Classifications

• • 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]
  • H01H2001/0084—Switches making use of microelectromechanical systems [MEMS] with perpendicular movement of the movable contact relative to the substrate
• • 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
  • H01H2059/0081—Electrostatic relays; Electro-adhesion relays making use of micromechanics with a tapered air-gap between fixed and movable electrodes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H59/00—Electrostatic relays; Electro-adhesion relays
  • H01H2059/009—Electrostatic relays; Electro-adhesion relays using permanently polarised dielectric layers

Definitions

• the invention relates to a micromechanical electrostatic relay
• a flexible anchor tongue made of solid material, which is connected on one side to the base substrate and forms a wedge-shaped working air gap which widens towards the open end,
• an armature electrode formed on the armature tongue and opposite the base electrode
• At least one fixed contact arranged on the base substrate
• At least one movable contact arranged on the anchor tongue and opposite the fixed contact.
• Such a micromechanical relay is basically already described in DE 42 05 029 Cl. Due to the wedge-shaped air gap between the base electrode and the armature electrode, when the voltage is applied between the two electrodes, the armature tongue rolls off on the base electrode, causing the narrow distance between the two electrodes to move further from the clamping point to the free, contacting end (traveling wedge principle) . In this way it is possible, on the one hand, to ensure the insulation strength between the fixed contact and the moving contact in the open state with a sufficient contact spacing, and on the other hand to make the armature respond electrostatically with a relatively low switching capacity.
• relatively high switching voltages are required; in addition, the contact forces that can be achieved are still relatively low. 2
• normally closed contacts or changeover contacts are very difficult to implement.
• an electrostatic relay is also already known, in which a movable tongue can be switched between two stationary electrodes and the stationary electrodes are additionally provided with electrets.
• the stationary electrodes are arranged parallel to each other there at a relatively large distance from the movable tongue, so that in the respective switching positions they can only contact the counter electrodes at an acute angle and can only touch them in a point-like or linear manner.
• the electret layers also only extend over part of the length of the movable armature tongue, whereby a flat contact with it does not appear possible.
• the aim of the present invention is to develop an electrostatic relay of the type mentioned at the outset such that an improved switching behavior with a desired step switching characteristic and with sufficiently high contact forces is achieved with relatively low switching voltages. It should be possible to set a desired switching characteristic, such as break contacts, make contacts and changeover contacts.
• a relay for achieving this goal has the structure mentioned at the outset and, moreover, at least one electret layer arranged on the base substrate or the anchor tongue and incorporated into the surface of the wedge-shaped working air gap.
• the switching characteristics of the relay can be adjusted very well to the respective application. Since the electret layer extends into the tip of the wedge-shaped air gap, the electrical charges of the electret are 3 movement at the same time with the installations of the control voltage more ⁇ sam, so that the control voltage itself can be correspondingly lower. Depending on the intended electrical charge density of the electret layer, the characteristics of the relay can be selected differently. This charge density can thus be chosen so high that even without activation, the attraction force of the electret exceeds the mechanical pretensioning force of the anchor tongue, with which, due to its basic shape, it is pretensioned away from the base substrate.
• the anchor tongue therefore lies against the base substrate in the idle state. and an NC contact is formed. If, on the other hand, with a lower charge density this tightening force is less than the pre-tensioning force, a closer is created.
• the electret layer can optionally be arranged on the base substrate or the base electrode or on the armature tongue or the armature electrode.
• an additional cover substrate will be arranged above the base substrate in such a way that these two fixed substrates form a wedge-shaped air gap, in which the armature tongue is then pivotably arranged and can be placed either on the base electrode or on the cover electrode.
• an electret layer is provided on the base substrate and on the cover substrate, these electret layers carrying charges with different signs.
• the characteristic can be adjusted by coordinating the charge densities in both electret layers. If the charges have different signs in both
• Electret layers are equal in terms of their absolute values, ie their sum is zero, a bistable switching characteristic or, if appropriately fine-tuned, a tri-stable switching characteristic can be achieved in this way.
• monostable switching behavior can be achieved by different charge densities in the two electret layers. 4
• the air gap surface of the base substrate and, if appropriate, the cover substrate are each curved so that the greatest curvature occurs in the area of the clamping of the anchor tongue and that the distance between the base electrode and the anchor tongue or between the base electrode and the cover electrode from the clamping point of the anchor tongue to its free end is steadily increasing.
