WO2010110315A1 - Transmission line - Google Patents

Abstract

Provided is a transmission line having a dielectric substrate and signal wiring. The dielectric substrate has a first surface and a second surface, and the second surface is positioned on the side opposite to the first surface side. The dielectric substrate has a first region on the first surface, and a rear surface electrode is disposed on the second surface. The signal wiring is configured to transmit signals, has a length, a width, and a first end at one end in the length direction. The first end is disposed in the first region and is electrically connected to the rear surface electrode. The first region overlaps the rear surface electrode in the thickness direction of the dielectric substrate.

Description

Transmission line

The present invention relates to a transmission line for transmitting a high frequency.

Conventionally, a microstrip line in which a linear conductor film is formed on a dielectric substrate such as a silicon substrate is known. A transmission line made of a dielectric substrate having such a microstrip line is disclosed in Patent Document 1 described later. In Patent Document 1, the transmission line includes a dielectric substrate and signal wiring. The dielectric substrate is formed in a substantially plate shape. The dielectric substrate has a first surface, and a signal wiring made of a linear conductor foil is formed on the first surface. The dielectric substrate has a second surface located on the opposite side of the first surface. The dielectric substrate has a ground plane on the second surface. The dielectric substrate has a groove formed in a part thereof. This groove makes the distance between the signal wiring and the ground plane smaller than the thickness of the dielectric substrate.

This groove is formed on the second surface of the dielectric substrate. On the other hand, the first surface on which the signal wiring is formed is a flat surface. The groove shortens the distance between the signal wiring and the ground plane, thereby adjusting the impedance of the microstrip line.

JP 7-336114 A

As a transmission line for transmitting a high-frequency signal, a coplanar waveguide (coplanar wave guide) is known in addition to a microstrip line. The coplanar waveguide is composed of a substrate, a first conductor film, and a second conductor film. The first conductor film is provided on the upper surface of the substrate. The first conductor film has a slit-shaped opening. The second conductor film is provided on the upper surface of the substrate so as to be positioned inside the slit-shaped opening. The second conductor film is electrically insulated from the first conductor film. The coplanar waveguide transmits electromagnetic waves by an electric field in a direction from the signal wiring toward the first conductor films on both sides, a magnetic field in a direction surrounding the signal line inside the substrate, and a direction along the transmission direction outside the substrate.

The technology for adjusting the impedance of the microstrip line by forming a groove on the second surface of the dielectric substrate disclosed in Patent Document 1 can also be applied to this coplanar waveguide. In this case, the electric field in the direction from the signal wiring toward the first conductor films on both sides includes an electric field penetrating the inside of the dielectric substrate and an electric field passing through the air layer above the dielectric substrate. Here, the first surface of the dielectric substrate is a flat surface. Therefore, the ratio of the electric field passing through the air layer of information on the dielectric substrate to the electric field penetrating the inside of the dielectric substrate does not increase.

The dielectric loss tangent of dielectric substrates such as glass and silicon is larger than the dielectric loss tangent of the air layer. Therefore, the dielectric substrate has a greater loss of electrical energy (hereinafter referred to as “dielectric loss”) than the air layer. Here, “dielectric loss tangent (tangent delta)” is a numerical value representing the degree of dielectric loss in the capacitor formed by the signal wiring and the ground plane.

Therefore, the dielectric loss cannot be reduced in the coplanar waveguide in which the groove is formed on the second surface of the dielectric substrate.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a transmission line having a small dielectric loss and excellent transmission characteristics.

In order to solve the above-described problem, in the transmission line of the present invention, the dielectric substrate having a dielectric substrate and a signal wiring has a first surface and a second surface, and the second surface is the first surface. The dielectric substrate has a first region on the first surface, and the dielectric substrate is provided with a back electrode on the second surface. The signal wiring is configured to transmit a signal, has a length and a width, has a first end at one end in the length direction, and the first end is The first region is disposed in a first region, the first end is electrically connected to the back electrode, and the first region overlaps the back electrode in the thickness direction of the dielectric substrate. In this case, a transmission line having a small dielectric loss and excellent transmission characteristics can be obtained.

The dielectric substrate has a first recess formed in the first region, the first recess has a first inner surface, and one end of the signal wiring is disposed on the first inner surface. It is preferable.

The first inner surface includes a bottom surface, the first end of the signal wiring is disposed on the bottom surface, and the dielectric substrate is provided with a surface ground electrode on the first surface, The front surface ground electrode is electrically insulated from the signal wiring, and the dielectric substrate is provided with a rear surface ground electrode on the second surface, and the rear surface ground electrode is electrically connected to the signal wiring. Is preferably electrically insulated.

In this case, a first recess is formed on the first surface of the dielectric substrate. The signal wiring is disposed on the bottom surface of the first recess. Therefore, the distance between the signal wiring and the back surface ground electrode can be shortened as compared with the transmission line in which the signal wiring is arranged on the first surface. In this case, a transmission line having a desired impedance is obtained. At the same time, the signal wiring is disposed on the bottom surface of the first recess. In this case, an electric flux is formed between the signal wiring and the surface ground electrode. This electric flux is divided into an electric flux passing through the inside of the dielectric substrate and an electric flux passing through the air layer. This configuration can increase the electric flux passing through the air layer more than the electric flux passing through the inside of the dielectric substrate. The air layer has less dielectric loss than the dielectric substrate. As a result, dielectric loss can be reduced.

The first recess has a length along the first surface, and a bottom surface of the first inner surface has a length along a length direction of the first recess, and the signal All of the wiring is preferably arranged on the bottom surface.

The dielectric substrate has a second recess formed on the second surface thereof, and the second recess is formed to overlap the first recess in the thickness direction of the dielectric substrate, It is preferable that the second recess has a second inner surface, and the back ground electrode is formed on the second surface and the second inner surface.

It is preferable that the periphery of the second recess is aligned with the periphery of the first recess in the thickness direction of the dielectric substrate.

The first inner surface has an inclined surface, and the inclined surface is inclined with respect to the first surface so as to intersect at an acute angle with respect to the first surface. It is preferable that a part of one end is provided on the inclined surface.

In this case, the inclined surface of the first recess intersects the first surface at an acute angle. A part of one end of the signal wiring is disposed on the inclined surface. Accordingly, the through via can be shortened as compared with the case where the signal wiring is electrically connected to the back electrode via the through via embedded in the through hole penetrating from the first surface to the second surface. Therefore, impedance mismatch due to the through via is suppressed. As a result, a transmission line with high frequency transmission characteristics can be obtained.

The recess has an inner diameter, and the inner diameter is formed so as to decrease from the first surface to the second surface of the dielectric substrate, whereby the recess has the inclined surface. It is preferable.

The first inner surface further has a bottom surface, and the dielectric substrate is provided with a through wiring penetrating from the second surface to the bottom surface, and the through wiring is electrically connected to the back electrode. It is preferable that one end of the signal wiring is disposed on the bottom surface and is electrically connected to the through wiring.

It is preferable that the dielectric substrate has a through hole extending from the second surface to the bottom surface, and the through wiring is disposed in the through hole.

The dielectric substrate has a second recess formed on the second surface, and the dielectric substrate has a back surface ground electrode on the second surface and the second recess, and the back surface ground electrode Is electrically insulated from the back electrode, and the back ground electrode is separated from the signal wiring by a predetermined distance in the thickness direction of the dielectric substrate, and the predetermined distance is the signal wiring It is preferable that it is constant over the length direction.

