Terahertz device

Abstract

A terahertz device according to the present invention comprises: a semiconductor substrate that has a substrate front surface and a substrate back surface which is located on the opposite side from the substrate front surface; an active element that is provided on the substrate front surface and that oscillates or detects electromagnetic waves; an insulation substrate that is disposed to the substrate back surface side of the semiconductor substrate and that supports the semiconductor substrate; and a metal layer that is disposed between the semiconductor substrate and the insulation substrate and that is in contact with the substrate back surface. The semiconductor substrate has a thickness less than the wavelength of the electromagnetic waves.

Description

Terahertz Device

[0001] The present disclosure relates to terahertz devices.

[0002] In recent years, as electronic devices such as transistors have become increasingly miniaturized and their size has reached nanoscale, a phenomenon known as the quantum effect has become observable. Development is underway to utilize this quantum effect to realize ultrafast devices and devices with new functions.

[0003] In such an environment, attempts are being made to utilize electromagnetic waves in a frequency range called the terahertz band, which has a frequency of 0.1 THz to 10 THz, to perform high-capacity communication, information processing, imaging, measurement, etc. This frequency range combines the properties of both light and radio waves, and if devices operating in this frequency band are realized, they could be used for many applications, including the aforementioned imaging, high-capacity communication, and information processing, as well as measurements in various fields such as physical properties, astronomy, and biology.

[0004] As an element for emitting or receiving electromagnetic waves in the terahertz band, for example, a terahertz device having a structure in which a resonant tunneling diode and a fine slot antenna are integrated is known (see, for example, Patent Document 1).

[0005] Japanese Patent Application Laid-Open No. 2020-115500

[0006] However, when electromagnetic waves propagate through components arranged around the resonant tunneling diode of a terahertz device, there is a risk that electromagnetic waves of a frequency different from the desired frequency will be generated.

[0007] A terahertz device according to one aspect of the present disclosure includes a semiconductor substrate having a substrate surface and a substrate back surface opposite the substrate surface, an active element provided on the substrate surface for oscillating or detecting electromagnetic waves, an insulating substrate disposed on the substrate back surface side of the semiconductor substrate and supporting the semiconductor substrate, and a metal layer disposed between the semiconductor substrate and the insulating substrate and in contact with the substrate back surface, wherein the semiconductor substrate has a thickness less than the wavelength of the electromagnetic waves.

[0008] The terahertz device of the present disclosure can suppress the generation of electromagnetic waves with frequencies different from the electromagnetic waves with a desired frequency.

[0009] FIG. 1 is a schematic perspective view of a terahertz device according to one embodiment. FIG. 2 is a schematic side view of the terahertz device of FIG. 1. FIG. 3 is a schematic plan view of an active element and its periphery in the terahertz device of FIG. 1. FIG. 4 is a schematic cross-sectional view of the terahertz device of FIG. 3 taken along line F4-F4. FIG. 5 is a schematic cross-sectional view of the terahertz device of FIG. 3 taken along line F5-F5. FIG. 6 is a schematic cross-sectional view of an enlarged active element and its periphery in the terahertz device of FIG. 5. FIG. 7 is a schematic circuit diagram showing the circuit configuration of the terahertz device of FIG. 1. FIG. 8 is a schematic cross-sectional view showing a manufacturing process of the terahertz device. FIG. 9 is a schematic cross-sectional view showing a manufacturing process subsequent to that shown in FIG. 8. FIG. 10 is a schematic cross-sectional view showing a manufacturing process subsequent to that shown in FIG. 9. FIG. 11 is a schematic cross-sectional view showing a manufacturing process subsequent to that shown in FIG. 10. FIG. 12 is a schematic cross-sectional view showing a manufacturing process subsequent to that shown in FIG. 11. FIG. 13 is a schematic cross-sectional view of a terahertz unit according to a first application example of the terahertz device. Fig. 14 is a schematic cross-sectional view of a terahertz unit of a second application example of the terahertz device. Fig. 15 is a schematic plan view of a terahertz unit of a third application example of the terahertz device. Fig. 16 is a schematic cross-sectional view of a terahertz device of a modified example. Fig. 17 is a schematic cross-sectional view of a terahertz device of a modified example. Fig. 18 is a schematic cross-sectional view of a terahertz device of a modified example. Fig. 19 is a schematic cross-sectional view of a terahertz device of a modified example. Fig. 20 is a schematic side view of a terahertz device of a modified example.

[0010] Hereinafter, embodiments of a terahertz device according to the present disclosure will be described with reference to the accompanying drawings. For simplicity and clarity of description, the components shown in the drawings are not necessarily drawn to scale. Furthermore, cross-sectional views may omit hatching lines for ease of understanding. The accompanying drawings merely illustrate embodiments of the present disclosure and should not be construed as limiting the present disclosure.

[0011] The following detailed description includes devices, systems, and methods embodying exemplary embodiments of the present disclosure. This detailed description is merely illustrative in nature and is not intended to limit the embodiments of the present disclosure or the application and uses of such embodiments.

[0012] (Schematic Configuration of Terahertz Device) A schematic configuration of a terahertz device 10 according to this embodiment will be described with reference to FIGS. 1 to 7 . The side view of the terahertz device 10 shown in FIG. 2 is a simplified view of the configuration of the terahertz device 10 for ease of explanation. Therefore, the thickness relationships of the components in the side view of the terahertz device 10 shown in FIG. 2 differ from those in the perspective view of the terahertz device 10 shown in FIG. 1 . FIG. 3 is an enlarged plan view of a semiconductor element 20 (described later) and its periphery in the terahertz device 10. FIG. 4 shows the cross-sectional structure of a capacitor 91 (described later) in the semiconductor element 20. FIG. 5 shows the cross-sectional structure of a semiconductor substrate 50 (described later) and its periphery in the semiconductor element 20. FIG. 6 shows the cross-sectional structure of an active element 60 (described later) and its periphery in FIG. 5 for ease of explanation. An insulating layer 53 (described later) is omitted from FIG. 6 for ease of explanation.

[0013] 1, the terahertz device 10 is formed in a rectangular parallelepiped shape. The terahertz device 10 includes a device front surface 11, a device back surface 12 opposite the device front surface 11, and device side surfaces 13 to 16 extending between the device front surface 11 and the device back surface 12. In this embodiment, the direction perpendicular to the device front surface 11 is referred to as the "z direction." Two mutually perpendicular directions perpendicular to the z direction are referred to as the "x direction" and the "y direction," respectively.

[0014] Device side surface 13 and device side surface 14 are spaced apart from each other in the x direction. Both device side surface 13 and device side surface 14 extend along the yz plane. Device side surface 15 and device side surface 16 are spaced apart from each other in the y direction. Both device side surface 15 and device side surface 16 extend along the xz plane.

[0015] As shown in FIG. 2 , the terahertz device 10 includes a semiconductor element 20, an insulating substrate 30 serving as a support substrate for supporting the semiconductor element 20, and a metal layer 40 disposed between the semiconductor element 20 and the insulating substrate 30.

[0016] The semiconductor element 20 is an element that converts electromagnetic waves into electrical energy. Note that electromagnetic waves include the concepts of either light or radio waves, or both. The semiconductor element 20 is a functional device that oscillates and emits electromagnetic waves in a predetermined frequency band, for example, the terahertz band (terahertz waves). For example, the semiconductor element 20 can be said to be a terahertz element that oscillates and emits terahertz waves. Furthermore, for example, the semiconductor element 20 is a functional device that receives and detects electromagnetic waves in a predetermined frequency band, for example, the terahertz band (terahertz waves). For example, the semiconductor element 20 can be said to be a terahertz element that receives and detects terahertz waves. Here, the frequency band of terahertz waves is, for example, 0.1 THz or more and 10 THz or less.

[0017] The semiconductor element 20 converts the supplied electrical energy into electromagnetic waves by oscillating with the supplied electrical energy. As a result, the semiconductor element 20 emits electromagnetic waves in a desired frequency band. The semiconductor element 20 also receives electromagnetic waves and converts the electromagnetic waves into electrical energy. As a result, the semiconductor element 20 detects electromagnetic waves in a desired frequency band.

[0018] The semiconductor element 20 is formed in a flat plate shape. The shape of the semiconductor element 20 when viewed from the z direction is rectangular. Note that the shape of the semiconductor element 20 when viewed from the z direction is not limited to a rectangular shape, and may be a circular shape, an elliptical shape, or a polygonal shape.

[0019] The semiconductor element 20 includes a semiconductor substrate 50. The semiconductor substrate 50 is formed in a flat plate shape. The semiconductor substrate 50 is supported by an insulating substrate 30. The shape of the semiconductor substrate 50 when viewed from the z direction is rectangular. Note that the shape of the semiconductor substrate 50 when viewed from the z direction is not limited to a rectangular shape, and may be a circular shape, an elliptical shape, or a polygonal shape. The semiconductor substrate 50 may be made of any of a variety of materials, including InP (indium phosphide), GaAs (gallium arsenide), AlGaAs (aluminum gallium arsenide), InGaAs (indium gallium arsenide), InGaAsP (indium gallium arsenide phosphide), Si (silicon), SiC (silicon carbide), GaN (gallium nitride), GaN ２ In this embodiment, the semiconductor substrate 50 is made of a material containing InP.

