WO2008110389A1

WO2008110389A1 - Micromechanical switch device with mechanical power amplification

Info

Publication number: WO2008110389A1
Application number: PCT/EP2008/002119
Authority: WO
Inventors: Jörg FRÖMEL; Sebastian Voigt; Steffen Kurth; Stefan Leidich; Andreas Bertz; Christian Kaufmann; Thomas Gessner
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
Priority date: 2007-03-14
Filing date: 2008-03-12
Publication date: 2008-09-18
Also published as: DE102007013102A1

Abstract

The invention relates to a micromechanical switch device for switching an interrupted HF signal line which is provided on a substrate. The inventive device comprises a switch part and a cover which closes the switch part and is characterized in that the switch part comprises at least one ohmic switching contact for bridging and separating the HF signal line and an electrostatic drive for actuating the switching contact, said electrostatic drive being provided with a fixed and a movable electrode. A device for mechanical power amplification is mounted between the electrostatic drive and the switching contact and can be configured as a lever arrangement and/or an elastic element having a progressive effect.

Description

Micromechanical switch device with mechanical

boosting

The invention relates to a micromechanical switch device for switching an interrupted RF signal line according to the preamble of the main claim.

Micromechanical high-frequency switches are known from numerous publications, wherein for the

Construction of such RF switch two fundamentally different technologies are applied, each with two different variants of the actuation:

a. Surface technologies with structures actuated in a direction perpendicular to the device surface, as described, for example, in US Pat. No. 6,307,452 B1, or with structures activated in the lateral direction, as disclosed in US 2002/0153236 A1. b. Volume technology with structures actuated in the direction perpendicular to the component surface, as described, for example, in US 2004/0113727 A, or with structures activated laterally, as in M. Tang, et al. "A single-pole double-throw (SPDT) circuit using lateral metal-contact micromachined switches", from Sensors and Actuators A, Vol. 121, 2005, pages 187-196.

Another principal distinction is made between ohmic and capacitive RF switches, ohmic switching contacts usually by the mechanical contact of at least two good conducting body and the capacitive switching function by the overlap of conductive surfaces with insulating layers therebetween arise, which at high signal frequencies only to develop a very small reaction. Capacitive RF switches thus have a lower cut-off frequency at which the reactance becomes too high to transmit high-frequency signals with little loss and reflection. This disadvantage does not occur in ohmic working RF switches.

The reliability of an ohmic switch contact depends inter alia on the force with which the contact surfaces are pressed against each other or separated again.

The force required for the movement of the mechanical components and the contact force are generated electrically. Conventional techniques either use the electromagnetic force between current-carrying conductors or between conductors and permanent magnets. or the electrostatic force that generally acts on electrically polarized bodies. Since electromagnetic drive concepts either require continuous current and thus generate high power losses or require microtechnologically only partially realizable permanent magnets to be stable in the final states, electrostatic drives are preferable.

The electrostatic force caused by a pair of driving electrodes is, according to equation (1), directly proportional to the discharge of the capacitance after the deflection of the electrodes, which in the hitherto known technical solutions corresponds to the movement of the switching contacts.

Where F _{el is} the electrostatic force, which is directed to increase the capacitance C, and U is the actuation voltage.

Assuming the same operating parameters and thus the same actuation voltage, the dependence on the derivative of the capacitance after the deflection is reduced, which in the case of a plate capacitor with variation of the electrode spacing by

dC ε _o ∈ _r A

(2a) dx (X ₀ -X) ^{2 '}

and upon variation of the coverage of the electrode surfaces dC _ ε _o ∈ _r th dx x _n

where ε _{0 is} the permittivity of the vacuum, ε _{r is} the relative permittivity of the dielectric (usually air, shielding gas or vacuum), X _{0 is} the electrode base distance without application of an actuation voltage U and A are the electrode base area, th the Electrode depth and x are the path of movement of the elec- trode in the direction of the electrostatic force. Since the change in the dielectric is practically impossible or all suitable media have similar relative permittivities, the electrostatic force can only be varied by varying the electrode base distance XQ or the electrode base area A.

To maximize the force F _e i, therefore, either the electrode base distance x ₀ must be reduced or the electrode base area A must be increased. The minimum electrode base distance x _{0 to be set} depends on the production technology and is generally between 1 and 10 μm. Any reduction of the electrode base distance X ₀ is not permitted because in addition to numerous technological problems, the separation of the high frequency signal in the open state of the switch must be ensured and thus a certain contact distance is required. Capacitive crosstalk is only so sufficiently low.

