Patent Description:
Pressure sensors are known. Typically, a membrane is suspended over a cavity and becomes deflected in response to pressure.

However, gas molecules outgassing from the pressure sensor itself, or gas molecules entering from outside may affect defined conditions e.g. in the cavity and impact the measurement.

<CIT> concerns the prevention, reduction, and elimination of outgassing and trapped gases in micromachined devices. One disclosed approach is to deposit a barrier layer within the device cavity and another is to use a material which, instead of, or in addition to, acting as a barrier layer, acts as a getterer, such that it reacts with and traps unwanted gases.

<CIT> concerns a capacitive pressure transducer comprising capacitor plates formed on two opposed surfaces defining a closed cavity. During formation, organics are vaporized and/or decomposed are removed through the open pores of the diaphragm and base thereof.

<CIT> concerns a pressure sensor having two diaphragms with a cavity therebetween.

According to an aspect, there is provided a sensor for measuring pressure as described by claim <NUM>.

A sensor for measuring pressure comprises a body comprising a substrate and a deformable membrane suitable for deflecting in response to pressure applied. The deformable membrane spans a cavity manufactured in the body. A first, stationary electrode is provided, and a second electrode which.

is at least coupled to or embodied in the deformable membrane. In case of pressure applied, the deformable membrane deflects and a distance between the first and the second electrode changes. Such change in distance results in a change of a capacity between the first and the second electrode which is measured and is indicative of the pressure applied. The first electrode comprises a getter material for collecting gas molecules. The getter material is exposed to the cavity.

By such solution, no additional space is required for a separate getter arrangement. Hence, the one or more electrodes comprising the getter material have a multi-fold function:.

Additionally, the integration of the getter material into the electrode is beneficial in that electrode structures are designed to be manufactured by conventional processes, such as CMOS processes, such that the manufacturing of the getter can be integrated in standard processes, such as CMOS processes.

In a preferred embodiment, the membrane separates a cavity and a port open to an outside of the pressure sensor via which port the pressure to be measured is applied. In such arrangement, it is preferred that the first, stationary electrode is arranged inside the cavity e.g. at a bottom thereof facing the deformable membrane. Under the assumption that detrimental gas molecules may enter the cavity, the getter material of the first electrode is exposed to the cavity. The cavity preferably is evacuated. In the following the getter material may keep the cavity "clean" from gas molecules for maintaining quality measurements.

The second electrode may be attached to the membrane and faces the cavity. Alternatively, the membrane may itself be electrically conducting and act as second electrode. In case of the second electrode comprising the getter material, the getter material may face the cavity.

Generally, the getter material is provided for chemically combining or ad- or absorbing gas molecules that may disturb the measurement of pressure. Such gas molecules may outgas from the pressure sensor itself, e.g. into the cavity of the pressure sensor if available. And / or gas molecules may enter the cavity from the outside, e.g. through material interfaces of the pressure sensor.

The getter material preferably is a non-evaporable metal or a non-evaporable alloy. Hence, it is preferred to use a getter material in solid form, and preferably in form of a coating. The getter material comprises or preferably consists of one of titanium, platinum, zirconium, and ZrVFe. The getter material preferably is suited to ad- or absorb or bind one or more of H, <NUM>, N2, H2O. Preferably, the getter material is not Al/Cu.

In case at least the stationary electrode comprises the getter material, space can be saved given that the electrodes are to be provided anyway. Instead, an additional getter coating may consume surface e.g. in the cavity of a pressure sensor which may lead to an increase of the overall size of the pressure sensor, which is not desired in particular when the pressure sensor is a pressure sensor integrated on a semiconductor substrate, e.g. in combination with processing circuitry.

As to the arrangement of the electrode that comprises the getter material, and as to the provision of the getter material in an electrode, multiple variants are suggested:.

In an embodiment of the second variant, the subject electrode comprises a first layer and a second layer which second layer is made from the getter material which is deposited on the first layer. The first layer comprises conducting material different to the getter material, such as Al/Cu. The second layer may fully cover a top surface of the first layer in one embodiment, and leave side faces of the first layer exposed. Alternatively, the second layer may take the shape of a cap encapsulating the first layer at its top and additionally at its side faces such that the first layer is disconnected from the volume to collect the gas molecules from. Hence, materials can be used as first layer that may not have been used in the past in view of their degrading characteristics. Here, the getter coating may additionally protect the non-getter electrode material.