The dielectric substrate has a pair of surface ground electrodes, the surface ground electrodes are provided over the first surface and the inclined surface, and the surface ground electrodes are positioned on both sides of the signal wiring. Are arranged along the width direction of the signal wiring, and are separated from the signal wiring so as to be electrically insulated from the signal wiring, and the signal wiring has a wiring inclined portion, The wiring inclined portion is located on the inclined surface, the surface ground electrode has an electrode inclined portion, the electrode inclined portion is located on the inclined surface, and the wiring inclined portion is the electrode inclined portion. It is preferable that the first distance is separated from the portion, and the first distance changes as the surface ground electrode and the signal wiring approach the second surface.

The dielectric substrate further includes a pair of through-ground wirings, each of the pair of through-grounds penetrating from the second surface to the first surface of the dielectric substrate, and the through-ground Is located on both sides of the through wiring, is disposed along the width direction of the signal wiring, is electrically insulated from the through wiring, and the pair of through grounds is the pair of surfaces It is preferable to be electrically connected to the ground electrode.

The dielectric substrate has a hole formed in the first region, the hole penetrates from the second surface to the first surface, and the hole has a first inner surface, The signal wiring preferably extends from the first surface to the back electrode via the first inner surface.

The first inner surface has an inclined surface, and the inclined surface is inclined with respect to the first surface so as to intersect at an acute angle with respect to the first surface. It is preferable that a part of one end is provided on the inclined surface.

It is preferable that the hole is filled with an insulating resin.

It is a perspective view which shows the external appearance of the micro relay using the transmission line in connection with Embodiment 1 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 top view showing a configuration of a transmission line according to Embodiment 1 of the present invention, which is applied to a portion surrounded by a dotted line G in FIG. FIG. 3B is a bottom view of the 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. FIG. 3C is a cross-sectional view taken along the line AA in FIG. FIG. 3D is a cross-sectional view relating to a modification. It is a figure explaining the effect which the transmission line concerning Embodiment 1 of the present invention shows. FIG. 4A is a cross-sectional view of a transmission line according to a comparative example. FIG. 4B is a cross-sectional view of the transmission line according to the first embodiment of the present invention. FIG. 5A is a top 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. FIG.5 (b) is a bottom view of the structure of the transmission line concerning Embodiment 2 of this invention applied to the part enclosed with the dotted line G of FIG. FIG. 5C is a cross-sectional view taken along the line BB in FIG. FIG. 5D is a cross-sectional view relating to a modification. FIG. 6A is a plan view showing a configuration of a transmission line according to Embodiment 3 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 a). 7A 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. 7B is a cross-sectional view taken along the line BB in FIG. 6A. FIG. FIG. 8A is a plan view showing a configuration of a transmission line according to the fourth embodiment of the present invention, which is applied to a portion surrounded by a dotted line G in FIG. 2, and FIG. FIG. 8C is a cross-sectional view taken along the line CC of FIG. 8A, and FIG. 8C 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. 9 (a) is a cross-sectional view taken along the line DD in FIG. 6 (b) of the third embodiment, showing the configuration of the transmission line according to the fifth embodiment of the present invention. These are top views which show the back surface structure of a 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.
(Embodiment 1)
First, with reference to FIG.1 and FIG.2, the structure of the micro relay using the transmission line in connection with Embodiment 1 of this invention is demonstrated. A micro relay is an example of a MEMS structure. The micro relay according to the first embodiment of the present invention is a MEMS relay that transmits a high-frequency electric signal and has a micro-drive mechanism manufactured using a semiconductor process. Further, the micro relay is a so-called latching type relay having a normally open contact and a normally closed contact.

FIG. 1 shows a perspective view of the microrelay of this embodiment. 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 shows an exploded perspective view of the microrelay of this embodiment. As shown in FIG. 2, the micro relay has a base 20, a functional unit 30, a cover 40, and a driving device 50. The transmission line according to the first embodiment of the present invention is used in a part of the base 20. If it demonstrates concretely, the transmission line in connection with Embodiment 1 of this invention is used for the part enclosed with the dotted line G of the base 20. FIG.

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 a glass substrate 21 and a pair of signal wirings 10. The glass substrate 21 is formed in a rectangular parallelepiped shape. Therefore, the glass substrate 21 has a length, a width, and a thickness. The width direction of the glass substrate 21 is along the y direction of FIG. The length direction of the glass substrate 21 is along the x direction of FIG. The thickness direction of the glass substrate 21 is along the z direction of FIG. The glass substrate 21 has the 1st surface which functions as a surface, and the function part 30 is arrange | positioned on this 1st surface. The signal wiring 10 is disposed on the first surface. One pair of signal wirings 10 is disposed at one end in the longitudinal direction of the glass substrate 21, and the other pair of signal wirings 10 is disposed at the other end in the longitudinal direction of the glass substrate 21. Each of the pair of signal wirings 10 has a length and a width. The signal wiring 10 is disposed so as to have a length along the width direction of the glass substrate 21. The pair of signal wirings 10 are arranged along the width direction of the glass substrate 21.

The signal wiring 10 has a first end located at one end in the width direction of the glass substrate 21 and a second end opposite to the first end. The signal wiring 10 has a fixed contact 26 at the second end. A pair of fixed contacts 26 are disposed on both ends of the glass 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 movable part 32 and the frame 33 have a length along the length direction of the glass substrate 21 and have a width along the width direction.

The frame 33 is formed in a frame shape. The frame 33 has two first openings and one second opening. More specifically, the frame 33 has first openings 31 at one end and the other end in the length direction. The frame 33 has a second opening 34 at the center thereof. Therefore, the second opening 34 is located between the first opening 31 and the first opening 31. 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. Further, the frame has a regulation protrusion 331. The restriction protrusions 331 extend from the both ends in the width direction of the frame to the inside of the frame. The restricting protrusion 331 is located between the first opening 31 and the second opening 34. The restriction protrusion 331 prevents the movable part 32 from moving in the direction along the longitudinal direction of the frame 33. The outer size of the frame 33 is equal to the outer size of the base 20.

The movable part 32 has a main body part 320 and a contact protrusion 321. The movable part 32 is arranged inside the frame 33 so that the main body part 320 is arranged inside the second opening 34. The movable portion 32 is disposed inside the frame 33 such that the contact protrusion 321 is disposed inside the first opening 31 of the frame 33. The main body 320 is formed in a rectangular plate shape. The contact protrusions 321 are located at both ends in the longitudinal direction of the main body 320, and project from the center in the width direction of the main body 320 toward the outside in the longitudinal direction of the main body 320. The tip of the contact protrusion 321 is disposed in the first opening 31. The contact protrusion 321 has a lower surface, and the lower surface faces the first surface of the base 20. The contact protrusion 321 is provided with a movable contact 322 on the lower surface thereof. 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, the main body 320 is provided with a fulcrum protrusion 323. The fulcrum protrusions 323 are located at both ends in the width direction of the main body 320 and at the center in the length direction. The fulcrum protrusion 323 has an upper surface, and this upper surface faces the lower surface of the cover 40. The fulcrum protrusion 323 is provided with a fulcrum protrusion 324 on the upper surface thereof. The fulcrum protrusion 324 is used as a fulcrum for the swinging motion of the movable part 32. In other words, the movable part 32 is disposed inside the frame 33 so as to swing around the fulcrum protrusion 324.

The movable portion 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 located at both ends in the longitudinal direction of the second opening 34 of the frame 33 and the outer side surface of the main body 320 in the width direction. 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 formed by, 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, such as photolithography technology and etching technology. It can be formed by patterning using technology.

