EP1246215A1 - Microrelay with new construction - Google Patents

Abstract

A drive capacitor (4,5) drives a movable contact piece (MCP) (1) electrostatically and has two conductive surfaces set apart but parallel. One (4) of these surfaces is applied to one side of the MCP with a flexible suspension (2). Altering the charging status of the drive capacitor moves the MCP into and out of a structure on a mating contact piece (6,7) in order to open and close an electrical contact between the MCP and the mating contact piece.

Description

Technical area

This invention relates to a micro-relay with a new mechanical Construction. The term micro-relay is usually called microscopic electrical switches in which a movable contact piece relative to a Counter contact piece electrostatically, electromagnetically, piezoelectrically or in moved in any other way to open an electrical contact and to shut down. Micro relays are so to speak very small relays, like themselves even from the name results, and become common, but not necessarily, with the help of technological processes made of semiconductor technology and / or microstructure technology are borrowed.

State of the art

Micro-relays with electrostatic drives are known per se. The electrostatic drive is effected by a drive capacitor, the two spaced conductive surfaces, one of which with the movable Contact piece is firmly connected. This allows the electrostatic forces between the surfaces for the mechanical drive of the movable Contact piece can be used. The movable contact piece is to Usually suspended elastically, so that the electrostatic drive against a restoring force of the elastic suspension acts.

In some known micro-relay consists of the movable contact piece an obliquely protruding from a substrate surface lamella, the at the same time contains one of the drive capacitor surfaces, wherein the other Drive capacitor surface and the mating contact piece in the substrate plane are arranged. The electrostatic attraction between the Drive capacitor surfaces, the lamella on the substrate surface pull down, whereupon a contact on the lamellar movable Contact piece touches the mating contact piece in the substrate surface.

Presentation of the invention

The present invention is based on the technical problem, a novel mechanical design for a micro-relay to provide.

Accordingly, the invention provides a micro-relay with a movable contact piece, a drive capacitor for electrostatic Drive of the movable contact piece, which drive capacitor in having substantially parallel spaced, conductive surfaces, one of which is firmly connected to the movable contact piece, an elastic Suspension of the movable contact piece and a mating contact piece, wherein the micro-relay is designed so that by changing the state of charge of the Drive capacitor, the movable contact piece in a direction of movement can be moved in and out of a system to the mating contact piece, to an electrical contact between the movable contact piece and the mating contact to open and close, in which the Direction of movement to the direction of the distance between the Drive capacitor surfaces is almost vertical and the elastic suspension with respect to a movement of the movable contact piece in the Direction of movement has a spring constant, which is much smaller than a spring constant of the elastic suspension with respect to a movement in the direction of the distance of the drive capacitor surfaces.

The basic idea of the invention is therefore that of the conventional concept to move away, in which the direction of movement of the movable contact piece in is substantially equal or parallel to the electrostatic force. Rather, a structure is chosen according to the invention, in which the movable Contact piece is elastically suspended so that it is one with respect to the direction the electrostatic force, ie to the direct distance between the Drive capacitor surfaces corresponding direction, is transverse elastic. at However, this transverse elasticity must have a low component in the direction of force be present so that the drive capacitor surfaces approach each other or removed from each other. It is essential, however, that by far most of the movement of the movable contact piece perpendicular to the electrostatic force, so the capacitor gap is. Quantitatively, this may mean that the transverse component in the movements Overall, preferably at least 5 times, more preferably 7.5 times, still better 12 times and in the best case even more than 20 times the force-parallel component is. This is inventively characterized achieved that the elastic suspension in the desired direction of movement has a much smaller spring constant than in the (conventional) Direction of the distance between the drive capacitor surfaces.

The advantages of this structure can be varied: For one thing it can in some applications to more favorable geometric solutions lead, the drive capacitor surfaces substantially parallel to the Movement direction of the movable contact piece to order. The The invention thus provides a new degree of freedom for the design of micro-relays to disposal.