In another example of the second variant not in accordance with the appended claims, the subject electrode comprises a center portion and a ring portion around the center portion, all in the same plane. The ring portion is disconnected from the center portion by means of a gap, whereas outside the gap there may be an electrical connection between the center portion and the ring portion, This variant utilizes space best, e.g. in a cavity.

Both the above embodiment and the above example can be applied simultaneously, not in accordance with the appended claims, i.e. the center portion and / or the ring portion may comprise the first and the second layer. In another example not in accordance with the appended claims, both the center and the ring portion consist of getter material. In examples not in accordance with the appended claims where both the center and the ring portion comprise getter material, a different getter material may be applied to the ring portion than to the center portion. In a different example, not in accordance with the appended claims, only one of the center portion and the ring portion consists of the getter material while the other portion consists of the conducting non-getter material, such as Al-Cu.

In case of any combinations of getter and non-getter material, the getter material is exposed to the volume to collect gas molecules from, e.g. the getter material faces the cavity.

In a preferred embodiment of the present invention, slots are provided in the getter material of the subject electrode. The slots may e.g. have a width of less than <NUM>, and preferably between <NUM> and <NUM>. Provided that the electrode has a plane extension the slots are directed vertical through the getter material, i.e. orthogonal to the plane extension of the electrode. In the case of a layered electrode, it is preferred that the slots reach into, and preferably through the first layer underneath the second layer of getter material. The slots serve as stress reducing means given that stress may be induced from thermal manufacturing processes of the sensor as such, from the deposition of the subject electrode itself, or from the deposition of individual layers of the subject electrode if any. The material of the electrode may now expand into the slots in response to thermal impact without converting into significant stress. In addition, in particular in the two layer embodiment of the subject electrode, delamination effects of the two layers may be reduced by means of the slots.

In the case of a two portion electrode, slots may be applied to any getter material irrespective in which portion the getter material is arranged. Preferably, in case one of the portions consisting only of a conducting material different to the getter material, this portion is not provided with slots.

In a different preferred embodiment of the present invention, the subject electrode may comprise multiple individual elements of the getter material, e.g. in the form of posts or pillars. Such individual elements may be arranged next to each other in a plane. Hence, the individual elements are disconnected from each other, e.g. by grooves. In case of a layered set-up of the elements, each individual element may comprise the first layer of conducting non-getter material and the second layer of the getter material deposited on the first layer. The grooves reach through both the first and the second layer.

As with the slots, the provision of the individual elements separated from each other by the grooves reduces stress and delamination. The material of the individual elements may now expand into the grooves in response to thermal impact without generating significant stress.

According to the invention to which this European patent relates, the individual elements are disconnected from each other except for electrically conducting bridges between two neighboring individual elements. In a different embodiment, the connection may be made within the CMOS layer stack "underneath" the posts in case the individual elements are arranged on top of a CMOS layer stack. It is preferred that each individual element is electrically connected to at least one of the neighboring individual elements, in order to contact the multitude of individual elements forming the electrode by only one contact. In another variant, an individual element may be connected to all of its neighboring elements.

