WO2025062479A1 - アンテナ素子 - Google Patents

アンテナ素子 Download PDF

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Publication number
WO2025062479A1
WO2025062479A1 PCT/JP2023/033878 JP2023033878W WO2025062479A1 WO 2025062479 A1 WO2025062479 A1 WO 2025062479A1 JP 2023033878 W JP2023033878 W JP 2023033878W WO 2025062479 A1 WO2025062479 A1 WO 2025062479A1
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WIPO (PCT)
Prior art keywords
inorganic material
material substrate
antenna element
conductor layer
substrate
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/JP2023/033878
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English (en)
French (fr)
Japanese (ja)
Inventor
健太郎 谷
順悟 近藤
直剛 岡田
真人 丹羽
省一郎 山口
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NGK Insulators Ltd
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NGK Insulators Ltd
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Filing date
Publication date
Application filed by NGK Insulators Ltd filed Critical NGK Insulators Ltd
Priority to JP2024538420A priority Critical patent/JP7821888B2/ja
Priority to PCT/JP2023/033878 priority patent/WO2025062479A1/ja
Priority to CN202380101902.1A priority patent/CN121866686A/zh
Priority to DE112023000587.7T priority patent/DE112023000587T5/de
Publication of WO2025062479A1 publication Critical patent/WO2025062479A1/ja
Anticipated expiration legal-status Critical
Pending legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q9/00—Electrically-short antennas having dimensions not more than twice the operating wavelength and consisting of conductive active radiating elements
    • H01Q9/04—Resonant antennas
    • H01Q9/0407—Substantially flat resonant element parallel to ground plane, e.g. patch antenna

Definitions

  • the present invention relates to an antenna element.
  • electromagnetic wave sensors that detect an object by transmitting electromagnetic waves to the object and receiving the waves reflected by the object.
  • an antenna element capable of transmitting and/or receiving electromagnetic waves is applied to such electromagnetic wave sensors.
  • an antenna element for example, a single antenna has been proposed that includes a dielectric substrate, a signal conversion unit disposed on the front surface of the dielectric substrate, and a ground plate disposed on the back surface of the dielectric substrate (see Patent Document 1).
  • a primary object of the present invention is to provide an antenna element capable of realizing a wide band of available electromagnetic waves.
  • An antenna element includes an inorganic material substrate, a first conductor layer, a support substrate, a cavity, and a ground conductor layer.
  • the first conductor layer is disposed on one side of the inorganic material substrate in a thickness direction.
  • the first conductor layer includes a patch antenna.
  • the support substrate is disposed on the opposite side of the inorganic material substrate to the first conductor layer.
  • the cavity is disposed on the opposite side of the inorganic material substrate to the first conductor layer and on the inorganic material substrate side of the support substrate.
  • the ground conductor layer is disposed within the cavity. The ground conductor layer is capable of generating an electric field between the patch antenna and the support substrate.
  • the thickness t of the inorganic material substrate satisfies the following formula (1).
  • t represents the thickness of the inorganic material substrate
  • ⁇ represents the wavelength of the electromagnetic wave transmitted and/or received by the antenna element
  • ⁇ represents the relative dielectric constant of the inorganic material substrate
  • a represents a numerical value of 3 or more.
  • the first conductor layer may further include a transmission line.
  • the transmission line is connected to the patch antenna.
  • the antenna element according to [3] above may further include a first ground layer.
  • the first ground layer is disposed between the inorganic material substrate and the support substrate in a portion different from the cavity. When the transmission line is projected in a thickness direction of the inorganic material substrate, at least a portion of the projection surface of the transmission line overlaps with the first ground layer.
  • the antenna element according to the above [4] may further include a joint portion that joins the inorganic material substrate and the support substrate.
  • the bonding portion may include a first bonding layer and a second bonding layer.
  • the first bonding layer is provided on a surface of the inorganic material substrate opposite to the first conductor layer in a thickness direction of the inorganic material substrate.
  • the second bonding layer is provided on a surface of the first ground layer opposite to the support substrate in a thickness direction of the inorganic material substrate.
  • the second bonding layer is bonded to the first bonding layer.
  • a thickness t of the inorganic material substrate may be 100 ⁇ m or less.
  • the frequency of the electromagnetic waves transmitted and/or received by the antenna element may be 20 GHz to 20 THz.
  • the inorganic material substrate may be made of quartz glass.
  • the supporting substrate may be made of silicon.
  • Embodiments of the present invention can achieve a wider bandwidth of available electromagnetic waves.
  • FIG. 1 is a schematic perspective view of an antenna element according to an embodiment of the present invention.
  • FIG. 2 is a cross-sectional view of the antenna element of FIG. 1 taken along line II-II'.
  • FIG. 3 is a schematic perspective view of an antenna element according to another embodiment of the present invention.
  • FIG. 4 is a schematic perspective view of an antenna element according to yet another embodiment of the present invention.
  • FIG. 5 is a schematic perspective view of an antenna element according to yet another embodiment of the present invention.
  • FIG. 6 is a schematic perspective view of an antenna element according to yet another embodiment of the present invention.
  • FIG. 7 is a schematic perspective view of a support substrate and a second conductor layer included in the antenna element of FIG.
