CN117693863A

CN117693863A - Waveguide element and method for manufacturing waveguide element

Info

Publication number: CN117693863A
Application number: CN202280050793.0A
Authority: CN
Inventors: 谷健太郎; 冈田直刚; 近藤顺悟
Original assignee: NGK Insulators Ltd
Current assignee: NGK Insulators Ltd
Priority date: 2021-08-12
Filing date: 2022-08-04
Publication date: 2024-03-12

Abstract

The invention provides a waveguide element capable of sufficiently reducing propagation loss even when electromagnetic waves with a frequency higher than 30GHz are guided. The waveguide element according to an embodiment of the present invention includes: an inorganic material substrate; a conductor layer including a signal electrode and a first ground electrodeThe method comprises the steps of carrying out a first treatment on the surface of the A support substrate located on the opposite side of the conductor layer from the inorganic material substrate; a second ground electrode located between the inorganic material substrate and the support substrate; and a third ground electrode located on an opposite side of the second ground electrode with respect to the support substrate. The first ground electrode, the second ground electrode, and the third ground electrode are electrically connected. The thickness t of the inorganic material substrate satisfies the following formula (1).

Description

Waveguide element and method for manufacturing waveguide element

Technical Field

The present invention relates to a waveguide element and a method for manufacturing the waveguide element.

Background

As one of elements for guiding millimeter wave to terahertz wave, a waveguide element has been developed. The waveguide element is 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 an example of the waveguide element, a technique using a grounded coplanar waveguide configured to include: a glass substrate having a thickness of 300 μm; a coplanar conductor disposed on the glass substrate; and a ground electrode provided on a surface of the glass substrate opposite to the coplanar conductor (patent document 1).

In the case of using the waveguide device of the above-described technique for various industrial products, the case of mounting the waveguide device on a supporting substrate such as an IC substrate or a printed circuit board has been studied. However, there are the following problems: if the waveguide element is mounted on the support substrate to guide millimeter wave to terahertz wave (particularly electromagnetic wave of 300GHz or more), propagation loss increases significantly.

Prior art literature

Patent literature

Patent document 1: japanese patent application laid-open No. 2021-509767

Disclosure of Invention

The main purpose of the invention is that: provided are a waveguide element and a method for manufacturing the same, wherein propagation loss can be sufficiently reduced even when electromagnetic waves having a high frequency of 30GHz or higher are guided.

The waveguide element according to the embodiment of the present invention can guide electromagnetic waves having a frequency of 30GHz to 20 THz. The waveguide element is provided with: an inorganic material substrate; a conductor layer provided on an upper portion of the inorganic material substrate, the conductor layer including a signal electrode extending in a predetermined direction and a first ground electrode disposed at a distance from the signal wiring in a direction intersecting the predetermined direction; a support substrate located on the opposite side of the conductor layer from the inorganic material substrate; a second ground electrode located between the inorganic material substrate and the support substrate; and a third ground electrode located on an opposite side of the second ground electrode with respect to the support substrate. The first ground electrode, the second ground electrode, and the third ground electrode are electrically connected. The thickness t of the inorganic material substrate satisfies the following formula (1).

[ mathematics 1]

( Wherein t represents the thickness of the inorganic material substrate. Lambda denotes the wavelength of the electromagnetic wave guided by the waveguide element. Epsilon represents the relative dielectric constant of the inorganic material substrate at 300 GHz. a represents a number of 3 or more. )

The waveguide element according to item [1] above, further comprising a first via hole. The first via hole electrically connects the first ground electrode and the third ground electrode, and electrically connects the second ground electrode.

The waveguide element according to item [2] above, further comprising a first via borrowing hole. The first via hole is disposed in the first via hole. The first via hole penetrates through the inorganic material substrate, the second ground electrode, and the support substrate via holes.

The waveguide element according to item [3], wherein the first via Kong Jieyong hole has a circular shape when viewed from the surface (upper surface) of the inorganic material substrate, and has a tapered shape in which the inner diameter becomes smaller as the second ground electrode is approached.

The waveguide element according to item [3], wherein the first via Kong Jieyong hole has a circular shape when viewed from the surface (upper surface) of the inorganic material substrate, and has a tapered shape in which the diameter becomes larger as the hole approaches the second ground electrode.

The waveguide element according to any one of [2] to [5] above, further comprising a second via hole. The second via hole electrically connects the first ground electrode and the second ground electrode. The waveguide element may include a plurality of the first via holes. The second via hole is disposed between adjacent ones of the plurality of first via holes.

The waveguide element according to item [6] above, further comprising a second via-borrowing hole. The second via hole is disposed by using the hole. The second via hole penetrates through the inorganic material substrate by means of a hole and does not penetrate through the supporting substrate.

The waveguide element according to item [1] above, further comprising a second via hole and a third via hole. The second via hole electrically connects the first ground electrode and the second ground electrode. A third via electrically connects the second ground electrode and the third ground electrode.

The waveguide element according to any one of [1] to [8], wherein a in the above formula (1) may represent a value of 6 or more.

The waveguide element according to any one of [1] to [9], wherein a relative dielectric constant ε at 300GHz of the inorganic material substrate is 3.5 or more and 12.0 or less, and a dielectric tangent (dielectric loss) tan δ at 300GHz of the inorganic material substrate is 0.003 or less.

The waveguide element according to item [10], wherein the inorganic material substrate is a quartz glass substrate.

The waveguide element according to any one of [1] to [11], wherein the conductor layer is a coplanar electrode.

The waveguide element according to any one of [1] to [11], wherein the conductor layer and the second ground electrode are microstrip electrodes.

The waveguide element according to [12] or [13], wherein the thickness of the inorganic material substrate is 10 μm or more when the frequency of the electromagnetic wave propagating through the waveguide element is 30GHz or more and 5THz or less.

A method of manufacturing a waveguide element according to another aspect of the present invention is a method of manufacturing the waveguide element according to any one of [2] to [5] above, comprising the steps of: preparing a laminate having the inorganic material substrate, the second ground electrode, and the support substrate in this order, wherein the laminate has first through Kong Jieyong holes penetrating through the inorganic material substrate, the second ground electrode, and the support substrate; the first via hole is formed in the first via Kong Jieyong hole, the third ground electrode is formed in the lower portion of the support substrate, and the conductor layer is formed in the upper portion of the inorganic material substrate.

The method for manufacturing a waveguide element according to another aspect of the present invention is a method for manufacturing a waveguide element according to [6] above, comprising the steps of: preparing a laminate including the inorganic material substrate, the second ground electrode, and the support substrate in this order, wherein the laminate includes a first via borrowed hole penetrating through the inorganic material substrate, the second ground electrode, and the support substrate, and a second via Kong Jieyong hole penetrating through the inorganic material substrate but not through the support substrate (penetrating only the inorganic material substrate); the first via hole is formed in the first via Kong Jieyong hole, the second via hole is formed in the second via Kong Jieyong hole, the third ground electrode is formed in the lower portion of the support substrate, and the conductor layer is formed in the upper portion of the inorganic material substrate.

The waveguide element according to another embodiment of the present invention can guide electromagnetic waves having a frequency of 30GHz to 20 THz. The waveguide element is provided with: an inorganic material substrate; a conductor layer provided on an upper portion of the inorganic material substrate, the conductor layer including a signal electrode extending in a predetermined direction and a first ground electrode disposed at a distance from the signal wiring in a direction intersecting the predetermined direction; a support substrate located on the opposite side of the conductor layer from the inorganic material substrate; a second ground electrode located between the inorganic material substrate and the support substrate; a third ground electrode located on an opposite side of the second ground electrode with respect to the support substrate; and a via hole electrically connecting the first ground electrode and the third ground electrode and electrically connecting the second ground electrode. The thickness t of the inorganic material substrate satisfies the above formula (1).

The waveguide element according to still another embodiment of the present invention can guide electromagnetic waves having a frequency of 30GHz to 20 THz. The waveguide element is provided with: an inorganic material substrate; a conductor layer provided on an upper portion of the inorganic material substrate, the conductor layer including a signal electrode extending in a predetermined direction and a first ground electrode disposed at a distance from the signal wiring in a direction intersecting the predetermined direction; a support substrate located on the opposite side of the conductor layer from the inorganic material substrate; a second ground electrode located between the inorganic material substrate and the support substrate; a third ground electrode located on an opposite side of the second ground electrode with respect to the support substrate; a first via electrically connecting the first ground electrode and the third ground electrode, and electrically connecting the second ground electrode; and a second via hole electrically connecting the first ground electrode and the second ground electrode. The waveguide element includes a plurality of the first via holes, and the second via holes are arranged between adjacent ones of the plurality of first via holes. The thickness t of the inorganic material substrate satisfies the above formula (1).

Effects of the invention

According to an embodiment of the present invention, it is possible to realize: a waveguide element capable of sufficiently reducing propagation loss even when electromagnetic waves having a high frequency of 30GHz or higher are guided. In addition, according to the embodiment of another aspect of the present invention, the waveguide element described above can be manufactured smoothly.

Drawings

Fig. 1 is a schematic perspective view of a waveguide element according to an embodiment of the present invention.

Fig. 2 is a sectional view of the waveguide element of fig. 1 in section II-II'.

