be seen an example of embodiment of a differential pressure measurement sensor that differs from the examples of figures 1A to ID and 2A and 2B in that it advantageously comprises a flexible articulation 32 between the membrane 4, 6 and the beam 8. This articulation is of spring or bending beam type. In figure 3 it is a bending beam 34 which makes it possible to transmit entirely the force along a Z axis orthogonal to the X and Y axes induced by the deformation of the membranes, while limiting the parasitic force along the X axis, i.e. along the axis of the beam 8 due to this deformation. This link has a certain flexibility along the X axis so as not to hinder the deformation of the membrane, and a certain rigidity along the Z axis to transmit the entire deformation of the membrane to the arm.

In figure 4 may be seen an example of embodiment of a differential pressure measurement sensor according to the invention offering a dissymmetrical configuration. For example, the membrane 4 has a greater surface area than the membrane 6. In order to compensate for this difference on the beam, the axis of rotation Y is shifted towards the membrane 4 which has the effect of increasing the amplification of the force applied to the membrane 6 and facilitates the treatment of measurements.

In a variant, the sensor could comprise membranes of different surface area and a pivot axis at the centre of the beam and conversely membranes of same surface area but a pivot axis moved off centre.

In figures 5A and 5B may be seen another example of differential pressure measurement sensor with detection by strain gauge in which mechanical stop means are implemented between the membranes 4, 6 and the cap.

The stops 36 serve to limit the movement of the membranes 4, 6, and thus that of the beam 8, to protect the strain gauges. In fact, in the case of pressure shock, the pressure experienced by the membranes may go beyond the measurement range provided at manufacture, and the membranes 4, 6 via the beam 8 may apply a strain greater than the strain that the gauge(s) can withstand. In the example represented, the stops are formed by beams of axis parallel to the X axis and anchored on the substrate, they overlap the membranes 4, 6.

It is thus possible to set simply the level of pressure from which the movement of the membrane and thus of the arm, is limited, by positioning the stops 36 more or less near to the zones of the membranes having the maximum deformation.

It may be envisaged that the stops are above the beam and form directly a stop for the beam, for example in the case where the stops are formed directly by the cap 12 or on the cap above the beam. It may be envisaged that a single stop is implemented, for example above the membrane the most likely to experience a pressure shock.

An electrical contact 38 may be added onto the anchoring pad of the stop in order to control the potential of the stop, for example the stop may be at the potential of the membrane, which makes it possible to avoid the risk of short-circuit in the case of contact of the membrane on the stop and the risk of a parasitic electrostatic attraction of the membrane towards the stop.

Alternatively, it may be envisaged that each stop forms a measurement and/or actuating electrode for the facing membrane, for example to assure a self-test, self-calibration function, or instead to assure an enslavement in position of the beam 8. The enslavement is obtained by applying an electrostatic retraction force counteracting the pressure force exerted on the membranes. The enslavement also makes it possible to increase the measurement range, i.e. the maximum pressure difference to be measured, for a given sensitivity of the sensor.

In figure 5A', a variant of figure 5A may be seen in which the pivot link 10' is formed by a single beam 10.2 subjected to torsional stress.

In figure 9, another example of embodiment of a differential pressure measurement sensor may be seen in which each pressure PI, P2 is applied to several membranes 4, 6 respectively, the beam 8 being connected to each of the membranes 4.

In the example represented, the sensor comprises two sets of four membranes 4, 6 arranged on either side of the Y axis. The four membranes 4 are arranged by pairs on each side of the X axis, and the four membranes 6 are arranged by pairs on each side of the X axis.

The beam 8 comprises two parallel transversal elements 40 on each arm, extending on either side of the beam 14 and connected in the vicinity of their ends to a membrane 4, 6

Deformations of the four membranes 4 apply a force to an arm of the beam 8 and the four membranes 6 apply a force to the other arm of the beam 8. The total surface area of four membranes being greater than that of a single membrane, the force applied to the beam, and thus to the gauges, is increased. This embodiment is particularly interesting for strain gauge sensors, such as piezoresistive or resonant gauges.

Thus it is possible to increase the force applied to the beam by adding up the forces applied to several membranes. It will be understood that the number of membranes subjected to the pressure PI and the number of membranes subjected to the pressure P2 may be different to each other. For example, several small membranes 4 and a single large membrane 6 or vice-versa could be provided.

In figure 10 may be seen another example of embodiment of a differential pressure measurement sensor in which the membranes 4, 6 have a locally enhanced rigidity in order to reduce the deformation of the membranes 4, 6 to the benefit of the strains applied to the beam and to the strain gauge(s). The sensitivity of the sensor may thus be optimised.