[0020] The semiconductor substrate 50 includes a substrate surface 51 and a substrate back surface 52 opposite to the substrate surface 51. The substrate surface 51 faces the same side as the device surface 11, and the substrate back surface 52 faces the same side as the device back surface 12. The detailed configuration of the semiconductor element 20 will be described later. The substrate surface 51 constitutes the device surface 11 of the terahertz device 10.

[0021] 2 , the insulating substrate 30 is disposed on the substrate back surface 52 side of the semiconductor substrate 50. The insulating substrate 30 has a front surface 31 and a back surface 32 opposite the front surface 31. The front surface 31 faces the same side as the device front surface 11, and the back surface 32 faces the same side as the device back surface 12. The back surface 32 constitutes the device back surface 12 of the terahertz device 10.

[0022] The insulating substrate 30 has a rectangular shape when viewed from the z direction. In this embodiment, the dimensions in the x direction and the y direction of the surface 31 of the insulating substrate 30 are equal to the dimensions in the x direction and the y direction of the semiconductor substrate 50. In other words, the side surfaces of the insulating substrate 30 and the semiconductor substrate 50 are flush with each other.

[0023] The metal layer 40 is in contact with the rear surface 52 of the semiconductor substrate 50. The metal layer 40 is in contact with the front surface 31 of the insulating substrate 30. In this embodiment, the metal layer 40 is formed over the entire rear surface 52 of the semiconductor substrate 50. The metal layer 40 is formed over the entire front surface 31 of the insulating substrate 30. The metal layer 40 is a bonding layer that bonds the semiconductor substrate 50 and the insulating substrate 30 together. In other words, it can be said that the semiconductor substrate 50 and the insulating substrate 30 are bonded together by the metal layer 40. In this embodiment, the metal layer 40 is electrically insulated from the semiconductor element 20. The metal layer 40 is in an electrically floating state.

[0024] The metal layer 40 is configured with a stacked structure of multiple metal layers. In this embodiment, the metal layer 40 includes a first metal layer 41 and a second metal layer 42. The first metal layer 41 is provided on the insulating substrate 30. The second metal layer 42 is provided on the rear surface 52 of the semiconductor substrate 50. Therefore, the second metal layer 42 is provided on the first metal layer 41. The first metal layer 41 and the second metal layer 42 are formed by, for example, sputtering.

[0025] The first metal layer 41 includes a first metal film 41A provided on the front surface 31 of the insulating substrate 30 and a second metal film 41B provided on the first metal film 41A. The second metal layer 42 includes a third metal film 42A provided on the rear surface 52 of the semiconductor substrate 50 and a fourth metal film 42B provided on the third metal film 42A. The fourth metal film 42B is in contact with the second metal film 41B.

[0026] Each of the first metal film 41A, the second metal film 41B, the third metal film 42A, and the fourth metal film 42B is formed of a material containing at least one selected from the group consisting of titanium (Ti), titanium nitride (TiN), gold (Au), silver (Ag), copper (Cu), aluminum (Al), and platinum (Pt). In this embodiment, both the first metal film 41A and the third metal film 42A are formed of a material containing Ti. Both the second metal film 41B and the fourth metal film 42B are formed of a material containing Au.

[0027] (Detailed Structure of Semiconductor Element) The detailed structure of the semiconductor element 20 will be described. As shown in FIG. 1, the semiconductor element 20 includes an insulating layer 53 provided on a substrate surface 51 of a semiconductor substrate 50. The insulating layer 53 is disposed in the center of the substrate surface 51 in the x and y directions. When viewed from the z direction, the insulating layer 53 has a rectangular shape. The insulating layer 53 is made of, for example, SiO ２ The material is formed from a material containing

[0028] 1 and 3, the semiconductor device 20 includes an active device 60, a first electrode 70, and a second electrode 80 disposed on a substrate surface 51. The first electrode 70 and the second electrode 80 include an antenna structure 90.

[0029] The active element 60 exchanges electromagnetic waves of a predetermined frequency band with electrical energy. The active element 60 is provided, for example, at the center of the substrate surface 51 in the x and y directions. The active element 60 converts supplied electrical energy into electromagnetic waves by connecting to the antenna structure 90. This causes the semiconductor element 20 to emit electromagnetic waves of a predetermined frequency band. Therefore, as shown in FIG. 3 , the active element 60 can be referred to as an oscillation point P1 that oscillates electromagnetic waves, and the antenna structure 90 can be referred to as a radiation point P2 that radiates electromagnetic waves. In this embodiment, the semiconductor element 20 has the radiation point P2 and the oscillation point P1 at the same position. Note that the position of the oscillation point P1 is not limited to the same position as the radiation point P2 and can be changed as desired. The position of the oscillation point P1 can be any position on the substrate surface 51.

[0030] The active element 60 is, for example, a resonant tunneling diode (RTD). The active element 60 may also be, for example, a tunnel injection transit time (TUNNETT) diode, an impact ionization avalanche transit time (IMPATT) diode, a GaAs-based field effect transistor (FET), a GaN-based FET, a high electron mobility transistor (HEMT), or a heterojunction bipolar transistor (HBT).

[0031] An example of a configuration for realizing the active element 60 will be described. As shown in Fig. 5 , the active element 60 is provided between a first conductive portion 71 of a first electrode 70 and the semiconductor substrate 50 in the z direction. The active element 60 is in contact with both the first conductive portion 71 and the substrate surface 51 of the semiconductor substrate 50. The first conductive portion 71 includes a connection portion 71a that overlaps with the active element 60 when viewed from the z direction. The active element 60 is also provided in an insulating layer 53.

[0032] 5 and 6, a semiconductor layer 61a is provided on the substrate surface 51 of the semiconductor substrate 50. As shown in FIG. 3, the semiconductor layer 61a has a rectangular shape when viewed from the z direction. The semiconductor layer 61a is made of, for example, GaInAs. The semiconductor layer 61a is heavily doped with n-type impurities.

[0033] 6, a GaInAs layer 62a is stacked on a semiconductor layer 61a. The GaInAs layer 62a is doped with n-type impurities. The n-type impurity concentration of the GaInAs layer 62a is lower than the n-type impurity concentration of the semiconductor layer 61a.

[0034] A GaInAs layer 63a is stacked on the GaInAs layer 62a. The GaInAs layer 63a is not doped with impurities. An AlAs layer 64a is stacked on the GaInAs layer 63a. An InGaAs layer 65 is stacked on the AlAs layer 64a. The InGaAs layer 65 is not doped with impurities. An AlAs layer 64b is stacked on the InGaAs layer 65. The AlAs layer 64a, the InGaAs layer 65, and the AlAs layer 64b form a resonant tunnel section.

[0035] An undoped GaInAs layer 63b is stacked on the AlAs layer 64b. An n-type doped GaInAs layer 62b is stacked on the GaInAs layer 63b. A highly doped GaInAs layer 61b is stacked on the GaInAs layer 62b. Therefore, the n-type impurity concentration of the GaInAs layer 61b is higher than the n-type impurity concentration of the GaInAs layer 62b. The connection portion 71a of the first conductive portion 71 is located on the GaInAs layer 61b and is in contact with the GaInAs layer 61b.

[0036] The specific configuration of the active element 60 can be changed as desired as long as it can generate (or detect, or both) electromagnetic waves. In other words, the active element 60 may be any element that can perform at least one of oscillation and detection of electromagnetic waves in the terahertz band.

[0037] 3 , the semiconductor element 20 includes a first conductive portion 71 and a second conductive portion 81 that function as an antenna structure 90. The first conductive portion 71 is formed integrally with the first electrode 70, and the second conductive portion 81 is formed integrally with the second electrode 80. In other words, the first conductive portion 71 is a part of the first electrode 70, and the second conductive portion 81 is a part of the second electrode 80.

[0038] The active element 60 is disposed between the first conductive portion 71 and the second conductive portion 81. The antenna structure 90 of this embodiment is a dipole antenna. The first conductive portion 71 and the second conductive portion 81 extend in opposite directions from the active element 60. The length of the antenna structure 90, i.e., the length from the tip of the first conductive portion 71 to the tip of the second conductive portion 81, is set to, for example, ½ wavelength (λ / 2) where λ is the wavelength of the electromagnetic waves emitted by the semiconductor element 20. Note that the antenna structure 90 is not limited to a dipole antenna, and may be other antenna structures such as a bowtie antenna, a slot antenna, a patch antenna, or a ring antenna. The length of the antenna structure 90 may be changed depending on the configuration of the antenna structure 90.

[0039] The first conductive portion 71 and the second conductive portion 81 are arranged on both sides of the active element 60 in the x-direction. Each of the first conductive portion 71 and the second conductive portion 81 extends in the x-direction. As shown in FIG. 5 , the connection portion 71 a of the first conductive portion 71 is provided on the insulating layer 53. The second conductive portion 81 is provided in an opening 53A of the insulating layer 53. The second conductive portion 81 is provided on the substrate surface 51 of the semiconductor substrate 50.

[0040] 3 , the first electrode 70 includes a first wiring portion 72 connected to the first conductive portion 71, a first electrode plate 73 connected to the first wiring portion 72, and a first electrode pad 74 connected to the first electrode plate 73. The first conductive portion 71, the first wiring portion 72, and the first electrode plate 73 are provided at positions overlapping the insulating layer 53 when viewed from the z direction. The first electrode pad 74 is disposed closer to the device side surface 16 than the insulating layer 53.

