JP2012215530A - Transmission type terahertz-wave inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmission type terahertz-wave inspection device that uses a resonance tunnel diode and determines the number of sheets based on a magnitude of attenuation by paper or the like by using transmission of terahertz-wave.SOLUTION: The transmission type terahertz-wave inspection device includes an oscillator 100 having a terahertz oscillation element, a detector 200 having a terahertz detection element, and paper or the like 300 placed between the oscillator 100 and the detector 200. The transmission type terahertz-wave inspection device detects, with the terahertz detection element, a transmission terahertz-wave obtained by transmitting, through the paper or the like, a terahertz-wave radiated by the terahertz oscillation element, and determines the number of sheets of the paper or the like 300 based on the magnitude of attenuation by the paper or the like 300.

Description

  The present invention relates to a transmission type terahertz wave inspection apparatus, and more particularly, to a transmission type terahertz wave inspection apparatus using a resonant tunnel diode.

  In recent years, electronic devices such as transistors have been miniaturized, and the size has become nano-sized. Therefore, a new phenomenon called a quantum effect has been observed. And development aiming at realization of ultra-high-speed devices and new functional devices using this quantum effect is in progress.

On the other hand, in such an environment, large-capacity communication, information processing, imaging, measurement, and the like are performed using a frequency range of 0.1 THz (10 ¹¹ Hz) to 10 THz, particularly called a terahertz band. An attempt is being made. This frequency region is an undeveloped region between light and radio waves. If a device that operates in this frequency band is realized, in addition to the above-mentioned imaging, large-capacity communication / information processing, physical properties, astronomy, living things, etc. It is expected to be used for many purposes such as measurement in various fields.

  On the other hand, an example using reflection / interference is disclosed as an inspection apparatus for paper using terahertz waves (see, for example, Patent Document 1).

JP 2009-3000279 A

  However, the reflectivity of terahertz waves by paper is not high, and it is difficult to observe interference unless banknotes and papers are ideally stacked properly. In addition, since interference occurs periodically depending on the thickness of paper, it is difficult to specify the number of sheets. In addition, since terahertz waves are likely to pass through papers, measurement accuracy decreases when reflection is used.

  An object of the present invention is to provide a transmission type terahertz wave inspection apparatus capable of determining the number of sheets based on the magnitude of attenuation by paper by using a resonant tunneling diode and utilizing transmission of terahertz waves. It is in.

  According to one aspect of the present invention for achieving the above object, an oscillator including a terahertz oscillation element, a detector including a terahertz detection element, and papers disposed between the oscillator and the detector are provided. The terahertz wave radiated from the terahertz oscillation element is transmitted through the paper, the transmitted terahertz wave is detected by the terahertz detection element, and based on the magnitude of attenuation by the paper, the paper A transmission type terahertz wave inspection apparatus for determining the number of sheets is provided.

  According to the present invention, there is provided a transmission type terahertz wave inspection apparatus capable of determining the number of sheets based on the magnitude of attenuation by paper by using a resonant tunneling diode and utilizing transmission of terahertz waves. Can do.

The typical block block diagram of the transmission-type terahertz wave inspection apparatus which concerns on embodiment. The typical block block diagram explaining the influence of the reflected wave of the transmission-type terahertz wave inspection apparatus which concerns on embodiment. The transmission terahertz wave inspection apparatus which concerns on embodiment WHEREIN: The figure which shows the relationship between the detection strength when the distance D = 2mm of an oscillator and a detector, and micro distance (DELTA) d. The transmission terahertz wave inspection apparatus which concerns on embodiment WHEREIN: The figure which shows the relationship between the detection intensity | strength when distance D of an oscillator and a detector is 3 cm, and micro distance (DELTA) d. The transmission terahertz wave inspection apparatus which concerns on embodiment WHEREIN: The figure which shows the relationship between the detection intensity | strength when the distance D of an oscillator and a detector is 5 cm, and micro distance (DELTA) d. The figure which shows the relationship between the detection intensity | strength and the distance D of an oscillator and a detector in the transmission-type terahertz wave inspection apparatus which concerns on embodiment. In the transmission-type terahertz wave inspection apparatus according to the embodiment, (a) a diagram for explaining a state of spread of the terahertz wave when the distance D between the oscillator and the detector is relatively close, (b) a distance between the oscillator and the detector The figure explaining the mode of the spread of the terahertz wave when D is relatively far. The typical bird's-eye view structure figure of the measurement system of the transmission type terahertz wave inspection device concerning an embodiment. The figure which shows the relationship between detection intensity | strength and the banknote number n in the transmission-type terahertz wave inspection apparatus which concerns on embodiment. The figure which shows the relationship between the transmittance | permeability and the number n of banknotes in the transmission-type terahertz wave inspection apparatus which concerns on embodiment. The transmission block type terahertz wave inspection device concerning an embodiment WHEREIN: The typical block lineblock diagram explaining the model in consideration of the influence in the bill in the attenuation and interference. The typical block block diagram explaining the model which considered the influence of the interference of the terahertz wave in a banknote. The figure which shows the relationship between the transmittance | permeability obtained by the theoretical formula of the transmittance | permeability from the model which considered the influence of the interference of the terahertz wave of FIG. The typical bird's-eye view of the terahertz oscillation detection element (RTD-SBD) applicable to the transmission-type terahertz wave inspection apparatus which concerns on embodiment. FIG. 14A is a schematic cross-sectional structure diagram taken along the line II of FIG. 14, and FIG. 14B is a schematic cross-sectional structure diagram taken along the line II-II of FIG. FIG. 17A is a schematic cross-sectional structure diagram of a terahertz oscillation detection element (RTD) applicable to the transmission terahertz wave inspection apparatus according to the embodiment, and FIG. 16B is a schematic cross-sectional structure diagram of a modified example of FIG. FIG. 3 is a schematic cross-sectional structure diagram of an integrated terahertz oscillation detection element (RTD-RTD), which is a schematic cross-sectional structure of a terahertz oscillation element RTD (O) and a terahertz detection element RTD (D) manufactured in the same process. (A) Typical circuit block diagram of terahertz oscillation element, (b) Simple equivalent circuit block diagram of terahertz oscillation element. (A) Typical circuit block diagram of terahertz detection element, (b) Simple equivalent circuit block diagram of terahertz detection element. (A) Typical equivalent circuit block diagram including antenna system of terahertz oscillation element, (b) Equivalent circuit block diagram of RTD of FIG. 20 (a). The typical equivalent circuit block diagram including the antenna system of the terahertz detection element. 4 is a current-voltage characteristic example of a terahertz oscillation detection element applicable to the transmission terahertz wave inspection apparatus according to the embodiment. The figure which shows the relationship between the oscillation frequency f which uses the resonator length L1 as a parameter, and the peak current Ip in the terahertz oscillation detection element applicable to the transmission type terahertz wave inspection apparatus according to the embodiment. The figure which shows the relationship between an oscillation intensity | strength and the oscillation frequency f in the terahertz oscillation detection element applicable to the transmission terahertz wave inspection apparatus which concerns on embodiment. The schematic diagram of the current-voltage characteristic of the Schottky barrier diode applicable to a terahertz oscillation detection element. The schematic diagram of the current-voltage characteristic of the terahertz oscillation detection element (RTD) applicable to the transmission-type terahertz wave inspection apparatus which concerns on embodiment. 4 is a current-voltage characteristic example of a terahertz oscillation detection element (RTD) applicable to the transmission type terahertz wave inspection apparatus according to the embodiment, and is a room temperature operation, a terahertz wave irradiation (A), and a terahertz wave non-existence. The characteristic example at the time of irradiation (B). (A) Circuit configuration diagram of a terahertz oscillation detection element (RTD-SBD) applicable to the transmission terahertz wave inspection apparatus according to the embodiment, (b) Example of operating characteristics when a reverse bias is applied to RTD and a forward bias is applied to SBD . (A) Circuit configuration diagram of a terahertz oscillation detection element (RTD-SBD) applicable to the transmission terahertz wave inspection apparatus according to the embodiment, (b) Example of operating characteristics when forward bias is applied to RTD and reverse bias is applied to SBD . The typical bird's-eye view of the terahertz oscillation detection element (RTD) of the modification 1 applicable to the transmission terahertz wave inspection apparatus which concerns on embodiment. The typical bird's-eye view of the terahertz oscillation detection element (RTD-SBD) of the modification 2 applicable to the transmission-type terahertz wave inspection apparatus which concerns on embodiment. FIG. 32 is a schematic plan view of a pattern structure of a first electrode 4, a second electrode 2a, and a semiconductor layer 91a corresponding to FIG. (A) The typical cross-section figure along the III-III line of FIG. 31, (b) The typical cross-section figure along the IV-IV line of FIG. In the terahertz detection element of the modification 2, the typical bird's-eye view which shows a mode that the insulator board | substrate was affixed on the sample surface and the semiconductor substrate was removed. The typical bird's-eye view which shows a mode that it saw from the back surface of FIG. The electromagnetic field simulation result of the terahertz oscillation detection element of the modification 2. (A) Schematic plan view of an electrode pattern structure of a terahertz oscillation detection element of Modification 3 applicable to the transmission type terahertz wave inspection apparatus according to the embodiment, (b) transmission type terahertz wave inspection apparatus according to the embodiment The typical top view of the electrode pattern structure of the terahertz oscillation detection element which concerns on the modification 4 applicable to FIG. The typical top view of the terahertz oscillation detection element (RTD-SBD) of the modification 5 applicable to the transmission-type terahertz wave inspection apparatus which concerns on embodiment. The typical top view of the terahertz oscillation detection element of the modification 6 applicable to the transmission-type terahertz wave inspection apparatus which concerns on embodiment.