In the example represented, the membranes 4', 6' are locally stiffened in the zone of large deformation by adding radial over-thicknesses 41, 61 onto the membranes 4, 6 having a similar structure to umbrella ribs. A honeycomb structure may also be suitable or any other means increasing the rigidity of the membrane. The level of stiffening is chosen in order to avoid rendering the sensor too sensitive to accelerations. Only one of the two membranes can have such stiffening means.

In figure 11 may be seen an example of integration of a differential pressure measurement sensor according to the invention and an inertial sensor. This integration is rendered possible by the fact that the differential pressure measurement sensor CP according to the invention may be formed with technologies for manufacturing inertial sensors, such as accelerometers or gyrometers formed using surface technology.

In figure 11 may be seen the differential pressure measurement sensor CP (on the left in the representation of figure 11) and an inertial sensor Cl (on the right in the representation of figure 11) comprising capacitive interdigitated combs 42, formed in the same substrate as that of the pressure measurement sensor.

The inertial sensor could in a variant be of the strain gauge type.

In the example represented, the encapsulation of the inertial sensor Cl is obtained by the formation of a cavity 44 separate from the cavity 14 of the differential pressure measurement sensor, a sealing bead 46 separating them. It may be envisaged to form only a single cavity for the two sensors CP and Cl, since said cavity is at a reference pressure.

The differential pressure measurement sensor according to the invention implements identical technologies to the technologies of manufacturing micro and nanoelectromechanical inertial sensors with interdigitated combs or with suspended strain gauges. It is then possible to pool together a large part of existing methods and to jointly integrate a differential pressure measurement sensor and one or more micro and nanoelectromechanical systems. In figures 7A and 7B may be seen a variant of embodiment of electrical connections. In this variant, the electrical connections are formed on the front face by vias 48 (or TSV (Through-Silicon Vias) through the cap on the front face of the opposite side with respect to the membranes and not on the rear face through the substrate as for the other examples represented. As for the TSV on the rear face, this variant makes it possible to recover the contacts directly inside the cavity or the cavities.

In figures 8A and 8B may be seen another variant of embodiment of electrical connections in the front face. In this variant, the electrical contacts 52 are formed in such a way that they emerge outside of the cavity or the cavities. The anchoring pads forming electrical contact 52 are such that they pass under the sealing bead between the substrate 2 and the cap 12. Access to the electrical contacts is then obtained by sawing or etching of the cap in line with the electrical contacts outside of the cavity or cavities, and the electrical connections may be easily formed. These electrical contacts are designated "saw to reveal".

Figures 12A and 12B show one embodiment of a sensor assembly made by an example of the manufacturing process. The case comprises a connection substrate 54 and a cover 62.

The support substrate 2 of the sensor comprises two through holes 2.1, 2.2. The first membrane 4 is suspended above the through hole 2.2 and the second membrane 6 is suspended above the through hole 2.1.

In figure 12A, the sensor assembly comprises a sensor according to figure 1A. Any or one of the sensors described above may be considered. The assembly also comprises a connection substrate 54 on which is attached the differential pressure measurement sensor. The connection substrate 54 is provided with two pressure ports 56, 58 passing through the thickness of the connection substrate.

The connection substrate 54 comprises a first face 54.1 bonded to the lower face of the sensor, and a second face 54.2 opposite to the first face.

Each pressure port 56, 58 comprises a first end 56.1, 58.1 and a second end 56.2, 58.2 located on the first and the second face respectively. Each one of the first end 56.1, 58.1 is located on the first face of the connection substrate 54 such that they faces at least partially the first 2.1 and second 2.2 through holes of the support substrate 2 respectively. The second ends 56.2, 58.2 of the ports 56, 58 are distant from each other by a distance D greater than the distance d between the first and second through holes 2.1, 2.2. The distance D is adapted to allow an easy connection to the outside, i.e. to the areas between which the differential pressure has to be measured.

D is for example between 1 mm and 5 mm, whereas the distance d between the through holes 2.1 and 2.2 is typical between 100 pm and 300 pm. Distance D is compatible with macroscopic handling.

In the example of figure 12A and preferably, the pressure port 56 and 58 are made by a first etching from the first end 56.1, 58.1 and by a second etching form the second end 56.2, 58.2, the two etchings being connected to each other in the thickness of the substrate and ensuring connection through the substrate. The connection substrate is affixed to the support 2 in a seal manner so as to isolate the pressure ports 56, 58. This sealing is obtained for example and advantageously directly during the step of fixing the connection substrate to the support, for example by gluing, for example with epoxy glue, or by eutectic bonding, for example Aluminium-Germanium bonding or Gold-Silicon eutectic bonding.

