Waveguide element

Abstract

Provided is a waveguide element in which a resin material substrate can be supported by a supporting substrate and thermal resistance can be reduced. A waveguide element according to an embodiment of the present invention is capable of guiding electromagnetic waves having a frequency of 30 GHz to 20 THz. The waveguide element comprises: a resin material substrate; a conductor layer provided on the upper portion of the resin material substrate; and a supporting substrate positioned on the opposite side of the resin material substrate from the conductor layer wherein the resin material substrate and the supporting substrate are directly bonded.

Description

[Technical Field]

[0001] The present invention relates to a waveguide element. [Background technology]

[0002] Development of waveguide elements is underway as one type of element that guides millimeter waves to terahertz waves. Waveguide elements are expected to be applied and developed in a wide range of fields, such as optical waveguides, next-generation high-speed communications, sensors, laser processing, and solar power generation. As such a waveguide element, for example, a mode converter has been proposed (see Patent Document 1), which includes: an upper substrate that is a flexible substrate; a planar circuit that is provided on the upper substrate and serves as a connection portion for transmitting high-frequency signals; and a substrate that has ground conductor layers on both sides, and the upper substrate and the substrate are bonded together with an adhesive layer made of an organic adhesive such as epoxy. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-236291 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the mode converter described in Patent Document 1, the upper substrate and the substrate are bonded with an organic adhesive, making it difficult to reduce the thermal resistance of the bonded portion. Therefore, when an active element (e.g., an oscillator, a receiver, etc.) is mounted on such a mode converter, the heat transferred from the active element to the upper substrate cannot be dissipated, and the upper substrate may become overheated. In this case, the heat may be transferred to other components (e.g., other active elements, mounted components) connected to the upper substrate, potentially degrading the characteristics of those components. A primary object of the present invention is to provide a waveguide element in which a resin material substrate can be supported by a support substrate and in which thermal resistance can be reduced. [Means for solving the problem]

[0005] [1] A waveguide element according to an embodiment of the present invention is capable of guiding electromagnetic waves with a frequency of 30 GHz or more and 20 THz or less. The waveguide element includes a resin material substrate, a conductor layer provided on the resin material substrate, and a support substrate located on the opposite side of the conductor layer with respect to the resin material substrate. The resin material substrate and the support substrate are directly bonded to each other. [2] The waveguide element according to [1] above may further include a first ground electrode, the first ground electrode being located between the resin material substrate and the support substrate. [3] In the waveguide element described in [2] above, the first ground electrode may be in direct contact with the resin material substrate and the support substrate, and may function as a joining portion joining the resin material substrate and the support substrate. [4] In the waveguide element described in [2] above, the first ground electrode may be in direct contact with the resin material substrate, and the waveguide element may further include a joining portion joining the first ground electrode to the support substrate. [5] In the waveguide element described in [2] above, the first ground electrode may be in direct contact with the support substrate, and the waveguide element may further include a joining portion joining the resin material substrate and the first ground electrode. [6] In the waveguide element according to any one of [1] to [5] above, the conductor layer comprises a signal electrode constituting a transmission line capable of propagating the electromagnetic wave; and the signal electrode and a spaced apart second ground electrode. [7] The waveguide element described in [6] above may further include a third ground electrode, a first via, and a second via. The third ground electrode is located on the opposite side of the support substrate from the first ground electrode. The first via electrically connects the second ground electrode to the third ground electrode and is also electrically connected to the first ground electrode. The second via electrically connects the first ground electrode to the second ground electrode. A plurality of first vias are provided, and the second via is disposed between adjacent first vias among the plurality of first vias. [8] The waveguide element described in [6] above may further include a third ground electrode and a plurality of through-substrate vias. The third ground electrode is located on the opposite side of the support substrate from the first ground electrode. The through-substrate vias electrically connect the first ground electrode and the third ground electrode. The first ground electrode, the third ground electrode, and the plurality of through-substrate vias constitute a substrate-integrated waveguide capable of propagating electromagnetic waves. [9] In the waveguide element according to any one of the above [1] to [8], the thickness t of the resin material substrate may satisfy the following formula (1):

number

[10] In the waveguide element described in [9] above, a in the formula (1) above may be a value of 6 or more.

[11] In the waveguide element according to any one of [1] to

[10] above, the thickness t of the resin material substrate may be 100 μm or less.

[12] In the waveguide element according to any one of [1] to

[11] above, the thickness t of the resin material substrate may be 1 μm or more.

[13] The waveguide element according to [1] or [2] may further include a junction between the resin material substrate and the support substrate. The junction may be a SiO2 layer, an amorphous silicon layer, or a tantalum oxide layer. [Effects of the Invention]

[0006] According to the embodiment of the present invention, it is possible to realize a waveguide element in which a resin material substrate can be supported by a support substrate and in which thermal resistance can be reduced. [Brief explanation of the drawings]

[0007] [Figure 1]FIG. 1 is a schematic perspective view of a waveguide element according to one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of the waveguide element of FIG. 1 taken along line II-II'. [Figure 3] FIG. 3 is a schematic cross-sectional view illustrating an example of the arrangement of the junctions in the waveguide element of FIG. [Figure 4] FIG. 4 is a schematic cross-sectional view illustrating another example of the arrangement of the junctions in the waveguide element of FIG. [Figure 5] FIG. 5 is a schematic cross-sectional view illustrating yet another example of the arrangement of the junctions in the waveguide element of FIG. [Figure 6] FIG. 6 is a schematic perspective view illustrating a modification of the waveguide element of FIG. [Figure 7] 7 is a cross-sectional view of the waveguide element of FIG. 6 taken along line VII-VII'. [Figure 8] FIG. 8 is a schematic perspective view of a waveguide element according to another embodiment of the present invention. [Figure 9] 9 is a cross-sectional view of the waveguide element of FIG. 8 taken along line IX-IX'. [Figure 10] FIG. 10 is a cross-sectional view of the director element of FIG. 8 taken along line XX'. [Figure 11] FIG. 11 is a cross-sectional view of the waveguide element of FIG. 8 taken along the line XI-XI'. [Figure 12] FIG. 12 is a schematic cross-sectional view illustrating a modified example of the shape of the via in the waveguide element of FIG. [Figure 13] FIG. 13 is a schematic cross-sectional view illustrating a modification of the arrangement of vias in the waveguide element of FIG. [Figure 14] FIG. 14 is a schematic cross-sectional view illustrating another modified example of the arrangement of vias in the waveguide element of FIG. [Figure 15] FIG. 15 is a schematic perspective view of a waveguide element according to yet another embodiment of the present invention. [Figure 16] 16 is a cross-sectional view of the waveguide element of FIG. 15 taken along line XVI-XVI'. [Figure 17] FIG. 17 is a schematic perspective view of a waveguide element according to yet another embodiment of the present invention. [Figure 18]18 is a cross-sectional view of the waveguide element of FIG. 17 taken along line XVIII-XVIII'. [Figure 19] FIG. 19 is an exploded perspective view of the director element of FIG. [Figure 20] FIG. 20 is a schematic cross-sectional view illustrating the state in which the conductive pin of FIG. 17 is covered with an insulating material. [Figure 21] FIG. 21 is a schematic perspective view of a waveguide element according to yet another embodiment of the present invention. [Figure 22] 22 is a cross-sectional view of the waveguide element of FIG. 21 taken along line XXII-XXII'. [Figure 23] FIG. 23 is a schematic cross-sectional view of a waveguide element according to yet another embodiment of the present invention. [Figure 24] FIG. 24 is a schematic cross-sectional view illustrating a modification of the waveguide element of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments. A. Overall configuration of the waveguide element A-1. Overall configuration of the director element 100 FIG. 1 is a schematic perspective view of a waveguide element according to one embodiment of the present invention; FIG. 2 is a cross-sectional view of the waveguide element of FIG. 1 taken along line II-II'. The illustrated waveguide element 100 can guide electromagnetic waves with frequencies between 30 GHz and 20 THz, in other words, millimeter waves to terahertz waves. Note that millimeter waves are typically electromagnetic waves with frequencies between 30 GHz and 300 GHz, and terahertz waves are typically electromagnetic waves with frequencies between 300 GHz and 20 THz. The waveguide element 100 comprises a resin material substrate 1, a conductor layer 2, and a support substrate 7. The conductor layer 2 is provided on top of the resin material substrate 1. The support substrate 7 is located on the opposite side of the resin material substrate 1 from the conductor layer 2. The resin material substrate 1 and the support substrate 7 are directly bonded together. This allows the support substrate 7 to support the resin material substrate 1. This improves the mechanical strength of the waveguide element.

