EP2510532B1 - Micro-electro-mechanical switch for switching an eletrical signal, micro-electro-mechanical system, intgrated circuit and method for producing an integrated circuit - Google Patents

Description

The invention relates to a microelectromechanical system. Furthermore, the invention relates to an integrated circuit with such a micro-electro-mechanical system and a method for producing an integrated circuit.

A microelectromechanical system of the Applicant is z. B. from the WO 2009/003958 known.

An electromechanical microswitch, as used in the US 6,529,093 can be used for switching a radio frequency signal, in particular in the GHz range. In particular, for microelectronic circuits that are clocked at peak frequencies in the GHz range, it is extremely useful to have electromechanical microswitches that allow selected electrical connections to be selectively turned on and off. In the above US 6,529,093 a micromechanical switch is described which consists of a polysilicon cantilever and which is driven by an electrode arrangement to which an electrical potential is applied. In addition to the electrode arrangement for driving the cantilever is there a second electrode arrangement is provided for switching the RF signal. At least one of the electrodes of an electrode pair is provided with a dielectric layer. The cantilever can also be designed as a bridge clamped on both sides. The necessary for the realization of the micro-switch layer structure consists of partially applied layers of a dielectric, conductive materials and polysilicon. Also in the US 6,639,488 describes an RF microswitch, the layer structure is characterized by applying various dielectric and electrically conductive layers. Although both of these documents use fabrication methods that are to be described as CMOS compatible, they require steps to fabricate the microswitches that are not required in the fabrication of microelectronic circuits.

In particular, in circuits that are manufactured with the dominant in the semiconductor industry CMOS technology and find their use in wireless data transmission and communication, often electromechanical switches are used, which can not be integrated together with electronic circuits on a chip. Significantly less expensive and advantageous in terms of further miniaturization, however, would be to provide an electromechanical microswitch, which is also designed in a CMOS-compatible manner, so that a micro-electro-mechanical micro-switch can be made in the course of the production of the microelectronic circuit.

With this in mind, it is important to understand the CMOS manufacturing process generally, which is divided into a front-end of line (FEoL) and a back-end of line (BEoL) area. While the process steps of the FEoL range are concerned with the production of the transistors directly on the surface of the silicon substrate, in the BEoL range, the transistors are connected to one another by electrical lines. In particular, such compounds are fabricated from the patterning of horizontal metal planes and vertical lines (so-called vias) embedded in electrically insulating layers between the horizontal metal planes. Now the processes carried out in the two areas FEoL and BEoL differ considerably in their thermal budget, in particular in the amount and duration of the process temperatures used. Very high process temperatures occur in the FEoL range, which are no longer reached in the BEoL range, in order not to destroy the complex transistor structures by interdiffusion processes.

As explained above, the abovementioned solutions realize an electromechanical microswitch based on silicon, the production of which must take place in the context of the FEoL processes. From a process engineering point of view, however, the production of an electromechanical microswitch would be much more advantageous in the field of BEoL.
In the US 6,667,245 A method for manufacturing a MEMS RF switch is described in which vias are used as design elements of a switch in the BEoL process. The document DE 10 2006 061 386 shows a MEMS switch according to the preamble of claim 1.

• einen auf dem Substrat, insbesondere Siliziumsubstrat, angeordneten Mehrebenen-Leitbahnschichtstapel, dessen Leitbahnen über elektrisch isolierende Schichten gegeneinander isoliert und über Via-Kontakte elektrisch miteinander verbunden sind, insbesondere auch mit elektrischen Schaltungen, die auf/in dem Substrat oder dergleichen. angebracht sein können,
• den in einer Ausnehmung des Mehrebenen-Leitbahnschichtstapels integrierten elektromechanischen Schalter mit einer Kontaktschwinge, einem Gegenkontakt und wenigstens einer Antriebselektrode für die Kontaktschwinge, wobei die Kontaktschwinge, der Gegenkontakt und die wenigstens eine Antriebselektrode jeweils Teil einer Leitungsebene des Mehrebenen-Leitbahnschichtstapels ist.

Das mikroelektromechanische System (MEMS) ist insbesondere zur Schaltung eines elektrischen Signals in Form eines Radiofrequenz-Signals als radiofrequenzmikroelektromechanisches System (RFMEMS), insbesondere zur Schaltung von hochfrequenten Signalen im GHz-Bereich ausgelegt.At this point, the invention begins, whose task is to provide a device for switching an electrical signal and a method for producing the device, which are designed so that a production can be carried out CMOS process compatible in the BEoL range. In particular, the device should be suitable for the switching of signals, in particular of radio-frequency signals, in the GHz range.
With regard to the device, the object of the invention is achieved by means of a microelectromechanical system (MEMS) with an electromechanical microswitch for switching an electrical signal, in particular a radio frequency signal (RFMEMS), in particular in the GHz range, which comprises:

• a multi-level interconnect layer stack arranged on the substrate, in particular a silicon substrate, whose interconnects are insulated against one another via electrically insulating layers and electrically connected to one another via via contacts, in particular also with electrical circuits which are on / in the substrate or the like. can be attached
• the electromechanical switch integrated in a recess of the multilevel interconnect layer stack with a contact rocker, a mating contact and at least one drive electrode for the contact rocker, wherein the contact rocker, the mating contact and the at least one drive electrode is each part of a line level of the multilevel interconnect layer stack.

The microelectromechanical system (MEMS) is designed in particular for the purpose of switching an electrical signal in the form of a radio-frequency signal as a radio-frequency microelectromechanical system (RFMEMS), in particular for the purpose of switching high-frequency signals in the GHz range.

The invention also leads to the integration of an electronic circuit with a microelectromechanical system, wherein preferably the electronic circuit is implemented in the form of an integrated CMOS circuit for achieving the object.

• Herstellen der integrierten Schaltung in einem FEoL-Prozess mit einer Vielzahl von elektronischen Schaltelementen, und
• elektrisches Kontaktieren der elektronischen Schaltelemente in einem BEoL-Prozess, wobei erfindungsgemäß der elektromechanische Mikroschalter in einem BEoL-Prozess in einer Ausnehmung des Mehrebenen-Leitbahnstapels integriert wird und die Kontaktschwinge, der Gegenkontakt und die wenigstens eine die Kontaktschwinge aktivierende Antriebselektrode jeweils Teil einer Leitungsebene des Mehrebenen-Leitbahnschichtstapels ist.

