DE102006001321B3 - Switching device, has two signal lines and ground lines which are controlled by plated-through hole through laminar extending substrate, where signal lines surrounded by ground lines - Google Patents

Abstract

The device has two signal lines (2) surrounded by ground lines (3,4) of controlled electromagnetic signal, where the signal lines or the ground lines are contactable at front side by substrate surface area operation drive, drivable to contact unit (8). The signal line and ground lines are controlled by a plated-through hole through a laminar extending substrate (5). The signal line and/or the ground lines are contactable in the range of the plated-through holes of the respective line of the contact unit.

Description

Technical area

The The invention relates to a device for switching an electromagnetic High frequency signal on a coplanar waveguide.

State of the art

Microsystem technology High frequency switch (MEMS (microelectromechanical system) RF switch) are mechanical devices for switching electromagnetic Radio frequency signals. MEMS RF switches have advantages over field effect transistors or PIN diodes, as they have very low losses in forward position cause and a very good insulation effect in locked position exhibit. About that In addition, they have excellent linearity in terms of signal transmission at high frequencies and a very low power consumption, taking this in particular for electrostatically driven switch applies. MEMS RF switch typically used at signal frequencies from 0.1 GHz to 100 GHz.

MEMS HF switches are usually used in conjunction with microfabricated used planar waveguides. Microfabricated high frequency waveguides exist typically in one embodiment as a microstrip conductor of two or in one embodiment as coplanar waveguide made of three metallic tracks, by means of produced on photolithography based planar technologies.

In a microstrip conductor, the two interconnects are on opposite Sides of a dielectric substrate, in typical embodiments the conductor track on a substrate level over the entire surface running and grounded. Not grounded track is referred to as a signal line and provides the actual functional trace.

Especially However, advantageous are coplanar waveguides in which a central Trace, the so-called signal line, from two grounded tracks, the so-called ground lines, is surrounded. An RF signal is spreading on a coplanar waveguide as a quasi-transversal mode between signal line and the ground lines. The advantages a coplanar waveguide to a microstrip are the simpler production (all traces are located on one level), the lower electromagnetic radiation (and thus a low signal attenuation) and the low electromagnetic interference juxtaposed Waveguides.

It There are two basic circuit embodiments of MEMS RF switches. In the serial arrangement is the signal line of the RF waveguide interrupted and can be closed by a contact piece. In the Short circuit arrangement becomes the signal line of the RF waveguide not interrupted but connected to the ground lines and with it shorted. The typical embodiments are in Gabriel M. Rebeiz "RF MEMS, Theory, Design, and Technology, John Wiley & Sons, Inc., 2003, Chapter 4 and 5 described.

There are two possible embodiments for the switching contacts in HF switches: Electrically conductive, such as metallic contacts and capacitive contacts. Typically, RF switches are used with electrically conductive contacts in the serial arrangement and function similar to classic relays, but no load currents but RF signals are switched. By closing a conductive contact piece, which is often designed in the form of a bending beam, an electromagnetic signal is passed or interrupted via the switch. This type of RF switch is particularly suitable for frequencies up to several GHz. Typical examples are in EP 0 751 546 B1 and EP 1 426 992 A2 be written. Some publications also describe HF switches with electrically conductive contacts in the short-circuit arrangement, such as in the aforementioned work by Rebeiz "RF MEMS, Theory, Design, and Technology." The movement of the contact piece in most switches is done by one Electrostatic drive, as this drive has a favorable, very low power consumption.

For signal frequencies from a few GHz up to a few hundred GHz are usually with HF switch capacitive contacts used in the short-circuit arrangement. In These switches become an electromagnetic signal in a waveguide led, whereby over the Signal line of the waveguide a conductive membrane similar to one bridge arranged in the case of a coplanar waveguide with the two ground lines is connected and their distance from the signal line can be varied. If enough great Distance between diaphragm and signal line can be low with the signal Losses happen. Is the distance of the membrane to the signal line decreases, increases the capacity between Membrane and signal line. The signal couples in this state Capacitive in the conductive membrane and is connected to the ground lines of the coplanar waveguide shorted. The signal can be the switch in this state not happen.