[0041] The first wiring portion 72 is formed in a band shape extending along the y direction. The first electrode plate 73 has a rectangular shape when viewed from the z direction. The first electrode plate 73 is arranged in a position overlapping a portion of the second electrode 80 when viewed from the y direction. The first electrode pad 74 is arranged closer to the device side surface 14 (see FIG. 1 ) than the second electrode 80. The first electrode pad 74 has a rectangular shape when viewed from the z direction. The first electrode pad 74 is formed on the substrate surface 51 of the semiconductor substrate 50.

[0042] The second electrode 80 includes a second wiring portion 82 connected to the second conductive portion 81, a second electrode plate 83 connected to the second wiring portion 82, and a second electrode pad 84 connected to the second electrode plate 83. The second conductive portion 81, the second wiring portion 82, and the second electrode plate 83 are provided at positions overlapping the insulating layer 53 when viewed from the z direction. The second electrode pad 84 is disposed closer to the device side surface 16 than the insulating layer 53.

[0043] The second wiring portion 82 is formed in a band shape extending along the y direction. The second electrode plate 83 has a rectangular shape when viewed from the z direction. The second electrode plate 83 is arranged in a position overlapping a portion of the first electrode 70 when viewed from the y direction. The second electrode pad 84 is arranged closer to the device side surface 13 (see FIG. 1 ) than the first electrode 70. The second electrode pad 84 has a rectangular shape when viewed from the z direction. The second electrode pad 84 is formed on the substrate surface 51 of the semiconductor substrate 50. In this embodiment, the first electrode pad 74 constitutes a main electrode, and the second electrode pad 84 constitutes a ground electrode.

[0044] As shown in FIG. 4 , the second electrode plate 83 is provided on the substrate surface 51 of the semiconductor substrate 50. The second electrode plate 83 is covered with the insulating layer 53. The first electrode plate 73 is provided on the insulating layer 53. In this manner, the first electrode plate 73 and the second electrode plate 83 are disposed opposite each other in the z direction, sandwiching the insulating layer 53 therebetween. As a result, the semiconductor element 20 can be said to include an MIM (Metal Insulator Metal) capacitor (hereinafter, “capacitor 91”). The capacitor 91 short-circuits the first electrode 70 and the second electrode 80 at high frequencies. The capacitor 91 can reflect high-frequency electromagnetic waves and therefore functions as a low-pass filter. Note that the capacitor 91 may be omitted. That is, the first electrode plate 73 may be omitted from the first electrode 70, and the second electrode plate 83 may be omitted from the second electrode 80.

[0045] 3 , the second electrode plate 83 includes a protruding portion 83a that protrudes closer to the antenna structure 90 in the y direction than the first electrode plate 73. A contact portion 85 that connects the protruding portion 83a and the second wiring portion 82 is provided between the protruding portion 83a and the second wiring portion 82. This electrically connects the second electrode plate 83 and the second wiring portion 82.

[0046] Dimensional Relationships of the Terahertz Device The dimensional relationships of the terahertz device 10 will be described with reference to Fig. 2. The semiconductor substrate 50 has a thickness less than the wavelength λ of the electromagnetic wave oscillated by the semiconductor element 20. Here, the wavelength λ is the effective wavelength in the semiconductor substrate 50, and λ = λ _０ × (1 / √ε _ｒ ) can be defined as λ _０ is the wavelength in free space, and ε _ｒ is the relative dielectric constant of the semiconductor substrate 50. Here, the free space is a space in which no dielectric exists, such as a vacuum. In this embodiment, the semiconductor substrate 50 is made of InP. Therefore, the relative dielectric constant ε of the semiconductor substrate 50 is _ｒ is 12.47. The thickness of the semiconductor substrate 50 is defined as "thickness Ts1." The thickness Ts1 of the semiconductor substrate 50 can be defined as the distance between the substrate front surface 51 and the substrate back surface 52 in the z direction.

[0047] In one example, the thickness Ts1 of the semiconductor substrate 50 is equal to or less than ½ of the wavelength λ of the electromagnetic wave oscillated by the semiconductor element 20. In another example, the thickness Ts1 of the semiconductor substrate 50 is equal to or less than ⅓ of the wavelength λ of the electromagnetic wave oscillated by the semiconductor element 20. In this embodiment, the thickness Ts1 of the semiconductor substrate 50 is less than ¼ of the wavelength λ of the electromagnetic wave oscillated by the semiconductor element 20. In another example, the thickness Ts1 of the semiconductor substrate 50 is equal to or greater than ⅕ of the wavelength λ of the electromagnetic wave oscillated by the semiconductor element 20.

[0048] In this way, the thickness Ts1 of the semiconductor substrate 50 is set according to the wavelength λ of the electromagnetic waves oscillated by the semiconductor element 20. In other words, the thickness Ts1 of the semiconductor substrate 50 is set according to the frequency of the electromagnetic waves set for the semiconductor element 20. The thickness Ts1 of the semiconductor substrate 50 is set to become thinner as the frequency of the electromagnetic waves of the semiconductor element 20 increases. Below, a description will be given of the thickness Ts1 of the semiconductor substrate 50 when the frequency band of the electromagnetic waves is 0.1 THz (100 GHz) or more and 10 THz or less, which is the frequency band of terahertz waves.

[0049] The thickness Ts1 of the semiconductor substrate 50 is set to be less than the thickness at an electromagnetic wave frequency of 100 GHz. For example, when the frequency of the electromagnetic wave of the semiconductor element 20 is in the 100 GHz band (100 GHz or more and less than 200 GHz), the wavelength λ of the electromagnetic wave is _０ is 1500 μm or more and less than 3000 μm. As a result, the wavelength λ of the electromagnetic wave is 425 μm or more and less than 850 μm. In one example, the thickness Ts1 of the semiconductor element 20 is 425 μm or more and less than 850 μm, which corresponds to the wavelength λ of the electromagnetic wave. In one example, the thickness Ts1 of the semiconductor element 20 is 212.5 μm or more and 425 μm or less, which corresponds to ½ of the wavelength λ of the electromagnetic wave. In one example, the thickness Ts1 of the semiconductor element 20 is 141.7 μm or more and 283.3 μm or less, which corresponds to ⅓ of the wavelength λ of the electromagnetic wave. In one example, the thickness Ts1 of the semiconductor element 20 is 106.3 μm or more and less than 212.5 μm, which corresponds to ¼ of the wavelength λ of the electromagnetic wave. When the frequency of the electromagnetic waves of the semiconductor element 20 is in the 100 GHz band (100 GHz or more and less than 200 GHz), the thickness Ts1 of the semiconductor element 20 may be less than 106.3 μm.

[0050] For example, when the frequency of the electromagnetic wave of the semiconductor element 20 is in the 300 GHz band (300 GHz or more and less than 400 GHz), the wavelength λ of the electromagnetic wave is _０is equal to or greater than 750 μm and less than 1000 μm. As a result, the wavelength λ of the electromagnetic wave is equal to or greater than 212.4 μm and less than 283.2 μm. In one example, the thickness Ts1 of the semiconductor element 20 is equal to or greater than 212.4 μm and less than 283.2 μm, which corresponds to the wavelength λ of the electromagnetic wave. In one example, the thickness Ts1 of the semiconductor element 20 is equal to or greater than 106.2 μm and less than 141.6 μm, which corresponds to ½ of the wavelength λ of the electromagnetic wave. In one example, the thickness Ts1 of the semiconductor element 20 is equal to or greater than 70.8 μm and less than 94.4 μm, which corresponds to ⅓ of the wavelength λ of the electromagnetic wave. In one example, the thickness Ts1 of the semiconductor element 20 is equal to or greater than 53.1 μm and less than 70.8 μm, which corresponds to ¼ of the wavelength λ of the electromagnetic wave. When the frequency of the electromagnetic waves of the semiconductor element 20 is in the 300 GHz band (not less than 300 GHz and less than 400 GHz), the thickness Ts1 of the semiconductor element 20 may be less than 53.1 μm.

[0051] For example, when the frequency of the electromagnetic wave of the semiconductor element 20 is in the 500 GHz band (500 GHz or more and less than 600 GHz), the wavelength λ of the electromagnetic wave is _０ is 500 μm or more and less than 600 μm. As a result, the wavelength λ of the electromagnetic wave is 141.6 μm or more and less than 169.9 μm. In one example, the thickness Ts1 of the semiconductor element 20 is 141.6 μm or more and less than 169.9 μm, which corresponds to the wavelength λ of the electromagnetic wave. In one example, the thickness Ts1 of the semiconductor element 20 is 70.8 μm or more and 85 μm or less, which corresponds to ½ of the wavelength λ of the electromagnetic wave. In one example, the thickness Ts1 of the semiconductor element 20 is 47.2 μm or more and 56.6 μm or less, which corresponds to ⅓ of the wavelength λ of the electromagnetic wave. In one example, the thickness Ts1 of the semiconductor element 20 is 35.4 μm or more and 42.5 μm or less, which corresponds to ¼ of the wavelength λ of the electromagnetic wave. When the frequency of the electromagnetic waves of the semiconductor element 20 is in the 500 GHz band (500 GHz or more and less than 600 GHz), the thickness Ts1 of the semiconductor element 20 may be less than 35.4 μm.

