JP2010225431A - Transmission line - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission line that prevents impedance mismatching. <P>SOLUTION: The transmission line used for an MEMS structure includes a dielectric substrate 21 with a first main surface F1 as well as a second main surface F2 opposed to each other and with a first recess Ca1 formed at the first main surface F1, and a signal wiring 10 arranged on the first main surface F1 and inside the first recess Ca1 for transmitting high frequencies. At least part of the side of the first recess Ca1 makes a slanted face WA1 where a normal of that side acutely crosses a normal of the first main surface F1. Part 10a of the signal wiring 10 is arranged on the slanted face WA1. The part 10a of the signal wiring arranged on the slanted face WA1 is electrically connected to a back electrode 13 arranged on the second main surface F2. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a transmission line used for a MEMS structure and transmitting a high frequency.

  2. Description of the Related Art Conventionally, an electromechanical switch (MEMS switch) that performs a switch operation similar to a normal mechanical switch by manufacturing a micro drive mechanism on a substrate surface using a semiconductor process and driving it by electromagnetic force is known ( For example, see Patent Document 1).

  In Patent Document 1, in a bulk micromachine system in which a micro-drive mechanism is manufactured by bonding substrates together, a recess is formed on the surface of the substrate, and electrodes that are continuous from the surface of the substrate to the side and bottom surfaces of the recess are formed. . And the recessed part is sealed using the sealing substrate in which the micro drive part is formed. As a result, the number of times of bonding the substrates is reduced, and the switch characteristics and reliability are improved.

JP 2006-236765 A

  By the way, in a structure manufactured using the MEMS switch or other MEMS technology (hereinafter referred to as “MEMS structure”), a transmission line for transmitting an electrical signal may be used. When connecting this transmission line and a device that handles the electric signal, impedance matching is important. If the impedances of the device and the transmission line are not matched, undesirable electrical signal reflections occur, which cause mutual interference between the electrical signals and attenuate signal strength.

  Conventionally, in order to transmit an electrical signal transmitted through a signal wiring formed on the front surface of a substrate to a back electrode formed on the back surface of the substrate, via wiring is embedded in a hole penetrating from the front surface to the back surface of the substrate. The signal wiring and the back electrode were connected to the via wiring.

  However, there may be a mismatch in the impedance of the via wiring due to a manufacturing error in the hole forming process or the via wiring embedding process.

  The present invention has been made in view of the above problems, and an object thereof is to provide a transmission line that suppresses impedance mismatching.

  A feature of the present invention is a transmission line used in a MEMS structure, the transmission line having a first main surface and a second main surface that face each other, and a first recess on the first main surface. Formed on the first main surface and inside the first recess, and at least a part of the side surface of the first recess The normal of the side surface forms an inclined surface that intersects with the normal of the first main surface at an acute angle, a part of the signal wiring is arranged on the inclined surface, and a part of the signal wiring arranged on the inclined surface Is electrically connected to the back electrode disposed on the second main surface.

  According to the characteristics of the present invention, at least a part of the side surface of the first recess forms an inclined surface in which the normal of the side surface intersects at an acute angle with respect to the normal of the first main surface, Is disposed on the inclined surface, and a part of the signal wiring disposed on the inclined surface is electrically connected to the back electrode disposed on the second main surface. Accordingly, the through via is eliminated as compared with the case where the signal wiring is electrically connected to the back surface electrode through the through via embedded in the hole penetrating from the first main surface to the second main surface. Can be shortened. Therefore, impedance mismatch due to the through via is suppressed, and as a result, high-frequency transmission characteristics can be improved.

  In addition, since the dielectric substrate itself is not thinned, the mechanical strength of the dielectric substrate is ensured, and handling during manufacture, transportation, and use remains unchanged.

  In the feature of the present invention, the first recess has a bottom surface, a through wiring is embedded in a hole penetrating the dielectric substrate from the bottom surface to the second main surface, and a part of the signal wiring is on the bottom surface. It may be extended to be electrically connected to the through wiring, and may be electrically connected to the back electrode through the through wiring. The first recess has a bottom surface without penetrating to the second main surface. Therefore, when the inside of the MEMS structure is sealed, the dielectric substrate functions as a package or a cap member. Therefore, the number of members is reduced, the manufacturing cost is reduced, and the MEMS structure is reduced in size.

  Alternatively, in the feature of the present invention, the first dent may penetrate to the second main surface, and a part of the signal wiring arranged on the inclined surface may be in contact with the back electrode. Thereby, since the through via embedded in the hole penetrating from the first main surface to the second main surface can be eliminated, the influence of impedance mismatch due to the through via is eliminated.