In case of gluing, glue beads 59 are made on the face 54.1 of the connection substrate prior to the assembly of the two substrates. In case of eutectic bonding, layers of eutectic metals (not shown) are made on the face 54.1 of the connection substrate and, if required, on the face of the support substrate prior the assembly of the two substrates.

The connection substrate is advantageously made of silicon.

In the example shown in figure 12A, the first etchings both extend in the plane of the connection substrate towards the outer side of the connection substrate to increase the distance between the second ends 56.2 and 58.2. As a variant a first etching may extend towards the outer side of the connection substrate and the other first etching may extend towards the inside of the connection substrate. The distance between the second ends would be also increased. The choice of one of these arrangements depends on the arrangement of the membranes with respect to the outer lateral face of the sensor. It may be advantageous to make one long first etching towards the outside of the stack and to make another etching towards the inside of the stack.

The length of the second etchings in the plane of the substrate may be equal to each other or different from each other.

In addition the etchings, specifically the first etchings in the example shown may have complex shape in the plane of the substrate, it may comprise at least one part of a curve and/or one or several straight portions connected to each other.

As a variant, the second etchings extends in the plane of the connection substrate and the first etchings extends through the substrate perpendicular thereto. As another variant, the first and the second etchings extend in the plane of the connection substrate until they connect to each other.

As a variant the pressure ports through the connection substrate are made in one step, and comprise a single bore perpendicular to the plane of the substrate. But in this variant the pneumatic connection of the sensor to the outside is not less complex because the distance between the ends of the pressure ports is not extended compared with that between the membranes.

In the example shown, the assembly also comprises a cover 62 sealed onto the bottom in order to protect the sensor.

In figures 13A and 13B, another embodiment of a sensor assembly according to the invention is shown.

In this embodiment, the connection substrate comprises one pressure port 66 passing through the connection substrate, and the other pressure port 68 is delimited between the first face 54.1 of the connection substrate and the rear face of the support 2.

During the mounting of the sensor on the bottom, only one sealing is formed around the through hole 2.1 by means of a bonding or glue, the membrane 4 experiencing the pressure which is shown schematically by the arrows 72. In this embodiment, the assembly of the cover 70 on the connection substrate 54 is sealed since this is the case that assures the pressure PI being brought onto the membrane 4. In a variant, a conduit is added in the cover 70, which connects the pressure port 66 to the opening for accessing the membrane 4, thereby making a sealed mounting of the cover on the cap unnecessary.

For example, communication between the first membrane 4 and the pressure port 58 is made by etching of the rear face of the support substrate 2 and/or by opening of the bead for bonding the sensor onto the connection substrate and/or by etching the first face 54.1 of the connection substrate. In the case where the section of passage left by the opening of the sealing bead is not sufficient to have acceptable load losses, it may be provided to form an additional vent by etching the support substrate and/or the connection substrate to increase the total passage section.

In case of gluing, at least one glue bead 71 is made on the face 54.1 of the connection substrate, around the first end 66.1 of the first pressure port 66, prior the assembly of the two substrates. In case of eutectic bonding, layers of eutectic metals (not shown) are made on the face 54.1 of the connection substrate 54 and, if required, on the face of the support substrate prior the assembly of the two substrates.

It will be understood that the devices of figures 12A, 12B and 13A and 13B may comprise a sensor with electrical contacts on the rear face or on the front face of the "saw to reveal" type.

The variants of embodiment have been described in considering a pressure measurement sensor with detection by piezoresistive strain gauge, but the variants of figures 3, 4, 5A, 5B, 6, 7A, 7B, 8A, 8B, 9, 10, 11, 12A, 12B, 13A and 13B apply to differential pressure measurement sensors with capacitive detection represented in figures 2A and 2B and to resonant strain gauge pressure sensors represented in figures 1C and ID.

Moreover, the different variants may be combined together without going beyond the scope of the present invention.

It will be understood that, in a preferred manner, the differential pressure measurement sensor has a symmetrical structure in particular of the membranes, of the beam..., in order to simplify the treatment of the measurements supplied by the measurement means.

Thanks to the implementation of two membranes and a rigid linking element between the two membranes, it is possible to work back to a "true" differential pressure measurement, by cancelling the common static pressure. The measurement dynamic is then notably increased compared to a device using two absolute pressure sensors.

The sensor combines both the advantages of absolute pressure sensors in which the measurement means are protected and the advantages of relative pressure sensors in terms of measurement dynamic. Furthermore, in the case where the reference pressure is a reference vacuum, thermal drifts are limited. In addition the measurement means are isolated from the external environment, for example there is no longer a risk of drift of the capacitance or short-circuit in the case of capacitive measurement means. The measurement sensor is then more robust and more reliable.