An essential parameter for increasing the contact force is therefore the electrode base area A, which is subject to a limitation of the magnification depending on the technology used. The vertical actuation device described in US Pat. No. 6,307,452 Bl is, as mentioned, produced by means of surface technology. Switch contact and movable actuator electrode are in this type of RF switch, the actual and only moving assembly. An electrical separation between the switching contact and the actuator electrode is technologically difficult to achieve or not possible because of the use of the actuator electrode as an RF current path. Since the electrode base area A is directly connected to the RF current path in this case, the increase in the electrode base area A directly affects the high-frequency characteristics of the RF switch. A significant increase in the electrode base area is therefore not possible or associated with losses with regard to the quality of the high-frequency properties. Another drawback which is particularly relevant in surface-technology manufactured, vertically actuated RF switches are limitations in terms of contact material deposition. The sequential deposition of the layers results in restrictions on the material combination of contact material and sacrificial layer, with regard to technological compatibility such as temperature resistance and adhesive strength.

In the publication by T. Seki et al. "Development of a large-force low-loss metal-contact RF MEMS switch", Sensors and Actuators A, Vol. 132, 2006, pages 683-688 is a vertical-frequency RF switch

Actuation described, which is made by volume microtechnology. In this case, a separation of the high-frequency-carrying conductor is realized by the electrode surface. The electrode base area A can thus be designed independently of the behavior at high frequency. A disadvantage of this technology is how For example, also shown in the cited document US 2004/0113727 Al, that the restoring force can be generated only by spring forces in the rule. The active resetting of the switching contact by means of electrostatic force in this case requires an additional wafer level and thus additional costs. Regardless of the technology used, vertical actuation is generally limited in that the electrode area can not be larger than the device footprint.

The invention has for its object to provide a micromechanical switch device for switching an RF signal line, which provides a high contact force for the switching contact for bridging the RF signal line and which is small and inexpensive to manufacture and good high-frequency properties and high reliability having.

This object is achieved by the characterizing features of the main claim in conjunction with the features of the preamble.

The fact that a device for mechanical power amplification is connected between the electrostatic drive and the switching contact, a higher in relation to the chip area and the actuator voltage or drive voltage contact force when closing the switch contact is made possible. As a result, the reliability of the switching can be increased or the electrode area necessary for generating the contact force can be reduced, as a result of which the actuator voltages are reduced, the size of the components decreases and the operating voltage can be made compatible with that of devices of the telecommunications technology. WEI Furthermore, by providing an arrangement for high-frequency insulation between the switching contact and the drive, electrical isolation of the RF signal line is ensured and good HF properties are ensured.

The measures specified in the dependent claims advantageous refinements and improvements are possible.

It is particularly advantageous that the mechanical force amplification device has a lever arrangement with a predetermined transmission ratio, which is suspended by spring joints, since with such a lever arrangement, the force of the electrostatic drive is amplified, wherein the path of movement of the electrostatic drive is increased with respect to the travel of the switching contact ,

In addition to or instead of the lever arrangement, an elastic element with progressive action or a coupling is advantageously connected in the force flow of the drive to the switching contact, whereby in particular also the opening of the switching contact can be improved. Due to the increasing elongation of the elastic element with progressive action, the force transmitted to the switching contact is increased disproportionately larger and additionally reinforced by the kinetic energy of the comparatively faster movement of the electrostatic drive. Advantageously, in the electrostatic drive provided with a clutch by its kinetic energy, the force for opening the switching element and thus of the switch is generated. This happens because the drive is already in full motion when it is engaged by the coupling on the contact. attacks.

A further advantage of using a progressive-action elastic element is that by suitably dimensioning the progressive-action spring element using an electrostatic drive and varying the electrode distance, the relatively small generated electrostatic force at the beginning of the movement path can also counteract relatively small force of the spring element, ie the electrostatic drive with variation of the electrode spacing produces a force increasing progressively with respect to the travel, which can be better exploited with respect to maximum travel and end force when using a progressive spring joint or a spring element with progressive action than in combination with a linear spring element. This advantage also applies when using the coupling.

Basically, the variation of the electrode spacing in progressive spring makes sense, while the variation of the electrode coverage for levers with high gear ratio and a flywheel with clutch is to be selected.

In a particularly preferred embodiment, the electrostatic drive is provided as a comb drive with a plurality of comb-like fixed electrodes and a plurality of comb-like movable electrodes which engage with each other. With the help of such an arrangement, it is possible to choose a very space-saving geometry of the drive combs.

