Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H1/00—Contacts
  • H01H1/0036—Switches making use of microelectromechanical systems [MEMS]
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H59/00—Electrostatic relays; Electro-adhesion relays
  • H01H59/0009—Electrostatic relays; Electro-adhesion relays making use of micromechanics
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H1/00—Contacts
  • H01H1/0036—Switches making use of microelectromechanical systems [MEMS]
  • H01H2001/0042—Bistable switches, i.e. having two stable positions requiring only actuating energy for switching between them, e.g. with snap membrane or by permanent magnet

Definitions

• the invention relates to a micro-mechanical switch, comprising a deformable suspension bridge, attached by support means to a substrate, and actuation means intended, from a first stable position of the switch, to deform the suspension bridge. deformable so as to establish an electrical contact between at least a first conductive element formed on the substrate, between the bridge and the substrate, and a second conductive element, integral with a lower face of the bridge.
• a micro-mechanical switch typically comprises a deformable suspended bridge 1 attached by means 2 of support to a substrate 3.
• Actuators allow the suspension bridge to be deformed, so as to establish electrical contact between first elements 5 conductors formed on the substrate 3 and a second element 6 conductor, integral with a lower face of the bridge 1.
• the actuators are, for example, constituted by electrodes 4a and 4b formed respectively on the bridge 1 and on the substrate 3 and between which an electric control voltage is applied.
• the first conductive elements 5 are, for example, constituted by two sections of a radiofrequency line which are connected by the second conductive element 6.
• the bridge 1 When the actuating means 4 are interrupted (cancellation of the control voltage), the bridge 1 returns in its non-deformed state, that is to say its stable position, and the electrical contact is interrupted. In order to maintain electrical contact, it is then necessary to continue actuation, which can increase the electrical consumption of the switch. Furthermore, if there is a problem with the control (or with the voltage), the electrical contact is no longer ensured.
• a conventional domestic switch has two stable positions and the electrical contact remains respectively established or interrupted without permanent energy supply.
• it is complicated to fabricate an analog, bistable, microscopic size switch.
• a first conductive element is constituted by a drop of mercury, which is moved by means of electrostatic forces to establish or interrupt an electrical contact between two solid conductive elements.
• mercury is very toxic and, on the other hand, the drop moves with the slightest movement of the switch which can cause unexpected switching.
• the document US2002 / 191897 describes a switch comprising a switching beam connected at its ends by supports fixed on a substrate.
• the switch has a first stable position corresponding to an open position of the switch.
• the switching beams are actuated by switching electrodes, so as to deform the switching beam to move the switch to a second position corresponding to the closed position of the switch. To maintain contact in this second position, it is necessary to keep the switching electrodes energized.
• the switch also comprises reconfiguration beams arranged at the periphery of the switching beam, of a single side of it or on either side of it.
• the reconfiguration beams are fixed to the substrate via rigid supports.
• the switch also includes actuating elements cooperating with the reconfiguration beams and intended to deform them independently of the switching beam.
• the deformation of the reconfiguration beam causes an increase in the distance between the switching beam and the electrode.
• the deformation of the reconfiguration beams leads to the appearance of restoring forces, inside the switching beam, representative of the spring constants of the switch.
• the object of the invention is to remedy these drawbacks and, in particular, to produce a microscopic switch having two mechanically stable positions.
• the support means are constituted by two feet arranged between the bridge and the substrate so as to subdivide the bridge transversely into a median segment disposed between the feet and two peripheral segments projecting outwards and comprising free ends, the actuating means comprising peripheral actuating means and median actuating means making it possible to independently deform the peripheral segments and the median segment respectively perpendicularly to the substrate.
• the switch being in the first stable position, in a first phase, the middle segment and the peripheral segments are simultaneously bent in the direction of the substrate, by means of their respective actuation means, so as to establish electrical contact, then, the peripheral actuation means are interrupted in a second phase, so as to automatically cause the separation of the peripheral segments with respect to to the substrate, the median actuation means being interrupted in a third phase, the median segment being thus automatically maintained in the bent position, so as to define a second stable position of the switch, in which the electrical contact remains established.