  In the feature of the present invention, a second recess is formed in the second main surface, a ground electrode is disposed on the second main surface and inside the second recess so as to face the signal wiring, and the ground electrode and the signal The distance from the wiring may be constant along the longitudinal direction of the signal wiring. By adjusting the positions and shapes of the first recess and the second recess so that the distance between the ground electrode and the signal wiring is constant along the longitudinal direction of the signal wiring, the signal wiring in the coplanar waveguide line The distance between the ground electrodes is constant, and a transmission line that realizes high frequency characteristics can be designed.

  In the features of the present invention, the transmission line further includes a pair of ground wirings disposed on at least the first main surface and the inclined surface and sandwiching both sides of the signal wiring in the short direction at a predetermined interval. The distance between the signal line on the inclined surface and the pair of ground lines may change from the distance on the first main surface toward the second main surface. Thereby, the impedance of the signal wiring on the inclined surface can be matched.

  In the feature of the present invention, a pair of ground through wirings are embedded in a hole penetrating the dielectric substrate from the bottom surface to the second main surface at positions sandwiching both sides of the through wiring, and the pair of ground wirings You may electrically connect to a pair of ground penetration wiring, respectively. Thereby, since a pair of ground penetration wiring becomes a slit and electromagnetic coupling to a penetration wiring can be controlled, a still higher high frequency characteristic is realizable.

  According to the transmission line of the present invention, impedance mismatch can be suppressed.

It is a perspective view which shows the external appearance of the micro relay using the transmission line in connection with the 1st Embodiment of this invention. FIG. 2 is a perspective view illustrating a state in which a base 20, a functional unit 30, a cover 40, and a driving device 50 in FIG. 1 are separated in a stacking direction (z direction). FIG. 3A is a plan view showing a configuration of a transmission line according to the first embodiment of the present invention, which is applied to a portion surrounded by a dotted line G in FIG. 2, and FIG. It is sectional drawing along the AA cut surface of Fig.3 (a). 4A is a plan view showing a back surface configuration of a portion surrounded by a dotted line G in the base 20 shown in FIG. 2, and FIG. 4B is a cross-sectional view taken along the line BB in FIG. 3A. FIG. FIG. 5A is a plan view showing a configuration of a transmission line according to the second embodiment of the present invention, which is applied to a portion surrounded by a dotted line G in FIG. 2, and FIG. FIG. 5C is a cross-sectional view taken along the line C-C in FIG. 5A, and FIG. 5C is a plan view showing a back surface configuration of a portion surrounded by a dotted line G in the base 20 shown in FIG. FIG. 6A is a cross-sectional view taken along a DD line corresponding to FIG. 3B of the first embodiment, showing the configuration of the transmission line according to the third embodiment of the present invention. FIG. 6B is a plan view showing the back surface configuration of the transmission line.

Embodiments of the present invention will be described below with reference to the drawings. In the description of the drawings, the same parts are denoted by the same reference numerals.
(First embodiment)

  First, with reference to FIG.1 and FIG.2, the structure of a micro relay is demonstrated as an example of the MEMS structure using the transmission line in connection with the 1st Embodiment of this invention. The micro relay according to the first embodiment of the present invention is a MEMS relay that handles a high-frequency electric signal and has a micro-drive mechanism manufactured using a semiconductor process, and further includes a normally open contact and a normally closed contact. Is a so-called latching type relay.

  As shown in FIG. 1, the micro relay includes a base 20, a functional unit 30, a cover 40, and a driving device 50 having an electromagnet device 51. FIG. 2 illustrates each configuration of the base 20, the functional unit 30, the cover 40, and the driving device 50 in a state where they are separated in the stacking direction (z direction). The transmission line according to the first embodiment of the present invention is used in a part of the base 20, for example, a part surrounded by a dotted line G.

  Next, with reference to FIG. 2, each structure of the base 20, the function part 30, the cover 40, and the drive device 50 is demonstrated.

  The base 20 includes, for example, a silicon substrate 21 made of rectangular parallelepiped single crystal silicon and a signal wiring 10 disposed on a first main surface (hereinafter referred to as “surface”) of the silicon substrate 21 facing the functional unit 30. With. The signal wirings 10 are arranged in pairs on both ends in the longitudinal direction on the surface of the silicon substrate 21. The length direction of each signal wiring 10 coincides with the short direction (x direction) of the silicon substrate 21, and the pair of signal wirings 10 are arranged side by side in the length direction.

  A plurality of fixed contacts 26 electrically connected to the signal wiring 10 are formed on the surface of the silicon substrate 21. Each fixed contact 26 is connected to an end portion inside each silicon substrate 21 in each signal wiring 10. Therefore, a pair of fixed contacts 26 are provided on both ends of the silicon substrate 21 in the longitudinal direction.

