EP0848823A2 - Dispositif de detection d'accelerations - Google Patents

Dispositif de detection d'accelerations

Info

Publication number
EP0848823A2
EP0848823A2 EP97923288A EP97923288A EP0848823A2 EP 0848823 A2 EP0848823 A2 EP 0848823A2 EP 97923288 A EP97923288 A EP 97923288A EP 97923288 A EP97923288 A EP 97923288A EP 0848823 A2 EP0848823 A2 EP 0848823A2
Authority
EP
European Patent Office
Prior art keywords
dielectric body
electrode plates
capacitor
capacitance value
plates
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP97923288A
Other languages
German (de)
English (en)
Other versions
EP0848823A3 (fr
Inventor
Mark André DE SAMBER
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Koninklijke Philips NV
Original Assignee
Koninklijke Philips Electronics NV
Philips Electronics NV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Koninklijke Philips Electronics NV, Philips Electronics NV filed Critical Koninklijke Philips Electronics NV
Publication of EP0848823A2 publication Critical patent/EP0848823A2/fr
Publication of EP0848823A3 publication Critical patent/EP0848823A3/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
    • G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
    • G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
    • G01P15/125—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values by capacitive pick-up
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P1/00—Details of instruments
    • G01P1/02—Housings
    • G01P1/023—Housings for acceleration measuring devices
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
    • G01P15/18—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration in two or more dimensions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
    • B81B2201/00—Specific applications of microelectromechanical systems
    • B81B2201/02—Sensors
    • B81B2201/0228—Inertial sensors
    • B81B2201/0235—Accelerometers