  Next, embodiments of the present invention will be described with reference to the drawings. In the following, the same reference numerals are assigned to the same blocks or elements to avoid duplication of explanation and simplify the explanation. It should be noted that the drawings are schematic and different from the actual ones. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  The following embodiments exemplify apparatuses and methods for embodying the technical idea of the present invention. In the embodiments of the present invention, the arrangement of each component is as follows. Not specific. Various modifications can be made to the embodiment of the present invention within the scope of the claims.

[Embodiment]
(Transmission type terahertz wave inspection equipment)
As shown in FIG. 1, a schematic block configuration of the transmission terahertz wave inspection apparatus according to the embodiment includes an oscillator 100 including a terahertz oscillation element, a detector 200 including a terahertz detection element, and the oscillator 100 and the detector 200. And papers 300 arranged between the two. Here, the transmitted terahertz wave obtained by transmitting the terahertz wave radiated from the terahertz oscillation element through the paper 300 is detected by the terahertz detection element, and the amount of attenuation by the paper 300 is determined based on the magnitude of the attenuation by the paper 300. The number of sheets can be determined.

  In the transmission terahertz wave inspection apparatus according to the embodiment, a schematic block configuration for examining the influence of the reflected wave is expressed as shown in FIG. When the distance D between the oscillator 100 and the detector 200 is assumed, the intensity of the reflected terahertz wave hνr from the detector 200 or the like is measured with respect to the radiated terahertz wave hνi from the oscillator 100, thereby affecting the influence of the reflected wave. I can grasp it.

The reflectance R is expressed as a function of exp (−iδ). Here, δ = 2π / λ · n ₁ · d. n ₁ represents the refractive index of the paper 300 such as banknotes, d represents the film thickness of the paper 300 such as banknotes, and λ represents the wavelength of the terahertz wave. Since the reflectance R periodically changes according to the number of sheets of paper 300, if the number of sheets of paper 300 is detected by the change in reflectance, the number of sheets is, for example, one or three. I can't tell. Further, the reflectivity of the terahertz wave with respect to the paper 300 is low, which is about 20% or less. For example, in the configuration of FIG. 2, in the measurement example of the detection intensity in the detector 200 when there is no paper 300, it is about 75.3 mV, but when there is one paper 300, it is about 61.5 mV. About 80% or more, and reflectivity is about 20% or less.

-Relationship between distance D between oscillator and detector and detection intensity-
In the transmission terahertz wave inspection apparatus according to the embodiment, the relationship between the detection intensity and the minute distance Δd when the distance D = 2 mm between the oscillator 100 and the detector 200 is expressed as shown in FIG. The relationship between the detection intensity when the distance D of the detector 200 is 3 cm and the minute distance Δd is expressed as shown in FIG. 4, and the detection intensity and the minute distance when the distance D between the oscillator 100 and the detector 200 is 5 cm. The relationship with Δd is expressed as shown in FIG. 3 to 5, the measurement condition is that the distance D between the oscillator 100 and the detector 200 is set to a constant interval, and then the oscillator 100 is changed by a minute distance Δd.

  As apparent from FIGS. 3 to 5, the detected intensity changes with a period of Δd = λ / 2 = 0.5 mm, and the presence of a reflected wave is recognized. It can also be seen that the amplitude of the change in detection intensity decreases as the distance D between the oscillator 100 and the detector 200 increases. Thus, the presence or absence of the influence of the reflected wave can be confirmed by the presence of interference. The oscillation characteristics from the oscillator 100 also change due to the influence of the reflected wave from the detector 200 and the like.

  In the transmission terahertz wave inspection apparatus according to the embodiment, the relationship between the detection intensity and the distance D between the oscillator and the detector is expressed as shown in FIG. In FIG. 6, the measurement condition is that the distance D between the oscillator 100 and the detector 200 is changed in a state where a 300 GHz terahertz wave is oscillated from the oscillator 100.

  As shown in FIG. 6, the detection intensity decreases exponentially with an increase in the distance D between the oscillator 100 and the detector 200. Here, for example, the detection intensity f (x) is proportional to exp (−αx), where x is the distance. Here, α is a constant.

  Since the attenuation amount of the 300 GHz terahertz wave in the atmosphere is about 0.001% / cm, the influence of the attenuation by the atmosphere is small.

  On the other hand, in the transmission terahertz wave inspection apparatus according to the embodiment, the state of the spread of the terahertz wave beam 400 when the distance D between the oscillator 100 and the detector 200 is relatively short is as shown in FIG. The state of the spread of the terahertz wave beam 400 when the distance D between the oscillator 100 and the detector 200 is relatively long is expressed as shown in FIG. As apparent from FIGS. 7A and 7B, when the distance D between the oscillator 100 and the detector 200 increases due to the spread of the terahertz wave beam 400, the amount of electromagnetic waves detected decreases. Yes.

―Relationship between number of banknotes and detection intensity―
A schematic bird's-eye view structure of the measurement system of the transmission terahertz wave inspection apparatus according to the embodiment is represented as shown in FIG. Paper 300 made of banknotes is fixed on the support base 500 and disposed between the oscillator 100 and the detector 200.

  As shown in FIG. 8, banknotes are inserted between the oscillator 100 and the detector 200, and the result of measuring the intensity change (transmittance change) of the transmitted terahertz wave in the detector 200 is shown in FIGS. 9 to 10. Represented as shown. That is, in the transmission terahertz wave inspection apparatus according to the embodiment, the measurement result of the relationship between the detected intensity and the number n of banknotes is expressed as shown in FIG. 9, and the relationship between the transmittance and the number n of banknotes is As shown in FIG.

  As apparent from FIG. 9, unlike the reflectance measurement type inspection apparatus, the detection intensity decreases as the number of banknotes n increases. In the example of FIG. 9, it can be seen that the detection intensity value of about 30 mV is the detection limit DL, and it is possible to detect up to n = 5.

  As is clear from FIG. 10, the transmittance decreases as the number of banknotes n increases.

  In the transmission-type terahertz wave inspection apparatus according to the embodiment, a schematic block configuration for explaining a model in consideration of the effects of attenuation / interference in banknotes and interference between banknotes is expressed as shown in FIG. . In FIG. 11, the interference in the banknote is represented by PI, and the interference between the banknotes is represented by PD. The result of calculating the transmittance in consideration of the attenuation / interference in banknotes and the interference between banknotes is shown in FIG. 10 as a calculated value. Here, the attenuation of the banknote is based on the detected intensity f (x) ∝exp (−αx) described in FIG.

  From the comparison between the calculated value and the experimental value in FIG. 10, it was confirmed that the terahertz wave propagating in the banknote attenuated exponentially.

―Interference of terahertz waves in banknotes―
Here, for reference, interference of terahertz waves in a banknote will be described.

A model considering the influence of terahertz wave interference in the banknote is expressed as shown in FIG. The terahertz wave I ₁ radiated from the oscillator 100 is attenuated to I ₂ in the paper 300 and further detected as I _{3 by the} detector 200. On the other hand, in the paper 300, the intensity is modulated by the interference effect and propagated as I ₄ , and further detected as I _{5 by the} detector 200.

Based on FIG. 12, the transmittance T in consideration of the interference effect of the terahertz wave in the banknote is expressed by the following equation. That is,
T = 1 / [1 + 4Rsin ² (χn ₁ L) / (1-R) ² ]
Here, n ₁ is obtained by a refractive index, χ = 2π / λ, and a reflectance R = | (1−n ₁ ) / (1 + n ₁ | ² .

  The relationship between the transmittance obtained by the above theoretical formula of the transmittance and the number of banknotes n from the model considering the influence of the interference of the terahertz wave in FIG. 12 is expressed as shown in FIG. In the result of FIG. 13, the transmittance changes periodically according to the number of banknotes n.

  As is clear from FIGS. 12 and 13, the model considering only the interference of the terahertz wave in the banknote cannot explain the experimental result that the transmittance decreases exponentially.

  From the above results, the attenuation in the banknote is based on the detected intensity f (x) ∝exp (−αx) described in FIG. 6 and, as shown in FIGS. 10 and 11, attenuation / interference in the banknote, The experimental results can be explained based on a model that considers the influence of interference between banknotes.

  According to the transmission-type terahertz wave inspection apparatus according to the embodiment, it is possible to determine the number of sheets based on the magnitude of attenuation by paper using a resonant tunnel diode and using transmission of terahertz waves. .

  Note that both the terahertz oscillation element constituting the oscillator 100 and the terahertz detection element constituting the detector 200 can be configured using an RTD (Resonant Tunneling Diode). The basic structure includes an RTD and a slot antenna structure integrated with the RTD.

  Further, a terahertz oscillation detection element that can realize an oscillation element and a detection element with one element can be applied to the terahertz oscillation element that constitutes the oscillator 100 and the terahertz detection element that constitutes the detector 200. The basic structure is composed of an RTD and a slot antenna structure integrated with the RTD. With this basic structure, a terahertz oscillation detecting element can be realized. In the following description, the terahertz oscillation detection element will be mainly described in detail.

(Terahertz oscillation detector)
A schematic bird's-eye view structure of a terahertz oscillation detecting element applicable to the transmission type terahertz wave inspection apparatus according to the embodiment is represented as shown in FIG. 14, and a schematic cross-sectional structure along the line II in FIG. A schematic cross-sectional structure expressed as shown in FIG. 15A and taken along line II-II in FIG. 14 is expressed as shown in FIG.

