WO1995035642A1 - Transducteur ultrasonore et procede de fabrication d'un tel transducteur - Google Patents
Transducteur ultrasonore et procede de fabrication d'un tel transducteur Download PDFInfo
- Publication number
- WO1995035642A1 WO1995035642A1 PCT/FR1995/000753 FR9500753W WO9535642A1 WO 1995035642 A1 WO1995035642 A1 WO 1995035642A1 FR 9500753 W FR9500753 W FR 9500753W WO 9535642 A1 WO9535642 A1 WO 9535642A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- layer
- substrate
- fixed electrode
- silicon nitride
- membrane
- Prior art date
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H11/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by detecting changes in electric or magnetic properties
- G01H11/06—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by detecting changes in electric or magnetic properties by electric means
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
- B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
- B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
- B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
- B06B1/0292—Electrostatic transducers, e.g. electret-type
Definitions
- the present invention relates to an ultrasonic transducer consisting of a membrane and a fixed electrode as well as to the methods for producing said membrane and fixed electrode and to the method for manufacturing said ultrasonic transducer from the membrane and the electrode. fixed.
- piezoelectric effect transducers which conventionally consist of a ceramic piezoelectric disc mounted on a substrate and provided with one or more adaptation layers d 'impedance.
- the ceramic structure of such a transducer can resonate radially or according to its thickness or even in a combined manner. These transducers are very resonant up to frequencies above 100 kHz and over a narrow frequency band but nevertheless offer poor efficiency in terms of radiated power.
- the second major family of ultrasonic transducers of the bimorph type are these transducers which generally consist of a vibrating membrane under which a piezoelectric disc is disposed.
- transducers which are more sensitive than the aforementioned piezoelectric effect transducers, are very resonant but, on the other hand, do not make it possible to reach resonant frequencies greater than 100 kHz.
- the Applicant has realized that it would be advantageous to be able to manufacture very resonant ultrasonic transducers with a defined resonance peak with an easily reproducible precision from one transducer to another and according to an inexpensive manufacturing process.
- This resonance peak should be able to be obtained over the ultrasonic range and in particular from 100 kHz.
- the present invention thus relates to an ultrasonic transducer comprising a silicon nitride membrane with a thickness of between 0.1 and 0.5 ⁇ m with an intrinsic mechanical stress between 100 MPa and 1.3 GPa, and a fixed electrode produced in rigid non-metallic material and provided with a plurality of orifices of small average diameter, said fixed electrode defining with said membrane an internal space of thickness between 1 and 5 ⁇ m.
- This ultrasonic transducer has, because of its manufacturing process, all the qualities required to have an adjustable ultrasonic resonance frequency, greater than 20 kHz, defined with high precision which is moreover perfectly reproducible. This is due in particular to the low mass and the high rigidity of the membrane which can be obtained by the manufacturing process. It is entirely possible to give the membrane an intrinsic mechanical stress between 100 MPa and 1.3 GPa and thus adjust the resonance frequency of the ultrasonic transducer to a value between 20 kHz and 1 MHz.
- the silicon nitride membrane has a thickness preferably of between 0.3 and 0.5 ⁇ m
- the fixed electrode is made of semiconductor material or ceramic
- the fixed electrode has a thickness greater than 20 ⁇ m, - the orifices of the fixed electrode have an average diameter of between 25 and 100 ⁇ m.
- the present invention also relates to a process for producing a membrane used in the manufacture of the aforementioned ultrasonic transducer, characterized in that it consists in performing the following steps:
- an electrical insulating layer is formed on two opposite faces, called front and rear, of a substrate made of semiconductor material,
- a layer of silicon nitride is deposited on each of the two layers of insulator, a material suitable for the reduction of the intrinsic mechanical stress of said layer of silicon nitride is implanted ionically in the layer of silicon nitride situated on the front face of said substrate;
- said substrate is etched anisotropically from its rear face, - c) and the insulating layer located on the front face of the substrate is selectively etched
- this method includes a step of ion implantation of a thin layer of silicon nitride, for example of the order of 0.1 to 0.5 ⁇ m, which makes it possible to reduce the intrinsic mechanical stress of said layer. .
- the ions thus implanted create defects in the layer of silicon nitride, consequently inducing a relaxation of the intrinsic mechanical stress.
- the ion implantation is carried out with a dose of ions coming from a material belonging to columns III to V of the periodic table of the elements and, for example from Boron, between 5.10 13 and 5.10 15 ions / cm 2 and the acceleration energy of these ions is between 35 and 150 keV.