Regarding the method, the object is achieved by the invention by means of a method of the type mentioned above, wherein the production of the integrated circuit takes place in a CMOS manufacturing process, comprising the steps:

• Producing the integrated circuit in a FEoL process with a plurality of electronic switching elements, and
• electrically contacting the electronic circuit elements in a BEoL process, wherein according to the invention the electromechanical microswitch is integrated in a recess of the multilevel interconnect stack in a BEoL process and the contact rocker, the mating contact and the at least one contact rocker activating the drive electrode each part of a line level of the multilevel Conductive layer stack is.

The invention is based on the consideration that previously chosen approaches for the realization of a microelectromechanical switch based on silicon or of the bulk material of silicon are not suitable for representing a microelectromechanical switch CMOS-compatible in a BEoL range. The invention has recognized that it is possible to advantageously integrate an electromechanical microswitch in a BEoL range by suitable choice of the microswitch materials by utilizing the layer sequence used for the connection of the electronic components. The invention has also recognized that with the process technologies available in recent years, it is indeed feasible to integrate or execute suitable electromechanical microswitches in microelectromechanical systems, such as, in principle, e.g. B. off WO 2009/003958 is known. Applicants' electromechanical system technologies have dealt with the elaboration of mechanically movable structures from the bulk material, in particular from silicon wafers.

The use of a layer sequence for the design of the electromechanical microswitch leads according to the invention to an advantageous embodiment of the individual functional elements of the electromechanical microswitch, such as the contact rocker, the mating contact and the drive electrodes for the contact. The contact rocker is advantageously carried out elastically movable and conductive. The mating contact is advantageously carried out at a distance to the contact rocker, in particular in the form of a solid and rigid mating contact socket.
The operation of the microswitch within the microelectromechanical system is preferably such that by means of one or more provided drive electrodes, based on the surface of the z. B. silicon substrates under or above the contact rocker can be attached, the contact rocker is movable. This is done by applying an electrical potential between the at least one drive electrode and the contact rocker, so that due to electrostatic forces an elastic movement of the contact rocker takes place and the capacitive coupling is changed over the distance between the mating contact and contact rocker. This leads to the switching of an electrical signal that can be performed on the mating contact and / or the contact rocker. Advantageously, the contact rocker may be grounded and the mating contact between different potentials to be performed - with decreasing distance between contact rocker and mating contact thus takes place a capacitive coupling of the signal line to ground.

The invention provides that the mating contact (socket) has a metal-insulator-metal (MIM) structure on a distal end facing the contact rocker (actuator). This makes it possible to use such an MIM structure, inter alia, to protect the mating contact as well as to improve the contact performance with extension of the frequency range. In addition, the switching behavior of the electromechanical microswitch can be advantageously designed.
In addition, it can be provided that the contact swing moving drive electrode (as part of a line level of the conductor layer stack) on a side facing the contact rocker has a structure of nubs with dielectric material. These can, as recognized by the training, within a Produce process step for exposing an electrode of a conductive path, without a separate process step would be required to represent the structure of nubs. In principle, the structure of nubs is advantageously suitable for avoiding unintentional contacting between the drive electrode and the contact rocker - that is, an undesired short circuit. In addition, the nubs are suitable for supporting the drive electrode in the region of the drive electrode or to represent a stop for the contact rocker. The process step for producing the dimples can take place, for example, in the context of a wet etching step and optionally a subsequent CO ₂ drying process. Further process steps for displaying the nub structure are not required. With regard to the structure of dimples with dielectric material, it has proven to be particularly advantageous in the context of the manufacturing method that the dielectric material is formed in the form of an oxide of the material of a line level of the multilevel interconnect layer stack, in particular by wet-chemical etching.

Further advantageous developments of the invention can be found in the dependent claims and specify in particular advantageous ways to realize the above-described concept in the context of the task and in terms of the above-mentioned and other advantages.

It has proved to be particularly advantageous that the contact rocker as a cantilever, z. B. is formed in the form of a one-sided spring or bridge. A bridge or spring (cantilever), for example, be provided with comparatively well-formed elastic properties in order to make the elastic movement of the contact rocker for switching the signal advantageous. For this purpose, the contact rocker can be provided with recesses. In particular, the contact rocker may be provided for integrating the electromechanical microswitch with an electronic circuit on a chip by structuring a line plane of the multilevel interconnect layer stack with one or more end fixing fixings. A fixing suspension are designed, for example, as a boom of the contact rocker, It is advantageous to arrange the boom at an angle not equal to 0 ° or 180 ° to each other to lock degrees of freedom in the mobility of the contact rocker and only allow movement in the switching direction. Have proven to be advantageous in each case two end arms of the contact rocker for the formation of Fixieraufhängungen, which are at an angle of approximately 90 ° to each other.

Particularly advantageously, the contact rocker has at least one distinguishable from the contact zone attractive area. The contact zone is assigned to the mating contact and serves for the capacitive coupling of contact rocker and mating contact. The at least one attractive region, on the other hand, is assigned to the activating drive electrode and serves to activate, i. H. Applying force to the contact rocker to set the contact rocker in motion.

The contact rocker is advantageously formed by structuring a line level of the multilevel conductor track stack, and is preferably made of metallic material such as aluminum. The representation of the contact rocker from a metallic line level of the multilevel interconnect stack can be advantageously integrated in the context of the BEoL process.

Basically, one or more of the contact rocker activating and / or counteracting drive electrodes may be provided, which are advantageously formed from the structuring of a line level of the multi-level conductor track stack. For example, within the scope of a particularly preferred development, a drive electrode activating the contact rocker can be arranged below the contact rocker with respect to the surface of the silicon substrate. This development means that the closing of the switch, the contact rocker is brought into a "down state" and is brought to open the switch in an "open state". To improve the switching behavior, a further contact electrode activating and / or counteracting drive electrode may be arranged at a distance relative to the surface of the silicon substrate over the contact rocker, additionally or alternatively. In the event that the remote from the substrate disposed above the contact rocker drive electrode is provided in addition to the lower substrate-side drive electrode, the upper drive electrode serves as a retraction electrode. Thereby, the movement of the contact rocker from the "down state" to the "up state" can be accelerated.