  A schematic bird's-eye view structure of a terahertz oscillation detecting element applicable to the transmission terahertz wave inspection apparatus according to the embodiment includes a semiconductor substrate 1 and a first structure disposed on the semiconductor substrate 1, as shown in FIGS. Two electrodes 2, 2 a, an insulating layer 3 disposed on the second electrode 2, a second electrode disposed on the semiconductor substrate 1 with respect to the second electrode 2 via the insulating layer 3. A first electrode 4 (4a, 4b, 4c) disposed opposite to the electrode 2, an MIM reflector 50 formed between the first electrode 4a and the second electrode 2 with the insulating layer 3 interposed therebetween, and an MIM reflector 50, a resonator 60 disposed between the first electrode 4 and the second electrode 2 opposed to each other on the semiconductor substrate 1, an active element 90 disposed at a substantially central portion of the resonator 60, Adjacent to the resonator 60, the first electrode 4 and the second electrode facing the semiconductor substrate 1. A waveguide 70 disposed between the two electrodes, a horn opening 80 disposed between the first electrode 4 and the second electrode 2 facing the semiconductor substrate 1 adjacent to the waveguide 70, and the first The electrode 4 and the SBD 30 connected between the second electrode 2 are provided.

  The active element 90 is typically an RTD, but can be composed of other diodes or transistors. Other active elements include, for example, a tannet (TUNNETT) diode, an impulse (Impact Ionization Avalanche Transit Time) diode, a GaAs field effect transistor (FET), a GaN FET, a high An electron mobility transistor (HEMT), a heterojunction bipolar transistor (HBT), or the like can also be applied.

  The horn opening 80 is composed of an open horn antenna. The opening angle θ of the horn opening is desirably set to about 10 degrees or less, for example, in order to provide directivity in the electromagnetic wave (hν) detection direction. The length L3 of the horn opening 80 is, for example, about 700 μm or less. The opening width at the tip of the horn opening 80 is, for example, about 160 μm.

  The waveguide 70 is disposed in the opening of the resonator 60. The length L2 of the waveguide 70 is, for example, about 700 μm or less. In addition, the distance between the first electrode 4 and the second electrode 2 in the waveguide 70 is, for example, about 24 μm.

  Note that the horn shape of the horn opening 80 is a structure necessary for effectively detecting electromagnetic waves from the air. Due to the horn shape, electromagnetic waves can be efficiently detected from the air with good impedance matching. The shape of the horn is not limited to a linear shape, but may be a non-linear shape, a curved shape, a quadratic curved shape, a parabolic shape, a stepped shape, or the like.

  In the resonator 60, two concave portions 5 and 6 are formed, and a convex portion 7 is formed between the two concave portions 5 and 6. Then, a protrusion 8 is formed at a substantially central portion of the protrusion 7 of the first electrode 4, and an active element 90 is disposed below the protrusion 8 so as to be sandwiched between the second electrode 2. .

The length L1 of the resonator 60 is, for example, about 30 μm or less. The length of the protrusion 8 is, for example, about 6 μm or less. Further, the width of the recesses 5 and 6 (the distance between the first electrode 4 and the second electrode 2) is, for example, about 4 μm. The dimension of the active element 90 is, for example, about 1.4 μm ² . However, the size of the active element 90 is not limited to this value, and may be, for example, about 5.3 μm ² or less. The detailed structure of the active element 90 will be described later. The size of each part of the resonator 60 is not limited to the above dimensions, and is appropriately set in design according to the frequency of the terahertz electromagnetic wave to be received.

  Further, as shown in FIG. 14, compared to the distance between the first electrode 4 and the second electrode 2 in the waveguide 70, the first electrode 4 and the second electrode in the portion where the resonator 60 is formed. The interval between the electrodes 2 is narrow.

  The MIM reflector 50 is disposed at the closing portion on the opposite side of the opening of the resonator 60. Due to the laminated structure of the metal / insulator / metal MIM reflector 50, the first electrode 4 and the second electrode 2 are short-circuited in high frequency. Further, the MIM reflector 50 has an effect that it can reflect a high frequency while being open in terms of direct current.

  Each of the first electrode 4 (4a, 4b, 4c) and the second electrode 2, 2a has, for example, a metal laminated structure of Au / Pd / Ti, and the Ti layer is a semi-insulating InP substrate described later. It is a buffer layer for making the contact state with the semiconductor substrate 1 which consists of favorable. The thickness of each part of the first electrodes 4a, 4b, 4c and the second electrodes 2, 2a is, for example, about several hundred nm, and as a whole, as shown in FIGS. 15 (a) and 15 (b). A flattened laminated structure is obtained. Note that both the first electrode 4 and the second electrode 2 can be formed by a vacuum evaporation method, a sputtering method, or the like.

  More specifically, the first electrode 4a and the first electrode 4c are made of, for example, Au / Pd / Ti, and the first electrode 4b is made of, for example, Au / Ti. The second electrode 2 is made of, for example, Au / Pd / Ti, and the second electrode 2a is made of, for example, Au / Ti.

  Note that the Ti layer forming the surface layer of the first electrode 4b is desirably removed in order to reduce the contact resistance when the extraction electrode is formed by a bonding wire (not shown). Similarly, the Ti layer forming the surface layer of the second electrode 2a is desirably removed in order to reduce the contact resistance when forming the extraction electrode with a bonding wire (not shown).

The insulating layer 3 can be formed of, for example, a SiO ₂ film. In addition, a Si ₃ N ₄ film, a SiON film, a HfO ₂ film, an Al ₂ O ₃ film, or the like can be applied. The thickness of the insulating layer 3 can be determined in consideration of the geometric plane size of the MIM reflector 50 and the required capacitor value in terms of circuit characteristics, and is, for example, about several tens nm to several hundreds nm. . The insulating layer 3 can be formed by a chemical vapor deposition (CVD) method, a sputtering method, or the like.

―Resonant tunnel diode―
A schematic cross-sectional structure of a resonant tunneling diode (RTD) applicable to the transmission terahertz wave inspection apparatus according to the embodiment is expressed as shown in FIG. It is expressed as shown in FIG.

  As shown in FIG. 16A, a configuration example of an RTD as an active element 90 applicable to the transmission terahertz wave inspection apparatus according to the embodiment is disposed on a semiconductor substrate 1 made of a semi-insulating InP substrate. , a GaInAs layer 91a doped with n-type impurities at a high concentration, a GaInAs layer 92a doped with n-type impurities, and an undoped GaInAs layer 93b disposed on the GaInAs layer 92a. , An RTD portion composed of an AlAs layer 94a / GaInAs layer 95 / AlAs layer 94b disposed on the GaInAs layer 93b, an undoped GaInAs layer 93b disposed on the AlAs layer 94b, and a GaInAs layer 93a. , n-type impurity doped GaInAs layer 92b and GaInAs layer 92b. Comprises a n-type impurity heavily doped GaInAs layer 91b, a first electrode 4a which is arranged on the GaInAs layer 91b, a second electrode 2 arranged on the GaInAs layer 91a.

  In the modified example, as shown in FIG. 16B, a GaInAs layer 91c doped with a high concentration of n-type impurities is further disposed on a GaInAs layer 91b doped with a high concentration of n-type impurities. The contact with the electrode 4a is made good.

As shown in FIGS. 16A and 16B, the RTD portion is formed by sandwiching a GaInAs layer 95 between AlAs layers 94a and 94b. The RTD portion laminated in this way is interposed with n-type GaInAs layers 92a and 92b and n ⁺ -type GaInAs layers 91a, 91b or 91c with undoped GaInAs layers 93a and 93b used as spacers interposed therebetween. The second electrode 2 and the first electrode 4 are ohmicly connected.

  Here, the thickness of each layer is as follows, for example.

The thicknesses of the n ⁺ -type GaInAs layers 91a, 91b, and 91c are, for example, about 400 nm, 15 nm, and 8 nm, respectively. The thicknesses of the n-type GaInAs layers 92a and 92b are substantially equal, for example, about 25 nm. The undoped GaInAs layers 93a and 93b have a thickness of about 2 nm and 20 nm, for example. The thicknesses of the AlAs layers 94a and 94b are equal, for example, about 1.1 nm. The thickness of the GaInAs layer 95 is about 4.5 nm, for example.

Note that, on the side wall portion of the stacked structure shown in FIGS. 16A and 16B, an SiO ₂ film, an Si ₃ N ₄ film, an SiON film, an HfO ₂ film, an Al ₂ O ₃ film, or the like, An insulating film made of a multilayer film can also be deposited. The insulating layer can be formed by a CVD method, a sputtering method, or the like.

  In the terahertz oscillation detection element applicable to the transmission terahertz wave inspection apparatus according to the embodiment, the terahertz oscillation element and the terahertz detection element can be formed in the same manufacturing process. In this case, RTD (D) is used as a detection element instead of SBD. A schematic cross-sectional structure of a terahertz oscillation element RTD (O) and a terahertz detection element RTD (D) manufactured in the same process, and a schematic cross-sectional structure of an integrated terahertz oscillation detection element (RTD-RTD) is: It is expressed as shown in FIG. Since the configuration of each layer is the same as that in FIG.

For example, in a terahertz oscillation detection element manufactured in the same process, the oscillation frequency observed at room temperature is about 300 GHz. Further, for example, the current density Jp of the terahertz oscillation detecting element at the time of oscillation is about 7 mA / μm ² .

  In the terahertz oscillation detection element applicable to the transmission terahertz wave inspection apparatus according to the embodiment, the thickness of the AlAs layers 94a and 94b serving as the barrier layers is increased compared to the terahertz oscillation element, and the detection time is increased. The noise density may be reduced by setting the current density Jp of the terahertz detecting element at low. Similarly, in the terahertz oscillation detection element applicable to the transmission type terahertz wave inspection apparatus according to the embodiment, the n-type GaInAs layers 92a and 92b are formed at lower doping levels than in the terahertz oscillation element. The noise density may be reduced by setting the current density Jp of the terahertz detecting element at low. In the case of an oscillation element, it is desirable that the RTD current density is large. However, when used as a detection element, oscillation may cause noise, so the RTD current density is desirably relatively low. For this reason, when there is a possibility that the oscillation becomes noise, a structure for reducing the noise may be provided by deliberately reducing the current density.