[0009] As used herein, "direct bonding" refers to bonding two layers or substrates without the use of an organic adhesive (e.g., a resin adhesive). The form of direct bonding can be appropriately determined depending on the configuration of the layers or substrates to be bonded. Furthermore, the interface bonded by direct bonding is typically amorphous. Therefore, the thermal resistance of the bonded interface can be significantly reduced compared to resin bonding (resin bonding) using an organic adhesive. As a result, when an active element (e.g., an oscillator, a receiver, etc.) is mounted on the waveguide element, even if heat generated by the active element is transferred to the resin material substrate, such heat can be smoothly dissipated from the resin material substrate to the package via the support substrate. As a result, heating of the resin material substrate can be suppressed, and deterioration of the characteristics of other components (e.g., other active elements, mounted components) connected to the resin material substrate can be suppressed. The form of direct bonding can also include bonding between the support substrate and the resin material substrate via the first ground electrode 3 and / or the bonding portion 8 described below. Furthermore, by directly bonding the resin material substrate and the support substrate together, peeling in the waveguide element can be effectively suppressed, and as a result, damage (e.g., cracks) to the resin material substrate caused by such peeling can be effectively suppressed.

[0010] Direct bonding can be achieved, for example, by the following procedure: -6A neutralization beam is irradiated onto the bonding surfaces of the components (layers or substrates) to be bonded at a pressure of about 100 Pa. This activates each bonding surface. Next, the activated bonding surfaces are brought into contact with each other in a vacuum atmosphere and bonded at room temperature. The load during this bonding can be, for example, 100 N to 20,000 N. In one embodiment, when performing surface activation using the neutralization beam, an inert gas is introduced into a chamber, and a high voltage is applied from a DC power supply to an electrode placed in the chamber. With this configuration, an electric field generated between the electrode (positive electrode) and the chamber (negative electrode) causes electrons to move, generating a beam of atoms and ions from the inert gas. Of the beams that reach the grid, the ion beam is neutralized by the grid, and a beam of neutral atoms is emitted from the fast atom beam source. The atomic species constituting the beam are preferably inert gas elements (e.g., argon (Ar) and nitrogen (N)). The voltage during activation by beam irradiation is, for example, 0.5 kV to 2.0 kV, and the current is, for example, 50 mA to 200 mA. The direct bonding method is not limited to this, and other methods such as surface activation using FAB (Fast Atom Beam) or an ion gun, atomic diffusion, and plasma bonding can also be used.

[0011] In one embodiment, the waveguide element 100 includes a first ground electrode 3. The first ground electrode 3 is located between the resin material substrate 1 and the support substrate 7. This prevents the electric field generated when a voltage is applied to the conductor layer from leaking from the resin material substrate to the support substrate. This prevents substrate resonance and stray capacitance, thereby reducing propagation loss.

[0012] In the illustrated example, the first ground electrode 3 is in direct contact with the resin material substrate 1 and the support substrate 7, and functions as a joint that joins the resin material substrate 1 and the support substrate 7. In this embodiment, only the first ground electrode 3 is provided between the resin material substrate 1 and the support substrate 7. In other words, the resin material substrate 1 and the support substrate 7 are directly joined via only the first ground electrode 3. With this configuration, the thermal resistance of the waveguide element can be stably reduced.

[0013] As shown in FIG. 3 , in one embodiment, the waveguide element 100 further includes a bonding portion 8. The bonding portion 8 is provided between the resin material substrate 1 and the support substrate 7. The first ground electrode 3 may be formed on the surface of the resin material substrate 1 opposite to the conductor layer 2, and may be in direct contact with the resin material substrate 1. In the embodiment shown in FIG. 3 , the bonding portion 8 is located between the first ground electrode 3 and the support substrate 7, and bonds the first ground electrode 3 and the support substrate 7 together. 4, the first ground electrode 3 may be formed on the surface of the support substrate 7 facing the resin material substrate, and may be in direct contact with the support substrate 7. In the embodiment shown in FIG. 4, the joint 8 is located between the resin material substrate 1 and the first ground electrode 3, and joins the resin material substrate 1 and the first ground electrode 3 together. 3 and 4, a first ground electrode 3 and a joint 8 are provided between the resin material substrate 1 and the support substrate 7. That is, the resin material substrate 1 and the support substrate 7 are directly joined via the first ground electrode 3 and the joint 8. These embodiments also make it possible to stably reduce the thermal resistance of the waveguide element.

[0014] As shown in Fig. 5, the waveguide element 100 does not necessarily have to include the first ground electrode 3. In the embodiment shown in Fig. 5, the bonding portion 8 is located between the resin material substrate 1 and the support substrate 7, bonding the resin material substrate 1 and the support substrate 7 together. In this embodiment, only the bonding portion 8 is provided between the resin material substrate 1 and the support substrate 7. In other words, the resin material substrate 1 and the support substrate 7 are directly bonded together only via the bonding portion 8. This also makes it possible to stably reduce the thermal resistance of the waveguide element.

[0015] As described above, it is preferable that no organic material (such as an adhesive) other than the resin material substrate 1 is present between the conductor layer and the support substrate. This reduces the thermal resistance at the interface between the resin material substrate 1 and the support substrate 7, and suppresses deterioration of the characteristics of the active elements and mounted components. A structure in which no organic material (such as an adhesive) other than the resin material substrate 1 is present can be obtained by directly bonding the resin material substrate 1 and the support substrate 7 (either or both of the resin material substrate 1 and the support substrate 7 may or may not have a first ground electrode formed thereon).

[0016] 1 and 2, the conductor layer 2 typically includes a signal electrode 21. The signal electrode 21 constitutes a transmission line capable of propagating the above-described electromagnetic waves. The signal electrode 21 typically has a linear shape extending in a predetermined direction. The width w of the signal electrode 21 is, for example, 2 μm or more, preferably 20 μm or more, and for example, 200 μm or less, preferably 150 μm or less. 1, the signal electrode 21 extends over the entire waveguide element 100, but the length of the signal electrode 21 may be any appropriate dimension depending on the application of the waveguide element. Also, a plurality of signal electrodes may be provided in the waveguide element so as to be aligned in the waveguiding direction.

[0017] In one embodiment, the conductor layer 2 further includes a second ground electrode 22 in addition to the signal electrode 21. The second ground electrode 22 is disposed at a distance from the signal electrode 21 in a direction intersecting (preferably perpendicular to) the longitudinal direction of the signal electrode 21. As a result, a gap (slit) extending in the longitudinal direction of the signal electrode 21 is formed between the signal electrode 21 and the second ground electrode 22. The width g of the gap (slit) is, for example, 2 μm or more, preferably 5 μm or more, and, for example, 100 μm or less, preferably 80 μm or less.