[0052] For example, when the frequency of the electromagnetic wave of the semiconductor element 20 is 1 THz or more and 2 THz or less, the wavelength λ of the electromagnetic wave is _０is 150 μm or more and 300 μm or less. As a result, the wavelength λ of the electromagnetic wave is 42.5 μm or more and 85 μm or less. In one example, the thickness Ts1 of the semiconductor element 20 is 42.5 μm or more and 85 μm or less, which corresponds to the wavelength λ of the electromagnetic wave. In one example, the thickness Ts1 of the semiconductor element 20 is 21.3 μm or more and 42.5 μm or less, which corresponds to ½ of the wavelength λ of the electromagnetic wave. In one example, the thickness Ts1 of the semiconductor element 20 is 14.2 μm or more and 28.3 μm or less, which corresponds to ⅓ of the wavelength λ of the electromagnetic wave. In one example, the thickness Ts1 of the semiconductor element 20 is 10.6 μm or more and less than 21.3 μm, which corresponds to ¼ of the wavelength λ of the electromagnetic wave. Note that when the frequency of the electromagnetic wave of the semiconductor element 20 is 1 THz or more and 2 THz or less, the thickness Ts1 of the semiconductor element 20 may be less than 10.6 μm.

[0053] For example, when the frequency of the electromagnetic wave of the semiconductor element 20 is 10 THz, the wavelength λ of the electromagnetic wave _０ is 30 μm. As a result, the wavelength λ of the electromagnetic wave is 8.5 μm. In one example, the thickness Ts1 of the semiconductor substrate 50 is less than 8.5 μm, which corresponds to the wavelength λ of the electromagnetic wave. In one example, the thickness Ts1 of the semiconductor substrate 50 is 4.3 μm or less, which corresponds to ½ of the wavelength λ of the electromagnetic wave. In one example, the thickness Ts1 of the semiconductor substrate 50 is 2.8 μm or less, which corresponds to ⅓ of the wavelength λ of the electromagnetic wave. In one example, the thickness Ts1 of the semiconductor substrate 50 is 2.1 μm or less, which corresponds to ¼ of the wavelength λ of the electromagnetic wave.

[0054] The thickness Ts1 of the semiconductor substrate 50 is set according to the frequency of the electromagnetic waves of the semiconductor element 20 used, and by setting the thickness Ts1 of the semiconductor substrate 50 to, for example, 20 μm or more and 300 μm or less, it can be adapted to roughly the frequency of the electromagnetic waves used by the semiconductor element 20. In other words, if the frequency of the electromagnetic waves of the semiconductor element 20 is 100 GHz or more and 1 THz or less, the thickness Ts1 of the semiconductor substrate 50 should be set to 20 μm or more and 300 μm or less. If the frequency of the electromagnetic waves of the semiconductor element 20 is higher than 1 THz, the thickness Ts1 of the semiconductor substrate 50 should be set according to that frequency.

[0055] The insulating substrate 30 is made of AlN, SiC, alumina (Al ２ O ３), Si, and silicon oxide (SiO ２ ) The insulating substrate 30 has higher rigidity than the semiconductor substrate 50. For example, the thickness Ts2 of the insulating substrate 30 is thicker than the thickness Ts1 of the semiconductor substrate 50. Here, the thickness Ts2 of the insulating substrate 30 can be defined as the distance between the front surface 31 and the back surface 32 of the insulating substrate 30 in the z direction.

[0056] The insulating substrate 30 is made of AlN, SiC, or Al ２ O ３ When the insulating substrate 30 is formed of a material having a Young's modulus higher than that of the semiconductor substrate 50, such as a material having a Young's modulus higher than that of the semiconductor substrate 50, the thickness Ts2 of the insulating substrate 30 may be equal to or less than the thickness Ts1 of the semiconductor substrate 50, as long as the insulating substrate 30 has a higher rigidity than the semiconductor substrate 50.

[0057] The insulating substrate 30 is made of Si, SiO ２ When the insulating substrate 30 is formed of a material having a Young's modulus roughly equivalent to that of the semiconductor substrate 50, such as a material having a Young's modulus of 0.1 to 1.0 μm, the thickness Ts2 of the insulating substrate 30 is made thicker than the thickness Ts1 of the semiconductor substrate 50 so that the insulating substrate 30 has higher rigidity than the semiconductor substrate 50.

[0058] The thickness Ts1 of the semiconductor substrate 50 is greater than the thickness Tm of the metal layer 40. The thickness Tm of the metal layer 40 is, for example, not less than 10 nm and not more than 300 nm. The thickness Tm of the metal layer 40 can be defined, for example, by the distance in the z direction between the rear surface 52 of the semiconductor substrate 50 and the front surface 31 of the insulating substrate 30.

[0059] In this embodiment, the thickness Ts2 of the insulating substrate 30 is approximately 520 μm. Therefore, in this embodiment, the thickness Ts2 of the insulating substrate 30 is thicker than the thickness Ts1 of the semiconductor substrate 50 (20 μm or more and 300 μm or less).

[0060] (Circuit Configuration of Terahertz Device) The circuit configuration of the terahertz device 10 will be described with reference to FIG. 7 . In the terahertz device 10, a resonant tunneling diode RTD serving as an active element 60 is electrically connected by a first electrode 70 and a second electrode 80. More specifically, the resonant tunneling diode RTD is electrically connected via a first wiring portion 72 of the first electrode 70 and a second wiring portion 82 of the second electrode 80. An antenna structure 90 formed by the first conductive portion 71 of the first electrode 70 and the second conductive portion 81 of the second electrode 80 is electrically connected in parallel with the resonant tunneling diode RTD. A capacitor 91 formed by the first electrode plate 73 of the first electrode 70 and the second electrode plate 83 of the second electrode 80 is electrically connected in parallel with the resonant tunneling diode RTD.

[0061] The first wiring portion 72 includes an inductor L1 and a wiring resistance R1. The second wiring portion 82 includes an inductor L2 and a wiring resistance R2. The first wiring portion 72, the second wiring portion 82, and the capacitor 91 form an LC resonance circuit. The semiconductor element 20 oscillates electromagnetic waves through LC resonance.

[0062] (Method of Manufacturing Terahertz Device) An example of a method of manufacturing the terahertz device 10 will be described with reference to Figures 8 to 12. Each of Figures 8 to 12 is a schematic cross-sectional view showing an example of a manufacturing process for the terahertz device 10. Note that hatching lines are omitted in Figures 8 to 12 for the sake of convenience.

[0063] 8, the manufacturing method of the terahertz device 10 includes preparing a semiconductor substrate 850. The semiconductor substrate 850 is supported by a support substrate 900. The support substrate 900 is formed of, for example, sapphire. The semiconductor substrate 850 is a semiconductor wafer from which a plurality of semiconductor substrates 50 (see FIG. 2) can be manufactured, and is thicker than the thickness Ts1 (see FIG. 2) of the semiconductor substrate 50. The semiconductor substrate 850 is formed of, for example, a material containing InP.

[0064] The semiconductor substrate 850 has a substrate front surface 851 and a substrate back surface 852 opposite to the substrate front surface 851. The support substrate 900 is bonded to the substrate front surface 851. The substrate back surface 852 is exposed.

[0065] 9 , the manufacturing method for the terahertz device 10 includes grinding the semiconductor substrate 850 to reduce its thickness. By grinding the semiconductor substrate 850, the thickness of the semiconductor substrate 850 is made equal to the thickness Ts1 of the semiconductor substrate 50. In other words, the amount of grinding of the semiconductor substrate 850 is set according to the frequency of the electromagnetic waves of the semiconductor element 20. The amount of grinding of the semiconductor substrate 850 increases as the frequency of the electromagnetic waves of the semiconductor element 20 increases.

[0066] Grinding the semiconductor substrate 850 to reduce its thickness includes mirror-polishing the substrate rear surface 52. The mirror-polishing is performed by a known method such as chemical mechanical polishing (CMP). The substrate rear surface 52 is mirror-polished so that the arithmetic mean roughness Ra of the substrate rear surface 52 after mirror-polishing is 10 nm or less. The arithmetic mean roughness Ra of the substrate rear surface 52 may be 5 nm or less.

[0067] As shown in FIG. 10 , the manufacturing method for the terahertz device 10 includes forming a second metal layer 842 on a rear surface 852 of a semiconductor substrate 850. More specifically, a third metal film 842A is first formed on the rear surface 852 of the semiconductor substrate 850. Subsequently, a fourth metal film 842B is formed on the third metal film 842A. The third metal film 842A and the fourth metal film 842B are formed by, for example, sputtering. The third metal film 842A is formed of, for example, a material containing Ti. The fourth metal film 842B is formed of, for example, a material containing Au. The third metal film 842A and the fourth metal film 842B constitute the second metal layer 842. Note that in FIG. 10 , the thickness of the second metal layer 842 is thicker than the thickness of the semiconductor substrate 850 to clearly show the layered structure of the second metal layer 842; however, in reality, the thickness of the second metal layer 842 is thinner than the thickness of the semiconductor substrate 850.

