Abstract: A method for producing a semiconductor includes providing a p-doped semiconductor body having a first side and a second side; implanting protons into the semiconductor body via the first side to a target depth of the semiconductor body; bonding the first side of the semiconductor body to a carrier substrate; forming an n-doped zone in the semiconductor body by heating the semiconductor body such that a pn junction arises in the semiconductor body; and removing the second side of the semiconductor body at least as far as a space charge zone spanned at the pn junction.

Abstract: A method of constructing devices using semiconductor manufacturing processes includes fabricating a device having a movable portion and a fixed portion. The movable portion is connected to the fixed portion only through at least one sacrificial layer. The sacrificial layer is removed in the presence of a force of sufficient strength so as to controllably reposition the movable portion during the release process. The force can be externally applied, generated locally as a result of, for example, the relative positions of the fixed and movable portions, or some combination of the two. Several devices constructed according to such a method are also disclosed.

Abstract: The present disclosure relates a method to mitigate wafer warpage in advanced technology manufacturing processes due to crystallization of one or more amorphous layers with asymmetrical front-surface and back-surface layer thicknesses. After deposition of one or more layers of amorphous material on a front-surface and a back-surface of the wafer in a furnace tool, the front-surface layers are patterned which thins a front layer thickness. Downstream thermal processing performed at a temperature which exceeds a crystallization threshold of the amorphous material will result in asymmetric stress between the front and back surfaces due to the asymmetrical layer thicknesses. To mitigate this effect, the amount of warpage as a function of the difference in asymmetrical layer thickness may be determined such that a front-surface deposition tool may be utilized in conjunction with the furnace tool to reduce the difference in front-surface and back-surface layer thicknesses. Other methods are also disclosed.

Abstract: Disclosed herein an inertial sensor and a method of manufacturing the same. An inertial sensor 100 according to a preferred embodiment of the present invention is configured to include a plate-shaped membrane 110, a mass body 120 that includes an adhesive part 123 disposed under a central portion 113 of the membrane 110 and provided at the central portion thereof and a patterning part 125 provided at an outer side of the adhesive part 123 and patterned to vertically penetrate therethrough, and a first adhesive layer 130 that is formed between the membrane 110 and the adhesive part 123 and is provided at an inner side of the patterning part 125. An area of the first adhesive layer 130 is narrow by isotropic etching using the patterning part 125 as a mask, thereby making it possible to improve sensitivity of the inertial sensor 100.

Abstract: The present invention relates to a CMOS compatible MEMS microphone, comprising: an SOI substrate, wherein a CMOS circuitry is accommodated on its silicon device layer; a microphone diaphragm formed with a part of the silicon device layer, wherein the microphone diaphragm is doped to become conductive; a microphone backplate including CMOS passivation layers with a metal layer sandwiched and a plurality of through holes, provided above the silicon device layer, wherein the plurality of through holes are formed in the portions thereof opposite to the microphone diaphragm, and the metal layer forms an electrode plate of the backplate; a plurality of dimples protruding from the lower surface of the microphone backplate opposite to the diaphragm; and an air gap, provided between the diaphragm and the microphone backplate, wherein a spacer forming a boundary of the air gap is provided outside of the diaphragm or on the edge of the diaphragm; wherein a back hole is formed to be open in substrate underneath the diaph

Abstract: A simple and cost-effective manufacturing method for hybrid integrated components including at least one MEMS element, a cap for the micromechanical structure of the MEMS element, and at least one ASIC substrate, using which a high degree of miniaturization may be achieved. The micromechanical structure of the MEMS element and the cap are manufactured in a layered structure, proceeding from a shared semiconductor substrate, by applying at least one cap layer to a first surface of the semiconductor substrate, and by processing and structuring the semiconductor substrate proceeding from its other second surface, to produce and expose the micromechanical MEMS structure. The semiconductor substrate is then mounted with the MEMS-structured second surface on the ASIC substrate.

Abstract: A method for manufacturing an ultrasonic transducer includes: forming a piezoelectric element by laminating a lower electrode, a piezoelectric body, and an upper electrode on a first face of a support film; affixing a reinforcing substrate that covers the piezoelectric element to the first face of the support film; forming a photosensitive resin substrate to a second face of the support film that is on an opposite side from the first face; forming an opening in the resin substrate by irradiating the resin substrate with light; and removing the reinforcing substrate.