An essential, but not necessarily according to the invention in Foremost advantage is that through the relatively small Component of the movements of the movable contact piece in the direction the distance of the drive capacitor surfaces with the inventive Microrelay relatively large quantitative ratios between the possible Moving distance of the movable contact piece on the one hand and the maximum occurring intermediate distance between the drive capacitor surfaces On the other hand can be achieved. According to a preferred aspect of Invention, these quantitative ratios should be as large as possible, preferably over 10, better over 20 and best over 40. This is because As a result, on the one hand with relatively small supply voltages sufficiently large electrostatic forces between the Drive capacitor surfaces can be generated, on the other hand, the Isolation distances between the movable contact piece and the Counter contact piece, yes of the movable contact piece in the movement must be overcome, but can be relatively large. The Microrelay according to the invention can thus with a high dielectric strength combine a small drive voltage.

This overcomes a major disadvantage of electrostatic micro-relays, which are Conventionally, already relatively low supply voltages or services allow, however, in terms of dielectric strength are limited to the effect that the drive capacitor even at the largest occurring distance between the drive capacitor surfaces yet another must be able to muster sufficiently large attractive force.

Incidentally, with the conventional electrostatic microrelay in the Compared to the electromagnetic drive solutions only very small Pressure forces between the contacts, ie between the movable Contact piece and the mating contact piece to be applied. From these relatively low contact forces can cause difficulties in the production of Contacts and undesirable high contact resistance arise. Also here offers the invention a remedy.

A favorable embodiment of an elastic suspension with the described properties consists of at least a narrow long Beam whose longitudinal direction of the distance of the Drive capacitor areas corresponds and in the direction of movement of the movable contact piece is much narrower. In the third remaining Direction, the carrier may be relatively extended or relatively flat, preferably adapted to the corresponding dimensions of Drive capacitor and the other components in this direction. This carrier forms a leaf-spring-like structure and can be affected by the electrostatic force Although the drive capacitor is not extended and shortened, but laterally be deformed.

Preferably, at least two of these carriers are provided, which are preferably essentially identical to each other, but in the direction of movement spaced apart from each other. Through their common solid coupling with the movable contact piece then results in a movement of the movable Contact piece, which remains tilt-free, so essentially only off translational components. For this purpose, the embodiments directed. The force-distance relationships, so the spring constants can in such carriers easily calculated using known approximation formulas become.

The movement of the movable contact piece can not only be used for this purpose be, attached to the movable contact piece contact with an associated contact on a mating contact in connection to bring and separate him from it, rather, the same movement can at the same time a further contact of the movable contact piece with a other contact on another mating contact in complementary Connect and disconnect. In this case, therefore, the movable contact piece moved back and forth between the mating contact pieces. You get in a sense, a double switch, which also in a middle position one State offers, in which all contacts are separated. But he can do that too be designed or operated to be between two states is switched, in each case one of the two contact pairs open and the each other is closed. The different advantageous ones Applications of such double switch are the expert without further known.

Incidentally, the carrier or carriers described must be in a force-free state not necessarily elongated, so that they through the electrostatic drive are curved. You can also at the Production of the micro-relay already with a predetermined slight curvature be provided, which then reduces by the electrostatic driving force, canceled or can be reversed in the direction sense.

Furthermore, it is conceivable to make the drive capacitor more complicated than only with two adjacent drive capacitor surfaces. It can too nested structures find use where a larger number Drive capacitor surfaces are associated in an interleaved manner, like two combs engaged with each other. As an illustration Reference is made to the corresponding embodiment.