Preferably, the different levels of the multi-level interconnect layer stack z. B. made of aluminum at the same time as a carrier layers for the contact rocker, the mating contact, the activating and / or counteracting drive electrodes of the electromechanical microswitch. In a particularly preferred manner, the metallic line levels can be coated on at least one side, preferably on both sides. In a particularly preferred development, this applies to all metallic line levels forming the electromechanical microswitch to, at least in the region of the contact, the mating contact, the activating drive electrode and the counteracting drive electrode. In the present case, the coating is advantageously formed by one or more layers with TiN and / or Ti and / or AICu. In particular, a double layer of TiN-Ti has been found to be advantageous or a sandwich of TiN-AlCu-TiN.

In a preferred embodiment, the base of the mating contact is formed with insulating material. It has been shown that when producing the multilevel interconnect layer stack, the insulating material, for example a dielectric material, preferably Si ₃ N _4, which is applied between the line levels can also advantageously be used to form the base of the mating contact. In a particularly advantageous manner, the base of the mating contact is formed from a sequence of a first metallic line level, an insulating material set thereon and a second metallic line level.

The metallic layer of the mating contact has a particularly advantageous switching behavior with respect to the contact with the contact surface of the contact rocker.

• einer der Basis zugewandten Barriere-Schicht aus leitfähigem Material, insbesondere metallischem Material;
• einer der Kontaktschwinge zugewandten leitfähigen Kappe am distalen Ende;
• einer dazwischen liegenden dielektrischen Schicht.

Further, the attachment of an MIM structure (metal-insulator-metal structure) on a base to form a distal end of the mating contact is advantageously provided. In particular, it has proved to be advantageous for the MIM structure to consist of:

• a base-facing barrier layer of conductive material, especially metallic material;
• one of the contact swing facing conductive cap at the distal end;
• an intermediate dielectric layer.

The barrier layer is advantageously used as protection between a signal-conducting metal layer attached on the basis of the mating contact and the dielectric layer of the MIM structure. The cap of the MIM structure advantageously serves to protect the mating contact. Advantageously, in a modification of this development, the cap is designed with a higher layer thickness than that of the barrier layer. This ensures that in a "down state" of the contact a reliably defined and comparatively low capacity is realized. To further improve the contact behavior can the conductive cap, in particular metallic cap, also be formed in the form of a metal layer structure, which can be realized as needed. The barrier layer may advantageously be of the same type as the cap. The insulating dielectric layer layer of the MIM structure is advantageously a Si ₃ N ₄ .

In a particularly preferred manner, the contact rocker and / or the cap can be formed from a metallically conductive layer or layer combination containing titanium nitride and / or Ti-based material, in particular consisting of a titanium nitride material or pure titanium. In particular, in a "down state" of the electromechanical microswitch, a titanium nitride titanium nitride (TiN-TiN) contact or TiN-Ti contact has been found to be relatively resistant.

Thus, the contact rocker and / or the cap can be formed from one or more layers Ti, TiN and / or AICu. These combinations of materials have proven to be easy to process, highly resistant in an "off-state" and advantageous in terms of switching performance. A sandwich structure of TiN-AlCu-TiN has proven to be particularly advantageous for the embodiment of the contact rocker and the cap. It is advantageous that the entire line levels of the conductor layer stack are performed in this sandwich structure, including in the areas where structured line levels are used for the electrical connection of electronic circuits.

In the context of a further preferred development, a distance of a contact arrangement activating the contact armature (drive electrode) is selected to be greater than a distance of the contact rocker to the mating contact. In other words, a distance between mating contact and contact is less than between a drive electrode and contact rocker. A pull-in effect, i. An overshoot of the contact rocker from the "up state" in the "down state" when closing the switch is thereby counteracted advantageous.

In a particularly preferred embodiment, the distance between the mating contact and the contact zone of the contact rocker and the capacity of the MIM structure on the mating contact can be dimensioned such that over the entire distance in the course of movement of the contact between an "open state" and "Ab-state" results in a largely proportional capacity curve as a function of the activation voltage between the drive electrode and contact rocker. The electromechanical Microswitch can be used according to this development advantageously as variable capacity with defined control voltage curve.

Embodiments of the invention will now be described below with reference to the drawings. This is not necessarily to scale the embodiments, but the drawing, where appropriate for explanation, executed in a schematized and / or slightly distorted form. With regard to additions to the teachings directly recognizable from the drawing reference is made to the relevant prior art. It should be noted that various modifications and changes may be made in the form and detail of an embodiment without departing from the general idea of the invention. The disclosed in the description, in the drawing and in the claims features of the invention may be essential both individually and in any combination for the development of the invention. In addition, all combinations of at least two of the features disclosed in the description, the drawings and / or the claims fall within the scope of the invention. The general idea of the invention is not limited to the exact form or detail of the preferred embodiment shown and described below or limited to an article which would be limited in comparison to the subject matter claimed in the claims. For the given design ranges, values within the stated limits should also be disclosed as limit values and be arbitrarily usable and claimable. For simplicity, the same reference numerals are used below for identical or similar parts or parts with identical or similar function.