In a preferred embodiment of the pressure sensor, a cavity of the pressure sensor preferably is formed in a cap which cap preferably is attached to a first substrate such that the deformable membrane faces the first substrate and such that a gap is provided between the deformable membrane and the first substrate. The cap may further contain a processing circuit. A deformation of the deformable membrane is capacitively measured and converted into a signal that is supplied to and processed by the processing circuit in the cap. The first substrate contains a support portion to which the cap is attached. A contact portion of the first substrate is provided for electrically connecting the pressure sensor to the outside world. The support portion is suspended from the contact portion by one or more suspension elements, in this arrangement, the deformable membrane as element sensitive to stress in essence is mechanically decoupled from the contact portion of the first substrate via which stress may be induced from an external carrier, or during mounting of the pressure sensor to an external carrier given that the contact portion preferably is the only portion via which the pressure sensor is electrically and mechanically connected to the external carrier. Not only is the deformable membrane no longer attached to the first substrate and is integrated into the cap instead. Moreover, already a first substrate portion, i.e. the support portion is mechanically decoupled from the contact portion. On the other hand, the cap is attached, and preferably is solely attached to the support portion of the first substrate but not to the contact portion such that the membrane has no direct mechanical link to the contact portion of the first substrate. Hence, any propagation of stress induced via the contact portion of the first substrate towards the membrane is significantly reduced. The cap is at least partly manufactured from a second substrate. Preferably, the second substrate is a semiconductor substrate, such as a silicon substrate. Hence, the second substrate may, for example, contain a bulk material made from silicon and various layers stacked on the bulk material such as one or more of metal layers, insulation layers and passivation layers. It is preferred, that the processing circuit is integrated into the second substrate. And it is preferred that the cavity is formed solely in the layer stack of the second substrate and does not reach into the bulk material. In a preferred embodiment, the deformable membrane is built from a third substrate, which is attached to the top layer of the second substrate. The third substrate may, for example, be an SOI (Silicon On Insulator) substrate, wherein specifically the deformable membrane may be built from a silicon layer of the SOI substrate while an insulation layer and bulk material of the SOI substrate are removed during processing. In the first substrate, the contact and the support portion are preferably built by applying one or more grooves vertically through the first substrate. By way of manufacturing the one or more grooves, one or more small portions of the first substrate remain for mechanically linking the support portion to the contact portion. This / these small portion/s act as suspension element/s for suspending the support portion from the contact portion. Preferably, the one or more grooves are arranged vertically in the first substrate, i.e. orthogonal to a plane extension of the first substrate. The suspension element/s may contain ridges, e.g. four ridges that hold the support portion. Preferably, each suspension element is formed integrally with the support portion and the contact portion given that the support portion, the contact portion and the one or more suspension elements are built from the first substrate. The suspension elements do not represent the shortest path between the contact portion and the support portion but do have a shape that allows one or more of a deflection or a rotation of the support portion relative to the contact portion, e.g. a deflection in at least one direction of the plane of the first substrate. In such way, translational and / or rotational forces applied to the support portion via the cap may be dampened. The suspension elements may contain spring portions for this purpose. Preferably, the deformable membrane itself serves as second electrode and as such contains electrically conducting material. The second electrode may be a metal layer, or may be a polysilicon layer. On the other hand, the first electrode which contains the getter material may be arranged near or in the cavity at a stationary position such that this electrode arrangement may allow sensing a capacitance between the first electrode and the deflectable membrane which capacitance is dependent on the distance between the electrodes. For electrically connecting the cap to the first substrate, electrical connections may be provided between the cap and the first substrate, e.g. in form of solder bumps or balls, or other electrically conducting elements that at the same time may also serve as spacer elements for providing the gap between the first substrate and the deformable membrane. In order to connect to the electrically conducting layers in the second substrate, contact windows may be provided into the second substrate and if applicable through the third substrate. On the other hand, the spacer elements may connect to contact pads on the first substrate which may be areas of conducting layers revealed from the first substrate.

Embodiments of the present invention, aspects and advantages will become apparent from the following detailed description thereof. Such description makes reference to the annexed drawings, wherein the figures show:.

The term "pressure sensor" as used herein designates any type of sensor measuring a parameter that is equal to or derived from the pressure of a fluid, which fluid shall include a gas and a liquid. In particular, the term designates relative (i.e. differential) as well as absolute pressure sensors, it also covers static as well as dynamic pressure sensors. Typical examples of applications of such sensors are e.g. in scientific instrumentation, meteorology, altitude measurement, sound recording, mobile or portable computers and phones etc..