[0018] In the illustrated example, the conductor layer 2 includes a signal electrode 21 and two second ground electrodes 22a and 22b. The second ground electrode 22a is located on the opposite side of the signal electrode 21 from the second ground electrode 22b. In the waveguide elements shown in FIGS. 1 to 14, the signal electrode 21 and the two second ground electrodes 22a and 22b form a coplanar line, which is an example of a transmission line. That is, the signal electrode 21 and the second ground electrode 22 are coplanar electrodes. In such a coplanar line, when a voltage is applied to the conductor layer 2, an electric field is generated between the signal electrode 21 and the second ground electrode 22. When the high-frequency electromagnetic wave described above is input to the waveguide element, it couples with the electric field generated between the signal electrode 21 and the second ground electrode 22 and propagates through the resin material substrate 1.

[0019] 6 and 7, the second ground electrode 22 may be electrically connected to the first ground electrode 3. When the second ground electrode 22 is electrically connected to the first ground electrode 3, the ground can be strengthened and stray capacitance due to surrounding lines and elements can be suppressed. In the illustrated example, a plurality of via holes are formed in the resin material substrate 1, and the first ground electrode 3 and the second ground electrode 22a, and the first ground electrode 3 and the second ground electrode 22b are short-circuited by vias 6 located in each via hole. The arrangement of the plurality of vias 6 (via holes) is not particularly limited. In the illustrated example, the plurality of vias 6 (via holes) are aligned in the longitudinal direction of the signal electrode 21. The row of vias 6 short-circuiting the first ground electrode 3 and the second ground electrode 22a and the row of vias 6 short-circuiting the first ground electrode 3 and the second ground electrode 22b are spaced apart in a direction intersecting the longitudinal direction of the signal electrode 21. The vias 6 are typically conductive films formed on the entire inner surface of the via holes. The vias 6 are made of a conductive material, typically a metal (described later) similar to that of the conductor layer 2. The via holes may be filled entirely with a conductive material. When the vias are formed of a metal film, the interiors of the vias may be filled with a conductive material. The conductive material may be the same metal as the vias or may be a different material such as a conductive paste.

[0020] A-2. Overall configuration of the director element 101 8 is a schematic perspective view of a waveguide element according to another embodiment of the present invention; FIG. 9 is a cross-sectional view of the waveguide element of FIG. 8 taken along line IX-IX'; FIG. 10 is a cross-sectional view of the waveguide element of FIG. 8 taken along line XX'; and FIG. 11 is a cross-sectional view of the waveguide element of FIG. 8 taken along line XI-XI'.

[0021] The illustrated waveguide element 101 further includes a third ground electrode 4 in addition to the resin material substrate 1, the conductor layer 2, the first ground electrode 3, and the support substrate 7. Although not shown, the waveguide element 101 may also include the above-mentioned joint. The third ground electrode 4 is located on the opposite side of the support substrate 7 from the first ground electrode 3. In the illustrated example, the third ground electrode 4 is formed on the surface of the support substrate 7 opposite to the first ground electrode 3 and is in direct contact with the support substrate 7. With this configuration, the first ground electrode is located between the resin material substrate and the support substrate, and the third ground electrode is located on the opposite side of the support substrate from the first ground electrode, thereby further suppressing leakage of electromagnetic waves to the support substrate.

[0022] In one embodiment, the director element 101 further includes a first via 5 and a second via 6. As shown in FIG. 9, the first via 5 electrically connects the second ground electrode 22 and the third ground electrode 4, and is also electrically connected to the first ground electrode 3. The director element 101 includes a plurality of the above-described first vias 5 (see FIG. 8). As shown in FIG. 10, the second via 6 electrically connects the first ground electrode 3 and the second ground electrode 22. The second via 6 is disposed between adjacent first vias 5 (see FIG. 8). With this configuration, the first via electrically connects the first ground electrode, the second ground electrode, and the third ground electrode. This strengthens the ground and reduces stray capacitance due to surrounding lines and elements. Furthermore, the support substrate can be provided with excellent heat dissipation capabilities, and transmission in higher modes can be suppressed. In addition, the relative positional accuracy of the portion of the first via located between the first ground electrode and the second ground electrode and the portion located between the first ground electrode and the third ground electrode can be easily ensured, thereby suppressing the occurrence of ripples. Furthermore, since the second vias are disposed between adjacent first vias, the pitch of the first and second vias in the resin material substrate can be made smaller than the pitch of the first vias in the support substrate, so that the strength of the resin material substrate can be sufficiently ensured even if the thickness of the resin material substrate is reduced.

[0023] A-2-1. First via 9, in the waveguide element 101, the first vias 5 are provided on both sides of the signal electrode 21 in a direction intersecting (preferably perpendicular to) the longitudinal direction of the signal electrode 21. Hereinafter, the first vias electrically connecting the second ground electrode 22a and the third ground electrode 4 may be referred to as the first via 5a, and the first vias electrically connecting the second ground electrode 22b and the third ground electrode 4 may be referred to as the first via 5b, to distinguish them from each other. The first via 5a is in contact with the second ground electrode 22a and the third ground electrode 4, and extends continuously between the second ground electrode 22a and the third ground electrode 4. The first via 5b is in contact with the second ground electrode 22b and the third ground electrode 4, and extends continuously between the second ground electrode 22b and the third ground electrode 4. Each of the first vias 5a and 5b penetrates the first ground electrode 3 and is in contact with the first ground electrode 3. Note that the waveguide element may include only one of the first vias 5a and 5b.

[0024] The first via 5 is typically a conductive film. The first via 5 is made of a conductive material, typically a metal (described later) similar to that of the conductor layer 2. The shape of the first via 5 corresponds to the shape of the first via hole 51 in which it is disposed. That is, the waveguide element 101 has a plurality of first via holes 51 corresponding to the plurality of first vias 5. The first via holes 51 penetrate the resin material substrate 1, the first ground electrode 3, and the support substrate 7. The first via hole 51 typically has a circular shape when viewed from above the resin material substrate 1. When the first via hole has a circular shape, the inner diameter of the first via hole is, for example, 10 μm or more, preferably 20 μm or more, and for example, 200 μm or less, preferably 100 μm or less, and more preferably 80 μm or less.

[0025] 9, the first via hole 51 has a circular shape when viewed from above the resin material substrate 1, and penetrates the resin material substrate 1, the first ground electrode 3, and the support substrate 7 linearly in the thickness direction of the resin material substrate 1. When the first via hole is circular and linear, the first via 5 has a columnar or cylindrical shape extending in the thickness direction of the resin material substrate 1. In this case, the range of the outer diameter of the first via 5 is the same as the range of the inner diameter of the first via hole described above.

[0026] 12, the first via hole 51 may have a circular shape when viewed from above the resin material substrate 1, and may have a tapered shape that becomes smaller in diameter as it approaches the first ground electrode 3. Although not shown, the first via hole 51 may also have a circular shape when viewed from above the resin material substrate 1, and may have a tapered shape that becomes larger in diameter as it approaches the first ground electrode 3. When the first via hole has a tapered shape, it is possible to provide the following features: it is easy to form a conductive film in the first via, and it is easy to ensure the strength of the support substrate. Furthermore, the first via may be formed so that a conductive material is embedded in the first via hole. When the first via hole is circular and tapered, the first via 5 preferably has an hourglass shape in which the diameter is small at the portion in contact with the first ground electrode 3 and increases with increasing distance from the first ground electrode 3. In other words, the first via 5 preferably has a shape in which the apexes of two cones are joined. In this case, the maximum outer diameter of the first via 5 falls within the above-mentioned range. In one embodiment, the outer diameter of one end of the first via 5 in contact with the second ground electrode 22 is smaller than the outer diameter of the other end of the first via 5 in contact with the third ground electrode 4. The taper angle of the first via 5 on the conductor layer 2 side relative to the first ground electrode is smaller than the taper angle on the third ground electrode side relative to the first ground electrode. In the illustrated example, the second and third ground electrodes are each formed to block the first via hole, but the configuration of the second and third ground electrodes is not limited to this. Each of the second and third ground electrodes only needs to be electrically connected to the first via, and may be open without blocking the first via hole.