• the object of the invention is also a method of producing a micro-mechanical switch according to the invention, characterized in that the manufacture of the deformable suspension bridge on the substrate comprises: the deposition of a peripheral sacrificial layer on the substrate, on each side of the first conductive element, the deposition of at least one peripheral insulating layer on each peripheral sacrificial layer, so as to cover the front faces and the lateral faces of the two peripheral sacrificial layers to form the peripheral segments and the feet, deposition of a middle sacrificial layer, between the peripheral insulating layers, coming into contact with the lateral faces adjacent to the two peripheral insulating layers and covering the first conductive element, the deposition, on the middle sacrificial layer, of a middle insulating layer coming into contact with each of the front faces of the two peripheral insulating layers to form the middle segment, the etching of the lateral peripheral faces of the two peripheral insulating layers, so as to delimit the peripheral segments, the removal of the sacrificial layers.
• Figure 1 shows a micro-mechanical switch according to the prior art.
• Figures 2 and 3 show two particular embodiments of a micro-mechanical switch according to the invention.
• FIGS 4 to 7, on the one hand, and 8 and 9, on the other hand, illustrate schematically respectively the different phases of the establishment and the interruption of an electrical contact of a micro-mechanical switch according to l 'invention.
• Figures 10 to 15 illustrate a method of producing a micromechanical switch according to the invention.
• FIG. 16 represents a variant of a micro-mechanical switch manufactured according to the production method illustrated in FIGS. 10 to 15. Description of particular embodiments
• the micro-mechanical switch shown in FIG. 2 comprises a deformable suspended bridge 1, attached to a substrate 3 by two feet 7 arranged between the bridge 1 and the substrate 3 so as to subdivide the bridge 1 transversely into a median segment 8 disposed between the two feet 7, and two peripheral segments 9 projecting outwards.
• Two central electrostatic actuators 10 and two peripheral electrostatic actuators 11 make it possible to deform, independently, respectively the middle segment 8 and the peripheral segments 9 substantially perpendicular to the substrate.
• the actuators 10 and 11 are constituted by electrodes formed respectively on the substrate 3 and on the middle segments 8 or peripheral 9.
• the actuators 10 and 11 allow the bridge 1 to be deformed so as to establish electrical contact between a first conductive element 5 formed on the substrate 3, between the bridge 1 and the substrate 3, and a second conductive element 6, integral with the underside of bridge 1.
• the peripheral actuators 10 are also in the rest position and the switch is in a first stable position. While in FIG. 2, the middle segment 8 and the peripheral segments 9 are formed by a single layer, in FIG. 3, a first curved layer 13 respectively forms a foot 7 and the associated peripheral segment 9, so that the feet 7 are inclined relative to the substrate 3 and that the segments peripherals 9 have free ends 15 inclined away from the substrate 3. In FIG. 3, the middle segment 8 consists of a second curved layer 14 and thus comprises a slightly raised central part 12. The actuators 10 and 11 are respectively integrated in the middle and peripheral segments.
• the switch can switch from its first stable position, corresponding to the interruption of the electrical contact ( Figures 2 and 3), to a second stable position, corresponding to an established electrical contact.
• Figures 4 to 7 schematically illustrate the transition from the first stable position to the second stable position.
• the switch is shown in the first stable position, the actuators being at rest, the central part 12 of the middle segment 8 being raised and the peripheral segments 9 being inclined away from the substrate 3.
• Localized constraints ⁇ at the peripheral segments represented by horizontal arrows in the figures, exert a compressive force on the median segment 8 in its longitudinal direction and thus prevent the median segment from leaving its raised position.
• a first phase represented in FIG.
• the middle segment 8 and the peripheral segments 9 are simultaneously flexed in the direction of the substrate 3, respectively by means of the middle and peripheral actuators 10.
• the actuation of the peripheral actuators 11 causes stresses ⁇ exerting a tension force on the median segment 8 in its longitudinal direction (FIG. 5).
• the peripheral actuators 11 are interrupted in a second phase, represented in FIG. 6. This automatically causes the spacing of the peripheral segments 9 relative to the substrate 3 and, in this final position of the second phase, compressive stresses ⁇ on the median segment 8 in its longitudinal direction (FIG. 6).
• the middle actuators 10 are interrupted in a third phase.
• the middle segment 8 is then automatically maintained in the bent position by compressive stresses ⁇ effected by the peripheral segments 9, thus defining a second stable position of the switch, shown in FIG. 7, in which the electrical contact remains established.
• the three successive actuation phases allow the switch to pass from its first stable position (FIG. 4) to its second stable position (FIG. 7).
• FIG. 8 illustrates the return from the second stable position to the first stable position of the switch.
• the peripheral segments 9 are again bent in the direction of the substrate 3, by means of the peripheral actuators 11.
• a mechanical stress ⁇ in tension is exerted on the median segment 8 in its longitudinal direction, moving its central part 12 away from the substrate 3.