Fig. 3 is a cross-sectional view of a waveguide element according to another embodiment of the present invention, II-II'.

Fig. 4 is an IV-IV' cross-sectional view of a waveguide element of another embodiment of the present invention.

Fig. 5 is a sectional view of a waveguide element according to still another embodiment of the present invention in section II-II'.

Fig. 6 is a sectional view of a waveguide element according to still another embodiment of the present invention in section II-II'.

Fig. 7 is a schematic perspective view of a waveguide element according to still another embodiment of the present invention.

Fig. 8 is a cross-sectional view of the waveguide element VIII-VIII' of fig. 7.

Fig. 9 is a cross-sectional view of the waveguide element IX-IX' of fig. 7.

Fig. 10 is an X-X' cross-sectional view of the waveguide element of fig. 7.

Fig. 11 is an X-X' cross-sectional view of a waveguide element of yet another embodiment of the present invention.

Fig. 12 is an X-X' cross-sectional view of a waveguide element of yet another embodiment of the present invention.

Fig. 13 is a VIII-VIII' cross-sectional view of a waveguide component according to yet another embodiment of the invention.

Fig. 14 is an X-X' cross-sectional view of a waveguide element of yet another embodiment of the present invention.

Detailed Description

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

A. Integral construction of waveguide elements

A-1. Integral construction of waveguide element 100

Fig. 1 is a schematic perspective view of a waveguide element according to 1 embodiment of the present invention; fig. 2 is a sectional view of the waveguide element of fig. 1 in section II-II'.

The waveguide element 100 illustrated in the drawing can guide electromagnetic waves having a frequency of 30GHz or more and 20THz or less, in other words, electromagnetic waves of millimeter waves to terahertz waves. The millimeter wave is typically an electromagnetic wave having a frequency of about 30GHz to 300 GHz; terahertz waves are typically electromagnetic waves having a frequency of about 300GHz to 20 THz. In particular, the waveguide element 100 can guide electromagnetic waves having a frequency of 30GHz to 2THz (particularly electromagnetic waves having a frequency of 30GHz to 1 THz) with excellent propagation loss.

The waveguide element 100 includes: an inorganic material substrate 1; a conductor layer 2 including a signal electrode 2a and first ground electrodes 2b, 2c; a support substrate 7; a second ground electrode 3; a third ground electrode 4; and a first via hole 5.

The conductor layer 2 is provided on the upper portion (more specifically, the upper surface) of the inorganic material substrate 1. The signal electrode 2a extends in a predetermined direction (waveguide direction). The first ground electrodes 2b and 2c are arranged at intervals from the signal electrode 2a in a direction intersecting the predetermined direction in which the signal electrode 2a extends. The support substrate 7 is located on the opposite side of the conductor layer 2 from the inorganic material substrate 1. The second ground electrode 3 is located between the inorganic material substrate 1 and the support substrate 7. The third ground electrode 4 is located on the opposite side of the second ground electrode 3 with respect to the support substrate 7. The first via hole 5 electrically connects the first ground electrode 2b, 2c and the third ground electrode 4, and electrically connects the second ground electrode 3. Thereby, the first ground electrodes 2b, 2c, the second ground electrode 3, and the third ground electrode 4 are electrically connected. The thickness t of the inorganic material substrate 1 satisfies the following formula (1).

[ mathematics 1]

In the waveguide element including the conductor layer including the signal electrode, the electromagnetic wave of high frequency inputted to the waveguide element propagates through the inorganic material substrate.

According to the above configuration, if the thickness of the inorganic material substrate satisfies the above formula (1), even when the waveguide guides the electromagnetic wave with a high frequency, the induction of the slab mode and/or the occurrence of the substrate resonance can be suppressed. However, when the thickness of the inorganic material substrate satisfies the above formula (1), a new problem may occur: the propagating electromagnetic wave leaks from the inorganic material substrate to the support substrate, and propagation loss due to dielectric loss of the support substrate increases.

In contrast, according to the above configuration, the second ground electrode is disposed between the inorganic material substrate and the support substrate, and the third ground electrode is disposed on the opposite side of the second ground electrode with respect to the support substrate, so that leakage of electromagnetic waves to the support substrate can be suppressed. Therefore, induction of the flat mode and/or occurrence of substrate resonance can be suppressed, and leakage of electromagnetic waves to the supporting substrate can be suppressed.

Further, the first via hole electrically connects the first ground electrode, the second ground electrode, and the third ground electrode, and therefore, the ground can be enhanced, and the floating capacity due to surrounding wires and elements can be suppressed. In addition, a heat dissipation function can be added to the substrate. Further, transmission in the advanced mode can be suppressed.

Further, according to the above configuration, the first via hole electrically connects the first ground electrode, the second ground electrode, and the third ground electrode, and therefore, the relative positional accuracy of the portion located between the first ground electrode and the second ground electrode and the portion located between the second ground electrode and the third ground electrode can be ensured easily in the first via hole. Therefore, compared with the case where the via hole connecting the first ground electrode and the second ground electrode and the via hole connecting the second ground electrode and the third ground electrode are provided separately (refer to fig. 14), the occurrence of the fluctuation can be suppressed.

The above results: in the waveguide element, even when electromagnetic waves having a high frequency of 30GHz or more are guided, propagation loss can be sufficiently reduced.

In addition, miniaturization of the waveguide element is being developed, and integration of the circuit is expected. In the waveguide element, since the inorganic material substrate is thinned, excellent propagation loss performance can be ensured, and the desire for downsizing can be satisfied.

In 1 embodiment, in the above formula (1), a represents a number of 6 or more.

If the thickness of the inorganic material substrate satisfies the formula (1) in which a represents a value of 6 or more, the propagation loss can be reduced when the electromagnetic wave having the high frequency is guided.

The dielectric constant of the inorganic material substrate 1 at 100GHz to 10THz is, for example, 10.0 or less, preferably 3.7 or more and 10.0 or less, and more preferably 3.8 or more and 9.0 or less. When the frequency used is 300GHz, the relative dielectric constant epsilon of the inorganic material substrate 1 is typically 3.5 or more, typically 12.0 or less, preferably 10.0 or less, and more preferably 5.0 or less. If the dielectric constant of the inorganic material substrate is in such a range, the propagation delay of electromagnetic waves can be suppressed.

The dielectric loss tangent (tan δ) of the inorganic material substrate is preferably 0.01 or less, more preferably 0.008 or less, further preferably 0.006 or less, particularly preferably 0.004 or less at the frequency of use. When the frequency to be used is 300GHz, the dielectric loss tangent tan δ of the inorganic material substrate 1 is preferably 0.0030 or less, more preferably 0.0020 or less, and further preferably 0.0015 or less.

If the dielectric loss tangent is in the above range, propagation loss in the waveguide can be reduced. The smaller the dielectric loss tangent, the more desirable. The dielectric loss tangent may be, for example, 0.001 or more.

When the relative permittivity epsilon and the dielectric loss tangent (dielectric loss) tan delta of the inorganic material substrate are in the above-described ranges, it is possible to more stably achieve a reduction in propagation loss when guiding the electromagnetic wave of the high frequency (particularly, electromagnetic wave of 300GHz or more). The relative dielectric constant epsilon and the dielectric loss tangent (dielectric loss) tan delta can be measured by terahertz time-domain spectroscopy. In the present specification, the term "relative permittivity and dielectric loss tangent" refers to the relative permittivity and dielectric loss tangent at 300GHz unless a measurement frequency is mentioned.

The thickness of the inorganic 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, still more preferably 20 μm or more, for example 1700 μm or less, preferably 500 μm or less, more preferably 200 μm or less, still more preferably 100 μm or less. In the case where the frequency of the electromagnetic wave propagating through the waveguide element is 30GHz or more and 5THz or less, the thickness of the inorganic material substrate 1 is preferably 10 μm or more.

If the thickness of the inorganic material substrate 1 is less than the lower limit, the thickness and width of the electrode constituting the waveguide element are as low as several μm or so, and the propagation loss is increased due to the influence of the skin effect, and the allowable error in the line performance due to the manufacturing variation is significantly reduced.

If the thickness of the inorganic material substrate 1 is equal to or less than the upper limit, the induction of the flat mode or the occurrence of substrate resonance is suppressed, and it is possible to realize: a waveguide element whose propagation loss is small in a wide frequency range (i.e., wide frequency band).

In 1 embodiment, the waveguide elements constitute coplanar lines. That is, the conductor layer of the waveguide element is a coplanar electrode.

In 1 embodiment, the conductor layer 2 is a coplanar electrode. As shown in fig. 2, when the conductor layer 2 is a coplanar electrode, the electromagnetic wave having the high frequency is propagated through the inorganic material substrate 1 by being combined with an electric field generated between the signal electrode 2a and the first ground electrodes 2b and 2 c.

In the case where the conductor layer 2 is a coplanar electrode, the signal electrode 2a has a line shape extending in a predetermined direction (waveguide direction). The first ground electrode 2b is configured to: a predetermined gap (clearance) is formed between the signal electrode 2a in a direction intersecting (preferably orthogonal to) the longitudinal direction of the signal electrode 2 a. The first ground electrode 2c is configured to: in a direction intersecting (preferably orthogonal to) the longitudinal direction of the signal electrode 2a, a predetermined gap (clearance) is formed between the signal electrode 2a and the first ground electrode 2b on the opposite side of the signal electrode 2 a. The void (gap) extends in the longitudinal direction of the signal electrode 2 a.