  The fixed contact 26 is a metal thin film made of a metal material having good conductivity such as copper (Cu) or gold (Au). Such a fixed contact 26 can be formed using a sputtering method, an electroplating method, a vacuum deposition method, or the like. The fixed contact 26 is not limited to a single layer structure, and may be a multilayer structure including, for example, an Au layer and a Ti layer interposed between the Au layer and the base 20.

  The functional unit 30 mainly includes a movable part 32 and a frame 33 surrounding the movable part 32.

  The frame 33 is formed in a rectangular frame shape. Openings 31 (hereinafter referred to as “first openings” in the present embodiment) 31 are formed at both ends in the longitudinal direction of the frame 33 so that the signal wiring 10 faces the cover 40 side. An opening (hereinafter referred to as “second opening” in the present embodiment) 34 for the movable portion 32 is formed at the center of the frame 33. Each of the first openings 31 and the second openings 34 are in communication with each other at the central portion of the frame 33 in the short direction. Note that portions of the frame 33 between the first openings 31 and the second openings 34 constitute a pair of restricting protrusions that restrict the movement of the movable portion 32 in the direction along the longitudinal direction of the frame 33. . Further, the outer size of the frame 33 is equal to the outer size of the base 20.

  The movable portion 32 has a main body portion 320 disposed in the second opening 34 of the frame 33 and contact protrusions 321 respectively disposed in the first opening 31 of the frame 33. The main body 320 is formed in a rectangular plate shape. The longitudinal direction of the main body 320 and the longitudinal direction of the frame 33 substantially coincide with each other. A contact protrusion 321 is provided at the center of each end of the main body 320 in the longitudinal direction. The tip of the contact protrusion 321 is disposed in the first opening 31. A movable contact 322 is provided on the surface of the contact protrusion 321 facing the base 20 (the lower surface in FIG. 2). When the movable contact 322 contacts each of the pair of fixed contacts 26 simultaneously, the movable contact 322 causes the pair of fixed contacts 26 to be short-circuited. On the other hand, a fulcrum protrusion 323 is provided at the center of each end of the main body 320 in the short direction. A fulcrum protrusion 324 is provided on the surface of the fulcrum protrusion 323 facing the cover 40 (the upper surface in FIG. 2). The fulcrum protrusion 324 is used as a fulcrum for the swinging motion (seesaw motion) of the movable portion 32.

  The movable part 32 is integrally connected to the frame 33 by a plurality of (for example, four) support pieces 35. Each support piece 35 integrally connects the inner side surface in the longitudinal direction of the second opening 34 of the frame 33 and the outer side surface in the short direction of the main body 320. The four support pieces 35 are arranged at positions that are point-symmetric with respect to the center of the main body 320.

  The support piece 35 has a curved shape that advances while meandering in a direction along the longitudinal direction of the main body 320 in a plane orthogonal to the stacking direction (z direction). Thereby, the movable part 32 is supported so as to be swingable with respect to the frame 33. By forming the support piece 35 in a meandering shape, the length of the support piece 35 can be increased. Therefore, the spring constant of the spring force generated when the support piece 35 is twisted when the movable portion 32 swings can be appropriately reduced, and the stress applied to the support piece 35 can also be dispersed.

  The movable part 32, the frame 33, and the support piece 35 are, for example, a semiconductor substrate (for example, a silicon substrate or an SOI substrate) having a thickness of about 50 μm to 300 μm, preferably about 200 μm, and semiconductor fine processing such as photolithography and etching. It can be formed by patterning using technology.

  An armature 60 is provided on the side of the main body 320 of the movable portion 32 that faces the cover 40 (upper surface in FIG. 2). The armature 60 is formed by machining a magnetic material such as electromagnetic soft iron, electromagnetic stainless steel, or permalloy into a rectangular plate shape, and is joined to the main body 320 by a method such as adhesion, welding, heat fitting, or brazing. . The armature 60 is used for swinging the movable part 32 by a magnetic field generated by the electromagnet device 51 of the driving device 50. On the other hand, a reciprocal 70 is provided on the side of the movable portion 32 facing the base 20. The sequential 70 is used to set the distance between the movable part 32 and the base 20 to a suitable distance.

  The frame 33 of the functional unit 30 is joined to the base 20 in a state in which the movable contact 322 and the pair of fixed contacts 26 are aligned so as to face each other. Thereby, the function part 30 is attached to the surface side of the base 20. In joining the frame 33 to the base 20, a joining metal layer (not shown) can be used. The metal layer can be used as a ground.