[0068] 11 , the method for manufacturing the terahertz device 10 includes preparing an insulating substrate 830. The insulating substrate 830 is a substrate that enables the manufacturing of a plurality of insulating substrates 30, and has the same thickness as the thickness Ts2 of the insulating substrate 30. The insulating substrate 830 is formed of a material containing, for example, AlN.

[0069] The manufacturing method of the terahertz device 10 includes forming a first metal layer 841 on the surface 831 of the insulating substrate 830. More specifically, first, a first metal film 841A is formed on the surface 831 of the insulating substrate 830. Subsequently, a second metal film 841B is formed on the first metal film 841A. The first metal film 841A and the second metal film 841B are formed by, for example, sputtering. The first metal film 841A is formed of, for example, a material containing Ti. The second metal film 841B is formed of, for example, a material containing Au. The first metal film 841A and the second metal film 841B constitute the first metal layer 841.

[0070] 12 , the manufacturing method of the terahertz device 10 includes bonding a first metal layer 841 and a second metal layer 842. In one example, the first metal layer 841 and the second metal layer 842 are diffusion bonded. This forms the metal layer 840. The metal layer 840 serves as a bonding layer that bonds the semiconductor substrate 850 and the insulating substrate 830.

[0071] The method for manufacturing the terahertz device 10 includes removing the support substrate 900. For example, the support substrate 900 is removed from the semiconductor substrate 850 by grinding the support substrate 900.

[0072] Although not shown, the method of manufacturing the terahertz device 10 includes forming the insulating layer 53, the active element 60, the first electrode 70, and the second electrode 80 (all see FIG. 3) on the substrate surface 851 of the semiconductor substrate 850.

[0073] Although not shown, the manufacturing method of the terahertz device 10 includes singulation. More specifically, the semiconductor substrate 850, the metal layer 840, and the insulating substrate 830 are cut with a dicing blade. Through the above steps, the terahertz device 10 is manufactured.

[0074] (Operation) The operation of the terahertz device 10 of this embodiment will be described. The electromagnetic waves (terahertz waves) oscillated or detected by the active element 60 propagate through multiple paths around the active element 60, for example, between the first electrode 70 and the second electrode 80.

[0075] One of the propagation paths of the electromagnetic wave is a path that propagates within the semiconductor substrate 50. The electromagnetic wave propagates, for example, in the thickness direction of the semiconductor substrate 50. Here, for example, if the thickness Ts1 of the semiconductor substrate 50 is equal to or greater than the wavelength λ of the electromagnetic wave, a standing wave occurs within the semiconductor substrate 50. This standing wave causes a substrate mode of the semiconductor substrate 50. Then, due to the substrate mode of the semiconductor substrate 50, an electromagnetic wave of a frequency different from the electromagnetic wave of the desired frequency is generated in the terahertz device 10.

[0076] In this regard, in the terahertz device 10 of the present embodiment, the thickness Ts1 of the semiconductor substrate 50 is less than the wavelength λ of the electromagnetic wave, and therefore the electromagnetic wave propagating in the thickness direction of the semiconductor substrate 50 is blocked by the metal layer 40 before reaching the wavelength λ. This makes it possible to suppress the generation of standing waves within the semiconductor substrate 50. This makes it possible to suppress the generation of substrate modes in the semiconductor substrate 50. This makes it possible to suppress the generation of electromagnetic waves of frequencies different from electromagnetic waves of a desired frequency in the terahertz device 10.

[0077] In a terahertz device assumed not to include an insulating substrate 30, during manufacturing of the terahertz device, the semiconductor substrate 850, which is a semiconductor wafer constituting the semiconductor substrate 50, is ground to the thickness Ts1 of the semiconductor substrate 50, and then the support substrate 900 is removed to form the first electrode 70 and the like. Here, reducing the thickness Ts1 of the semiconductor substrate 850 reduces the rigidity of the semiconductor substrate 850. Therefore, if the semiconductor substrate 850 is transported alone after removing the support substrate 900, the semiconductor substrate 850 will deform due to its low rigidity. This may result in damage to the semiconductor substrate 850. Therefore, it is difficult to transport the semiconductor substrate 850 alone.

[0078] Therefore, in this embodiment, the insulating substrate 830 is bonded to the semiconductor substrate 850 via the metal layer 840. Since the semiconductor substrate 850 is reinforced by the insulating substrate 830, deformation of the semiconductor substrate 850 can be suppressed when the semiconductor substrate 850 is transported. Therefore, the semiconductor substrate 850 can be transported.

[0079] (Effects) The terahertz device 10 of this embodiment provides the following effects: (1) The terahertz device 10 includes a semiconductor substrate 50 having a substrate front surface 51 and a substrate back surface 52 opposite to the substrate front surface 51, an active element 60 provided on the substrate front surface 51 and configured to oscillate or detect electromagnetic waves, an insulating substrate 30 disposed on the substrate back surface 52 side of the semiconductor substrate 50 and supporting the semiconductor substrate, and a metal layer 40 disposed between the semiconductor substrate 50 and the insulating substrate 30 and in contact with the substrate back surface 52. The semiconductor substrate 50 has a thickness less than the wavelength λ of the electromagnetic waves of the active element 60.

[0080] This configuration can suppress the occurrence of substrate modes caused by electromagnetic waves propagating within the semiconductor substrate 50, thereby preventing electromagnetic waves of frequencies different from the desired frequency from being generated in the terahertz device 10.

[0081] In addition, since the semiconductor substrate 50 is supported by the insulating substrate 30, deformation of the semiconductor substrate 50 can be suppressed. Therefore, during the manufacture of the terahertz device 10, damage to the semiconductor substrate 850 constituting the semiconductor substrate 50 can be suppressed, and the semiconductor substrate 850 can be transported in an appropriate manner.

[0082] (2) The thickness Ts1 of the semiconductor substrate 50 is equal to or less than half the wavelength λ of the electromagnetic wave. This configuration further suppresses the generation of a substrate mode caused by the electromagnetic wave propagating within the semiconductor substrate 50, thereby further suppressing the generation of electromagnetic waves of frequencies different from the electromagnetic wave of the desired frequency in the terahertz device 10.

[0083] (3) The thickness Ts1 of the semiconductor substrate 50 is less than ¼ of the wavelength λ of the electromagnetic wave. This configuration further suppresses the generation of a substrate mode caused by the electromagnetic wave propagating within the semiconductor substrate 50, thereby further suppressing the generation of electromagnetic waves of frequencies different from the desired frequency in the terahertz device 10.

[0084] (4) The thickness Ts1 of the semiconductor substrate 50 is greater than the thickness Tm of the metal layer 40. With this configuration, the thickness Ts1 of the semiconductor substrate 50 is not excessively thin, and therefore the semiconductor substrate 50 can be easily manufactured.

[0085] (5) The insulating substrate 30 has higher rigidity than the semiconductor substrate 50. With this configuration, the insulating substrate 30 is less likely to deform than the semiconductor substrate 50. Therefore, the insulating substrate 30 can suppress deformation of the semiconductor substrate 50.

[0086] (6) The thickness Ts2 of the insulating substrate 30 is greater than the thickness Ts1 of the semiconductor substrate 50. With this configuration, even if the insulating substrate 30 is made of the same material as the semiconductor substrate 50, the insulating substrate 30 has higher rigidity than the semiconductor substrate 50. Therefore, the insulating substrate 30 can suppress deformation of the semiconductor substrate 50. This allows for a wider range of materials to be used for the insulating substrate 30.

[0087] (Application Examples of Terahertz Device) Application examples of the terahertz device 10 will be described with reference to FIGS. 13 to 15. FIG. 13 shows a schematic cross-sectional structure of a terahertz unit 100, which is a first application example of the terahertz device 10. FIG. 14 shows a schematic cross-sectional structure of a terahertz unit 200, which is a second application example of the terahertz device 10. FIG. 15 shows a schematic cross-sectional structure of a terahertz unit 300, which is a third application example of the terahertz device 10. Note that the terahertz device 10 shown in FIGS. 13 and 14 is shown to be thicker than its actual thickness in order to make the drawings easier to understand.

[0088] 13, the terahertz unit 100 includes the terahertz device 10, a dielectric 110, an antenna base 120, a reflective film 130 as a reflective portion, and a gas space 140. The gas in the gas space 140 is, for example, air.

[0089] The dielectric 110 is made of a dielectric material that transmits electromagnetic waves generated from the semiconductor element 20 of the terahertz device 10. In the first application example, the dielectric 110 is made of a resin material. An example of the resin material is epoxy resin (e.g., glass epoxy resin). The dielectric 110 has insulating properties. The dielectric refractive index n2, which is the refractive index (absolute refractive index) of the dielectric 110, is lower than the element refractive index n1, which is the refractive index of the semiconductor element 20. The element refractive index n1 is higher than the gas refractive index n3, which is the refractive index of the gas in the gas space 140. The dielectric refractive index n2 is higher than the gas refractive index n3. For example, the dielectric refractive index n2 is 1.55, and the element refractive index n1 is 3.4. The element refractive index n1 is the refractive index of the semiconductor substrate 50. In the first application example, the semiconductor substrate 50 is made of a material containing InP.