The width (dimension in the direction perpendicular to the longitudinal direction) w of the signal electrode 2a of the coplanar electrode is, for example, 2 μm or more, preferably 20 μm or more, for example, 200 μm or less, preferably 150 μm or less.

The width (dimension in the direction perpendicular to the longitudinal direction) g of the void (gap) is, for example, 2 μm or more, preferably 5 μm or more, for example, 100 μm or less, preferably 80 μm or less.

In 1 embodiment, the waveguide element constitutes a microstrip line. That is, the conductor layer and the second ground electrode of the waveguide element are microstrip-type electrodes.

In 1 embodiment, the conductor layer 2 and the second ground electrode 3 are microstrip-type electrodes. In the case of the microstrip electrode shown in fig. 6, the electromagnetic wave having the high frequency is coupled with an electric field generated between the signal electrode 2a and the second ground electrode 3, and propagates through the inorganic material substrate 1.

In the case where the conductor layer 2 is a microstrip electrode, the signal electrode 2a has a flat strip shape extending in a predetermined direction (waveguide direction). The second ground electrode 3 is configured to: a predetermined gap (thickness of the inorganic material substrate) is formed between the signal electrode 2a in a direction intersecting (preferably orthogonal to) the longitudinal direction of the signal electrode 2 a. The gap extends in the longitudinal direction of the signal electrode 2 a. On the other hand, the first ground electrodes 2b, 2c may be provided similarly to the coplanar electrode, and the first ground electrodes 2b, 2c may be separated from the signal electrode 2a by a width larger than the width g of the gap portion (gap) of the coplanar electrode in a direction intersecting (preferably orthogonal to) the longitudinal direction of the signal electrode 2 a.

The width (dimension in the direction perpendicular to the longitudinal direction) w of the signal electrode 2a of the microstrip-type electrode is, for example, 2 μm or more, preferably 100 μm or more, more preferably 300 μm or more, for example, 800 μm or less, preferably 500 μm or less.

In the example of the figure, when the conductor layer 2 is a coplanar electrode or a microstrip electrode, the signal electrode 2a extends over the entire waveguide element 100, but the dimension of the signal electrode 2a in the longitudinal direction may be any appropriate dimension as long as it is not more than the dimension of the waveguide element in the waveguide direction. In addition, a plurality of signal electrodes may be provided in the waveguide element so as to be aligned in the waveguide direction.

A-2. Integral construction of waveguide element 101

Fig. 7 is a schematic perspective view of a waveguide element according to 1 embodiment of the present invention; FIG. 8 is a cross-sectional view of the waveguide element VIII-VIII' of FIG. 7; FIG. 9 is a cross-sectional view IX-IX' of the waveguide element of FIG. 7; fig. 10 is an X-X' cross-sectional view of the waveguide element of fig. 7.

The waveguide element 101 illustrated in the drawing can guide electromagnetic waves having a frequency of 30GHz or more and 20THz or less, in other words, electromagnetic waves of millimeter waves to terahertz waves described above. In particular, the waveguide element 101 can guide electromagnetic waves having a frequency of 30GHz to 2THz (particularly electromagnetic waves having a frequency of 30GHz to 1 THz) with excellent propagation loss.

The waveguide element 101 includes: an inorganic material substrate 1; a conductor layer 2 including a signal electrode 2a and first ground electrodes 2b, 2c; a support substrate 7; a second ground electrode 3; a third ground electrode 4; a first via hole 5; and a second via 6. That is, the waveguide element 101 has the same configuration as the waveguide element 100 except that the second via hole 6 is further provided.

The conductor layer 2 is provided on the upper portion (more specifically, the upper surface) of the inorganic material substrate 1. The signal electrode 2a extends in a predetermined direction (waveguide direction). The first ground electrodes 2b and 2c are arranged at intervals from the signal electrode 2a in a direction intersecting the predetermined direction in which the signal electrode 2a extends. The support substrate 7 is located on the opposite side of the conductor layer 2 from the inorganic material substrate 1. The second ground electrode 3 is located between the inorganic material substrate 1 and the support substrate 7. The third ground electrode 4 is located on the opposite side of the second ground electrode 3 with respect to the support substrate 7. The first via hole 5 electrically connects the first ground electrode 2b, 2c and the third ground electrode 4, and electrically connects the second ground electrode 3. The waveguide element 101 includes a plurality of the first via holes 5. The second via hole 6 electrically connects the first ground electrodes 2b, 2c and the third ground electrode 3. Thereby, the first ground electrodes 2b, 2c, the second ground electrode 3, and the third ground electrode 4 are electrically connected. The second via holes 6 are arranged between adjacent ones of the plurality of first via holes 5. The thickness t of the inorganic material substrate 1 satisfies the above formula (1).

According to the above configuration, since the second via holes are arranged between the first via holes adjacent to each other, the pitch of the first via holes and the second via holes in the inorganic material substrate can be made smaller than the pitch of the first via holes in the support substrate. Therefore, even if the inorganic material substrate is thinned as described above, the strength of the inorganic material substrate can be sufficiently ensured.

As shown in fig. 14, the waveguide element 101 may be provided with a third via hole 10 instead of the first via hole 5. In other words, the waveguide element 101 includes: an inorganic material substrate 1; a conductor layer 2 having a signal electrode 2a and first ground electrodes 2b, 2c; a support substrate 7; a second ground electrode 3; a third ground electrode 4; a second via hole 6; and a third via 10. The third via hole 10 electrically connects the second ground electrode 3 and the third ground electrode 4.

According to this configuration, the second via hole connects the first ground electrode and the second ground electrode, and the third via hole connects the second ground electrode and the third ground electrode, so that the first ground electrode, the second ground electrode, and the third ground electrode can be electrically connected. Accordingly, the ground can be strengthened, and the floating capacity due to surrounding wires and elements can be suppressed.

The term "waveguide element" in this specification includes: a wafer (waveguide wafer) having at least 1 waveguide element formed therein, and a chip obtained by cutting the waveguide element wafer.

In the following, the specific configuration of each component of the waveguide element will be described in the items B to I. In item J, a method of manufacturing a waveguide element is described.

B. Inorganic material substrate

The inorganic material substrate 1 has: an upper surface of the conductor layer 2 and a lower surface located in the composite substrate are provided.

The inorganic material substrate 1 is made of an inorganic material. As the inorganic material, any appropriate material may be used as long as the effects of the embodiments of the present invention are obtained. As such a material, typically, there may be mentioned: single crystal quartz (relative permittivity 4.5, dielectric loss tangent 0.0013), amorphous quartz (quartz glass, relative permittivity 3.8, dielectric loss tangent 0.0010), spinel (relative permittivity 8.3, dielectric loss tangent 0.0020), alN (relative permittivity 8.5, dielectric loss tangent 0.0015), sapphire (relative permittivity 9.4, dielectric loss tangent 0.0030), siC (relative permittivity 9.8, dielectric loss tangent 0.0022), magnesia (relative permittivity 10.0, dielectric loss tangent 0.0012) and silicon (relative permittivity 11.7, dielectric loss tangent 0.0016) (-) the relative permittivity and dielectric loss tangent within the range of (). The values at frequency 300GHz are represented. The inorganic material substrate 1 is preferably a quartz glass substrate made of amorphous quartz.

If the inorganic material substrate is a quartz glass substrate, propagation loss increase can be suppressed more stably even when the electromagnetic wave with high frequency is guided. Further, since the dielectric constant is larger than that of a resin-based substrate, the substrate size can be reduced, and since the dielectric constant is relatively small among inorganic materials, the substrate is advantageous in terms of reduction in retardation.

The resistivity of the inorganic material substrate 1 is, for example, 100kΩ·cm or more, preferably 300kΩ·cm or more, more preferably 500kΩ·cm or more, and even more preferably 700kΩ·cm or more. If the specific resistance is in such a range, electromagnetic waves do not affect electron conduction, and can propagate in the material with low loss. The details of this phenomenon are not clear, however, it is presumed that: if the resistivity is small, the electromagnetic wave combines with electrons, and the energy of the electromagnetic wave is extracted by the electron conduction and lost. From this point of view, the higher the resistivity, the more desirable. The resistivity may be, for example, 3000kΩ (3 mΩ). Cm or less.

The flexural strength of the inorganic material substrate 1 is, for example, 50MPa or more, preferably 60MPa or more. If the bending strength is in such a range, the substrate is less likely to deform, and therefore, a waveguide element having stable hole diameters and hole periods and small characteristic variations can be realized. The greater the bending strength, the more desirable. The bending strength may be, for example, 700MPa or less. The bending strength can be measured according to JIS standard R1601.

The thermal expansion coefficient (linear expansion coefficient) of the inorganic material substrate 1 is, for example, 10×10 ^－6 Preferably 8X 10, and K is less than or equal to ^－6 and/K or below. If the thermal expansion coefficient is in such a range, thermal deformation (typically warpage) of the substrate can be favorably suppressed. The coefficient of thermal expansion can be measured according to JIS standard R1618.