  The cover 40 includes, for example, a rectangular parallelepiped glass substrate 45 and a closing plate 42. The outer size of the glass substrate 45 is equal to the outer size of the base 20. In the central portion of the glass substrate 45, an opening 41 is formed that penetrates the glass substrate 45 in the stacking direction (z direction). The blocking plate 42 is tightly bonded to the surface of the glass substrate 45 facing the functional unit 30 (the lower surface in FIG. 2) to block the entire opening 41. Therefore, a space surrounded by the inner peripheral surface of the opening 41 and the closing plate 42 constitutes a storage chamber of the driving device 50. The closing plate 42 is made of, for example, a thin plate such as a silicon plate or a glass plate having a thickness of about 5 to 50 μm, preferably about 20 μm. The cover 40 is joined to the surface of the frame 33 opposite to the base 20 (upper surface in FIG. 2). In joining the glass substrate 45 to the frame 33, a joining metal layer (not shown) can be used. The metal layer can be used as a high-frequency shield layer. However, a nonmagnetic material is used as the material of the metal layer so as not to block the magnetic field of the driving device 50.

  The drive device 50 includes an electromagnet device 51 that generates a magnetic field that attracts the armature 60 and a permanent magnet 52 that latches the movable portion 32. The electromagnet device 51 mainly includes a yoke 53 and a pair of coils 54. The yoke 53 integrally has a long rectangular plate-shaped main piece 530 and rectangular plate-shaped leg pieces 531 that protrude from both ends in the longitudinal direction on the surface side (the lower surface side in FIG. 2) of the main piece 530. I have. Such a yoke 53 is formed by bending or forging an iron plate such as electromagnetic soft iron. The permanent magnet 52 is formed in a rectangular parallelepiped shape, and is magnetized so that one surface side and the other surface side in the stacking direction have different polarities. The permanent magnet 52 is attached to the yoke 53 so that the other surface is in contact with the central portion in the longitudinal direction on the surface of the main piece 530 of the yoke 53. Each coil 54 is wound around each portion of the main piece 530 between each leg piece 531 and the permanent magnet 52. The drive device 50 is provided with a pair of coil terminals 55. By applying a voltage between the pair of coil terminals 55, a current flows through each coil 54. Such a driving device 50 is stored in the storage chamber of the cover 40.

  In the microrelay shown in FIGS. 1 and 2, a drive electrode (not shown) for energizing the coil 54 is formed on the second main surface (back surface) facing the surface of the silicon substrate 21. . A wiring pattern 43 to which the coil terminal 55 is connected is formed on the surface of the glass substrate 45 opposite to the functional unit 30 side. Here, the drive electrode and the wiring pattern 43 described above are a through via 27 that penetrates the silicon substrate 21 in the stacking direction, a through via 36 that penetrates the frame 33 in the thickness direction, and a penetration that penetrates the cover 40 in the thickness direction. The vias 44 are electrically connected.

  Although not shown in FIGS. 1 and 2, the end portion of the pair of signal wirings 10 that is outside the base 20 is formed through silicon vias embedded in holes that penetrate the silicon substrate 21. The substrate 21 is electrically connected to a back electrode disposed on the second main surface (back surface). The transmission line according to the first embodiment of the present invention is applied to a portion surrounded by a dotted line G in FIG. 2 including the signal wiring 10, the through wiring, and the back electrode.

  Next, the configuration of the transmission line according to the first embodiment of the present invention applied to the portion surrounded by the dotted line G in the base 20 shown in FIG. 2 will be described with reference to FIGS. 3A is a plan view of a portion surrounded by a dotted line G in the base 20 shown in FIG. 2, and FIG. 3B is a diagram of the microrelay along the AA cut surface in FIG. It is sectional drawing. The x direction in FIG. 3A is the x direction in FIG. 2, that is, the short direction of the base 20, and the y direction in FIG. 3A is the y direction in FIG.

  The transmission line according to the first embodiment of the present invention is a transmission line used for a micro relay as an example of a MEMS structure, and is opposed to a first main surface (surface) and a second main surface ( A silicon substrate 21 as an example of a dielectric substrate having a back surface and having a first recess Ca1 formed on the surface, and disposed on the surface of the silicon substrate 21 and inside the first recess Ca1 and having a high frequency And a pair of ground wirings 11 disposed on the surface of the silicon substrate 21 and in the first recess Ca1 and sandwiching both sides of the signal wiring 10 in the short direction at a predetermined interval. And a back electrode 13 disposed on the back surface F2 of the silicon substrate 21.

  Two first recesses Ca1 are formed in the silicon substrate 21 side by side in the x direction. The first recess Ca1 has a side surface and a bottom surface. At least a part of the side surface of the first recess Ca1 forms an inclined surface WA1 where the normal of the side surface intersects at an acute angle with respect to the normal of the surface F1. A part 10a of the signal wiring 10 is disposed on the inclined surface WA1 of the first recess Ca1, and a part 10b of the signal wiring 10 is extended to the bottom surface BT of the first recess Ca1. A through wiring 12 is embedded in a hole that penetrates from the bottom surface BT of the first recess Ca <b> 1 to the back surface F <b> 2 of the silicon substrate 21. The back electrode 13 and the part 10 b of the signal wiring 10 are in contact with the through wiring 12, respectively.