It is advantageous that the switch part by means of near-surface volume microtechnology is produced and the drive has a lateral actuation. The structuring of monocrystalline silicon by means of anisotropic dry etching allows a largely free design of the drive and the high-frequency-carrying assemblies with high aspect ratio. Through the use of comb structures, the electrode base area can be greatly increased with the same component base area and the realization of small ridge intervals and the implementation of force transmission are thus possible, with no additional material stresses in the silicon due to the use of monocrystalline silicon as the functional layer.

Advantageously, the electrostatic drive, the lever assembly, the spring joints and optionally the elastic element with progressive action and the coupling of a high-impedance silicon substrate are structured, wherein an insulating region is provided between the drive and switching contact for electrical isolation of the RF signal line. In this area, the high-resistance silicon ensures sufficiently good insulation between the RF signal line and the electric drive. As a result, the high-frequency-conducting switching contact can be electrically insulated from the drive carrying the electrode base area, and good high-frequency properties are ensured. Basically, by the use of high-resistance silicon, a substantial electrical insulation between the drive and the RF current path is given. Characterized in that the resistance of the electrical connection between the contacts and the lever mechanism or the actuator or drive compared to the impedance of the switching RF line, which is usually between 30 ohms and 300 ohms is relatively large, the losses of RF power are less than in a variety of previous circuitry. In the case of these previous switch arrangements, therefore, an external decoupling of the HF current path from the actuation voltage is often required, which causes additional components and often a frequency-dependent decoupling. Such disadvantages are avoided with the invention.

The switching contact may be rigid or preferably flexible, since in the latter case, the reliability of the switch is increased due to its lateral friction movement in conjunction with a high contact force.

Advantageously, the drive, the mechanical force amplification device with switching contact and the RF signal line are structured within a bonding frame of the switch part, which is tightly connected to a cover, wherein the cover has openings for access to electrical connection surfaces in a sealed manner. Due to the combination used near-surface micromechanics with encapsulation methods, which allows simultaneous encapsulation of all elements on the substrate

Including any type of gas and pressures, particularly inert or reducing gases, and incorporating integral electrical feedthroughs, allows for a small size and size, while maintaining high reliability and performance. The ability to hermetically fire at wafer level allows the RF switch to be processed with conventional PCB technology, and by including a vacuum, switching times can be reduced. As noted, the fabrication technology for this switch design is a near-surface volume technology such as Air Gap Insulated Microstructure (AIM) technology or Single Crystal Reactive Ion

Etching and Metallization (SCREAM) technology using highly resistive silicon as wafer material. For electrostatic drive, these technologies allow for the production of an electrode area which can be larger than the chip area used for this purpose. Furthermore, these technologies enable the galvanic separation of the high-frequency signal line and the electrostatic drive.

Overall, according to the invention, a micromechanical HF switch is provided which generates a higher contact force with the same operating parameters and the same chip footprint as in prior art RF switches, or which has a lower contact force for generating a contact force corresponding to the required reliability. voltage and / or a smaller chip area required. To ensure good high-frequency characteristics of the switch contact is electrically isolated from the actuator and the reliability of the switch with a large number of switching cycles, eg 10 ^{9 in} terms of low contact resistance when switched on and high RF attenuation in the off state is given.

The invention is illustrated in the drawing and will be explained in more detail in the following description. Show it

Fig. 1 is a schematic representation of the micromechanical switch device according to the invention with unidirectional drive;

FIG. 2 is a schematic representation of the switch device according to the invention with a double-acting drive; FIG.

Figure 3 is a schematic representation of a switch device according to the invention with double-acting drive and elastic elements with progressive action.

4 shows a schematic illustration of the switch device according to the invention with a drive for closing and a drive for opening, wherein a coupling is provided between these drives;

Fig. 5 is a plan view of a switch part of the switch device according to the invention according to the operating principle of FIG.

1;

6 shows a plan view of a switch part of the switch device according to the invention according to the operating principle according to FIG. 2;

Figure 7 is a plan view of a switch part of the switch device according to the invention with a coupling according to the operating principle of FIG. 4.

Fig. 8 a closed with a lid Switch part in section, approximately corresponding to the dash-dotted section line in Fig. 7; and

9 shows a section through a switch device, which corresponds to that according to FIG. 8, but is manufactured by means of the AIM technology.