  • FIG. 8 is a schematic perspective view showing another embodiment of the second conductor layer of FIG.
  • FIG. 9 is a schematic perspective view showing yet another embodiment of the second conductor layer of FIG.
  • FIG. 10 is a graph showing the S11 parameter of the antenna element of the first embodiment.
  • FIG. 11 is a graph showing the S11 parameter in the antenna element of the first comparative example.
  • FIG. 1 is a schematic perspective view of an antenna element according to one embodiment of the present invention
  • Fig. 2 is a cross-sectional view of the antenna element of Fig. 1 taken along line II-II'.
  • the antenna element 100 is typically capable of transmitting and/or receiving electromagnetic waves in the range of millimeter waves to terahertz waves. Millimeter waves are typically electromagnetic waves with frequencies of about 20 GHz to 300 GHz, and terahertz waves are typically electromagnetic waves with frequencies of about 300 GHz to 20 THz.
  • the frequency of the electromagnetic waves that the antenna element can transmit and/or receive is, for example, 20 GHz to 20 THz, or, for example, 20 GHz to 500 GHz, or, for example, 20 GHz to 300 GHz, or, for example, 100 GHz to 200 GHz.
  • the antenna element 100 includes an inorganic material substrate 2, a first conductor layer 1, a support substrate 3, a cavity 5, and a ground conductor layer 41.
  • the first conductor layer 1 is disposed on one side of the inorganic material substrate 2 in the thickness direction.
  • the first conductor layer 1 includes a patch antenna 11.
  • the support substrate 3 is disposed on the opposite side of the inorganic material substrate 2 to the first conductor layer 1.
  • the cavity 5 is disposed on the opposite side of the inorganic material substrate 2 to the first conductor layer 1, and on the inorganic material substrate side of the support substrate 3.
  • the ground conductor layer 41 is disposed in the cavity 5.
  • the patch antenna 11, the ground conductor layer 41, and the inorganic material substrate 2 located therebetween typically constitute a planar antenna.
  • the ground conductor layer 41 can generate an electric field between the patch antenna 11. More specifically, when the patch antenna 11 receives and/or transmits the above-mentioned high-frequency electromagnetic waves, an electric field is generated between the patch antenna 11 and the ground conductor layer 41.
  • the thickness t of the inorganic material substrate 2 satisfies the following formula (1): When the patch antenna 11 is projected in the thickness direction of the inorganic material substrate 2 , at least a part of the projection surface of the patch antenna 11 overlaps with the cavity 5 .
  • t represents the thickness of the inorganic material substrate 2
  • ⁇ represents the wavelength of the electromagnetic wave transmitted and/or received by the antenna element 100
  • ⁇ represents the relative dielectric constant of the inorganic material substrate 2
  • a represents a numerical value of 3 or more.
  • These features can sufficiently reduce the reflection loss of the electromagnetic wave in the antenna element 100.
  • the bandwidth of the electromagnetic wave with sufficiently small reflection loss i.e., the bandwidth of the electromagnetic wave with the S11 parameter representing the reflection loss being equal to or less than a predetermined value, can be expanded in the antenna element 100.
  • the antenna element 100 can function as a wideband antenna.
  • the bandwidth of the electromagnetic waves (-10 dB bandwidth) in which the S11 parameter (reflection loss) of the antenna element 100 is -10 dB or less is, for example, 5.0 GHz or more, preferably 8.0 GHz or more, more preferably 10.0 GHz or more, and even more preferably 13.0 GHz or more.
  • the upper limit of the -10 dB bandwidth of the antenna element 100 is typically 50 GHz.
  • the S11 parameter is measured by, for example, a network analyzer.
  • development of miniaturization of the antenna element 100 is underway, and since circuit integration is expected in the future, it is expected that there will be a corresponding demand for miniaturization of the antenna element 100.
  • the thickness of the inorganic material substrate 2 satisfies the above formula (1), and the inorganic material substrate 2 is made thin, so that the antenna element 100 can be made broadband while also meeting the demand for miniaturization.
  • the area ratio of the portion of the projection surface of the patch antenna 11 that overlaps with the cavity 5 is, for example, 70% or more, preferably 80% or more, and more preferably 90% or more.
  • the broadband of the antenna element 100 can be stably achieved.
  • the entire projection surface of the patch antenna 11 overlaps with the cavity 5.
  • the area ratio of the portion of the projection surface of the patch antenna 11 that overlaps with the cavity 5 is 100%.
  • the projected area of the cavity 5 is equal to or greater than the projected area of the patch antenna 11.
  • the projected area of the cavity 5 is, for example, 1 to 4 times, and preferably 1 to 3 times, the projected area of the patch antenna 11. If the projected area of the cavity 5 has such a relationship with the projected area of the patch antenna 11, the patch antenna 11 can be easily positioned so that the patch antenna 11 overlaps the cavity 5 when viewed from the thickness direction of the inorganic material substrate 2. This improves the freedom of design of the patch antenna 11, and makes it possible to more stably achieve a broadband antenna element 100.
  • the outer edge of the projection surface of the cavity 5 is spaced apart from the outer edge of the projection surface of the patch antenna 11.