  Thus, in the first embodiment, a part 10a of the signal wiring 10 arranged on the inclined surface WA1 is connected to the back surface electrode via the other part 10b and the through wiring 12 arranged on the bottom surface BT. 13 is electrically connected.

  The distance between the ground wiring 11 and the signal wiring 10 arranged on the surface F <b> 1 of the silicon substrate 21 is constant along the longitudinal direction of the signal wiring 10. A frame electrode 19 is disposed on the surface of the silicon substrate 21 so as to surround the outer periphery of the silicon substrate 21. The frame electrode 19 and the ground wiring 11 are electrically connected, and a ground potential is applied.

  A part 11a of the ground wiring 11 is disposed on the inclined surface WA1 of the first recess Ca1, and a part 11b of the ground wiring 11 is extended to the bottom surface BT of the first recess Ca1. The distance between the signal wiring 10a and the ground wiring 11a on the inclined surface WA1 of the first recess Ca1 changes from the distance between the two on the front surface F1 of the silicon substrate 21 toward the back surface F2. Specifically, for example, the line width of the signal wiring 10a and the interval between the signal wiring 10a and the ground wiring 11a on the inclined surface WA1 of the first recess Ca1 are reduced as the back surface F2 is approached. Thereby, a transmission line can be reduced in size. Alternatively, the line width of the signal wiring 10a and the distance between the signal wiring 10a and the ground wiring 11a on the inclined surface WA1 of the first recess Ca1 may be increased as the back surface F2 is approached.

  As shown in FIG. 3B, the base 20, the functional unit 30, and the cover 40 are stacked. The movable contact 322 provided on the contact protrusion 321 in the function unit 30 comes into contact with the fixed contact on the pair of signal wirings 10 by the swinging of the main body in the function unit 30. The signal wiring 10 can be short-circuited.

  Next, referring to FIG. 4A and FIG. 4B, the back surface configuration of the portion surrounded by the dotted line G in the base 20 shown in FIG. 2 and the cross-sectional configuration at the BB cut surface of FIG. Will be explained. As shown in FIG. 4A, the back surface electrode 13 connected to the through wiring 12 and the ground electrode 14 electrically insulated from the back surface electrode 13 are disposed on the back surface F2 of the silicon substrate 21. . The back electrode 13 has a line segment shape, one end of which is connected to the through wiring 12, and the other end is disposed on the outer periphery of the silicon substrate 21. A predetermined gap is formed between the back electrode 13 and the ground electrode 14.

  As shown in FIG. 4B, the ground through wiring 15 is embedded in the holes penetrating from the bottom surface BT of the first recess Ca <b> 1 to the back surface F <b> 2 of the silicon substrate 21 at positions sandwiching both sides of the through wiring 12. It is. A portion 11b of the ground wiring disposed on the bottom surface BT and the ground electrode 14 are electrically connected by a ground through wiring 15 respectively.

  The signal wiring 10, the ground wiring 11, the back electrode 13, and the ground electrode 14 are preferably made of a conductive material having high adhesion to the silicon substrate 21. For example, Au, Cr, Pt, Ti, Ni, Al A conductor film made of Cu or the like, a conductor film made of an alloy of these, or a body film having a structure in which these layers are laminated are used.

  Here, an example of the manufacturing method of the transmission line shown in FIG.3 and FIG.4 is demonstrated. The wet etching process is performed on the surface F1 of the silicon substrate 21 on which the (100) crystal plane is exposed, using an alkali solution such as tetramethylammonium hydroxide (TMAH) or potassium hydroxide (KOH) aqueous solution as an etchant. Thereby, anisotropic etching which exposes the (111) crystal plane inclined with respect to the (100) crystal plane can be performed. Therefore, for example, a resist pattern having an opening is formed in a region where the first depression Ca1 is to be formed in the surface F1 of the silicon substrate 21, and the above-described surface F1 of the silicon substrate 21 exposed in the opening is selectively formed as described above. By performing the wet etching process, the inclined surface WA1 of the first dent Ca1 can be formed.

In addition, the vertical surface which 1st dent Ca1 has is formed by performing the dry etching process which has the anisotropy to the direction perpendicular | vertical with respect to the surface F1 before the process which forms above-mentioned inclined surface WA1. The vertical plane may be barriered with a barrier material that does not react with the above-described etchant. Then, the barrier material is removed after the wet etching process. By the above process, the first recess Ca1 having a side surface including the inclined surface WA1 and the vertical surface can be formed on the surface F1 of the silicon substrate 21. An ICP etching apparatus is used for the dry etching process, and two kinds of gases of SF ₆ and C ₄ F ₈ are used as etching gases. It is possible to form a groove with a high aspect ratio by repeating the etching with SF ₆ and the formation of the protective film with C ₄ F ₈ .