Abstract: Embodiments of mechanisms for forming a micro-electro mechanical system (MEMS) device are provided. The MEMS device includes a substrate and a MEMS structure over the substrate, and the MEMS structure has a movable element. The movable element is surrounded by a cavity. The MEMS device also includes a fuse layer on the movable element, and the fuse layer has a wide portion and a narrow portion linked to the wide portion.

Abstract: A MEMS device includes a membrane comprising a first plurality of fingers. A counter electrode arrangement includes a second plurality of fingers disposed in a interdigitated relationship with the first plurality of fingers of the membrane. A deflector is configured to deflect the membrane such that the first and second plurality of fingers are displaced in a position excluding maximum overlapping of surfaces of the fingers.

Abstract: An rf MEMS system has a semiconductor substrate, e.g., silicon. The system also has a control module provided overlying one or more first regions of the semiconductor substrate according to a specific embodiment. The system also has a base band module provided overlying one or more second regions of the semiconductor substrate and an rf module provided overlying one or more third regions of the semiconductor substrate. The system also has one or more MEMS devices integrally coupled to at least the rf module.

Abstract: A microphone structure of an MEMS device has a layer construction including: a base substrate; a deflectable microphone diaphragm at least partly spanning a through-opening in the substrate; a deflectable electrode of a microphone condenser system; a stationary counter-element having ventilation openings situated in the layer construction over the microphone diaphragm and acting as a bearer for a stationary electrode of the microphone condenser system. The diaphragm is bonded into the layer construction on the substrate via a flexible beam. The otherwise free edge region of the diaphragm is curved in a pan shape, so that it extends both vertically and also in some regions laterally beyond the edge region of the through-opening, and the edge region of the through-opening forms a lower stop for the diaphragm movement.

Abstract: A micromechanical component includes a substrate having a cavern structured into the same, an at least partially conductive diaphragm, which at least partially spans the cavern, and a counter electrode, which is situated on an outer side of the diaphragm oriented away from the substrate so that a clearance is present between the counter electrode and the at least partially conductive diaphragm, the at least partially conductive diaphragm being spanned onto or over at least one electrically insulating material which at least partially covers the functional top side of the substrate, and at least one pressure access being formed on the cavern so that the at least partially conductive diaphragm is bendable into the clearance when a gaseous medium flows from an outer surroundings of the micromechanical component into the cavern. Also described is a manufacturing method for a micromechanical component.

Abstract: A structure having a plurality of conductive regions insulated electrically from each other comprises a movable piece supported movably above the upper face of the conductive region, the movable piece having an electrode in opposition to the conductive region, the structure being constructed to be capable of emitting and receiving electric signals through the lower face of the conductive region, the plural conductive regions being insulated by sequentially connected oxidized regions formed from an oxide of a material having through-holes or grooves.

Abstract: A MEMS device wherein a die of semiconductor material has a first face and a second face. A membrane is formed in or on the die and faces the first surface. A cap is fixed to the first face of the first die and is spaced apart from the membrane by a space. The die is fixed, on its second face, to an ASIC, which integrates a circuit for processing the signals generated by the die. The ASIC is in turn fixed on a support. A packaging region coats the die, the cap, and the ASIC and seals them from the outside environment. A fluidic path is formed through the support, the ASIC, and the first die, and connects the membrane and the first face of the die with the outside, without requiring holes in the cap.

Abstract: For simplifying the manufacture of a MEMS structural component including a deflectable diaphragm which spans an opening in the rear side of the structural component, and including a fixed counter-element, which is provided with passage openings, the counter-element from the base substrate of the MEMS structural component is patterned and the deflectable diaphragm is implemented in a layered structure on the base substrate. These measures are intended to improve the diaphragm properties and reduce the overall height of the MEMS structural component.

Abstract: A MEMS microphone includes a first diaphragm element, a counter electrode element, and a low pressure region between the first diaphragm element and the counter electrode element. The low pressure region has a pressure less than an ambient pressure.

Abstract: A MEMS microphone. The MEMS microphone includes a back plate, a membrane, a support structure, a substrate, and an overtravel stop. The membrane is coupled to the back plate. The support structure includes a support structure opening and a first side of the support structure is coupled to a second side of the back plate. The substrate includes a substrate opening and a first side of the substrate is coupled to a second side of the support structure. The overtravel stop limits a movement of the membrane away from the back plate and includes at least one of an overtravel stop structure coupled to the substrate, an overtravel stop structure formed as part of a carrier chip, and an overtravel stop structure formed as part of the support structure in the support structure opening.