• Fig. 1 eine perspektivische Darstellung eines elektromechanischen Mikroschalters gemäß einer besonders bevorzugten Ausführungsform für ein MEMS;
• Fig. 2 eine schematische Schnittdarstellung des elektromechanischen Mikroschalters zur Verdeutlichung des Aufbaus der Kontaktschwinge, des Gegenkontakts und der aktivierenden Antriebselektrode in der bevorzugten Ausführungsform;
• Fig. 3 eine schematisch dargestellte Draufsicht auf den elektromechanischen Mikroschalter der Fig. 1 als Teil des MEMS zur Verdeutlichung der Funktion und der Signalwege;
• Fig. 4A, 4B, 4C ein Ersatzschaltbild des Mikroschalters der Fig. 3 mit dargestellten Signalwegen;
• Fig. 5, 6 eine Seitenansicht einer ersten bevorzugten Ausführungsform eines MEMS mit einem elektromechanischen Mikroschalter unter Zuordnung der Kontaktschwinge, des Gegenkontakts und der Antriebselektrode zu den einzelnen Leitungsebenen des Mehrebenen-Leitbahnstapels des MEMS bzw. mikroelektromechanischen Systems für Radiofrequenz-Signale (RFMEMS) sowie eine abgewandelte bevorzugte Ausführungsform, welche zusätzlich mit einer Rückzieh-Elektrode versehen ist;
• Fig. 7 eine zweite bevorzugte Ausführungsform eines MEMS mit einer speziell bevorzugten Schichtabfolge der Leitungsebenen des Mehrebenen-Leiterbahnschichtstapel des MEMS;
• Fig. 8A, 8B, 8C, 8D den elektromechanischen Mikroschalter der Fig. 1 mit einer symbolisch dargestellten Struktur aus Noppen mit dielektrischem Material (A) sowie Elektronen-Mikroskopieaufnahmen in unterschiedlichen Vergrößerungen (B), (C), (D) der Noppenstruktur;
• Fig. 9 eine schematische Darstellung des elektromechanischen Mikroschalters ähnlich wie Fig. 2 mit symbolisch dargestellter Bewegungsrichtung der Kontaktschwinge zum Gegenkontakt und symbolisch dargestellter kapazitiven Kopplung sowie Abstandsbereichen zur Realisierung einer definiert schaltbaren Region einer kapazitiven Kopplung;
• Fig. 10 eine beispielhafte Radiofrequenzcharakterisierung eines elektromechanischen Mikroschalters der bevorzugten Ausführungsform bei 24 GHz hin-sichtlich des Schaltverhaltens;
• Fig. 11 die Messanordnung zur Charakterisierung des MEMS der Fig. 10 mit elektromechanischen Mikroschalter.

Further advantages, features and details of the invention will become apparent from the following description of the preferred embodiments and with reference to the drawing, which shows in:

• Fig. 1 a perspective view of an electromechanical microswitch according to a particularly preferred embodiment of a MEMS;
• Fig. 2 a schematic sectional view of the electromechanical micro-switch to illustrate the structure of the contact rocker, the mating contact and the activating drive electrode in the preferred embodiment;
• Fig. 3 a schematic plan view of the electromechanical micro-switch of Fig. 1 as part of the MEMS to clarify the function and the signal paths;
• FIGS. 4A, 4B, 4C an equivalent circuit diagram of the microswitch the Fig. 3 with illustrated signal paths;
• Fig. 5, 6 a side view of a first preferred embodiment of a MEMS with an electromechanical microswitch assigning the contact rocker, the mating contact and the drive electrode to the individual conduction levels of the multi-level interconnect of the MEMS or microelectromechanical system for radio frequency signals (RFMEMS) and a modified preferred embodiment, which additionally provided with a retraction electrode;
• Fig. 7 a second preferred embodiment of a MEMS with a particularly preferred layer sequence of the line levels of the multi-level interconnect layer stack of the MEMS;
• Fig. 8A . 8B . 8C . 8D the electromechanical microswitch the Fig. 1 with a symbolically represented structure of dimples with dielectric material (A) and electron micrographs at different magnifications (B), (C), (D) of the dimpled structure;
• Fig. 9 a schematic representation of the electromechanical micro-switch similar Fig. 2 with symbolically represented movement direction of the contact rocker to the mating contact and symbolically represented capacitive coupling and distance ranges for realizing a defined switchable region of a capacitive coupling;
• Fig. 10 an exemplary radio frequency characterization of an electromechanical microswitch of the preferred embodiment at 24 GHz in terms of switching behavior;
• Fig. 11 the measuring arrangement for characterizing the MEMS of Fig. 10 with electromechanical microswitch.

The in Fig. 1 to Fig. 4C micro-switch shown in detail, according to the concept of the invention, as in a first embodiment in Fig. 5 and a modification thereof in Fig. 6 or in a second embodiment of the MEMS as shown in FIG Fig. 7 is illustrated by structuring the conduction levels of a multi-level wiring layer stack.

In this respect, the show Fig. 1 to Fig. 4C as well as the example of FIGS. 8A to 8D and Fig. 9 Detail sections of a preferred embodiment of a MEMS.

The in Fig. 1 shown electromechanical microswitch 1 is composed of a cantilevered, elastically movable, conductive contact rocker 10, a mating contact 20 and a contact rocker 10 activating the drive electrode 30. The contact rocker 10 is presently formed in the form of a bridge 14, a contact zone 13 and a first attractive Area 11 and a second attractive area 12 has. The attractive regions 11, 12 are each assigned to a first and second part 31, 32 of the activating drive electrode, that is arranged opposite one another. The distal end 23 of the mating contact 20 is arranged opposite the contact zone 13 of the bridge 14. The contact rocker 10 has at the end of the bridge 14 in each case two arms 15A, 15B and 16A, 16B, which fix the bridge 14 at the end region of the attractive areas 11, 12. For this purpose, the arms 15 B, 16 B and 15 A, 16 A run obliquely from a common fixed point in different directions and are with their attachment portions 15, 16 in the semiconductor material of an in Fig. 11 symbolically represented CMOS chips.

Upon application of an electrical potential between the drive electrode 30 and the contact rocker 10 this is caused to an elastic movement, which changes a capacitive coupling of the contact zone 13 of the contact rocker 10 to the mating contact 20 and thus suitable for switching an electrical signal S in the interconnect 112.

Fig. 2 shows the electromechanical micro-switch along the section line II-II in Fig. 1 , wherein the structure of the tracks for forming the contact rocker, 10 of the mating contact 20 and the drive electrode 30 is more apparent and described below. Fig. 3 and FIGS. 4A, 4B, 4C explain the function of the microswitch.