The direction of movement of the micro-relay according to the invention is preferably parallel to a substrate on which the micro-relay is mounted or on the it has preferably been produced integrated. This also exists Difference to the prior art, in which the directions of movement more or less perpendicular to the substrate plane. The substrate parallel Movement direction, however, has the advantage of two-dimensional structures of the To encourage micro-relays, which are very advantageous in terms of manufacturing technology. So are the typical microtechnological and semiconductor technology Processes such as lithography, etching or coating process usually initially two-dimensional and in three-dimensional structures only with something to realize increased effort. Accordingly, the individual Functional parts of the micro-relay, namely the movable contact piece, the elastic suspension and the drive capacitor, each in their functional structure preferably purely two-dimensional, in one substrate-parallel plane.

Furthermore, a flat construction possible by the substrate-parallel movement is possible often structurally favorable and facilitates in particular subsequent Lithography steps, such as those to be prepared for on the same substrate microelectronic circuits are needed. Even with a protection of Micro-relay through an encapsulation or cover is a flat construction advantageous.

In order to detach the movable parts of the micro-relay from the substrate in an integrated embodiment, it is advisable to provide and remove buried layers at the suitable locations in order to free these parts from the substrate and thus make them elastically deformable or movable. In particular, SiO ₂ layers are suitable for silicon substrates. In particular, the well-known SOI structures (Silicon on Insulator) are suitable for this purpose, especially the so-called SIMOX wafers.

The material silicon is basically a preferred material for the Micro-relay according to the invention.

Another material solution are different glasses. Silicon, however, has the advantage of suitable sorting both insulating and electric be carried out conductive. By ion implantation or diffusion Of dopants can thus easily conductive tracks with adapted structure getting produced. The underlying technology is from the Semiconductor device manufacturing known.

Nevertheless, for example, for the contacts themselves metallizations to be necessary. In a glass micro-relay must basically Metallizations are attached to the electrical wires and Make contacts.

Particular importance for the production of the micro-relay according to the invention, in particular in a two-dimensional realization with substrate-parallel Alignment, have the ion etching, and in particular the so-called RIE procedure. As for the micro-relay relatively large etching depths may be interesting, come preferably the so-called DRIE method Deep reactive ion etching. By suitable process control can be Achieve near vertical etching edges in considerable depths, for example in of the order of 0.5 mm. This can be sufficiently large to achieve Contact areas are important because in the preferred embodiments of the invention provide perpendicular contact surfaces on the substrate can. For this purpose, reference is again made to the exemplary embodiments.

As an example, reference is also made to the article "Vertical Mirrors Fabricated by Deep Reactive Ion Etching for Fiber Optic Switching Applications "by C. Marxer at all, Journal of Microelectromechanical Systems, Vol. 6, No. 3, September 1997, pages 277 - 285. There are indeed micro-optical switches for Fiber optic applications described, however, the process steps can be also readily apply to the invention. The realized there Wall heights of 75 microns can be easily surpassed, if this from Interest is.

Brief description of the drawings

In the following, embodiments of the invention are explained, wherein the thereby revealed features in other than the illustrated Combinations may be essential to the invention.

Figur 1 eine schematische Draufsicht auf ein erfindungsgemäßes bewegbares Kontaktstück mit elastischer Aufhängung;

Figur 2 ein erstes Ausführungsbeispiel für ein erfindungsgemäßes Mikrorelais;

Figur 3 ein zweites Ausführungsbeispiel für ein erfindungsgemäßes Mikrorelais;

und Figur 4 ein drittes Ausführungsbeispiel für ein erfindungsgemäßes Mikrorelais.

In detail shows:

Figure 1 is a schematic plan view of an inventive movable contact piece with elastic suspension;

FIG. 2 shows a first exemplary embodiment of a microrelay according to the invention;

FIG. 3 shows a second exemplary embodiment of a microrelay according to the invention;

and FIG. 4 shows a third exemplary embodiment of a microrelay according to the invention.