Furthermore, thanks to the linking beam which can serve as amplifying arm, a considerable gain in sensitivity is obtained, which makes it possible to form a more efficient or smaller sensor.

Moreover, the membranes and the measurement means are decoupled, which enables a separate optimisation of these two parts of the sensor.

It is also possible to carry out a differential measurement, just as well in the case of the use of piezoresistive measurement means, as capacitive or resonant measurement means. This differential measurement makes it possible to increase the signal/noise ratio and to limit the thermal sensitivity of the sensor.

In the particular case of capacitive measurement means, when the electrostatic air gap is defined by a sacrificial layer between each of the membranes and the fixed electrode, it is possible to have good control of same.

Moreover, since the moving electrodes are borne by the linking beam and the fixed electrodes are borne by the substrate, it is possible to have a high volume of the cavity or cavities under vacuum, offering a large reference volume, thus a reference vacuum likely to be more stable and more intense than those in conventional sensors. Moreover, it is easy to provide for mechanical stops assuring protection in the case of overpressure, pressure surge...

As has already been mentioned, this structure is balanced and is insensitive to accelerations.

The sensor further offers the advantage of being able to form the at least two membranes on the same layer and following the same steps. Membranes having similar or even identical mechanical properties are then obtained.

Thanks to the connection substrate, the sensor can be more easily pneumatically connected to the outside. An example of method of manufacturing the pressure measurement sensor assembly of figures 12A and 12B will now be described by means of figures 14A to 14N, figures 14A to 141 represent the element in top view and sectional view.

The emplacements of different parts of the pressure measurement sensor, during formation in the different steps represented, are designated by the references of these parts.

It involves a manufacturing method using surface technology i.e. by deposition and successive machining of thin layers on a base substrate.

The sensor and the connections substrate are manufactured separately, and thereafter attached to each other.

One starts with a SOI (Silicon on Insulator) wafer 100 on which a set of sensors will be made. The SOI wafer comprises a substrate 101, an oxide layer 103 and an upper silicon layer 102 having a thickness comprised between several hundreds of nm and several pm. The oxide layer of the SOI substrate is designated 101.

The description below relates to the manufacturing of one sensor, but at each step the whole set of sensors is made simultaneously from the wafer 100.

A lithography step is carried out in order to define the strain gauges, the torsion axis, the contour of the membranes 4, 6, the contour of the contact and embedding zones of the gauges and the torsion axis and the opening for renewal of contact on the rear face. In figure 14A, openings at the level of the contacts of the embedding pads are formed which make it possible to raise the electrical contacts between the substrate 101 and the active layer 102 during the epitaxy step, following the etching of the oxide in these openings.

An etching of the silicon layer is then carried out with stoppage on the oxide layer 103. The remaining resin is eliminated.

An etching of the oxide layer 103 is then carried out with stoppage on the substrate.

The element represented in figure 14A is obtained.

During a following step, a deposition is carried out of a S1O2 layer 106, the thickness of which may be comprised between 1 pm and 3 pm. A lithography is then carried out to protect the strain gauges, the membranes 4, 6, and to define the opening of the contact zones and embedding pads of the gauges and of the torsion axis, and the opening of the anchoring zones 64 of the beam 8 on the membranes 4, 6. An etching of the layer 106 then takes place with stoppage on the silicon of the layer 102 and on the silicon 101 of the SOI substrate. The remaining resin is eliminated. The element thereby obtained is visible in figure 14B.

During a following step, the formation of a monocrystalline or polycrystalline silicon layer 108 takes place, for example by epitaxy, having typically a thickness comprised between 1 pm and several tens of pm. An abrasion and a chemical- mechanical planarization of the layer 108 may be carried out. The element obtained is visible in figure 14C.

During a following step, a lithography is carried out on the layer 108 in order to define the opening zone of the membranes 4, 6, and the opening zone of the gauges 20, and to define the linking beam 8 and the isolation zones of the contacts. An etching of the layer 108 is then carried out with stoppage on the S1O2 layer 106. The remaining resin is eliminated. The element obtained is visible in figure 14D.

During a following step, the linking beam 8, the torsion axis and the gauges are freed by etching for example using hydrofluoric acid vapour. During this step, the layer 106 is entirely etched as well as part of the S1O2 layer of the SOI substrate. During this step, the membranes 4, 6 are not yet freed. The element obtained is visible in figure 14E. During a following step, sealing is carried out under vacuum of the cap 12 by means of a bead 13. In a variant, the sealing may be for example be of eutectic, SDB or anodic type in the case of a glass cap, i.e. without bead, the sealing being obtained by direct adhesion of the two surfaces 12 and 108. A cavity 14 is delimited between the cap 12 and the element of figure 14D.