[0027] 8 to 12, the plurality of first vias 5a are arranged at intervals in the longitudinal direction of the signal electrode 21. The direction in which the plurality of first vias 5a are arranged is not limited to the longitudinal direction of the signal electrode 21. As shown in FIG. 14, the plurality of first vias 5a may be arranged at intervals in a direction intersecting (preferably perpendicular to) the longitudinal direction of the signal electrode 21. The waveguide element may also have a plurality of rows of first vias 5a arranged in the longitudinal direction of the signal electrode 21 in a direction intersecting (preferably perpendicular to) the longitudinal direction of the signal electrode 21.

[0028] As shown in FIG. 12, the pitch P1 of the multiple first vias 5a (the distance between the centers of adjacent first vias 5a) is, for example, 40 μm or more, preferably 60 μm or more, and for example, 600 μm or less, preferably 400 μm or less, and more preferably 200 μm or less. Moreover, the waveguide element 101 may include a plurality of first vias 5b, similar to the first via 5a.

[0029] A-2-2. Second via As shown in FIG. 8 , in the waveguide element 101, the second vias 6 are provided on both sides of the signal electrode 21 in a direction intersecting (preferably perpendicular to) the longitudinal direction of the signal electrode 21. Hereinafter, the second vias electrically connecting the second ground electrode 22a and the first ground electrode 3 may be referred to as the second via 6a, and the second vias electrically connecting the second ground electrode 22b and the first ground electrode 3 may be referred to as the second via 6b, to distinguish them from each other. The second via 6a is in contact with the second ground electrode 22a and the first ground electrode 3, but is not in contact with the third ground electrode 4. The second via 6b is in contact with the second ground electrode 22b and the first ground electrode 3, but is not in contact with the third ground electrode 4. Note that the waveguide element may include only one of the second vias 6a and 6b.

[0030] The second via 6 is typically a conductive film. The second via 6 is made of a conductive material, typically a metal (described later) similar to that of the first via 5. The shape of the second via 6 corresponds to the shape of the second via hole 61 in which it is disposed. In other words, the waveguide element 101 has a second via hole 61 corresponding to the second via 6.

[0031] 10, the second via hole 61 penetrates at least the resin material substrate 1 but does not penetrate the support substrate 7. The second via hole 61 typically has a circular shape when viewed from above the resin material substrate 1. When the second via hole has a circular shape, the range of the inner diameter of the second via hole is, for example, the same as the range of the inner diameter of the first via hole described above.

[0032] The second via hole 61 in the illustrated example penetrates the resin material substrate 1 linearly in the thickness direction of the resin material substrate 1, but does not penetrate the first ground electrode 3. When the second via hole 61 is circular and linear, the second via 6 has a columnar or cylindrical shape extending in the thickness direction of the resin material substrate 1. In this case, the range of the outer diameter of the second via 6 is the same as the range of the inner diameter of the second via hole described above.

[0033] As shown in FIG. 12 , the second via hole 61 may have a conical shape that tapers away from the conductor layer 2. The second via hole 61 in the illustrated example penetrates the resin material substrate 1 and the first ground electrode 3, and its tip reaches the support substrate 7. When the second via hole 61 has a conical shape, the second via 6 preferably has a conical shape similar to that of the second via hole 61. In this case, the maximum outer diameter of the second via 6 is within the range of the inner diameter of the second via hole. Furthermore, the apex of the second via 6 (the end of the second via 6 opposite the conductor layer 2) may reach the support substrate 7. In the illustrated example, the second ground electrode is formed so as to block the second via hole, but the configuration of the second ground electrode is not limited to this. The second ground electrode only needs to be electrically connected to the second via, and may be open without blocking the second via hole.

[0034] 11 to 14, the second vias 6 are arranged between adjacent first vias 5 among a plurality of first vias 5 arranged in a predetermined direction. The second vias 6 are typically located in the center of the gap between the adjacent first vias 5. The illustrated waveguide element 101 has a plurality of second vias 6 (a plurality of second vias 6a and a plurality of second vias 6b). The second vias 6 shown in FIGS. 8 to 13 are arranged between the first vias 5 adjacent to each other in the longitudinal direction of the signal electrode 21. The second vias 6 shown in FIG. 14 are arranged between the first vias 5 adjacent to each other in a direction intersecting (preferably perpendicular to) the longitudinal direction of the signal electrode 21. Furthermore, the second vias 6 can be arranged at any appropriate position between adjacent first vias 5. A second via 6 may be arranged every n first vias 5 in the direction in which the multiple first vias are arranged. n is, for example, 1 to 5, and preferably 1 or 2. More preferably, the first vias 5 and the second vias 6 are arranged alternately. Furthermore, the multiple second vias 6 may all be arranged between adjacent first vias 5, as shown in FIGS. 11 and 12, or may include a second via 6 that is not arranged between first vias 5, as long as at least one second via 6 is arranged between adjacent first vias 5, as shown in FIG. 13.

[0035] As shown in Figure 12, the pitch P2 between adjacent first vias 5 and second vias 6 (the distance between the centers of adjacent first vias 5a and second vias 6a) is substantially half the pitch P1 (the distance between the centers of adjacent first vias 5a), and is, for example, 25 μm or more, preferably 60 μm or more, and for example, 600 μm or less, preferably 400 μm or less, and more preferably 200 μm or less. In this way, by arranging the second vias 6 between adjacent first vias 5, the pitch P2 of the first vias 5 and the second vias 6 in the resin material substrate 1 can be made smaller than the pitch P1 of the first vias 5 in the support substrate 7. Therefore, even if the resin material substrate is made thinner, the strength of the resin material substrate can be sufficiently ensured.

[0036] A-2-3. Modification of the director element 101 Although not shown, the waveguide element 101 may include a third via, instead of the first via 5, that electrically connects the first ground electrode 3 and the third ground electrode 4. That is, the waveguide element 101 may include a second via 6 that connects the first ground electrode 3 and the second ground electrode 22 and a third via that connects the first ground electrode 3 and the third ground electrode 4. However, such a configuration may result in a decrease in the relative positional accuracy between the second via that connects the first ground electrode and the second ground electrode and the third via that connects the first ground electrode and the third ground electrode. In this case, a large misalignment between the second and third vias may cause ripples in the frequency characteristics. Therefore, it is preferable that the waveguide element 101 include the first via 5, since this suppresses ripples. Furthermore, a waveguide element that includes a first via can be manufactured more easily than a waveguide element that includes both the second and third vias.

[0037] Although not shown, the waveguide element 101 may include the first via 5 but not the second via 6. However, as shown in FIG. 12 , if the first via hole 51 has a tapered shape that increases in diameter with increasing distance from the first ground electrode 3 and the thickness of the support substrate 7 is greater than that of the resin material substrate 1, the outer diameter of the other end of the first via 5 that contacts the third ground electrode 4 may be larger than the outer diameter of the one end of the first via 5 that contacts the second ground electrode 22. In this case, if the pitch between the multiple first vias 5 is narrowed to the pitch P2 described above without providing the second vias 6, the other ends of the first vias 5 may interfere with each other. Therefore, it is preferable that the waveguide element 101 include the first via 5 and the second via 6 and that the second via 6 be disposed between adjacent first vias 5, since this suppresses interference between the first vias 5.

[0038] A-3. Overall configuration of director element 102 FIG. 15 is a schematic perspective view of a waveguide element according to yet another embodiment of the present invention; FIG. 16 is a cross-sectional view of the waveguide element of FIG. 15 taken along line XVI-XVI'. In the director element 102, the signal electrode 21, together with the first ground electrode 3, constitutes a microstrip line, which is an example of a transmission line. That is, the signal electrode 21 and the first ground electrode 3 are microstrip type electrodes. Although not shown, the director element 102 may also include the above-mentioned junction. When the signal electrode 21 is a microstrip electrode, the width w of the signal electrode 21 is, for example, 100 μm or more, preferably 300 μm or more, and for example, 800 μm or less, preferably 500 μm or less. When the signal electrode and the first ground electrode are microstrip type electrodes, the above-mentioned high-frequency electromagnetic waves are coupled with the electric field generated between the signal electrode 21 and the first ground electrode 3 and propagate through the resin material substrate 1.