  In the terahertz oscillation detection element applicable to the transmission terahertz wave inspection apparatus according to the embodiment, bismuth (Bi) wiring for suppressing parasitic oscillation is not necessary.

―Circuit configuration―
A schematic circuit configuration of the oscillation element (RTD) of the terahertz oscillation detection element (RTD-RTD) applicable to the transmission type terahertz wave inspection apparatus according to the embodiment includes an active element 90 as shown in FIG. And a capacitor CM composing the MIM reflector 50. A diode anode is connected to the first electrode 4, a diode cathode is connected to the second electrode 2, a negative voltage is applied to the first electrode 4, and a positive voltage is applied to the second electrode 2. Is applied. In the oscillation state, the electromagnetic wave (hν) from the Y-axis direction that is the opening direction of the horn opening is detected with good directivity.

  In the simple equivalent circuit configuration corresponding to FIG. 19A, as shown in FIG. 19B, the RTD constituting the active element 90 can be represented by a parallel circuit of the capacitor C01 and the inductor L01, and the MIM reflector 50 Are further connected in parallel.

  A schematic circuit configuration of the detection element (RTD) of the terahertz oscillation detection element (RTD-RTD) applicable to the transmission type terahertz wave inspection apparatus according to the embodiment includes an active element 90 as shown in FIG. And a capacitor CM composing the MIM reflector 50. A diode anode is connected to the first electrode 4, a diode cathode is connected to the second electrode 2, a negative voltage is applied to the first electrode 4, and a positive voltage is applied to the second electrode 2. Is applied. In the detection state, the electromagnetic wave (hν) from the Y-axis direction that is the opening direction of the horn opening is detected with good directivity.

  In the simple equivalent circuit configuration corresponding to FIG. 19A, as shown in FIG. 19B, the RTD constituting the active element 90 can be represented by a parallel circuit of the capacitor C01 and the inductor L01, and the MIM reflector 50 Are further connected in parallel.

A schematic equivalent circuit configuration including the antenna system of the oscillation element (RTD) of the terahertz oscillation detection element (RTD-RTD) applicable to the transmission type terahertz wave inspection apparatus according to the embodiment is shown in FIG. As described above, the parallel circuit of the active element 90 representing the diode (RTD) system and the capacitor CM is connected in parallel to the parallel circuit of the antenna inductor L, the antenna capacitor CA, and the antenna radiation resistance G _ANT representing the antenna (ANT) system. Is done.

  As shown in FIG. 20 (b), the equivalent circuit configuration of the diode constituting the active element 90 of FIG. 20 (a) includes a parallel circuit of a contact portion composed of a contact resistance Rc and a contact capacitor Cc, and an external diode capacitor CD / A parallel circuit of a diode part composed of an internal diode capacitor Cd and a diode negative resistance (-Gd) and a series circuit of a mesa part composed of an inductor LM and a resistor RM are connected in series.

Here, the admittance Y of the entire equivalent circuit is
Y = Yd + Yc.Ya.Ym / (Yc.Ya + Ya.Ym + Yc.Ym)
It is represented by Here, Yd = −Gd + jωCd, Yc = 1 / Rc + jωCc, Ym = 1 / (Rm + jωLm), Ya represents the admittance of the antenna system, and ω represents the oscillation angular frequency. Each parameter can be obtained from a physical property value of a diode (RTD) constituting the active element 90.

A schematic equivalent circuit configuration including the antenna system of the detection element (RTD) of the terahertz oscillation detection element (RTD-RTD) applicable to the transmission terahertz wave inspection apparatus according to the embodiment is as shown in FIG. A parallel circuit of an antenna inductor L, an antenna capacitor CA, and an antenna radiation resistance G _ANT representing an antenna (ANT) system is connected in parallel to the parallel circuit of the active element 90 representing the diode (RTD) system and the capacitor CM.

  An example of the current-voltage characteristic of the terahertz oscillation detection element applicable to the transmission terahertz wave inspection apparatus according to the embodiment is expressed as shown in FIG. 22, and at about 0.75 V, the value of the peak current Ip is about 12 mA is obtained. Further, negative differential resistance (NDR) is obtained in the range of 0.7V to 1.0V. The peak-to-valley ratio is about 3.

  In the terahertz oscillation detection element applicable to the transmission terahertz wave inspection apparatus according to the embodiment, the relationship between the oscillation frequency f and the peak current Ip using the resonator length L1 as a parameter is expressed as shown in FIG. With the resonator length L1 = 80 μm, an oscillation frequency f of about 250 to 300 GHz, with L1 = 60 μm, about 300 to 320 GHz, with L1 = 40 μm, about 350 to 370 GHz, and with L1 = 20 μm, an oscillation frequency f of about 380 to 400 GHz is obtained. Yes. The value of the peak current Ip is about 4 to 10 mA. As the resonator length L1 becomes shorter, the oscillation frequency f tends to increase.

  In the terahertz oscillation detection element applicable to the transmission terahertz wave inspection apparatus according to the embodiment, the relationship between the oscillation intensity and the oscillation frequency f is expressed as shown in FIG. An oscillation frequency f of about 300 GHz is obtained at room temperature. The value of the oscillation frequency f can be changed by adjusting the structure of each layer, the size of the mesa region, the antenna structure, and the like shown in FIG.

  A current-voltage characteristic of a Schottky Barrier Diode (SBD) applicable to a terahertz oscillation detecting element applicable to the transmission type terahertz wave inspection apparatus according to the embodiment is schematically shown in FIG. expressed.

  On the other hand, the current-voltage characteristics of the terahertz oscillation detection element (RTD) applicable to the transmission terahertz wave inspection apparatus according to the embodiment are negative in the forward and reverse directions, as schematically shown in FIG. Because of having a resistance, there is a region having a large nonlinearity compared to SBD, and when RTD is applied as a detection element, sensitivity is increased.

  In SBD, the number of electrons that flow beyond the Schottky barrier increases with temperature. Therefore, when the temperature is increased to increase detection sensitivity, thermal noise increases and the S / N ratio decreases. On the other hand, in the terahertz oscillation detection element (RTD) applicable to the transmission terahertz wave inspection apparatus according to the embodiment, electrons contributing to the tunnel current are electrons lower than the Fermi energy level. For this reason, the temperature dependence of the tunnel current is small. Therefore, in the terahertz oscillation detection element (RTD) according to the embodiment, the nonlinearity is large before and after the negative resistance, so that the S / N ratio is improved.

  As shown in FIG. 26, the operating point Q on the current-voltage characteristic is the NDR region. In order to increase the detection sensitivity in the terahertz oscillation detection element according to the embodiment, it is desirable to set the operating point on the current-voltage characteristic to the non-oscillation state and maximize the rate of change of the differential resistance. Such an operating point corresponds to the operating point P and the operating point Q on the current-voltage characteristics of the terahertz oscillation detecting element according to the embodiment. That is, the operating point P and the operating point R on the current-voltage characteristic are in the NDR region, and the detection sensitivity has a maximum value.

  FIG. 6 is an example of current-voltage characteristics of a terahertz oscillation detection element (RTD) applicable to the transmission terahertz wave inspection apparatus according to the embodiment, in a room temperature operation, when a terahertz wave is irradiated (A) and when the terahertz wave is not The characteristic change at the time of irradiation (B) is expressed as shown in FIG. As shown in FIG. 27, by setting the bias voltage to 0.5 V, for example, terahertz electromagnetic waves can be detected with good sensitivity and at room temperature.

The circuit configuration of the terahertz oscillation detection element (RTD-SBD) applicable to the transmission type terahertz wave inspection apparatus according to the embodiment is expressed as shown in FIG. 28A, where RTD is reverse biased and SBD is forward biased An example of the operating characteristic at the time of application is expressed as shown in FIG. In FIG. 28 (b), P _R corresponds to the bias point at the time of oscillation when a reverse bias is applied to the RTD.

The circuit configuration of the terahertz oscillation detection element (RTD-SBD) applicable to the transmission type terahertz wave inspection apparatus according to the embodiment is represented as shown in FIG. 29A, where RTD is forward biased and SBD is reverse biased. An example of the operating characteristic at the time of application is expressed as shown in FIG. In FIG. 29 (b), P _D corresponds to the bias point at the time of detection of the forward bias applied to the RTD.

  In the terahertz oscillation detection element (RTD-SBD) applicable to the transmission terahertz wave inspection apparatus according to the embodiment, the RTD and the SBD are connected in parallel. At this time, when the current flows in the direction in which the RTD functions as an oscillation element, the SBD becomes a parasitic oscillation suppression element by allowing the current to flow in the forward direction of the SBD.

  When a current is passed in the opposite direction, the SBD functions as an insulator and the RTD functions as a detection element.

  Since both RTD and SBD exhibit asymmetric current-voltage characteristics, the terahertz oscillation detection element (RTD-SBD) according to the embodiment functions as both an oscillation element and a detection element by combining them well. be able to.

  Here, the SBD connected in parallel with the RTD is only for rectification and is not used as a detection element. The ideal of SBD is that in forward bias, no current flows until the voltage at which RTD exhibits negative resistance, and it acts as a resistor that suppresses parasitic oscillation in the negative resistance region. On the other hand, the reverse bias is to act as an insulator from which no current flows. As a result, there is an advantage that less current flows through the entire circuit when the voltage is not related to oscillation.

-Modification 1-
A schematic bird's-eye view structure of the terahertz oscillation detection element of Modification Example 1 applicable to the transmission terahertz wave inspection apparatus according to the embodiment is expressed as shown in FIG.