<FIG> illustrates a pressure sensor in a schematic sectional view according to the present invention to which this European patent relates. The pressure sensor preferably is an integrated pressure sensor, i.e. embodied by means of a substrate, and preferably by a semiconductor substrate such as a silicon substrate, preferably together with a processing circuit (not shown) for at least preprocessing a pressure signal. The pressure sensor comprises a body, which contains a substrate <NUM>, and a deformable membrane <NUM> spanning a cavity <NUM> manufactured in the body. The deformable membrane <NUM> deflects in response to pressure applied to it, such as pressure of the surrounding air, which deflection is in z-direction orthogonal to a plane extension of the pressure sensor in x- / y- direction. The deflection of the membrane <NUM> is determined by a capacitive measurement. For this purpose, a first electrode <NUM> is arranged inside the cavity <NUM>, e.g. at a bottom of the cavity <NUM>, while a second electrode <NUM> is arranged at or embodied in the membrane <NUM>. A change of a distance d between the first and the second electrode <NUM> and <NUM> results in a change in the capacitance between the two electrodes <NUM> and <NUM> which is measured by the electrodes <NUM> and <NUM>. A corresponding signal preferably is supplied to a processing circuit, e.g. integrated together with the sensor in the same chip. Preferably, the cavity <NUM> is evacuated, such that the pressure sensor is adapted to measure an absolute pressure. In the present invention to which this European patent relates, the first, stationary electrode <NUM> comprises the getter material.

<FIG> each shows a cutout of a pressure sensor according to an embodiment of the present invention in a sectional view, e.g. a cutout of the first electrode <NUM> of the pressure sensor of <FIG>. In the pressure sensor of each of the <FIG>, it is assumed that the first electrode <NUM> is arranged on a stack of material layers, e.g. CMOS layers, which at least include an insulating layer <NUM> arranged on a semiconductor bulk material <NUM>, and a passivation layer <NUM> arranged on the insulating layer <NUM>. Preferably, the insulating layer <NUM> is a SiO2 layer, while the passivation layer <NUM> is a SiNx layer. The first electrode <NUM> is arranged on the passivation layer <NUM>. The layer stack - which may contain additional insulating and metal layers - and the bulk material <NUM> preferably contribute to the body of the pressure sensor.

In the embodiment of <FIG>, the first electrode <NUM> is solely made from a getter material, e.g. from titanium. The getter material may instead be - and without being limited to the present embodiment - e.g. platinum, or zirconium. In the present embodiment, the getter material is deposited straight on the passivation layer <NUM>.

In the embodiment of <FIG>, the first electrode <NUM> is layered. Presently, it contains a first layer <NUM> and a second layer <NUM>. The second layer <NUM> is made from the getter material. The first layer <NUM> is made from an electrode material, e.g. from a metal or an alloy different to the getter material, and specifically from aluminum; and preferably from aluminum containing a small amount of copper, i.e. the metal composition of a conducting layer of the material stack in the CMOS process. In the present embodiment, the first layer <NUM> is deposited straight on the passivation layer <NUM>, and the getter material is deposited on the first layer <NUM>.

The embodiment of <FIG> differs from the one of <FIG> in that the second layer <NUM> of getter material is formed as a cap separating the first layer <NUM> from the cavity. In this example, the first layer <NUM> is not exposed at all to any molecules to be caught by the getter material, and therefore is fully protected from corrosion.

<FIG> each show a top view on an electrode of a pressure sensor, not forming part of the present invention to which this European patent relates. For example, the electrode may be the first electrode <NUM>, <NUM> and arranged as stationary electrode in the cavity of a pressure sensor, and specifically arranged at the bottom of such cavity. In the present example, the first electrode <NUM> is of circular shape.

In the example of <FIG>, the getter material <NUM> or <NUM> is applied continuous within the circumference of the first electrode <NUM>.

In the example of <FIG>, slots <NUM> are provided in the getter material <NUM>. A hard mask may be provided representing the slots in form of ridges which hard mask may be arranged on the passivation layer, or more generally, on the place to build the getter electrode at. The non-getter material if any, and the getter material may be coated or vapor deposited between the ridges of the hard mask. In a different example, the non-getter material if any, and the getter material <NUM>, <NUM> may be deposited as a continuous layer, and slots <NUM> may be applied afterwards, e.g. by etching or other processing means.

<FIG> is a cut along line A-A' of the first electrode <NUM> of <FIG>. In the present example, the first electrode <NUM> comprises two layers <NUM> and <NUM>, e.g. an Al/cu layer <NUM>, and the getter layer <NUM>, e.g. made from titanium. As can be seen from <FIG>, the slots <NUM> fully reach through both layers <NUM> and <NUM>.

