EP0776475A1 - Transducteur - Google Patents

Transducteur

Info

Publication number
EP0776475A1
EP0776475A1 EP95928591A EP95928591A EP0776475A1 EP 0776475 A1 EP0776475 A1 EP 0776475A1 EP 95928591 A EP95928591 A EP 95928591A EP 95928591 A EP95928591 A EP 95928591A EP 0776475 A1 EP0776475 A1 EP 0776475A1
Authority
EP
European Patent Office
Prior art keywords
transducer
mass
seismic mass
deflection
force
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Withdrawn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
EP95928591A
Other languages
German (de)
English (en)
Inventor
John Neville Fawcett
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.)
BTG International Ltd
Original Assignee
BTG International Ltd
British Technology Group Ltd
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 BTG International Ltd, British Technology Group Ltd filed Critical BTG International Ltd
Publication of EP0776475A1 publication Critical patent/EP0776475A1/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Withdrawn legal-status Critical Current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
    • 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
    • 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
    • G01P15/0802—Details
    • 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
    • G01P15/13—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 measuring the force required to restore a proofmass subjected to inertial forces to a null position
    • G01P15/131—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 measuring the force required to restore a proofmass subjected to inertial forces to a null position with electrostatic counterbalancing means
    • 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

Definitions

  • This invention relates to a transducer for use in an accelerometer or other force transducer and in particular to a micro-accelerometer fabricated as a chip from a semiconductor material wafer using manufacturing techniques analogous to those of integrated circuits.
  • micro-accelerometers find applications in the motor and aerospace industries as inputs for control systems; in the motor industry the uses include triggering air bags and as inputs to suspension systems.
  • Micro-accelerometers can be single axis devices, sensitive in a single direction, which are then assembled to form a three dimensional unit.
  • Accelerometers may have to survive over-shocks of hundreds of times their normal operating range and usually employ deflection stops incorporated into the structure to prevent damage. Accelerometers built from single-crystal semiconductor material exhibit very low mechanical loss and need to have controlled damping in order to ensure high- fidelity transduction of acceleration.
  • Accelerometer systems with Self-Testable Features by Allen, Terry and De Bruin, Sensors and Actuators, 20 (1989) 153-161, incorporated herein by reference, a single axis accelerometer having a double cantilever structure is disclosed. Such a device has a seismic mass supported through four silicon springs and the mass can move in a pure translational mode as shown in Figure la.
  • EP 322093 A discloses a deflectable seismic mass constructed from a single wafer of silicon.
  • the mass moves rectilinearly in response to a force applied perpendicularly to the surface of the wafer.
  • All of the embodiments disclosed show masses in which movement in the ⁇ 1,1,1, ⁇ plane is constrained and which deflect in a plane perpendicular to the ⁇ 1,1,1 ⁇ plane and the surface of the wafer (the ⁇ 1,0,0 ⁇ silicon plane).
  • the mass when subjected to a force which is not perpendicular the ⁇ 1,0,0, ⁇ silicon plane, tends to move and rock through the deflectable plane.
  • the mass of figure 5 of EP 322093 is constrained to rotate about a line parallel to the ⁇ 1,1,1 ⁇ silicon plane, positioned at the intersection of the planes defined by flexible members 24" and 26".
  • the devices disclosed are also unsuitable for use in a flat, single wafer device which is sensitive in all three dimensions. As before, a lack of symmetry in the mass will cause unwanted rotational movements.
  • a transducer comprising a deflectable seismic mass supported on a frame by support means, said seismic mass at rest including a plane, characterised in that the seismic mass when deflected by any force retains the plane substantially parallel to the rest position.
  • a transducer comprising a deflectable seismic mass supported on a frame by support means characterised in that any deflection of the seismic mass is purely translational.
  • a third aspect of the invention there is provided a method of manufacturing a transducer according to the first or second aspect.
  • a single axis accelerometer including a force transducer according to the first or second aspect.
  • a three dimensional accelerometer including a force transducer according to the first or second aspect.
  • the invention also allows three identical structures to be etched onto a flat semiconductor wafer and yet can be used to determine accelerations in three perpendicular directions.
  • the structures deflect such that the surfaces of their seismic masses always remain parallel to the wafer surface. This enables measurement of the deflection to be made easily, for example by depositing electrodes on the surfaces of the seismic masses and fixed surfaces (such as deflection stops) and measuring the change in capacitance between the electrodes.
  • Cross coupling effects will be negligible since each transducer is stiff in all directions except the sensitive direction.
  • etching and/or doping techniques may be employed to micromachine the transducer . It may also be possible to include the measuring means on the same wafer as the transducer. Embodiments of the invention are described in detail below, by way of example only, with reference to the figures in which,
  • Figure 1 illustrates the three modes of motion of the prior art
  • Figure 2 shows a first embodiment of the invention
  • Figure 3 shows a process for etching the first embodiment
  • Figure 4 shows a suitable configuration for the first embodiment
  • Figure 5 shows a second embodiment of the invention