FIG. 1 shows an exemplary embodiment of the mechanism of action of the micromechanical switch device according to the invention, as implemented in the volume technology with structures activated in the lateral direction, as shown in FIG. The mechanism of action according to FIG. 1 is provided with a lever arrangement 1 which is movable over a plurality of spring joints 2, wherein in the illustration according to FIG. 1 a spring joint 2 has an armature 3, which with the existing structure, in the present case with a Substrate, firmly connected. A broken RF SignalIeitung 4 is indicated schematically, wherein a switching contact 5, which may be rigid or flexible, the broken line 4 can bridge. The switching contact 5 is connected to one end of the lever arrangement 1. The other

End of the lever assembly is connected via the spring joint 2 with an electrostatic drive 6, which acts unidirectionally. When the electrostatic drive 6 is activated, a force is applied to the lever assembly 1 via the spring joint 2, which transmits according to the gear ratio of the lever assembly 1 on the switching contact 5, whereby the switching contact is moved and pressed against the RF line and the switch is closed. If the drive is deactivated, the switching contact 5 is replaced by the restoring force of the suspension Steer 2 opened and remains in the deactivated state of the drive in the open position. The electrostatic drive 6 is, as will be described below, activated by an actuation voltage U.

For a reliable closing and opening of the switch and for a low contact resistance in each case a certain force is required. The force when opening the switch contact is applied without the force of the electrostatic drive 6 by the restoring force of the spring joints and is by

^ k_off ⁼ KXmax '3)

on the contact side of the lever assembly 1 and

ra_off ~ ^ '

on the page of the electrostatic drive. In this case, a is the transmission ratio of the lever assembly 1 with respect to the force and k the rigidity of the spring joints on the contact side of the lever assembly 1 and x _max the maximum distance covered by the switching contact 5. Since the force required to open depends mainly on the design of the switching contact 5, the contact material and the operating conditions such as RF power, humidity, etc., it can be assumed that a certain force for opening the contact, the causally only from the spring joints 2, for the sake of simplicity, is spoken only by a spring joint in the following. Thus, the path of movement of the electrostatic drive 6 ax _max . The applied by the electrostatic drive 6 for the closed switch state force on the contact Side of the lever assembly 1 results from the sum of the restoring force and the required for reliable closing contact force F _k , which depends as well as the force to open the switching of the design of the switch contact 5, the contact material and the abovementioned operating conditions and by

F _k _ _oπ = kX _max + F _k (5)

is described. The force on the side of the electrostatic drive 6 is then

Vv -4- F ^ a on = a ^• ( ⁶ >

The applied by the electrostatic drive 6 force is divided by the transmission ratio a and reduced. Under the exemplary assumption that the amounts of contact force for closing and opening the switch are the same, the force to be applied by the electrostatic drive 6 is about the

Factor a diminished. The force of the electrostatic drive 6 is amplified by the lever arrangement 1, wherein the movement path of the electrostatic drive 6 is increased with respect to the travel of the switching contact 5. Electrostatic comb drive with variation of the electrode coverage are particularly suitable in this approach, because their force does not depend on the movement path x. With a long way on the drive side of the lever and a relatively small force of the drive with variation of the electrode coverage is low applicable. For mechanisms which require a small force at the beginning of the movement, which increases with increasing motion, the variation of the electrode spacing is useful (progressive spring). In Fig. 5, a switch part 14 according to the operating principle of FIG. 1 is shown in plan view, wherein the essential parts, such as drive, Hebelan- order, spring joints are made of a high-resistance silicon and the metallic conductive surfaces and the switching contact are deposited. The switch part 14 or the chip has a circumferential bonding frame 12, within which said components are arranged. The switch part 14 is, as will be described below, connected to a cover through which the necessary for the electrical connection of the high-frequency line and the drive to the outside contacts or electrical connection surfaces 11 are accessible.

The RF line 4, which is produced by metal deposition, is denoted by 4, and the associated ground line with 13th RF line 4 and grounding line 13 are provided with pads 11, which surfaces are also surrounded by the bonding frame, which same hatching is indicated. The bonding frame 12 itself is coated with an electrically conductive metallization, which, as will be explained below, serves as a bonding agent layer in the connection with the cover.

6 denotes a comb drive, which in the exemplary embodiment has two drive parts and which is designed according to the principle of varying the electrode cover. In this case, a multiplicity of electrodes 28, which are fixedly connected to the substrate 27, and a multiplicity of movable electrodes 29 likewise arranged in the manner of a comb, are provided, wherein stationary and movable electrodes 28 and 29 intermesh with each other. The movable electrodes 29 are connected to the lever assembly 1, wherein the lever assembly in this embodiment comprises two parallel in plan view in the resting state parallel beam members 30, each of which, as can be seen in the figure, with two rows of movable electrodes 29 are connected. At the end of the beam parts 30 of the switching contact 5 is arranged, which may consist of one or, as shown, of two or more contact surfaces. The beam parts branch off according to the drive 6 after both

Pages and are connected by spring joints 2 with anchors 3, which in turn are firmly connected to the substrate 27. The actuation voltage for the electrostatic drive 6 is supplied via connection surfaces 11, the upper connection surface 11 with the fixed electrodes 28 and the lower connection surface 11 in FIG. 5, via the armature, the spring joint 2 and the beam parts 30 is electrically connected to the movable electrodes 29. In the area between switching contact and electrical

Drive 6, here in the front part of the lever assembly 1 is an insulating region 20, which must cut the bonding frame 12 at least one place due to the manufacturing technology.