According to the invention to which this European patent relates in <FIG>, the first electrode <NUM> is made from individual elements <NUM> represented by small squares each. The elements <NUM> are electrically connected with each other. Each element <NUM> at least is electrically connected to one other element <NUM> in order to ensure the electrical connectivity of the overall first electrode <NUM>. An element <NUM> is electrically connected via an electrically conducting bridge to at least one of the neighboring elements <NUM>, and preferably to all of the neighboring elements <NUM> as is shown in <FIG> which is a zoom-in of area C of <FIG> in top view. Nine elements <NUM> are zoomed wherein each of these elements <NUM> is connected to each of the neighboring elements <NUM> by means of V-shaped bridges <NUM> which in addition act as springs. <FIG> shows the zoom-in of area C of <FIG> according to a second embodiment of the present invention. Here, the individual elements <NUM> are connected with each other via bridges <NUM> that are shaped different than the bridges of <FIG>. Again, the bridges <NUM> also act as springs.

<FIG> is a cut along line B-B' of <FIG>. In the present example, the electrode <NUM> comprises two layers <NUM> and <NUM>, e.g. an Al/Cu layer <NUM>, and the getter layer <NUM>, e.g. made from titanium. As can be seen from <FIG>, the individual elements <NUM> are separated from each other except for the electrically conducting bridges <NUM>. The bridges <NUM> serve for electrically connecting all individual elements <NUM>, such that the entire electrode <NUM> requires only a single electrical contact.

As to the manufacturing of the individual elements <NUM>, in a first embodiment a hard mask may be provided in form of a grid which hard mask may be arranged on the passivation layer, or more generally, on the place to build the getter electrode at. The non-getter material if any, and getter material may be coated or vapor deposited into the openings of the grid. In a different embodiment, the non-getter material if any, and the getter material <NUM> may be deposited both as a continuous layer, and may be separated into individual elements <NUM> afterwards, e.g. by etching or other processing means.

<FIG> shows a schematic sectional view of a pressure sensor in accordance with an embodiment of the present invention. The pressure sensor as shown is flipped with its solder balls <NUM> showing upwards while the pressure sensor will be mounted to a carrier with its solder balls <NUM> sitting on the carrier. The pressure sensor includes a first substrate <NUM> and a cap <NUM> for the first substrate <NUM>. The cap <NUM> preferably is made from a second substrate <NUM> and a third substrate <NUM>. The second substrate <NUM> preferably is a semiconductor substrate, preferably a silicon substrate, and has a front side <NUM> and a backside <NUM>. The second substrate <NUM> contains a bulk material <NUM> of, e.g. silicon and a stack of layers <NUM> on the bulk material <NUM>. These layers <NUM> may be arranged for CMOS processing of the second substrate <NUM>, and as such may also be denoted as CMOS layers or material layers. Specifically, the layers <NUM> can include for example a plurality of SiO2 layers, metal or polysilicon layers.

The bulk material <NUM> may contain doped regions within the silicon such as indicated by the reference sign <NUM>. These components can form active circuitry, such as amplifiers, A/D converters or other analog and/or digital signal processing units. A top layer <NUM> of the stack of layers <NUM> may be a dielectric layer of silicon oxide and/or silicon nitride protecting the structures below it. In the present example, it is assumed that a processing circuit collectively referred to as <NUM> is integrated on the front side <NUM> of the second substrate <NUM> by means of CMOS. processing.

In the cap <NUM>, a cavity <NUM> is formed by omitting or removing material from one or more of the layers <NUM>, presently the top layer <NUM>. The cavity <NUM> is closed by a deformable membrane <NUM>. The membrane <NUM> is sufficiently thin such that it deforms depending on a pressure drop between a pressure at the top of the membrane <NUM> and below it. A metal layer of the layer stack <NUM> may be used as a first stationary electrode <NUM>, and as such may be arranged at the bottom of the cavity <NUM>. The first stationary electrode <NUM> is entirely made from a getter material in this example.