  • the distance L between the outer edge of the projection surface of the cavity 5 and the outer edge of the projection surface of the patch antenna 11 is, for example, 0 ⁇ m to ⁇ /2 ⁇ ⁇ m, for example, 0 ⁇ m to ⁇ /4 ⁇ ⁇ m.
  • ⁇ represents the relative dielectric constant of the inorganic material substrate 2. If the distance L between the outer edges of the cavity 5 and the patch antenna 11 is within this range, the design freedom of the patch antenna 11 can be further improved, and the broadband of the antenna element 100 can be more stably achieved.
  • the patch antenna 11 has any suitable shape.
  • Examples of the shape of the patch antenna 11 when viewed from the thickness direction of the inorganic material substrate 2 include a triangle, a square, a pentagon, a polygon having at least a hexagon, a circle, and an ellipse.
  • the patch antenna 11 has a substantially rectangular shape when viewed from the thickness direction of the inorganic material substrate 2.
  • the cavity 5 has any appropriate shape.
  • the cavity 5 has a similar shape to the patch antenna 11 when viewed in the thickness direction of the inorganic material substrate 2.
  • the cavity 5 and the patch antenna 11 have similar shapes to each other, and the center of the patch antenna 11 and the center of the cavity 5 are positioned on the same axis along the thickness direction of the inorganic material substrate 2.
  • the first conductor layer 1 further includes a transmission line 12 in addition to the patch antenna 11.
  • the transmission line 12 is connected to the patch antenna 11.
  • the end of the transmission line 12 opposite the patch antenna 11 is typically configured to be connectable to an external device.
  • an electrical signal input from an external device can be supplied to the patch antenna 11 via the transmission line 12.
  • the patch antenna 11 and the ground conductor layer 41 can convert the electrical signal into an electromagnetic wave. Therefore, the patch antenna 11 can radiate the electromagnetic wave converted from the electrical signal.
  • the patch antenna 11 and the ground conductor layer 41 can convert the electromagnetic wave into an electrical signal. Therefore, the antenna element 100 can transmit the electrical signal converted from the electromagnetic wave to an external device via the transmission line 12.
  • the transmission line 12 typically has a flat band shape extending in a specific direction.
  • the width of the transmission line 12 is, for example, 2 ⁇ m to 800 ⁇ m.
  • the direction in which the transmission line 12 extends is typically substantially parallel to the width direction of the patch antenna 11.
  • the patch antenna 11 and the transmission line 12 are configured to be impedance matched.
  • the patch antenna 11 may have a notch 111.
  • the notch 111 is provided adjacent to a connection portion of the patch antenna 11 to the transmission line 12.
  • the notch 111 may have any appropriate configuration.
  • the notch 111 is recessed inward from the outer edge of the patch antenna 11.
  • the patch antenna 11 may have a slit 112.
  • the slit 112 penetrates the patch antenna 11 in the thickness direction.
  • the slit 112 may have any appropriate configuration.
  • the slit 112 has a substantially U-shape when viewed from the thickness direction of the inorganic material substrate 2.
  • the transmission line 12 may have a narrow portion 121 and a wide portion 122.
  • the narrow portion 121 is located at an end of the transmission line 12 on the patch antenna 11 side.
  • the narrow portion 121 is connected to the patch antenna 11.
  • the width of the narrow portion 121 is smaller than the width of the wide portion 122.
  • the width of the narrow portion 121 is adjusted arbitrarily and appropriately.
  • the wide portion 122 is located on the opposite side of the narrow portion 121 to the patch antenna 11.
  • the width range of the wide portion 122 is, for example, the same as the width range of the transmission line 12 described above.
  • the transmission line 12 constitutes a waveguide capable of propagating electromagnetic waves. This allows electromagnetic waves to be supplied to the patch antenna 100.
  • the transmission line 12 constitutes a microstrip line together with the first ground layer 42.
  • the transmission line 12 constituting the microstrip line may be referred to as an MS type signal wiring 12a below.
  • the antenna element 100 includes the patch antenna 11, a ground conductor layer 41, the MS type signal wiring 12a, and the first ground layer 42, and constitutes a microstrip patch antenna.
  • the width of the MS type signal wiring 12a is, for example, 20 ⁇ m to 800 ⁇ m, and preferably 50 ⁇ m to 500 ⁇ m.
  • the first ground layer 42 is typically disposed between the inorganic material substrate 2 and the supporting substrate 3 in a portion different from the cavity 5.
  • the transmission line 12 (MS type signal wiring 12a) is projected in the thickness direction of the inorganic material substrate 2, at least a portion of the projection surface of the transmission line 12 overlaps with the first ground layer 42.
  • an electric field is generated between the MS type signal wiring 12a and the first ground layer 42. Therefore, an electromagnetic wave input from an external device is coupled with the electric field generated between the MS type signal wiring 12a and the first ground layer 42, propagates through the inorganic material substrate 2, and can reach the patch antenna 11.
  • the patch antenna 11 receives an electromagnetic wave, the electromagnetic wave can be transmitted to the external device by propagating through the inorganic material substrate 2 due to the electric field generated between the MS type signal wiring 12a and the first ground layer 42.
  • the transmission line 12 and the second ground layer 13 form a coplanar line.
  • the first conductor layer 1 further includes the second ground layer 13.
  • the transmission line 12 forming the coplanar line may be referred to as a CP type signal wiring 12b hereinafter.