[0039] A-4. Overall configuration of director element 103 17 is a schematic perspective view of a waveguide element according to yet another embodiment of the present invention; FIG. 18 is a cross-sectional view of the waveguide element of FIG. 17 taken along line XVIII-XVIII'; and FIG. 19 is an exploded perspective view of the waveguide element of FIG. 17. The illustrated waveguide element 103 includes the resin material substrate 1, the conductor layer 2, the first ground electrode 3, the support substrate 7, and the third ground electrode 4, as well as a plurality of through-substrate vias 9. Although not shown, the waveguide element 103 may also include the above-described junctions. Each of the plurality of through-substrate vias 9 electrically connects the first ground electrode 3 and the third ground electrode 4. The first ground electrode 3, the third ground electrode 4, and the plurality of through-substrate vias 9 form a substrate integrated waveguide (hereinafter referred to as SIW) capable of propagating electromagnetic waves. This allows the SIW to be provided on the support substrate, enabling the support substrate to be effectively used as a waveguide.

[0040] In the illustrated example, the signal electrode 21, together with the first ground electrode 3, constitutes a microstrip line as an example of a transmission line. In one embodiment, the second ground electrode 22 is the first ground electrode described above. 2In addition to the ground electrode 22a and the second ground electrode 22b, a second ground electrode 22c is further included. 2 One end of the signal electrode 21 is located between the ground electrode 22a and the second ground electrode 22b. 2 The ground electrode 22a and the second ground electrode 22b may be electrically connectable to an external element (not shown). The second ground electrode 22c is disposed at a predetermined distance from the other end of the signal electrode 21. The second ground electrode 22c has a substantially C-shape when viewed from above, and surrounds the other end of the signal electrode 21. The conductor layer 2 does not necessarily have to include the second ground electrode 22c. The signal electrode 21 may have a second ground electrode 22c. 2 The ground electrode 22a and the second ground electrode 22b may together form a coplanar electrode, which is an example of a transmission line.

[0041] Furthermore, the director element 103 may further include the above-mentioned vias 6. This strengthens the ground and reduces stray capacitance due to surrounding lines and elements. In the illustrated example, each of the second ground electrodes 22a, 22b, and 22c is electrically connected to the first ground electrode 3 by a plurality of vias 6.

[0042] Each of the plurality of through-substrate vias 9 penetrates the support substrate 7 in the thickness direction and is periodically arranged in the support substrate 7. Typically, the plurality of through-substrate vias 9 includes a first via row 9a and a second via row 9b. Each of the first via row 9a and the second via row 9b is made up of a plurality of through-substrate vias 9 arranged at intervals in a predetermined direction. The second via row 9b is located away from the first via row 9a in a direction perpendicular to the direction in which the first via row 9a extends. In one embodiment, an area of ​​the support substrate 7 surrounded by the first ground electrode 3, the third ground electrode 4, the first via row 9a, and the second via row 9b functions as an SIW.

[0043] As shown in FIG. 18 , the through-substrate via 9 is made of a conductive material, typically a metal (described later) similar to that of the conductor layer 2. The through-substrate via 9 is disposed in a substrate via hole 91. That is, the director element 103 has a plurality of substrate via holes 91 corresponding to the plurality of through-substrate vias 9. In the illustrated example, the substrate via hole 91 collectively penetrates the first ground electrode 3, the support substrate 7, and the third ground electrode 4. The through-substrate via 9 is typically a conductive film formed on the entire inner surface of the substrate via hole 91. Note that the substrate via hole 91 may penetrate only the support substrate without penetrating the first and third ground electrodes. In this case, the through-substrate via is filled in the substrate via hole so as to contact the first and third ground electrodes. Furthermore, when the through-substrate via 9 that electrically connects the first and third ground electrodes 3 and 4 is formed of a conductive film, its interior may be filled with a material such as resin.

[0044] In the director element 103, the transmission line and the SIW formed by the signal electrode 21 may be independent of each other, or may be coupled to each other so that electromagnetic waves can propagate through them. In one embodiment, the transmission line (typically a microstrip transmission line) formed by the signal electrode 21 and the SIW are coupled by a conductor pin 25. This allows the propagation mode of the electromagnetic wave to be converted between a transmission line mode and a waveguide mode. For example, an electromagnetic wave (signal) in the transmission line mode propagating through a resin material substrate can be converted into an electromagnetic wave in the waveguide mode propagating through a support substrate via the conductor pin. The support substrate can function as an antenna that spatially radiates electromagnetic waves propagating in the waveguide mode in the in-plane direction of the substrate.

[0045] The conductor pin 25 extends from the signal electrode 21 through the resin material substrate 1 to the SIW in the support substrate 7. The conductor pin 25 can serve as a propagation medium for electromagnetic waves. The conductor pin 25 is made of a conductive material, typically made of the same metal (described later) as the conductor layer 2. In the illustrated example, the conductor pin 25 extends in the thickness direction of the resin material substrate 1. The conductor pin 25 may have a columnar shape, such as a cylindrical shape, or a hollow cylindrical shape, such as a cylindrical shape. The base end of the conductor pin 25 is connected to the end of the signal electrode 21. The free end of the conductor pin 25 is inserted into a recess 71 formed in the support substrate 7 (see FIG. 19 ). The recess 71 is located between the first via row 9a and the second via row 9b. The portion of the conductor pin 25 between the base end and the free end is inserted into an opening 31 of the first ground electrode 3. The conductive pin 25 is preferably insulated from the first ground electrode 3. In one embodiment, as shown in FIG. 18 , the opening 31 forms an air layer around the conductive pin 25. The opening 31 is larger than the outer shape of the conductive pin 25, and the entire periphery of the opening 31 is separated from the conductive pin 25. This insulates the conductive pin from the first ground electrode, thereby stably insulating the signal electrode and the first ground electrode. In addition, substrate resonance due to leakage of the electric field to the support substrate can be further suppressed. Furthermore, the influence of dielectric loss can be suppressed compared to a structure in which the air layer is filled with resin.

[0046] 20, the periphery of the conductive pin 25 may be covered with an insulating material 15. This also insulates the conductive pin from the first ground electrode. Examples of insulating materials include resin and SiO2.

[0047] A-5. Overall configuration of director element 104 Fig. 21 is a schematic perspective view of a waveguide element according to another embodiment of the present invention, and Fig. 22 is a cross-sectional view of the waveguide element of Fig. 21 taken along line XXII-XXII'. Note that, for convenience, the second ground electrode and vias are omitted from Fig. 21. The director element 104 includes a plurality of signal electrodes 21 spaced apart from one another. Therefore, the director element 104 includes a plurality of transmission lines corresponding to the signal electrodes. In the illustrated example, the director element 104 includes a conductor layer 2 including a first signal electrode 21a and a second signal electrode 21b, a first conductor pin 25a, and a second conductor pin 25b. The first signal electrode 21a and the first ground electrode 3 form a first transmission line, and the second signal electrode 21b and the first ground electrode 3 form a second transmission line. The first conductor pin 25a couples the SIW, which includes the first ground electrode 3, the third ground electrode 4, and the plurality of through-substrate vias 9, to the first transmission line. The second conductor pin 25b couples the SIW, which includes the first ground electrode 3, the third ground electrode 4, and the plurality of through-substrate vias 9, to the second transmission line. As a result, in one embodiment, an electromagnetic wave (signal) in a transmission line mode propagating through the resin material substrate can be converted to an SIW mode via the first conductor pin, then propagated through the support substrate in the SIW mode, and then converted back to a transmission line mode propagating through the resin material substrate via the second conductor pin. In this embodiment, the electromagnetic wave propagated through the resin material substrate can be emitted from an antenna element provided on the resin material substrate.