As described above, the smaller the dielectric loss tangent tan δ of the inorganic material substrate 1 is, the more preferable. As a method for reducing the dielectric loss tangent (tan δ) of the inorganic material substrate 1 in the 300GHz band, there is a method for reducing the concentration of OH groups contained in the inorganic material substrate. When the waveguide member guides electromagnetic waves having a frequency of 250GHz to 350GHz, the OH group concentration in the inorganic material substrate is, for example, 100wtppm or less, preferably 15wtppm or less, and more preferably 10wtppm or less. The OH group concentration in the inorganic material substrate may be typically 0wtppm or more. The OH group concentration can be measured by FTIR (fourier transform infrared spectroscopy), raman scattering spectroscopy, kalfield method.

In addition, the dielectric loss of the inorganic material substrate 1 can be evaluated by FQ value. The FQ value is calculated by the product of the reciprocal of the dielectric loss tangent (tan δ) and the frequency of the electromagnetic wave guided by the waveguide element.

When the OH group concentration of the inorganic material substrate 1 is 100wtppm or less, the FQ value is preferably 45000GHz or more if the frequency of the electromagnetic wave is 150GHz or more and less than 250 GHz; if the frequency of the electromagnetic wave is 250GHz or more and less than 350GHz, the FQ value is preferably 75000GHz or more.

In the case where the OH group concentration of the inorganic material substrate 1 is 15wtppm or less, if the frequency of the electromagnetic wave is 150GHz or more and less than 250GHz, the FQ value is preferably 75000GHz or more; if the frequency of the electromagnetic wave is 250GHz or more and less than 350GHz, the FQ value is preferably 105000GHz or more.

In the case where the OH group concentration of the inorganic material substrate 1 is 10wtppm or less, if the frequency of the electromagnetic wave is 150GHz or more and less than 250GHz, the FQ value is preferably 150000GHz or more, typically 270000GHz or less; if the frequency of the electromagnetic wave is 250GHz or more and less than 350GHz, the FQ value is preferably 250000GHz or more, typically 390000GHz or less.

The porosity of the inorganic material substrate 1 is, for example, 0.5ppm to 3000ppm, preferably 0.5ppm to 1000ppm, more preferably 0.5ppm to 100ppm, of pores having a pore size of 1 μm or more. If the porosity is in such a range, densification is enabled, and further, from the viewpoint of any one of mechanical strength and long-term reliability, a stable waveguide element can be realized by a synergistic effect with the effect of making the cavity size in the above-described predetermined range. Further, since the particle size can be reduced, the via hole described later can be uniformly formed by the shape of the hole. If the porosity exceeds 3000ppm, propagation loss in the waveguide may be increased. It is difficult to make the porosity less than 0.5ppm in the technique using an inorganic material substrate.

The size of the air hole is a diameter when the air hole is substantially spherical, a diameter when the air hole is substantially cylindrical, and a diameter of a circle inscribed in the air hole when the air hole is of another shape. The presence or absence of the air holes can be confirmed by, for example, light CT (Computed Tomograohy) or a transmittance measuring device. The size of the pores may be determined, for example, using a Scanning Electron Microscope (SEM).

C. Conductor layer

The conductor layer 2 is located on the opposite side of the second ground electrode 3 from the inorganic material substrate 1, and is provided on the surface of the inorganic material substrate 1. Typically, the conductor layer 2 is in direct contact with the inorganic material substrate 1.

Typically, the conductor layer 2 is composed of metal. Examples of the metal include: chromium (Cr), nickel (Ni), copper (Cu), gold (Au), silver (Ag), palladium (Pd), titanium (Ti). The metals may be used singly or in combination. The conductor layer 2 may be a single layer or may be formed by stacking 2 or more layers. The conductor layer 2 is formed on the inorganic material substrate 1 by plating, sputtering, vapor deposition, printing, for example.

The thickness of the conductor layer 2 is, for example, 1 μm or more, preferably 4 μm or more, for example, 20 μm or less, preferably 10 μm or less.

D. Second ground electrode

In 1 embodiment, the second ground electrode 3 is provided at: the surface of the inorganic material substrate 1 opposite to the conductor layer 2. The second ground electrode 3 is disposed with a gap from the signal electrode 2a in the thickness direction of the inorganic material substrate 1. Typically, the second ground electrode 3 is in direct contact with the inorganic material substrate 1. The second ground electrode 3 may be composed of the same metal as the conductor layer 2. From the standpoint of joining the inorganic material substrate 1 and the support substrate 7, the second ground electrode 3 needs to ensure adhesion strength that is easy to planarize the joint surface, and the metal of the second ground electrode 3 may be different from the metal of the conductor layer 2. The thickness range of the second ground electrode 3 is the same as that of the conductor layer 2.

Typically, the second ground electrode 3 is formed on the inorganic material substrate 1 by sputtering and plating.

E. Support substrate

The support substrate 7 can impart excellent mechanical strength to the waveguide element. Accordingly, the thickness t of the inorganic material substrate can be made thin so as to satisfy the above formula (1). Any suitable configuration may be used for the support substrate 7. Specific examples of the material constituting the support substrate 7 include: indium phosphide (InP), silicon (Si), glass, sialon (Si) ₃ N ₄ －Al ₂ O ₃ ) Mullite (3 Al) ₂ O ₃ ·2SiO ₂ ，2Al ₂ O ₃ ·3SiO ₂ ) Aluminum nitride (AlN), magnesium oxide (MgO), aluminum oxide (Al) ₂ O ₃ ) Spinel (MgAl) ₂ O ₄ ) Sapphire, quartz, crystal, gallium nitride (GaN), silicon carbide (SiC), silicon nitride (Si) ₃ N ₄ ) Gallium oxide (Ga) ₂ O ₃ )。

The support substrate 7 is preferably composed of at least 1 selected from indium phosphide, silicon, aluminum nitride, silicon carbide and silicon nitride, and more preferably composed of silicon.

When an active element such as an oscillator or a receiver is mounted on a waveguide element, there is a possibility that the inorganic material substrate is heated and the characteristics of other active elements or mounted components deteriorate. In order to prevent this, a material having high thermal conductivity may be used for the support substrate. In this case, the thermal conductivity is preferably 150W/Km or more, and examples of the material constituting the support substrate 7 in this viewpoint include: silicon (Si), aluminum nitride (AlN), gallium nitride (GaN), silicon carbide (SiC), silicon nitride (Si) ₃ N ₄ )。

The closer the linear expansion coefficient of the material constituting the support substrate 7 is to the linear expansion coefficient of the material constituting the inorganic material substrate 1, the more desirable. With such a configuration, thermal deformation (typically warpage) of the composite substrate can be suppressed. The linear expansion coefficient of the material constituting the support substrate 7 is preferably in the range of 50% to 150% relative to the linear expansion coefficient of the material constituting the inorganic material substrate 1.

In addition, the smaller the dielectric loss tangent of the material constituting the support substrate 7, the more desirable. In the case of the coplanar line, if the thickness of the waveguide element is reduced, the propagating electromagnetic wave may ooze out to the supporting substrate, and the dielectric loss tangent may be reduced, whereby the propagation loss may be suppressed. From this viewpoint, the dielectric loss tangent of the support substrate 7 is preferably 0.07 or less.

The thickness of the support substrate 7 is, for example, 50 μm or more, preferably 100 μm or more, more preferably 150 μm or more, for example, 3000 μm or less, preferably 2000 μm or less, more preferably 300 μm or less. In addition, in 1 embodiment, the thickness of the support substrate 7 is larger than that of the inorganic material substrate. More specifically, the thickness of the support substrate 7 is, for example, 1.1 times or more, preferably 1.5 times or more, for example, 30 times or less, preferably 10 times or less, and more preferably 5 times or less, relative to the thickness of the inorganic material substrate. If the thickness of the support substrate is not less than the lower limit, the mechanical strength of the waveguide element can be stably improved. If the thickness of the support substrate is equal to or less than the upper limit, it is possible to achieve: suppression of propagation of a flat mode, thinning of a waveguide element (maintenance of mechanical strength of the waveguide element), and suppression of substrate resonance.

The support substrate 7 supports the conductor layer 2, the inorganic material substrate 1, and the second ground electrode 3. More specifically, the support substrate 7 may be directly bonded to the inorganic material substrate 1 only by the second ground electrode 3, or may be directly bonded to the inorganic material substrate 1 by the second ground electrode 3 and a bonding portion (not shown).

In this specification, "directly joined" means: the 2 layers or substrates are bonded without an adhesive (typically, an organic adhesive). The form of direct bonding may be appropriately set according to the constitution of the layers or substrates to be bonded to each other.

By integrating these components by direct bonding, peeling in the waveguide element can be favorably suppressed, and as a result, damage (e.g., cracking) of the inorganic material substrate caused by such peeling can be favorably suppressed. In the following item J, details of direct bonding will be described.

When the support substrate 7 is bonded to the inorganic material substrate 1 only via the second ground electrode 3, the second ground electrode 3 functions as a bonding portion for bonding the inorganic material substrate 1 and the support substrate 7, and the support substrate 7 is in direct contact with the second ground electrode 3.