How out Fig. 2 and Fig. 3 As can be seen, the electromechanical microswitch 1 of the present embodiment is characterized in that the attractive regions 11, 12 of the contact rocker 10 are separated from the contact zone 13 of the contact rocker 10 by slots 18 or the contact zone 13 separately between the attractive region 11, 12th is arranged. In this way, separate area 43 influencing the signal S is formed, the size of which is determined essentially by the contact zone 13 and the flat distal end 23 of the mating contact 20. The area 43 is thus separated from the areas 41, 42 transmitting electrical forces between in each case an attractive area 11, 12 or a part 31, 32 of the activating drive electrode 30.

As an equivalent circuit is shown schematically in Fig. 4A with (I) an "on state" of the electromechanical microswitch 1, in which a radio frequency signal passes through the mating contact 20 from P1 to P2, without the capacitance between the mating contact 20 and the contact zone 13 being able to transmit the signal S to influence significantly. With (II) is in Fig. 4B Symbolically, the signal terminal of an RF signal for the "down state" of the contact 10 shown - in the present case finds the RF signal due to the now existing capacitive possibly. Contacting coupling of mating contact 20 and the contact zone 13 its way to a ground terminal, which at the Contact rocker 10 is present.

In order to promote or permit elastic movement of the contact rocker 10 in a preferred dynamic range, the contact rocker 10 is as shown in FIG Fig. 1 can be seen, provided with a number of recesses 17 or slots 18, which reduce the moment of resistance of the spring action of the contact arm 10. The slots 18 also serve the above-described separation between attractive areas 11, 12 and the contact zone 13 of the bridge 14. In the case of the "up-state" of the electromechanical microswitch 1 - ie in the case of low capacitive coupling with the transmitted signal is the capacity between mating contact 20 and the contact rocker 10 approximately between 50 to 500 fF. In an "off state" of the electromechanical microswitch 1, the capacitance between mating contact 20 with an MIM structure at the distal end 23 and the contact zone 13 is about 1 to 10 pF.

The out Fig. 2 schematically apparent preferred construction of the contact rocker 10, the mating contact 20 and the drive electrode 30 of the electromechanical microswitch 1 results according to the specification of a MEMS structure according to the concept of the invention the structuring of line levels of a multilevel interconnect layer stack, which is applied to the surface of a silicon substrate. The contact rocker 10 is in this case designed as a structuring of the line level M3 (3rd level of the multilevel interconnect layer stack), wherein the line level M3 in turn of a sandwich structure consists of a central metal layer and this covering cover layers 19, which are present on both sides of the metal layer, such as aluminum, attached. The cover layers 19 are formed in the present embodiment of a titanium nitride based material, in this case TiN. In addition to advantageous mechanical and protective properties, TiN also has excellent properties with regard to the contact behavior of the contact zone 13 with respect to the mating contact 20. The bridge 14 is therefore correspondingly present Fig.2 formed as a three-layer membrane, which is largely stress-free or particularly well tension compensated by the sandwich arrangement in a particularly advantageous manner. In embodiments, the bridge 14 or the contact rocker 10 can also be used as a membrane with more than three, for example as in Fig. 7 be formed from five layers.

The drive electrode 30 is formed in each of its parts 31, 32 by structuring the line level M1, which is also formed in the embodiment of aluminum and a cover layer 39 also made of TiN.

The mating contact 20 in the present case has a base 21 made of a layer of a non-conductive or insulating material Si ₃ N ₄ . Further layers are applied to the base 21 by forming the line level M2 in accordance with the contour of the mating contact, since the line level M2 again consists of a sandwich structure of an aluminum carrier layer with intermediate layers 22, for example of TiN, applied on both sides. On the surface of the distal end 23 of the mating contact 20 is a sequence of first of a base facing barrier layer 24 of conductive material - in the present case metallic TiN - thereon a dielectric layer 25 and finally arranged a contact rocker 10 conductive cap 26. The MIM sequence of conductive layer 24, dielectric layer 25 and conductive cap 26 is presently formed as a special protection of the mating contact 20, to improve the contact properties to the contact 10 and to form a defined switching capacity. In the present case, the protective conductive cap 26 is formed of a thin metal layer of TiN attached directly to the dielectric layer 25 by a corresponding patterning process. However, in a modified embodiment, not shown here, the cap 26 may also consist of a layer sequence of be formed of different metallic materials. At least the surface, which is formed by the cap 26, thereby projects laterally beyond the surface of the contact rocker 10, as for example in Fig. 3 is recognizable. This ensures a particularly reliable contact. The dielectric layer 25 for forming the MIM structure may be basically formed of any suitable dielectric material. In addition, the dielectric layer itself is comparatively thin in order to obtain a precisely defined capacitance Cs influencing the signal path in the "down state". The concept presented here thus provides that in an "off-state" the RF signal is influenced only by the capacity defined by the MIM structure, and indeed largely independent of the contact resistance between the contact zone 13 and the cap 26.

Regarding Fig. 5 According to the present invention, the electromechanical microswitch 1 as part of a MEMS 100 is completely formed according to the inventive concept in a BEoL process (back-end of line process) of a standard CMOS-BiCMOS process. As a result, a complete integration of the electromechanical microswitch together with electronic components in a chip is possible. The MEMS100 has a multilevel interconnect layer stack 102 arranged on a substrate 101, whose line levels M1 to M5 are partially structured in the area region 103 in order to form interconnects 111 to 115 for connecting the electronic components. The line levels M1 to M5 are insulated from one another by electrically insulating layers 103 and connected to one another via via contacts 104. In the present case, the electromechanical microswitch 1 is integrated in a recess 105 of the multilevel interconnect layer stack 102. In this case, as can be seen from the synopsis of the line levels M1, M2, M3, the contact rocker 10, the mating contact 20 and the contact rocker activating drive electrode 30 are each a structured part of a line level of the multilevel interconnect layer stack 102. During the on the substrate 101 - eg Si - Arranged portion of the transistor circuits 106 and / or 108 is made in a FEoL process section, the interconnection thereof with each other and with the electromechanical microswitch 1 in the multi-level interconnect layer stack 102 in a BEoL process section. This direct, low-inductance line connection is particularly advantageous at very high frequencies of the RF signal. The interconnects 111 to 115 are presently made of an aluminum material, the vias 104 of a tungsten material and the insulating or other protective layers may be formed of a Si ₃ N ₄ material.