Abstract: Methods for fabricating crack resistant Microelectromechanical (MEMS) devices are provided, as are MEMS devices produced pursuant to such methods. In one embodiment, the method includes forming a sacrificial body over a substrate, producing a multi-layer membrane structure on the substrate, and removing at least a portion of the sacrificial body to form an inner cavity within the multi-layer membrane structure. The multi-layer membrane structure is produced by first forming a base membrane layer over and around the sacrificial body such that the base membrane layer has a non-planar upper surface. A predetermined thickness of the base membrane layer is then removed to impart the base membrane layer with a planar upper surface. A cap membrane layer is formed over the planar upper surface of the base membrane layer. The cap membrane layer is composed of a material having a substantially parallel grain orientation.

Abstract: The invention discloses a capacitive pressure sensor and a method of fabricating the same. The capacitive pressure sensor includes a fixed plate configured as a back plate, a movable plate configured as diaphragm for sensing pressure, wherein a cavity is formed between the fixed plate and the movable plate, an isolation layer between the fixed plate and the movable plate and electrical contacts thereof for minimizing the leakage current, plurality of damping holes for configuring the contour of the fixed plate as the deflected diaphragm when pressure is exerted, a vent hole extending to the cavity having resistive air path for providing equilibrium to the diaphragm and an extended back chamber for increasing the sensitivity of the capacitive pressure sensor. The capacitive pressure sensor is also configured for minimizing parasitic capacitance.

Abstract: An integrated circuit device includes a first layer comprising at least two partial cavities, an intermediate layer bonded to the first layer, the intermediate layer formed to support at least two Micro-electromechanical System (MEMS) devices, and a second layer bonded to the intermediate layer, the second layer comprising at least two partial cavities to complete the at least two partial cavities of the first layer through the intermediate layer to form at least two sealed full cavities. The at least two full cavities have different pressures within.

Abstract: A capacitance type sensor has a semiconductor substrate having a vertically opened penetration hole, a movable electrode film arranged above the penetration hole such that a periphery portion opposes to a top surface of the semiconductor substrate with a gap provided, and a fixed electrode film arranged above the movable electrode film with a gap with respect to the movable electrode film. A concave portion having at least a part thereof formed by an inclined surface is provided in the top surface of the semiconductor substrate in a region of the top surface of the semiconductor substrate which overlaps the periphery portion of the movable electrode film.

Abstract: A method of forming a MEMS structure, in which an etch stop layer is formed to be buried within the inter-dielectric layer and, during an etch of the substrate and the inter-dielectric layer from backside to form a chamber, the etch stop layer protect the remaining inter-dielectric layer. The chamber thus formed has an opening at a backside of the substrate, a ceiling opposite to the opening, and a sidewall joining the ceiling. The sidewall may further include a portion of the etch stop layer.

Abstract: A MEMS device includes a dual membrane, an electrode, and an interconnecting structure. The dual membrane has a top membrane and a bottom membrane. The bottom membrane is positioned between the top membrane and the electrode and the interconnecting structure defines a spacing between the top membrane and the bottom membrane.

Abstract: A method of modifying stress characteristics of a membrane in one embodiment includes providing a membrane layer, determining a desired stress modification, and forming at least one trough in the membrane layer based upon the determined desired stress modification.

Abstract: A MEMS inertial sensor and a method for manufacturing the same are provided. The method includes: depositing a first carbon layer on a semiconductor substrate; patterning the first carbon layer to form a fixed anchor bolt, an inertial anchor bolt and a bottom sealing ring; forming a contact plug in the fixed anchor bolt and a contact plug in the inertial anchor bolt; forming a first fixed electrode, an inertial electrode and a connection electrode on the first carbon layer, where the first fixed electrode and the inertial electrode constitute a capacitor; forming a second carbon layer on the first fixed electrode and the inertial electrode; and forming a sealing cap layer on the second carbon layer and the top sealing ring. Under an inertial force, only the inertial electrode may move, the fixed electrode will almost not move or vibrate, which improves the accuracy of the MEMS inertial sensor.