When the support substrate 7 is bonded to the inorganic material substrate 1 via the second ground electrode 3 and the bonding portion, the bonding portion is provided between the second ground electrode 3 and the support substrate 7. The joint may be 1 layer or may be laminated with 2 or more layers. As a means ofThe joint may include, for example: siO (SiO) ₂ Layer, amorphous silicon layer, tantalum oxide layer. In addition, from the viewpoint of securing adhesion strength and preventing migration, the metal film of Ti, cr, ni, pt, pd may be formed as an intermediate layer between the inorganic material substrate and the second ground electrode or between the support substrate and the second ground electrode. The thickness of the joint is, for example, 0.01 μm or more and 3 μm or less.

F. Third ground electrode

In 1 embodiment, the third ground electrode 4 is provided at: the surface of the support substrate 7 on the opposite side from the second ground electrode 3. The third ground electrode 4 is disposed at an interval from the second ground electrode 3 in the thickness direction of the inorganic material substrate 1. Typically, the third ground electrode 4 is in direct contact with the support substrate 7. The third ground electrode 4 is made of the same metal as the conductor layer 2, and 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 is formed on the support substrate 7 by, for example, sputtering or plating. The third ground electrode 4 may not necessarily be formed on the entire surface of the support substrate 7 on the opposite side from the second ground electrode.

G. First via hole

As shown in fig. 1, in the waveguide element 100, the first via holes 5 are provided on both sides of the signal electrode 2a in a direction intersecting (preferably orthogonal to) the longitudinal direction of the signal electrode 2 a. Hereinafter, the first via hole for electrically connecting the first ground electrode 2b and the third ground electrode 4 may be referred to as a first via hole 5a, and the first via hole for electrically connecting the first ground electrode 2c and the third ground electrode 4 may be referred to as a first via hole 5 b.

As shown in fig. 2, the first via hole 5a is in contact with the first ground electrode 2b and the third ground electrode 4, and extends continuously between the first ground electrode 2b and the third ground electrode 4. The first via hole 5b is in contact with the first ground electrode 2c and the third ground electrode 4, and extends continuously between the first ground electrode 2c and the third ground electrode 4. The first via holes 5a, 5b penetrate the second ground electrode 3, respectively, and are in contact with the second ground electrode 3. The waveguide element may be provided with only one of the first via holes 5a and 5 b.

Typically, the first via hole 5 is a conductive film. The first via hole 5 is made of a conductive material, typically the same metal as the conductive layer 2. The shape of the first via hole 5 corresponds to the shape of the first via hole borrowing hole 8 to be disposed therein. That is, the waveguide 100 has a plurality of first via borrowing holes 8 corresponding to the plurality of first via holes 5. In the example shown in the figure, the first via Kong Jieyong hole in which the first via 5a is provided is sometimes referred to as a first via Kong Jieyong hole 8a, and the first via Kong Jieyong hole in which the first via 5b is provided is sometimes referred to as a first via Kong Jieyong hole 8 b. The first via hole penetrates the inorganic material substrate 1, the second ground electrode 3, and the support substrate 7 through the via hole 8. Typically, the first via hole has a circular shape when viewed from the surface (upper surface) direction (upper side) of the inorganic material substrate 1 by means of the hole 8. 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, for example, 200 μm or less, preferably 100 μm or less, and more preferably 80 μm or less.

In fig. 2, the first via hole has a circular shape when viewed from the surface (upper surface) direction (upper side) of the inorganic material substrate 1 by way of the hole 8, and linearly penetrates the inorganic material substrate 1, the second ground electrode 3, and the support substrate 7 along the surface (upper surface) direction (thickness direction) of the inorganic material substrate 1. When the first via Kong Jieyong hole is circular and linear, the first via hole 5 has a cylindrical shape or a cylindrical shape extending in the direction (thickness direction) of the surface (upper surface) of the inorganic material substrate 1. In this case, the outer diameter range of the first via hole 5 is the same as the inner diameter range of the first via hole borrowing hole.

As shown in fig. 3, the first via hole borrowing hole 8 may have a circular shape when viewed from the surface (upper surface) direction (upper side) of the inorganic material substrate 1, and may have a tapered shape in which the inner diameter becomes smaller as approaching the second ground electrode 3. Although not shown, the first via hole 8 may have a circular shape when viewed from the direction (upward) of the surface (upper surface) of the inorganic material substrate 1, and may have a tapered shape in which the inner diameter increases as the second ground electrode 3 approaches.

If the first via Kong Jieyong hole is tapered, the conductor layer in the first via hole can be easily formed, and the strength of the substrate can be easily ensured. The first via hole may be formed by burying a conductive material in the first via hole.

In the case where the first via Kong Jieyong hole is circular and tapered, the structure of the first via hole 5 is not particularly limited, and the first via hole 5 preferably has: the contact portion with the second ground electrode 3 has a small diameter and is formed in an hourglass shape having a large diameter as it is separated from the second ground electrode 3. In other words, the first via hole 5 preferably has a shape in which apexes of 2 cones are connected to each other. In this case, the maximum outer diameter of the first via hole 5 is within the above-described range. In 1 embodiment, the outer diameter of one end portion of the first via hole 5 in contact with the first ground electrodes 2b, 2c is smaller than: the other end portion of the first via hole 5, which is in contact with the third ground electrode 4, has an outer diameter. In the first via hole 5, the taper angle on the conductor layer 2 side with respect to the second ground electrode is smaller than: taper angle on the third ground electrode side with respect to the second ground electrode.

In the example shown in the figure, the first ground electrode and the third ground electrode are each formed so as to seal the first via hole with a hole, but the configuration of each of the first ground electrode and the third ground electrode is not limited to this. The first ground electrode and the third ground electrode may be opened without plugging the first via hole, as long as they are in communication with the first via hole.

As shown in fig. 4, in the waveguide element 100, a plurality of first via holes 5a are arranged at intervals in the longitudinal direction of the signal electrode 2 a. The direction in which the plurality of first via holes 5a are arranged is not limited to the longitudinal direction of the signal electrode 2 a. As shown in fig. 5, the plurality of first via holes 5a may be arranged at intervals from each other in a direction intersecting (preferably orthogonal to) the longitudinal direction of the signal electrode 2 a. That is, the waveguide element may have a plurality of columns of the first via holes 5a arranged in the longitudinal direction of the signal electrode 2a in a direction intersecting (orthogonal to) the longitudinal direction of the signal electrode 2 a.

The pitch P1 of the plurality of first via holes 5a (the distance between the centers of the first via holes 5a adjacent to each other) is, for example, 40 μm or more, preferably 60 μm or more, for example, 600 μm or less, preferably 400 μm or less, and more preferably 200 μm or less.

The waveguide element 100 may include a plurality of first via holes 5b in the same manner as the first via holes 5 a.

H. Second via hole

As shown in fig. 7 to 9, in the waveguide element 101, the second via holes 6 are provided on both sides of the signal electrode 2a in a direction intersecting (preferably orthogonal to) the longitudinal direction of the signal electrode 2 a. Hereinafter, a second via hole for electrically connecting the first ground electrode 2b and the second ground electrode 3 may be referred to as a second via hole 6a, and a second via hole for electrically connecting the first ground electrode 2c and the third ground electrode 4 may be referred to as a second via hole 6 b. The second via hole 6a is in contact with the first ground electrode 2b and the second ground electrode 3, and is not in contact with the third ground electrode 4. The second via hole 6b is in contact with the first ground electrode 2c and the second ground electrode 3, and is not in contact with the third ground electrode 4. The waveguide element may be provided with only one of the second via holes 6a and 6 b.

Typically, the second via hole 6 is a conductive film. The second via hole 6 is made of a conductive material, typically the same metal as the first via hole 5. The shape of the second via hole 6 corresponds to the shape of the second via hole borrowing hole 9 to be disposed therein. That is, the waveguide element 101 has: the second via hole corresponding to the second via hole 6 is borrowed by the hole 9. In the example shown in the figure, the second via Kong Jieyong hole in which the second via 6a is provided is sometimes referred to as a second via Kong Jieyong hole 9a, and the second via Kong Jieyong hole in which the second via 6b is provided is sometimes referred to as a second via Kong Jieyong hole 9 b.

The second via borrowing hole 9 penetrates at least the inorganic material substrate 1 and does not penetrate the support substrate 7. Typically, the second via hole has a circular shape when viewed from the surface (upper surface) direction (upper side) of the inorganic material substrate 1 by means of the hole 9. When the second via hole borrowed hole has a circular shape, the inner diameter range of the second via hole borrowed hole is the same as that of the first via hole borrowed hole described above, for example.

In fig. 9, the second via hole has a circular shape when viewed from the surface (upper surface) direction (upper side) of the inorganic material substrate 1 by way of the hole 9, and penetrates the inorganic material substrate 1 in a straight line along the surface (upper surface) direction (thickness direction) of the inorganic material substrate 1. The second via borrowing hole 9 shown in fig. 9 and 10 does not penetrate the second ground electrode 3. In the case where the second via hole borrowing hole 9 is circular and linear, the second via hole 6 has a cylindrical shape or a cylindrical shape extending in the thickness direction of the inorganic material substrate 1. In this case, the outer diameter range of the second via hole 6 is the same as the inner diameter range of the second via hole borrowing hole.