• Silicon or a crystalline material with similar properties is preferably used as the material for the base and lid substrates and for the anchor tongue.
• the electret layer preferably consists of silicon dioxide (Si0 2 ) or of a silicon dioxide / silicon nitrate (Si0 2 / Si 3 N 4 ) composite structure.
• the surface charge densities in the electret layers can be between 10 "4 and 10 " 3 , possibly also 10 "2 , C / m 2 .
• a method for producing one or more relays of the type mentioned at the outset is that in a crystalline base substrate, by removing the surface, a profile corresponding to the desired wedge-shaped air gap surface is generated and, by selective coating and structuring, at least one insulation layer, a metal layer for forming the Base electrode and at least one load circuit lead, an insulation layer provided with electrical charges as an electret layer and at least one contact piece are formed that on the underside of an armature substrate by selective coating and structuring at least one insulation layer, a metal layer to form an armature electrode and at least one movable contact element and a surface insulation layer is generated so that the armature substrate with its structured underside on the structured upper 5 side of the base substrate is bonded as well as to a desired armature ge ⁇ thickness removed, and that then the contour of the anchor tongue is exposed on three sides.
• Preference ⁇ as also a cover substrate is coated in an analogous manner as the base substrate and patterned and then bonded with its structured side to the armature substrate.
• the same or similar etching, coating, structuring and doping methods are used for the individual production steps of the relay, as are also used in semiconductor technology or in other ways in micromechanics.
• the curved profiles for the air gap surfaces of the base substrate and optionally of the cover substrate are preferably obtained by means of gray-tone lithography or sacrificial mask technology.
• Figures 1 to 4 different configurations of a closer or. Break relays in two switching states each in a schematic sectional view
• FIG. 5 shows a changer arrangement in a schematic sectional illustration
• FIG. 6 shows a section VI-VI from FIG. 5, 6
• FIG. 7 shows a view VII-VII from above of the base substrate from FIG. 5, with the contour of the anchor tongue indicated
• FIG. 8 shows a view from above of an embodiment of the anchor tongue with single contact
• FIG. 9 shows a view from above onto an anchor tongue with bridge contact ,
• FIGS. 10A to 10E show a schematic sectional illustration of a base substrate in different manufacturing process steps
• FIGS. 11A to 11H show a schematic sectional illustration of the manufacture of one (or two) anchor tongue (s) in several process steps, the connection to a base substrate and the application of an additional cover substrate
• Figure 12 is a perspective view of a multiple relay arrangement with a common base substrate, a plurality of contiguous anchor tongues and a common cover substrate and
• FIG. 13 to 15 different path-voltage characteristics for an inventive relay.
• FIGS. 1 to 4 show different embodiments of a simple NO / NC relay with an electret, in which only one base substrate 1 and one armature substrate 2 with an armature tongue 21 are provided.
• a wedge-shaped air gap 10 is formed between the base substrate 1 and the armature tongue 21, at the open end of which the base substrate 1 carries a fixed contact 5 and the armature tongue 21 carries a movable contact 6.
• both the base substrate 1 and the armature tongue 21 are designed as electrodes, between which a control voltage U s can be applied via corresponding connections.
• an electret layer 4 is provided on one of the air gap surfaces, that is to say an insulating layer with stationary electrical charges.
• the air gap 10 is defined by the basic shape of the base substrate and the armature tongue, where either according to Figu ⁇ ren 1A and 2A, the base substrate has a flat surface 11 has ⁇ and the anchor tongue is bent away from the plane up or according to the figures 3A and FIG. 4A the base substrate has a curved surface 12 and the anchor tongue has a flat basic shape.
• the electret layer 4 can be arranged either on the surface 11 of the base substrate 1 or on the surface of the armature tongue 21 facing the base substrate. Depending on the electrical charge density in the electret layer 4 in comparison to the mechanical pretensioning of the armature tongue 21 with respect to the base substrate, different switching characteristics result:
• FIGS. 1A, 2A, 3A and 4A each show a switching state with an open air gap 10, while FIGS. 1B, 2B, 3B and 4B show the state with a closed air gap, that is to say with the armature tongue 21 tightened. If one assumes that the charge density in the electret layer 4 is not sufficient to attract the armature tongue 21 without control voltage U s , it is a normally open relay. In this case, FIGS. 1A to 4A show the unexcited state with open contacts, while FIGS. 1B to 4B show the excited state after application of a control voltage U s . The application of the control voltage U s thus causes the circuit between contacts 5 and 6 to be closed.
• FIGS. 1B to 4B show the idle state with the contacts 5 and 6 closed.
• an opener relay must be used Contact opening a control voltage U s between base substrate 1 and armature tongue 21 are applied, the opposite polarity to the charge of the electret layer 4 and greater than this, so that the 8 of the electret pullout rating overcome and the contact ge ⁇ is open.