- the energy of the ions is calculated so as to obtain the maximum of ions at the interface between the layer of silicon nitride and the layer of underlying electrical insulator.
- An annealing operation is then carried out on the substrate coated with its layer of ion-implanted silicon nitride in order to increase the mechanical stress of said layer.
- Annealing takes place in a range of temperatures from 500 to 800 ° C. for a period of between 15 minutes and a few hours. Thanks to annealing, it is therefore possible to precisely adjust the ultrasonic resonance frequency to the desired value. Furthermore, annealing provides better reproducibility of the mechanical stress values in the membrane from one substrate to another compared to a simple ion implantation.
- Annealing also improves the long-term stability of the mechanical stress in the silicon nitride layer and therefore improves the stability of the future ultrasonic transducer.
- the Applicant has realized that it is more advantageous to use a layer of silicon nitride (membrane) of thickness between 0.3 and 0.5 ⁇ m in order to reduce its brittleness and therefore improve its mechanical behavior during the following steps of forming the membrane by etching as well as the other steps.
- this thickness range constitutes the best possible compromise between the solidity of the membrane and its sensitivity, in terms of conversion of mechanical energy into acoustic energy and also of conversion of acoustic energy into mechanical energy.
- the electrical insulating layer is formed by thermal oxidation of the two faces of the substrate and the insulating layer has for example a thickness of 1 ⁇ m, and this thickness can even be less than 1 ⁇ m.
- the electrical contact is obtained by metallization of the rear face of the substrate.
- the layers of silicon nitride and insulator which remain on the rear face of the substrate are removed by selective etching.
- the silicon nitride layer is deposited, its ion implantation, optionally its annealing and then, said ion implanted silicon nitride layer is structured so as to leave the peripheral insulating layer which will be used to release define the internal space and which will receive for example a sealing agent such as "PYREX" for the final assembly of the ultrasonic transducer.
- a sealing agent such as "PYREX” for the final assembly of the ultrasonic transducer.
- this embodiment allows better control of the formation of the internal space between the membrane and a fixed electrode.
- the thickness of the layer of electrical insulator which is for example formed by thermal oxidation of the two faces of the substrate has a thickness which must be greater than 1 ⁇ m thus making it possible to predetermine the thickness of the internal space.
- the present invention also relates to a method for producing a fixed electrode used in the manufacture of the aforementioned ultrasonic transducer, characterized in that it consists in carrying out the following steps from a substrate of semiconductor material having two opposite faces say front and back:
- At least one protective layer is formed on the rear face of said substrate - the fixed electrode is formed, on the one hand, by selectively etching said protective layer located on the rear face of the substrate and, on the other hand, by etching anisotropically said substrate from its rear face, after having previously protected the front face against anisotropic etching, - one etches in said substrate a main cavity located opposite said fixed electrode and at least one secondary cavity intended to electrical contacts,
- At least one layer of electrical insulation is formed in the. central cavity and in at least one secondary cavity, - a metal protective layer is formed on the front face of the substrate, - Selectively etching in line with said main cavity said metallic layers, of insulation and the fixed electrode so as to form a plurality of orifices in said fixed electrode.
- the main cavity is between 1.5 and 2.5 ⁇ m deep.
- the protective layer on the rear face of the substrate is made of an electrical insulator resistant to etching agents and can be made of silicon nitride, but it is then preferable to perform an ion implantation of said layer with a material belonging to columns III. to V of the periodic classification of the elements with a view to reducing the intrinsic mechanical stress of the latter and therefore of adapting this stress to that of the substrate.
- first layer in contact with said substrate being formed of an electrical insulator such as an oxide and a second layer of silicon nitride on which it does not it is not necessary to perform an ion implantation since it is not in direct contact with the substrate.
- the electrical insulator layer is then formed in the main cavity and in at least one secondary cavity by deposition of an electrical insulator layer and then by etching of said layer.
- the layer of electrical insulator is etched in the secondary cavity provided to establish electrical contact with the substrate.
- said metallic protective layer is etched so as to form electrical contacts facing the main and secondary cavities. It is also possible to subsequently make electrical contact with the substrate and, on the other hand, to form the orifices of the fixed electrode before making this contact, but this further complicates the process.
- the invention also relates to a method of manufacturing the aforementioned ultrasonic transducer from the membrane and the fixed electrode respectively obtained by the previously mentioned methods.