  Thereafter, a through hole is formed in the bottom surface BT of the first recess Ca1 by using a photolithography technique and an etching technique, and a conductor to be the through wiring 12 and the ground through wiring 15 is embedded therein. Then, using a physical vapor deposition (PVD) method such as a sputtering method, a chemical vapor deposition (CVD) method or the like, on the surface F1 of the silicon substrate 21, the inclined surface WA1 and the bottom surface BT of the first recess Ca1, At the same time, a conductor film is formed. Then, patterning of the signal wirings 10 and 10b and the ground wirings 11 and 11b shown in FIG. 3A is performed using a photolithography technique and an etching technique. Then, the signal wiring 10a and the ground wiring 11a formed on the inclined surface WA1 are patterned using a laser patterning technique. The back surface electrode 13 and the ground electrode 14 shown in FIG. 4A are also formed on the back surface F2 by a similar process.

  As described above, according to the first embodiment of the present invention, the following operational effects can be obtained.

  At least a part of the side surface of the first recess Ca1 forms an inclined surface WA1 in which the normal line of the side surface intersects with the normal line of the surface F1 of the silicon substrate 21 at an acute angle. Arranged on the inclined surface WA1. Further, the first recess Ca1 has a bottom surface BT, a through wiring 12 is embedded in a hole penetrating the silicon substrate 21 from the bottom surface BT to the back surface F2, and a part 10b of the signal wiring 10 is formed on the bottom surface BT. And is electrically connected to the through wiring 12 and is electrically connected to the back electrode 13 through the through wiring 12.

  Accordingly, the through via is shortened as compared with the case where the signal wiring 10 is electrically connected to the back electrode 13 through the through via embedded in the hole penetrating from the front surface F1 to the back surface F2 of the silicon substrate 21. be able to. The part 10a of the signal wiring 10 arranged on the inclined surface WA1 can suppress a change in impedance compared to the through via. Therefore, impedance mismatch due to the through via is suppressed, and as a result, high-frequency transmission characteristics can be improved.

  In addition, since the normal line of the inclined surface WA1 intersects at an acute angle with respect to the normal line of the surface F1 of the silicon substrate 21, for example, a part of the signal wiring 10 is formed on a vertical plane perpendicular to the surface F1. Compared with the case of forming, a rapid change in electromagnetic field and a change in impedance can be suppressed.

  Furthermore, since it is not necessary to make the entire silicon substrate 21 thin, the mechanical strength of the silicon substrate 21 is ensured, and handling during manufacture, transportation, and use is not different from the conventional one. Further, the bottom surface BT is formed without penetrating the first recess Ca1 to the back surface F2. Thereby, when sealing the inside of a micro relay, since the silicon substrate 21 functions as a package or a cap member, the number of members is reduced, the manufacturing cost is reduced, and the micro relay is reduced in size.

  In this way, a part of the signal wiring 10 a arranged on the inclined surface WA 1 is electrically connected to the back electrode 13 arranged on the back surface F 2 of the silicon substrate 21. Accordingly, the through via is shortened as compared with the case where the signal wiring 10 is electrically connected to the back electrode 13 through the through via embedded in the hole penetrating from the front surface F1 to the back surface F2 of the silicon substrate 21. As a result, impedance mismatch due to through vias is suppressed, and as a result, high-frequency transmission characteristics can be improved.

  By changing the interval between the signal wiring 10a and the pair of ground wirings 11a on the inclined surface WA1 of the first recess Ca1 from the interval on the front surface F1 of the silicon substrate 21 toward the back surface F2, the inclined surface WA1 The impedance of the signal wiring 10a can be matched. Specifically, for example, the line width of the signal wiring 10a and the interval between the signal wiring 10a and the ground wiring 11a on the inclined surface WA1 of the first recess Ca1 are reduced as the back surface F2 is approached. Thereby, a transmission line can be reduced in size. Alternatively, the line width of the signal wiring 10a and the interval between the signal wiring 10a and the ground wiring 11a on the inclined surface WA1 of the first recess Ca1 may be increased as the distance from the rear surface F2 is approached.