As shown in fig. 11, the second via borrowing hole 9 may have: the tapered conical shape becomes thinner as it moves away from the conductor layer 2. The second via hole shown in fig. 11 penetrates the inorganic material substrate 1 and the second ground electrode 3 through the hole 9, and the tip end thereof reaches the support substrate 7. In the case where the second via hole 9 is conical, the structure of the second via hole 6 is not particularly limited, and the second via hole 6 is preferably: the same conical shape as the second via borrowing hole 9. In this case, the maximum outer diameter of the second via hole 6 is within the range of the inner diameter of the second via hole borrowing hole. In addition, the apex portion of the second via hole 6 (the end portion of the second via hole 6 on the opposite side from the conductor layer 2) can reach the support substrate 7.

In the example of the figure, the first ground electrode is formed as: the second via hole is plugged with a hole, but the configuration of the first ground electrode is not limited to this. The first ground electrode may be opened without blocking the second via hole by the hole.

As shown in fig. 10 to 13, the second via hole 6 is arranged in: among the plurality of first via holes 5 arranged in the predetermined direction, first via holes 5 adjacent to each other are located. Typically, the second via holes 6 are located at the center of the interval between the first via holes 5 adjacent to each other.

The waveguide element 101 of the illustrated example has a plurality of second via holes 6 (a plurality of second via holes 6a and a plurality of second via holes 6 b). In the waveguide element 101 shown in fig. 10 to 12, the second via hole 6 is arranged in: among the plurality of first via holes 5 (first via holes 5a or first via holes 5 b) arranged in the longitudinal direction of the signal electrode 2a, first via holes 5 adjacent to each other are located. In the waveguide element 101 shown in fig. 13, the second via hole 6 is arranged in: among the plurality of first via holes 5 (first via holes 5a or first via holes 5 b) arranged in a direction intersecting (preferably orthogonal to) the longitudinal direction of the signal electrode 2a, first via holes 5 adjacent to each other are provided.

The second via holes 6 may be disposed between the first via holes 5 adjacent to each other, and may be disposed at any appropriate position. The second via holes 6 may be arranged every n first via holes 5 in the direction in which the plurality of first via holes are arranged. N is, for example, 1 to 5, preferably 1 or 2. More preferably, the first via holes 5 and the second via holes 6 are alternately arranged. As shown in fig. 10 and 11, the plurality of second via holes 6 may be all arranged between the first via holes 5 adjacent to each other, and as shown in fig. 12, at least 1 second via hole 6 may be arranged between the first via holes 5 adjacent to each other, and may be included without being arranged between the first via holes 5.

The pitch P2 between the first via holes 5 and the second via holes 6 adjacent to each other (the distance between the centers of the first via holes 5a and the second via holes 6a adjacent to each other) is substantially 1/2 of the pitch P1 (the distance between the centers of the first via holes 5a adjacent to each other), for example, 25 μm or more, preferably 60 μm or more, for example, 600 μm or less, preferably 400 μm or less, more preferably 200 μm or less.

By disposing the second via holes 6 between the first via holes 5 adjacent to each other in this manner, the pitch P2 of the first via holes 5 and the second via holes 6 in the inorganic material substrate 1 can be made smaller than the pitch P1 of the first via holes 5 in the support substrate 7. Therefore, even if the inorganic material substrate is thinned as described above, the strength of the inorganic material substrate can be sufficiently ensured.

Further, as shown in fig. 11, if the first via hole borrowing hole 8 has a tapered shape in which the inner diameter becomes larger as it goes away from the second ground electrode 3, and the thickness of the support substrate 7 is larger than that of the inorganic material substrate 1, the outer diameter of the other end portion of the first via hole 5 in contact with the third ground electrode 4 may be larger than that of the third ground electrode 4: the outer diameter of one end portion of the first via hole 5 that is in contact with the first ground electrodes 2b, 2 c. In this case, if the second via holes 6 are not provided and the pitch of the plurality of first via holes 5 is narrowed like the pitch P2, there is a possibility that the other end portions of the first via holes 5 interfere with each other. In contrast, in the waveguide 101, the second via holes 6 are arranged between the first via holes 5 adjacent to each other, and therefore, interference between the first via holes 5 can be suppressed.

I. Third via hole

As shown in fig. 14, the waveguide element 101 may be provided with a plurality of third via holes 10 instead of the plurality of first via holes 5. The third via hole 10 is in contact with the second ground electrode 3 and the third ground electrode 4, and is not in contact with the first ground electrodes 2b, 2c 4. Typically, the third via hole 10 is a conductive film. The third via hole 10 is made of a conductive material, typically the same metal as the first via hole 5. The shape of the third via hole 10 corresponds to the shape of the substrate via hole borrowing hole 71 to be disposed therein. That is, the waveguide element 101 may have the substrate via borrowing hole 71 corresponding to the third via 10. The substrate via borrowing hole 71 penetrates at least the support substrate 7.

J. Method for manufacturing waveguide element

Next, a method of manufacturing the waveguide element 100 will be described with reference to fig. 1 and 2. In 1 embodiment, the method of manufacturing the waveguide element 100 includes the steps of: preparing a laminate 11, wherein the laminate 11 is provided with an inorganic material substrate 1, a second ground electrode 3 and a support substrate 7 in the following order, and the laminate 11 is provided with a first via borrowing hole 8 penetrating the inorganic material substrate 1, the second ground electrode 3 and the support substrate 7 uniformly; the conductor layer 2 is formed on the upper portion of the inorganic material substrate 1, the first via hole 5 is formed in the first via hole 8, and the third ground electrode 4 is formed on the lower portion of the support substrate 7.

For preparing the laminate 11, for example, the inorganic material substrate 1 and the support substrate 7 are directly bonded. When the inorganic material substrate 1 and the support substrate 7 are bonded via the second ground electrode 3, first, a metal constituting the second ground electrode 3 is sputtered on the surface of the inorganic material substrate 1 to form a first metal thin film as a first bonding portion. Further, a second metal thin film as a second joint portion is formed by sputtering a metal constituting the second ground electrode 3 on the surface of the support substrate 7. In addition, in the film formation of the first metal thin film and the second metal thin film, a metal film of Ti, cr, ni, pt, pd may be formed as an intermediate layer from the viewpoint of securing adhesion strength and preventing migration.

Next, in a high vacuum chamber (e.g., 1X 10 ^－6 Pa or so), and a neutralizing beam is irradiated to the bonding surface of each of the constituent elements (layers or substrates) to be bonded. Thereby, each joint surface is activated. Then, the activated bonding surfaces are brought into contact with each other in a vacuum atmosphere, and bonding is performed at room temperature. The load at the time of the joining may be, for example, 100N to 20000N. In 1 embodiment, when surface activation is performed by the neutralization beam, an inert gas is introduced into the chamber, and a high voltage is applied from a dc power supply to an electrode disposed in the chamber. With such a configuration, electrons move due to an electric field generated between the electrode (positive electrode) and the chamber (negative electrode), and a beam of atoms and ions of the inert gas is generated. The ion beam in the beam reaching the grid is neutralized at the grid, and therefore, a beam of neutral atoms is emitted from a high-speed atomic beam source. The atomic species constituting the beam are preferably inert gas elements (e.g., argon (Ar), nitrogen (N)). The voltage at the time of activation by irradiation with a beam is, for example, 0.5 to 2.0kV, and the current is, for example, 50 to 200mA. The method of direct bonding is not limited to this, and a surface activation method using FAB (Fast Atom Beam) or an ion gun, an atomic diffusion method, a plasma bonding method, or the like may be applied.

In this way, the first metal thin film as the first bonding portion and the second metal thin film as the second bonding portion are directly bonded to each other to form the second ground electrode 3. Accordingly, the laminate 11 having the structure of the inorganic material substrate 1, the second ground electrode 3, and the support substrate 7 was obtained.

In addition, when the inorganic material substrate 1 and the support substrate 7 are joined together via the second ground electrode 3 and the joining portion, the second ground electrode 3 is formed on the surface of the inorganic material substrate 1 by sputtering in order to prepare the laminate 11. Next, the above-mentioned junction was formed on the second ground electrode 3 (more specifically, a Cr thin film having a thickness of 0.02 μm and an amorphous silicon layer having a thickness of 0.1 μm were formed in this order). After film formation, planarization treatment is performed by, for example, CMP polishing. If necessary, the support substrate is also formed with a joint portion in the same manner as in the above operation.

Next, the inorganic material substrate and the support substrate are directly bonded in the same manner as the above operation. Accordingly, the laminate 11 having the structure of the inorganic material substrate 1, the second ground electrode 3, the joint portion, and the support substrate 7 was obtained.

Then, for example, laser processing (more specifically, processing using laser light having a wavelength of 515nm and a pulse width of 10 ps) is performed to form: first through-holes Kong Jieyong a, 8b penetrating the inorganic material substrate 1, the second ground electrode 3, and the support substrate 7 are unified.