• FIGS. 1A to 4A show the energized state of the relay.
• the preferred embodiment of the inventive relay is however not the simple NO or ⁇ ff ⁇ nerrelais but the changeover relay, which is schematically shown in FIG. 5
• a lid substrate 3 is provided so that the wedge-shaped air gap 10 is formed between the base substrate and the lid substrate and the anchor tongue between these two substrates is included.
• the lid substrate 3 is preferably designed identically to the base substrate 1 and rotated by 180 ° and placed on top of it with the interposition of an armature substrate 2.
• the surfaces 11 of the base substrate and 31 of the cover substrate facing the air gap 10 are - as in the case of the previously described FIGS.
• the armature tongue 21 can either nestle against the surface of the cover substrate 3 or against the surface of the base substrate 1 (indicated by dots in FIG. 5).
• the substrates 1 and 3 with the appropriate doping could themselves function as a base or cover electrode; likewise, the armature substrate 2 or the armature tongue 21 could directly form the armature electrode.
• a base electrode 19 is preferably provided on the base surface, a cover electrode 39 on the cover surface and metallic anchor electrodes 28 and 29 on the respective surfaces of the armature tongue 21.
• the metal layers for forming the electrodes can then be formed by appropriate structures. 9 also form supply lines for the load circuit that are insulated from the electrodes.
• spacer webs 13 and 33 are formed on the respective electret layer 12 and 32, respectively, which do not carry any electrical charges and which extend in the longitudinal direction of the armature tongue 21.
• FIG. 7 shows such electret regions 7, which partially surround the region of the base electret layer 12 in the form of a frame.
• the base electret layer 12 has a region which surrounds the contact 15 in an approximately circular manner and does not carry any charges. This area is shown with a boundary line 14.
• the contour of the anchor tongue 21 with the contact area is shown in dashed lines in FIG. This special contour will be explained later.
• FIG. 7 accordingly shows three differently charged regions of the electret layer, namely the frame-like, highly charged electret regions 7, the actual electret layer 12 with a defined charge density between 10 "4 and 10 " 3 or 10 "2 C / m 2 and that of the approximately circular line 14 delimited contact area, which carries no surface charges.
• the contact system 10 of the change-over relay is according to FIG 5 comprises a base-fixed contact 15, a lid-fixed contact 16 and a movable center contact 17, the Ge on the Ankerzun ⁇ disposed 21st
• the anchor tongue 21 is shown in plan view in FIG.
• conductive regions are colored dark (which also conducting electrode layer of at ⁇ kerzunge not shown).
• the movable contact portion 28 is connected to the Mittelkon ⁇ clock 17 into one another cross-by spirally or sonnenradförmig slots 22 of movable bars 27 in the armature ⁇ tongue 21 is suspended, so that it consists in making contact respectively the plane of the anchor tongue can be moved out and in this way receives the desired contact force.
• Such an arrangement of an anchor tongue with a movably suspended contact has already been described in DE 44 37 259 Cl.
• the contact is connected via a conductor track 24 to a connection (not shown) in the area of the clamping point of the armature tongue 21.
• a torsion band suspension is shown in FIG. 9.
• a bridge contact 24 is suspended via torsion straps 25, which in turn are separated from the actual anchor tongue by appropriately designed slots 26.
• FIGS. 10 and 11 show the essential manufacturing steps for a relay according to FIG. 5.
• a longitudinal section through the respective substrate is shown, only the most important process steps being listed. For example, intermediate steps such as masking or application of additional layers that are necessary in terms of production technology with adhesion promoters, diffusion barriers, etc. are not considered. 11 received.
• Such process steps are known to those skilled in the processing of silicon wafers or similar substrates in semiconductor technology or in micromechanical process technology.
• FIG. 10A basically shows a section through a silicon substrate 100, which serves as a starting substrate for a base substrate 1 or a lid substrate 3.
• This substrate 100 is first removed on the surface in order to obtain the curved surface 101 required for the wedge-shaped working air gap.
• two mirror-inverted substrate systems are manufactured simultaneously for manufacturing reasons, namely an electrode surface 101A in the left half of the substrate and a mirrored electrode surface 101b in the right half of the substrate.
• This base electrode profile is preferably generated using gray-tone lithography;
• other processing methods would also be conceivable, such as sacrificial layer technology or other etching methods from semiconductor processing.
• the layers shown in FIG. IOC are applied in succession, namely an insulation layer 102, a metal layer 103, which is structured to form a drive electrode and, if appropriate, load circuit leads, and an insulation layer 104 for the electret surfaces, which is likewise structured accordingly .
• a further insulation layer 105 is then applied according to FIG. 10D and structured to form the spacer webs 13 and 33 (FIG. 5).
• fixed contact pieces 106 are formed on the metal layer 103 by galvanic amplification.