  In Modification 1, as shown in FIG. 30, the semiconductor substrate 1 is a region where the first electrode 4 and the second electrode 2 that form the resonator 60, the waveguide 70, and the horn opening 80 are disposed. In FIG. On the semiconductor substrate 1, an SBD 30 connected between the first electrode 4 and the second electrode 2 is provided. Furthermore, as shown in FIG. 30, the waveguide 70 between the first electrode 4 and the second electrode 2 and the semiconductor substrate 1a of the horn opening 80 may be completely removed. Other configurations are the same as the configuration of FIG. 14, and thus description of each unit is omitted.

  In FIG. 30, the thickness of the thinned semiconductor substrate 1a is about 20 μm, for example. The length of the waveguide 70 is, for example, about 700 μm or less, and the length of the horn opening 80 is, for example, about 700 μm or less. The total length of the terahertz detection element according to the first modification including the MIM reflector 50 is, for example, about 1600 μm or less.

  According to the electromagnetic field simulation result of the terahertz oscillation detection element of Modification Example 1, the electric field pattern is formed at constant intervals in the Y-axis direction along the electrode pattern extending in the Y-axis direction on the thinned semiconductor substrate 1a. There is almost no leakage of the electric field in the vertical direction (−Z axis direction) to the semiconductor substrate 1a. Further, according to the three-dimensional electromagnetic field simulation result in the XYZ-axis directions, the directivity in the Y-axis direction is remarkably improved. Further, from the relationship between the Y-axis direction radiation intensity and the oscillation frequency, the harmonic component is suppressed, and the directivity is improved. As a technique for forming the thinned semiconductor substrate 1a, a technique for forming a MEMS (Micro Electro Mechanical Systems) element can be applied.

  According to the terahertz oscillation detection element of the first modification, it is possible to suppress the influence of the substrate by thinning the semiconductor substrate, improve directivity, and highly efficiently in the lateral direction with respect to the substrate. It is possible to detect the oscillation of radio waves and to easily integrate.

  According to the terahertz oscillation detecting element of the first modification, the influence of the substrate can be suppressed by thinning the semiconductor substrate, the directivity is improved in the direction horizontal to the substrate, and the terahertz electromagnetic wave is efficiently generated. Oscillation can be detected.

-Modification 2-
A schematic bird's-eye view structure of the terahertz oscillation detection element of Modification 2 applicable to the transmission type terahertz wave inspection apparatus according to the embodiment is represented as shown in FIG. 31, and the first electrode corresponding to FIG. 4. A schematic plan view of the pattern structure of the second electrode 2a and the semiconductor layer 91a is expressed as shown in FIG. Further, a schematic cross-sectional structure taken along line III-III in FIG. 31 is represented as shown in FIG. 33A, and a schematic cross-sectional structure taken along line IV-IV in FIG. 31 is shown in FIG. Represented as shown.

  As shown in FIGS. 31 to 33, the terahertz oscillation detection element of Modification 2 includes an insulator substrate 10, a first electrode 4 (4 a, 4 b, 4 c) disposed on the insulator substrate 10, An insulating layer 3 disposed on one electrode 4a, an interlayer insulating film 9 disposed on an insulator substrate 10, and an insulating layer 3 disposed on the interlayer insulating film 9 and with respect to the first electrode 4a. A second electrode 2, 2 a disposed opposite to the first electrode 4 via the semiconductor layer 91, a semiconductor layer 91 a disposed on the second electrode 2, and the first electrode 4 a sandwiching the insulating layer 3 The MIM reflector 50 formed between the second electrodes 2, and the resonator 60 disposed between the first electrode 4 and the second electrode 2 facing the insulator substrate 10 adjacent to the MIM reflector 50. An active element 90 disposed substantially at the center of the resonator 60, and an insulator substrate adjacent to the resonator 60. The waveguide 70 disposed between the first electrode 4 and the second electrode 2 facing each other on the substrate 10, and the first electrode 4 and the second electrode facing each other on the insulator substrate 10 adjacent to the waveguide 70. A horn opening 80 disposed between the first electrode 4 and the SBD 30 connected between the first electrode 4 and the second electrode 2.

  The horn opening 80 is composed of an open horn antenna. The opening angle θ of the horn opening is preferably set to about 10 degrees or less, for example, in order to provide directivity in the terahertz electromagnetic wave (hν) detection direction. The length L3 of the horn opening 80 is, for example, about 700 μm or less. The opening width at the tip of the horn opening 80 is, for example, about 160 μm.

  The waveguide 70 is disposed in the opening of the resonator 60. The length L2 of the waveguide 70 is, for example, about 700 μm or less. In addition, the distance between the first electrode 4 and the second electrode 2 in the waveguide 70 is, for example, about 24 μm.

  Note that the horn shape of the horn opening 80 is a structure necessary for effectively detecting terahertz electromagnetic waves from the air. By the horn shape, terahertz electromagnetic waves can be efficiently detected from the air with good impedance matching. The shape of the horn is not limited to a linear shape, but may be a non-linear shape, a curved shape, a quadratic curved shape, a parabolic shape, a stepped shape, or the like.

  In the resonator 60, two concave portions 5 and 6 are formed, and a convex portion 7 is formed between the two concave portions 5 and 6. A protrusion 8 is formed at a substantially central portion of the protrusion 7 of the semiconductor layer 91a, and an active element 90 is disposed below the protrusion 8 so as to be sandwiched between the first electrode 4a.

The length L1 of the resonator 60 is, for example, about 30 μm or less. The length of the protrusion 8 is, for example, about 6 μm or less. Further, the width of the recesses 5 and 6 (the distance between the first electrode 4 and the second electrode 2) is, for example, about 4 μm. The dimension of the active element 90 is, for example, about 1.4 μm ² . However, the size of the active element 90 is not limited to this value, and may be, for example, about 5.3 μm ² or less. The size of each part of the resonator 60 is not limited to the above dimensions, and is appropriately set in design according to the frequency of the terahertz electromagnetic wave to be received.

  Further, as shown in FIG. 31, compared with the distance between the first electrode 4 and the second electrode 2 in the waveguide 70, the first electrode 4 and the second electrode in the portion where the resonator 60 is formed. The interval between the electrodes 2 is narrow.

  The MIM reflector 50 is disposed at the closing portion on the opposite side of the opening of the resonator 60. Due to the laminated structure of the metal / insulator / metal MIM reflector 50, the first electrode 4 and the second electrode 2 are short-circuited in high frequency. Further, the MIM reflector 50 has an effect that it can reflect a high frequency while being open in terms of direct current.

  Each of the first electrode 4 (4a, 4b, 4c) and the second electrode 2, 2a has, for example, an Au / Pd / Ti metal laminated structure, and the Ti layer is in contact with the insulator substrate 10. This is a buffer layer for improving the resistance. The thickness of each part of the first electrodes 4a, 4b, 4c and the second electrodes 2, 2a is, for example, about several hundred nm, and as shown in FIGS. 33 (a) and 33 (b) as a whole. A flattened laminated structure is obtained. Note that both the first electrode 4 and the second electrode 2 can be formed by a vacuum evaporation method, a sputtering method, or the like.

  More specifically, the first electrode 4a and the first electrode 4c are made of, for example, Au / Pd / Ti, and the first electrode 4b is made of, for example, Au / Ti. The second electrode 2 is made of, for example, Au / Pd / Ti, and the second electrode 2a is made of, for example, Au / Ti.

  Note that the Ti layer forming the surface layer of the first electrode 4b is desirably removed in order to reduce the contact resistance when the extraction electrode is formed by the bonding wire 12b. Similarly, the Ti layer forming the surface layer of the second electrode 2a is desirably removed in order to reduce the contact resistance when the extraction electrode is formed by the bonding wire 12a.

The insulating layer 3 can be formed of, for example, a SiO ₂ film. In addition, a Si ₃ N ₄ film, a SiON film, a HfO ₂ film, an Al ₂ O ₃ film, or the like can be applied. The thickness of the insulating layer 3 can be determined in consideration of the geometric plane size of the MIM reflector 50 and the required capacitor value in terms of circuit characteristics, and is, for example, about several tens nm to several hundreds nm. . The insulating layer 3 can be formed by a CVD method or a sputtering method.

Similarly, the interlayer insulating film 9 can be formed of, for example, a SiO ₂ film. In addition, a Si ₃ N ₄ film, a SiON film, a HfO ₂ film, an Al ₂ O ₃ film, or the like can be applied. As shown in FIG. 33A, the thickness of the interlayer insulating film 9 is such that the total thickness of the second electrode 2a and the interlayer insulating film 9 is approximately the same as the thickness of the first electrode 4. Is set to The interlayer insulating film 9 can be formed by a CVD method or a sputtering method.

  The insulator substrate 10 is preferably made of a substrate having a lower dielectric constant than that of the semiconductor layer 91a in order to detect radio waves efficiently. As the insulating substrate 10 made of a low dielectric constant material, for example, a polyimide resin substrate, a Teflon (registered trademark) substrate, or the like can be applied. The thickness of the insulator substrate 10 is, for example, about 200 μm.

In the terahertz oscillation detecting element of the second modification, since the upper side is air, the relative dielectric constant ε _air = 1. When a polyimide resin substrate is used as the insulator substrate 10, since the relative permittivity ε _poly = 3.5 of the polyimide resin, the ratio of the radiated radio wave below the insulator substrate 10 to the total radiated radio wave is ε _poly ^3/2 / (ε _air ^3/2 + ε _poly ^3/2 ) = 0.87. That is, about 87% of the entire radiated radio wave is radiated from the insulator substrate 10 side, and the radio wave radiated laterally through the horn opening 80 is relatively increased.