In a typical embodiment, the signal line from the conductive membrane is through a dielectric layer separated to maximize capacitance in the blocking position and prevent electrical contact. A typical capacitive RF switch is in US Pat. No. 6,803,534 B1 described. There are other embodiments of the same principle, wherein, for example, in DE 100 37 385 A1 the signal line is designed as a movable membrane and is led to an electrode on the substrate, which is connected to the ground lines. The movement of the membrane is preferably realized by an electrostatic drive. In the above examples, a DC voltage between the membrane and signal line or in DE 100 37 385 A1 placed between membrane and ground line to achieve movement of the membrane. In other embodiments, the membrane is moved across electrostatic surface drives associated with the membrane (D.M. Peroulis et al., "MEMS devices for high isolation switching and tunable filtering", IEEE MTT-S International Microwave Symposium Digest, Boston, June 2000, 1217- 1220).

In US Pat. No. 6,798,315 B2 "Lateral Motion MEMS Switch" describes a serial RF switch in which a broken signal line is contacted and closed laterally by means of a contact piece.The lateral arrangement of the switch parallel to the substrate plane allows the use of a lateral, electrostatic comb drive Comb drives are advantageous because the electrode surface required for the drive is not limited by the substrate surface in comparison to the electrostatic diaphragm or bending beam drives acting vertically to the substrate plane.

In DE 103 28 183 A1 a high-frequency component is described, in which the electromagnetic signal can be passed via feedthroughs through a base body from a planar waveguide applied on the underside to a waveguide located on the upper side, so that there is a continuous connection. The described component is, for example, a short circuit switch according to DE 100 37 385 A1 ,

Disadvantages of the state of the technique

MEMS RF switches often have low reliability in number possible switching cycles. The main failure cause of electrostatically driven switches with electrically conductive Contact is a wear of the Contact. The cause of are the wear the relatively small drive and contact forces of MEMS RF switches, the a use of soft contact materials, such as e.g. Gold, required make, in turn, a sufficient contact surface between ensure the contacts. The main failure cause of electrostatically driven switches with capacitive contact is an education of non-reversible charges in the contact area, which, depending on the polarity, opens or closes the Prevent switch.

The reliability of MEMS RF switches can be increased by increasing the contact force and thus potential Use of relatively hard, low-wear contact materials and by a high restoring force to open of the switch can be improved. A high restoring force, for example by a rigid membrane or bending beam element or by a additional Reset mechanism reached. Such embodiments increase but again the requirements for a drive to close the Switch, because the restoring force of the Counteracts contact force. Previous MEMS RF switch with vertical to the substrate level electrostatic membrane or bending beam drives can apply only relatively small forces, because the size of the drive by the size of the switch is limited.

MEMS RF switch with lateral electrostatic comb drives, as in US Pat. No. 6,798,315 B2 described, can apply relatively large forces on a contact piece. However, this type of switch has the disadvantage that it can only be used in microstrip conductors so far. In a coplanar waveguide, the signal line to be closed is surrounded by two ground lines and thus can not be closed or opened with a lateral arrangement of drive and contact piece.

The predominant Number of MEMS RF switches are using surface micromechanics technologies produced. In surface micromechanics layers are selectively deposited on a substrate selectively removed. Especially the production of free movable diaphragms or bending beams by so-called sacrificial layer etching places high demands on the production technology, since the layer stress the membrane or bending beam material very accurate and reproducible must be adjusted.

task the invention

The The object of the invention is an electromagnetic RF signal to switch on a coplanar waveguide.