The movable part 32 is provided with a magnetic plate 60 on the upper surface side of the main body part 320. The magnetic plate 60 is made of, for example, a magnetic material such as electromagnetic soft iron, electromagnetic stainless steel, and permalloy machined 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 The magnetic plate 60 is used for swinging the movable portion 32 by a magnetic field generated by the electromagnet device 51 of the driving device 50. On the other hand, a sequential 70 is provided on the lower surface of the movable portion 32. 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 described above is joined to the base 20 so that the movable contact 322 and the pair of fixed contacts 26 face each other. Thereby, the functional unit 30 is attached to the first 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 is 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 thickness direction (z direction). The closing plate 42 is tightly bonded to the lower surface of the glass substrate 45 and closes the entire opening 41. Therefore, the cover 40 is formed with a recess having an upper opening. More specifically, the cover 40 has a recess defined by the inner peripheral surface of the opening 41 and the closing plate 42. The driving device 50 is disposed in the recess. 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 driving device 50 includes an electromagnet device 51 that generates a magnetic field that attracts the magnetic plate 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 the upper surface side and the lower surface side have different polarities. The permanent magnet 52 is attached to the yoke 53 so that the upper surface thereof is in contact with the longitudinal center of the upper surface of the main piece 530 of the yoke 53. Each coil 54 is wound around the main piece 530 so as to be positioned between each leg piece 531 and the permanent magnet 52. The drive device 50 is provided with a pair of coil terminals 55. When a voltage is applied 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 surface of the glass substrate 21. A wiring pattern 43 to which the coil terminal 55 is connected is formed on the upper surface of the glass substrate 45. Here, the drive electrode and the wiring pattern 43 described above are a through via 27 that penetrates the glass 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 first end of each signal wiring 10 is connected to the first end of the glass substrate 21 via a penetration signal wiring embedded in a hole that penetrates the glass substrate 21. It is electrically connected to the back surface extraction electrode arranged on the two surfaces. 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 signal wiring 12, and the back electrode 13.

Next, with reference to FIGS. 3A to 3C, 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. explain. 3A is a plan view showing a first surface of a portion surrounded by a dotted line G in the base 20 shown in FIG. 2, and FIG. 3B is a plan view showing a second surface. FIG. 3C is a cross-sectional view taken along the line AA in FIG.

The transmission line according to Embodiment 1 of the present invention is a transmission line used for the MEMS structure, and includes a glass substrate 21, a signal wiring 10, a front surface ground electrode 11, and a back surface ground electrode 14. The glass substrate 21 is used as an example of a dielectric substrate. The glass substrate 21 has a first surface F1 and a second surface F2. The second surface F2 is located on the opposite side of the first surface F1. Further, the glass substrate 21 has a first region on the first surface F1. Further, the glass substrate 21 has a first recess Ca1 formed in the first region of the first surface F1. In other words, the first recess Ca1 defines the first region of the first surface F1. This 1st recessed part Ca1 has the 1st inner surface comprised by the bottom face BT and the side surface. The signal wiring 10 is disposed on the bottom surface BT of the first recess Ca1. More specifically, all the signal wirings 10 are disposed on the bottom surface BT of the first recess Ca1. Therefore, the first end of the signal wiring 10 is also disposed on the bottom surface BT of the first recess Ca <b> 1 that is the first region. The signal wiring 10 is provided for transmitting a high frequency signal. The surface ground electrode 11 is provided on the first surface F <b> 1 and is electrically insulated from the signal wiring 10. The back surface ground electrode 14 is disposed on the second surface F2. The back surface ground electrode 14 is separated via the glass substrate 21. Therefore, the back surface ground electrode 14 is electrically insulated from the signal wiring 10.

The signal wiring 10 in FIG. 3A is one linear wiring, and is in contact with the through wiring 12 at both ends thereof. When applied to the signal wiring 10 in the base 20 of FIG. 2, a pair of signal wirings 10 is formed by removing the central portion in the length direction of the signal wiring 10 of FIG.

The through wiring 12 penetrates from the first surface F1 to the second surface F2 of the glass substrate 21. The through wiring 12 is in contact with the signal wiring 10 at one end located on the first surface F1 side. The through wiring 12 is electrically connected to the back surface electrode 13 disposed on the second surface F2 at one end located on the second surface F2 side. The through wiring 12 has a cylindrical shape. The back electrode 13 overlaps the through wiring 12 in the thickness direction of the glass substrate 21. The back electrode 13 has the same circular planar shape as the through wiring 12.

The surface ground electrode 11 is provided with a linear gap. The signal wiring is composed of a linear conductor foil. The signal wiring 10 is disposed on the upper surface of the glass substrate 21 so as to be located inside the gap. As a result, the signal wiring 10 is sandwiched between the linear slits. The linear slits and the signal wiring 10 are arranged along the width direction of the signal wiring 10. A ground potential is applied to the surface ground electrode 11. Electromagnetic waves are transmitted by an electric field formed between the signal wiring 10 and the surface ground electrodes 11 on both sides thereof. Further, the characteristic impedance of the transmission line can be arbitrarily designed by adjusting the distance between the signal wiring 10 and the surface ground electrode 11. A glass substrate 21 is exposed in the gap between the signal wiring 10 and the surface ground electrode 11. Thereby, the signal wiring 10 is electrically insulated from the surface ground electrode 11.

The surface ground electrode 11 is electrically connected to the through ground wiring 15. The through-ground wiring 15 penetrates from the first surface F1 to the second surface F2 of the glass substrate 21, contacts the surface ground electrode 11 at one end on the first surface F1 side, and at the end on the second surface F2 side. It is in contact with the back ground electrode 14. The through-ground wiring 15 has a cylindrical shape. In the first embodiment, two through-ground wirings 15 forming a pair are arranged on both sides of the signal wiring 10.

The back surface ground electrode 14 is disposed on a portion of the second surface F2 of the glass substrate 21 excluding the region where the back electrode 13 is formed and the peripheral region of the back electrode 13. That is, the back surface ground electrode 14 is separated from the back surface electrode 13 by a predetermined distance. The characteristic impedance of the transmission line can be designed to have an arbitrary value by adjusting the distance from the back surface electrode 13 to the back surface ground electrode 14. The glass substrate 21 is exposed in the gap between the back ground electrode 14 and the back electrode 13. Therefore, the back surface ground electrode 14 is electrically insulated from the back surface electrode 13.

As shown in FIG. 3 (c), a first recess Ca1 is formed on the first surface F1 of the glass substrate 21. 1st recessed part Ca1 is comprised by the bottom face BT and side surface which are located in the other side of 2nd surface F2. The first recess Ca1 has a width. The width of the first concave portion Ca1 is gradually reduced from the first surface F1 toward the second surface F2. The first recess Ca <b> 1 has a length along the width direction of the glass substrate 21 and a width along the length direction of the glass substrate 21. Accordingly, the first recess Ca1 has a length along the first surface F1. The signal wiring 10 is disposed along the length direction of the bottom surface BT, and is disposed at the center of the bottom surface BT in the width direction.

As shown in FIG. 3C, the bottom surface BT has an intersection line intersecting the side surface. The distance from one end of the signal wiring 10 in the width direction to the intersection line is preferably in the range of 0 to 2 times the width of the signal wiring 10. Further, the side surface of the first recess Ca1 is inclined at a predetermined angle different from the right angle with respect to the bottom surface BT. However, the side surface of the first recess Ca1 may intersect the bottom surface BT at a right angle.

The surface ground electrode 11 is disposed up to the upper end of the side surface of the first recess Ca1. In other words, the surface ground electrode 11 is disposed on the entire first surface F1 of the glass substrate 21 excluding the first recess Ca1.

Next, an example of a method for manufacturing the transmission line shown in FIG. 3 will be described. For example, a through hole for the through wiring (12, 15) and the first recess Ca1 are formed on the glass substrate 21 having a thickness of 500 μm by using blasting or the like. Here, the slit-shaped first recess Ca1 is formed so that the depth is 200 to 400 μm and the bottom width is 100 to 400 μm.