Definitions

  • the invention relates to a device for measuring accelerations by means of a change in the capacitance value of a capacitor which is provided with two electrode plates.
  • Such a device is used for measuring accelerations which are exerted on the device.
  • the term “acceleration” here also includes the force of gravity.
  • Such a device may accordingly be used for measuring accelerations in cars in the case of collisions, but it is also possible with such a sensor to measure the direction of the force of gravity.
  • US Patent no. 5,326,726 discloses a device of the kind mentioned in the opening paragraph.
  • the known device is a capacitive acceleration transducer in which a movement of a movable electrode relative to a fixed electrode results in a capacitance change or in an electrical contact between the electrodes.
  • An acceleration will cause the movable electrode to move, thus changing the interspacing between the electrodes.
  • the change in interspacing results in a capacitance change which can be related to the acceleration to which the movable electrode was subject.
  • the known device described has the disadvantage that the measured capacitance and capacitance change is not very well reproducible. Major differences in capacitance value and in the change in capacitance value under the influence of an acceleration may thus exist between devices manufactured by one and the same production process.
  • the invention has for its object inter alia to counteract the above disadvantage.
  • the method is for this purpose characterized in that the capacitor comprises two fixed electrode plates and a dielectric body which can be displaced between the electrode plates.
  • the device according to the invention accordingly has two fixed, immovable capacitor plates between which a dielectric body having a certain mass can move under the influence of an acceleration.
  • the invention is based on the recognition that the capacitance value or capacitance change measured in the known device strongly depends on the positions of the electrode plates.
  • the capacitance value is in fact inversely proportional to the interspacing between the electrode plates. A minor deviation of this interspacing, for example caused by an inaccuracy in the production process or mechanical stresses, will lead to a major variation in the capacitance value.
  • the measure according to the invention renders the interspacing between the electrode plates constant.
  • the capacitance value now changes linearly as a result of the dielectric body being moved between the capacitor plates.
  • the exact position of the dielectric body in a direction perpendicular to the electrode plates is immaterial.
  • the dielectric body may even make contact with the electrode plates. It is only the degree to which the dielectric body is moved into the space between the plates which causes a change in the capacitance value of the capacitor. There is no risk of the dielectric body short-circuiting the electrode plates.
  • the device is characterized in that the electrode plates and the dielectric body are constructed as comparatively thin layers on a substrate.
  • the electrode plates and the dielectric body are then manufactured by means of techniques which are known, for example, in the field of the manufacture of semiconductor elements.
  • a silicon or glass substrate may be used, for example, as the substrate.
  • Such an embodiment of the device has the advantage that the device can be manufactured with comparatively small dimensions and with a high accuracy by means of standard techniques.
  • the dielectric body may be provided so as to lie loose between the electrode plates, for example provided with guides and an end stop. It is possible then to measure the position of the dielectric body relative to the electrode plates. When the device is tilted, the dielectric body can slide under the influence of the force of gravity. Thus, for example, the direction of the force of gravity relative to the device can be measured.
  • the dielectric body is connected to a spring. The acceleration will then act on the mass of the dielectric body. The acceleration force exerted on the dielectric body will cause the dielectric body to shift and thus load the spring. The acceleration force and the spring force are in equilibrium then. The displacement of the dielectric body between the electrode plates in that case is a measure for the acceleration.
  • the dielectric body is provided with an additional mass.
  • the sensitivity of the device to accelerations can be influenced thereby.
  • the acceleration force is influenced in that the mass of the dielectric body is changed, which will lead to a different displacement of the dielectric body, and thus a different capacitance value of the capacitor, with the spring remaining the same.
  • Fig. 1 is a plan view of an embodiment of a device according to the invention
  • Fig. 2 is a cross-section taken on the line A-A in Fig. 1 of a device according to the invention
  • Figs. 3 to 6 are cross-sections taken on the line A-A in Fig. 1 of various stages in the manufacture of a device according to the invention.
  • Figs. 1 and 2 show an embodiment of a device according to the invention for measuring accelerations by means of a change in the capacitance value of a capacitor 1.
  • Fig. 1 is a plan view and Fig. 2 a cross-section taken on the line A-A in Fig. 1.
  • the capacitor 1 is provided with two electrode plates 2, 3.
  • the capacitor 1 comprises two fixed electrode plates 2, 3 and a dielectric body 4 which can be moved between the electrode plates.
  • the device according to the invention thus has two fixed, immovable capacitor plates 2, 3 between which a dielectric body 4 having a certain mass can move under the influence of an acceleration 20.
  • the dielectric body 4 is connected to a spring 5 in the present example.
  • an acceleration force 20 is exerted on the mass of the dielectric body 4, the dielectric body 4 will slide between the electrode plates 2, 3 and load the spring 5. The acceleration force and the spring force will then reach an equilibrium (see Fig. 1). The degree to which the dielectric body 4 has moved to between the electrode plates 2, 3 then is a measure for the acceleration which obtains.
  • This first embodiment of the device is manufactured by techniques which are known from the manufacture of semiconductor elements (IC technology).
  • Figs. 3 to 6 show stages in the manufacture of the device.
  • the electrode plates 2, 3 and the dielectric body 4 are constructed as comparatively thin layers on a substrate 10.
  • the manufacture of this embodiment of the device starts with a glass substrate 10.
  • a 2 ⁇ m thick TiPtAu layer is provided on this glass substrate 10 by a standard sputtering technique and patterned by standard photolithographic and etching techniques.
  • the electrode plates 2, 3 are created thereby (see Fig. 3).
  • a so-called sacrificial layer 11 of 0.5 ⁇ m thick silicon oxide is provided over the electrode plates 2, 3 by a CVD (Chemical Vapor Deposition) process (see Fig. 4).
  • the sacrificial layer 11 is given a hole 12 down to the substrate (the location of the hole 12 is shown in the plan view of Fig. 1) by means of standard photolithographic and etching techniques.
  • a layer 4 of a dielectric material is provided over the sacrificial layer 11 then, in this example a 1 ⁇ thick layer of PZT (lead- zirconium-titanate, see Fig. 5).
  • the layer 4 is provided in a standard manner by a sol-gel technique.
  • This layer is subsequently fired at 700 °C in O 2 and patterned by means of photolithographic and etching techniques so as to create the dielectric body 4 and the spring 5 (see Fig. 6).
  • the dielectric body is provided with an additional mass 14.
  • the sensitivity of the device to accelerations can be influenced in this manner. A change in the mass of the dielectric body 4 influences the acceleration force, which will lead to a different displacement with the spring 5 remaining the same.
  • the additional mass 14 is provided in this example by retaining a certain overlap over the electrode plates 2, 3 during etching of the layer 12.
  • the sacrificial layer 11 is now removed by an isotropic etching technique with HF.
  • the dielectric body 4 with the additional mass 14 and the spring 5 then become freely movable.
  • the spring is connected to the substrate through the hole 12 only.
  • the device thus obtained can be manufactured to a high accuracy, while manufacturing tolerances are narrow.
  • the invention is not limited to the embodiment described above, but variations are possible within the scope of the invention.
  • the device may alternatively be used for indicating a position.
  • the device is provided with several capacitors in that case, comprising fixed electrode plates between which there is a common space.
  • the dielectric body is present in this space and can move freely therein, the position being derived from the position of the dielectric body with respect to the electrode plates of the different capacitors. It is thus possible to manufacture a device according to the invention in that a dielectric body is provided on a spring between two conductive surfaces, for example silicon slices. In the example, the dielectric body is linearly moved between the electrode plates. It is quite possible, however, for this body to perform a rotary movement between the electrode plates.
  • the electrode plates may very well be manufactured from a material other than gold, for example a metal such as aluminum, chromium, copper, tungsten, or suicides, or a conductive monocrystalline, polycrystalline, or non-crystalline semiconductor material such as silicon.
  • a metal such as aluminum, chromium, copper, tungsten, or suicides, or a conductive monocrystalline, polycrystalline, or non-crystalline semiconductor material such as silicon.
  • the sacrificial layer may be manufactured from a material other than silicon oxide. It is important that the material of the sacrificial layer should be capable of selective etching with respect to the material of the electrode plates and the material of the dielectric body. Such combinations are known.
  • a lateral capacitor is manufactured in the embodiment, i.e. the direction from the one electrode plate via the dielectric body to the other electrode plate runs parallel to a main surface of the substrate. It is alternatively possible for this direction to be transverse, i.e. perpendicular to the substrate. In that case, first a first, subjacent electrode plate is manufactured on the substrate, then a sacrificial layer, the dielectric body, a second sacrificial layer, and finally the second, upper electrode plate, whereupon the sacrificial layers are removed.
  • a transverse device may be realized in a simple manner, for example, in that a conductive silicon substrate is used as the first electrode plate, while the second, upper electrode is made from metal.
  • the electrode plates and/or the dielectric body may be provided with holes or slots for facilitating the removal of the sacrificial layer by etching.
  • the additional mass was made from the same material as the dielectric body 4. It is also possible to manufacture the additional mass from a different material than the dielectric material, for example through the provision of a further layer and patterning of this layer.
  • the device may be manufactured as a stand-alone device. It is alternatively possible for the device to be manufactured in the back end of a semiconductor manufacturing process. The metal and dielectric layers available in that process are utilized in that case.
  • the substrate used for the device then comprises, for example, semiconductor devices which serve for measuring the capacitance value of the capacitor and for further processing of this value.
  • the example described relates to a device manufactured by semiconductor manufacturing techniques. Although this is to be preferred on account of the manufacturing accuracy and reproducibility thereof, it implies by no means that a device according to the invention can be manufactured only by these techniques.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Pressure Sensors (AREA)
  • Measuring Fluid Pressure (AREA)