The cap may have been prepared beforehand. The preparation of the cap may comprise the step of forming a cavity, deposition of getter, forming electrical routings or even an electronic (CMOS co-integration) in the case of eutectic sealing...

The sealed cavity around the membranes is then formed.

A thinning is then carried out of the substrate for example by abrasion on the rear face or "back-grinding" and chemical-mechanical planarization. The element obtained is visible in figure 14F.

During a following step, a deposition of a metal layer is carried out on the rear face of the substrate in order to form the contact on the rear face. Then, a lithography is carried out on this layer to delimit the contact on the rear face and finally an etching of the metal layer is carried out. The resin on the remaining metal layer is eliminated. A new lithography is carried out on the rear face to delimit the isolation zone of the contacts and the opening of the membranes 4, 6 as well as an etching of the substrate on the rear face, for example by DRIE ("deep reactive-ion etching") with stoppage on the oxide layer 103 of the SOI substrate. The remaining resin is eliminated. The element obtained is visible in figure 14G.

Finally, an etching is carried out on the rear face of the oxide layer 103 of the SOI substrate. The membranes are released. The element obtained is visible in figure 14H. At the end of this step, the both membranes of each sensor of the set of sensors are released.

The manufacturing of a set of connection substrates will be now described.

One start with a wafer 200, preferably made of silicon for all the assembly to have the same mechanical and thermal properties. As a variant substrate 200 is made of glass with thermal properties close to the ones of silicon, such a Pyrex 7740^® or Pyrex 7070^®.

The dimensions of the wafer 200 are preferably the same as those of the wafer 100. The connection substrates will be bonded collectively to the set of sensors.

The description below relates to the manufacturing of one connection substrate, but at each step the whole set of sensors is made simultaneously from the wafer 200.

The bonding means are firstly made on the front face 202 of the wafer 200. In case of eutectic bonding a layer 203 of eutectic metal, for example Au, is formed on the front face, for example by deposition and then it is etched by an appropriate chemical solution.

The microelectronic manufacturing apparatuses are able to make the bonding means of all the connection substrates at very precise location on the wafer 200, such that when the sensor wafer and the connection substrate wafer are stacked, the bonding means are precisely located between membranes without overflowing.

The element obtained is visible in figure 141. During a following step, the locations of the first ends of the pressure port are fixed by lithography. A mask 204 is formed on the front face 202 of substrate.

The element obtained is visible in figure 14J.

During a following step the substrate is partially etched, for example by deep dry etching. The through ports 56 and 58 are partially made.

And the mask 204 is removed.

The element obtained is visible in figure 14K.

A mask 206 is made, by photolithography, on the rear face of the substrate 200 delimiting the locations of the second ends 56.2 and 58.2 of the through ports.

The element obtained is visible in figure 14L.

During a following step, the substrate is etched from its rear face until the etching reaches the etching previously made from the front face. The trenches made during the first etching extend in the plane of the substrate in opposite way to each other to allow the trenches made during the second etching to be very far from each other. The first etching is not mandatory a deep etching in comparison with the second etching, and can have a little extension in the plane of the substrate. The length of the first trenches are about several hundreds of pm and the depth can be as low as lOpm up to several hundred of pm.

The element obtained is visible in figure 14M.

The connection substrate 54 is ready for being bonded to the sensor shown of figure 14H.

During a following step, the connection substrate and sensor is bonded by eutectic bonding.

During a following step the sensors are separated from each other, for example by dicing the stack of wafers with a saw.

A single sensor assembly is visible in figure 14N.

Preferably the bonding means are made before the etching of the pressure ports, because it is easier to deposit eutectic metal or glue layer and then etch it on a flat surface than on an etched surface.

An additional cap may be added as shown of figure 12A. It may be assembled to the element shown in figure 14N.

Figures 15A to 15E show pressure measurement sensors according to an example of embodiment.

Sensor of figure 15A comprise a support substrate 302 having a first 302.1 and a second 302.2 through holes, a first and a second membranes 304, 306 suspended from a first side of the support substrate 302 and covering the first and the second through holes 302.1, 302.1 respectively, a connection substrate 354 connected to a second side opposite to the first side of the support substrate 302, a rigid beam 308 articulated with respect to the support substrate 302 by a pivot link located in a plane parallel to the first side of the support substrate 302, a cap delimiting a hermetic cavity with the support substrate 302 on the first side of the support substrate 302. The sensor also comprises a movement sensor for measuring the movement of the rigid beam. The rigid beam 308 is in contact via a first zone to the first membrane 304 and via a second zone to the second membrane 306 such that the pivot link is situated between the first zone and the second zone of the beam 308. The movement sensor is arranged in the hermetic cavity 314 and at least in part on the support substrate. The connection substrate 354 comprises a first portion 356.1 of the first pressure port 356 passing through the connection substrate 354 itself and delimits a first portion 358.1 of the second pressure port 358 with the support substrate 354 on the second side of the support substrate.