  • Figure 6 shows a suitable configuration for the second embodiment
  • Figure 7 shows an alternative arrangement for the second embodiment
  • Figure 8 shows an arrangement for measuring the deflection of the seismic mass
  • Figure 9 shows an alternative arrangement for measuring the deflection of the mass
  • Figure 10 shows a null arrangement for measuring the deflection of the mass
  • Figure 11 shows a null construction for the first embodiment of the invention
  • Figure 12 shows the orientation of three transducers in a three dimensional structure.
  • Figure 2 shows a first embodiment of the invention employing a quad bridge structure.
  • the transducer consists of a seismic mass 10 supported on a frame 11 by four flexible support elements 12.
  • the flexible support elements consist of thin parallel beams formed at an angle ⁇ to the surface of the mass.
  • the device Taking the three perpendicular axes Ox, Oy and Oz, with the Ox axis parallel to the longitudinal axis of the beams and Oz perpendicular to the face of the beams, the device is stiff in the Ox and Oy directions but will, when subjected to a force, deflect in the Oz direction.
  • the deflection of the mass, or the force required to maintain a null position, can be used as a measure of the acceleration of the mass.
  • FIG. 3a shows a section through a silicon slice or wafer 15 the upper surface of which has been masked, by a mask 16, over some of its area.
  • the cavity formed When etched through the mask the cavity formed always has flat walls which lie at an angle ⁇ to the surface of the slice. In (1,0,0) silicon this angle is 54.7° and the walls 17 formed correspond to (1,1,1) surfaces.
  • Figure 3 b illustrates that by etching similar cavities in the underside of the silicon slice, with appropriate masking, by a mask 18, and timing of the etching process, it is possible to produce thin beams 19 suitable for use in the transducer.
  • the walls 17 may be doped, for example with boron.
  • the doped areas are impervious to etchant and will remain after the etching process is complete. It would be possible to etch both sides simultaneously, or to etch sequentially.
  • Figure 4 shows a suitable configuration, with figure 4a , 4b, 4c and 4d showing the respective cross sections A-A, B-B, C-C and D-D. Variations in the detailed shape of the seismic mass 10, the frame 11 and the support elements 12 will depend on the type of mask and etching process used. The sensitive direction is shown by the arrow 20.
  • Figure 5 shows an second embodiment in which the four support elements are replaced by two support beams 30 attaching the seismic mass 10 to the frame 1 1.
  • the device Taking the three perpendicular axes Ox, Oy and Oz, with the Ox axis in the plane of the mass and parallel to the plane of the and Oz perpendicular to the plane of the beam, the device is stiff in the Ox and Oy directions but will, when subjected to a force, deflect in the Oz direction.
  • the deflection of the mass, or the force required to maintain a null position can be used as a measure of the acceleration of the mass.
  • Figure 6 shows a suitable configuration, with figures 6a and 6b showing the respective cross sections A-A and B-B.
  • Figure 8 shows a cross section of the mass 10, between an upper deflection stop 40 and a lower deflection stop 41. Pairs of electrodes 42,43 may be deposited directly onto the mass and the fixed surfaces of the deflection stops to form a push-pull capacitor. Since both the upper and lower surfaces of the mass remain parallel to the fixed surfaces of the deflection stops, the change in the capacitance between the electrodes on the fixed surfaces and the electrodes on the movable surfaces will be a direct measure of the amount of deflection of the mass, and thus the acceleration.
  • Figure 9 shows an alternative arrangement which avoids the need for supplying an electrical connection to the mass.
  • a pair of electrodes 42,43 is deposited on the upper deflection stop 40 and the lower deflection stop 41.
  • a conducting layer 44 is deposited on the upper and lower surfaces of the mass 10. Electrodes 42,44 and 43,44 form two capacitors in series at each of the upper and lower gaps. As with the previous arrangement, the change in the capacitance will be a direct measure of the amount of deflection of the mass, and thus the acceleration.
  • Figure 10 shows a null arrangement whereby the deflection of the mass is counteracted.
  • a conducting layer 44 is deposited on a surface of the mass 10 adjacent to a deflection stop (not shown). Pairs of electrodes 42,43 are deposited on the deflection stop and as with the arrangement illustrated in figure 8, the change in the capacitance will be a direct measure of the amount of deflection of the mass, and thus the acceleration.
  • Two actuators 45,46, also deposited on the deflection stop, are used the counteract the deflection of the mass by means of suitable voltages applied to electrodes 45 and 46.
  • figure 11 shows an null arrangement for the first embodiment illustrated in figure 2 and consists of a seismic mass 10 supported on a frame 11 by four flexible support elements 12.
  • Two thin null beams 50 prevent movement of the mass; any force applied on the mass in the sensitive direction (marked by arrow 20) will apply a tensile load to one beam and a compressive load to the other beam. If the beams are caused to vibrate at their natural frequencies of transverse vibration, these natural frequencies will change as the tensile and compressive loads change. The differences in the natural frequencies of these beams is proportional to the acceleration of the mass.
  • Figure 12 shows a three dimensional layout where three of the single axis devices can be produced on a single wafer of silicon.
  • the properties of (1,0,0) silicon are such that it is possible to produce two or more identical transducers which are rotated, about an axis normal to the wafer (OY), by 90° intervals relative to the first device.
  • O ⁇ zi O2Z2 and O3Z3 are the sensitive directions for each transducer. If the acceleration components measured along OjZ], O2Z2 and O3Z3 are aj, a2 and a.$- respectively, the accelerations A along the three perpendicular axes Ox, Oy and Oz are