Abstract: The present disclosure is directed to a device that includes a substrate and a sensor formed on the substrate. The sensor includes a chamber formed from a plurality of integrated cavities, a membrane above the substrate, the membrane having a plurality of openings, each opening positioned above one of the cavities, and a plurality of diamond shaped anchors positioned between the membrane and the substrate, the anchors positioned between each of the cavities. A center of each opening is also a center of one of the cavities.

Abstract: A micromechanical structure for a MEMS capacitive acoustic transducer, has: a substrate of semiconductor material; a rigid electrode, at least in part of conductive material, coupled to the substrate; a membrane, at least in part of conductive material, facing the rigid electrode and coupled to the substrate, which undergoes deformation in the presence of incident acoustic pressure waves and is arranged between the substrate and the rigid electrode and has a first surface and a second surface, in fluid communication, respectively, with a first chamber and a second chamber, the first chamber being delimited at least in part by a first wall portion and by a second wall portion formed by the substrate, and the second chamber being delimited at least in part by the rigid electrode; and a stopper element, connected between the first and second wall portions for limiting the deformations of the membrane. At least one electrode-anchorage element couples the rigid electrode to the stopper element.

Abstract: A micromechanical component including a first composite of a plurality of semiconductor chips, the first composite having a first front and back surfaces, a second composite of a corresponding plurality of carrier substrates, the second composite having a second front and back surfaces; wherein the first front surface and the second front surface are connected via a structured adhesion promoter layer in such a way that each semiconductor chip is connected, essentially free of cavities, to a corresponding carrier substrate corresponding to a respective micromechanical component.

Abstract: Provided is a structure for improving performance of a micro electro mechanical system (MEMS) microphone by preventing deformation from occurring due to a residual stress and a package stress of a membrane and by decreasing membrane rigidity. A MEMS microphone according to the present disclosure includes a backplate formed on a substrate; an insulating layer formed on the substrate to surround the backplate; a membrane formed to be separate from above the backplate by a predetermined interval; a membrane supporting portion configured to connect the membrane to the substrate; and a buffering portion formed in a double spring structure between the membrane and the membrane supporting portion.

Abstract: A method for forming a MEMS device is provided. The method includes the following operations of providing a substrate having a first portion and a second portion; fabricating a membrane type sensor on the first portion of the substrate using a double-side process; and fabricating a bulk silicon sensor on the second portion of the substrate.

Abstract: A MEMS backplate enables MEMS microphones with reduced parasitic capacitance. A MEMS backplate includes a central area and a perforation in the central area. A suspension area surrounds the central area at least partially. An aperture is disposed in the suspension area.

Abstract: A MEMS microphone has reduced parasitic capacitance. The microphone includes a trench electrically separating an acoustically active section of the backplate from an acoustically inactive section of the backplate.

Abstract: A mechanism for reducing stiction in a MEMS device by decreasing an amount of carbon from TEOS-based silicon oxide films that can accumulate on polysilicon surfaces during fabrication is provided. A carbon barrier material film is deposited between one or more polysilicon layer in a MEMS device and the TEOS-based silicon oxide layer. This barrier material blocks diffusion of carbon into the polysilicon, thereby reducing accumulation of carbon on the polysilicon surfaces. By reducing the accumulation of carbon, the opportunity for stiction due to the presence of the carbon is similarly reduced.

Abstract: An improved method for the fabrication of Micro-Electro-Mechanical Systems (MEMS), Nano-Electro-Mechanical Systems (NEMS), Photonics, Nanotechnology, 3-Dimensional Integration, Micro- and Nano-Fabricated Devices and Systems for both rapid prototyping development and manufacturing is disclosed. The method includes providing a plurality of different standardized and repeatable process modules usable in fabricating the devices and systems, defining a process sequence for fabricating a predefined one of the devices or systems, and identifying a series of the process modules that are usable in performing the defined process sequence and thus in fabricating the predefined device or system.

Abstract: A micro-channel structure having variable depths includes a substrate and a cured layer formed on the substrate. At least first and second micro-channels are embossed in the cured layer. The first micro-channel has a bottom surface defining a first depth and the second micro-channel has a bottom surface defining a second depth different from the first depth. A cured electrical conductor is making a micro-wire is formed in each of the first and second micro-channels over their respective bottom surfaces.