Next, a base metal thin film is formed (more specifically, a Ti thin film having a thickness of 0.15 μm and a palladium thin film having a thickness of 0.04 μm are sequentially formed in this order) on the side wall portions in the first via Kong Jieyong holes 8a and 8b, the front surface of the inorganic material substrate 1, and the rear surface of the support substrate 7 by, for example, an ICP (inductively coupled plasma) sputtering apparatus, and then, a surface metal thin film (for example, a copper thin film having a thickness of 1.5 μm) is formed by, for example, plating (more specifically, electric field plating).

Thereafter, a resist is applied to the metal thin film on the surface of the inorganic material substrate 1, and the resist is patterned by photolithography so that the portion of the gap where the conductor layer 2 is formed is exposed and the other portion is masked. Thereafter, the conductor layer 2 (coplanar electrode or microstrip electrode) is formed by, for example, wet etching (more specifically, ferrous chloride).

Accordingly, a conductor layer is formed on the upper portion of the inorganic material substrate 1, a first via hole 5 is formed in the first via hole 8, and a third ground electrode 4 is formed on the lower portion of the support substrate 7. Therefore, the waveguide element can be manufactured smoothly as compared with the case where the conductor layer, the first via hole, and the third ground electrode are formed separately. After that, the resist is removed. In the above embodiment, the conductor layer 2 is formed by etching after the first via hole 5 and the third ground electrode 4 are formed, but the present invention is not limited thereto. The first via hole 5, the third ground electrode 4, and the conductor layer 2 may be formed at the same time.

Next, a method of manufacturing the waveguide element 101 will be described with reference to fig. 7 to 9. In 1 embodiment, the method of manufacturing the waveguide element 101 includes the steps of: preparing a laminate 12, wherein the laminate 12 comprises an inorganic material substrate 1, a second ground electrode 3 and a support substrate 7 in this order, and the laminate 12 comprises a first via borrowing hole 8 penetrating the inorganic material substrate 1, the second ground electrode 3 and the support substrate 7 in a unified manner, and a second via borrowing hole 9 penetrating the inorganic material substrate 1 but not penetrating the support substrate 7; a first via hole 5 is formed in the first via hole 8, a second via hole 6 is formed in the second via hole 9, a third ground electrode 4 is formed at the lower portion of the support substrate 7, and a conductor layer 2 is formed at the upper portion of the inorganic material substrate 1.

The laminate 12 is prepared by directly bonding an inorganic material substrate and a support substrate, as in the laminate 11.

Then, for example, laser processing (more specifically, processing using laser light having a wavelength of 515nm and a pulse width of 10 ps) is performed to form: the first via borrowing hole 8 penetrating the inorganic material substrate 1, the second ground electrode 3, and the support substrate 7, and the second via borrowing hole 9 penetrating the inorganic material substrate 1 but not penetrating the support substrate 7 are unified.

Next, a base metal thin film (more specifically, a Ti thin film having a thickness of 0.15 μm and a palladium thin film having a thickness of 0.04 μm are sequentially formed in this order) is formed on the side wall portions in the first via hole 8 and the second via hole 9, the front surface of the inorganic material substrate 1, and the rear surface of the support substrate 7 by, for example, an ICP (inductively coupled plasma) sputtering apparatus, and then, a surface metal thin film (for example, a copper thin film having a thickness of 1.5 μm) is formed by, for example, plating (more specifically, electric field plating).

Then, the metal thin film on the surface of the inorganic material substrate 1 is masked and etched in the same manner as described above, to form the conductor layer 2 (coplanar electrode or microstrip electrode).

Accordingly, a conductor layer is formed on the upper portion of the inorganic material substrate 1, a first via hole 5 is formed in the first via hole 8, a second via hole 6 is formed in the second via hole 9, and a third ground electrode 4 is formed on the lower portion of the support substrate 7. Therefore, the waveguide element can be manufactured smoothly as compared with the case where the conductor layer, the first via hole, the second via hole, and the third ground electrode are formed separately. After that, the resist is removed. In the above embodiment, the conductor layer 2 is formed by etching after the first via hole 5, the second via hole 6, and the third ground electrode 4 are formed, but the present invention is not limited thereto. The first via hole 5, the second via hole 6, the third ground electrode 4, and the conductor layer 2 may also be formed at the same time.

By the above operation, the waveguide element 101 can be manufactured.

In the above-described operation, the step of preparing the laminated body having the first via-borrowed hole and the second via-borrowed hole by forming the laminated body after forming the laminated body is described in detail, but the step of preparing the laminated body is not limited thereto. The inorganic material substrate, the second ground electrode, and the support substrate may be bonded to each other so that the holes communicate with each other to form the first via borrowed hole.

Examples

The present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

Reference example 1 >

1-1. Fabrication of waveguide elements (coplanar lines)

A quartz glass wafer (quartz glass substrate, inorganic material substrate) having a thickness of 0.5mm was prepared, and an amorphous silicon film of 0.2 μm was formed on the quartz glass wafer by sputtering. After the film formation, the amorphous silicon film is polished and planarized. Here, the arithmetic average roughness of ≡10μm (10 μm square region; the same applies hereinafter) of the surface of the amorphous silicon film was measured using an atomic force microscope, and found to be 0.2nm.

In addition, a silicon wafer (support substrate) having a thickness of 525 μm was prepared. The arithmetic average roughness of ≡10 μm surface of the silicon wafer was measured using an atomic force microscope, and found to be 0.2nm.

The amorphous silicon surface of the quartz glass wafer and the silicon wafer were directly bonded as follows. First, a quartz glass wafer and a silicon wafer are placed in a vacuum chamber at 10 ^－6 In a vacuum of about Pa, a high-speed neutral Ar atomic beam (acceleration voltage 1kV, ar flow rate 60 seem) was irradiated to the junction surface of both (amorphous silicon surface of quartz glass wafer and surface of silicon wafer) for 70 seconds. After the irradiation, the glass quartz wafer and the silicon wafer were left to stand for 10 minutes, and after cooling, the bonding surfaces of the glass quartz wafer and the silicon wafer (the surface beam irradiation surfaces of the glass quartz wafer and the silicon wafer) were brought into contact, and the glass quartz wafer and the silicon wafer were bonded by pressing at 4.90kN for 2 minutes. After bonding, the quartz glass wafer was polished until its thickness reached 150 μm, to form a composite wafer. In the obtained quartz glass/silicon composite substrate, no defects such as peeling were observed at the bonding interface.

Next, a resist is applied to the surface (polished surface) of the quartz glass wafer opposite to the silicon wafer, and a pattern is formed by photolithography so that the portion where the coplanar electrode pattern is formed is exposed. Then, a base electrode was formed by sputtering the upper surface of the quartz glass wafer exposed from the resist to form a Cr film 50nm thick and a Ni film 100nm thick. Further, copper is formed on the base electrode by electroplating to form a coplanar electrode pattern. The length of the signal electrode in the waveguide direction was 10mm.

By the above operation, a waveguide element is obtained, which includes: coplanar electrodes, an inorganic material substrate, and a support substrate.

1-2. Calculation of propagation loss

In order to measure propagation loss of the waveguide element, 3 waveguide elements having signal electrodes of 30mm, 40mm and 50mm in length were fabricated in the same manner as described above.

Next, an RF signal generator is connected to the input side of the waveguide via a probe, and a probe is provided on the output side of the waveguide to combine the electromagnetic wave with an RF signal receiver.

Next, a voltage was applied to the RF signal generator, and the RF signal generator was caused to transmit electromagnetic waves having the frequencies shown in table 1. Thereby, the electromagnetic wave is propagated to the coplanar line (waveguide element). The RF signal receiver measures the RF power of the electromagnetic wave output from the coplanar line. Propagation loss (dB/cm) was calculated from the measurement results of 3 kinds of waveguide elements having different lengths of the signal electrodes, and the measurement was evaluated based on the following criteria. The results are shown in Table 1.

Excellent (excellent): less than 0.5dB/cm

((good): 0.5dB/cm or more and less than 1dB/cm

Delta (cocoa): more than 1dB/cm and less than 2dB/cm

X (not): more than 2dB/cm

Reference example 2 >

2-1. Fabrication of waveguide elements (coplanar lines with ground)

A quartz glass wafer (quartz glass substrate, inorganic material substrate) having a thickness of 0.5mm was prepared, and a base electrode was formed on the quartz glass wafer by sputtering to form a Cr film having a thickness of 50nm and a Ni film having a thickness of 100 nm. Further, copper is formed on the base electrode by electroplating, thereby forming a second ground electrode. Next, an amorphous silicon film of 0.2 μm was formed on the second ground electrode by sputtering. After the film formation, the amorphous silicon film is polished and planarized. Here, the arithmetic average roughness of ≡10 μm of the surface of the amorphous silicon film was measured using an atomic force microscope, and found to be 0.2nm.

In addition, a silicon wafer (support substrate) having a thickness of 525 μm was prepared. The arithmetic surface roughness average of ≡10 μm of the surface of the silicon wafer was measured using an atomic force microscope, and found to be 0.2nm.

Then, the amorphous silicon surface formed on the ground electrode and the silicon wafer are directly bonded. The direct bonding was performed in the same manner as in reference example 1. In the obtained quartz glass/second ground electrode/silicon composite substrate, no defects such as peeling were observed at the bonding interface.

Next, the quartz glass wafer was polished to a thickness of 150. Mu.m.