About the lever assembly 1, which is fixed by means of the spring joints 2 elastically by means of armature 3 on the substrate 27 of the switch part 14, the way of e-electrostatic drive 6 is reduced for the switching contact 5. In this case, a force transmission in the ratio of realized by the beam parts 30 lever arms of the lever assembly 1 is achieved. For closing the switching contact 5, the drive 6 is acted upon by the actuator surfaces via the connection surfaces 11, whereby the movable contacts move and the lever arms or beam parts 30 are moved. bend talking. By this movement, the switching contact 5 is pressed against the broken RF line 4, whereby the connection is made. After switching off the actuator voltage stored in the spring joints 2 restoring force opens the switch contact 5 again.

Due to the insulating region 20, which is formed by the interruption of the metallization on the lever arrangement 1, it is possible to separate the electrical potential from the electrostatic drive 6 and the switching contact 5. As already stated, a connection between the illustrated switch part 14 and the cover (not shown) takes place in the region of the bonding frame 12, the contact surfaces remaining accessible from the outside through the cover, so that an electrical contacting of the HF signal line 4 of the HF Ground line 13 and the electrodes of the electrostatic actuator can be achieved.

FIG. 2 shows the basic illustration of a switch arrangement which differs from that according to FIG. 2 by a double-acting electrostatic drive 6 - 1, 6 - 2, ie this drive is designed such that it blocks the movement to close the Switching element 5 and also the opposite movement for opening the switching element 5 applies and thus acts bidirectionally. Since in this case the switching contact is not separated by the forces of the spring joint 2 but by the forces generated by the electrostatic drive 6, the spring joint can be dimensioned in comparison with the solution according to FIG. 1 or FIG. 5 with a much lower rigidity k , The spring joint 2 thus reduces the force of the electrostatic drive by a much smaller part than that in known solutions in which the Force is applied to open the switch contact by a spring, which is the case. The spring joint 2 is expediently designed so that the switch remains in the switched-off position in the state without electrical activation.

In Fig. 6, a switch part 14 is shown with the principle of action of Fig. 2, wherein this embodiment to that of FIG. 5 in the lever assembly 1 and, as already mentioned, in the type of electrostatic drive 6 or 6-1 and 6-2 is different. Since the drive must be bidirectional, the implementation of a second fixed electrode system is necessary in the design as a comb drive. In the embodiment of FIG. 6, a plurality of first fixed electrodes 31, a plurality of second fixed electrodes 32 are thus provided, which together with the movable electrodes 33 form the drives 6-1 for opening and 6-2 for closing the switching contact 5 , In addition, it can be seen that the entire drive 6 consists of two (in principle, it can be several) acting in the same direction areas (Teilantreiben}, which are arranged side by side and have ben ben the same structure, ie, both partial drives consist of two fixed electrode systems and a movable electrode system, wherein in each case the movable comb-like electrodes 33 are located between an electrode 31 of the first fixed electrode system and an electrode 32 of the second fixed electrode system.The division into two or more partial drives has the advantage that the length of the bend due to the electrostatic force, the electromagnetically stressed electrodes and their deformation become smaller due to the electrostatic force. strikes, which is supplied via the right in Fig. 6 provided pads and corresponding lines and preferably for both have the same value, while the movable electrodes 33 are usually grounded. For the arrangement of the two fixed electrode systems from the electrodes 32 and 31, a plurality of electrically insulating crossing points 26 of the electrical connections must be provided so as to organize the bidirectional force generation.

The movable electrodes 33 are connected on the one hand via spring joints 2 fixedly connected to the substrate 27 anchors 3 and on the other hand in each case via a spring joint 2 with a relatively rigid beam 34 which acts on the end of an elongated lever 35. This lever can, as can be seen from FIG. 6, be deflected by 90 ° and has the switching contact 5 at its end. Also, the lever is connected to a spring joint with an anchor.