- a sealing agent is deposited on a peripheral part of the front face of the membrane or of the fixed electrode, the membrane is positioned opposite the fixed electrode and they are assembled so that they form between them an internal space of small thickness, for example between 1 and 5 ⁇ m.
- the sealing agent used can be an adhesive, "PYREX” (registered trademark) or any other suitable sealing agent.
- the sealing agent is "PYREX”
- the assembly is done by an anodic sealing and it is therefore planned, before depositing the "PYREX”, to remove from the front and rear faces of the fixed electrode the remaining parts various layers having served as protection, to remove from the front face of the membrane the possible protective layer and to form on the non-etched areas of said front face of the fixed electrode a final protective layer.
- FIGS. 1 to 12 are cross-sectional views each representing an important step in the process for producing a membrane used for the manufacture of an ultrasonic transducer according to an embodiment of the invention
- FIGS. 13 to 23 are cross-sectional views each representing an important step in the process for producing a fixed electrode used for the manufacture of an ultrasonic transducer according to an embodiment of the invention
- FIG. 24 is a cross-sectional view showing the ultrasonic transducer assembled according to the invention.
- FIG. 25 shows a frequency response curve of an ultrasonic transducer according to the invention with a resonant frequency at 100 kHz.
- the production methods according to the invention obviously make it possible to simultaneously produce several membranes and several fixed electrodes from the same substrate for each process and therefore therefore to simultaneously manufacture several ultrasonic transducers in the form of '' a network of transducers.
- a substrate 1 of p-doped average resistivity 1 between 1 and 20 ⁇ / cm is used, and for example a monocrystalline silicon wafer whose crystal orientation is of the type ⁇ 100> of equal thickness at 520 ⁇ m and which has two large opposite faces 1a, 1b called front and rear.
- This wafer 1 is cleaned in the usual manner and then an electric insulating layer 2, 3 is formed on each of its large opposite faces.
- thermal oxidation of the silicon is carried out for example on 1 ⁇ m as shown in the figure. 1.
- the next step, the result of which is illustrated in FIG. 2, consists in delimiting the internal space which will form with the membrane and the fixed electrode a variable capacity.
- a layer of photosensitive resin (not shown) is deposited, for example with a spinner, on the oxide layer 2 on the front face 1a of the wafer 1, annealing is carried out at 60 ° C., a photogravure mask (not shown), with said wafer, this resin layer is exposed through said mask, the exposed resin layer is developed with the mask, another annealing is carried out at 120 ° C., an etching of the oxide layer 2 in the central part using an etchant such as hydrofluoric acid in dilute solution to form the internal space.
- an etchant such as hydrofluoric acid in dilute solution to form the internal space.
- the next step (fig. 3) of the process consists in depositing a layer of silicon nitride 4, 5 of between 0.1 and 0.5 ⁇ m and for example around 0.3 ⁇ m on each of the two oxidized faces or partially oxidized from the wafer 1. This deposition is carried out, for example, by a known technique of low pressure chemical vapor deposition (LPCVD).
- LPCVD low pressure chemical vapor deposition
- An ion implantation is then carried out, in the silicon nitride layer 4 situated on the front face of the wafer, of a material belonging to columns III to V of the periodic table of the elements, such as for example boron in order to reduce the intrinsic mechanical stress of said layer of silicon nitride (FIG. 4).
- a material belonging to columns III to V of the periodic table of the elements such as for example boron
- Another suitable material for ion implantation of oxygen can also be used.
- an ion dose between 5.10 " ! 3 and 5.10 15 ions / cm 2 is used, for example equal to 2.10 15 ions / cm 2.
- the ion acceleration energy is between 35 and 150 kev and is for example equal to 100 kev. The choice of the dose of ions and the energy of acceleration is made according to their size and their mass.
- an annealing operation is carried out in an oven at a temperature of 600 ° C. for 30 minutes.
- annealing therefore makes it possible to increase the intrinsic mechanical stress of the silicon nitride and to obtain this stress with great precision and thereby the resonance frequency of the future ultrasonic transducer, which is very useful if the stress was too strongly reduced during ion implantation or if the constraint approaches by desired value the desired value but with insufficient precision.
- this membrane is then structured from the face back.
- a layer of photosensitive resin (not shown) is deposited on the spinner on the rear face of the wafer, that is to say on the outer face of layer 5, an annealing is carried out at 60 ° C.