Solution of task

• a) die Signalleitung (2) sowie die Masseleitungen (3, 4) jeweils mittels wenigstens einer Durchkontaktierung (6a, 6b, 6c, 7a, 7b, 7c) durch ein sich flächig erstreckendes Substrat (5) geführt sind und
• b) die Signalleitung (2) und/oder die Masseleitungen (3, 4) stirnseitig von einem mittels eines parallel zur Substratoberfläche arbeitenden Antriebs (12 bis 17) antreibbaren Kontaktstück (8) kontaktierbar ist/sind.

The task is solved by a Vorrich to switch one in a coplanar waveguide ( 1 ) with a signal line ( 2 ) and two the signal line ( 2 ) surrounding ground lines ( 3 . 4 ) guided electromagnetic signal, in the

• a) the signal line ( 2 ) as well as the ground lines ( 3 . 4 ) each by at least one via ( 6a . 6b . 6c . 7a . 7b . 7c ) by a flat extending substrate ( 5 ) are guided and
• b) the signal line ( 2 ) and / or the ground lines ( 3 . 4 ) end face of a by means of a parallel to the substrate surface working drive ( 12 to 17 ) drivable contact piece ( 8th ) is contactable / are.

Advantages of invention

The Through holes of the coplanar waveguide allow the Contact signal line by means of a contact piece at the front, without interrupting the ground lines of the waveguide. there becomes the high frequency effective geometry of the waveguide through the frontal contacting substantially not impaired. This has the consequence that the signal attenuation the switch for electromagnetic signals in Durchlassstellung is very low.

In Locking position causes the frontal contact piece in particular a galvanic or a high-frequency, capacitive Short circuit between one or both ground lines and the signal line. An RF signal can therefore no longer pass through the waveguide. The switch thus causes a high isolation of the RF signal in Waveguides.

By the frontal contact can be a lateral, parallel to Substrate-level drive can be used for switching. One parallel to the substrate surface working drive of the contact piece has the advantage that he spread in the width or depth of the device and thus a greater driving force as a perpendicular to the surface apply working drive or with a lower drive voltage (for example, from 3 V to 12 V) can be operated.

By the size Force can in the case of an electrically conductive contact piece good contact even when using hard contact materials and thus a high reliability in terms of the number of possible Switching cycles are achieved. Furthermore, a large restoring force, for example, by a Rückstellme mechanism, be realized, which ensures a reliable opening of the switch.

The Device allows the realization of a switch in short circuit arrangement in which the signal line is connected to the ground lines and the realization of a switch in a serial arrangement the signal line can be interrupted and closed. Furthermore, a switch with two contact pieces on realized the respective end faces of the two vias be that for very high signal frequencies is suitable.

By the frontal arrangement of the contact pieces and the possible substrate-parallel arrangement of the electrostatic drive, the switch with a reactive Ionenätzprozess, the so-called Deep Reactive Ion Etching (DRIE, description in DE 42 41 045 C1 ), are made of single-crystal silicon. In contrast to surface micromechanics, the production process is very well suited for the production of movable structures. In a monocrystalline material, no residual stresses can occur which adversely affect the function of the switch. In addition, the material is subject to almost no mechanical aging phenomena, as they can occur, for example, in moving metallic systems.

description of exemplary embodiments

Further advantageous embodiments emerge from the dependent claims as well as from the attached Drawings closer explained Embodiments. Show it:

1a a plan view of a switch in a short-circuit arrangement according to a first embodiment of the invention, wherein the switch is in the blocking position;

1b a view of the switch according to 1a in passage position;

1c a side sectional view of the switch 1b along the line AA according to 1b ;

1d the bottom of the switch off 1b ;

1e the underside of a switch according to a second embodiment, wherein the vias on the bottom are connected to coplanar waveguides.