As in the exemplary embodiment according to FIG. 5, the design of the lever arrangement 1 in interaction with the spring joints 2 and the electrical drives 6-1 and 6-2 effects the movement of the switching contact 5 in the direction of the RF signal line and away therefrom with power transmission and reduction of the travel. In this case, the fixed first electrodes 31 of the drive 6-2 are subjected to a voltage, whereby the movable electrodes 33 move the lever arm over the beam 34 for closing the switching contact 5. In order to open the switching contact 5, the same voltage is preferably applied to the second stationary electrodes 32 of the drive 6-1, whereby the drive 6-2 is no longer activated, as a result of which the movable electrodes 33 are connected to the beam 34 and the Move lever 35 in the opposite direction to open the switch contact 5.

Again, the lever arm 35 is provided in front of the switching contact 5 with an insulating region 20 which intersects the bonding ^¬ frame 5.

In Fig. 3 a further possible ^¬ ness of a device for power amplification or schematically - _B transmission is provided, wherein in the power flow between the switching contact of the drive 6, an elastic member is inserted with progressive effect 7 and 5. In addition, another elastic element with progressive action 7 downstream of the drive 6 and anchored via spring joints 2. The two elasti ^¬ rule elements progressive power 7 serve to increase the force in opening and closing of the switch contact 5. With the elastic members 7 and the spring joints 2 is achieved that the e- LECTROSTATIC drive 6, with its mass inertia at the beginning of the closing - or opening operation moves faster than the switching contact. With increasing elongation of the elastic element with progressive action 7, the force transmitted to the switching contact 5 is disproportionately larger and amplified by the kinetic energy of the comparatively faster movement of the electrostatic drive. This variant realizes the power amplification through the kinetic effect of the moving actuator mass and through the elastic element with progressive action, which enhances the force during detachment.

A further basic Ausführungsführungsbe- game is shown in FIG. 4, wherein a spring-suspended coupling between a first on ^¬ drive 6 for opening and a second drive 6 for Closing the switch contact is arranged. The left drive in FIG. 4 serves to close the contact element and the drive shown in the figure on the right is used together with the clutch 8 to open the switching contact 5. The clutch 8 causes due to a built-in game that the power flow between the electrostatic right drive 6 and the switching contact only comes about when the drive 6 has already reached a certain speed. Its energy is used to generate the force required to open the switch on the switching contact.

An advantage of the embodiments of FIGS. 3 and 4 is that by suitable dimensioning of the spring element with progressive action 7 or the clutch 8 counteract when using an electrostatic drive while varying the electrode spacing of the relatively low electrostatic force generated at the beginning of the movement path also a relatively small force of the spring element can.

As a result, the force generated by the electrostatic drive 6 can better overcome the force of the spring joint 2 to achieve the maximum deflection.

In Fig. 7, an embodiment of a switch part 14 is shown, which implements the operation according to FIG. 4 with a lever arrangement and comprises a clutch 8. In this case, the lever arrangement 1 corresponds in its embodiment to that according to FIG. 6.

The electrostatic drive 6 is divided in two oppositely acting areas 6-1 and 6-2 area. The right drive 6-1 works on the principle of the distance variation of the electrodes and generates the

Force to close the contact. Here, the movable electrodes 36, which in turn are suspended via spring joints 2 to anchors 3, connected to the end of the lever 35 of the lever assembly 1 via a spring joint.

As explained above in connection with FIG. 2 or FIG. 6, the stiffness of the spring joints is much lower than that they could apply the force for opening the switching contact 5. Therefore, much of the power of the electrostatic drive 6-1 becomes effective as a contact force when the switch is closed. The electrostatic drive 6-2 is not acted on during the closing of the switch or the switching contact 5 with an electrical voltage.

The electrostatic drive 6-2 operates on the principle of the variation of the electrode cover, wherein the drive is similar to that of FIG. 5 is formed. It has a plurality of interlocking fixed and movable comb-like electrodes 28, 29, wherein the movable electrodes 29 are connected to the coupling 8, which in turn is articulated to the lever 35. To open the switch, the electrostatic drive 6-1 is not subjected to a voltage and the drive 6-2 is activated. As in the other exemplary embodiments, the latter is anchored elastically to the substrate 27 of the switch part 14 by means of spring joints 2 and armature 3 and moves in the direction of the increase in the electrical capacitance opposite to the effective direction of the electrostatic drive 6-1. The clutch 8 causes by means of a built-in game, that the power flow between the electrostatic drive 6-2 and the lever 1 only comes about when the drive 6-2 and its movable electrode 29 have already reached a certain speed. By means of in the mass of the electrostatic drive 6-2 stored kinetic energy is a power surge transmitted via the lever 1 to the contact element 5, which is sufficiently large to disconnect the contacts. Otherwise, as in the embodiment of FIG. 6 corresponding pads 11 for the supply of voltages to the drives 6-2, 6-1. In the same way, an isolation region 20 is provided.