- a photogravure mask (not shown) with the wafer, this layer of resin is exposed through said mask, another annealing is carried out and carried out at 120 ° C.
- the silicon nitride layer 5 is selectively etched by reactive ion attack (RIE) in the presence of sulfur hexafluoride and oxygen ions (dry etching), then the oxide layer 3 by wet etching. in a 1: 7 HF / NH4F solution.
- RIE reactive ion attack
- the oxide layer 3 by wet etching. in a 1: 7 HF / NH4F solution.
- the remaining photosensitive resin layer is then removed and the surfaces are conventionally cleaned.
- a peripheral zone is then obtained formed by a part 5a of the silicon nitride layer and by a part 3a of the oxide layer leaving the rear face 1b of exposed on a central zone. plate 1.
- a photogravure is then carried out on the front face of the wafer so as to etch the layer 4 of silicon nitride to reveal the peripheral zone 2a of the oxide layer 2.
- This photogravure is identical to that described previously and comprises the following steps :
- a layer 6 of "PYREX 7740" (registered trademark) between 1 and 3 ⁇ m and for example 2 ⁇ m is deposited by cathodic deposition or by vacuum evaporation.
- a photogravure is then carried out on the front face of the wafer 1 so as to etch the layer 6 of "PYREX” to reveal the remaining central zone 4a of the layer 4 of ionically implanted silicon nitride and thus form a peripheral zone 6a of the layer of "PYREX” (figure 8). This photoengraving is carried out according to the steps explained above:
- Layer 6 of "PYREX” is then etched (wet etching) in a dilute HF solution.
- sealing agent which can be an adhesive and for example a polyimide or an epoxy resin, is deposited only after having produced the membrane and the fixed electrode, just before assembly.
- Another variant could consist in preforming the internal space by structuring a peripheral zone 2a of the oxide layer 2 on the front face of the wafer 1 as already described but in depositing the layer of "PYREX” only after having carried out the membrane and the fixed electrode. For this variant, it is however advisable to etch this layer of "PYREX” before considering sealing the membrane and the fixed electrode.
- a first step we anisotropically etches the silicon wafer 1 from its exposed rear face 1b, using a solution containing the KOH etching agent diluted to 30% and brought to a temperature of around 70 to 90 ° C.
- the wafer 1 is etched until a thickness of silicon for example of 5 ⁇ m is obtained before reaching the central zone 4a of the layer of silicon nitride 4.
- provision may be made to protect, for example mechanically with a glass plate, the front face 1a of the wafer.
- a second step (fig.10) then consists in eliminating from the rear face
- This step can be carried out by selective etching, on the one hand, by reactive ion attack in the presence of hexafluoride ions in zone 5a of the layer of silicon nitride and, on the other hand, by wet etching in a solution
- FIG. 11 represents the third stage of structuring of the membrane which consists in carrying out another anisotropic etching in 13
- This metallization layer 7 can be carried out by cathodic deposition or by vacuum evaporation.
- a substrate 10 of p-doped average resistivity between 1 and 20 ⁇ / cm, is used, and for example a monocrystalline silicon wafer whose crystal orientation is of the type ⁇ 100>, of thickness equal to 520 ⁇ m and which has two large opposite faces 10a and 10b called front and rear.
- This wafer 10 is cleaned in the usual way and then at least one protective layer is formed, consisting of an electrical insulator resistant to etching agents on the rear face 10b of said wafer.
- at least one protective layer is formed, consisting of an electrical insulator resistant to etching agents on the rear face 10b of said wafer.
- two protective layers are formed on each face 10a, 10b of the wafer.
- a first layer 11, (resp.12) is formed by thermal oxidation of the silicon on the front face 10a (resp. On the rear face 10b) over a thickness of between 0.1 and 0.3 ⁇ m and for example equal to 0.2 ⁇ m.
- a second layer 13 (resp. 14) of thickness between 0.1 and 0.3 ⁇ m, for example equal to 0.2 ⁇ m, is formed on layer 11 (resp. 12) by chemical vapor deposition at low pressure (fig. 13).
- the first step in producing the fixed electrode is carried out by selective etching of the protective layers of silicon nitride 14 and oxide 12 located on the rear face 10b of the wafer 10. To do this, a photogravure of the rear face 10b is carried out by carrying out the steps already described in detail during the production of the membrane:
- the layer 14 of silicon nitride is etched by reactive ion attack (RIE) in the presence of sulfur hexafluoride ions and oxygen (dry etching) then the layer 12 of oxide is etched by wet etching in an HF / NH4F solution 1: 7.