Further, when a Teflon (registered trademark) resin substrate is used as the insulator substrate 10, since the relative permittivity ε _tef of the Teflon (registered trademark) is 2.1, the insulator substrate 10 is below the insulator substrate 10 with respect to the entire radiated radio wave. The ratio of the radiated radio wave is represented by ε _tef ^3/2 / (ε _air ^3/2 + ε _tef ^3/2 ) = 0.75. That is, about 75% of the entire radiated radio wave is emitted to the insulator substrate 10 side, and the radio wave radiated laterally through the horn opening 80 relatively increases.

The MIM reflector 50 has a structure in which an insulating layer 3 is interposed between the first electrode 4a and the second electrode 2 as shown in FIG. Further, as is clear from FIG. 33B, the active element 90 made of RTD is disposed on the insulator substrate 10 via the first electrode 4a. The first electrode 4a is disposed in contact with the n ⁺ GaInAs layer 91b of the RTD. The second electrode 2 is disposed in contact with the n ⁺ GaInAs layer 91a of the RTD. Further, the first electrode 4 (4b, 4c) is disposed so as to extend on the insulator substrate 10.

Thus, since the 1st electrode 4 is extended and arrange | positioned on the insulator board | substrate 10, the 1st electrode 4 and the 2nd electrode 2 are not mutually short-circuited, but RTD. A predetermined DC bias voltage can be applied between the n ⁺ GaInAs layer 91a and the n ⁺ GaInAs layer 91b.

  Note that a bonding wire 12b is connected to the first electrode 4, a bonding wire 12a is connected to the second electrode 2a, and a DC power source is connected between the first electrode 4 and the second electrode 2a. 15 is connected. In addition, a resistor (not shown) for preventing parasitic oscillation is connected between the first electrode 4 and the second electrode 2a.

  In the structure of the terahertz oscillation detecting element according to the modified example 2, the insulator substrate 10 is pasted directly on the first electrode 4 and on the second electrode 2 via the interlayer insulating film 9, and the semiconductor substrate 1 is removed by etching. The structure turned upside down after the process is represented as shown in FIGS. 33 (a) and 33 (b). As shown in FIGS. 33A and 33B, in the terahertz oscillation detecting element according to the second modification, the semiconductor layer 91a is disposed on the second electrode 2, but the second electrode 2a is also formed. Since it is exposed, an electrode extraction process such as wire bonding can be easily performed on the second electrode 2a.

  In the method for manufacturing the terahertz oscillation detection element according to Modification 2, as shown in FIGS. 15A and 15B, the width of the semiconductor layer 91a is formed by patterning after the semiconductor layer 91a is formed on the semiconductor substrate 1. And the pattern width of the second electrode 2 formed on the semiconductor layer 91a is narrowed. In the remaining portion, a second electrode 2a is formed which is connected to the second electrode 2 and has a predetermined width and is relatively thick. As a result, as shown in FIGS. 15A and 15B, a structure in which the second electrode 2a is in contact with the semiconductor substrate 1 is obtained.

  Next, as shown in FIGS. 33 (a) and 33 (b), the insulator substrate 10 is pasted directly on the first electrode 4 and on the second electrode 2 via the interlayer insulating film 9, A vertically inverted structure after the semiconductor substrate 1 is removed by etching is obtained.

  Next, as shown in FIG. 31, the bonding wire 12b is connected to the first electrode 4, and the bonding wire 12a is connected to the second electrode 2a, whereby the electrode is taken out.

  The semiconductor substrate 1 is formed of, for example, a semi-insulating InP substrate and has a thickness of about 600 μm, for example. As the etching solution for the InP substrate, for example, a hydrochloric acid-based etching solution can be applied.

  In the terahertz oscillation detection element of Modification 2, a schematic bird's-eye view structure after the step of attaching the insulator substrate 10 having a thickness d to the sample surface and removing the semiconductor substrate by etching is expressed as shown in FIG. A schematic bird's-eye view structure seen from the back surface of FIG. 34 is expressed as shown in FIG. As is apparent from FIG. 34, the first electrode 4 is directly attached to the insulator substrate 10. The second electrodes 2 and 2a are not shown in FIG. 34, but as shown in FIGS. 33A and 33B, the second electrodes 2 and 2a are formed on the insulator substrate 10 via the interlayer insulating film 9. It is pasted. The detailed structure of FIG. 34 corresponds to FIG.

  A schematic cross-sectional structure of a resonant tunneling diode (RTD) that can be applied to the active element 90 as a terahertz oscillation detecting element of Modification 2 is expressed in the same manner as in FIG. Moreover, the schematic cross-sectional structure of the modification is represented similarly to FIG.16 (b). Further, an integrated structure of the terahertz detection element RTD (D) and the terahertz oscillation element RTD (O) formed in the same manufacturing process is expressed in the same manner as FIG.

  FIG. 16 and FIG. 17 are structural examples arranged on the semiconductor substrate 1, but after the insulator substrate 10 is attached to the first electrode 4a in a subsequent process, the semiconductor substrate 1 is removed by etching. Is done. Therefore, FIG. 16 and FIG. 17 correspond to a schematic cross-sectional structure in the vicinity of the active element 90 just before the insulator substrate 10 is attached.

  As described above, the active element 90 is typically an RTD, but other diodes or transistors may be used. As other active elements, for example, TUNETTT diodes, IMPATT diodes, GaAsFETs, GaN-based FETs, HEMTs, HBTs, and the like can be applied.

  An example of a three-dimensional electromagnetic field simulation result in the XYZ-axis direction of the terahertz oscillation detection element of Modification 2 is expressed as shown in FIG. It can be seen that the Y-axis direction is the output direction of radio waves, and extremely good directivity is obtained. The example of FIG. 36 is a result of forming the insulator substrate 10 with a polyimide substrate having a thickness d = 200 nm and setting the oscillation frequency f = 0.5 THz in the terahertz oscillation element of the modification 2 shown in FIGS. 34 and 35. It is.

  According to the terahertz oscillation detecting element of the modification example 2, by using an insulator substrate having a low dielectric constant, the directivity in the lateral direction can be improved, and the directivity in the lateral direction with respect to the substrate can be oscillated with high efficiency. In addition, integration is easy.

-Modification 3 and Modification 4
The electrode pattern structure of the terahertz oscillation detection element of Modification Example 3 applicable to the transmission terahertz wave inspection apparatus according to the embodiment is expressed as shown in FIG. The pattern structure is expressed as shown in FIG. In FIGS. 37A and 37B, the SBD 30 connected between the first electrode 4 and the second electrode 2 is not shown, but is arranged in the same manner as in FIG.

  The electrode pattern structure of the terahertz oscillation detection element of Modification 3 is an example in which the second electrode 2 constituting the MIM reflector 50 is provided with a stub structure, and the electrode pattern structure of the terahertz detection element of Modification 4 is the MIM reflector 50. This is an example in which the first electrode 4 constituting the stub structure is provided. As is clear from FIG. 33A, since the semiconductor layer 91a is disposed on the second electrode 2, in FIG. 37A and FIG. 37B, the semiconductor layer 91a is displayed. However, the pattern of the second electrode 2 is arranged in the same pattern shape under the semiconductor layer 91a.

  That is, as shown in FIG. 37A, the second electrode 2 includes a plurality of stubs 13 </ b> A in a part constituting the MIM reflector 50.

  As shown in FIG. 37 (b), the first electrode 4 includes a plurality of stubs 13B in the portion constituting the MIM reflector 50.

  The plurality of stubs 13A or 13B may be arranged at equal intervals facing the resonator 60, or may be arranged so that the intervals thereof change.

  A combination of Modification 3 and Modification 4 described above may include a plurality of stubs on both the second electrode 2 and the first electrode 4.

  A resonant circuit is formed by providing a stub with a quarter of the wavelength of the electromagnetic wave in a part of the transmission line of the electromagnetic wave, drawing the electromagnetic wave into the stub, reflecting it, and returning it to the transmission line. I know. This is because only the electromagnetic wave having a wavelength four times the length of the stub out of the electromagnetic wave incident on the transmission line is equivalently short-circuited at the position of the stub, and this electromagnetic wave is reflected thereby. This is a phenomenon that leakage from the transmission line is reduced. According to this method, since the length of the stub is determined to be a quarter wavelength with respect to the wavelength of the input electromagnetic wave, for the electromagnetic wave in which the wavelength of the electromagnetic wave is four times the length of the stub. Although it can be strongly resonated and reflected, an electromagnetic wave having a wide bandwidth has little reflection effect.

  The length of the stub 13A of the third modification is not a quarter wavelength of the electromagnetic wave at the central portion of the incident electromagnetic wave having a band, but is shifted from the quarter. For example, when there is a frequency width to be reflected, it is desired to reflect by providing many stubs 13A having a length of 2 to 3 wavelengths for partially reflecting electromagnetic waves having a median frequency of the frequency width. It is possible to reflect electromagnetic waves having a frequency range in a wide range.

  Naturally, the reflectivity of the electromagnetic wave is smaller than that of the quarter wavelength, but still a considerable amount of reflection occurs compared to the case where there is no stub. And, there is an effect of uniformly reflecting a frequency having a certain band (electromagnetic wave having a certain wavelength width) as much as the resonance condition is loose. In addition, the multi-stage stubs have a length that is about half the wavelength of electromagnetic waves having a median frequency of the electromagnetic wave frequency to be reflected, thereby strengthening the interference between the reflections from each stub (Bragg). Reflection) occurs, the reflected waves are superimposed, and the reflectance becomes a large value of almost 100%. Depending on the length, number, and interval of the stubs, the reflected frequency width and the center frequency are comprehensively determined.

₀ the center wavelength of the electromagnetic wave lambda having a predetermined bandwidth, and the distance of the stub and lambda _0/2, the reflectivity can be obtained a wavelength range Δλ of electromagnetic waves close to 100%. At this time, the length of the stub, it is preferable to design the 2～3Ramuda ₀ or more. Further, when the width of the stub is half of the stub interval, a large reflectance close to 100% is obtained with a small number of about 5 to 10 stubs. When the stub width is other than that, it is necessary to increase the number of stubs in order to obtain a large reflectance, and the frequency width is also narrowed. However, these lengths are not limited and are defined in terms of design in relation to the reflected bandwidth.