In all embodiments, the switching contact 5 is deformed when touching the high-frequency signal line 4 and thus enables reliable contact that a friction movement can take place.

FIG. 8 shows a section through a micromechanical switch device, wherein only the cover 9 is to be referred to here for the time being. Such a lid is in the embodiments according to FIGS. 5 to 7 is used and a hermetic closure and a contacting of the electrostatic drive 6 and the high-frequency signal line 4 through the plated-through cover 9 made of glass or high-resistance silicon or other suitable material using a joining process, such as eutectic bonding, anodic bonding or glass-frit bonding achieved. This enables the desired usability for conventional printed circuit board technology and a short switching time due to the possibility of enclosing vacuum in the inner cavity 25. The electrical contacting of the RF signal line 4 and the connections of the electrostatic drive 6 is achieved by openings 10 in cover 9 an access to the pads 11 share.

For the production of the electrical contact between see the respective external terminals of the RF switch and the RF signal line 4 and the electrodes of the electrostatic drive 6, two basic solutions are followed. In the first, the electrical contact during the joining process between the lid and switch part is made. Either the gesarate joining layer or parts thereof is used as e- lectric conductor. In the latter case, these parts do not necessarily contribute to the joining process. The electrical connection produced in this way can be conducted to the outside of the overall structure by means of a through-connection produced in the cover before the joining process or after the joining process. In the case of the second, a gap arises in the area of the electrical contact surfaces during the joining, which opening can be accessed from outside by means of an opening produced before or after the joining process.

In connection with FIG. 8, which illustrates, at least suggestively, a section corresponding to the dot-dash line of FIG. 7, an example of the production method will be explained. The switch part 14 is made of highly resistive silicon. After generating an SiO ₂ layer 15 on the front and back of the substrate 27 of the switch part 14 trenches 16 and movable structures 17 are generated by means of lithographic structuring and a dry etching process with Seitenwandpassivie- tion and subsequent free etching, which in the present case, for example include the lever 35. A subsequently produced partially or completely aluminum layer 18 serves as a high-frequency signal line and makes it possible to make contact with the electrodes of the electrostatic drive which are not to be recognized here, as well as the formation of the electrodes thereof. With the help of a shadow mask during the coating can the metallization is interrupted on the lever arrangement 1 in the insulating region 20 and thus an isolation of the high-frequency signal line 4 from the electrical potential of the electrostatic drive is achieved. Subsequently, the region of the switching contact 5 and opposite regions of the high-frequency line 4 is coated with a layer or a layer stack of gold, platinum, titanium and tungsten or another suitable material.

The closure and the contacting of the connection surfaces is carried out with the aid of the plated-through cover 9 made of glass or another dielectric or another material which is dielectrically insulated in the region of the plated-through holes. The lid 9 includes in the embodiment on the bottom etched recesses 19 to the mobility of the electrostatic drive 6, the lever assembly 1, the spring joints 2 and optionally the progressive spring element 7 or the clutch 8 to ensure. After connection to the switch part 14, the lid 9 is preferably thinned, e.g. to 50 microns thickness. This allows a simple etching of the openings 10. After removing the etching mask for the openings 10 are conductor structures and the

Contacting in the apertures, e.g. generated by means of sputtering through a shadow mask. Subsequently, the contact pads 22 may be applied by chemical thickening and later provided with a solder bump for a flip-chip mounting process.

FIG. 9 shows a schematic cross-section of the high-frequency switch according to the invention in an alternative technology, partly using the AIM method. Here, the switch part 14 made of highly resistive silicon and the lid 9 of a substrate which is at least partially formed of polycrystalline, monocrystalline or amorphous silicon. After the production and structuring of an SiO ₂ layer 15, the aluminum layer 18 is produced and also structured. Thereafter, the trenches 16 and movable structures 17 are worked out. Subsequently, the undercutting of the aluminum support 23 takes place, so that the movable structures are mechanically connected only by these aluminum supports with the fixed areas. The HF--

Signal line 4 and the associated ground line 13 and the contact element 5 may e.g. metallized by means of shadow masks with gold and then the area of the switch contact 21 can also be metallized thick shadow mask.

As in the above embodiment, the lid can in a wet or dry etching process recesses 19 obtained, which allow the movement of the structure. Thereafter, the underside is provided with a patterned gold metallization 24. The apertures 10 are etched from the top to the perforation.