The membrane <NUM> preferably is formed by a doped, conducting silicon layer, is arranged as a sealing lid over the cavity <NUM>, and may be used as a second electrode <NUM> for which reason the deformable membrane <NUM> may contain electrically conducting material. Hence upon a change in pressure the membrane <NUM> deflects and as such a distance between the two electrodes <NUM> and <NUM> changes which results in a change of the capacitance between the two electrodes <NUM> and <NUM>.

In the present example, the deformable membrane <NUM> is built from a third substrate <NUM>. The third substrate <NUM> as shown in <FIG> may be the remainder of an SOI substrate, specifically its device layer after some manufacturing steps. The third substrate <NUM> not only may contribute to the deformable membrane <NUM>. The third substrate <NUM> may contain contact windows <NUM> reaching through which may also reach into one or more of the layers <NUM>.

Corresponding signals may be transmitted from the electrodes <NUM> and <NUM> via electrical paths <NUM> to the processing circuit <NUM> where these signals are processed. Signals processed by the processing circuit <NUM> may be supplied to the first substrate <NUM>.

The first substrate <NUM> may be a semiconductor substrate, e.g. a silicon substrate, or a glass substrate, for example, with a front side <NUM> and a back side <NUM>. The semiconductor substrate <NUM> includes bulk material <NUM> such as silicon, and one or more layers <NUM>, such as an oxide layer on the bulk material <NUM>. The one or more layers <NUM> may further include for example a plurality of SiO2 layers, metal or polysilicon layers.

The first substrate <NUM> contains vias <NUM> reaching vertically through the first substrate <NUM>. Those vias <NUM> provide for an electrical connection from the front side <NUM> of the substrate <NUM> to its backside <NUM>. Those vias <NUM> are manufactured by etching or drilling holes into the first substrate <NUM> from its backside <NUM>, by applying an oxide <NUM> to the hole, and by applying conducting material <NUM> to the oxide <NUM>. At the back side <NUM> of the first substrate <NUM>, the vias <NUM> are electrically connected to contact pads <NUM> residing on an oxide layer <NUM> applied to the bulk material <NUM>, which contact pads <NUM> serve as support for solder balls <NUM> or other contact means for electrically connecting the pressure sensor to the outside world, i.e. to another device. Alternative to the vias <NUM> and the solder balls <NUM>, there may be other ways of interconnecting the pressure sensorto the outside world, e.g. by means of wire bonds, bond pads or conducting structures that lead from the front side <NUM> of the first substrate <NUM> along its sides to the backside <NUM>. The electrical connection to the outside world may also be implemented via one or more of a Land Grid Array, a Pin Grid Array, or a leadframe.

The assembly containing the second and the third substrate <NUM>, <NUM> is attached to the front side <NUM> of the first substrate <NUM>. The attachment may include bonding or other fusion techniques. In the present example, spacer elements <NUM> are provided between the third substrate <NUM> and the first substrate <NUM>. The spacer elements <NUM> may have different functions: On the one hand, the spacer elements <NUM> provide for a gap <NUM> between the deformable membrane <NUM> and the first substrate <NUM> which is required for supplying the pressure medium to the membrane <NUM>. On the other hand, some of the spacer elements <NUM>, but not necessarily all may be electrically conductive for connecting the contact windows <NUM> to the first substrate <NUM>. other or the same spacer elements <NUM> may provide mechanical stability for the stacking of substrates <NUM>, <NUM>, and / or may provide mechanical protection to the inside of the pressure sensor, and specifically to the membrane <NUM>. For this purpose, it may be preferred, that a spacer element <NUM> is arranged in from of a ring at the edges of the substrates <NUM>,<NUM> providing mechanical stability, protection as well as an electrical connection, while spacer elements <NUM> are rather pillar-like and provide electrical connections.

The signals provided by the processing circuit <NUM> hence may be transferred via one or more of the electrical paths <NUM> and via one or more of the contact windows <NUM> to one or more of the spacer elements <NUM>. As shown in <FIG>, the spacer elements <NUM> end at the vias <NUM> of the first substrate <NUM> and are electrically connected thereto. Hence, the signals are conducted through the vias <NUM> to the contact pads <NUM> and the solder balls <NUM>.