• the desired electret layers are formed by structured charging of the insulation layer 104 with electrical charges 107. For example, a potential of approximately ⁇ 10 to in the area of the actual electret layers 12 ⁇ 50 V, while a potential of approx. ⁇ 100 to ⁇ 300 V is generated in the outer suction area of the frame-shaped electret surfaces 7.
• armature substrate 200 is provided on the underside of the wafer with an insulation layer 201, and a metal layer 202 is applied to this insulation layer and structured to form an armature electrode and, if appropriate, load circuit leads.
• a further insulation layer 203 is then applied and structured, as shown in FIG. ILA. 11B, movable contacts 204 are formed on the metal layer 202 by galvanic amplification.
• the armature substrate 200 obtained and structured in this way is bonded anodically or eutectically or in another way to a base substrate 100 which is designed according to FIG. 10E (FIG. 11C). Then, according to FIG. HD, the armature substrate is etched down to a desired thickness of the armature tongue 21. Such a thickness is, for example, on the order of 10 ⁇ m.
• the anchor tongue layer 210 obtained in this way could, if only an opener or closer according to FIGS. 3 and 4 should be produced, be separated in the middle in the area 211, so that two anchor tongues 21, which are denoted in brackets and arranged in mirror-inverted fashion, would be obtained.
• the upper side of the armature tongue layer 210 is structured further, namely by applying a further insulation layer 205, by applying and structuring a metal layer 206 for a further drive electrode and optionally for load circuit leads, and by applying and structuring a further insulation layer 207 ( Figure HE). Thereafter, by galvanically strengthening the metal layer 206 13 wegliche contact pieces 208 formed ( Figure HF), and finally two anchor tongues 21 are laterally struc ⁇ rATORs obtained three-sided exposure, as is shown in Figure HG. Finally, a cover substrate 300, which is designed like the base substrate 100 according to FIG. 10E, is bonded from above with the structured surface down to the anchor substrate 200. In this way, according to FIG.
• a relay is formed with two opposing armature tongues 21, the base fixed contacts 15 and the cover fixed contacts 16 of both systems being connected via the metal layers 103. If the systems were to be switchable separately, these layers would have to be separated or insulated accordingly in the course of production.
• the processing of the individual substrates is carried out not only with two anchor tongues according to FIGS. 10 and 11, but in multiples, so that a matrix arrangement with a large number of relay systems is obtained.
• a multiple is shown in FIG. 12, a common base substrate 100 and a common cover substrate 300 including an armature substrate 200 with a plurality of armature tongues 21.
• the individual switching units, each with an armature tongue 21, can be controlled separately or in parallel by switching the feed paths accordingly, or can be switched.
• FIGS. 13 to 15 show path-voltage characteristics for the three circuit characteristics that are possible.
• the deflection s of the armature tongue is shown in each case via a control voltage U. This results in a closed hysteresis loop.
• FIG. 13 shows the characteristic curves for a bistable changer. With a voltage -Ul, a first contact is made with the deflection + sl. By charging the electret accordingly, the anchor tongue is held in this position, even when the voltage is switched off. Only with a positive voltage 14 + U1, the anchor tongue is switched, so that a second con ⁇ clock -sl is closed with the spring deflection.
• Figure 14 shows the characteristic of a monostable changer.
• the anchor tongue In the unexcited state, the anchor tongue is layered by the electret ⁇ according to one side with the spring deflection + sl deflected and held, so that a corresponding rest contact is closed. Only when the voltage U2, the anchor ⁇ is switched tongue, so that the deflection -sl a working beitsKey is closed. After lowering the excitation voltage to the value U3, the attractive force of the opposite electret prevails, so that the armature tongue is switched and the normally closed contact is closed again.
• Figure 15 shows a three-point switch.
• the anchor tongue in the absence of excitation, the anchor tongue always assumes a middle rest position (zero position), in which none of the contacts are closed.
• a positive voltage U4 is applied, a first contact is closed (with the spring deflection -sl).
• this switch position is not stable, but when the voltage drops to the value + U5 the armature tongue returns to the zero position.
• a negative excitation voltage -U6 a second contact is closed at spring deflection + sl, which opens again when the negative voltage drops to the value -U7.
• a three-point switch with two separate NO contacts and a zero position is thus created.
• the individual relay system or the relay multiple arrangement is accommodated in a conventional manner in a housing, which is not specifically shown.
• a housing is preferably hermetically sealed and, for example, evacuated or filled with a protective gas (N 2 or SF 6 ). It is also expedient to manufacture the housing from metal for the purpose of electrostatic shielding.

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Citations (6)

• 1998
  • 1998-02-20 DE DE1998107214 patent/DE19807214A1/de not_active Withdrawn
  • 1998-12-11 TW TW87120680A patent/TW434617B/zh not_active IP Right Cessation
  • 1998-12-21 EP EP98966571A patent/EP1057196A1/de not_active Ceased
  • 1998-12-21 WO PCT/DE1998/003766 patent/WO1999043013A1/de not_active Application Discontinuation

Patent Citations (7)

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