  • the antenna element 100 includes the patch antenna 11, the ground conductor layer 41, the CP type signal wiring 12b, and the second ground layer 13, and forms a coplanar patch antenna.
  • the width of the CP type signal wiring 12b is, for example, 2 ⁇ m to 200 ⁇ m, and preferably 20 ⁇ m to 150 ⁇ m.
  • the second ground layer 13 is disposed so as to sandwich the transmission line 12 (CP type signal wiring 12b) in a direction perpendicular to the extension direction of the transmission line 12.
  • a gap (slit) is formed between the second ground layer 13 and the transmission line 12 (CP type signal wiring 12b) in the direction perpendicular to the extension direction of the transmission line 12.
  • the width of the gap is, for example, 2 ⁇ m to 100 ⁇ m, and preferably 5 ⁇ m to 80 ⁇ m.
  • the second ground layer 13 may be provided so as to surround the patch antenna 11 in addition to the transmission line 12.
  • the above-mentioned gap (slit) is formed between the second ground layer 13 and the patch antenna 11. This allows the antenna to be configured with a different design than the configuration in FIG. 5.
  • the antenna element 100 including the CP type signal wiring 12b preferably further includes the above-mentioned first ground layer 42.
  • the first ground layer 42 and the second ground layer 13 may be electrically connected.
  • the ground can be strengthened and stray capacitance due to surrounding lines and elements can be suppressed.
  • the first ground layer 42 and the second ground layer 13 are short-circuited by forming a plurality of via holes in the inorganic material substrate 2 and providing a via in each of the via holes.
  • antenna element includes both a wafer on which at least one antenna element is formed (antenna element wafer) and a chip obtained by cutting the antenna element wafer.
  • the inorganic material substrate 2 has an upper surface on which the first conductor layer 1 is provided, and a lower surface located within the antenna element 100.
  • the thickness t of the inorganic material substrate 2 satisfies the above formula (1).
  • a preferably represents a numerical value of 6 or more.
  • the thickness of the inorganic material substrate 2 is, for example, 1 ⁇ m or more, preferably 2 ⁇ m or more, more preferably 10 ⁇ m or more, even more preferably 20 ⁇ m or more, particularly preferably 30 ⁇ m or more, and particularly preferably 40 ⁇ m or more. If the thickness of the inorganic material substrate 2 falls below such a lower limit, the thickness and size of the electrodes constituting the transmission line 12 will be reduced to about several ⁇ m, making it difficult to achieve impedance matching with the patch antenna 11. In addition, the tolerance of the transmission performance due to manufacturing variations may be significantly reduced.
  • the thickness of the inorganic material substrate 2 is, for example, 500 ⁇ m or less, preferably 200 ⁇ m or less, more preferably 100 ⁇ m or less, further preferably 80 ⁇ m or less, and particularly preferably 60 ⁇ m or less.
  • the thickness of the inorganic material substrate 2 is equal to or less than such an upper limit, it is possible to stably suppress induction of a slab mode and/or resonance of the inorganic material substrate 2. This makes it possible to further reduce the reflection loss when the antenna element 100 transmits and/or receives electromagnetic waves. As a result, it is possible to expand the bandwidth (typically, ⁇ 10 dB bandwidth) of electromagnetic waves for which the reflection characteristics of the antenna element 100 are sufficiently small, and it is possible to further widen the bandwidth of the antenna element 100.
  • the relative dielectric constant ⁇ of the inorganic material substrate 2 at 300 GHz is, for example, 12.0 or less, preferably 10.0 or less, and more preferably 5.0 or less.
  • the lower limit of the relative dielectric constant ⁇ of the inorganic material substrate 2 at 300 GHz is typically 3.5.
  • the dielectric tangent (dielectric loss) tan ⁇ of the inorganic material substrate 2 at 300 GHz is, for example, 0.0030 or less, preferably 0.0020 or less, and more preferably 0.0015 or less.
  • the dielectric constant ⁇ and the dielectric loss tangent (dielectric loss) tan ⁇ can be measured by, for example, terahertz time domain spectroscopy.
  • the dielectric constant and the dielectric loss tangent at 300 GHz are meant.
  • the inorganic material substrate 2 is made of an inorganic material. Any suitable material may be used as the inorganic material as long as the effect of the embodiment of the present invention can be obtained.
  • suitable material may be used as the inorganic material as long as the effect of the embodiment of the present invention can be obtained.
  • inorganic materials constituting the inorganic material substrate 2 include single crystal quartz (relative dielectric constant 4.5, dielectric loss tangent 0.0013), amorphous quartz (quartz glass, relative dielectric constant 3.8, dielectric loss tangent 0.0010), spinel (relative dielectric constant 8.3, dielectric loss tangent 0.0020), AlN (relative dielectric constant 8.5, dielectric loss tangent 0.0015), sapphire (relative dielectric constant 9.4, dielectric loss tangent 0.0030), SiC (relative dielectric constant 9.8, dielectric loss tangent 0.0022), magnesium oxide (relative dielectric constant 10.0, dielectric loss tangent 0.0012), and silicon (relative di
  • amorphous quartz quartz glass
  • the reflection loss in the antenna element 100 can be further stably reduced.