The first substrate <NUM> contains a support portion <NUM> and a contact portion <NUM>. Suspension elements not shown in the present illustration are provided for suspending the support portion <NUM> from the contact portion <NUM>. The support portion <NUM> preferably encircles the contact portion <NUM> in a plane of the first substrate <NUM>.

The contact portion <NUM> is separated from the support portion <NUM> by one or more grooves <NUM>. Owed to the manufacturing. of the contact portion <NUM> and the support portion <NUM> from the common first substrate <NUM>, both portions may include bulk material <NUM> from the first substrate <NUM>.

The cap <NUM> preferably is exclusively attached to the support portion <NUM> of the first substrate <NUM> via the spacer elements <NUM>. On the other hand, it is preferred that it is solely the contact portion that provides a mechanical and electrical contact to the outside world. Hence, the portion of the pressure sensor via which mechanical stress is induced, i.e. the contact portion <NUM> is mechanically decoupled from the rest of the pressure sensor and specifically from the deformable membrane <NUM> by way of the suspension elements.

A port for conducting a medium to the deformable membrane <NUM> in the present example encompasses the grooves <NUM> and the gap <NUM>, or at least parts of.

The overall height of the pressure sensor in the present example is about <NUM>.

<FIG> illustrates a bottom view onto the first substrate <NUM> of the pressure sensor of <FIG>. The first substrate <NUM> contains a support portion <NUM> and a contact portion θ wherein the support portion <NUM> is suspended from the contact portion θ by means of a suspension element <NUM>, which is a representation of a mechanical link between the two portions <NUM> and <NUM>. A groove <NUM> is arranged vertically through the first substrate <NUM>. Vias <NUM> are arranged in the support portion <NUM>, while the solder balls <NUM> are arranged in the contact. portion <NUM>. The contact portion <NUM> is electrically connected to the support portion <NUM> by means of electrically conducting structures such as the contact pads <NUM> which electrically conducting structures may in generally be denoted as redistribution layer.

<FIG> each shows a pressure sensor according to an example not forming part of the present invention to which this European patent relates, in diagram b) in a cross section, and in diagram b) in a top view on the corresponding first electrode <NUM>. For the present examples, it is assumed that the pressure sensor may contain a structural set-up identical or similar to those shown in <FIG> or <FIG>. Hence, a cavity <NUM> is formed by means of a membrane <NUM> facing a substrate containing silicon as bulk material <NUM> and a stack of layers on top of the bulk material <NUM>. In a top most layer <NUM>, which presently may be an oxide layer such as a SiO2 layer, a recess is built for forming the cavity <NUM>. The top most layer <NUM> may be arranged on a passivation layer <NUM>, such as a SiNx layer which in turn is arranged on an oxide layer <NUM>. Other layers, such as further CMOS layers may be present in the stack of layers. In all the present examples, a first electrode <NUM> is arranged at a bottom of the cavity <NUM>, while a second electrode not further shown may be integrated, arranged on or otherwise coupled to the deflectable membrane <NUM>. Contact windows <NUM> are arranged in the top most layer <NUM> and the anchorage of the membrane <NUM>.

In <FIG>, the first electrode <NUM> comprises a center portion <NUM> including a stack of a first layer <NUM> of electrically conducting material, specifically a non-getter material, such as Al-Cu, which may be made from a metal layer of the CMOS layer stack and of a second layer <NUM> arranged on top of the first layer <NUM> and covering a top surface of the first layer <NUM> entirely. The second layer <NUM> is a continuous film as can be derived from diagram 14a). Outside the layered center portion <NUM> and separated by a gap, the first electrode <NUM> further comprises a ring portion <NUM> of getter material which is directly applied to the passivation layer <NUM> or another layer of the stack of layers. This ring portion <NUM> lacks the first layer material <NUM> underneath. By such means, the surface of the getter material can be enhanced, thereby improving the capacitance of catching gas molecules. As can be derived from diagram 14a), an electrical contact <NUM> is provided for contacting the ring portion <NUM> which ring portion <NUM> on the other hand is electrically connected to the layered portion <NUM> (not shown). Such connection may be e.g. implemented by means of a metal layer in the stack of layers underneath the ring portion and the layered portion. Hence, the first electrode <NUM> comprising the getter material is split into a central portion <NUM> and a ring portion around <NUM> the center portion, wherein the center portion <NUM> is a layered while the ring portion <NUM> is non-layered. Preferably, the first electrode <NUM> is arranged centered in the cavity <NUM>, and preferably at the bottom of the cavity <NUM>.