A metal film such as gold (Au) or copper (Cu) is formed on the second surface F2 of the glass substrate 21 by plating. At this time, the metal film is filled in the through hole for the through wiring (12, 15) described above. Thereafter, using the photolithography technique and the etching technique, as shown in FIG. 3B, the patterned back surface ground electrode 14 and back surface electrode 13 are formed.

Similarly, a metal film such as Au or Cu is formed on the first surface F1 of the glass substrate 21 by plating. Thereafter, as shown in FIG. 3A, a patterned surface ground electrode 11 and signal wiring 10 are formed by using a photolithography technique and an etching technique. At this time, the line width of the signal wiring 10 is 100 to 300 μm. According to these design parameters, a transmission line having a characteristic impedance of 50Ω can be manufactured.

Next, with reference to FIG. 4, the operation and effects of the transmission line shown in FIGS. 3 (a) to 3 (c) will be described. FIG. 4A is a cross-sectional view of a transmission line according to a comparative example. FIG. 4B is a cross-sectional view of the transmission line according to the first embodiment of the present invention.

Both the transmission line according to the comparative example and the first embodiment have a glass substrate 21, a front surface ground electrode 11, a back surface ground electrode 14, and a signal wiring 10. The surface ground electrode 11 is provided on the first surface F <b> 1 of the glass substrate 21. The back surface ground electrode 14 is provided on the second surface F <b> 2 of the glass substrate 21. The surface ground electrode 11 has a linear gap formed at the center thereof, and the upper surface of the glass substrate 21 is exposed upward via the gap. The signal wiring 10 is disposed at the center of the gap. And a transmission line transmits electromagnetic waves with the 1st magnetic field, the 2nd magnetic field, and the 3rd magnetic field. The first magnetic field is generated from the signal wiring 10 toward the surface ground electrode 11. The second magnetic field is generated in the direction surrounding the signal wiring 10 inside the glass substrate 21. The third magnetic field is generated outside the glass substrate 21 in a direction along the longitudinal direction of the signal wiring 10.

In the comparative example shown in FIG. 4A, the signal wiring 10 and the surface ground electrode 11 are formed on the flat upper surface of the glass substrate 21. Here, the first electric field EL from the signal wiring 10 toward the surface ground electrode 11 is divided into an electric field that penetrates the inside of the glass substrate 21 and an electric field that passes through the air layer above the glass substrate 21. In the case of the structure shown in FIG. 4A, the ratio of the electric field passing through the air layer of the information on the glass substrate 21 to the electric field passing through the inside of the glass substrate 21 is not large.

On the other hand, in the first embodiment of the present invention shown in FIG. 4B, the signal wiring 10 is formed at the central portion of the bottom surface of the first recess Ca1. Even in this case, the first electric field EL from the signal wiring 10 toward the surface ground electrode 11 is divided into an electric field penetrating the inside of the glass substrate 21 and an electric field passing through the air layer above the glass substrate 21. In the case of the structure shown in FIG. 4B, the ratio of the electric field passing through the air layer above the glass substrate 21 to the electric field penetrating the inside of the glass substrate 21 is increased.

The dielectric loss tangent (tangent delta) of a dielectric substrate such as glass or silicon is larger than the dielectric loss tangent of the air layer. Therefore, the dielectric substrate has a larger dielectric loss than the air layer. Therefore, it is preferable to form the signal wiring 10 inside the first recess Ca1. By forming the signal wiring 10 inside the first recess Ca1, the dielectric loss of the transmission line is reduced.

As described above, the transmission line of the present embodiment includes the glass substrate 21 and the signal wiring 10. As for the glass substrate, 1st recessed part Ca1 is formed in the 1st surface F1. The signal wiring 10 is disposed on the bottom surface BT of the first recess Ca1. In this case, an electric flux is formed between the signal wiring 10 and the surface ground electrode 11. This electric flux includes an electric flux passing through the inside of the glass substrate 21 and an electric flux passing above the glass substrate 21. Since the signal wiring 10 is disposed on the bottom surface BT of the first recess Ca1, the electric flux passing through the inside of the glass substrate 21 is larger than the electric flux passing above the glass substrate. In other words, it is possible to increase the electric flux passing through air having a dielectric loss smaller than that of the glass substrate 21. As a result, the dielectric loss of the transmission line is reduced.

The signal wiring 10 is disposed on the bottom surface BT of the first recess Ca1. Therefore, the distance between the signal wiring 10 and the back surface ground electrode 14 can be shortened as compared with the case where the signal wiring 10 is disposed on the flat first surface F1. In other words, compared with the case where the signal wiring 10 is arranged on the bottom surface BT of the first concave portion Ca1 from the signal wiring 10 as compared with the case where the signal wiring 10 is arranged on the glass substrate 21 where the first concave portion Ca1 is not formed. The distance to the back ground electrode 14 is reduced. As a result, a desired impedance can be obtained in the transmission line in which the signal wiring 10 and the back surface ground electrode 14 are electromagnetically coupled.

Furthermore, in the transmission line of this embodiment, since the glass substrate 21 is formed with the first concave portion Ca1 only in a part thereof, the portions other than the first concave portion Ca1 are ensured in thickness. Therefore, the mechanical strength of the glass substrate 21 is ensured. That is, the transmission line according to the present embodiment is handled in the same manner as in the past during manufacture, transportation, and use, and can suppress a decrease in yield.
(Embodiment 2)
Next, referring to FIGS. 5A to 5C, the configuration of the transmission line according to the second embodiment of the present invention applied to the portion surrounded by the dotted line G in the base 20 shown in FIG. explain. 5A is a plan view showing a first surface of a portion surrounded by a dotted line G in the base 20 shown in FIG. 2, and FIG. 5B is a plan view showing a second surface. FIG. 5C is a cross-sectional view taken along the line BB in FIG.

The transmission line according to Embodiment 2 of the present invention is a transmission line used for a MEMS structure. The transmission line of the present embodiment includes a glass substrate 21, a signal wiring 10, and a back surface ground electrode 14. The glass substrate 21 is a dielectric substrate having a first surface F1 and a second surface F2. The first surface F1 is located on the opposite side of the second surface F2. As for the glass substrate 21, 1st recessed part Ca1 is formed in the 1st surface F1. The signal wiring 10 is disposed on the bottom surface BT of the first recess Ca1. The signal wiring 10 is provided for transmitting a high frequency signal. The back surface ground electrode 14 is disposed on the second surface F2.

The transmission lines in FIGS. 5A to 5C are different from the transmission lines in FIGS. 3A to 3C in that the surface ground electrode 11 and the through-ground wiring 15 are not provided. Other configurations are the same.

The signal wiring 10 in FIG. 5A is one linear wiring. The signal wiring 10 is electrically connected to the through wiring 12 at both ends in the length direction. When applied to the signal wiring 10 in the base 20 in FIG. 2, the pair of signal wirings 10 is formed by removing the central portion of the signal wiring 10 in FIG. 5.

The through wiring 12 penetrates from the first surface F1 to the second surface F2 of the glass substrate 21. The through wiring 12 is electrically connected to the signal wiring 10 at one end on the first surface F1 side, and is electrically connected to the back electrode 13 at one end on the second surface F2 side. The through wiring 12 has a cylindrical shape, and the back electrode 13 overlaps the through wiring 12 in the thickness direction of the glass substrate 21 and has the same circular planar shape as the through wiring 12.

As shown in FIG. 5C, a first recess Ca1 is formed on the first surface F1 of the glass substrate 21. As shown in FIG. The first recess Ca1 has a bottom surface BT and side surfaces located on the opposite side of the second surface F2. The first recess Ca1 has a length and a width. The signal wiring 10 is disposed in the central portion of the bottom surface BT along the length direction of the bottom surface BT.