- RIE reactive ion attack
- the remaining photosensitive resin layer is then removed and the surfaces are conventionally cleaned.
- FIG. 14 shows that the protective layers have been etched in their central part in order to release the central part from the rear face 10b of the wafer which will be subjected to an anisotropic attack.
- the next step consists in performing an anisotropic etching of the silicon wafer 10 from its rear face 10b with a solution containing an etching agent such as KOH diluted to 30% and brought to a temperature of 75 ° C.
- the silicon is thus etched until a silicon thickness of 50 ⁇ m is left, thus forming the fixed electrode (fig. 15).
- Rinsing with deionized water is then carried out, followed by conventional cleaning of the surfaces.
- a main cavity 10 of depth between 1.5 and 2.5 is formed in the manner which will be described in detail below. ⁇ m and for example equal to 1 ⁇ m situated opposite the fixed electrode 15 and at least one secondary cavity 17 intended for the electrical contacts. A second secondary cavity 18 is also formed in the same way in order to make electrical contact with the front face 10a of the wafer 10.
- photogravure is carried out on the front face of the wafer 10 according to the conventional steps:
- the layer of silicon nitride 13 is etched by reactive ion attack (RIE) in the presence of ions of sulfur hexafluoride and oxygen (dry etching) then the oxide layer 11 is etched by wet etching in an HF solution / NH4F1: 7.
- RIE reactive ion attack
- a small thickness of approximately 2 ⁇ m of the silicon wafer is then etched by reactive ion attack (RIE) in the presence of ions of sulfur hexafluoride and oxygen.
- RIE reactive ion attack
- the remaining photosensitive resin layer is removed and the surfaces are conventionally cleaned. As shown in FIG. 16, a central cavity 16 and two secondary cavities 17 and 18 are thus obtained.
- the step which follows makes it possible to obtain the result illustrated in FIG. 17 and consists in forming at least one layer of electrical insulator 20 with a thickness of between 0.5 and 2.5 ⁇ m in the central cavity 16 and in at least one secondary cavity and for example equal to 1 ⁇ m.
- an insulating layer 21, 22 is formed in each of the two secondary cavities 17 and 18.
- the insulating layer with a thickness equal to 1 ⁇ m is for example obtained by thermal oxidation at 1100 ° C of the silicon located at the bottom of the main 16 and secondary cavities 17, 18 at 1100 ° C in a dry atmosphere for 1 hour, then in humid atmosphere for 1 hour 30 minutes and finally in a dry atmosphere for 1 hour.
- the oxide layer 20 located in the central cavity 16 is etched to form a plurality of holes 23 of small average diameter between 25 and 100 ⁇ m and for example equal to 50 ⁇ m and the oxide layer 22 located in the second secondary cavity 18 is etched in order to make electrical contact with the wafer 10. For this, the following steps are carried out:
- FIG. 19 illustrates the next step of forming a metal protective layer 24 on the front face 10a of the wafer.
- This layer 24 for example of aluminum with a thickness equal to 1 ⁇ m, is deposited on the front face by cathodic deposition or evaporation under vacuum.
- a plurality of orifices 25 is formed in the fixed electrode by performing a dry etching of the silicon of the fixed electrode over its entire thickness. (approximately 50 ⁇ m) by reactive ion attack in the presence of sulfur hexafluoride ions.
- the penultimate step (fig. 22) consists in carrying out a photoetching of the metallic protective layer 24 so as to form electrical contacts facing the main 16 and secondary cavities 17 and 18. This step is carried out in the manner following: - deposit of a layer of photosensitive resin on the front face,
- Selective etching of the silicon nitride 14 is carried out on both sides of the wafer 10 by reactive ion etching in the presence of sulfur hexafluoride and the oxide layer by wet etching in a 1: 7 HF / NH4F solution.
- the internal space, after sealing, has a thickness of between 1 and 5 ⁇ m and for example equal to 3 ⁇ m.
- FIG. 25 represents a frequency response curve of an ultrasonic transducer according to the invention revealing a perfectly defined resonance peak at a frequency value of 100 kHz. This curve is typically obtained for an ultrasonic transducer having a membrane equal to 0.3 ⁇ m in width equal to 1 mm, whose intrinsic mechanical stress (after annealing) is 200 MPa and which has an internal space of 3 ⁇ m d 'thickness.