The first electrode <NUM> in <FIG> solely comprises the centered, layered portion <NUM> of the first electrode <NUM> of <FIG>. Hence, a stack is provided comprising a first layer <NUM> of electrically conducting non-getter material, such as Al-Cu, and a second layer <NUM> comprising the getter material arranged on top of the first layer <NUM> and covering a top surface of the first layer <NUM> entirely. Again, the second layer <NUM> is a continuous film as can be derived from diagram 15a).

The first electrode <NUM> in <FIG> solely comprises getter material in the ring portion <NUM> of the first electrode <NUM> of <FIG>. Instead, the center portion <NUM> is not layered, and only the first layer <NUM> containing non-getter material is provided in the center portion <NUM>. Again, it is assumed that the electrical contact <NUM> reaches via the ring portion <NUM> to the first layer <NUM> which is not shown in the top view of diagram 16a) which diagrams a) only indicate any getter material in top view.

The first electrodes <NUM> in <FIG> comprise slotted getter material portions. The first electrode <NUM> of <FIG> resembles the first electrode <NUM> of <FIG> and as such comprises a layered center portion <NUM> and a ring portion <NUM> around the center portion <NUM>. However, both the layered center portion <NUM> and the ring portion <NUM> comprise slots <NUM> in the getter material as introduced in connection with the example of <FIG>. In the ring portion <NUM> as well as in the center portion <NUM>, the slots <NUM> reach through the getter material and through the first layer <NUM>. In a different example, the slots <NUM> reach only through the getter material but not through the first layer <NUM>.

The first electrode <NUM> in <FIG> solely comprises the layered center portion <NUM> of the first electrode <NUM> of <FIG>. Hence, a stack of a first layer <NUM> of electrically conducting non-getter material, such as Al-Cu, and of a second layer <NUM> comprising the getter material is manufactured. Again, the second layer <NUM> is slotted, and the first layer <NUM> preferably is slotted, too.

The first electrode <NUM> in <FIG> solely comprises getter material in the ring portion <NUM> of the first electrode <NUM> of <FIG>. The center portion <NUM> is not layered and only comprises the first layer <NUM> containing non-getter material. Again, it is assumed that the electrical contact <NUM> reaches via the ring portion <NUM> to the first layer <NUM>. The ring portion <NUM> comprises slots <NUM>.

The first electrode <NUM> in <FIG> resembles the first electrode <NUM> of <FIG>. However, the second layer <NUM> of the center portion <NUM> additionally covers the sides of the first layer <NUM> and hence forms a cap for the first layer <NUM> such that the first layer <NUM> is not exposed to gaseous components.

The first electrode <NUM> in <FIG> resembles the first electrode <NUM> of <FIG>. Again, no ring portion is provided, but the center portion is layered comprising the getter material containing second layer <NUM> continuously deposited on the first layer <NUM>. However, as in the example of <FIG>, the second layer <NUM> additionally covers the sides of the first layer <NUM> and hence forms a cap for the first layer <NUM> such that the first layer <NUM> is not exposed to gaseous components.

Claim 1:
A sensor for measuring pressure, the sensor comprising:
a body comprising:
a substrate (<NUM>), and
a deformable membrane (<NUM>) for deflecting in response to pressure applied,
wherein the deformable membrane (<NUM>) spans a cavity (<NUM>) manufactured in the body;
a first stationary electrode (<NUM>) and a second electrode (<NUM>) for determining a change in a capacitance between the first and the second electrode (<NUM>, <NUM>) in response to the pressure applied,
wherein the second electrode is coupled to or embodied in the deformable membrane (<NUM>);
wherein the first electrode (<NUM>, <NUM>) comprises a getter material for collecting gas molecules,
wherein the getter material is exposed to the cavity,
characterized in that:
the first electrode comprises a plurality of individual elements, wherein neighbouring elements of the plurality of individual elements are coupled to one another through an electrically conducting bridge, and
wherein the electrically conducting bridge is configured to act as a spring.