As described above, in the transmission line of the present embodiment, the signal wiring 10 is disposed on the bottom surface BT of the first recess Ca1. Therefore, when the signal wiring 10 is arranged on the bottom surface BT of the first concave portion Ca1 from the signal wiring 10 than when the signal wiring is arranged on the upper surface of the glass substrate 21 not having the first concave portion Ca1. The distance to the back ground electrode 14 is short. Therefore, the transmission line of this embodiment in which the signal wiring 10 and the back surface ground electrode 14 are electromagnetically coupled can widen the design range of impedance.

Furthermore, in the transmission line of the present embodiment, since the glass substrate 21 is formed with the first recess Ca1 only in a part thereof, the thickness other than the first recess Ca1 is ensured. Therefore, the mechanical strength of the glass substrate 21 is ensured. That is, the transmission line according to the present embodiment is handled in the same manner as in the past during manufacture, transportation, and use, and can suppress a decrease in yield.

3 (d) and 5 (d) show modified examples of the above-described first and second embodiments. For example, as shown in FIG. 3D and FIG. 5D, a second recess Ca2 may be formed on the second surface F2 of the glass substrate 21. Thereby, 2nd recessed part Ca2 has a 2nd inner surface. 2nd recessed part Ca2 is formed so that it may be located on the opposite side to 1st recessed part Ca1, and has the same linear planar shape. More specifically, the second recess Ca2 is on the opposite side of the first recess Ca1 so that the entire periphery of the second recess Ca2 overlaps with the entire periphery of the first recess Ca1 in the thickness direction of the glass substrate 21. To position. The back surface ground electrode 14 is also disposed on the second inner surface of the second recess Ca2. Thereby, the distance between the signal wiring 10 and the back surface ground electrode 14 can be further shortened. Therefore, the design range of impedance is further expanded.

In the first and second embodiments of the present invention, the glass substrate 21 has been described as an example of a dielectric substrate. However, a silicon substrate made of single crystal silicon or a low temperature co-fired ceramic substrate (LTCC substrate) can also be used as the dielectric substrate. In the case of a silicon substrate, a semiconductor fine processing technique such as a photolithography technique and an etching technique can be used. Therefore, the base 20 made of a silicon substrate can be processed more easily than the base 20 made of the glass substrate 21. In particular, the functional unit 30 is formed using silicon. Therefore, the linear expansion coefficients of the functional unit 30 and the base 20 can be made approximately equal. By making the linear expansion coefficients of the functional unit 30 and the base 20 approximately equal, the stress generated between the functional unit 30 and the base 20 due to the difference in linear expansion coefficient is reduced. As the silicon substrate, it is desirable to use high resistance silicon. In this case, high frequency characteristics (particularly, high frequency characteristics in the slow wave mode) are improved.

When the dielectric substrate is the glass substrate 21, 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 the glass substrate 21. 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. More specifically, when the diameter of the through hole is uniform regardless of the depth of the hole, it has better high frequency characteristics than when the diameter of the hole changes according to the depth of the hole. Further, the impedance can be adjusted by providing a ground layer inside the substrate. As a result, the transmission line impedance can be easily designed. Therefore, high-frequency transmission characteristics can be improved compared to a glass substrate.

In the embodiment of the present invention, the micro relay has been described as an example of the MEMS structure. However, the present invention is not limited to this, and includes a high frequency switch, a resonator, a filter, an oscillator, and the like that handle high frequency electric signals.
(Embodiment 3)
This embodiment will be described with reference to FIGS. The micro relay of the present embodiment also has the same configuration except for the micro relay and the base 20 in the first embodiment. Therefore, the same reference numerals are given to the same components as those in the first embodiment. The description of the same configuration as that of the first embodiment is omitted.

The base 20 includes a silicon substrate 21 and a pair of signal wirings 10. The silicon substrate 21 is made of rectangular parallelepiped single crystal silicon. Accordingly, the silicon substrate 21 has a length, a width, and a thickness. The width direction of the silicon substrate 21 is along the y direction of FIG. The length direction of the silicon substrate 21 is along the x direction of FIG. The thickness direction of the silicon substrate 21 is along the z direction of FIG. The silicon substrate 21 has a first surface. The functional unit 30 is disposed on the first surface of the silicon substrate 21. The signal wiring 10 is disposed on the first surface. The signal wiring 10 is disposed on the first surface. One pair of signal wirings 10 is disposed at one end in the longitudinal direction of the silicon substrate 21, and the other pair of signal wirings 10 is disposed at the other end in the longitudinal direction of the silicon substrate 21. Each of the pair of signal wirings 10 has a length and a width. The signal wiring 10 is arranged to have a length along the width direction of the silicon substrate 21. The pair of signal wirings 10 are arranged along the width direction of the silicon substrate 21.

The signal wiring 10 has a first end located at one end in the width direction of the silicon substrate 21 and a second end opposite to the first end. The second end of the signal wiring is located at the center in the width direction of the silicon substrate 21. The signal wiring 10 has a fixed contact 26 at the second end. Accordingly, a pair of fixed contacts 26 are disposed 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.

Next, with reference to FIGS. 6 and 7, the configuration of the transmission line according to the third 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. 6 (a) is a plan view of a portion surrounded by a dotted line G in the base 20 shown in FIG. 2, and FIG. 6 (b) is a diagram of the microrelay along the AA section in FIG. 6 (a). It is sectional drawing. The x direction in FIG. 6A is the x direction in FIG. 2, that is, the width direction of the base 20, and the y direction in FIG. 6A is the y direction in FIG.

The transmission line according to Embodiment 3 of the present invention is a transmission line used for a micro relay as an example of a MEMS structure. This transmission line includes a silicon substrate 21, a signal wiring 10, a pair of front surface ground electrodes 11, and a back surface electrode 13. The silicon substrate 21 is an example of a dielectric substrate. The silicon substrate 21 has a first surface and a second surface. The first surface is located on the opposite side of the second surface. The first surface has a first recess Ca1. The signal wiring 10 is provided for transmitting a high frequency signal. The signal wiring 10 is disposed on the first surface of the silicon substrate 21 and inside the first recess Ca1. The pair of surface ground electrodes 11 are disposed on the first surface of the silicon substrate 21 and inside the first recess Ca1. The pair of surface ground electrodes 11 are separated from the signal wiring 10 by a predetermined distance. The pair of surface ground electrodes 11 are located on both sides of the signal wiring 10. The pair of surface ground electrodes 11 and the signal wiring 10 are arranged along the width direction of the signal wiring 10. The back electrode 13 is disposed on the second surface F <b> 2 of the silicon substrate 21.

The silicon substrate 21 has two first recesses Ca1 arranged in the x direction. In other words, the silicon substrate 21 is provided with first recesses Ca1 at one end and the other end in the width direction. 1st recessed part Ca1 has the 1st inner surface comprised by the side surface and the bottom face BT. The first recess Ca1 has an opening area. More specifically, the first recess Ca <b> 1 has an opening area in a direction perpendicular to the thickness direction of the silicon substrate 21. The opening area of the first recess Ca1 decreases as it goes from the first surface F1 to the second surface F2. Moreover, 1st inner surface Ca1 has the periphery located in the upper end of the 1st inner surface Ca1, and the periphery located in the lower end of the 1st inner surface Ca2. The entire periphery located at the lower end of the first inner surface Ca1 is located inside the entire periphery located at the upper end of the first inner surface Ca1. At least a part of the side surface of the first recess Ca1 forms an inclined surface WA1 where the side surface intersects at an acute angle with respect to the first surface F1. The first end of the signal wiring 10 has a wiring inclined portion 10a and a wiring bottom portion 10b. The wiring inclined portion 10a of the signal wiring 10 is disposed on the inclined surface WA1 of the first recess Ca1. Furthermore, the wiring bottom portion 10b of the signal wiring 10 is disposed on the bottom surface BT of the first recess Ca1. The silicon substrate 21 has a through hole 221 that penetrates from the bottom surface BT of the first recess Ca1 to the second surface F2. In the silicon substrate 21, the through wiring 12 disposed so as to be positioned inside the through hole 221 is embedded. The back electrode 13 and the wiring bottom 10b of the signal wiring 10 are in contact with the through wiring.