Next, as in reference example 1, a coplanar electrode pattern was formed on the surface (polished surface) of the quartz glass wafer opposite to the silicon wafer. The length of the signal electrode in the waveguide direction was 10mm.

By the above operation, a waveguide element is obtained, and the waveguide element is provided with: a coplanar electrode, an inorganic material substrate, a second ground electrode, and a support substrate.

2-2. Calculation of propagation loss

In order to measure the propagation loss of the waveguide element, 3 waveguide elements having signal electrodes of 30mm, 40mm and 50mm in length were fabricated in the same manner as described above. Next, the RF power of the electromagnetic wave output from the coplanar line was measured by the RF signal receiver in the same manner as in reference example 1. The propagation loss of the waveguide element of reference example 2 was evaluated in the same manner as in reference example 1. The results are shown in Table 1.

Reference example 3 >

3-1. Fabrication of waveguide element (microstrip line)

A quartz glass/second ground electrode/silicon composite substrate was obtained in the same manner as in reference example 2.

Next, a resist is applied to the surface (polished surface) of the quartz glass wafer opposite to the silicon wafer, and a pattern is formed by photolithography so that the portion where the microstrip electrode is formed is exposed. Then, a base electrode was formed by sputtering the upper surface of the quartz glass wafer exposed from the resist to form a Cr film 50nm thick and a Ni film 100nm thick. Further, copper is formed on the base electrode by electroplating to form a microstrip electrode. The length of the microstrip electrode in the waveguide direction was 10mm.

By the above operation, a waveguide element is obtained, and the waveguide element is provided with: microstrip electrode, inorganic material substrate and support substrate.

3-2. Calculation of propagation loss

In order to measure propagation loss of the waveguide element, 3 waveguide elements having microstrip electrodes with lengths of 30mm, 40mm and 50mm were fabricated in the same manner as described above. Next, the RF power of the electromagnetic wave output from the coplanar line was measured by the RF signal receiver in the same manner as in reference example 1. The propagation loss of the waveguide element of reference example 3 was evaluated in the same manner as in reference example 1. The results are shown in Table 1.

Reference examples 4 to 6

A waveguide element was produced in the same manner as in each of reference examples 1 to 3 except that the thickness of the polished quartz glass wafer (inorganic material substrate) was changed to the value shown in table 1.

The propagation loss of the obtained waveguide element was calculated and evaluated in the same manner as in reference example 1. The results are shown in Table 1.

Reference example 7 >

A waveguide element was produced in the same manner as in reference example 1, except that the quartz glass wafer as the inorganic material substrate was changed to a single crystal silicon wafer, and the thickness of the polished silicon wafer was changed to the value shown in table 1.

Reference example 8 >

A waveguide element was produced in the same manner as in reference example 1, except that the quartz glass wafer as the inorganic material substrate was changed to a sapphire wafer, and the thickness of the polished sapphire wafer was changed to the value shown in table 1.

Reference example 9 >

A waveguide element was produced in the same manner as in reference example 1, except that the quartz glass wafer as the inorganic material substrate was changed to a polycrystalline AlN wafer, and the thickness of the AlN wafer after polishing was changed to the value shown in table 1.

Reference example 10 >

A waveguide element was produced in the same manner as in reference example 1, except that the thickness of the polished quartz glass wafer (inorganic material substrate) was changed to the value shown in table 1.

Reference examples 11 to 14

A waveguide element was produced in the same manner as in reference example 3, except that the thickness of the polished quartz glass wafer (inorganic material substrate) was changed to the value shown in table 1.

Reference example 15 >

A waveguide element was produced in the same manner as in reference example 2 except that the thickness of the polished quartz glass wafer was changed to 300 μm.

Reference example 16 >

A waveguide element was produced in the same manner as in reference example 3 except that a quartz glass wafer (quartz glass plate, inorganic material substrate) having a thickness of 2100 μm was prepared and the thickness of the polished quartz glass wafer was changed to 2000 μm.

TABLE 1

As can be seen from table 1: when the thickness of the inorganic material substrate satisfies the above formula (1), propagation loss when electromagnetic waves having a high frequency exceeding 30GHz are guided is relatively small.

Industrial applicability

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 in particular, can be suitably used as a waveguide for millimeter waves to terahertz waves. Such a waveguide element can be used for, for example, an antenna, a band-pass filter, a coupler, a delay line (phaser), or an isolator.

Symbol description

1. Inorganic material substrate

2. Conductor layer

2a signal electrode

2b, 2c first ground electrode

3. Second ground electrode

4. Third ground electrode

5. First via hole

6. Second via hole

8. Via borrowing hole

11. Laminate body

12. Laminate body

Claims

1. A waveguide element capable of guiding electromagnetic waves having a frequency of 30GHz or more and 20THz or less,

the waveguide element is characterized by comprising:

an inorganic material substrate;

a conductor layer provided on an upper portion of the inorganic material substrate, the conductor layer including a signal electrode extending in a predetermined direction and a first ground electrode disposed at a distance from the signal wiring in a direction intersecting the predetermined direction;

a support substrate located on the opposite side of the conductor layer from the inorganic material substrate;

A second ground electrode located between the inorganic material substrate and the support substrate; and

a third ground electrode located on an opposite side of the second ground electrode with respect to the support substrate,

the first ground electrode, the second ground electrode, and the third ground electrode are electrically connected,

the thickness t of the inorganic material substrate satisfies the following formula (1),

[ mathematics 1]

Where t represents the thickness of the inorganic material substrate, λ represents the wavelength of electromagnetic waves guided by the waveguide element, ε represents the relative dielectric constant of the inorganic material substrate at 300GHz, and a represents a value of 3 or more.

2. The waveguide element according to claim 1, wherein,

the waveguide element further includes a first via hole that electrically connects the first ground electrode and the third ground electrode, and electrically connects the second ground electrode.

3. The waveguide element according to claim 2, wherein,

the waveguide element further includes a first via Kong Jieyong hole, which is provided by the first via hole, penetrates the inorganic material substrate, the second ground electrode, and the support substrate.

4. A waveguide element according to claim 3, wherein,

the first via Kong Jieyong hole has a circular shape when viewed from the upper surface direction, which is the surface direction of the inorganic material substrate, and has a tapered shape in which the inner diameter becomes smaller as approaching the second ground electrode.

5. A waveguide element according to claim 3, wherein,

the first via Kong Jieyong hole has a circular shape when viewed from the upper surface direction, which is the surface direction of the inorganic material substrate, and has a tapered shape with a diameter that becomes larger as approaching the second ground electrode.

6. The waveguide element according to any one of claims 2 to 5,

the waveguide element further includes a second via hole electrically connecting the first ground electrode and the second ground electrode,

the waveguide element is provided with a plurality of the first via holes,

the second via hole is disposed between adjacent ones of the plurality of first via holes.

7. The waveguide element according to claim 6, wherein,

the waveguide element has a second via Kong Jieyong hole, which is provided by the second via hole, penetrates the inorganic material substrate, and does not penetrate the support substrate.

8. The waveguide element according to claim 1, wherein,

the waveguide element further includes:

a second via electrically connecting the first ground electrode and the second ground electrode; and

and a third via hole electrically connecting the second ground electrode and the third ground electrode.

9. The waveguide element according to any one of claims 1 to 8,

in the formula (1), a represents a value of 6 or more.

10. The waveguide element according to any one of claims 1 to 9, characterized in that,

the relative dielectric constant epsilon at 300GHz of the inorganic material substrate is 3.5-12.0, and the dielectric loss tangent tan delta at 300GHz of the inorganic material substrate is 0.003 or less.

11. The waveguide component according to claim 10, wherein,

the inorganic material substrate is a quartz glass substrate.

12. The waveguide element according to any one of claims 1 to 11,

the conductor layer is a coplanar electrode.

13. The waveguide element according to any one of claims 1 to 11,

the conductor layer and the second grounding electrode are microstrip type electrodes.

14. Waveguide element according to claim 12 or 13, characterized in that,

when the frequency of the electromagnetic wave propagating through the waveguide element is 30GHz or more and 5THz or less, the thickness of the inorganic material substrate is 10 μm or more.

15. A method for manufacturing a waveguide element according to any one of claims 2 to 5, comprising the steps of:

preparing a laminate having the inorganic material substrate, the second ground electrode, and the support substrate in this order, the laminate having first through-holes Kong Jieyong uniformly penetrating them;

the first via hole is formed in the first via Kong Jieyong hole, the third ground electrode is formed in the lower portion of the support substrate, and the conductor layer is formed in the upper portion of the inorganic material substrate.

16. A method for manufacturing a waveguide according to claim 6, comprising the steps of:

preparing a laminate including the inorganic material substrate, the second ground electrode, and the support substrate in this order, wherein the laminate includes first via holes penetrating the inorganic material substrate, the second ground electrode, and the support substrate in a unified manner, and second via Kong Jieyong holes penetrating the inorganic material substrate but not penetrating the support substrate;

The first via hole is formed in the first via Kong Jieyong hole, the second via hole is formed in the second via Kong Jieyong hole, the third ground electrode is formed on the lower portion of the support substrate, and the conductor layer is formed on the upper portion of the inorganic material substrate.