ARRANGEMENT OF MEMS SWITCHES

Description

[0001] The invention relates to an arrangement of MEMS switches with movable elements.

[0002] Three different solutions are known for switching electric current: Firstly, electromechanical relays are used, secondly, semiconductor switching elements are used, and finally, MEMS switches (MEMS = Micro-Electro-Mechanical System) can also be used.

[0003] MEMS switches are based on the mostly electrostatically actuated movement of a moving element, in particular a small bar, whose movement moves the MEMS switch into an open or closed position. The microscopic dimensions of the moving element advantageously allow for short switching times and virtually no wear. However, the current-carrying capacity and dielectric strength of moving elements in MEMS switches are too low for many applications. To address higher power classes, several MEMS switches can be interconnected to form an array and, in particular, arranged in a matrix. Arrays of MEMS switches are known, for example, from EP 2 541 568 A1, which, however, does not describe specific embodiments of the MEMS switches but rather a circuit concept. MEMS switch arrays are also known from US 2019 / 172672 A1.EP 2 398 028 A2 and WO 2004 / 015728 A1, for example, disclose embodiments of MEMS switches.

[0004] Interconnecting multiple MEMS switches into an array requires a large number of identically manufactured MEMS switches that must exhibit identical behavior throughout their entire operating life. This can be achieved through high process quality, but producing a large number of MEMS switches is rarely feasible.

[0005] It is therefore an object of the invention to create an arrangement of MEMS switches which has a higher reliability, especially in the case of individual MEMS switches that do not meet the specifications.

[0006] This object of the invention is achieved with an arrangement of MEMS switches having the features specified in claim 1. Preferred embodiments of the invention are specified in the dependent claims, the following description, and the drawing.

[0007] The arrangement of MEMS switches according to the invention comprises MEMS switches with movable elements, wherein the MEMS switches are interconnected in a total cross-tied circuit. In the arrangement according to the invention, conductor connections advantageously extend along at least two spaced-apart planes, and the MEMS switches (20) each have a first (150) and a second part (210), wherein the first part (150) of the MEMS switch (20) is formed with a silicon substrate and the second part (210) is formed with a glass wafer (220). The first plane is arranged on the first part and the second plane on the second part, or the first plane is arranged on the second part and the second plane on the first part.

[0008] The circuit in a Total Cross-Tied (TCT) configuration offers several advantages: Firstly, multiple MEMS switches are connected in parallel in a TCT configuration, which increases the current-carrying capacity of the arrangement compared to individual MEMS switches, proportionally to the number of MEMS switches connected in parallel. Furthermore, the series connection of the MEMS switches increases the dielectric strength of the arrangement compared to individual MEMS switches. Therefore, the arrangement is inherently more reliable due to the increased current-carrying capacity and dielectric strength. The additional cross-connections in the TCT configuration also allow for redundant configuration of the MEMS switches, so that faulty MEMS switches can be easily bypassed via the additional circuit paths.

[0009] Because the conductor connections extend along at least two spaced-apart planes, conductor crossings within a plane can be avoided. Thus, conductor connections running at an angle to each other, especially perpendicularly, are arranged along spaced-apart planes, so that an actual conductor crossing does not occur. Therefore, conductor crossings do not need to be specifically considered during manufacturing, which would entail a very high manufacturing effort. Consequently, a TCT circuit with MEMS switches can be manufactured very reliably.

[0010] In the arrangement according to the invention, the MEMS switches in a suitably further development each have a bending element as a movable element.

[0011] Preferably, each of the MEMS switches has a first electrical contact on the movable element and each of the MEMS switches has a second electrical contact, wherein the first contacts are located on a first of the planes and the second contacts are located on a second of the planes.

[0012] Thus, two spaced-apart planes, along which conductor connections can be arranged, can be formed on the movable element and at a distance from it. By moving the movable element, a conductive connection can then be created between components located in the two planes.

[0013] In an advantageous further development, the arrangement according to the invention includes gate contacts which are located in the first and / or second level.