Thus, in the third embodiment, the signal wiring 10 has the wiring inclined portion 10a and the wiring bottom portion 10b. The wiring inclined portion 10a is disposed on the inclined surface WA1. The wiring bottom portion 10b is disposed on the bottom surface BT. The wiring bottom portion 10 b is electrically connected to the back electrode 13 disposed on the bottom surface BT via the through wiring 12.

The surface ground electrode 11 disposed on the first surface F1 of the silicon substrate 21 is separated from the signal wiring 10 by a predetermined distance. Therefore, the surface ground electrode 11 is electrically insulated from the signal wiring 10. The predetermined distance between the surface ground electrode 11 and the signal wiring 10 is constant along the longitudinal direction of the signal wiring 10. A frame electrode (annular electrode) 19 is disposed on the first surface of the silicon substrate 21 so as to surround the outer periphery of the silicon substrate 21. The frame electrode (annular electrode) 19 and the surface ground electrode 11 are electrically connected, and a ground potential is applied.

The surface ground electrode 11 has an electrode inclined part 11a and an electrode bottom part 11b. The electrode inclined portion 11a of the surface ground electrode 11 is disposed on the inclined surface WA1 of the first recess Ca1. The electrode bottom 11b of the surface ground electrode 11 is extended to the bottom surface BT of the first recess Ca1. The wiring inclined portion 10 a of the signal wiring 10 is separated from the electrode inclined portion 11 a of the surface ground electrode 11 by a first distance. The first distance changes as the signal wiring 10 and the surface ground electrode 11 approach the second surface F2 of the silicon substrate 21. Specifically, the first distance decreases as the signal wiring 10 and the surface ground electrode 11 approach the second surface F <b> 2 of the silicon substrate 21. Thereby, a transmission line can be reduced in size. In addition, the space | interval of the wiring inclination part 10a of the signal wiring 10 and the electrode inclination part 11a of the surface ground electrode 11 may become large as it approaches the 2nd surface F2.

As shown in FIG. 6B, the functional unit 30 is disposed on the base 20. The cover 40 is disposed on the functional unit 30. Therefore, the base 20 is laminated together with the functional unit 30 and the cover 40. The movable contact 322 provided on the contact protrusion 321 in the function unit 30 contacts the fixed contact on the pair of signal wirings 10 as the main body in the function unit 30 swings. Thereby, the movable contact 322 short-circuits the pair of signal wirings 10.

Next, referring to FIG. 7A and FIG. 7B, 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 to Fig.7 (a), the silicon substrate 21 is provided with the back surface electrode 13 and the ground electrode 14 in the 2nd surface F2. The back electrode 13 is electrically connected to the through wiring 12. The back electrode 13 is electrically insulated from the back ground electrode 14. The back electrode 13 has a line segment shape. The back electrode 13 has one end connected to the through wiring 12 and the other end arranged on the outer periphery of the silicon substrate 21. A predetermined gap is formed between the back electrode 13 and the back ground electrode 14.

As shown in FIG. 7B, the silicon substrate 21 has a through hole penetrating from the bottom surface BT of the first recess Ca1 to the second surface F2 of the silicon substrate 21. The through holes are located on both sides of the through wiring 12. Further, the through hole 222 and the through wiring 12 are arranged along the width direction of the signal wiring 10. The silicon substrate 21 is provided with a through ground wiring 15, and the through ground wiring 15 is provided inside the through hole 222. Therefore, the through ground wiring 15 and the through wiring 12 are arranged along the width direction of the signal wiring 10. Further, the through ground wiring 15 is separated from the through wiring 12 by the silicon substrate 21. Accordingly, the through ground wiring 15 is electrically insulated from the through wiring 12. The electrode bottom 11b of the surface ground electrode 11 is disposed on the bottom surface BT of the first recess Ca1. Therefore, the electrode bottom 11 b of the front surface ground electrode 11 is electrically connected to the back surface ground electrode 14 through the through ground wiring 15.

It is preferable that the signal wiring 10, the front surface ground electrode 11, the back surface electrode 13, and the back surface ground electrode 14 are made of a conductive material having high adhesion to the silicon substrate 21. Examples of such a conductive material include Au, Cr, Pt, Ti, Ni, Al, and Cu. In addition, such conductive materials include alloys such as Au, Cr, Pt, Ti, Ni, Al, and Cu. Therefore, the signal wiring 10 is preferably made of a conductive film made of these conductive materials or alloys. Alternatively, the signal wiring 10 may be formed by laminating these conductive films in multiple layers.

Here, an example of a method for manufacturing the transmission line shown in FIGS. 6 and 7 will be described. First, a silicon substrate 21 with a (100) crystal face exposed is prepared. A wet etching process is performed on the first surface F1 of the silicon substrate 21 on which the (100) crystal plane is exposed, using an alkaline solution such as tetramethylammonium hydroxide (TMAH) or potassium hydroxide (KOH) aqueous solution as an etchant. Apply. Thereby, anisotropic etching which exposes the (111) crystal plane inclined with respect to the (100) crystal plane can be performed. Therefore, for example, the inclined surface WA1 is formed by the following process. First, a resist pattern having an opening in a predetermined region of the first surface F1 of the silicon substrate 21 is formed. Subsequently, the wet etching process is selectively performed on the first surface F1 of the silicon substrate 21 exposed from the opening. In this way, the inclined surface WA1 of the first recess Ca1 is formed.

In addition, when it is desired that the first recess Ca1 has a surface perpendicular to the first surface F1 in addition to the inclined surface WA1, the following steps are performed. First, before forming the inclined surface WA1, etching is selectively performed only in a direction perpendicular to the first surface F1. An example of such selective etching is dry etching. Thereby, a recess having a surface perpendicular to the first surface F1 is formed in the silicon substrate 21. Subsequently, a barrier material that does not react with the etchant is coated on the vertical surface of the recess. Subsequently, a wet etching process for performing wet etching on the silicon substrate is performed. Thereby, the silicon substrate 21 provided with the recessed part which has inclined surface WA1 is obtained. Then, the barrier material is removed after the wet etching process. As a result, the first recess F <b> 1 having a side surface having a surface perpendicular to the inclined surface WA <b> 1 is formed on the first surface F <b> 1 of the silicon substrate 21. An ICP etching apparatus is used for the dry etching process. Two types of gases, SF ₆ and C ₄ F ₈ , are used for the dry etching process in the ICP etching apparatus. Specifically, etching with SF ₆ and formation of a protective film with C ₄ F ₈ are performed alternately. As a result, a groove having a high aspect ratio is formed on the first surface F1 of the silicon substrate 21.

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. Subsequently, a conductor that becomes the through wiring 12 and the through ground wiring 15 is embedded in the through hole. Then, on the first surface F1 of the silicon substrate 21, the inclined surface WA1 of the first recess Ca1, and the bottom surface BT using a physical vapor deposition (PVD) method such as a sputtering method, a chemical vapor deposition (CVD) method, or the like. At the same time, a conductor film is formed. Then, using the photolithography technique and the etching technique, the signal wirings 10 and 10b and the surface ground electrodes 11 and 11b shown in FIG. 6A are patterned. Then, the signal wiring 10a and the surface ground electrode 11a formed on the inclined surface WA1 are patterned using a laser patterning technique. The back surface electrode 13 and the back surface ground electrode 14 shown in FIG. 7A are also formed on the second surface F2 by a similar process.