FIG. 1 shows a plan view of a structure comprising a movable contact piece 1 with an elastic suspension 2. The viewing direction is perpendicular to the substrate plane, which should be a two-dimensional structure. The schematically drawn base 3 should, as indicated by the hatched background, be firmly connected to the substrate, whereas the elastic suspension forming carrier 2 and the movable contact piece 1 are free from the substrate. In the concrete example, the parts 1, 2 and 3 should consist of Si and be worked out integrally from a Si substrate. The movable contact piece 1 and the carriers 2 have been freed from the substrate by dissolving an SiO ₂ layer buried underneath.

The solid lines represent the force-free arrangement, while the dashed lines the movable contact piece 1 and the elastic Show suspension 2 in the deflected state. This deflection is effected by a force symbolized by N, which acts from top to bottom in FIG. 1, So lies in the substrate plane, but to the difference between the dashed and the solid drawing recognizable Movement direction is substantially vertical. The direction of movement is By the way, not really constant direction. Rather, from this figure vividly that the direction of movement with increasing deflection of the right-angled orientation to the normal force away. However, it is essential that the moving distance is a much larger component f perpendicular to The force N contains as the force-parallel component λ. The component λ is but as important as it is necessary to the movement depicted at all with the force N to produce.

The movement behavior of the movable contact piece 1 results from the Shape and arrangement of the pair of carriers 2 and these are in Movement direction spaced from each other and otherwise identical and to the force N substantially symmetrically aligned to Avoid torque as much as possible. The carriers 2 have a length I in Direction of the force N and are in contrast very narrow, as indicated by h. The depth perpendicular to the plane is denoted by b and corresponds here the depth of the movable contact piece 1. It is for the invention Principle not of concern. As will be seen below, while it increases the Spring constant linear, but in the embodiments, the area increases of the drive capacitor also linear with the depth, so that the depth b only from the technical limits of the etching process and the desired Contact surface depends. However, a too large width of the capacitor 4,5 increases not only the inertia of the movable contact part 1, but also goes directly into the overall size of the micro-relay. Here, then, has a meaningful Compromise can be found.

The deflection f in the desired force normal dimension is approximately calculated f = (NI 3 ) / (2Eb 3 )

Where E is the modulus of elasticity of the material used. It can be seen that the depth b is linear in the spring constant, but this depends on the ratio of length I and narrowness h of the carrier 2 in the third power. The necessary, but as small as possible movement component λ is approximately λ = (3f 2 ) / (5I)

It can be seen that the movement is increasingly dependent on the vertical Orientation to force N differs because the component λ proportional to Square of the component f is. It also recognizes that long vehicles are cheap are for a large ratio of the normal component f to the force-parallel component λ.

Quantitative example values could have a length of I = 1800 μm, a Be narrowness h of 16 microns and a depth b of 450 microns. An exemplary Value for the force N of about 4 mN then leads to f = 40 μm and λ = 0.53 μm. The Movement of the movable contact thrust 1 is thus as good as perpendicular to N.

FIG. 2 shows the basic structure schematically illustrated in FIG. 1 in a concrete application form. On the movable contact piece 1, in this case on the side facing the carriers 2, an electrically conductive surface layer 4 is mounted, which is opposite to a second electrically conductive surface layer 5 on a substrate-fixed part. Between these two drive capacitor surfaces 4 and 5, a voltage U _{d can be} applied which causes the electrostatic drive force N according to the following approximation: N = (ε 0 AU d 2 ) / (2d 2 )

Here, A is the area of the drive capacitor 4, 5 and also proportional to b. d is the distance between the two drive capacitor surfaces 4 and 5. It can be seen immediately that very small by correspondingly small distances can generate large electrostatic forces, because the distance d in the second Potency occurs. Furthermore, wide capacitors in the sense of the horizontal in the Drawing plane, so large distances between the carriers 2, low. at a distance d of 1 .mu.m result at a supply voltage of 36 V and a typical area A of 450 μm x 1500 μm forces in the range of 4 mN.