[0090] The dielectric 110 surrounds the terahertz device 10. In the first application example, the dielectric 110 surrounds the entire terahertz device 10. It can also be said that the dielectric 110 seals the terahertz device 10. The dielectric 110 is formed in the shape of, for example, a rectangular plate.

[0091] The antenna base 120 has a rectangular parallelepiped shape as a whole. The antenna base 120 is formed, for example, from an insulating material. In one example, the antenna base 120 is made of a dielectric material, for example, a synthetic resin such as epoxy resin. The material forming the antenna base 120 is arbitrary, and may be, for example, silicon or glass.

[0092] A dielectric 110 is laminated on a base surface 121 of the antenna base 120. The dielectric 110 is formed so as to protrude from the antenna base 120 when viewed from the z direction. The antenna base 120 has an antenna recess 122 recessed from the base surface 121. The antenna recess 122 is recessed in a direction away from the base surface 121. In the first application example, the antenna recess 122 is formed in a hemispherical shape as a whole. The antenna recess 122 opens toward the dielectric 110. The opening of the antenna recess 122 is circular when viewed from the z direction.

[0093] The antenna recess 122 has an antenna surface 123 that faces the terahertz device 10 across the dielectric 110 and the gas space 140. The antenna surface 123 is the inner surface of the antenna recess 122. The antenna surface 123 is formed to correspond to the shape of the antenna. In one example, the antenna surface 123 is curved so as to be concave in a direction away from the terahertz device 10. The antenna surface 123 is curved, for example, in a cone shape. In one example, the antenna surface 123 is curved so as to have a parabolic antenna shape.

[0094] The reflective film 130 reflects the electromagnetic waves radiated from the semiconductor element 20 in one direction. The reflective film 130 is formed on the antenna surface 123. Therefore, the reflective film 130 has an antenna shape. In the first application example, the reflective film 130 is a parabolic mirror of revolution. The reflective film 130 is formed of a material that reflects the electromagnetic waves radiated from the semiconductor element 20, and is formed of, for example, a metal such as Cu or an alloy. The reflective film 130 may have a single-layer structure or a multi-layer structure. The electromagnetic waves radiated from the semiconductor element 20 are reflected upward by the reflective film 130. Therefore, the terahertz unit 100 is configured to radiate electromagnetic waves upward.

[0095] The terahertz unit 100 includes external electrodes 151 and 152 used for electrical connection to the outside, and conductive portions 161 and 162 electrically connected to the terahertz device 10. The external electrodes 151 and 152 and the conductive portions 161 and 162 are each provided on the dielectric 110. The external electrodes 151 and 152 are provided so as to be exposed from the dielectric 110. The conductive portions 161 and 162 are provided within the dielectric 110.

[0096] The external electrodes 151 and 152 are arranged at positions that do not overlap the reflective film 130 when viewed from the z direction. Specifically, the external electrodes 151 and 152 are provided on a portion of the dielectric 110 that protrudes from the antenna base 120.

[0097] The conductive portions 161 and 162 connect the external electrodes 151 and 152 to the terahertz device 10. More specifically, the conductive portion 161 electrically connects the external electrode 151 to the first electrode 70 of the terahertz device 10. The conductive portion 162 electrically connects the external electrode 152 to the second electrode 80 of the terahertz device 10.

[0098] The terahertz device 10 is flip-chip mounted on the conductive portions 161 and 162. Specifically, the conductive portion 161 is connected to the first electrode pad 74 via a bump 171. The conductive portion 162 is connected to the second electrode pad 84 via a bump 172. The bumps 171 and 172 are configured with a layered structure of, for example, a metal layer containing Cu, a metal layer containing Ti, and a metal layer containing tin (Sn). Note that the bumps 171 and 172 may also have a single-layer structure.

[0099] Second Application Example As shown in FIG. 14, the terahertz unit 200 includes the terahertz device 10 , a support substrate 210 , and a waveguide 220 .

[0100] The support substrate 210 is formed in the shape of a rectangular plate. The support substrate 210 is made of an insulating material. An example of the insulating material is epoxy resin. The support substrate 210 has a substrate front surface 211 and a substrate back surface 212 opposite to the substrate front surface 211. Here, the substrate front surface 211 corresponds to the "support substrate front surface."

[0101] Two power supply lines 213 are formed on the substrate surface 211. Two external electrodes 214 are provided on the substrate back surface 212. Two connection conductors 215 are provided within the support substrate 210, respectively connecting the two power supply lines 213 and the two external electrodes 214. The terahertz device 10 is mounted on the substrate surface 211. The first electrode pad 74 of the first electrode 70 and the second electrode pad 84 of the second electrode 80 of the terahertz device 10 are individually electrically connected to the two power supply lines 213 by wires W.

[0102] The waveguide 220 is a hollow metal tube that transmits electromagnetic waves. The waveguide 220 is formed of a material that is opaque to the electromagnetic waves emitted or detected by the semiconductor element 20. Examples of such a material include metal materials such as Cu, Cu alloys, Al, and Al alloys. The waveguide 220 is laminated on the substrate surface 211. The waveguide 220 includes a through-hole 221 that penetrates the waveguide 220 in the z-direction. The waveguide 220 is formed in a rectangular parallelepiped shape. The support substrate 210 covers one end of the through-hole 221 in the z-direction. The waveguide 220 houses the terahertz device 10. That is, the terahertz device 10 is disposed within the through-hole 221 when viewed from the z-direction. The through-hole 221 functions as a transmission region 222 that transmits electromagnetic waves. The transmission region 222 is defined by the tapered surface of the through-hole 221. It can also be said that the terahertz device 10 is disposed within the transmission region 222 .

[0103] The shape of the through hole 221 when viewed from the z direction is circular. The through hole 221 is formed in a tapered shape that increases in diameter as it moves away from the support substrate 210 in the z direction. In other words, the through hole 221 is formed in a tapered shape that increases in diameter as it moves away from the terahertz device 10 in the z direction. The shape of the through hole 221 can be changed as desired. In one example, the shape of the through hole 221 when viewed from the z direction may be a polygon such as a square.

[0104] 15 , a terahertz unit 300 includes two semiconductor elements 20 and one insulating substrate 310 that supports the semiconductor elements 20. The insulating substrate 310 has a configuration similar to that of the insulating substrate 30 of the above embodiment. The insulating substrate 310 has larger dimensions in the x direction and the y direction than the insulating substrate 30 of the above embodiment.

[0105] The two semiconductor elements 20 include a semiconductor element 20 that emits electromagnetic waves and a semiconductor element 20 that detects electromagnetic waves. The two semiconductor elements 20 are arranged side by side and spaced apart from each other on an insulating substrate 310. Hereinafter, of the two semiconductor elements 20, the semiconductor element 20 that emits electromagnetic waves will be referred to as a first semiconductor element 20A, and the semiconductor element 20 that detects electromagnetic waves will be referred to as a second semiconductor element 20B.

[0106] The first semiconductor element 20A includes a first semiconductor substrate 50A, a first active element, a first electrode 70, and a second electrode 80. The first semiconductor substrate 50A, the first active element, the first electrode 70, and the second electrode 80 have the same configuration as the semiconductor substrate 50, the active element 60, the first electrode 70, and the second electrode 80 of the above embodiment. The first active element is an element that oscillates electromagnetic waves.

[0107] The second semiconductor element 20B includes a second semiconductor substrate 50B, a second active element, a first electrode 70, and a second electrode 80. The second semiconductor substrate 50B, the second active element, the first electrode 70, and the second electrode 80 have the same configuration as the semiconductor substrate 50, the active element 60, the first electrode 70, and the second electrode 80 of the above embodiment. The second active element is an element that detects electromagnetic waves.

[0108] Although not shown, a metal layer 40 is interposed between the first semiconductor substrate 50A and the insulating substrate 310. A metal layer 40 is interposed between the second semiconductor substrate 50B and the insulating substrate 310. Here, the metal layer 40 between the first semiconductor substrate 50A and the insulating substrate 310 corresponds to the "first substrate side metal layer," and the metal layer 40 between the second semiconductor substrate 50B and the insulating substrate 310 corresponds to the "second substrate side metal layer."

[0109] Although not shown, a first metal layer is interposed between the first semiconductor element 20A and the insulating substrate 310. A second metal layer is interposed between the second semiconductor element 20B and the insulating substrate 310. The first metal layer and the second metal layer have the same configuration as the metal layer 40 (see FIG. 2) in the above embodiment.

[0110] Furthermore, the terahertz unit 300 may include three or more semiconductor elements 20. That is, the terahertz unit 300 includes a plurality of semiconductor elements 20. All of the plurality of semiconductor elements 20 may be semiconductor elements that emit electromagnetic waves. All of the plurality of semiconductor elements 20 may be semiconductor elements that detect electromagnetic waves. Furthermore, among the plurality of semiconductor elements 20, the number of first semiconductor elements 20A and the number of second semiconductor elements 20B may be different from each other.

[0111] [Modifications] The above embodiment can be modified as follows. The above embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs. For ease of explanation, the first electrode 70 and the second electrode 80 are omitted from FIGS. 16 to 19. For ease of explanation, the thickness of the semiconductor substrate 50 is shown to be approximately equal to the thickness of the insulating substrate 30 in FIGS. 16 to 19. For ease of explanation, hatched lines are omitted from FIGS. 16 to 19.