The connection substrate is not a packaging. It is stacked to the device at a wafer level.

Figure 15B is a representation of a part of a pressure measurement sensor close to the sensor of figure 15A, which differs from the sensor of figure 15A in that the connection substrate 354 delimits a second portion 356.2 of the first pressure port 356 with the support substrate 302 on the second side of the support substrate 302.

Figure 15C is a representation of a part of a pressure measurement sensor close to the sensor of figure 15A, which differs from the sensor of figure 15A in that the connection substrate 354 comprises a second portion 358.2 of the second pressure port passing through the connection substrate itself 354.

Figure 15D is a representation of a part of a pressure measurement sensor which is a combination of sensors of figures 15B and 15C. The connection substrate 354 delimits a second portion 356.2 of the first pressure port with the support substrate 302 on the second side of the support substrate and comprises a second portion 358.2 of the second pressure port passing through the connection substrate itself 354.

Sensor of figure 15E differs from sensor of figure 15A, in which no pressure port passes through the connection substrate 354. The connection substrate 354 both delimits a portion of the first pressure port 356 with the support substrate 302 on the second side of the support substrate and a portion of the second pressure port 358 with the support substrate 302 on the second side of the support substrate 302. Figures 16A to 16D and 16A' to 16D' show a pressure measurement sensor according to another example of embodiment. The pressure measurement sensor of figure 16A comprises a support substrate 402 having a first and a second through holes 456, 458, a first 404 and a second 406 membranes suspended from a first side of the support substrate 402 and covering the first 402.1 and the second 402.2 through holes respectively, a rigid beam 408 articulated with respect to the support substrate 402 by a pivot link located in a plane parallel to the first side of the support substrate 402, a cap delimiting a hermetic cavity with the support substrate 402 on the first side of the support substrate 402, a mmovement sensor for measuring the movement of the rigid beam 408, and a case 474 accommodating the support substrate 402, the first and the second membranes 404, 406, the rigid beam, the cap and the movement sensor.

The rigid beam 408 is in contact via a first zone to the first membrane and via a second zone to the second membrane such that the pivot link is situated between the first zone and the second zone of the beam. The movement sensor is arranged in the hermetic cavity 414 and at least in part on the support substrate. A portion of a second side opposite to the first side of the support substrate 402 is fixed to the case 474 with an adhesive member. The adhesive member 476 delimits a portion of at least one of a first and a second pressure ports with the support substrate 402 on the second side of the support substrate, and the first and the second pressure ports lead to the first and the second through holes of the support substrate 402 respectively. An example of a support substrate 402 is shown on figure 16A'. The second pressure port 458 is a groove opening in a lateral face and in a second side of the support substrate 404.

The adhesive member 476 comprises a first portion 456.1 of a first pressure port 456 passing through the adhesive member itself 476 and delimits a first portion 458.1 of a second pressure port 458 with the support substrate 402 on the second side of the support substrate. At least the second pressure port 458 is connected to the outside by a channel delimited by the casing 474 and the outer part of the sensor.

Figure 16B shows a pressure measurement sensor close to the sensor of figure 16A, which differs from the sensor of figure 15A in that the adhesive member 476 delimits a second portion 456.2 of the first pressure port 456 with the support substrate 402 on the second side of the support substrate 402. An example of a support substrate 402 is shown on figure 16B'. The second pressure port 458 is a groove opening in a lateral face and in a second side of the support substrate 404 and the first pressure port 456 is a groove opening in the second side of the support substrate 404.

Figure 16C shows a pressure measurement sensor close to the sensor of figure 16A, which differs from the sensor of figure 16A, in that the adhesive member 476 comprises a second portion 458.2 of the second pressure port 458 passing through the adhesive member itself 476. An example of a support substrate 402 is shown on figure 16C'. The second pressure port 458 is a groove opening in the second side of the support substrate 404.

Figure 16D shows a pressure measurement sensor which is a combination of sensors of figures 16B and 16C. The adhesive member 476 delimits a second portion456.2 of the first pressure port with the support substrate on the second side of the support substrate and comprises a second portion 458.2 of the second pressure port passing through the adhesive member itself. An example of a support substrate 402 is shown on figure 16D'. The second pressure port 458 and the first pressure port 456 are grooves opening in the second side of the support substrate 404.

In sensors of figures 16C and 16D the connection of second pressure ports 456 is made directly facing the second portion 458.2, it is not delimited between the casing and the outer part of the cavity 414.