  • 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, it is advantageous in terms of reducing delay.
  • the first conductor layer 1 metal layer can be formed without roughening or surface treatment.
  • the inorganic material substrate 2 may be curved so that the portion that overlaps with the cavity 5 when viewed in the thickness direction sinks into the cavity 5.
  • the first conductor layer 1 is provided on the surface (one surface in the thickness direction) of the inorganic material substrate 2 and is in direct contact with the inorganic material substrate 2 .
  • the first conductor layer 1 is typically made of a metal. Examples of metals include chromium (Cr), nickel (Ni), copper (Cu), and gold (Au). The metals may be used alone or in combination.
  • the first conductor layer 1 may be a single layer, or may be formed by laminating two or more layers.
  • the thickness of the first conductor layer 1 is, for example, 1 ⁇ m to 20 ⁇ m, and preferably 4 ⁇ m to 10 ⁇ m.
  • the support substrate 3 can provide excellent strength to the antenna element 100.
  • the support substrate 3 supports the inorganic material substrate 2 via the first ground layer 42 and a joint 6 (described later). This allows the inorganic material substrate 2 to be thinned as described above.
  • the support substrate 3 has any appropriate configuration.
  • Examples of materials that can be used to form the support substrate 3 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, crystal, gallium nitride (GaN), silicon carbide (SiC), silicon nitride ( Si3N4 ), and gallium oxide ( Ga2O3 ).
  • InP indium phosphide
  • Si silicon
  • glass sialon
  • Si3N4 - Al2O3 sialon
  • mullite 3Al2O3.2SiO2 , 2Al2O3.3SiO2
  • magnesium oxide MgO
  • the thermal conductivity of the material constituting the support substrate 3 is preferably 150 W/Km or more, and more preferably 200 W/Km or more.
  • an external device e.g., an amplifier
  • the inorganic material substrate 2 may be heated by the external device, and the heat of the inorganic material substrate 2 may adversely affect the external device.
  • the support substrate 3 functions as a heat sink and can smoothly dissipate the heat of the inorganic material substrate 2.
  • thermal conductivity approximately 160 W/Km
  • silicon carbide thermal conductivity: approximately 270 W/Km
  • aluminum nitride thermal conductivity: approximately 150 W/Km to 250 W/Km
  • the linear expansion coefficient of the material constituting the support substrate 3 is as close as possible to the linear expansion coefficient of the material constituting the inorganic material substrate 2.
  • the linear expansion coefficient of the material constituting the support substrate 3 is, for example, within a range of 50% to 150% of the linear expansion coefficient of the material constituting the inorganic material substrate 2. If the linear expansion coefficient of the material constituting the support substrate 3 is within this range, thermal deformation (typically, warping) of the antenna element 100 can be suppressed.
  • indium phosphide silicon, aluminum nitride, gallium nitride, silicon carbide, and silicon nitride are preferred, silicon, aluminum nitride, gallium nitride, silicon carbide, and silicon nitride are more preferred, and silicon is particularly preferred.
  • the support substrate 3 has a recess 31 corresponding to the cavity 5 .
  • the recess 31 is typically recessed downward (in a direction away from the inorganic material substrate 2) from the upper surface (surface on the inorganic material substrate 2 side) of the support substrate 3.
  • the recess 31 has a shape similar to the above-mentioned hollow portion 5 when viewed from the thickness direction of the inorganic material substrate 2.
  • the recess 31 has a substantially U-shape that opens toward the inorganic material substrate 2 on a cut surface obtained by cutting the support substrate 3 in the thickness direction.
  • the inner surface of the recess 31 includes a side surface and a bottom surface.
  • the side surface of the recess 31 extends in the thickness direction of the inorganic material substrate 2.
  • the extending direction of the side surface of the recess 31 may be completely the same (i.e., parallel) as the thickness direction of the inorganic material substrate 2, or may be slightly inclined with respect to the thickness direction of the inorganic material substrate 2.
  • the bottom surface of the recess 31 extends in a direction intersecting (typically perpendicular) the thickness direction of the inorganic material substrate 2.
  • the antenna element 100 further includes a second conductor layer 4 including a ground conductor layer 41.
  • the second conductor layer 4 is disposed between the inorganic material substrate 2 and the support substrate 3.
  • the second conductor layer 4 is typically provided on the upper surface of the support substrate 3 (the surface on the inorganic material substrate 2 side) and is in direct contact with the support substrate 3.
  • the ground conductor layer 41 included in the second conductor layer 4 is located within the recess 31 of the support substrate 3.
  • the ground conductor layer 41 is provided on at least the bottom surface of the recess 31.
  • the ground conductor layer 41 is provided on the entire inner surface of the recess 31. Therefore, at least a portion of the ground conductor layer 41 is disposed opposite the patch antenna 11 in the thickness direction of the inorganic material substrate 2. Therefore, an electric field can be stably generated between the patch antenna 11 and the ground conductor layer 41.
  • the second conductor layer 4 further includes a first ground layer 42.
  • the first ground layer 42 may be provided at any appropriate location as long as it overlaps at least a portion of the projection surface of the transmission line 12 as described above.
  • the first ground layer 42 is provided on a portion of the upper surface of the support substrate 3 (the surface on the inorganic material substrate 2 side) other than the recess 31.