[0112] 16 , the terahertz device 10 may include a through-hole 17. The through-hole 17 penetrates each of the semiconductor substrate 50, the metal layer 40, and the insulating substrate 30 in the z-direction. In this case, for example, the metal layer 40 may be formed so as to be recessed in a direction perpendicular to the z-direction relative to the inner surfaces of the semiconductor substrate 50 and the insulating substrate 30 that form the through-hole 17. The number of through-holes 17 can be changed as desired.

[0113] 17 , the terahertz device 10 may have a configuration in which vias 18 are embedded in the through holes 17. The vias 18 are exposed from both the device front surface 11 and the device back surface 12. The vias 18 may be in contact with the metal layer 40. The vias 18 may be electrically connected to, for example, a ground electrode (not shown). The vias 18 may also be electrically connected to the second electrode 80. This allows the metal layer 40 to be grounded. The number of through holes 17 and vias 18 can be changed as desired.

[0114] As shown in FIG. 18 , a through hole 54 may be formed in a part of the semiconductor substrate 50. The through hole 54 penetrates the semiconductor substrate 50 in the z-direction. Therefore, the through hole 54 exposes the metal layer 40. Although not shown, a through hole may be formed in a part of the insulating substrate 30 instead of the semiconductor substrate 50. The through hole penetrates the insulating substrate 30 in the z-direction. Therefore, the through hole of the insulating substrate 30 exposes the metal layer 40. The number of through holes 54 in the semiconductor substrate 50 can be changed as desired. The number of through holes in the insulating substrate 30 can also be changed as desired. Furthermore, for example, a via may be provided in the through hole 54 or the through hole of the insulating substrate 30. The via may be in contact with, for example, the second electrode 80. As a result, the metal layer 40 is electrically connected to the second electrode 80.

[0115] 19 , the semiconductor substrate 50 may include a plurality of slits 55. Each slit 55 extends from the substrate front surface 51 toward the substrate back surface 52 of the semiconductor substrate 50. The bottom surface of each slit 55 is provided at a position spaced apart from the substrate back surface 52 in the z direction.

[0116] Furthermore, the insulating substrate 30 may include a plurality of slits 33. Each slit 33 extends from the rear surface 32 toward the front surface 31 of the insulating substrate 30. The bottom surface of each slit 33 is provided at a position spaced apart from the front surface 31 in the z direction. The number of slits 33, 55 can be changed arbitrarily. In one example, there may be one slit 55. There may also be one slit 33. Either the slit 33 or the slit 55 may be omitted.

[0117] 20 , the side surface 43 of the metal layer 40 may be located inward relative to both the substrate side surface 56 of the semiconductor substrate 50 and the side surface 34 of the insulating substrate 30. In this case, when singulating in the manufacturing method of the terahertz device 10, the dicing blade can singulate the device by cutting both the semiconductor substrate 850 and the insulating substrate 830 without cutting the metal layer 40.

[0118] For example, an insulating bonding material may be interposed between the metal layer 40 and the surface 31 of the insulating substrate 30. In this case, the metal layer 40 is provided on the rear surface 52 of the semiconductor substrate 50. In this way, the metal layer 40 does not have to also function as a bonding layer.

[0119] For example, an insulating bonding material may be interposed between the metal layer 40 and the rear surface 52 of the semiconductor substrate 50. In this case, the metal layer 40 is provided on the front surface 31 of the insulating substrate 30. In this way, the metal layer 40 does not have to also function as a bonding layer.

[0120] The term "on" used in this disclosure includes the meanings of "on" and "above" unless the context clearly indicates otherwise. Therefore, the expression "A is formed on B" is intended to mean that, although in each of the above embodiments, A may be in contact with B and disposed directly on B, as a modified example, A may be disposed above B without contacting B. In other words, the term "on" does not exclude a structure in which another member is formed between A and B.

[0121] The z-direction used in this disclosure does not necessarily have to be the vertical direction, nor does it have to completely coincide with the vertical direction. Therefore, various structures according to this disclosure are not limited to the "up" and "down" of the z-direction described herein being "up" and "down" of the vertical direction. For example, the x-direction may be the vertical direction, or the y-direction may be the vertical direction.

[0122] [Note] The technical ideas that can be understood from the above-described embodiment and each modified example are described below. Note that, for the purpose of aiding understanding and not intending to limit the scope of the invention, the corresponding reference numerals in the embodiment are shown in parentheses for the configurations described in the notes. The reference numerals are shown as examples to aid understanding, and the components described with each reference numeral should not be limited to the components indicated by the reference numerals.

[0123] (Appendix A1) A terahertz device (10) comprising: a semiconductor substrate (50) having a substrate surface (51) and a substrate back surface (52) opposite to the substrate surface (51); an active element (60) provided on the substrate surface (51) for oscillating or detecting electromagnetic waves; an insulating substrate (30) arranged on the substrate back surface (52) side of the semiconductor substrate (50) and supporting the semiconductor substrate (50); and a metal layer (40) arranged between the semiconductor substrate (50) and the insulating substrate (30) and in contact with the substrate back surface (52), wherein the semiconductor substrate (50) has a thickness less than the wavelength (λ) of the electromagnetic waves.

[0124] (Appendix A2) The terahertz device according to Appendix A1, wherein the thickness (Ts1) of the semiconductor substrate (50) is equal to or less than half the wavelength (λ) of the electromagnetic wave.

[0125] (Appendix A3) The terahertz device according to Appendix A2, wherein the thickness (Ts1) of the semiconductor substrate (50) is less than ¼ of the wavelength (λ) of the electromagnetic wave.

[0126] (Appendix A4) The terahertz device according to any one of Appendices A1 to A3, wherein a thickness (Ts1) of the semiconductor substrate (50) is greater than a thickness (Tm) of the metal layer (40).

[0127] (Appendix A5) The terahertz device according to any one of Appendices A1 to A4, wherein the insulating substrate (30) has higher rigidity than the semiconductor substrate (50).

[0128] (Appendix A6) The terahertz device according to any one of Appendices A1 to A5, wherein a thickness (Ts2) of the insulating substrate (30) is greater than a thickness (Ts1) of the semiconductor substrate (50).

[0129] (Appendix A7) The terahertz device according to any one of Appendices A1 to A6, wherein the metal layer (40) includes a first metal layer (41) provided on the insulating substrate (30), and a second metal layer (42) provided on the rear surface (52) of the substrate.

[0130] (Appendix A8) The terahertz device according to any one of Appendices A1 to A7, wherein the metal layer (40) is in an electrically floating state.

[0131] (Appendix A9) The terahertz device according to any one of Appendices A1 to A8, wherein the semiconductor substrate (50) includes any one of InP, GaAs, and Si.

[0132] (Appendix A10) The insulating substrate (30) is made of AlN, SiC, Al ２ O ３ , Si, SiO ２ The terahertz device according to any one of appendices A1 to A9, comprising:

[0133] (Appendix A11) The terahertz device according to any one of Appendices A1 to A10, wherein the metal layer (40) contains at least one of Ti and Au.

[0134] (Appendix A12) A terahertz device according to any one of Appendices A1 to A11, comprising a first electrode (70) and a second electrode (80), wherein the active element (60) is electrically connected to the first electrode (70) and the second electrode (80), and the first electrode (70) and the second electrode (80) include: a first electrode plate (73) and a second electrode plate (83) arranged opposite each other so as to form a capacitor (91) electrically connected in parallel with the active element (60); and an antenna structure (90) that radiates or detects the electromagnetic waves.

[0135] (Appendix A13) A terahertz unit (100) comprising: a terahertz device (10) according to any one of Appendices A1 to A12; a dielectric (110) formed of a dielectric material and surrounding the terahertz device (10); a gas space (140) in which a gas is present; and a reflecting section (130) having a portion facing the terahertz device (10) across the dielectric (110) and the gas space (140), and reflecting the electromagnetic wave generated from the active element (60) and propagated through the dielectric (110) and the gas space (140) in one direction.

[0136] (Appendix A14) A terahertz unit (200) comprising: a support substrate (210) having a support substrate surface (211); a waveguide (220) laminated on the support substrate surface (211) and having a transmission region (222) that transmits the electromagnetic wave; and a terahertz device (10) according to any one of Appendices A1 to A12 mounted on the support substrate surface (211) within the transmission region (222).

[0137] (Appendix B1) A method for manufacturing a terahertz device, comprising: preparing a semiconductor substrate (850) having a substrate surface (851) and a substrate back surface (852) opposite the substrate surface (851); cutting the semiconductor substrate (850) to reduce its thickness; providing an active element (60) that emits or detects electromagnetic waves on the substrate surface (851); preparing an insulating substrate (830) having a surface (831); forming a first metal layer (841) in contact with the surface (831); forming a second metal layer (842) in contact with the substrate back surface (852); and bonding the first metal layer (841) and the second metal layer (842), wherein cutting the semiconductor substrate (850) to reduce its thickness involves cutting the semiconductor substrate (850) to a thickness less than the wavelength (λ) of the electromagnetic waves.