Abstract

La présente invention porte sur un dispositif qui mesure les accélérations en modifiant la valeur de capacité d'un condensateur (1) doté de deux plaques d'électrodes (2, 3). Conformément à cette invention, le dispositif se caractérise par le fait que le condensateur (1) comprend deux plaques d'électrodes (2, 3) fixes et un corps diélectrique (4) pouvant se déplacer entre les deux plaques d'électrodes (2, 3). Ce dispositif est donc composé de deux plaques (2, 3) de condensateur fixées de façon définitive, entre lesquelles un corps diélectrique (4) ayant une certaine masse se déplace sous l'influence d'une force d'accélération (20). La mesure effectuée conformément à la présente invention permet de garder constante la distance entre les deux plaques d'électrodes (2, 3). La valeur de capacité connaît une évolution linéaire du fait que le corps diélectrique (4) se déplace entre les plaques (2, 3) de condensateur pour s'écarter plus ou moins de celles-ci, ce qui rend tout traitement supplémentaire de la valeur de capacité relativement simple. En outre, ledit dispositif élimine tout risque de court-circuitage des deux plaques d'électrodes (2, 3).
EP97923288A 1996-07-08 1997-06-10 Dispositif de detection d'accelerations Withdrawn EP0848823A3 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
EP96201900 1996-07-08
EP96201900 1996-07-08
PCT/IB1997/000671 WO1998001761A2 (fr) 1996-07-08 1997-06-10 Dispositif de detection d'accelerations

Publications (2)

Publication Number Publication Date
EP0848823A2 true EP0848823A2 (fr) 1998-06-24
EP0848823A3 EP0848823A3 (fr) 1999-05-06

Family

ID=8224154

Family Applications (1)

Application Number Title Priority Date Filing Date
EP97923288A Withdrawn EP0848823A3 (fr) 1996-07-08 1997-06-10 Dispositif de detection d'accelerations

Country Status (4)

Country Link
EP (1) EP0848823A3 (fr)
JP (1) JPH11513118A (fr)
KR (1) KR19990044488A (fr)
WO (1) WO1998001761A2 (fr)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA2403052A1 (fr) 2001-01-24 2002-08-01 The Regents Of The University Of Michigan Dispositif micromecanique a coefficient q eleve et son procede de reglage
FR2817050A1 (fr) * 2001-03-07 2002-05-24 Commissariat Energie Atomique Brasseur optique a voies guidees et procedes de realisation d'un tel brasseur
US7137300B2 (en) * 2003-03-19 2006-11-21 California Institute Of Technology Parylene capacitive accelerometer utilizing electrical fringing field sensing and method of making
CN113156168B (zh) * 2021-05-11 2025-07-01 中国人民解放军空军工程大学 一种基于气体电容电场效应的加速度传感验证装置及方法
CN115015580B (zh) * 2022-05-31 2025-10-24 深圳市华芯国际技术开发有限公司 加速度传感器

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4676103A (en) * 1985-12-12 1987-06-30 Diesel Kiki Co., Ltd. Acceleration or inclination sensors
DE3919190A1 (de) * 1989-06-13 1990-12-20 Vdo Schindling Beschleunigungssensor
DE4222472C2 (de) * 1992-07-09 1998-07-02 Bosch Gmbh Robert Beschleunigungssensor

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9801761A2 *

Also Published As

Publication number Publication date
WO1998001761A3 (fr) 1998-04-09
KR19990044488A (ko) 1999-06-25
EP0848823A3 (fr) 1999-05-06
JPH11513118A (ja) 1999-11-09
WO1998001761A2 (fr) 1998-01-15

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