  • the first ground layer 42 may be provided partially on the upper surface of the support substrate 3 excluding the recess 31 (see FIG. 7), or may be provided on the entire upper surface of the support substrate 3 excluding the recess 31 (see FIG. 8).
  • the first ground layer 42 is provided over the entire top surface of the support substrate 3 except for the recess 31.
  • the first ground layer 42 and the ground conductor layer 41 are continuous with each other. If the ground conductor layer 41 and the first ground layer 42 are continuous with each other to form the second conductor layer 4, the ground function is stable across the entire substrate, and the design and manufacture of the antenna element 100 can be facilitated.
  • the second conductor layer 4 is made of, for example, the same metal as the first conductor layer 1 .
  • the thickness of the second conductor layer 4 is typically smaller than the thickness of the first conductor layer 1.
  • the thickness of the second conductor layer 4 is, for example, 1 nm to 30 ⁇ m, and preferably 10 nm to 10 ⁇ m.
  • the antenna element 100 further includes a joint 6.
  • the joint 6 joins the inorganic material substrate 2 and the support substrate 3.
  • the joint 6 joins the inorganic material substrate 2 and the support substrate 3 on which the first ground layer 42 is provided, and is located between the inorganic material substrate 2 and the first ground layer 42.
  • the joint 6 may be made of an organic material (typically an organic adhesive) or an inorganic material.
  • the inorganic material substrate 2 and the support substrate 3 on which the first ground layer 42 is formed are directly bonded.
  • a joint 6 is formed between the inorganic material substrate 2 and the first ground layer 42.
  • direct bonding means that two layers or substrates are bonded without the intermediation of an organic material (typically an organic adhesive).
  • the form of direct bonding can be appropriately set according to the configuration of the layers or substrates to be bonded to each other.
  • the interface bonded by direct bonding is typically amorphous. Therefore, it is possible to dramatically reduce the thermal resistance of the bonding interface compared to resin bonding.
  • the inorganic material substrate 2 can efficiently dissipate heat, and deterioration of the characteristics of the external device can be suppressed. Furthermore, by integrating them by direct bonding, peeling of the antenna element 100 can be effectively suppressed, and as a result, damage (e.g., cracks) to the inorganic material substrate 2 caused by such peeling can be effectively suppressed. In addition, by directly bonding them together without using resin, the heat resistance and chemical resistance in later manufacturing processes can be improved, and deterioration of the antenna characteristics of the antenna element 100 due to heat and moisture absorption can be suppressed.
  • the joint 6 may have a single-layer structure or a laminated structure. As shown in FIG. 2, in one embodiment, the joint 6 has a laminated structure.
  • the joint 6 includes a first bonding layer 61 and a second bonding layer 62.
  • the first bonding layer 61 is provided on the surface of the inorganic material substrate 2. More specifically, the first bonding layer 61 is provided on the surface of the inorganic material substrate 2 opposite to the first conductor layer 1 in the thickness direction of the inorganic material substrate 2. In the illustrated example, the first bonding layer 61 is provided on the lower surface of the inorganic material substrate 2 (the surface opposite to the first conductor layer 1) and is in direct contact with the inorganic material substrate 2. The first bonding layer 61 may be provided partially on the lower surface of the inorganic material substrate 2, or may be provided on the entire lower surface of the inorganic material substrate 2. In the illustrated example, the first bonding layer 61 is provided on the entire lower surface of the inorganic material substrate 2. The thickness of the first bonding layer 61 is, for example, 0.5 nm to 5 ⁇ m, preferably 0.01 ⁇ m to 1.5 ⁇ m, and more preferably 0.01 ⁇ m to 0.05 ⁇ m.
  • the second bonding layer 62 is provided on the surface of the first ground layer 42. More specifically, the second bonding layer 62 is provided on the surface of the first ground layer 42 opposite the support substrate 3 in the thickness direction of the inorganic material substrate 2. In the illustrated example, the second bonding layer 62 is provided on the upper surface (the surface opposite the support substrate 3) of the first ground layer 42 and is in direct contact with the first ground layer 42. The second bonding layer 62 may be provided only on the first ground layer 42, or may be provided on the ground conductor layer 41 in addition to the first ground layer 42. In the illustrated example, the second bonding layer 62 is provided on the entire upper surfaces of the ground conductor layer 41 and the first ground layer 42.
  • the second bonding layer 62 is laminated over the entire second conductor layer 4.
  • the range of the thickness of the second bonding layer 62 is, for example, the same as the range of the thickness of the first bonding layer 61 described above.
  • the second bonding layer 62 is bonded to the first bonding layer 61 and is integrated with the first bonding layer 61. In the illustrated example, a portion of the second bonding layer 62 located on the first ground layer 42 is directly bonded to the first bonding layer 61.
  • the second conductor layer 4 may be composed of only the ground conductor layer 41, without including the first ground layer 42.
  • the joint 6 is located between the part of the upper surface of the support substrate 3 other than the recess 31 and the inorganic material substrate 2, and joins them.
  • the cavity 5 is located inside the area surrounded by the inorganic material substrate 2 and the ground conductor layer 41.
  • the cavity 5 is a groove formed in the support substrate 3.