As described above, according to Embodiment 3 of the present invention, the following operational effects can be obtained.

At least part of the side surface of the first recess Ca1 forms an inclined surface WA1 whose side surface intersects at an acute angle with respect to the first surface F1 of the silicon substrate 21. The wiring inclined portion 10a of the signal wiring 10 is disposed on the inclined surface WA1. Further, the first recess Ca1 has a bottom surface BT. The silicon substrate 21 has a through hole 221 that penetrates the silicon substrate 21 from the bottom surface BT to the second surface F2. The through wiring 12 is embedded in the through hole 221 of the silicon substrate 21. The wiring bottom portion 10b of the signal wiring 10 is provided on the bottom surface BT. The wiring bottom 10 b of the signal wiring 10 is electrically connected to the through wiring 12 and is electrically connected to the back electrode 13 through the through wiring 12.

Thereby, compared with the case where the signal wiring 10 is electrically connected to the back surface electrode 13 through the through wiring embedded in the through hole penetrating from the first surface F1 to the second surface F2 of the silicon substrate 21, The through wiring can be shortened. The wiring inclined portion 10a of the signal wiring 10 disposed on the inclined surface WA1 has a smaller impedance change than the through wiring. Therefore, with this configuration, impedance mismatch due to the through wiring is suppressed, and as a result, high-frequency transmission characteristics can be improved.

In addition, since the inclined surface WA1 intersects the first surface F1 of the silicon substrate 21 at an acute angle, for example, compared with the case where a part of the signal wiring 10 is formed on a vertical surface perpendicular to the first surface F1, the inclined surface WA1 is sharp. It is possible to suppress a change in electromagnetic field and a change in impedance.

Furthermore, in the transmission line of the present embodiment, since the silicon substrate 21 has the first recess Ca1 formed only in a part thereof, the thickness is ensured at portions other than the first recess Ca1. Therefore, the mechanical strength of the silicon substrate 21 is ensured. That is, the transmission line according to the present embodiment is handled in the same manner as in the past during manufacture, transportation, and use, and can suppress a decrease in yield. Further, the first recess Ca1 does not penetrate to the second surface F2 of the silicon substrate 21. Therefore, when sealing the inside of the micro relay, the silicon substrate 21 functions as a package or a cap. Therefore, a micro relay can be manufactured with few members. As a result, the manufacturing cost is reduced and the shape of the microrelay is reduced.

As described above, the wiring inclined portion 10a of the signal wiring disposed on the inclined surface WA1 is electrically connected to the back surface electrode 13 disposed on the second surface F2 of the silicon substrate 21. Thereby, compared with the case where the signal wiring 10 is electrically connected to the back surface electrode 13 through the through via embedded in the through hole penetrating from the first surface F1 to the second surface F2 of the silicon substrate 21, The through via is shortened. Therefore, impedance mismatch due to the through via is suppressed, and as a result, high-frequency transmission characteristics can be improved.

The wiring inclined portion 10a of the signal wiring 10 on the inclined surface WA1 of the first recess Ca1 is separated from the electrode inclined portion 11a of the surface ground electrode 11 by a predetermined distance. This predetermined distance changes as it goes from the first surface F1 of the silicon substrate 21 to the second surface F2. Therefore, the impedance of the signal wiring 10a in the inclined surface WA1 can be matched. Specifically, for example, the line width of the wiring inclined portion 10a of the signal wiring 10 becomes smaller from the first surface F1 of the silicon substrate 21 toward the second surface F2. Further, the distance between the wiring inclined portion 10a of the signal wiring 10 and the electrode inclined portion 11a of the surface ground electrode 11 decreases as it goes from the first surface F1 of the silicon substrate 21 to the second surface F2. Thereby, a transmission line can be reduced in size. Note that the line width of the signal wiring 10a and the distance between the signal wiring 10a and the surface ground electrode 11a on the inclined surface WA1 of the first recess Ca1 may be increased as the second surface F2 is approached.

As shown in FIG. 7B, the silicon substrate 21 is provided with a pair of through ground wirings 15. The through ground wiring 15 is located on both sides of the through wiring 12. Further, the through ground wiring 15 and the through wiring 12 are provided along the width direction of the signal wiring. The pair of surface ground electrodes 11 b and the surface ground electrode 11 are electrically connected by a pair of through-ground wirings 15. With this configuration, the pair of through ground wirings 15 can be prevented from being electromagnetically coupled to the through wiring 12. As a result, high-frequency transmission characteristics can be realized.
(Embodiment 4)
In the fourth embodiment, the silicon substrate 21 has a hole Ca1 instead of the first recess Ca1. FIG. 8A is a surface view of a portion surrounded by a dotted line G in the base 20 shown in FIG. FIG. 8B is a cross-sectional view of the entire micro relay along the line CC of FIG. 8A. The x direction in FIG. 8A is the x direction in FIG. 2, that is, the width direction of the base 20. The y direction in FIG. 8A is the y direction in FIG. 2, that is, the longitudinal direction of the base 20.

In the transmission line according to Embodiment 4 of the present invention, the hole Ca1 formed in the silicon substrate 21 penetrates from the first surface F1 to the second surface F2 of the silicon substrate 21. Therefore, the hole Ca1 does not have a bottom surface. The wiring inclined portion 10a of the signal wiring 10 is disposed on the inclined surface WA1 of the hole Ca1. However, since the hole Ca1 does not have a bottom surface, the signal wiring 10 does not have a wiring bottom 10b. Similarly, the electrode inclined portion 11a of the surface ground electrode 11 is disposed on the inclined surface WA1 of the hole Ca1. However, since the hole Ca1 does not have a bottom surface, the surface ground electrode 11 does not have the electrode bottom 11b.

As shown in FIG. 8B, the wiring inclined portion 10a of the signal wiring 10 arranged on the inclined surface WA1 of the hole Ca1 is in contact with the back electrode 13b. That is, the signal wiring 10 is directly electrically connected to the back surface electrode 13b. In other words, the signal wiring 10 is electrically connected to the back surface electrode 13b without passing through the through wiring.

As shown in FIG. 8C, the silicon substrate 21 includes a hole Ca1 penetrating from the second surface F2 to the first surface F1. The silicon substrate 21 includes a back electrode 13b and a back ground electrode 14 on the second surface F2. The back electrode 13b is adjacent to the hole Ca1. The back surface ground electrode 14 is located around the back surface electrode 13b. Although not shown in the drawing, the electrode inclined portion 11a of the front surface ground electrode 11 disposed on the inclined surface WA1 of the hole Ca1 is in contact with the back surface back surface ground electrode. That is, the front surface ground electrode 11 is directly electrically connected to the back surface ground electrode 14. In other words, the front surface ground electrode 11 is electrically connected to the back surface ground electrode 14 without passing through the through-ground wiring 15.

The hole Ca1 may be filled with an insulator such as resin. In this case, the airtightness inside the micro relay can be ensured.

Other configurations are the same as those of the transmission line shown in FIGS. 6 and 7, and the description thereof is omitted.