In a variant, it may be envisaged to use instead of an SOI substrate a standard substrate, on which a deposition of a sacrificial layer, for example of oxide, has been carried out, as well as a deposition of a first layer of polysilicon or SiGe-Poly. The following steps are similar to those described in starting from an SOI substrate.

The thickness values are given uniquely by way of example. Generally speaking, the sacrificial layers (made of oxide) are comprised between several tens of nm and several microns, and the active layers, such as Si, SiGe ... are comprised between several tens of nm and several tens of pm. The pressure measurement sensor assembly according to the invention may be used in all fields where a differential pressure measurement is required, for example in the medical field, with a view to determining respiratory or gaseous exchanges. It may also be used in the field of climatic engineering, with the aim of controlling air flows. Thanks to an artificial constriction in the conduit of the flow, realised for example by means of a laminar element or a diaphragm, it is possible to obtain a pressure drop indicative of the flow rate. The differential pressure sensors measure the pressure upstream and downstream of the element. The sensor according to the invention may also be used in industrial or automobile or avionic environments: for the surveillance of filters for example by using the pressurisation principle to control the flow of air in climatic engineering. If the filter becomes blocked over time, it offers a greater resistance to the passage of the flow, and the pressure difference at the terminals of the filter increases. Differential pressure measurement sensors can measure this pressure difference and trigger alarms as soon as critical values are reached.

Claims

1. Method for manufacturing a pressure measurement sensor assembly comprising:

a) manufacturing a set of pressure measurement sensors from a first wafer (100), each pressure measurement sensor comprising at least one semi-conductor layer, such that each pressure measurement sensor comprising at least one first membrane and at least one second membrane, each first and second membrane is suspended from a support substrate, the first membrane having a face subjected to a reference pressure and a second face subjected to a first pressure to be detected, the second membrane having a first face subjected to the reference pressure and a second face subjected to a second pressure to be detected, the support substrate comprising a first through hole and a second through hole above which the first membrane and the second membrane are suspended respectively,

- a rigid beam of longitudinal axis articulated with respect to the substrate by a pivot link a round an axis said pivot link being located in a plane pa rallel to the first membrane and the second membrane which is different from the plane of the first membra ne and the second membrane, said beam being in contact via a first zone to the first membrane and via a second zone to the second membrane such that the pivot link is situated between the first zone and the second zone of the beam,

a cap delimiting with the substrate on the side of the first faces of a first and second membranes at least one hermetic cavity

b) manufacturing a set of connection substrates from a second wafer (200), in which bonding means for bonding each pressure measurement sensor to each connection substrate are made, said bonding mea ns being configured to isolate in tight manner the first membrane from the second membrane, c) Making pressure measurement assemblies by bonding the first wafer (100) and the second wafer (200), such that for each pressure measurement sensor, the first membrane and the second membrane are isolated in a tight manner from each other,

d) Separating each pressure measurement sensor assembly from each other.

2. Method according to claim 1, wherein the bonding means is eutectic bonding means, a layer of eutectic metal being formed on a first face of the second wafer (200) and, depending on the type of eutectic to realize, possibly on the face of the first (100) wafer

3. Method according to claim 1, wherein the bonding means are glue, glue being deposited on a first face of the second wafer which contacts the support substrates, the glue ensuring the sealing between the first membrane and the second membrane.

4. Method according to any of claims 1, 2 or 3, wherein the manufacturing of the connection substrates comprises the step of making the pressure ports through the second wafer (200).

5. Method according to claim 4, wherein each pressure port is made by first etching from the first face of the second wafer (200) and a second etching from a second face of the second wafer (200).

6. Method according to claim 5, wherein at least the first etchings extend in the plane of the second wafer, such that the first etchings for the pair of pressure ports of one pressure measurement sensor extend far from each other, and the second etchings are made through the second wafer such that each one of the second etchings connects a first etching of the second wafer, such that the distance between the two second etchings is greater than the distance between two membranes of one pressure measurement sensor assembly.

7. Method according to any of claims 1 to 6, wherein the distance between two second etchings of one pressure measurement sensor is about 1 mm to 5 mm.

8. Method according to any of claim 1, 2 or 3, wherein the manufacturing of the connection substrates comprises the step of making one pressure port in the connection substrate, and wherein the support substrate is structured such that a gap is created between the support substrate and the first face of the second wafer delimiting the other pressure port.

9. Method according to any of claims 1 to 8, wherein making the bonding means takes place before making a least one pressure port.