As shown in FIG. 4B, a pair of ground through wires 15 are formed in a hole penetrating the silicon substrate 21 from the bottom surface BT to the back surface F2 of the first recess Ca1 at positions sandwiching both sides of the through wire 12. Are embedded, and the pair of ground wirings 11 b and the ground electrode 14 are electrically connected by a pair of ground through wirings 15. Thereby, since a pair of ground penetration wiring 15 can suppress electromagnetic coupling to penetration wiring 12, still higher transmission characteristics of a high frequency are realizable.
(Second Embodiment)

  In the second embodiment, a case where the first recess Ca1 penetrates to the back surface F2 of the silicon substrate 21 will be described. 5A is a surface view of a portion surrounded by a dotted line G in the base 20 shown in FIG. 2, and FIG. 5B is an entire microrelay along the CC cut surface of FIG. 5A. FIG. The x direction in FIG. 5A is the x direction in FIG. 2, that is, the short direction of the base 20, and the y direction in FIG. 5A is the y direction in FIG.

  In the transmission line according to the second embodiment of the present invention, the first recess Ca1 formed in the front surface F1 of the silicon substrate 21 penetrates to the back surface F2 of the silicon substrate 21, and the first recess Ca1 extends through the bottom surface. I don't have it. A part 10a of the signal wiring 10 is disposed on the inclined surface WA1 of the first recess Ca1, but is not disposed on the bottom surface of the first recess Ca1. Similarly, a part 11a of the ground wiring 11 is disposed on the inclined surface WA1 of the first recess Ca1, but is not disposed on the bottom surface of the first recess Ca1.

  As shown in FIG. 5B, a part 10a of the signal wiring 10 disposed on the inclined surface WA1 of the first recess Ca1 is in contact with the back electrode 13b. That is, the part 10a of the signal wiring 10 is directly connected to the back electrode 13b without passing through the part 10b of the signal wiring 10 or the through wiring 12 arranged on the bottom surface BT shown in FIG. Connected to.

  As shown in FIG. 5C, the first recess Ca1 is exposed on the back surface F2 of the silicon substrate 21, and the back electrode 13b is disposed adjacent to the first recess Ca1, and the periphery thereof is set to a predetermined area. A ground electrode 14 is arranged at an interval. Although illustration is omitted, a part 11a of the ground wiring 11 disposed on the inclined surface WA1 of the first recess Ca1 is in contact with the ground electrode 14. In other words, the part 11a of the ground wiring 11 directly connects the ground electrode 14 without passing through the part 11b of the ground wiring 11 or the ground through wiring 15 arranged on the bottom surface BT shown in FIG. Connected.

  In addition, when sealing the inside of a microrelay in order to ensure the airtightness inside a microrelay, you may fill insulators, such as resin, in the inside of 1st dent Ca1.

  Other configurations are the same as the configurations of the transmission lines shown in FIG. 3 and FIG.

As described above, the first recess Ca1 penetrates to the back surface F2 of the silicon substrate 21, and a part 10a of the signal wiring disposed on the inclined surface WA1 of the first recess Ca1 contacts the back electrode 13b. ing. Thereby, since the through via embedded in the hole penetrating the silicon substrate can be eliminated, the influence of impedance mismatch due to the through via is eliminated, and as a result, the high-frequency transmission characteristics can be further improved.
(Third embodiment)

  In the third embodiment, a case will be described in which the first recess Ca1 does not penetrate to the back surface F2 but has the bottom surface BT, and the second recess Ca2 is formed on the back surface F2 of the silicon substrate 21. . The second recess Ca2 has an inclined surface WA2 and a bottom surface, and the ground electrodes 14 are disposed on the back surface F2 of the silicon substrate 21 and on the inclined surface WA2 and the bottom surface of the second recess Ca2, respectively. 6A is a cross-sectional view taken along the line D-D in FIG. 6B, and the ground electrode 14 is disposed to face the signal wiring 10.

  As shown in FIG. 6A, the distance between the ground electrodes 14, 14a and the signal wirings 10, 10a, that is, the thickness of the silicon substrate 21, is constant along the longitudinal direction of the signal wirings 10, 10a. Specifically, the second recess Ca2 is formed to face a region where the first recess Ca1 is not formed on the surface F1 of the silicon substrate 21, and the inclined surface WA2 is an inclined surface of the first recess Ca1. It is formed at a position facing WA1.

  As described above, the positions and shapes of the first recess Ca1 and the second recess Ca2 are set such that the distance between the ground electrodes 14 and 14a and the signal wirings 10 and 10a is constant along the longitudinal direction of the signal wirings 10 and 10a. By adjusting in this way, the distance between the signal wirings 10 and 10a and the ground electrodes 14 and 14a in the coplanar waveguide line becomes constant, and a transmission line that realizes high-frequency transmission characteristics can be designed.

Other configurations are the same as those of the transmission line shown in FIGS.
(Other embodiments)

  As described above, the present invention has been described with reference to the three embodiments. However, it should not be understood that the descriptions and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  For example, the third embodiment shows the case where the second recess Ca2 is formed on the back surface F2 side in the transmission line shown in FIGS. 3 and 4, but the back surface F2 side in the transmission line shown in FIG. Even if the second dent Ca2 is formed, a similar effect can be obtained.