The movement of the movable contact piece 1 corresponds to the illustration in FIG. 1. FIG. 2 shows that the movable contact piece 1 is switched back and forth between two counter-contact pieces 6 and 7. For this purpose, it has, at its ends extending beyond the supports 2, in each case an angled attachment region 8 or 9, which carries in each case two metal contacts, which are connected via a metallic conductor track. These contacts can come in contact with each associated two contacts on the mating contact pieces 6 and 7, which in turn are electrically isolated from each other. They are thus bridged by the contacts on the angled regions 8 and 9 of the movable contact piece 1. The contact force P results from this P = (f / l) N. For N = 4 mN this gives a contact force P of approx. 0.09 mN.

The hatched areas in Figure 2 indicate that the two Drive capacitor surfaces 4 and 5 and in each case from the contacts to the Counter contact pieces 6 and 7 outgoing conductor tracks ion-implanted Si regions are formed. The black filled contacts are metallized, such as by lateral Schrägbedampfung or Plasma deposition and corresponding masking.

It can also be seen that the micro-relay of Figure 2 in uncharged Drive capacitor 4, 5, the contacts on the left mating contact piece. 7 bridged and by voltage application of the capacitor 4, 5 so can be switched, that instead the contacts on the right Counter contact 6 are bridged. The drive capacitor surfaces 4, 5 are aligned with each other so that they are approximately in the middle of this Way directly opposite, so that each at the two ends of a way certain offset, but because of the actually low quantitative significance is immaterial.

It has already been mentioned that the total contact surfaces by adjusting the Depth b can be determined. In addition, the metal contacts can also in the vertical direction in Figure 2 be made wider when the contact surface plays an essential role.

If you look at one of the two angled areas 8 and 9 and the associated mating contact 6 or 7 in Figure 2 thinks away, it can be seen directly that realize with this structure and simple switch leave open or closed in a de-energized state (normally open / normally closed).

In the second embodiment of Figure 3 is opposite to the variants from Figure 1 and 2 to the effect that before the carrier 2 'only are slightly curved slightly S-shaped in the illustrated stress-free state, namely, approximately as in the deformed state of Figure 1. This can by corresponding structuring of the mask in the DRIE process, with which this Structures are machined out of the silicon wafer, easily realized become. In addition, the drive capacitor in this example is on in the Comparison to Figure 2 other side of the movable contact piece. 1 arranged, and therefore designated 4 ', 5'. Finally, the micro-relay is in This case designed so that the "right switch" 6, 8 in the tension-free Condition is closed while the "left switch" 7, 9 in the tension-free Condition is open.

Due to the electrostatic attraction between the drive capacitor surfaces 4 'and 5', the movable contact piece 1 in Figure 3 moves to the left be, with the carrier 2 'stretch largely or with deformed direction reversed direction.

The arrangement of the drive capacitor 4 '5' should be in simple micro-relay Incidentally, done so that when closed a maximum Contact force results, so the minimum distance between the Drive capacitor surfaces 4, 5 and 4 ', 5' is present. In the first and in the second embodiment, this is for the right switch and for the left Given a switch.

Figure 4 shows a third embodiment, which is a variant of the second Embodiment of Figure 3 represents. The difference is that the drive capacitor in this case of comb-like nested surfaces consisting of 4 "and 5". Again, these are Si structures with corresponding dopants (or metallizations), like the Show hatching. By a manufacturing technology little problematic Complication of the mask layout can thus be effective Area of the drive capacitor can be multiplied, in this case tripled. Otherwise, this embodiment corresponds to the above described.

All embodiments are due to the two-dimensional structure technically unproblematic and on the other hand show an unusually good Compromise between contact closure force, supply voltage and Dielectric strength in the open state.