2a a plan view of a switch in a serial arrangement according to a third embodiment of the invention, wherein the switch is in the passage position;

2 B a view of the switch according to 2a in locked position;

2c a side sectional view of the switch 2 B along the line AA according to 2 B ;

2d the bottom of the switch off 2 B ;

3a a view of the switch according to 1a in passage position with an electrostatic comb drive and two return springs;

3b a view of the switch according to 3a However, the switch is in the locked position;

4 a plan view of a switch with two contact pieces according to a fourth embodiment of the invention;

5 a plan view of a switch with an input and two switchable outputs according to a fifth embodiment of the invention;

6a a plan view of a switch in the blocking position according to a sixth embodiment having only a passage of the waveguide through the substrate;

6b a view of the switch according to 6a in passage position;

6c a side sectional view of the switch 6b along the line AA according to 6b ;

6d the bottom of the switch off 6a ,

1a shows an embodiment of the switch in short circuit arrangement for a coplanar waveguide 1 with a signal line 2 and two ground lines 3 and 4 in locked position (the drive of the switch is not shown). The cables are made of a conductive material and are located on a substrate 5 in that it is electrically or only slightly conductive. The width of the lines is typically in the range of 10 .mu.m to 200 .mu.m. The height of the lines perpendicular to the imaging plane is typically 5 μm to 100 μm. Alternatively, one or more intermediate layers may be present between the coplanar waveguide and the substrate, causing, for example, an insulation between interconnects and substrate.

At the respective ends of the signal line and the ground lines are plated-through holes 6a . 6b . 6c and 7a . 7b . 7c passing the coplanar waveguide through the substrate 5 through to the opposite substrate surface. The vias are in 1c and 1d represented and serve a connection of the switch, for example by so-called flip-chip technology, to any RF circuit. Alternatively - as in 1e shown - the vias also on the opposite substrate surface with coplanar waveguides 18 . 19 be connected. The coplanar waveguides 1 the front are in 1d and 1e indicated by dashed lines.

The implementation of the waveguide 1 through the substrate 5 allows a lateral, frontal contacting of the signal line 2 of the coplanar waveguide 1 which is not possible with a planar design without interruption of at least one ground line. That opposite to the substrate 5 and the waveguide 1 movable contact piece 8th is designed so that it moves with a parallel to the substrate plane, with the section 9 the signal line 2 with the ground lines 3 and 4 connect in the area or in the vicinity of the vias and thus can short circuit.

The connection between section 9 and the wires 2 . 3 . 4 can be designed as an electrically conductive contact or as a capacitive contact or as a combination of both types of contact. In all embodiments of the contact element 8th becomes the signal line 2 with the ground lines 3 and 4 high-frequency technically connected or short-circuited. The high-frequency short circuit of signal line and ground lines causes an RF signal, the switch can no longer or only very heavily attenuated happen.

The contact piece 8th and its subarea 9 and the wires 2 . 3 . 4 of the coplanar waveguide 1 in the area of the contact points can have various variations. Particularly advantageous embodiments are those in which a good contact closure and thus a good transition for an RF signal are ensured. Furthermore, embodiments are possible in which the signal line is connected only to a ground line or in which the contact element is elastically connected to one or two lines of the waveguide.

1b shows the switch 1a in the open state. By retracting the contact piece 8th become the leads of the coplanar waveguide 1 no longer shorted and a high frequency signal can pass the switch.

2a shows an embodiment of the switch in a serial arrangement. In contrast to the embodiment in 1a the signal line consists of the two subareas 2 and 10 in the area of the via 6b through a recess 11 are separated from each other. The contact piece 8th with the section 9 causes in this embodiment, a compound of the two sections 2 and 10 the signal line. In the shown position of the contact piece 8th An RF signal can pass the switch.

2 B shows the switch 2a in locked position. The contact piece 8th is withdrawn and the subareas 2 and 10 the signal line are not connected. In this condition, an RF signal can no longer pass through the switch or only to a very high degree.

2c shows a sectional view of the switch along the line AA according to 2 B in which the vias 6b and 7b can be seen. 2d shows the bottom of the switch 2a on which all vias 6a . 6b . 6c and 7a . 7b . 7c can be seen. The coplanar waveguide 1 the front is in 2c indicated by dashed lines.