Fig. 6 shows a modified embodiment in a comparable view as Fig. 5 , Shown is a modified microelectromechanical system 100 in which identical reference numerals are used for identical or similar parts or parts of identical or similar function for the sake of simplicity. In addition to the arrangement of the contact 10 and mating contact 20 and the activating drive electrode 30 is in the electromechanical system 100 of Fig. 6 a further contact electrode 50 counteracting the contact 10 is provided as a return electrode. The return electrode is present in one of Fig. 5 integrated lead level M4 of the multilevel interconnect layer stack 102 integrated. As indicated by the arrows in the force transmitting areas 41, 42 (FIG. Fig. 3 ), can be accelerated by the return electrode, the contact rocker 10 of an "Ab-state" bring in an "open state", which significantly increases the switching time of the electromechanical microswitch 1 in the MEMS 100. This makes it possible to switch radio frequencies even in a high GHz range without problems.

It should be understood that the assignment of the contact rocker 10, the activating drive electrode 30 and the mating contact 20 to the line levels M3, M1, M2 in the present embodiments is not restrictive in the present embodiments, but can be variably selected. For example, the mating contact 20 can also be arranged in a M3 metal layer and the activating drive electrode 30 in a line plane M2. In principle, however, the contact rocker 10 could be arranged with respect to the surface of the silicon substrate 101 below an activating drive electrode or a mating contact. Such embodiments are not explicitly shown here. In addition, the assignment of the contact rocker 10, the counter electrode 20 and the drive electrode 30 of the electromechanical microswitch 1 to the line levels M1 to M5 of the multilevel interconnect layer stack 102 must not be sequential - rather, it is also possible that between the contacts arranged further metal layers no direct Function with the electromechanical micro-switch have.

Fig. 7 ₂ shows a second embodiment of a MEMS 200 with an electromechanical microswitch 1 integrated according to the concept of the invention. The MEMS in turn has a multilevel interconnect layer stack 202 arranged on a substrate 201, which is covered by a SiO ₂ layer 206, for example for attaching applications , The region 206 and / or 208 for transistor circuits or the like is manufactured in a FeOL process section. In a BEoL process (BEoL) the Line levels M1 to M5 and therefrom by structuring z. B. formed by etching the interconnects 211, 212, 213, 214, 215 and connected via via contacts 204 suitably connected to each other. Between the line levels M1 to M5 of the interconnect layer stack 202 alternately electrically insulating layers 203 are arranged. The insulating layers 203 are presently made of Si ₃ N ₄ , which can be easily processed in a BEoL process. As already on the basis of Fig. 5 and Fig. 6 1, the microswitch 1 is integrated in a recess 205 of the multilevel interconnect layer stack 202. The contact rocker 10, the mating contact 20 and the drive electrodes 30 for the contact rocker 10 are presently formed by structuring the line levels M1 to M5. In the embodiment of the Fig. 7 the line levels M1 to M5 are formed in a particularly preferred manner as a metallic carrier layer, for example made of aluminum and double-sided bilayers, The double layer comprises in each case a layer of Ti and a layer of TiN. On a side of the line levels M1 to M5 facing the substrate 201, the metallic carrier layer, for example made of aluminum, is initially coated directly with a first layer of TiN, which in turn is coated with a second layer of Ti. On the side of the line levels M1, M2, M3, M4, M5 facing away from the substrate 201, the cover layer embodied as a double layer is not mirrored, that is, first the metallic carrier layer z. As aluminum coated with Ti and then applied an external TiN layer.

In the present case, the mating contact 20 is initially constructed as a base with a base which has a layer sequence corresponding first to the line level M1, then an insulating dielectric layer 21 and then the correspondingly structured line level M2. In this case, the topmost TiN layer of the line level M2, based on the Si substrate, at the same time forms the lower end layer of the MIM structure, which is arranged on the mating contact 20. The MIM structure further comprises a dielectric layer 25, which consists for example of TiN-Si ₃ N ₄ , and a further TiN-layer as a metallic cap 26. The details of the MIM structure is shown in enlarged detail B of FIG Fig. 7 shown. It can be seen that the layer sequence 24, 25, 26 of the MIM layer consists of a layer sequence of TiN-Si ₃ N ₄ and TiN. This also has the consequence that when forming the capacitive coupling between the contact rocker 10 and the mating contact 20, the substrate facing the lower Ti layer of the line level M3 and facing away from the substrate TiN layer of the MIM structure face each other. It has been shown that a potential formation between Ti layer on the one hand and TiN layer on the other hand in an electromechanical micro-switch of the embodiment according to Fig. 7 is particularly advantageous.

Fig. 8A shows an electromechanical micro-switch 1, in which on one of the contact rocker 10 side facing the activating drive electrode 30 is a structure 33 of nubs 34, which in the enlarged views of Fig. 8B , C, D are closer to recognize. These nubs, also referred to as dielectric islands or support posts, can be produced integrated in a conventional BEoL process without an additional process step, in particular without an extra mask. For this purpose, a preferred method in the present case provides that the nub structure 34 remains as the remainder of a wet-chemical etching step and a subsequent CO ₂ drying process. The knobs prevent the contacting contact between the contact zone 13 of the contact arm 10 on the one hand and the activating drive electrode 30 on the other. As a result, a short circuit between the contact rocker 10 and the drive electrode 30 is advantageously avoided.