- the method according to the invention makes it possible not only to adjust the resonance frequency of the ultrasonic transducer but also to adjust the bandwidth of said transducer according to the intended application.
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Pressure Sensors (AREA)
- Transducers For Ultrasonic Waves (AREA)
Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU27427/95A AU2742795A (en) | 1994-06-17 | 1995-06-08 | Ultrasonic transducer and method for making same |
EP95922584A EP0765590A1 (fr) | 1994-06-17 | 1995-06-08 | Transducteur ultrasonore et procede de fabrication d'un tel transducteur |
TW084106939A TW289849B (fr) | 1994-06-17 | 1995-07-05 |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR94/07488 | 1994-06-17 | ||
FR9407488A FR2721471B1 (fr) | 1994-06-17 | 1994-06-17 | Transducteur ultrasonore et procédé de fabrication d'un tel transducteur. |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1995035642A1 true WO1995035642A1 (fr) | 1995-12-28 |
Family
ID=9464371
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/FR1995/000753 WO1995035642A1 (fr) | 1994-06-17 | 1995-06-08 | Transducteur ultrasonore et procede de fabrication d'un tel transducteur |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0765590A1 (fr) |
AU (1) | AU2742795A (fr) |
FR (1) | FR2721471B1 (fr) |
WO (1) | WO1995035642A1 (fr) |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6430109B1 (en) | 1999-09-30 | 2002-08-06 | The Board Of Trustees Of The Leland Stanford Junior University | Array of capacitive micromachined ultrasonic transducer elements with through wafer via connections |
ITRM20050093A1 (it) * | 2005-03-04 | 2006-09-05 | Consiglio Nazionale Ricerche | Procedimento micromeccanico superficiale di fabbricazione di trasduttori ultracustici capacitivi microlavorati e relativo trasduttore ultracustico capacitivo microlavorato. |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0561566A2 (fr) * | 1992-03-18 | 1993-09-22 | Knowles Electronics, Inc. | Microphone à condensateur à l'état solide |
-
1994
- 1994-06-17 FR FR9407488A patent/FR2721471B1/fr not_active Expired - Fee Related
-
1995
- 1995-06-08 EP EP95922584A patent/EP0765590A1/fr not_active Ceased
- 1995-06-08 WO PCT/FR1995/000753 patent/WO1995035642A1/fr not_active Application Discontinuation
- 1995-06-08 AU AU27427/95A patent/AU2742795A/en not_active Abandoned
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0561566A2 (fr) * | 1992-03-18 | 1993-09-22 | Knowles Electronics, Inc. | Microphone à condensateur à l'état solide |
Non-Patent Citations (5)
Title |
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HANNEBORG A ET AL: "Silicon-to-silicon anodic bonding with a borosilicate glass layer", JOURNAL OF MICROMECHANICS AND MICROENGINEERING, SEPT. 1991, UK, VOL. 1, NR. 3, PAGE(S) 139 - 144, ISSN 0960-1317 * |
KUHNEL W ET AL: "A silicon condenser microphone with structured back plate and silicon nitride membrane", SENSORS AND ACTUATORS A (PHYSICAL), FEB. 1992, SWITZERLAND, VOL. A30, NR. 3, PAGE(S) 251 - 258, ISSN 0924-4247 * |
KUHNEL W ET AL: "Micromachined subminiature condenser microphones in silicon", EUROSENSORS V CONFERENCE, ROME, ITALY, 30 SEPT.-2 OCT. 1991, ISSN 0924-4247, SENSORS AND ACTUATORS A (PHYSICAL), APRIL 1992, SWITZERLAND, PAGE(S) 560 - 564 * |
SCHEEPER P R ET AL: "A review of silicon microphones", SENSORS AND ACTUATORS A (PHYSICAL), JULY 1994, SWITZERLAND, VOL. A44, NR. 1, PAGE(S) 1 - 11, ISSN 0924-4247 * |
SCHEEPER P R ET AL: "A silicon condenser microphone with a silicon nitride diaphragm and backplate", JOURNAL OF MICROMECHANICS AND MICROENGINEERING, SEPT. 1992, UK, VOL. 2, NR. 3, PAGE(S) 187 - 189, ISSN 0960-1317 * |
Also Published As
Publication number | Publication date |
---|---|
FR2721471A1 (fr) | 1995-12-22 |
EP0765590A1 (fr) | 1997-04-02 |
FR2721471B1 (fr) | 1996-08-02 |
AU2742795A (en) | 1996-01-15 |
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