  • the cavity 5 is defined by a first bonding layer 61 provided on the lower surface of the inorganic material substrate 2 or on the lower surface of the inorganic material substrate 2, and a second bonding layer 62 provided on the upper surface of the ground conductor layer 41 or on the upper surface of the ground conductor layer 41.
  • the cavity 5 is defined by the first bonding layer 61 provided on the lower surface of the inorganic material substrate 2, and the second bonding layer 62 provided on the upper surface of the ground conductor layer 41.
  • Air is typically present in cavity 5.
  • cavity 5 is under vacuum.
  • the dimension d (hereinafter referred to as depth d) of the cavity 5 in the thickness direction of the inorganic material substrate 2 is changed arbitrarily and appropriately depending on the configuration of the antenna element 100 and the frequency of the electromagnetic waves transmitted and/or received by the antenna element 100.
  • the depth d of the cavity 5 is, for example, 1 ⁇ m to 250 ⁇ m.
  • the depth d of the cavity 5 refers to the distance between the lower surface of the inorganic material substrate 2 (the surface opposite to the first conductor layer 1) and the upper surface of the ground conductor layer 41 (the surface opposite to the support substrate 3) in the thickness direction of the inorganic material substrate 2.
  • the depth d of the cavity 5 is, for example, 5 ⁇ m to 250 ⁇ m. In another embodiment, when the patch antenna 11 has a rectangular shape and the antenna element 100 transmits and receives electromagnetic waves with a frequency of 250 GHz to 350 GHz, the depth d of the cavity 5 is, for example, 5 ⁇ m to 200 ⁇ m.
  • a support substrate 3 having a recess 31 is prepared.
  • the recess 31 is formed in the support substrate 3 by, for example, reactive ion etching.
  • the second conductor layer 4 is formed on the upper surface of the support substrate 3 on which the recess 31 is formed.
  • Any appropriate film formation method may be used as the film formation method. Examples of the film formation method include sputtering, plating, and vapor deposition, and plating is preferred.
  • the inorganic material substrate 2 is prepared, and the inorganic material substrate 2 and the support substrate 3 are directly bonded to each other. More specifically, a first bonding layer 61 is formed on the lower surface of the inorganic material substrate 2. A second bonding layer 62 is formed on the upper surface of the second conductor layer 4. Examples of the film formation method include sputtering, plating, and vapor deposition, and sputtering is preferred. The surfaces of the first bonding layer 61 and the second bonding layer 62 are planarized by polishing as necessary.
  • Direct bonding can be achieved, for example, by the following procedure.
  • a neutralizing beam is irradiated onto the respective bonding surfaces of the components (layers or substrates) to be bonded.
  • an inert gas is introduced into the chamber, and a high voltage is applied from a DC power source to an electrode disposed in the chamber.
  • a high voltage is applied from a DC power source to an electrode disposed in the chamber.
  • the ion beam is neutralized by the grid, and a beam of neutral atoms is emitted from the high-speed atom beam source.
  • the atomic species that constitute the beam is preferably an inert gas element (for example, argon (Ar), 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 irradiation time of the neutralizing beam is, for example, 10 to 300 seconds, and preferably 30 to 120 seconds. This activates the inorganic material present on each bonding surface, more specifically, on the beam irradiated surface.
  • the activated bonding surfaces are brought into contact with each other in a vacuum atmosphere at room temperature (23° C.).
  • the load during this contact may be, for example, 100 N to 20,000 N.
  • the first bonding layer 61 and the second bonding layer 62 are bonded together to form the bonded portion 6.
  • This provides a laminate having a structure of inorganic material substrate 2/joint portion 6/second conductor layer 4/support substrate 3.
  • 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.
  • the laminate is heat-treated as necessary. This can improve the bonding strength between the inorganic material substrate and the support substrate.
  • the heating temperature is, for example, 60° C. to 140° C., and preferably 80° C. to 120° C.
  • the heating time is, for example, 10 minutes to 5 hours, and preferably 30 minutes to 3 hours.
  • polishing chemical mechanical polishing
  • the first conductor layer 1 is formed on the upper surface of the inorganic material substrate 2.
  • a resist having an opening corresponding to the first conductor layer is formed on the upper surface of the inorganic material substrate 2, and then the first conductor layer is formed through the resist.
  • methods for forming the metal film include sputtering, plating, and vapor deposition, and preferably plating. In this manner, the antenna element 100 having the structure of the first conductor layer 1 /inorganic material substrate 2 /joint 6 /second conductor layer 4 /support substrate 3 and including the cavity 5 is manufactured.
  • Such an antenna element 100 may be applied to any suitable optical device (e.g., a waveguide element, an electromagnetic wave sensor).
  • the antenna element 100 has a wide band of available electromagnetic waves, and therefore may be suitably used in a human presence sensor that requires excellent resolution.
  • human presence sensors include gesture detection sensors for use in vehicles and gesture detection sensors for human machine interfaces (HMIs).
  • Example 1 A quartz glass wafer (inorganic material substrate) with a thickness of 0.5 mm was prepared. An amorphous silicon film (first bonding layer) with a thickness of 0.02 ⁇ m was formed on the surface of the inorganic material substrate by sputtering. After the film formation, the first bonding layer was polished and flattened. Here, the arithmetic mean roughness of the surface of the first bonding layer over a square of 10 ⁇ m was measured using an atomic force microscope and found to be 0.2 nm.