[0048] A-6. Overall configuration of director element 105 FIG. 23 is a schematic cross-sectional view of a waveguide element according to yet another embodiment of the present invention; and FIG. 24 is a schematic cross-sectional view illustrating a modification of the waveguide element of FIG. The above-described waveguide element includes one support substrate 7, but the number of support substrates 7 is not particularly limited. In the waveguide element 105, a plurality of support substrates 7 are arranged at intervals in the thickness direction of the resin material substrate 1, and each of the plurality of support substrates 7 is provided with a substrate integrated waveguide (SIW). With this configuration, antenna portions that radiate electromagnetic waves in SIW mode can be arrayed in the thickness direction. Therefore, such a waveguide element can be used as a phased array antenna in wireless communication. Note that, when multiple substrates that transmit signals (electromagnetic waves) are integrated, heat generation from the waveguide element can be a problem. However, in the above-described embodiment, the resin material substrate and the support substrate are directly bonded, and a through-substrate via that penetrates the support substrate is connected to a ground electrode, allowing heat to be smoothly dissipated from the waveguide element.

[0049] 23 , in the waveguide element 105, a third ground electrode 4 is disposed between adjacent ones of the plurality of support substrates 7. As a result, the SIW provided on each support substrate 7 is composed of metal layers (i.e., the first ground electrode 3 and the third ground electrode 4, or two third ground electrodes 4) disposed on both sides of the support substrate 7 and a plurality of through-substrate vias 9 that penetrate the support substrate 7.

[0050] 24 , in a waveguide element 105, a plurality of waveguide units 12 including SIW may be arranged at intervals in the thickness direction of a resin material substrate 1. Each of the plurality of waveguide units 12 includes a first ground electrode 3, a support substrate 7, a third ground electrode 4, and a plurality of through-substrate vias 9. A spacer substrate 13 may be provided between adjacent ones of the plurality of support substrates 7. In one embodiment, the spacer substrate 13 is disposed between adjacent waveguide units 12. By providing the spacer substrate, the spacing between the antenna portions on the plurality of support substrates can be adjusted. In particular, adjusting the spacing between the plurality of antenna portions to λ / 2 allows the radiation angle of the electromagnetic waves to be sufficiently scanned. Typical materials for the spacer substrate include the same resin materials (described below) as those for the resin material substrate.

[0051] Furthermore, a waveguide element having multiple SIWs preferably includes the same number of signal electrodes 21 and conductor pins 25 as the number of SIWs. Each conductor pin 25 couples the transmission path formed by each signal electrode 21 with the corresponding SIW. The conductor pin 25 extends from the corresponding signal electrode 21 through the resin material substrate 1, is inserted into the opening 31 of the first ground electrode 3, and further penetrates the support substrate 7, the third ground electrode 4, and the spacer substrate 13 as necessary to reach the corresponding support substrate 7. This configuration is relatively easy to fabricate, and allows a signal (electromagnetic wave) from an external signal source X placed on the resin material substrate to easily propagate to the SIW of each support substrate.

[0052] In this specification, the term "waveguide element" encompasses both a wafer on which at least one waveguide element is formed (waveguide element wafer) and chips obtained by cutting the waveguide element wafer. Specific configurations of the resin material substrate, the conductor layer, the first ground electrode, the third ground electrode, the support substrate, and the bonding portion will be described below.

[0053] B. Resin material substrate 1, the resin material substrate 1 has an upper surface on which a conductor layer 2 is provided, and a lower surface located within the composite substrate. The thickness of the resin material substrate 1 satisfies, for example, the following formula (1).

number

[0054] In one embodiment, in the above formula (1), a represents a numerical value of 6 or more. When the thickness of the resin material substrate satisfies the formula (1) where a is a value of 6 or more, it is possible to stably reduce the propagation loss when guiding the above-mentioned high-frequency electromagnetic waves.

[0055] The relative dielectric constant ε of the resin material substrate 1 at 150 GHz is typically 1.5 or more, and typically 4.0 or less, preferably 3.5 or less, and more preferably 3.0 or less. The dielectric loss tangent (dielectric loss) tan δ of the resin material substrate 1 at 150 GHz is typically 0.01 or less, preferably 0.005 or less, and more preferably 0.002 or less. If the dielectric loss tangent is in this range, the propagation loss in the waveguide can be reduced. The smaller the dielectric loss tangent, the more preferable it is. The dielectric loss tangent can be, for example, 0.0001 or more. When the dielectric constant ε and dielectric loss tangent (dielectric loss) tanδ of the resin material substrate are within the above ranges, the propagation loss can be more stably reduced when guiding the above-mentioned high-frequency electromagnetic waves (particularly electromagnetic waves of 150 GHz or higher). The dielectric constant ε and dielectric loss tangent (dielectric loss) tanδ can be measured by terahertz time-domain spectroscopy. In this specification, when the measurement frequency for the dielectric constant and dielectric loss tangent is not specified, the dielectric constant and dielectric loss tangent refer to the dielectric constant and dielectric loss tangent at 150 GHz.

[0056] The thickness of the resin material substrate 1 satisfying the above formula (1) is specifically 1 μm or more, preferably 2 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more, and is, for example, 1700 μm or less, preferably 500 μm or less, more preferably 200 μm or less, and even more preferably 100 μm or less. From the viewpoint of miniaturization by reducing the size of the electrodes, the thickness of the resin material substrate 1 is preferably 80 μm or less, and even more preferably 60 μm or less. Furthermore, when the frequency of the electromagnetic waves propagating through the waveguide element is 30 GHz or more and 5 THz or less, the thickness of the resin material substrate 1 is preferably 10 μm or more. To ensure strength, the thickness of the resin material substrate 1 is preferably 30 μm or more, and even more preferably 40 μm or more. If the thickness of the resin material substrate 1 falls below the above-mentioned lower limit, the thickness and width of the electrodes constituting the waveguide element will be reduced to about several μm, which will increase the propagation loss due to the skin effect and significantly reduce the tolerance of line performance due to manufacturing variations. When the thickness of the resin material substrate 1 is equal to or less than the above upper limit, induction of slab mode and occurrence of substrate resonance are suppressed, and a waveguide element with small propagation loss over a wide frequency range (ie, wideband) can be realized.

[0057] The resin material substrate 1 is made of a resin material. Any appropriate material can be used as the resin material as long as the effects of the embodiment of the present invention can be obtained. Representative examples of such materials include fluorine-based resins such as polytetrafluoroethylene (PTFE); hydrocarbon-based resins such as cycloolefin (COP) and cyclic olefin copolymer (COC); liquid crystal-based resins such as liquid crystal polymer (LCP); and polyimide-based resins such as modified polyimide.

[0058] The resistivity of the resin material substrate 1 is, for example, 10 7 kΩ·cm or more, preferably 10 8 kΩ·cm or more, and more preferably 10 9 kΩ·cm or more, and more preferably 10 10The resistivity is greater than or equal to kΩ·cm. If the resistivity is in this range, the electromagnetic waves can propagate through the material with low loss without affecting the electron conduction. Although the details of this phenomenon are not clear, it can be assumed that if the resistivity is low, the electromagnetic waves couple with the electrons and the energy of the electromagnetic waves is taken away by the electron conduction, resulting in loss. From this point of view, the higher the resistivity, the better. The resistivity is, for example, 10 16 It can be less than kΩ·cm.

[0059] The thermal expansion coefficient (linear expansion coefficient) of the resin material substrate 1 is not particularly limited. The upper limit of the thermal expansion coefficient (linear expansion coefficient) of the resin material substrate 1 is, for example, 80 ppm / K, and preferably 70 ppm / K. The lower limit of the thermal expansion coefficient (linear expansion coefficient) of the resin material substrate 1 is, for example, 10 ppm / K, and preferably 12 ppm / K. If the thermal expansion coefficient is within this range, thermal deformation (typically, warpage) of the substrate can be effectively suppressed. The thermal expansion coefficient can be measured in accordance with JIS standard R1618.

