Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H57/00—Electrostrictive relays; Piezoelectric relays
• • 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
  • 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
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H57/00—Electrostrictive relays; Piezoelectric relays
  • H01H2057/006—Micromechanical piezoelectric relay
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H67/00—Electrically-operated selector switches
  • H01H67/22—Switches without multi-position wipers

Definitions

• the air knife capacitor thus formed has a capacity
• the force F is related to the tension applied by the following equation
• the subject of the invention is a switching device comprising at least one membrane made of material M-
• the means for switching from a state 0 to a state 1 comprise a piezoelectric layer deposited on the surface of the membrane, so as to constitute a bimetal system having two stable states 0 and 1
• the substrate can advantageously be made of silicon
• the membrane can advantageously be made of material constrained with respect to silicon, of the silica or silicon nitride type Indeed it is known to use deposition conditions, such as the material M
• the invention also relates to a display device associating a conventional matrix type liquid crystal matrix, the optical state of the pixels of which is electrically controllable and a matrix of elementary switching devices such as those described above.
• Each pixel of the active matrix is opposite the upper electrode for controlling the piezoelectric material of an elementary switching device
• FIG. 1 illustrates a switching device according to the known art, using a bimetal system
• FIG. 2 illustrates a switching device according to the invention
• FIG. 3 illustrates the piezoelectric means for controlling a switching device according to the invention
• FIG. 4 illustrates the characteristic parameters of the deformation of a pre-stressed membrane of a switching device of the invention
• FIG. 5 illustrates a top view of a switching device according to the invention, in which the membrane has openings to partially release the membrane from the substrate,
• FIG. 6 illustrates the association of a liquid crystal matrix display device and a matrix of electrical switches according to the invention, making it possible to control said device
• FIG. 7 illustrates a top view of the set of electrodes 15 ,, and 16 ,, allowing the addressing of the switches used to address a matrix of liquid crystal pixels
• the device comprises means which can advantageously be of the piezoelectric type, the transition from a stable state to another stable state being achieved in this case by a simple pulse.
• FIG. 2 illustrates such a switching device.
• a membrane 11 made of material M- ⁇ is supported by a substrate 12 made of material M2.
• This membrane is shown convex corresponding to the state known as 0, shown in solid lines and denoted 11 Q but by construction. as will be explained later, it can equally be concave and correspond to state 1 (shown in dotted lines and denoted 111)
• the membrane comprises a piezoelectric device consisting of a layer of piezoelectric material 14 inserted between electrodes 15 and 16
• the piezoelectric device is thin in front of the membrane and does little to modify the behavior of the material M-- with respect to the material M2, as illustrated in FIG. 3
• FIG. 4 illustrates the curvature of the membrane 1 1 in the presence of pre-stresses as well as the different parameters d, dg, o and hg 2 ho being representative of the difference between the convex state 0 and the concave state 1
• a layer of thermal silica is created on both sides by annealing at 950 ° C. in the presence of water vapor or at 1050 ° C. under dry oxygen.
• microlithography it is etched with HF acid or a reactive plasma, all the silica on the front face and part of that on the rear face making it possible to produce a rectangular mask later used for chemical or electronic machining of silicon.
• a lower electrode 15 is deposited for the piezoelectric device, for example made of platinum, and this is done through a resin mask which is then removed by conventional microlithography methods.
• the layer of piezoelectric material 14 is deposited by cent ⁇ fugation or any other technique of depositing in thin layers, a layer of PZT (lead titano-zirconate), which is then etched with acid type HF diluted (having protected the back side with resin)
• the PZT is crystallized and densified by rapid annealing at a temperature between 600 and 700 ° C for a short time, of the order of 2 minutes, so that the stress of the underlying layer cannot relax. finally deposits an upper electrode 16 similar to the lower electrode
• the silica membrane is thus released, to relax and take the curved shape illustrated in FIG. 2, (concave or convex shape), carrying with it the piezoelectric capacitor previously formed.
• the embodiment has been described for a switching device comprising a membrane
• the switching device comprises a matrix of elementary switches, produced collectively using all the process steps described above using suitable microlithography masks
• This type of switch matrix can advantageously be used in visualization by being coupled to a display device, of the liquid crystal matrix type, plasma screen, light-emitting diodes.
• FIG. 6 illustrates an example of a display device using a switching device according to the invention
• the display device comprises a matrix of pixels PXLIJ, comprising a common electrode 19 called the upper electrode, each pixel also comprising a electrode 20 ⁇ j called the lower
• the switching device comprises elementary membranes 11,., Supported by a substrate Each membrane 11 , is covered with an electrode 15, j , called the lower electrode, with a layer of piezoelectric material 14 , and with an electrode called superior 16 ,.
• an electrode 15, j called the lower electrode
• a layer of piezoelectric material 14 a layer of piezoelectric material 14
• an electrode called superior 16 an electrode called superior 16 .
• HERE represented a liquid crystal matrix
• FIG. 7 illustrates a top view of the assembly of the lower electrodes 15, and upper 16,. located on either side of the piezoelectric layers

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• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Micromachines (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=9495721

Family Applications (1)

Country Status (4)

Families Citing this family (7)

Family Cites Families (4)

• 1996
  • 1996-09-13 FR FR9611199A patent/FR2753565B1/fr not_active Expired - Fee Related
• 1997
  • 1997-09-12 JP JP10513325A patent/JP2000502496A/ja active Pending
  • 1997-09-12 EP EP97919091A patent/EP0861496A1/de not_active Ceased
  • 1997-09-12 WO PCT/FR1997/001616 patent/WO1998011586A1/fr not_active Application Discontinuation

Non-Patent Citations (1)

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