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Pressure Sensors (AREA)
  • Micromachines (AREA)

Abstract

On décrit un capteur de forces où une masse sismique pouvant être infléchie prend appui sur un cadre par l'intermédiaire d'un support. La masse sismique au repos comprend un plan et, lorsqu'elle est infléchie par une force quelle qu'elle soit, maintient toujours ce plan parallèle à celui de sa position de repos. Toute inflexion de cette masse sismique constitue un mouvement purement translationnel du point de vue topographique, aucun mouvement tournant n'étant possible. L'invention permet de graver sur une plaquette en semiconducteur trois structures identiques qu'on peut cependant utiliser pour déterminer des accélérations se produisant dans trois directions perpendiculaires. Quand ces structures s'infléchissent, les surfaces de leurs masses sismiques restent toujours parallèles à la surface de la plaquette. Cela facilite la mesure de l'inflexion, par exemple par dépôt des électrodes sur les surfaces des masses sismiques et sur des surfaces fixes (telles que des butoirs d'inflexion) et par mesure des changements de capacitance entre ces électrodes. Les effets des couplages parasites sont négligeables car chaque transducteur est rigide dans toutes les directions sauf celle de la détection.
EP95928591A 1994-08-18 1995-08-18 Transducteur Withdrawn EP0776475A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB9416683 1994-08-18
GB9416683A GB9416683D0 (en) 1994-08-18 1994-08-18 Accelerometer
PCT/GB1995/001966 WO1996006358A1 (fr) 1994-08-18 1995-08-18 Transducteur

Publications (1)

Publication Number Publication Date
EP0776475A1 true EP0776475A1 (fr) 1997-06-04

Family

ID=10760018

Family Applications (1)

Application Number Title Priority Date Filing Date
EP95928591A Withdrawn EP0776475A1 (fr) 1994-08-18 1995-08-18 Transducteur

Country Status (6)

Country Link
EP (1) EP0776475A1 (fr)
JP (1) JPH10504649A (fr)
KR (1) KR970705755A (fr)
GB (2) GB9416683D0 (fr)
TW (1) TW297909B (fr)
WO (1) WO1996006358A1 (fr)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19506401A1 (de) * 1995-02-23 1996-08-29 Siemens Ag Beschleunigungssensor
SE9800194D0 (sv) * 1998-01-23 1998-01-23 Gert Andersson Anordning för mätning av vinkelhastighet
FR2810976B1 (fr) * 2000-06-29 2003-08-29 Planhead Silmag P H S Microcomposant electronique, capteur et actionneur incorporant un tel microcomposant
GB2498520A (en) * 2012-01-13 2013-07-24 Secr Defence Accelerometer
JP6893179B2 (ja) * 2015-06-11 2021-06-23 ジョージア テック リサーチ コーポレイション 直交同調ための傾斜電極を有するｍｅｍｓ慣性測定装置
CN114323395B (zh) * 2021-12-23 2022-11-11 西安交通大学 一种基于soi工艺的mems六轴力传感器芯片及其制备方法

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5000817A (en) * 1984-10-24 1991-03-19 Aine Harry E Batch method of making miniature structures assembled in wafer form
US4922756A (en) * 1988-06-20 1990-05-08 Triton Technologies, Inc. Micro-machined accelerometer
GB8718004D0 (en) * 1987-07-29 1987-12-16 Marconi Co Ltd Accelerometer
US4812199A (en) * 1987-12-21 1989-03-14 Ford Motor Company Rectilinearly deflectable element fabricated from a single wafer
US4879914A (en) * 1989-02-27 1989-11-14 Sundstrand Data Control, Inc. Unitary push-pull force transducer
US4919993A (en) * 1989-02-27 1990-04-24 Sundstrand Data Control, Inc. Flexures and method for creating flexures in a wafer
US5045152A (en) * 1989-03-06 1991-09-03 Ford Motor Company Force transducer etched from silicon
SE500615C2 (sv) * 1992-12-03 1994-07-25 Gert Andersson Anordning för mätning av kraftkomponenter, förfarande för framställning av dylik samt användning därav.

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9606358A1 *

Also Published As

Publication number Publication date
KR970705755A (ko) 1997-10-09
GB9516992D0 (en) 1995-10-18
WO1996006358A1 (fr) 1996-02-29
GB2292462A (en) 1996-02-21
TW297909B (fr) 1997-02-11
GB9416683D0 (en) 1994-10-19
JPH10504649A (ja) 1998-05-06

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