  In the third modification, the leaked electromagnetic wave is reflected by the stub 13A and the MIM reflector and returned to the resonator 60 side. Since the reflected electromagnetic wave is emitted as a radiated radio wave, the electromagnetic wave radiated from the active element 90 has a high output.

  Also in the modified example 4, since the operation of the stub 13B is the same as that of the stub 13A, a duplicate description is omitted.

  By providing multistage stubs on both the second electrode 2 and the first electrode 4, it is possible to obtain the same large reflectivity with about half the number of stubs as compared with the case of only one. In addition, the degree of freedom in design when determining the frequency width and center frequency can be increased, which is extremely effective in design. Note that the length, number, and interval of the stubs attached to both the second electrode 2 and the first electrode 4 are not necessarily equal, and can be freely changed in design.

  According to the terahertz oscillation detecting elements of the third and fourth modifications, the directivity in the lateral direction is improved by using an insulating substrate having a low dielectric constant, so that high efficiency and high output can be achieved. Radiation can be radiated with high directivity, and integration is easy.

  According to the terahertz oscillation detection elements of the modification 3 and the modification 4, the directivity in the lateral direction is improved by using an insulating substrate having a low dielectric constant, and the stub structure is combined with the electrodes constituting the MIM reflector. It becomes possible to radiate electromagnetic waves more efficiently in the direction horizontal to the substrate and with higher directivity.

-Modification 5-
A schematic plane configuration of the electrode pattern structure of the terahertz oscillation detection element of the modification 5 applicable to the transmission terahertz wave inspection apparatus according to the embodiment is expressed as shown in FIG.

  Also in the terahertz oscillation detecting element according to the modified example 5, the configurations of the first electrode 4 (4a, 4b, 4c), the second electrode 2, 2a, the MIM reflector 50, the resonator 60, and the active element 90 are modified example 2. In the following, redundant description is omitted.

  As shown in FIG. 38, the terahertz oscillation detection element of Modification 5 includes an insulator substrate 10, a first electrode 4 (4a, 4b, 4c) disposed on the insulator substrate 10, and a first electrode. Insulating layer 3 (FIG. 31) disposed on 4a (FIG. 31), interlayer insulating film 9 (FIG. 31) disposed on insulator substrate 10, and first insulating layer 3 disposed on interlayer insulating film 9 A second electrode 2, 2 a disposed opposite to the first electrode 4 via the insulating layer 3 with respect to the electrode 4 a, a semiconductor layer 91 a disposed on the second electrode 2, and an insulator A first slot line electrode 41 disposed adjacent to the first electrode 4 on the substrate 10 and opposite the first electrode 4 on the opposite side of the second electrode 2a; A second slot disposed adjacent to the second electrode 2a and opposite the second electrode 2a on the side opposite to the first electrode 4 The in-electrode 21, the MIM reflector 50 formed between the first electrode 4 a and the second electrode 2 with the insulating layer 3 interposed therebetween, and the first electrode facing the insulator substrate 10 adjacent to the MIM reflector 50. The resonator 60 disposed between the electrode 4 and the second electrode 2, the active element 90 disposed substantially at the center of the resonator 60, and the resonator 60 are adjacent to each other on the insulator substrate 10. A first waveguide 70 disposed between the first electrode 4 and the second electrode 2, and the first electrode 4 and the second electrode adjacent to the first waveguide 70 and opposed to the insulator substrate 10. A first horn opening 80 disposed between the electrodes 2, a second waveguide 71 disposed between the first electrode 4 and the first slot line electrode 41 opposed to each other on the insulator substrate 10, and a second conductor. The first electrode 4 and the first slot line electrode that are adjacent to the waveguide 71 and face the insulator substrate 10. A second horn opening 81 disposed between the first substrate 2, a second waveguide 2 a facing the insulator substrate 10, a third waveguide 72 disposed between the second slot line electrodes 21, and a third waveguide 72, a third horn opening 82 disposed between the second electrode 2 a and the second slot line electrode 21 facing on the insulator substrate 10, the first electrode 4 and the second electrode 2. And an SBD 30 connected therebetween.

  As in the second modification, the active element 90 is typically an RTD, but can be configured by other diodes or transistors. As other active elements, for example, TUNETTT diodes, IMPATT diodes, GaAsFETs, GaN-based FETs, HEMTs, HBTs, and the like can be applied.

  The horn openings 80 to 82 constitute an open horn antenna.

  In the terahertz oscillation detection element of Modification 5, as shown in FIG. 38, the width W4 of the slot line electrodes 21 and 41 at the output end is, for example, about 160 μm. As shown in FIG. 38, the width D20 of the horn opening 80, the width D10 of the horn openings 81 and 82, and the width W4 of the slot line electrodes 21 and 41 at the output end can be changed as appropriate.

  The waveguide 70 is disposed in the opening of the resonator 60.

  The MIM reflector 50 is disposed in a closed portion opposite to the opening of the resonator 60.

  In the portion constituting the MIM reflector 50, the second electrode 2 may include a plurality of stubs similar to those of the third modification shown in FIG. Similarly, in the portion constituting the MIM reflector 50, the second electrode 2 may include a plurality of stubs similar to those of the modified example 4 shown in FIG.

  In the above description, the plurality of stubs may be arranged at equal intervals facing the resonator 60, or may be arranged so that the intervals change.

  The insulator substrate 10 is preferably made of a substrate having a lower dielectric constant than that of the semiconductor layer 91a in order to detect radio waves efficiently in the lateral direction and with high directivity. As the insulator substrate 10 made of a low dielectric constant material, for example, a polyimide resin substrate, a Teflon (registered trademark) substrate, or the like can be applied as in the first embodiment.

  When a polyimide resin substrate is used as the insulator substrate 10, about 87% of the total received radio waves are detected from the insulator substrate 10 side, and the received radio waves detected from the lateral direction through the horn opening 80 are The relatively increasing point is the same as in the second modification.

  When a Teflon (registered trademark) resin substrate is used as the insulator substrate 10, about 75% of the entire radiated radio wave is emitted to the insulator substrate 10 side as in the second modification, and the horn opening portion. The radio wave radiated from the lateral direction via 80 is relatively the same as in the second modification example in that it increases relatively.

  In the terahertz oscillation detecting element according to the modified example 5, a pair of tapered shapes having the same shape is formed on both sides of the tapered slot antenna including the first electrode 4 and the second electrode 2 connected to the active element 90. By arranging the slot line electrodes 41 and 21, the directivity of the detected radio wave is further improved as compared with the second modification.

  According to the terahertz oscillation detecting element of the fifth modification, a pair of tapered slot line electrodes 41 and 21 are arranged in parallel on both sides of the tapered slot antenna including the first electrode 4 and the second electrode 2. As a result, even if the tapered slot antenna is integrated on the insulator substrate 10, the influence of the insulator substrate 10 can be suppressed and sufficient radiation wave directivity can be obtained.

  The electric field spread from the tapered slot antenna composed of the first electrode 4 and the second electrode 2 in the center is drawn into a pair of slot line electrodes 41, 21 provided on both sides, and the slot line electrodes 41, 21 And is returned to the first electrode 4 and the second electrode 2 at the center. At this time, standing waves are formed in the first electrode 4, the second electrode 2, and the slot line electrodes 41, 21 in the center, and electromagnetic waves are received inside by the reflected electric field. The radiation electromagnetic fields from the first electrode 4 and the second electrode 2 at the center and the pair of slot line electrodes 41 and 21 interfere with each other, thereby improving the directivity of the radiation electromagnetic wave.

  According to the terahertz oscillation detecting element of the fifth modification, the directivity in the lateral direction is improved by using an insulating substrate having a low dielectric constant, and the standing wave is effectively generated by arranging the slot line electrodes in parallel. Accordingly, it is possible to radiate with high directivity in the lateral direction with respect to the substrate with higher efficiency and higher output, and integration is easy.

-Modification 6-
A schematic planar configuration of the electrode pattern structure of the terahertz oscillation detection element of the modification 6 applicable to the transmission type terahertz wave inspection apparatus according to the embodiment is expressed as shown in FIG.

  Also in the terahertz oscillation detection element of the modification 6, the first electrode 4, the second electrode 2, the MIM reflector 50, the resonator 60, the active element 90, the first slot line electrode 41, and the second slot line electrode 21 Since the configuration is the same as that of the second embodiment, redundant description will be omitted below.

  As shown in FIG. 36, the terahertz detection element of Modification 6 further includes a pair of slot line electrodes 22 and 42 arranged in parallel to the electrode pattern configuration of Modification 5 shown in FIG. . That is, the third slot line electrode 42 disposed on the insulator substrate 10 adjacent to the first slot line electrode 41 and opposite to the first electrode 4 and facing the first slot line electrode 41; A fourth slot line electrode 22 disposed adjacent to the second slot line electrode 21 on the insulator substrate 10 and opposite to the second slot line electrode 21 on the opposite side of the second electrode 2a; A fourth waveguide 74 disposed between the first slot line electrode 41 and the third slot line electrode 42 facing on the substrate 10, and a first waveguide facing the insulator substrate 10 adjacent to the fourth waveguide 74. A fourth horn opening 84 disposed between the first slot line electrode 41 and the third slot line electrode 42, and between the second slot line electrode 21 and the fourth slot line electrode 22 facing on the insulator substrate 10. The fifth waveguide 73 disposed and the fifth horn opening disposed between the second slot line electrode 21 and the fourth slot line electrode 22 facing the insulator substrate 10 adjacent to the fifth waveguide 73. Part 83. In FIG. 39, the SBD 30 connected between the first electrode 4 and the second electrode 2 is not shown.