LIST OF REFERENCE NUMBERS

1

movable contact piece

2

elastic suspension, namely narrow long straps

3

Base

4, 4 ', 4 "

conductive capacitor surface on the movable contact piece

5, 5 ', 5 "

solid electrically conductive drive capacitor surface

6, 7

Against contacts

8, 9

Angled approach areas of the movable contact piece

f

Movement distance across the force

I

Length of a carrier 2

H

Narrowness of a carrier 2

Claims (14)

micro-relay with a movable contact piece (1), a drive capacitor (4, 5, 4 ', 5', 4 ", 5") for the electrostatic drive of the movable contact piece (1), which drive capacitor has two, substantially parallel spaced, conductive surfaces (4, 5, 4 ', 5', 4 ", 5"), one of which (4, 4 ', 4 ") fixed to the movable contact piece (1) connected is, an elastic suspension (2, 2 ') of the movable contact piece (1), and a mating contact piece (6, 7), wherein the micro-relay is designed so that by changing the charge state of the drive capacitor (4, 5, 4 ', 5', 4 ", 5"), the movable contact piece (1) in a direction of movement in and out of contact with the mating contact piece ( 6, 7) can be moved to open and close an electrical contact between the movable contact piece (1) and the mating contact piece (6, 7), characterized in that the direction of movement to the direction of the distance between the drive capacitor surfaces (4, 5, 4 ', 5', 4 ", 5") is almost vertical, and the elastic suspension (2, 2 ') has a spring constant substantially smaller than a spring constant of the elastic suspension (2, 2') with respect to movement in the direction of the distance with respect to movement of the movable contact piece (1) in the direction of movement the drive capacitor surfaces (4, 5, 4 ', 5', 4 ", 5"). Micro-relay according to claim 1, wherein the largest occurring in operation Distance of the drive capacitor surfaces (4, 5, 4 ', 5', 4 ", 5") very much smaller than that during operation of the movable contact piece (1) traveled distance (f) is in the direction of movement. Micro-relay according to claim 1 or 2, wherein the elastic suspension (2, 2 ') is substantially parallel to the direction of the distance the drive capacitor surfaces (4, 5, 4 ', 5', 4 ", 5") extending and in Comparison to its length (I) in this direction in the direction of movement has much narrower (h) carrier (2, 2 '), with the movable Contact piece (1) is firmly connected and this due to its length (I) and narrowness (h) is elastically movable in the direction of movement. Micro-relay according to Claim 3, in which the elastic suspension (2, 2 ') at least two of the described carrier (2), which in the Movement direction are offset from each other in parallel. Micro-relay according to one of the preceding claims, in which the movable contact piece (1) between two mating contact pieces (6, 7) can be switched back and forth. Micro-relay according to one of the preceding claims, wherein the / the Carrier (2 ') along its length (I) slightly curved / curved and by the drive capacitor (4 ', 5', 4 ", 5") during the movement of the movable contact piece (1) can be stretched / can. Micro-relay according to one of the preceding claims, wherein the Drive capacitor (4 ", 5") a variety nested parallel having spaced conductive surfaces (4 ", 5"). Micro-relay according to one of the preceding claims with a substrate, on which the micro-relay is attached (3), the direction of movement of the movable contact piece (1) is substrate-parallel. Micro-relay according to one of the preceding claims, located on the Substrate is produced in an integrated manner. Micro-relay according to one of the preceding claims, at least Claim 8, wherein the movable contact piece (1), the elastic Suspension (2, 2 ') and the drive capacitor (4, 5, 4', 5 ', 4 ", 5") at least a substantial part of their respective functional structure in Form of a two-dimensional structure in a substrate-parallel plane respectively. Micro-relay according to claim 9 and claim 10, with one between the arranged two-dimensional structures and the substrate buried layer, which is under movable structural parts (1, 2, 2 ', 4, 4', 4 ") is removed. Micro-relay according to one of the preceding claims, characterized by Ion etching method, preferably a DRIE method. Micro-relay according to one of the preceding claims, which is in essentially consists of silicon. Micro-relay according to one of claims 1-12, consisting essentially of Glass exists.

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