[0014] The independent manufacturing of the at least two parts of the MEMS switch, as possible according to the invention, allows for the provision of two levels in the manufacturing process without significant additional costs or effort, along which the conductor connections can be arranged as described above.

[0015] Preferably, in the arrangement according to the invention, the first part is formed with a silicon-on-insulator substrate, in particular with a silicon-on-glass substrate.

[0016] Advantageously, in this further development of the invention, the first and second parts are bonded to each other, for example by means of at least one eutectic and / or anodic bond and / or a silicon direct bond.

[0017] Particularly preferred in the arrangement according to the invention is at least one of the MEMS switches designed and manufactured as described in the embodiment of DE 10 2017 215 236 A1.

[0018] The invention will now be explained in more detail with reference to an embodiment shown in the drawing. The drawing shows: Fig. 1 shows a schematic arrangement of MEMS switches according to the invention in a basic circuit diagram, Fig. 2 shows the arrangement of MEMS switches according to the invention. Fig. 1 schematically in a top view and Fig. 3 a MEMS switch of the arrangement of MEMS switches according to the invention. Fig. 1 and 2 schematic longitudinal section.

[0019] The arrangement 10 of MEMS switches 20 according to the invention is a matrix arrangement of MEMS switches 20 in which the MEMS switches 20 are arranged in a rectangular grid of mutually perpendicular rows 30 and columns 35. The MEMS switches 20 are connected in series in the matrix arrangement, one after the other in rows 30. For this purpose, the MEMS switches 20 each have a source 40 and a drain 50, which the MEMS switches 20 electrically isolate from each other in an open position by spacing a first switching contact 60 and a second switching contact 70, and which are electrically conductively connected to each other in a closed position. To control the MEMS switches 20 into the open and closed positions, the MEMS switches 20 each have a gate contact 80, which, depending on the potential applied with a gate potential 85, exerts an electrostatic force on a bending beam 90 (sa Figures 2 and3 The bending beam 90 is deflected by the electrostatic force exerted by the MEMS switch 20, which carries the second switching contact 70. In its rest position, the bending beam 90 is electrically conductively connected to the first switching contact 60, while in its deflected position, it is insulated from the first switching contact 60. Opposite the gate contact 80, each MEMS switch 20 has a ground contact 93 at ground potential 96, relative to which a source potential of the source terminal 50 and a gate potential of the gate contact 80 each define a voltage.

[0020] Thus, the MEMS switches 20 are opened or closed by means of the gate contact 80. The source terminals 40 and the drain terminals 50 of the MEMS switches 20 of different rows 30 and each of a common column 35 are connected to each other by means of a connecting line 100. This connecting line 100, spanning different rows 30 of each of a column 35, forms a total cross-tied circuit (TCT circuit) with the rest of the circuit of the arrangement 10 described above. In such a TCT circuit, the connecting lines 100 are therefore oriented perpendicular to the longitudinal center axis L of the bending beams 90. The connecting lines 100 thus cross the provided conductor connections 110 of the gate contacts 80 and conductor connections 120 of the ground contacts 93 at intersection points 130.

[0021] The intersection points 130, however, do not actually form true intersection points in a plane, but merely appear as such intersection points 130 in a circuit diagram. This is because, in reality, the connecting lines 100 and the line connections 110 of the gate contacts 80, as well as the line connections 120 of the ground contacts 93, run in planes parallel to and spaced apart from each other.

[0022] This becomes evident from the more detailed representation of the MEMS switch 20 in Fig. 3As shown, the MEMS switch 20 comprises two parts: A first part 150 is formed with a silicon-on-insulator substrate, which includes two silicon layers 160, 170 separated by a glass layer 180. The first silicon layer 160 has a thickness approximately 30 times that of the second silicon layer 170, which has a thickness of 10 micrometers. The second silicon layer 170 forms the bending beam 90, which is hinged to the first silicon layer 160 in a region 185 by means of the glass layer 180 and has a free end 190. The bending beam 90 extends with its free end 190 in a direction parallel to the unlimited, i.e. longest, planar, extension directions of the glass layer 180 from the area 185, so that in the undisplaced state the longitudinal central axis L of the bending beam 90 extends parallel to the unlimited extension directions of the glass layer 180.Between area 185 and the free end 190, the silicon of the second silicon layer 170 and the glass of the glass layer 180 are removed, allowing the free end 190 to oscillate freely. The bending beam 90 has the first switching contact 60 at its free end 190.