Abstract: A micropatterned component, for measuring accelerations and/or yaw rates, including a substrate having a principal plane of extension of the substrate, an electrode, and a further electrode; the electrode having a principal plane of extension of the electrode, and the further electrode having a principal plane of extension of the further electrode; the principal plane of extension of the electrode being set parallelly to a normal direction perpendicular to the principal plane of extension of the substrate; the principal plane of extension of the further electrode being set parallelly to the normal direction; the electrode having an electrode height extending in the normal direction; the electrode having a flow channel extending completely through the electrode in a direction parallel to the principal plane of extension of the substrate; the flow channel having a channel depth extending parallelly to the normal direction; the channel depth being less than the electrode height.

Abstract: A piezoelectric MEMS microphone comprising a multi-layer sensor that includes at least one piezoelectric layer between two electrode layers, with the sensor being dimensioned such that it provides a near maximized ratio of output energy to sensor area, as determined by an optimization parameter that accounts for input pressure, bandwidth, and characteristics of the piezoelectric and electrode materials. The sensor can be formed from single or stacked cantilevered beams separated from each other by a small gap, or can be a stress-relieved diaphragm that is formed by deposition onto a silicon substrate, with the diaphragm then being stress relieved by substantial detachment of the diaphragm from the substrate, and then followed by reattachment of the now stress relieved diaphragm.

Abstract: A piezoelectric device includes a piezoelectric thin film formed by separating and forming a piezoelectric single crystal substrate, an inorganic layer formed on a back surface of the piezoelectric thin film, an elastic body layer disposed on a surface opposite to the piezoelectric thin film of the inorganic layer, and a support pasted to a surface opposite to the inorganic layer of the elastic body layer. In a membrane structure portion, the inorganic layer and the elastic body layer are disposed on the piezoelectric thin film through a gap layer. The elastic body layer reduces a stress caused by pasting the piezoelectric thin film including the inorganic layer and the support and has a certain elastic modulus. The inorganic layer is formed with a material having an elastic modulus higher than that of the elastic body layer and suppresses damping caused by disposing the elastic body layer.

Abstract: An assembly (20) includes a MEMS die (22) having a pressure transducer device (40) formed on a substrate (44) and a cap layer (38). A packaging process (74) entails forming the device (40) on the substrate, creating an aperture (70) through a back side (58) of the substrate (44) underlying a diaphragm (46) of the device (40), and coupling a cap layer (38) to the front side of the substrate (44) overlying the device (40). A trench (54) is produced extending through both the cap layer (38) and the substrate (44), and surrounds a cantilevered platform (48) at which the diaphragm (46) resides. The die (22) is suspended above a substrate (26) so that a clearance space (60) is formed between the platform (48) and the substrate (26). The diaphragm (46) is exposed to an external environment (68) via the aperture (70) and the space (60), and an external port.

Abstract: The present invention relates to a method of manufacturing a capacitive micro- machined transducer (100), in particular a CMUT, the method comprising depositing a first electrode layer (10) on a substrate (1), depositing a first dielectric film (20) on the first electrode layer (10), depositing a sacrificial layer (30) on the first dielectric film (20), the sacrificial layer (30) being removable for forming a cavity (35) of the transducer, depositing a second dielectric film (40) on the sacrificial layer (30), depositing a second electrode layer (50) on the second dielectric film (40), and patterning at least one of the deposited layers and films (10, 20, 30, 40, 50), wherein the depositing steps are performed by Atomic Layer Deposition. The present invention further relates to a capacitive micro-machined transducer (100), in particular a CMUT, manufactured by such method.

Abstract: Methods for the fabrication of a Microelectromechanical Systems (“MEMS”) device are provided. In one embodiment, the MEMS device fabrication method includes forming a via opening extending through a sacrificial layer and into a substrate over which the sacrificial layer has been formed. A body of electrically-conductive material is deposited over the sacrificial layer and into the via opening to produce an unpatterned transducer layer and a filled via in ohmic contact with the unpatterned transducer layer. The unpatterned transducer layer is then patterned to define, at least in part, a primary transducer structure. At least a portion of the sacrificial layer is removed to release at least one movable component of the primary transducer structure. A backside conductor, such as a bond pad, is then produced over a bottom surface of the substrate and electrically coupled to the filled via.