3a shows an embodiment of the switch 1a with an electrostatic comb drive. The drive shown is with the contact piece 8th connected and consists of two comb-shaped toothed electrodes 12 and 13 , wherein an electrode 12 is movable and has elastic suspensions 14a and 14b with the substrate 5 in the places 15a . 15b . 15c connected is. The representation of the electrostatic comb drive shows only one possible example. The drive may be larger or smaller and have any number of toothed electrode fingers. The opening of the switch is in this embodiment by a return mechanism, consisting of two elastically suspended return springs 16a . 16b and attacks 17a . 17b at the movable electrode, supported.

3b shows the switch 3a in locking position with deflected movable electrode 12 and deflected return springs 16a . 16b , The deflection of the system is achieved by applying a DC voltage to the electrodes 12 and 13 reached. Typically, the electrodes are separated by an insulating layer or spacers to avoid shorting.

The return springs 16a . 16b at the same time prevent or reduce bouncing of the contact element 8th when hitting the signal line 2 or the ground lines 3 . 4 because it reduces the impact speed at the impact of the contact piece 8th reduce to these lines.

Deviating from 3a and 3b Embodiments of the drive are also possible in which the contact element is connected in the rest position with the lines of the waveguide. In this case, applying a DC voltage causes the switch to open.

4 shows a further embodiment as a switch, wherein in each case a contact element on both sides of the coplanar waveguide in the region of the plated-through holes 8th is attached.

5 shows a further embodiment of the switch in which a coplanar waveguide branches into two coplanar waveguides. In this embodiment, an input signal by means of two contact elements 8th be switched to two alternative outputs.

As a general rule For example, a waveguide may include one or more such branches have, so that he has one input and several outputs, one output and several entrances or more inputs and several outputs having. In this case, each input and each output with a switch of be connected as described above, so that in total a multiple switch device results.

6a shows an embodiment of the switch with only one implementation of the coplanar waveguide through the substrate 5 in locked position. The in the sectional drawing according to 6c shown and in 6d dashed lined vias 6a . 6b . 6c can in this embodiment with the contact piece 8th short-circuited in terms of frequency. The vias 6a . 6b . 6c are on the bottom of the switch ( 6d ) is connected to a continuous coplanar waveguide. The coplanar waveguide 18 may be as shown in this embodiment, on the underside of the switch or on another substrate, which is preferably connected to the switch in flip-chip technology. Be the vias 6a . 6b . 6c as in 6a shown by means of the contact piece 8th connected, an RF signal, the switch can not pass or only strongly attenuated. 6b shows the switch 6a in passage position. The vias 6a . 6b . 6c are not in this case by the contact piece 8th connected and a signal can pass the switch largely undisturbed.

The contact elements 8th according to the in the 2a to 2 B . 4 . 5 and 6a to 6d illustrated embodiments are preferably also with an electrostatic comb drive according to the 3a / 3b Thus, in this regard, the remarks on the 3a and 3b is referenced.

The switches described above are preferably manufactured and consist of photolithography-based so-called planar technology predominantly or substantially entirely of silicon or a metal. Preferably, metallic structures are produced galvanically. As an alternative to silicon as substrate material, it is also possible to use another semiconductor material, glass or another ceramic material.

Farther It is preferably provided that the respective switch device according to the invention hermetically encapsulated. That it has a hermetic cover on it completely surrounds, possibly within the device existing cavities Have vacuum or in these cavities a protective gas atmosphere or an inert gas atmosphere is included.

Of It is further provided that these devices according to the invention in so-called flip-chip versions to be created. In this case, small devices are attached to the chip housing of the device solder balls or pads provided, which then when connecting the device under defined Location to be connected Soldered HF circuit become.

alternative can Wire bonding technologies or other technologies are used to the switching devices according to the invention to connect with other circuits.