Fig. 9 illustrates the switching function of the electromechanical microswitch 1 on the basis of the schematic representation, as already in Fig. 2 was shown. In synopsis with Fig. 3 3, the contact rocker 10 in the direction of the mating contact 20 due to the triggered by the drive electrode 30 force in the power attractive areas 41, 42, the capacitive coupling 4 between the contact zone 13 and the distal end 23 of the mating contact 20 is changed. The contact rocker 10 and the drive electrodes 30 are electrically connected via the correspondingly structured line level M3 and vias to the electronic circuit parts of the MEMS. The capacitive coupling between the ground potential contact arm 10 and the mating contact 20 connected to the RF signal path becomes substantially only by the distance between the contact zone 13 and the cap 26 and the dielectric layer 25 formed as an MIM structure of the mating contact 20 defined. When the contact zone 13 contacts the cap 26 of the MIM structure on the mating contact 20 in an "off state" of the electromechanical microswitch 1, an effective contact between the contact zone 13 with the covering layer 19 of Ti and the cap 26 of TiN on the mating contact 20 are produced. This allows an in Fig. 4A, Fig. 4B schematically illustrated circuit of an RF signal. The distance between the cap 26 on the mating contact 20 and the contact zone 13 of the contact rocker 10 is smaller than the distance between the activating drive electrode 30 and the contact rocker 10, whereby a relatively large activation voltage (pull-down voltage) between the activating drive electrode 30th and the contact arm 10 is needed. The cap 26 of TiN is automatically used as a stop layer for used the contact zone 13 of the contact arm 10, as one of Fig. 11 apparent height difference between the mating contact 20 and the drive electrode 30 consists.

Fig. 10 shows an exemplary measurement of the switching behavior of the electromechanical microswitch at 24 GHz over the distance A accordingly Fig. 9 , The measuring arrangement for the electromechanical microswitch is in Fig. 11 shown. At 24 GHz, this results in an attenuation of the RF signal by -25 dB and a mechanically stable behavior with an activation voltage of up to 30 V without unintentional blocking or adhesion of the contact 10 on the mating contact 20 or the drive electrode 30 is detected. The so-called pull-in voltage - ie the voltage at which the switch has moved from an "on state" to an "off state" - is in the present case about 17 to 18 V. In the case of a working range of the activation voltage present between 10 -15 V is a nearly linear course of the capacitance between the counter electrode 20 and the contact rocker 10 determine what is advantageous for an application of the electromechanical microswitch invention as adjustable capacity. A corresponding circuit arrangement is the Fig. 4C refer to.

The maximum DC voltage difference between the mating contact 20 and the contact rocker 10 is correspondingly lower than the activation voltage (pull-down voltage) between the activating drive electrode 20 and the contact rocker 10.

• einen auf einem Substrat 101, 201 angeordneten Mehrebenen-Leitbahnschichtstapel 102, 202, dessen Leiterbahnen 111-115, 211-215 in verschiedenen Leitungsebenen M1-M5 mit elektrisch isolierende Schichten 103, 203 gegeneinander isoliert und über Via-Kontakte 104, 204 elektrisch miteinander verbunden sind,
• den in einer Ausnehmung 105, 205 des Mehrebenen-Leitbahnschichtstapels 102, 202 integrierten elektromechanischen Schalter 1 mit einer Kontaktschwinge 10, einem Gegenkontakt 20 und wenigstens einer Antriebselektrode 30, 50 für die Kontaktschwinge 10, wobei die

In summary, a microelectromechanical system (MEMS) 100, 200 with an electromechanical microswitch 1 has been described for switching an electrical signal S, in particular a radio frequency signal (RFMEMS), in particular in the GHz range, comprising:

• a multi-level interconnect layer stack 102, 202 arranged on a substrate 101, 201, the interconnects 111-115, 211-215 of which are insulated against one another in different line levels M1-M5 with electrically insulating layers 103, 203 and electrically connected to one another via via contacts 104, 204 are,
• the in a recess 105, 205 of the multi-level interconnect layer stack 102, 202 integrated electromechanical switch 1 with a contact arm 10, a mating contact 20 and at least one drive electrode 30, 50 for the contact rocker 10, wherein the

Contact rocker 10, the mating contact 20 and the at least one drive electrode 30, 50 each part of a line level M1-M5 of the multi-level interconnect layer stack 102, 202 is. Overall, a microelectromechanical system (MEMS) 100, 200 for radio frequency signals (RFMEMS) with an electromechanical microswitch 1, which can be integrated in a BEoL process sequence, has been described in the present case. This is formed in a particularly advantageous manner with a sequence of metal-insulator-metal structure at the distal end 23 of the mating contact 20 and the drive electrode 30 has a on a contact 10 side facing a structure of nubs with dielectric material. This will on the one hand in Fig. 10 achieved particularly advantageous switching behavior and on the other unwanted blocking of the electromechanical microswitch 1 avoided.

Claims (22)

1. A microelectromechanical system (MEMS) (100, 200) with an electromechanical microswitch (1) for switching an electrical signal (S) in particular a radio frequency signal (RFMEMS), in particular in a GHz range, comprising:

   - a multi-level conductive path layer stack (102, 202) arranged on a substrate (101, 201), wherein conductive paths (111-115, 211-215) of the multi-level conductive path layer stack arranged in different conductive levels (M1-M5) are insulated from one another through electrically insulating layers (103, 203) and electrically connected with one another through Via contacts (104, 204),

   - an electromechanical switch (1) which is integrated in a recess (105, 205) of the multi-level conductive path layer stack (102, 202) and which includes a contact pivot (10), an opposite contact (20) and at least one drive electrode (30, 50) for the contact pivot (10), wherein