As described above, the silicon substrate 21 has the hole Ca1 penetrating from the first surface F1 to the second surface F2 of the silicon substrate 21. The wiring inclined portion 10a of the signal wiring 10 is disposed on the inclined surface WA1 and is electrically connected to the back electrode 13b. Thereby, the silicon substrate 21 does not need to have a through via. Therefore, the influence of impedance mismatch due to the through via can be reduced. As a result, high-frequency transmission characteristics can be further improved.
(Embodiment 5)
In the fifth embodiment, the silicon substrate 21 has a first recess Ca1, and the first recess Ca1 has a bottom surface BT without penetrating to the second surface F2. Further, the silicon substrate 21 is provided with a second recess Ca2 on the second surface F2. The second recess Ca2 has an inclined surface WA2 and a bottom surface. The back surface ground electrode 14 is disposed on the second surface F2 of the silicon substrate 21 and on the inclined surface WA2 and the bottom surface of the second recess Ca2. FIG. 9A is a cross-sectional view taken along the line DD in FIG. 9B. The back surface ground electrode 14 is disposed on the side opposite to the signal wiring 10 when viewed from the silicon substrate 21.

As shown in FIG. 9A, the back surface ground electrode 14 is separated from the signal wiring 10 by a predetermined distance. This predetermined distance is constant along the longitudinal direction of the signal wiring 10. In other words, the back surface ground electrode 14 is separated from the signal wiring 10 by the thickness of the silicon substrate 21. The thickness of the silicon substrate 21 is constant along the longitudinal direction of the signal wiring 10.

Further, the back surface ground electrode 14a is separated from the signal wiring 10a by a predetermined distance. This predetermined distance is constant along the longitudinal direction of the signal wiring 10. In other words, the back surface ground electrode 14 a is separated from the signal wiring 10 a by the thickness of the silicon substrate 21. The thickness of the silicon substrate 21 is constant along the longitudinal direction of the signal wiring 10. Specifically, the second recess Ca2 is formed on the first surface F1 of the silicon substrate 21 so as to face a region where the first recess Ca1 is not formed. The inclined surface Wa2 is formed at a position facing the inclined surface WA1 of the first recess Ca1.

As shown in the present embodiment, the positions and shapes of the first recess Ca1 and the second recess Ca2 are such that the distance between the back ground electrodes 14, 14a and the signal wirings 10, 10a is along the longitudinal direction of the signal wirings 10, 10a. Adjusted to be constant. As a result, the distance between the signal wirings 10 and 10a and the back ground electrodes 14 and 14a in the coplanar waveguide line is constant. As a result, 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 FIG. 6 and FIG.

Moreover, although Embodiment 5 showed the case where 2nd recessed part Ca2 was formed in the 2nd surface F2 side in the transmission line shown in FIG.6 and FIG.7, the 2nd surface F2 side in the transmission line shown in FIG. Even if the second concave portion Ca2 is formed, a similar effect can be obtained.

In the first to fifth 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). It does not matter. 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, 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 fifth embodiments of the present invention, the micro relay 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, and the like that handle a high frequency electric signal are also included. included.

Thus, it should be understood that the present invention includes various embodiments 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.

Claims (16)

1. A transmission line having a dielectric substrate and signal wiring,
   The dielectric substrate has a first surface and a second surface, and the second surface is located on the opposite side of the first surface;
   The dielectric substrate has a first region on the first surface;
   The dielectric substrate is provided with a back electrode on the second surface,
   The signal wiring is configured to transmit a signal, has a length and a width, has a first end at one end in the length direction, and the first end is the first end. Disposed in a region, the first end is electrically connected to the back electrode,
   The transmission line, wherein the first region overlaps the back electrode in the thickness direction of the dielectric substrate.
   
2. The dielectric substrate has a first recess formed on a first surface thereof, and the first recess defines the first region,
   The transmission line according to claim 1, wherein one end of the signal wiring is disposed on the first inner surface.
   
3. The first inner surface includes a bottom surface;
   The first end of the signal wiring is disposed on the bottom surface;
   The dielectric substrate is provided with a surface ground electrode on the first surface, and the surface ground electrode is electrically insulated from the signal wiring,
   The transmission according to claim 2, wherein the dielectric substrate is provided with a back surface ground electrode on the second surface, and the back surface ground electrode is electrically insulated from the signal wiring. line.
   
4. The first recess has a length along the first surface;
   The bottom surface of the first inner surface has a length along the length direction of the first recess,
   The transmission line according to claim 3, wherein all of the signal wires are disposed on the bottom surface.
   
5. The dielectric substrate has a second recess formed on the second surface thereof, and the second recess is formed to overlap the first recess in the thickness direction of the dielectric substrate, The second recess has a second inner surface;
   The transmission line according to claim 3 or 4, wherein the back ground electrode is formed on the second surface and the second inner surface.
   
6. The transmission line according to claim 5, wherein a peripheral edge of the second concave portion is aligned with a peripheral edge of the first concave portion in a thickness direction of the dielectric substrate.
   
7. The first inner surface has an inclined surface, and the inclined surface is inclined with respect to the first surface so as to intersect at an acute angle with respect to the first surface;
   The transmission line according to claim 2, wherein a part of the first end of the signal wiring is provided on the inclined surface.
   
8. The first recess has an opening area;
   The opening area is formed so as to become smaller from the first surface to the second surface of the dielectric substrate, whereby the first recess has the inclined surface. The transmission line according to claim 7.
   
9. The first inner surface further has a bottom surface,
   The dielectric substrate is provided with a through wiring penetrating from the second surface to the bottom surface, and the through wiring is electrically connected to the back electrode,
   The transmission line according to claim 7 or 8, wherein one end of the signal wiring is disposed on the bottom surface and is electrically connected to the through wiring.
   
10. The transmission line according to claim 9, wherein the dielectric substrate has a through hole extending from the second surface to the bottom surface, and the through wiring is disposed in the through hole.
    
11. The dielectric substrate has a second recess formed on the second surface,
    The dielectric substrate is provided with a back surface ground electrode on the second surface and the second recess, and the back surface ground electrode is electrically insulated from the back surface electrode,
    The back ground electrode is separated from the signal wiring by a predetermined distance in the thickness direction of the dielectric substrate,
    The transmission line according to any one of claims 7 to 10, wherein the predetermined distance is constant over a length direction of the signal wiring.
    
12. The dielectric substrate has a pair of surface ground electrodes,
    The surface ground electrode is provided over the first surface and the inclined surface,
    The surface ground electrodes are located on both sides of the signal wiring, are arranged along the width direction of the signal wiring, and are separated from the signal wiring so as to be electrically insulated from the signal wiring,
    The signal wiring has a wiring inclined portion, and the wiring inclined portion is located on the inclined surface,
    The surface ground electrode has an electrode inclined portion, the electrode inclined portion is located on the inclined surface,
    The wiring inclined portion is separated from the electrode inclined portion by a first distance,
    12. The transmission line according to claim 7, wherein the first distance changes as the surface ground electrode and the signal wiring approach the second surface.
    
13. The dielectric substrate further has a pair of through-ground wirings,
    Each of the pair of through-ground wirings penetrates from the second surface of the dielectric substrate to the first surface,
    The through-ground wiring is located on both sides of the through-wiring, is disposed along the width direction of the signal wiring, and is electrically insulated from the through-wiring,
    The transmission line according to claim 9 or 10, wherein the pair of penetration grounds are electrically connected to the pair of surface ground electrodes, respectively.
    
14. The dielectric substrate has a hole penetrating from the second surface to the first surface,
    The hole has a first inner surface, and the first inner surface defines the first region;
    The transmission line according to claim 1, wherein the signal wiring extends from the first surface to the back electrode through the first inner surface.
    
15. The first inner surface has an inclined surface, and the inclined surface is inclined with respect to the first surface so as to intersect at an acute angle with respect to the first surface;
    The transmission line according to claim 2, wherein a part of the first end of the signal wiring is provided on the inclined surface.
    
16. The transmission line according to claim 14 or 15, wherein the hole is filled with an insulating resin.

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