The switch part 14 and the lid 9 are now connected in a eutectic joining process. In this case, the SiO ₂ layer 15 and the aluminum layer on the switch part 14 act as a barrier or conductive layer. This serves to prevent a continuous eutectic layer and is necessary because the contacting of the high-frequency signal line 4 with the connection surfaces 11 or the associated ground line 13 with corresponding connection surfaces 11 would not be sufficiently low due to the poor conductivity of the AuSi eutectic. The above-described switch arrangement can be used in mobile communication for improving the flexibility of the terminals. The distribution of the transmission channels to a plurality of frequency bands, some of which are far apart, enforces compromises in the design of antennas, transmitter and receiver circuits due to limited filter gradients and non-arbitrarily broadband transmitters and receivers. The use of small, high-quality micromechanical high-frequency switches according to the invention will bring about improvements in terms of insertion loss, isolation and above all in terms of energy efficiency in this context.

Claims

claims

A micromechanical switch device for switching an interrupted RF signal line provided on a substrate to a switch part and a cover closing the switch part, the switch part having at least one ohmic switch contact for bridging and disconnecting the RF signal line and at least one fixed and one movable switch Electrostatic having electrostatic drive for actuating the switch contact comprises, characterized in that between the electrostatic drive (6) and switching contact (5), a device for mechanical power amplification and an arrangement (20) for high-frequency isolation are connected.

2. Switch device according to claim 1, characterized in that the device for mechanical power amplification see a lever assembly (1) having a predetermined transmission ratio, which is suspended by spring joints (2).

3. Switch device according to claim 1 or claim 2, characterized in that the device for mechanical power amplification has at least one elastic element with progressive action (7).

4. Switch device according to one of claims 1 to 3, characterized in that the device for mechanical transmission has a coupling.

5. Switching device according to one of claims 1 to 4, characterized in that the arrangement for high-frequency insulation has an insulating region (20) made of electrically non-conductive, high-resistance or semi-conductive material for electrical isolation of the RF signal line (4).

6. Switching device according to one of claims 1 to 5, characterized in that the electrostatic drive (6) as a comb drive with a plurality of comb-like fixed electrodes (28, 31, 32) and a plurality of comb-like movable electrodes (29 , 33) which mesh with each other is formed.

7. Switching device according to one of claims 2 to 6, characterized in that the electrostatic drive is unidirectionally designed to close the switch contact and the spring joints (2) are designed in terms of their restoring force to open the switch contact (5).

8. Switching device according to one of claims 1 to 6, characterized in that the electrostatic drive is bidirectionally formed with at least two electrode systems (31, 33, 32, 33), wherein an electrode system is designed for closing and the other electrode system for opening the switching contact ,

9. Switching device according to one of claims 1 to 6, characterized in that a first and a second electrostatic drive (6-1, 6-2) are provided, wherein the first drive (6-1) operates on the principle of the variation of the electrode spacing and for generating the force to close the switching contact (5) and the second drive (6-2) according to the principle of Variation of the electrode overlap works and is used to generate the force to open the switch contact (5).

10. Switching device according to one of claims 1 to 9, characterized in that the switch part (14) is made by means of micromechanical volume technology and the electrostatic drive (6) has a lateral actuation.

11. Switch device according to one of claims 1 to 10, characterized in that the drive (6), the lever arrangement (1), the spring joints (2) and optionally the elastic element (7) and the coupling (8) of a high-resistance silicon substrate are structured.

12. Switching device according to claim 11, characterized in that the moving parts of the drive, the lever arrangement and the spring joints are connected via anchors (3) to the substrate (27).

13. Switching device according to claim 11, characterized in that the armatures of the lever arrangement via metallization layers (23) are connected to fixed areas.

14. Switching device according to one of claims 1 to 13, characterized in that the drive (6), the device for mechanical power amplification (1) with switching contact (5) and the HF Signal line (4) within a bonding frame (12) of the switch part (14) are structured, which is hermetically sealed to a lid (9).

15. Switching device according to claim 14, characterized in that the cover (9) has openings (10) for access to electrical connection surfaces (11), wherein the cover (9) is hermetically sealed to the connection surfaces (11).

16. Switching device according to claim 14 or claim 15, characterized in that the lid (9), the bonding frame (12) and the substrate (27) closed cavity (25) is under vacuum.

17. Switching device according to one of claims 14 to 16, characterized in that the closed cavity (25) is filled with an inert or reducing gas.

18. Switching device according to one of claims 1 to 17, characterized in that the switching contact (5) is flexible.