[0060] Such a resin material substrate 1 may be subjected to surface treatment such as surface roughening, if necessary.

[0061] C. Conductor layer In one embodiment, the conductor layer 2 is formed on the surface (one surface in the thickness direction) of the resin material substrate 1 and is in direct contact with the resin material substrate 1. The conductor layer 2 is typically made of a metal. Examples of metals include chromium (Cr), nickel (Ni), copper (Cu), gold (Au), silver (Ag), palladium (Pd), and titanium (Ti). The metals can be used alone or in combination. The conductor layer 2 may be a single layer, or may be formed by laminating two or more layers. The conductor layer 2 is formed on the resin material substrate 1 by a known film formation method (for example, plating, sputtering, vapor deposition, or printing). The thickness of the conductor layer 2 is, for example, 1 μm or more, preferably 4 μm or more, and for example, 20 μm or less, preferably 10 μm or less.

[0062] D. First and third ground electrodes In one embodiment, the first ground electrode 3 is formed by, for example, sputtering on the surface (preferably a roughened surface) of the resin material substrate 1 and / or the surface of the support substrate 7. The first ground electrode 3 can be made of the same metal as the conductor layer 2. The metal of the first ground electrode 3 may be the same as or different from the metal of the conductor layer 2. The thickness range of the first ground electrode 3 is the same as the thickness range of the conductor layer 2. Furthermore, when the first ground electrode 3 functions as a joint, metal layers may be formed on both the resin material substrate 1 and the support substrate 7, and these metal layers may be directly joined to form the first ground electrode 3. In this case, the joint interface is formed inside the first ground electrode.

[0063] As shown in FIG. 8 , in one embodiment, the third ground electrode 4 is formed by, for example, sputtering or plating on the surface of the support substrate 7 opposite the first ground electrode 3. The third ground electrode 4 can be made of the same metal as the conductor layer 2. The metal of the third ground electrode 4 may be the same as or different from the metal of the conductor layer 2. The thickness range of the third ground electrode 4 is the same as the thickness range of the conductor layer 2. The third ground electrode 4 does not necessarily have to be formed over the entire surface of the support substrate 7 opposite the first ground electrode.

[0064] E. Support board The support substrate 7 has an upper surface located within the composite substrate and a lower surface exposed to the outside. The support substrate 7 is provided to increase the strength of the composite substrate, thereby enabling the resin material substrate to be thinned. Any appropriate configuration can be adopted for the support substrate 7. Specific examples of materials that can be used for the support substrate 7 include indium phosphide (InP), silicon (Si), glass, sialon (Si3N4-Al2O3), mullite (3Al2O3·2SiO2, 2Al2O3·3SiO2), aluminum nitride (AlN), magnesium oxide (MgO), aluminum oxide (Al2O3), spinel (MgAl2O4), sapphire, quartz (single crystal quartz, amorphous quartz, etc.), quartz, gallium nitride (GaN), silicon carbide (SiC), silicon nitride (Si3N4), and gallium oxide (Ga2O3). The thermal conductivity of the support substrate 7 is, for example, 90 W / Km or more, preferably 150 W / Km or more, and typically 500 W / Km or less.

[0065] When mounting an active element such as an oscillator or receiver on a waveguide element, it is desirable to improve the heat dissipation performance of the waveguide element. Therefore, it may be desirable to use a material with high thermal conductivity for the support substrate. In this case, the thermal conductivity of the support substrate is preferably 150 W / Km or higher, and the material of the support substrate is preferably selected from silicon (Si), aluminum nitride (AlN), gallium nitride (GaN), silicon carbide (SiC), or silicon nitride (Si3N4).

[0066] Furthermore, when an SIW is formed on the support substrate 7, a material with a small dielectric loss tan δ is preferred to reduce the loss of the electromagnetic wave propagating through the SIW. In this case, the material of the support substrate is preferably selected from single crystal quartz, amorphous quartz, spinel, AlN, sapphire, aluminum oxide, SiC, magnesium oxide, or silicon. Among such materials for the support substrate, silicon is more preferable.

[0067] The thickness of the support substrate 7 is determined by setting the relative dielectric constant of the support substrate 7 to εb , where λ is the wavelength of the electromagnetic wave guided by the waveguide element, for example, λ / 4√ε b or more, preferably λ / 2√ε b or more, for example, 2λ / √ε b Below, preferably 3λ / 2√ε b More preferably, λ / √ε b If the thickness of the support substrate is equal to or greater than the above-mentioned lower limit, the mechanical strength of the waveguide element can be reliably improved. If the thickness of the support substrate is equal to or less than the above-mentioned upper limit, slab mode propagation can be suppressed, the waveguide element can be made thinner (maintaining the mechanical strength of the waveguide element), and substrate resonance can be suppressed. 23 and 24, when a plurality of support substrates 7 are arranged at intervals in the thickness direction of the resin material substrate 1, if the substrate is to be used as a phased array antenna, it is desirable that the interval between adjacent support substrates 7 be approximately λ / 2, which is appropriate for the antenna pitch. If the thickness of the support substrates 7 is less than this interval, an appropriate antenna pitch can be ensured by providing a spacer substrate 13 between the adjacent support substrates.

[0068] In coplanar waveguides, it is preferable for the material making up the support substrate to have a small dielectric dissipation factor. In the case of coplanar waveguides, if the thickness of the resin material substrate becomes small, the propagating electromagnetic waves may seep into the support substrate, so reducing the dielectric dissipation factor can reduce propagation loss. From this perspective, it is preferable for the dielectric dissipation factor to be 0.07 or less.

[0069] F. Joint As shown in FIGS. 3 and 4, the bonding portion may be a single layer, or may be a laminate of two or more layers. The bonding portion is typically made of an inorganic material. Examples of bonding portions include a SiO2 layer, an amorphous silicon layer, and a tantalum oxide layer. The bonding portion may be a metal film selected from gold (Au), titanium (Ti), platinum (Pt), chromium (Cr), copper (Cu), tin (Sn), or a combination (alloy) thereof. When the bonding portion is a metal film, adhesion with the metal ground electrode can be stably ensured, and migration can be suppressed. Among these bonding portions, an amorphous silicon layer is preferred. The thickness of the bonding portion is, for example, 0.001 μm or more and 10 μm or less, preferably 0.1 μm or more and 3 μm or less. [Example]

[0070] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0071] Example 1 1-1. Fabrication of waveguide element (coplanar waveguide) The waveguide element shown in Figure 3 was fabricated.

[0072] A 0.1 mm thick polyimide substrate (resin material substrate) was prepared, and the surface of the polyimide substrate was roughened. A gold film was then sputtered to form a ground electrode. An amorphous silicon film was then sputtered onto the ground electrode. After deposition, the amorphous silicon film was polished and flattened. Using an atomic force microscope, the arithmetic mean roughness of a 10 μm square area (a 10 μm square area; the same applies below) on the surface of the amorphous silicon film was measured and found to be 0.2 nm.

[0073] A silicon wafer (support substrate) with a thickness of 525 μm was also prepared. The arithmetic mean roughness of the surface of the silicon wafer, measured over a 10 μm square area using an atomic force microscope, was found to be 0.2 nm.