   the contact pivot (10), the opposite contact (20) and the at least one drive electrode (30, 50) respectively form a portion of a conductive level (M1-M5) of the multi-level layer stack (102, 202), and characterized in that the opposite contact (20) includes a metal-insulator-metal (MIM) structure (24, 25, 26) at a distal end (23) oriented towards the contact pivot (10).
2. The microelectromechanical system (100, 200) according to claim 1, characterized in that the electromechanical microswitch (1) includes a first drive electrode (30) activating the contact pivot and/or a second drive electrode (50) counter-activating the contact pivot (10).
3. The microelectromechanical system (100, 200) according to one of the claims 1 or 2, characterized in that the contact pivot (10) is movable through a drive electrode (30, 50), wherein a capacitive coupling (4) is changed through a distance between the opposite contact (20) and the contact pivot (10) for influencing the electrical signal (S) at least on the opposite contact (20) due to an elastic movement (3) of the contact pivot (10) when applying an electrical potential between the drive electrode (30) and the contact pivot (10).
4. The microelectromechanical system (100, 200) according to one of the claims 1 through 3, characterized in that the conductive contact pivot (10) and/or the opposite contact (20) and/or the activating drive electrode (30) and/or a counter-activating drive electrode (50) of the electromechanical microswitch (1), in particular all of them, include a carrier layer that is formed by a conductive level (M1-M5) of the multi-level conductive path layer stack (102, 202), wherein the carrier layer includes one or plural layers with TiN and/or Ti and/or AlCu at least on one side, preferably on both sides, in particular a double layer TiN - Ti, or in particular a sandwich made from TiN - AlCu - TiN.
5. The microelectromechanical system (100, 200) according to one of the claims 1 through 4, characterized in that the drive electrode (30) activating the contact pivot (10) and/or the drive electrode (50) counter activating the contact pivot (10) of the electromechanical microswitch (1) includes a structure (33) including knobs (34) with dielectric material (25) on a side oriented towards the contact pivot (10).
6. The microelectromechanical system (100, 200) according to claim 5, characterized in that the structure (33) is formed form knobs (34) with dielectric material (25) configured as an oxide of an electrode material of a conductive level (M1-M5), in particular configured as an oxide formed through wet chemical etching.
7. The microelectromechanical system (100, 200) according to one of the claims 1 through 6, characterized in that the contact pivot (10) is elastically movable, in particular cantilevered, preferably includes a contact zone (13) which is part of an elastically movable conductive bridge (14) or of a one- or double sided spring or of a similar cantilever.
8. The microelectromechanical system (100, 200) according to one of the claims 1 through 7, characterized in that the contact pivot (10) of the electromechanical microswitch (1) includes a contact zone (13) and an attractive portion (11, 12), in particular a partition configured as a slot (18) or similar between the portions (11, 12, 13).
9. The microelectromechanical system (100, 200) according to one of the claims 1 through 8, characterized in that the activating drive electrode (30) of the electromechanical microswitch (1) is arranged at a distance (A) on the substrate side below the contact pivot (10).
10. The microelectromechanical system (100, 200) according to one of the claims 1 through 9, characterized in that a counter-activating drive electrode (50) of the electromechanical microswitch (1) is arranged with an offset above the contact pivot (10) on a side oriented away from the substrate.
11. The microelectromechanical system (100, 200) according to one of the claims 1 through 10, characterized in that a first drive electrode (30) of the electromechanical microswitch (1) is configured as an activating drive electrode and a second drive electrode (50) is configured as a counter-activating drive electrode wherein the first drive electrode and the second drive electrode are tuned to one another and configured to impact the contact pivot (10).
12. The microelectromechanical system (100, 200) according to one of the claims 1 through 11, characterized in that the drive electrode (30) provided for moving the contact pivot (10) and/or another counter-activating drive electrode (50) of the electromechanical microswitch (1) are formed with a metal, in particular Al based carrier layer of a conductive level (M1-M5) of a conductive path layer stack (101, 102).
13. The microelectromechanical system (100, 200) according to one of the claims 1 through 12, characterized in that the opposite contact (20) of the electromechanical microswitch (1) is formed as a solid pedestal on the substrate (101, 102).
14. The microelectromechanical system (100, 200) according to one of the claims 1 through 13, characterized in that the opposite contact (20) of the electromechanical microswitch (1) includes a base with at least one layer with insulating material (21) and a MIM structure (MIM) (1), including:

    - a barrier layer (24) made from conductive material, in particular metal material, oriented towards the base;

    - a conductive cap (26) oriented towards the contact pivot (10) and arranged at a distal end (23);

    - a dielectric layer (25) arranged there between.
15. The microelectromechanical system (100, 200) according to one of the claims 1 through 14, characterized in that at least one conductive layer of the MIM structure of the electromechanical microswitch (1), in particular a cap (26) and/or a barrier layer (24) is formed from a conductive metal layer or layer combination including a material that is based on titanium nitride and/or titanium.
16. The microelectromechanical system (100, 200) according to claim 14 or 15, characterized in that the at least one conductive layer of the MIM structure of the electromechanical microswitch (1) is made from one or plural layers with TiN and/or Ti and/or AlCu, in particular a double layer TiN - Ti or in particular a sandwich made from TiN - AlCu - TiN.
17. The microelectromechanical system (100, 200) according to one of the claims 14 through 16, characterized in that the dielectric layer (25) of the MIM structure of the electromechanical microswitch (1) is formed from one or plural layers with Si3N4.
18. The microelectromechanical system (100, 200) according to one of the claims 1 through 17, characterized in that a distance (A + B) from the contact pivot (10) of a drive electrode activating the contact pivot (10) is greater than a distance A of the contact pivot (10) from the opposite contact (20).
19. The microelectromechanical system (100, 200) according to one of the claims 1 through 18, characterized in that a distance (A) between the opposite contact (20) and the contact pivot (10) is sized so that over the entire distance (A) in an operating range an approximately linear context is provided between the activation voltage applied to the drive electrode (30) and the contact pivot (10) and the capacity provided between the contact pivot (10) and the opposite electrode (20).
20. An integrated circuit, in particular an integrated CMOS circuit, including a microelectromechanical system (100, 200) according to one of the claims 1 through 19.
21. A method for producing an integrated circuit according to claim 20 through a CMOS production process comprising the steps:

    - producing the integrated circuit in an FEoL process with a plurality of electronic circuit elements; and

    - electrically contacting the electronic circuit elements in a BEoL process,

    wherein the electromechanical microswitch (1) is integrated in the BEoL process in a recess (105) of the multi-level conductive path layer stack (102, 202),
    characterized in that the contact pivot (10), the opposite contact (20) and the at least one drive electrode (30) activating the contact pivot (10) respectively form a portion of a conductive level (M1 - M5) of the multi-level conductive path layer stack (102, 202) and wherein the opposite contact (20) includes a metal-insulator-metal (MIM) structure (24, 25, 26) at a distal end (23) oriented towards the contact pivot (10).
22. The production method according to claim 21, wherein the structure (33) including knobs (34) with dielectric material (25) configured as an oxide of an electrode material of a conductive level (M1 - M5) of the multi-level conductive path layer stack (102, 202) for the electromechanical microswitch (1) is formed in particular through wet chemical etching.

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