[0138] (Appendix B2) The method for manufacturing a terahertz device according to Appendix B1, wherein cutting the semiconductor substrate (850) to reduce its thickness includes cutting the semiconductor substrate (850) to a thickness of 1 / 2 or less of the wavelength (λ) of the electromagnetic wave.

[0139] (Appendix B3) The method for manufacturing a terahertz device according to Appendix B2, wherein cutting the semiconductor substrate (850) to reduce its thickness includes cutting the semiconductor substrate (850) to a thickness less than 1 / 4 of the wavelength (λ) of the electromagnetic wave.

[0140] (Appendix B4) A method for manufacturing a terahertz device according to any one of Appendices B1 to B3, wherein the semiconductor substrate (850) is prepared with a support substrate (900) in contact with the substrate surface (851), and the support substrate (900) is removed after the first metal layer (841) and the second metal layer (842) are bonded.

[0141] (Appendix B5) The method for manufacturing a terahertz device according to any one of Appendices B1 to B4, wherein cutting the semiconductor substrate (850) to reduce its thickness includes mirror-polishing the rear surface (852) of the substrate.

[0142] (Appendix C1) A terahertz device (10) that emits or detects electromagnetic waves, a dielectric (110) formed of a dielectric material and surrounding the terahertz device (10), a gas space (140) in which a gas is present, and a reflecting section (130) that has a portion facing the terahertz device (10) across the dielectric (110) and the gas space (140), and reflects the electromagnetic waves generated from the terahertz device (10) and propagated through the dielectric (110) and the gas space (140) in one direction, wherein the terahertz device (10) comprises: a semiconductor substrate (50) having a substrate surface (51) and a substrate back surface (52) opposite to the substrate surface (51); an active element (60) provided on the substrate surface (51) that oscillates or detects the electromagnetic waves; A terahertz unit (100) comprising: an insulating substrate (30) that is disposed on the side of the semiconductor substrate (50) on the substrate back surface (52) side and supports the semiconductor substrate (50); and a metal layer (40) that is disposed between the semiconductor substrate (50) and the insulating substrate (30) and that contacts the substrate back surface (52), wherein the semiconductor substrate (50) has a thickness that is less than the wavelength (λ) of the electromagnetic wave.

[0143] (Appendix C2) A terahertz device (10) comprising: a support substrate (210) having a support substrate surface (211); a waveguide (220) laminated on the support substrate surface (211) and having a transmission region (222) for transmitting electromagnetic waves; and a terahertz device (10) mounted on the support substrate surface (211) within the transmission region (222), wherein the terahertz device (10) comprises: a semiconductor substrate (50) having a substrate surface (51) and a substrate back surface (52) opposite the substrate surface (51); an active element (60) provided on the substrate surface (51) for oscillating or detecting the electromagnetic waves; an insulating substrate (30) disposed on the substrate back surface (52) side of the semiconductor substrate (50) and facing the support substrate surface (211); and a metal layer (40) disposed between the semiconductor substrate (50) and the insulating substrate (30) and in contact with the substrate back surface (52), The semiconductor substrate (50) has a thickness less than the wavelength (λ) of the electromagnetic wave.

[0144] (Appendix C3) The terahertz unit according to appendix C1 or C2, wherein the thickness (Ts1) of the semiconductor substrate (50) is equal to or less than ½ of the wavelength (λ) of the electromagnetic wave.

[0145] (Appendix C4) The terahertz unit according to Appendix C3, wherein the thickness (Ts1) of the semiconductor substrate (50) is less than ¼ of the wavelength (λ) of the electromagnetic wave.

[0146] (Appendix C5) A first semiconductor substrate (50A) having a first substrate surface (51) and a first substrate back surface (52) opposite to the first substrate surface (51); a first active element (60) provided on the first substrate surface (51) and oscillating an electromagnetic wave; a second semiconductor substrate (50B) having a second substrate surface (51) and a second substrate back surface (52) opposite to the second substrate surface (51); a second active element (60) provided on the second substrate surface (51) and detecting the electromagnetic wave; an insulating substrate (30) arranged on the first substrate back surface (51) side of the first semiconductor substrate (50A) and on the second substrate back surface (52) side of the second semiconductor substrate (50B); a first substrate side metal layer (40) arranged between the first semiconductor substrate (50A) and the insulating substrate (30) and in contact with the first substrate back surface (52); a second substrate-side metal layer (40) disposed between the second semiconductor substrate (50B) and the insulating substrate (30) and in contact with a rear surface (52) of the second substrate, wherein both the first semiconductor substrate (50A) and the second semiconductor substrate (50B) have a thickness less than the wavelength (λ) of the electromagnetic wave.

[0147] (Appendix C6) The terahertz unit according to Appendix C5, wherein the thickness of each of the first semiconductor substrate (50A) and the second semiconductor substrate (50B) is equal to or less than ½ of the wavelength (λ) of the electromagnetic wave.

[0148] (Appendix C7) The terahertz unit according to Appendix C6, wherein the thickness of each of the first semiconductor substrate (50A) and the second semiconductor substrate (50B) is less than ¼ of the wavelength (λ) of the electromagnetic wave.

[0149] The above description is merely illustrative. Those skilled in the art will recognize that many more possible combinations and permutations are possible other than the components and methods (manufacturing processes) listed for the purpose of illustrating the technology of the present disclosure. The present disclosure is intended to embrace all alternatives, modifications, and variations that fall within the scope of the present disclosure, including the claims.

[0150] REFERENCE SIGNS LIST 10... Terahertz device 11... Device surface 12... Device back surface 13-16... Device side surface 17... Through hole 18... Via 20... Semiconductor element 20A... First semiconductor element 20B... Second semiconductor element 30... Insulating substrate 31... Surface 32... Back surface 33... Slit 34... Side surface 40... Metal layer 41... First metal layer 41A... First metal film 41B... Second metal film 42... Second metal layer 42A... Third metal film 42B... Fourth metal film 43... Side surface 50... Semiconductor substrate 50A... First semiconductor substrate 50B... Second semiconductor substrate 51... Substrate surface 52... Substrate back surface 53... Insulating layer 53A... Opening 54... Through hole 55... Slit 56... Substrate side surface 60... Active element 61a... Semiconductor layer 62a, 62b...GaInAs layers 63a, 63b...GaInAs layers 64a, 64b...AlAs layers 65...InGaAs layer 70...First electrode 71...First conductive portion 71a...Connection portion 72...First wiring portion 73...First electrode plate 74...First electrode pad 80...Second electrode 81...Second conductive portion 82...Second wiring portion 83...Second electrode plate 83a...Protrusion portion 84...Second electrode pad 85...Contact portion 90...Antenna structure 91...Capacitor 100...Terahertz unit 110...Dielectric 120...Antenna base 121...Base surface 122...Antenna recess 123...Antenna surface 130...Reflecting film 140...Gas space 151, 152...External electrodes 161, 162...Conductive portion 171,172...Bump 200...Terahertz unit 210...Support substrate 211...Substrate surface 212...Substrate back surface 213...Power supply line 214...External electrode 215...Connecting conductor 220...Waveguide 221...Through hole 222...Transmission region 300...Terahertz unit 310...Insulating substrate 830...Insulating substrate 831...Surface 840...Metal layer 841...First metal layer 841A...First metal film 841B...Second metal film 842...Second metal layer 842A...Third metal film 842B...Fourth metal film 850...Semiconductor substrate 851...Substrate surface 852...Substrate back surface 900...Support substrate W...Wire RTD...Resonant tunneling diode P1...Oscillation point P2...Radiation point Ts1...Semiconductor substrate thickness Ts2...Insulating substrate thickness Tm: thickness of metal layer L1, L2: inductor R1, R2: wiring resistance

Claims

1. a semiconductor substrate having a substrate front surface and a substrate back surface opposite to the substrate front surface; an active element provided on a surface of the substrate, the active element generating or detecting an electromagnetic wave; an insulating substrate disposed on the rear surface side of the semiconductor substrate and supporting the semiconductor substrate; a metal layer disposed between the semiconductor substrate and the insulating substrate and in contact with a rear surface of the substrate; Equipped with The semiconductor substrate has a thickness less than the wavelength of the electromagnetic wave. Terahertz device.

2. The thickness of the semiconductor substrate is equal to or less than half the wavelength of the electromagnetic wave. The terahertz device according to claim 1 .

3. The thickness of the semiconductor substrate is less than ¼ of the wavelength of the electromagnetic wave. The terahertz device according to claim 2 .

4. The thickness of the semiconductor substrate is greater than the thickness of the metal layer. The terahertz device according to claim 3 .

5. The insulating substrate has a higher rigidity than the semiconductor substrate. The terahertz device according to claim 1 .

6. The insulating substrate has a thickness greater than that of the semiconductor substrate. The terahertz device according to claim 1 .

7. The metal layer is a first metal layer provided on the insulating substrate; A second metal layer provided on the rear surface of the substrate; Includes The terahertz device according to claim 1 .

8. The metal layer is in an electrically floating state. The terahertz device according to claim 1 .

9. The semiconductor substrate includes any one of InP, GaAs, and Si. The terahertz device according to claim 1 .

10. The insulating substrate is made of AlN, SiC, Al ２ O ３ , Si, SiO ２ Contains any of the following: The terahertz device according to claim 1 .

11. The metal layer includes at least one of Ti and Au. The terahertz device according to claim 1 .