[0074] Then, the amorphous silicon surface formed on the ground electrode and the silicon wafer were bonded as follows: First, the polyimide substrate and the silicon wafer were placed in a vacuum chamber. -6 In a vacuum of the Pa range, both bonding surfaces (the amorphous silicon surface formed on the ground electrode and the surface of the silicon wafer) were irradiated with a high-speed Ar neutral atom beam (accelerating voltage 1 kV, Ar flow rate 60 sccm) for 70 seconds. After irradiation, the polyimide substrate and silicon wafer were allowed to cool for 10 minutes. Then, the amorphous silicon surface formed on the ground electrode and the bonding surfaces of the silicon wafer (the beam-irradiated surfaces of the polyimide substrate and silicon wafer) were brought into contact and pressed with 4.90 kN for 2 minutes to bond the polyimide substrate and silicon wafer. In other words, the polyimide substrate and silicon wafer were directly bonded via the amorphous silicon layer (bonding area). After bonding, the silicon wafer was polished to a thickness of 200 μm to form a composite wafer. No defects such as peeling were observed at the bonding interface in the resulting polyimide substrate / ground electrode / bonding area / silicon composite substrate.

[0075] Next, a resist was applied to the surface of the polyimide substrate opposite the silicon wafer (the polished surface), and the surface was patterned by photolithography to expose the area where the coplanar electrode pattern would be formed. The coplanar electrode pattern was then formed by sputtering on the upper surface of the polyimide substrate exposed from the resist. The length of the signal electrode in the waveguide direction was 10 mm. In this way, a waveguide element including a coplanar electrode, a resin material substrate, a ground electrode, and a support substrate was obtained.

[0076] 1-2. Calculating propagation loss Next, an RF signal generator was coupled to the input side of the director element by a probe, and an electromagnetic wave was coupled to an RF signal receiver by installing a probe on the output side of the director element. Next, a voltage was applied to the RF signal generator, causing it to transmit an electromagnetic wave with a frequency of 150 GHz. This caused the electromagnetic wave to propagate through the coplanar waveguide (waveguide element). The RF signal receiver measured the RF power of the electromagnetic wave output from the coplanar waveguide. From the measurement results, the propagation loss (dB / cm) was calculated, which was 1 dB / cm.

[0077] 1-3.Evaluation of heat dissipation performance A thermal conduction analysis was performed on the waveguide element of Example 1 using the finite element method (FEMTET, manufactured by Murata Software Corporation). In the thermal conduction analysis, the thermal conductivity of polyimide (resin material substrate) was set to 0.2 W / mK, the thermal conductivity of silicon (support substrate) to 150 W / mK, and the thermal conductivity of gold (ground electrode) to 300 W / mK. In Example 1, the resin material substrate and the support substrate were directly bonded via the ground electrode and the bonding portion, and since the bonding interface was amorphous, the thermal interface resistance of the interface was set to zero. As a result of this analysis, the thermal resistance of the waveguide element was 90 K / W. This confirmed the improvement in heat dissipation due to direct bonding.

[0078] <Example 2> A waveguide element was fabricated in the same manner as in Example 1, except that the ground electrode and the silicon wafer were directly bonded using solder (AuSn: thermal conductivity 50 W / mK) instead of the amorphous silicon layer. The thermal resistance of the obtained waveguide element was analyzed in the same manner as in the evaluation of the heat dissipation performance described above. As a result, the thermal resistance of the waveguide element was 90 K / W.

[0079] <Comparative Example 1> A waveguide element comprising a coplanar electrode, a polyimide substrate, a ground electrode, a polyimide adhesive layer, and a support substrate was obtained in the same manner as in Example 1, except that the polyimide substrate on which the ground electrode was formed and the silicon wafer were cured and bonded using a polyimide adhesive (organic adhesive) instead of direct bonding. The propagation loss of the obtained waveguide element was calculated in the same manner as in Example 1. As a result, the propagation loss was 1.0 dB / cm. The thermal resistance of the obtained waveguide element was analyzed in the same manner as in Example 1. As a result, the thermal resistance of the waveguide element was 150 K / W. [Industrial Applicability]

[0080] The waveguide element according to the embodiment of the present invention can be used in a wide range of fields, such as waveguides, next-generation high-speed communications, sensors, laser processing, and solar power generation, and is particularly suitable for use as a waveguide for millimeter waves to terahertz waves. Such a waveguide element can be used, for example, in an antenna, a bandpass filter, a coupler, a delay line (phase shifter), or an isolator. [Explanation of symbols]

[0081] 1 Resin material substrate 2 Conductor layer 21 signal electrode 22 2nd ground electrode 3 1st ground electrode 4 Third ground electrode 5. First via 6 Second via 7 Support substrate 8 Joint 9 Through-substrate vias 100 Waveguide element 101 Waveguide element 102 Waveguide element

Claims

1. A waveguide element capable of guiding electromagnetic waves having a frequency of 30 GHz or more and 20 THz or less, a resin material substrate; a conductor layer provided on the upper part of the resin material substrate; a support substrate located on the opposite side of the resin material substrate from the conductor layer, the resin material substrate and the support substrate are directly bonded to each other, the conductor layer includes a signal electrode that forms a transmission line capable of propagating the electromagnetic wave; The thickness t of the resin material substrate satisfies the following formula (1): [Equation 1] (wherein t represents the thickness of the resin material substrate; λ represents the wavelength of the electromagnetic wave guided by the waveguide element; ε represents the relative dielectric constant of the resin material substrate at 150 GHz; and a represents a value of 3 or more).

2. The waveguide element of claim 1 , further comprising a first ground electrode located between the resin material substrate and the support substrate.

3. The waveguide element according to claim 2 , wherein the first ground electrode is in direct contact with the resin material substrate and the support substrate, and functions as a joining portion that joins the resin material substrate and the support substrate.

4. the first ground electrode is in direct contact with the resin material substrate; The waveguide element according to claim 2 , further comprising a joint portion that joins the first ground electrode and the support substrate.

5. the first ground electrode is in direct contact with the support substrate; The waveguide element according to claim 2 , further comprising a joining portion joining the resin material substrate and the first ground electrode.

6. The waveguide element of claim 2 , wherein the conductor layer comprises a second ground electrode spaced apart from the signal electrode.

7. a third ground electrode located on the opposite side of the support substrate from the first ground electrode; a first via that electrically connects the second ground electrode and the third ground electrode and is also electrically connected to the first ground electrode; a second via that electrically connects the first ground electrode and the second ground electrode, a plurality of the first vias are provided; The waveguide element according to claim 6 , wherein the second via is disposed between adjacent first vias among the plurality of first vias.

8. a third ground electrode located on the opposite side of the support substrate from the first ground electrode; a plurality of through-substrate vias electrically connecting the first ground electrode and the third ground electrode; The waveguide element according to claim 6 , wherein the first ground electrode, the third ground electrode, and the plurality of through-substrate vias form a substrate integrated waveguide capable of propagating electromagnetic waves.

9. 2. The waveguide element according to claim 1, wherein in the formula (1), a represents a value of 6 or more.

10. A waveguide element capable of guiding electromagnetic waves having a frequency of 30 GHz or more and 20 THz or less, a resin material substrate; a conductor layer provided on the upper part of the resin material substrate; a support substrate located on the opposite side of the resin material substrate from the conductor layer, the resin material substrate and the support substrate are directly bonded to each other, the conductor layer includes a signal electrode that forms a transmission line capable of propagating the electromagnetic wave; A waveguide element, wherein the resin material substrate has a thickness t of 100 μm or less.

11. 2. The waveguide element according to claim 1, wherein the thickness t of the resin material substrate is 1 [mu]m or more.

12. A waveguide element capable of guiding electromagnetic waves having a frequency of 30 GHz or more and 20 THz or less, a resin material substrate; a conductor layer provided on the upper part of the resin material substrate; a support substrate located on the opposite side of the resin material substrate from the conductor layer; a bonding portion provided between the resin material substrate and the support substrate, the resin material substrate and the support substrate are directly bonded to each other, the conductor layer includes a signal electrode that forms a transmission line capable of propagating the electromagnetic wave; The bonding portion is made of SiO ２ The waveguide element is a silicon layer, an amorphous silicon layer, or a tantalum oxide layer.

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