Abstract: The present disclosure relates to a pressure sensor having a nanostructure and a method for manufacturing the same. More particularly, it relates to a pressure sensor having a nanostructure attached on the surface of the pressure sensor and thus having improved sensor response time and sensitivity and a method for manufacturing the same. The pressure sensor according to the present disclosure having a nanostructure includes: a substrate; a source electrode and a drain electrode arranged on the substrate with a predetermined spacing; a flexible sensor layer disposed on the source electrode and the drain electrode; and a nanostructure attached on the surface of the flexible sensor layer and having nanosized wrinkles.

Abstract: There are many inventions described and illustrated herein. In one aspect, the present inventions relate to devices, systems and/or methods of encapsulating and fabricating electromechanical structures or elements, for example, accelerometer, gyroscope or other transducer (for example, pressure sensor, strain sensor, tactile sensor, magnetic sensor and/or temperature sensor), filter or resonator. The fabricating or manufacturing microelectromechanical systems of the present invention, and the systems manufactured thereby, employ wafer bonding encapsulation techniques.

Abstract: A method of fabricating a MEMS microphone includes: first providing a substrate having a first surface and a second surface. The substrate is divided into a logic region and a MEMS region. The first surface of the substrate is etched to form a plurality of first trenches in the MEMS region. An STI material is then formed in the plurality of first trenches. Subsequently, the second surface of the substrate is etched to form a second trench in the MEMS region, wherein the second trench connects with each of the first trenches. Finally, the STI material in the first trenches is removed.

Abstract: An electromechanical transducer includes a first electromagnetic element and a second electromagnetic element, such as electrodes, disposed opposite to each other with a sealed cavity therebetween. The sealed cavity is formed by removing a sacrifice layer and then performing sealing. A sealing portion is formed by superposing a film of a hardened second sealing material that has fluidity at normal temperature on a film of a first sealing material that does not have fluidity at normal temperature.

Abstract: A sensor assembly includes a first wafer having a cavity formed therein and a second wafer bonded relative to the first wafer to form a diaphragm over the cavity. A trench is formed in the second wafer in or around the diaphragm and the trench may be filled with an isolating material to help thermally and/or electrically isolate the diaphragm. The diaphragm may support one or more sense elements. The sensor assembly may be used a flow sensor, a pressure sensor, a temperature sensor, and/or any other suitable sensor, as desired.

Abstract: Semiconductor nano pressure sensor devices having graphene membrane suspended over open cavities formed in a semiconductor substrate. A suspended graphene membrane serves as an active electro-mechanical membrane for sensing pressure, which can be made very thin, from about one atomic layer to about 10 atomic layers in thickness, to improve the sensitivity and reliability of a semiconductor pressure sensor device.

Abstract: The invention relates to a method for manufacturing a micromachined microphone and an accelerometer from a wafer 1 having a first layer 2, the method comprising the steps of dividing the first layer 2 into a microphone layer 5 and into an accelerometer layer 6, covering a front side of the microphone layer 5 and a front side of the accelerometer layer 6 with a continuous second layer 7, covering the second layer 7 with a third layer 8, forming a plurality of trenches 9 in the third layer 8, removing a part 10 of the wafer 1 below a back side of the microphone layer 5, forming at least two wafer trenches 11 in the wafer 1 below a back side of the accelerometer layer 6, and removing a part 12, 13 of the second layer 7 through the plurality of trenches 9 formed in the third layer 8. The micromachined microphone and the accelerometer according to the invention is advantageous over prior art as it allows for body noise cancellation in order to minimize structure borne sound.

Abstract: Disclosed is an integrated circuit comprising a substrate (10) including semiconductor devices and a metallization stack (20) over said substrate for interconnecting said devices, the metallization stack comprising a cavity (36), and a thermal conductivity sensor comprising at least one conductive portion (16, 18) of said metallization stack suspended in said cavity. A method of manufacturing such an IC is also disclosed.

Abstract: A MEMS comprises a back-plate (7) having an inner portion (7a) and an outer portion (7b), the inner portion (7a) connected to the outer portion (7b) by a sidewall (7c). A raised section or anchor ring (60) is formed in the outer portion (7b) of the back-plate, in a region of the back-plate near the inner perimeter of the outer portion. The anchor ring may comprise angled sidewalls. The thickness of the back-plate may be greater than the thickness of the material supporting the anchor ring. Embodiments are also disclosed in which a membrane comprises a raised portion and an outer portion connected by an angled sidewall.