  The insulator substrate 10 is preferably made of a substrate having a lower dielectric constant than that of the semiconductor layer 91a in order to radiate radio waves efficiently in the lateral direction and with high directivity. As the insulator substrate 10 made of a low dielectric constant material, for example, a polyimide resin substrate, a Teflon (registered trademark) substrate, or the like can be applied as in the first embodiment.

  In the configuration of FIG. 39, the directivity is further improved by further arranging a pair of slot line electrodes 22 and 42 in parallel outside the slot line electrodes 21 and 41.

  According to the terahertz oscillation detecting element of the modified example 6, the horizontal directionality is improved by using an insulating substrate having a low dielectric constant, and standing waves are effectively arranged by arranging two pairs of slot line electrodes in parallel. Therefore, it is possible to radiate with high directivity in the lateral direction with respect to the substrate with high efficiency and high output, and integration is easy.

  According to the terahertz oscillation detecting element applicable to the transmission type terahertz wave inspection apparatus according to the embodiment, the terahertz electromagnetic wave is oscillated and detected by a single electronic device having a parallel configuration of the resonant tunneling diode and the SBD. The terahertz electromagnetic wave can be detected and oscillated with high sensitivity and low noise.

  According to the terahertz oscillation detection element applicable to the transmission type terahertz wave inspection apparatus according to the embodiment, the transmitter and the detector are dramatically more than the conventional technique by combining with the terahertz detection element that can be manufactured in the same process. Therefore, it is possible to provide a wireless transmission / reception system of terahertz electromagnetic waves with high sensitivity and low noise.

  Further, since the terahertz oscillation element (RTD) applicable to the transmission terahertz wave inspection apparatus according to the embodiment can be used as a terahertz detection element, the same element functions as an oscillation element or a detection element. The device can be configured.

  According to the present invention, it is possible to provide a transmission type terahertz wave inspection apparatus capable of determining the number of sheets based on the magnitude of attenuation by paper by using RTD and transmission of terahertz waves. .

[Other embodiments]
As described above, the transmission-type terahertz wave inspection apparatus according to the embodiment has been described. However, it is understood that the discussion and the drawings that form a part of this disclosure are exemplary and limit the present invention. Should not. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  As described above, the present invention includes various embodiments not described herein.

  The transmission terahertz wave inspection apparatus of the present invention can be applied to a wide range of fields such as paper inspection, cash voucher inspection, and counterfeit bill inspection.

DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate 2, 2a ... 2nd electrode 3 ... Insulating layer 4, 4a, 4b, 4c ... 1st electrode 5, 6 ... Concave part 7 ... Convex part 8 ... Protrusion part 9 ... Interlayer insulating film 10 ... Insulator Substrate 13A, 13B ... Stub 15 ... DC power supply 21, 22, 41, 42 ... Slot line electrode 30 ... Schottky barrier diode (SBD)
50 ... MIM reflector 60 ... Resonators 70, 71, 72, 73, 74 ... Waveguides 80, 81, 82, 83, 84 ... Horn opening 90 ... Active element 91a ... Semiconductor layer 100 ... Oscillator 200 ... Detector 300 ... Paper 400 ... Beam 500 ... Support stand

Claims (18)

An oscillator including a terahertz oscillation element;
A detector comprising a terahertz detection element;
And a paper disposed between the oscillator and the detector, and the terahertz detection element detects a transmitted terahertz wave obtained by transmitting the terahertz wave radiated from the terahertz oscillation element through the paper. A transmission type terahertz wave inspection apparatus, wherein the number of papers is determined based on the magnitude of attenuation by the papers. The terahertz oscillation element and the terahertz detection element are:
A semiconductor substrate;
A second electrode disposed on the semiconductor substrate;
An insulating layer disposed on the second electrode;
A first electrode disposed with respect to the second electrode through the insulating layer and disposed on the semiconductor substrate so as to face the first electrode;
An MIM reflector formed between the first electrode and the second electrode across the insulating layer;
A resonator disposed between the first electrode and the second electrode facing the semiconductor substrate adjacent to the MIM reflector;
An active element disposed substantially in the center of the resonator;
A waveguide disposed between the first electrode and the second electrode facing the semiconductor substrate adjacent to the resonator;
2. The transmission type according to claim 1, further comprising: a horn opening disposed between the first electrode and the second electrode facing the semiconductor substrate adjacent to the waveguide. Terahertz wave inspection device.   The transmission terahertz wave inspection apparatus according to claim 2, further comprising a Schottky barrier diode connected between the first electrode and the second electrode. The terahertz oscillation element and the terahertz detection element are:
An insulator substrate;
A first electrode disposed on the insulator substrate;
An insulating layer disposed on the first electrode;
An interlayer insulating film disposed on the insulator substrate;
A second electrode disposed on the interlayer insulating film and disposed opposite to the first electrode via the insulating layer with respect to the first electrode;
A semiconductor layer disposed on the second electrode;
An MIM reflector formed between the first electrode and the second electrode across the insulating layer;
A resonator disposed between the first electrode and the second electrode facing the insulator substrate adjacent to the MIM reflector;
An active element disposed substantially in the center of the resonator;
A waveguide disposed between the first electrode and the second electrode facing the insulator substrate adjacent to the resonator;
2. The transmission according to claim 1, further comprising: a horn opening disposed between the first electrode and the second electrode facing the insulator substrate adjacent to the waveguide. Type terahertz wave inspection equipment.   The transmission terahertz wave inspection apparatus according to claim 4, further comprising a Schottky barrier diode connected between the first electrode and the second electrode. The terahertz oscillation element and the terahertz detection element are:
An insulator substrate;
A first electrode disposed on the insulator substrate;
An insulating layer disposed on the first electrode;
An interlayer insulating film disposed on the insulator substrate;
A second electrode disposed on the interlayer insulating film and disposed opposite to the first electrode via the insulating layer with respect to the first electrode;
A semiconductor layer disposed on the second electrode;
A first slot line electrode disposed on the insulator substrate adjacent to the first electrode and opposite to the second electrode and facing the first electrode;
A second slot line electrode disposed on the insulator substrate adjacent to the second electrode and opposite to the first electrode and facing the second electrode;
An MIM reflector formed between the first electrode and the second electrode across the insulating layer;
A resonator disposed between the first electrode and the second electrode facing the insulator substrate adjacent to the MIM reflector;
An active element disposed substantially in the center of the resonator;
A first waveguide disposed between the first electrode and the second electrode facing the insulator substrate adjacent to the resonator;
A first horn opening disposed between the first electrode and the second electrode facing the insulator substrate adjacent to the first waveguide;
A second waveguide disposed between the first electrode and the first slot line electrode facing each other on the insulator substrate;
A second horn opening disposed between the first electrode and the first slot line electrode facing the insulator substrate adjacent to the second waveguide;
A third waveguide disposed between the second electrode and the second slot line electrode facing each other on the insulator substrate;
The third horn opening disposed between the second electrode facing the insulator substrate and the second slot line electrode adjacent to the third waveguide. 1. The transmission terahertz wave inspection apparatus according to 1.   The transmission terahertz wave inspection apparatus according to claim 6, further comprising a Schottky barrier diode connected between the first electrode and the second electrode. The terahertz oscillation element and the terahertz detection element are:
A third slot line electrode disposed on the insulator substrate adjacent to the first slot line electrode and opposite the first slot line electrode to face the first slot line electrode;
A fourth slot line electrode disposed adjacent to the second slot line electrode on the insulator substrate and opposite to the second slot line electrode on the opposite side of the second electrode;
A fourth waveguide disposed between the first slot line electrode and the third slot line electrode facing each other on the insulator substrate;
A fourth horn opening disposed between the first slot line electrode and the third slot line electrode facing the insulator substrate adjacent to the fourth waveguide;
A fifth waveguide disposed between the second slot line electrode and the fourth slot line electrode facing each other on the insulator substrate;
The fifth horn opening disposed between the second slot line electrode and the fourth slot line electrode facing the insulator substrate adjacent to the fifth waveguide. Item 8. The transmission terahertz wave inspection apparatus according to Item 6 or 7.   The semiconductor substrate is thinned in a region where the first electrode and the second electrode forming the resonator, the waveguide, and the horn opening are disposed. The transmission terahertz wave inspection apparatus according to claim 2.   3. The active element is any one of a resonant tunnel diode, a tannet diode, an impat diode, a GaAs field effect transistor, a GaN FET, a high electron mobility transistor, and a heterojunction bipolar transistor. The transmission type terahertz wave inspection apparatus according to any one of?   9. The transmission terahertz wave inspection apparatus according to claim 2, wherein the horn opening constitutes an opening horn antenna. 10.   The transmission terahertz wave inspection apparatus according to claim 4, wherein the insulator substrate is made of a substrate having a lower dielectric constant than that of the semiconductor layer.   The transmission terahertz wave inspection apparatus according to claim 2, wherein the waveguide is disposed in an opening of the resonator.   9. The transmission terahertz wave inspection apparatus according to claim 2, wherein the MIM reflector is disposed in a closed portion opposite to the opening of the resonator. 10.   9. The transmission terahertz wave inspection apparatus according to claim 2, wherein the second electrode includes a plurality of stubs in a portion constituting the MIM reflector. 10.   9. The transmission terahertz wave inspection apparatus according to claim 2, wherein the first electrode includes a plurality of stubs in a portion constituting the MIM reflector. 10.   The transmission type terahertz wave inspection apparatus according to claim 15, wherein the plurality of stubs are arranged at equal intervals so as to face the resonator. The transmission type terahertz wave inspection device according to claim 15 or 16, wherein the plurality of stubs are arranged so as to face the resonator and the intervals thereof change.