• the peripheral actuators 11 are then interrupted in a fifth phase, represented in FIG. 9, to return the switch to its first stable position, in which the peripheral segments 9 are inclined away from the substrate 3.
• the peripheral segments 9 are in substantially the same position (away from the substrate) in the two stable positions of the switch (FIGS. 4, 7 and 9) and change position only temporarily (FIGS. 5 and 8) during the actuation of the switch.
• the switch having two stable positions, the first position in which the electrical contact is interrupted, and the second position in which the electrical contact is established, only the passage from one position to the other consumes energy and the switch can, after actuation, remain in each of these positions without additional energy supply.
• Figures 10 to 15 illustrate a method of producing a micromechanical switch according to the invention. For reasons of clarity, the steps of manufacturing the electrodes constituting the actuators 10 and 11 are not shown.
• the manufacture of the deformable suspended bridge 1 on the substrate 3 then comprises at least the following steps.
• a peripheral sacrificial layer 16 is deposited on each side of the first conductive element 5 disposed on the substrate 3.
• at least one insulating layer 17 peripheral is deposited on each sacrificial layer 16 peripheral.
• the peripheral insulating layers 17 cover the front faces and the lateral faces of the two sacrificial layers 16 peripheral.
• a middle sacrificial layer 18 is deposited between the peripheral insulating layers 17. It comes into contact with the adjacent lateral faces of the two peripheral insulating layers 17 and covers the first conductive element 5.
• the fourth step consists in depositing on the middle sacrificial layer 18 an insulating middle layer 19. The latter comes into contact with each of the front faces of the two peripheral insulating layers 17, which it can partially cover, to form the middle segment 8 (FIG. 13).
• a fifth step (FIG.
• the peripheral insulating layer 17 can be a layer capable of creating a compressive stress on the median segment 8 in the longitudinal direction of the median segment 8 by a mechanical torque effect at the peripheral segments 9.
• the peripheral insulating layer 17 can be deposited using a method fixing a state of stress of the peripheral insulating layer 17.
• a method of the "dual frequency plasma deposition" type for example, it is possible to obtain a single layer which has a stress gradient.
• the desired level of stress can be obtained by adapting the thickness of the deposited layer. It is also possible to deposit several peripheral insulating layers 17 on each sacrificial sacrificial layer 16 in order to produce a stress gradient compressing the middle segment 8 in its longitudinal direction.
• a stack of two layers can, for example, be produced by an unconstrained layer deposited on a compression layer, by a tension layer deposited on an unconstrained layer or by a tension layer deposited on a compression layer.
• a stack of three layers can, for example, consist of two tension layers deposited on a compression layer or by a tension layer deposited on an unconstrained layer deposited, itself, on a compression layer. We thus obtain a spring type effect.
• the middle insulating layer 19 covers the front faces of the peripheral insulating layers 17 over their entire length, which amplifies the stresses between the two layers 17 and 19.
• the free ends 15 of the peripheral segments 9 and the central part 12 of the middle segment 8 are raised automatically away from the substrate.
• the electrodes of the peripheral electrostatic actuators 11 are disposed respectively between each peripheral insulating layer 17 and the associated middle insulating layer 19.
• peripheral insulating layers 17 each cover a part 20 of the front face of the substrate 3 disposed respectively between the lateral face of a sacrificial layer 16 peripheral and the first conductive element 5.
• the actuators 10 and 11 can be constituted by any type of actuator, namely by piezoelectric, thermal, magnetic actuators, etc.
• the peripheral electrodes are, preferably, wider, by example of a factor three, that the median electrodes, in a plane parallel to the substrate 3, which makes it possible to reduce the piloting voltage of the peripheral actuators.
• a switch according to the invention can be used in a matrix of switches or as a simple switch. Such a switch can typically be used in telecommunications applications, in particular for radiofrequency, terrestrial and space devices, in biomedical applications, relays, etc.

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• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Micromachines (AREA)
• Push-Button Switches (AREA)
• Hydrogenated Pyridines (AREA)

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• 2003
  • 2003-08-01 FR FR0309534A patent/FR2858459B1/fr not_active Expired - Fee Related
• 2004
  • 2004-07-26 WO PCT/FR2004/001988 patent/WO2005015594A2/fr active IP Right Grant
  • 2004-07-26 US US10/564,801 patent/US7342472B2/en not_active Expired - Fee Related
  • 2004-07-26 AT AT04767777T patent/ATE371948T1/de not_active IP Right Cessation
  • 2004-07-26 DE DE602004008648T patent/DE602004008648T2/de not_active Expired - Lifetime
  • 2004-07-26 EP EP04767777A patent/EP1652205B1/de not_active Expired - Lifetime
  • 2004-07-26 JP JP2006522366A patent/JP4481309B2/ja not_active Expired - Fee Related

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