  In the first to third embodiments of the present invention, the silicon substrate 21 made of single crystal silicon has been described as an example of the dielectric substrate. However, the dielectric substrate may be a glass substrate or a low-temperature co-fired ceramic substrate ( LTCC substrate). The advantages of each substrate are described. First, in the case of the silicon substrate 21, since the semiconductor fine processing technology such as the photolithography technology and the etching technology can be used, the processing of the base 20 can be easily performed as compared with the case of using the glass substrate. In particular, since the functional unit 30 is formed using silicon, the linear expansion coefficients of the functional unit 30 and the base 20 can be made approximately equal. Therefore, the stress resulting from the difference in linear expansion coefficient can be reduced. As the silicon substrate 21, it is desirable to use high resistance silicon. In this case, high frequency characteristics (particularly, high frequency characteristics in the slow wave mode) can be improved.

  When the dielectric substrate is a glass substrate, the high frequency characteristics can be improved by using glass which is a substance having a relatively low dielectric constant.

  The low-temperature co-fired ceramic substrate can easily form circular through-holes and internal wiring (ground layer) having a uniform diameter as compared with a glass substrate. When the diameter of the through hole is uniform, the high frequency characteristics are improved as compared with the case where the diameter of the through hole is not uniform (for example, when the diameter changes according to the depth of the hole). Further, by providing a ground layer inside the substrate, the impedance can be adjusted, and the impedance design becomes easy. Therefore, high-frequency transmission characteristics can be improved compared to a glass substrate.

  In the first to third embodiments of the present invention, the microrelay has been described as an example of the MEMS structure. However, the present invention is not limited to this, and a high frequency switch, a resonator, a filter, An oscillator is also included.

  Thus, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the invention specifying matters according to the scope of claims reasonable from this disclosure.

DESCRIPTION OF SYMBOLS 10 Signal wiring 10a, 10b Part of signal wiring 11 Ground wiring 11a, 11b Part of ground wiring 12 Through wiring 13, 13b Back electrode 14 Ground electrode 15 Ground through wiring 19 Frame electrode 20 Base 21 Silicon substrate (dielectric substrate)
26 fixed contact 27, 36, 44 through-via 30 function part 31 first opening 32 movable part 33 frame 34 second opening 35 support piece 40 cover 41 opening part 42 closing plate 43 wiring pattern 45 glass substrate 50 driving device 51 Electromagnetic device 52 Permanent magnet 53 Yoke 54 Coil 55 Coil terminal 60 Armature 70 Reciprocal 320 Main body 321 Contact protrusion 322 Movable contact 323 Support point protrusion 324 Support point protrusion 530 Main piece 531 Leg piece BT Bottom face F1 Surface (first main surface) surface)
F2 back side (second main surface)
WA1, WA2 inclined surface

Claims (6)

A transmission line used in a MEMS structure,
A dielectric substrate having a first main surface and a second main surface facing each other and having a first recess formed in the first main surface;
A signal wiring disposed on the first main surface and in the first recess and transmitting a high frequency signal,
At least a part of the side surface of the first recess forms an inclined surface in which a normal line of the side surface intersects at an acute angle with respect to a normal line of the first main surface,
A part of the signal wiring is disposed on the inclined surface, and a part of the signal wiring disposed on the inclined surface is electrically connected to a back electrode disposed on the second main surface. A transmission line characterized by that.   The first recess has a bottom surface, and a through wiring is embedded in a hole penetrating the dielectric substrate from the bottom surface to the second main surface, and a part of the signal wiring is formed on the bottom surface. The transmission line according to claim 1, wherein the transmission line is electrically connected to the through-hole wiring and is electrically connected to the back electrode through the through-wiring.   The said 1st dent penetrates to the said 2nd main surface, A part of said signal wiring arrange | positioned on the said inclined surface is contacting the said back surface electrode. Transmission line.   A second recess is formed on the second main surface, a ground electrode is disposed on the second main surface and inside the second recess so as to face the signal wiring, and the ground electrode and the signal The transmission line according to any one of claims 1 to 3, wherein a distance from the wiring is constant along a longitudinal direction of the signal wiring. A pair of ground wirings disposed on at least the first main surface and the inclined surface and sandwiching both sides of the signal wiring in a short direction at a predetermined interval;
The distance between the signal line and the pair of ground lines on the inclined surface changes as the distance from the distance on the first main surface approaches the second main surface. The transmission line as described in any one of 1-4.   A pair of ground through wires are embedded in a hole penetrating the dielectric substrate from the bottom surface to the second main surface at positions sandwiching both sides of the through wire, and the pair of ground wires are The transmission line according to claim 5, wherein the transmission line is electrically connected to the pair of ground through wires.

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