10. Method according to any of claims 1 to 9, wherein, after step d), a cover is bonded to each connection substrate.

11. A pressure measurement sensor comprising:

a support substrate (302) having a first (302.1) and a second (302.2) through holes,

a first (304) and a second (306) membranes suspended from a first side of the support substrate (302) and covering the first (302.1) and the second (302.2) through holes respectively,

a connection substrate (354) connected to a second side opposite to the first side of the support substrate (302),

a rigid beam (308) articulated with respect to the support substrate (302) by a pivot link located in a plane parallel to the first side of the support substrate (302), a cap delimiting a hermetic cavity (314) with the support substrate on the first side of the support substrate, and

a movement sensor for measuring the movement of the rigid beam

(308), wherein:

the rigid beam (308) is in contact via a first zone to the first membrane (304) and via a second zone to the second membrane (306) such that the pivot link is situated between the first zone and the second zone of the beam,

the movement sensor is arranged in the hermetic cavity (314) and at least in part on the support substrate (302),

the connection substrate (354) delimits a portion of at least one of a first (356) and a second (358) pressure ports with the support substrate (302) on the second side of the support substrate (302), and

the first (356) and the second (358) pressure ports lead to the first

(302.1) and the second (302.2) through holes of the support substrate (302) respectively.

12. A pressure measurement sensor according to claim 11, wherein the connection substrate (354) comprises a first portion (356.1) of the first pressure port - 356) passing through the connection substrate (354) itself and delimits a first portion

(356.1) of the second pressure port (356) with the support substrate (302) on the second side of the support substrate.

13. A pressure measurement sensor according to claim 12 wherein the connection substrate (354) delimits a second portion (356.2) of the first pressure port (356) with the support substrate (302) on the second side of the support substrate.

14. A pressure measurement sensor according to claim 12, wherein the connection substrate (354) comprises a second portion (358.2) of the second pressure port (358) passing through the connection substrate (354) itself.

15. A pressure measurement sensor according to claim 12, wherein the connection substrate (354) delimits a second portion (356.2) of the first pressure port (356) with the support substrate (302) on the second side of the support substrate and comprises a second portion (358.2) of the second pressure port (358) passing through the connection substrate (354) itself.

16. A pressure measurement sensor according to claim 11, wherein the connection substrate (354) delimits a first portion (356.1) of the first pressure port (356) with the support substrate (302) on the second side of the support substrate and a first portion (358.1) of the second pressure port (358) with the support substrate (302) on the second side of the support substrate.

17. A pressure measurement sensor comprising:

a support substrate (402) having a first (402.1) and a second (402.2) through holes,

a first (404) and a second (406) membranes suspended from a first side of the support substrate and covering the first (402.1) and the second (402.2) through holes respectively,

a rigid beam (408) articulated with respect to the support substrate by a pivot link located in a plane parallel to the first side of the support substrate,

a cap delimiting a hermetic cavity (414) with the support substrate (402) on the first side of the support substrate,

a movement sensor for measuring the movement of the rigid beam, and a case (474) accommodating the support substrate (402), the first and the second membranes, the rigid beam the cap and the movement sensor, wherein:

the rigid beam (408) is in contact via a first zone to the first membrane and via a second zone to the second membrane such that the pivot link is situated between the first zone and the second zone of the beam,

the movement sensor is arranged in the hermetic cavity and at least in part on the support substrate, a portion of a second side opposite to the first side of the support substrate (402) is fixed to the case with an adhesive member (476),

the adhesive member (476) delimits a portion of at least one of a first (456) and a second (458) pressure ports with the support substrate (402) on the second side of the support substrate, and

the first (456) and the second (458) pressure ports lead to the first (402.1) and the second (402.2) through holes of the support substrate (402) respectively.

18. A pressure measurement sensor according to claim 17, wherein the adhesive member (476) comprises a first portion (456.1) of a first pressure port (456) passing through the adhesive member itself (476) and delimits a first portion (458.1) of a second pressure port (458) with the support substrate (402) on the second side of the support substrate.

19. A pressure measurement sensor according to claim 18, wherein the adhesive member (476) delimits a second portion (456.2) of the first pressure port (456) with the support substrate (402) on the second side of the support substrate.

20. A pressure measurement sensor according to claim 18, wherein the adhesive member (476) comprises a second portion (458.2) of the second pressure port (458) passing through the adhesive member itself (476).

21. A pressure measurement sensor according to claim 18, wherein the adhesive member (476) delimits a second portion (456.2) of the first pressure port (456) with the support substrate (402) on the second side of the support substrate and comprises a second portion (458.2) of the second pressure port (458) passing through the adhesive member itself (476).

22. A pressure measurement sensor according to claim 17, wherein the adhesive member (476) delimits a first portion (456.1) of the first pressure port (456) with the support substrate (402) on the second side of the support substrate and a first portion (458.1) of the second pressure port (458) with the support substrate (402) on the second side of the support substrate.