Claims (22)

Device for switching one in a coplanar waveguide ( 1 ) with a signal line ( 2 ) and two the signal line ( 2 ) surrounding ground lines ( 3 . 4 ) guided electromagnetic signal, wherein the signal line ( 2 ) as well as the ground lines ( 3 . 4 ) each by at least one via ( 6a . 6b . 6c . 7a . 7b . 7c ) by a flat extending substrate ( 5 ), characterized in that the signal line ( 2 ) and / or the ground lines ( 3 . 4 ) end face of a by means of a parallel to the substrate surface working drive ( 12 to 17 ) drivable contact piece ( 8th ) is contactable / are. Device according to Claim 1, characterized in that the signal line ( 2 ) and / or the ground lines ( 3 . 4 ) in the region of at least one of the plated-through holes ( 6a . 6b . 6c . 7a . 7b . 7c ) of the respective line from the contact piece ( 8th ) is contactable / are. Device according to claim 1 or 2, characterized in that the signal line ( 2 ) as well as the ground lines ( 3 . 4 ) in each case by means of at least two plated-through holes ( 6a . 6b . 6c . 7a . 7b . 7c ) are guided through the substrate. Device according to one of the preceding claims, characterized in that it is a switch in short-circuit arrangement, by means of which the signal line ( 2 ) with one or both ground lines ( 3 . 4 ) is short-circuitable. Device according to one of the preceding claims, characterized in that by means of the contact piece ( 8th ) Capacitive contact can be produced. Apparatus according to claim 5, characterized in that a dielectric layer between the contact piece ( 8th ) and the signal line ( 2 ) or the ground line (s) ( 3 . 4 ) is located. Apparatus according to claim 4, characterized in that it is in the contact piece ( 8th ) is an electrically conductive contact. Device according to one of claims 1 to 3, characterized in that it is a switch in a serial arrangement, in which the signal line ( 2 ) at its front end one part ( 10 ) separating recess ( 11 ), the subregion ( 10 ) with a via ( 6b ), wherein the contact piece ( 8th ) in Durchlassstellung bridging the recess ( 11 ) and in the blocking position, the signal line ( 2 ) is interrupted. Device according to one of the preceding claims, characterized in that the drive ( 12 - 17 ) is an electrostatic drive. Device according to claim 9, characterized in that that the drive interlocking, comb-like arranged electrodes having. Device according to one of the preceding claims, characterized characterized in that it is made largely of silicon. Device according to one of claims 1 to 10, characterized that it is largely made of a metal. Device according to one of claims 1 to 10, characterized that they are largely made of a combination of silicon and metal is made. Device according to one of the preceding claims. characterized in that the substrate ( 5 ) made of glass or other ceramic material. Device according to one of claims 1 to 13, characterized in that the substrate ( 5 ) consists of silicon or another semiconductor. Device according to one of the preceding claims, characterized in that the plated-through holes ( 6a . 6b . 6c . 7a . 7b . 7c ) are galvanic vias. Device according to one of the preceding claims, characterized in that it is a switch with two contact pieces at the plated-through holes ( 6a . 6b . 6c ) and the vias ( 7a . 7b . 7c ). Device according to one of the preceding claims, characterized in that the waveguide ( 1 ) has one or more branches such that it has one input and multiple outputs, one output and multiple inputs or multiple inputs and multiple outputs, each input and output may be connected to a switch to form a multiple switch. Device according to one of the preceding claims, characterized in that it is a switch in which the signal line and the ground lines of the coplanar waveguide only by means of one through-hole ( 6a . 6b . 6c ) are guided through the substrate. Device according to one of the preceding claims, characterized characterized in that they are layered in planar technology having constructed structure. Device according to one of the preceding claims, characterized characterized in that they are of a hermetically sealed lid completed, in particular under vacuum or a protective or inert gas atmosphere. Device according to one of the preceding claims, characterized characterized in that they solder pads for connection to a high-frequency circuit, for example with the so-called flip-chip technology, has.