[0023] The MEMS switch 20 also has a second part 210, which is formed with a glass wafer 220. The glass wafer 220 has two grooves 230, 240 extending perpendicular to the longitudinal center axis L of the bending beam 90, which are open towards the first part 150 of the MEMS switch 20. One of the two grooves 230 extends along the entire width of the free part of the bending beam 90 and also beyond the free end 190 of the bending beam 90, so that the bending beam 90 can pivot freely into the first groove 230. Facing the first switching contact 60, the second switching contact 70 is attached to the bottom of the first trench 230, so that the bending beam 90 can bring the first switching contact 60 and the second switching contact 70 into electrical contact with each other by pivoting the bending beam 90 towards the second part 210 into the first trench 230.

[0024] The second trench 240 extends parallel to the first trench 230 and opens towards area 185. The second trench 240 is spaced from the first trench 230 by a fraction of its width, so that a bridge is located between the first trench 230 and the second trench 240, which abuts the end of area 185 that borders the free end 190 of the bending beam 90.

[0025] The surface of the bending beam 90 facing the second part forms a first plane 245, along which the connecting lines 100 of the source connections 40 extend with their direction of travel, dh the direction of a current flowing through the connecting lines 100, in a direction perpendicular to the plane of the drawing. For example, the connecting lines 100 extend along the area 185.

[0026] A base 250, 260 of the trenches 230, 240, extending essentially parallel to the longitudinal center axis L of the bending beam 90, forms a second plane 265 along which the connecting lines 110 of the gate contacts 80 extend with their direction of travel perpendicular to the plane of the drawing. For example, the connecting lines 120 can also extend along the second plane 265, such as along the base 260.

[0027] The MEMS switches 20 in this embodiment are designed and manufactured as described in the German patent application DE 10 2017 215 236 A1.

Claims

1. Arrangement of MEMS switches (20) with movable elements (90), which are interconnected in a total-cross-tied connection (10), wherein a plurality of MEMS switches (20) are interconnected in parallel and a plurality of MEMS switches are interconnected in series in the total-cross-tied connection (10), and wherein additional cross-connections are provided for a redundant layout of the MEMS switches, such that faulty MEMS switches are able to be easily bypassed by means of the additional conduction paths, the arrangement further comprising conductor connections (100, 110, 120), characterized in that the conductor connections (100, 110, 120) extend along at least two planes (245, 265) that are spaced apart from one another, and the MEMS switches (20) each have a first part (150) and a second part (210), wherein the first part (150) of the MEMS switch (20) is formed with a silicon substrate and the second part (210) is formed with a glass wafer (220), and in which the first plane (245) is arranged on the first part (150) and the second plane (265) is arranged on the second part (210) or the first plane (245) is arranged on the second part (150) and the second plane (265) is arranged on the first part (150).

2. Arrangement according to the preceding claim, in which the MEMS switches (20) each have a bending element (90) as a movable element.

3. Arrangement according to either of the preceding claims, in which each of the MEMS switches (20) has a respective first electrical contact (60) on the first movable element (90) and has a respective second electrical mating contact (70), wherein the first contacts (60) are located on a first one of the planes (245) and the second contacts (70) are located on a second one of the planes (265).

4. Arrangement according to one of the preceding claims, in which gate contacts (80) are present, which are located in the first plane (245) and / or the second plane (265).

5. Arrangement according to one of the preceding claims, in which the first part (150) is formed with a silicon-on-insulator substrate, in particular with a silicon-on-glass substrate.