  • a silicon wafer (support substrate) with a thickness of 250 ⁇ m was also prepared.
  • a recess was formed on the upper surface of the support substrate by reactive ion etching.
  • the recess had a roughly rectangular shape when viewed in the thickness direction of the support substrate.
  • the dimension of the recess in the long side direction was 1100 ⁇ m
  • the dimension of the recess in the short side direction was 720 ⁇ m
  • the depth of the recess was 175 ⁇ m.
  • a gold film (second conductor layer) having a thickness of 1 ⁇ m was formed by sputtering on the top surface of the support substrate with the recess formed therein.
  • the second conductor layer integrally included a ground conductor layer located within the recess and a first ground layer located on the portion of the top surface of the support substrate other than the recess.
  • a 0.02 ⁇ m amorphous silicon film (second bonding layer) was formed on the second conductor layer by sputtering. After the film formation, the second bonding layer was polished and flattened.
  • the arithmetic mean roughness of the surface of the second bonding layer over a 10 ⁇ m square was measured using an atomic force microscope and found to be 0.2 nm.
  • the inorganic material substrate and the support substrate were directly bonded as follows. First, the inorganic material substrate on which the first bonding layer was formed and the support substrate on which the second bonding layer and the second conductor layer were formed were put into a vacuum chamber, and in a vacuum of 10 ⁇ 6 Pa, both bonding surfaces (the surfaces of the first bonding layer and the second bonding layer) were irradiated with a high-speed Ar neutral atom beam (accelerating voltage 1 kV, Ar flow rate 60 sccm) for 70 seconds.
  • a high-speed Ar neutral atom beam accelerating voltage 1 kV, Ar flow rate 60 sccm
  • the inorganic material substrate and the support substrate were left for 10 minutes to cool, and then the surfaces (beam irradiated surfaces) of the first bonding layer and the second bonding layer were brought into contact with each other, and the inorganic material substrate and the support substrate were bonded by applying pressure of 4.90 kN for 2 minutes. That is, the inorganic material substrate and the support substrate were directly bonded via the bonding portion and the second conductor layer. After bonding, the inorganic material substrate was polished until the thickness of the inorganic material substrate was 50 ⁇ m.
  • a resist was applied to the surface (polished surface) of the inorganic material substrate opposite to the bonding portion, and patterned by photolithography so as to expose the portion on which the first conductor layer was to be formed.
  • a copper film (first conductor layer) having a thickness of 5 ⁇ m was formed by sputtering on the upper surface of the inorganic material substrate exposed from the resist.
  • the resist was removed.
  • the first conductor layer included a patch antenna and an MS type signal wiring.
  • the patch antenna had a substantially rectangular shape when viewed from the thickness direction of the inorganic material substrate. The length of the patch antenna (direction perpendicular to the II-II' direction in FIG.
  • the MS type signal wiring was composed of a wide portion and a narrow portion, and the line width of each was set so that the impedance could be matched to 50 ⁇ .
  • the antenna element shown in FIG. 1 was obtained, that is, an antenna element having a configuration of the first conductor layer/inorganic material substrate/joint/second conductor layer/support substrate.
  • the antenna element had a cavity corresponding to the recess.
  • the entire projection surface of the patch antenna overlapped with the cavity.
  • the projection surface of the patch antenna was 507400 ⁇ m2
  • the projection area of the cavity was 792000 ⁇ m2 .
  • ⁇ Measurement of S11 parameters The antenna elements obtained in the examples and comparative examples were measured for the S11 parameter, which represents the return loss, using a network analyzer with a sampling frequency set to 120 GHz. The results are shown in Figs. 10 and 11. As is clear from Fig. 10, when the antenna element has a cavity, the bandwidth of the electromagnetic wave where the S11 parameter of the antenna element is -10 dB or less (-10 dB bandwidth) is 10.2 GHz. On the other hand, as shown in Fig. 11, in the antenna element without a cavity, the -10 dB bandwidth is 4.9 GHz. Therefore, it can be seen that the antenna element can be made wider bandwidth by having a cavity.
  • Antenna elements according to embodiments of the present invention can be used in a wide range of fields, such as next-generation high-speed communications and sensors, and are particularly suitable for use as human presence sensors.

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PCT/JP2023/033878 2023-09-19 2023-09-19 アンテナ素子 Pending WO2025062479A1 (ja)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62203404A (ja) * 1986-03-04 1987-09-08 Nippon Hoso Kyokai <Nhk> マイクロストリツプアンテナ
JPH01135105A (ja) * 1987-11-20 1989-05-26 Fujitsu Ltd パッチアンテナ
JP2020162120A (ja) * 2019-03-23 2020-10-01 京セラ株式会社 アンテナ基板およびアンテナモジュール

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62203404A (ja) * 1986-03-04 1987-09-08 Nippon Hoso Kyokai <Nhk> マイクロストリツプアンテナ
JPH01135105A (ja) * 1987-11-20 1989-05-26 Fujitsu Ltd パッチアンテナ
JP2020162120A (ja) * 2019-03-23 2020-10-01 京セラ株式会社 アンテナ基板およびアンテナモジュール

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