JP2018182422A - Substrate integrated waveguide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To mitigate a tradeoff between an upper limit of a frequency of an electromagnetic wave being able to propagate and mechanical strength of a substrate in a substrate integrated waveguide.SOLUTION: A substrate integrated waveguide comprises: a substrate 100; metal layers 101a, 102; a substrate penetrating via 103 that connects between the metal layer 101a and the metal layer 102; and a plurality of stubs 104 that are formed on the metal layer 101a to be extended in a direction being different from a propagating direction, from a place between adjacent substrate penetrating vias 103 toward outside in each column of substrate penetrating vias 103. Each stub 104, the substrate 100 and the metal layer 102 constitutes a line in which an electromagnetic wave leaking through the place between the substrate penetrating vias 103 from the substrate 100 propagates. When a wavelength of a desired electromagnetic wave to be desired to transmit in the substrate 100 is defined as λ, the length of the line is λ/4+n×λ/2 (n is a non-negative integer).SELECTED DRAWING: Figure 1

Description

  The present invention relates to circuit technology dealing with high frequency electrical signals, and in particular to substrate integrated waveguides.

  A coaxial line or a metal waveguide is mainly used as a transmission medium for high frequency electrical signals. In general, coaxial lines have low-pass characteristics, so the propagation loss is large in a high frequency band, and they are not suitable for transmission of an ultrahigh frequency electrical signal exceeding 100 GHz. On the contrary, metal waveguides have high-pass characteristics and small propagation loss in the high frequency band, so they are suitable for transmission media of ultra high frequency electrical signals exceeding 100 GHz.

  A substrate integrated waveguide (SIW) is a waveguide-like transmission line formed on a dielectric or semiconductor substrate using an integrated circuit process. Like metal waveguides, SIW is characterized by small propagation loss in the high frequency band and is easy to integrate with other functional circuits by an integrated circuit process, so integration using ultra high frequency electrical signals of 100 GHz or more It is suitable for high frequency wiring in a circuit (non-patent document 1).

As shown in FIG. 11, the SIW confines the electromagnetic wave in the vertical direction by the metal layers 101 and 102 formed on the upper and lower surfaces of the substrate 100, and passes through the electromagnetic wave by the through substrate via (TSV) 103. By confining the direction, it is possible to form in the substrate 100 the same propagation mode (TE ₁₀ mode etc.) as the metal waveguide.

The arrangement interval of the TSVs 103 in the direction perpendicular to the propagation direction of the electromagnetic wave (Wa in FIG. 11) is a parameter corresponding to the width of the waveguide in the metal waveguide. The value of the arrangement interval Wa is set to allow propagation of the TE ₁₀ mode at a desired frequency. Further, the value of the arrangement interval (Wb in FIG. 11) of the TSVs 103 in the propagation direction of the electromagnetic wave needs to be set so that the confinement of the electromagnetic wave in the in-plane direction of the substrate 100 is sufficiently strong. If the arrangement interval Wb is not sufficiently smaller than the wavelength of the electromagnetic wave, the electromagnetic wave can not be confined in the SIW, and the SIW can not be used as a transmission line.

As described above, in order to propagate an electromagnetic wave in SIW, it is necessary to set the interval Wb of the TSV 103 in the propagation direction of the electromagnetic wave to a value smaller than the wavelength of the electromagnetic wave to be handled. When the spacing Wb of the TSVs 103 in the propagation direction becomes more than one-quarter of the wavelength λg in the transmission line of TE ₁₀ mode that propagates SIWs, the gap of the TSVs 103 in the propagation direction starts to have the same function as the slit of the leaky wave antenna It is thought that electromagnetic waves leak to the outside of SIW. In order to design an SIW, it is necessary to determine the interval Wb of the TSVs 103 in the propagation direction with less electromagnetic wave leakage. For that purpose, as described above, the value of the wavelength λg in the TE ₁₀ mode transmission line propagating the SIW may be grasped, and the interval Wb of the TSVs 103 in the propagation direction may be set to a value equal to or smaller than one quarter. The wavelength λg in the transmission line is calculated by the following equation, assuming that the effective dielectric constant at each frequency of the TE ₁₀ mode is ε: λg = c / (ε ^1/2 f) (1)

Here, c represents the speed of light and f represents the frequency. FIG. 12 shows a calculation result of a quarter (λg / 4) of the wavelength in the transmission line of the TE ₁₀ mode propagating the SIW. In this calculation, for the sake of simplicity, the metal layers 101 and 102 on the upper surface and the lower surface of the substrate are ideal conductors, and the sidewall of the SIW is a metal plane made of an ideal conductor instead of the TSV 103. Further, it is assumed that InP (dielectric constant 12.3) is used as the material of the substrate 100, and the thickness of the substrate 100 is 50 μm. The width of the SIW was 180 μm.

  As is clear from the equation (1), λg / 4 is smaller as the frequency of the electromagnetic wave to be handled is higher. As can be seen from FIG. 12, λg / 4 takes an extremely small value of 100 μm or less at 290 GHz or more. However, if the space Wb of the TSVs 103 is reduced, the TSVs 103 are densely arranged on the substrate 100, which causes a problem that the mechanical strength of the substrate 100 is reduced. Therefore, in the interval Wb of the TSVs 103, there is a process lower limit value for securing the mechanical strength of the substrate 100.

  In particular, since compound semiconductor substrates such as InP and GaAs are easily broken, the lower limit value of the distance Wb between the TSVs 103 needs to be set to a value about twice or more larger than that of other semiconductor substrates such as Si. Therefore, when manufacturing SIW using 50 μm thick InP used in the calculation of FIG. 12, it is practically necessary to set the interval Wb of the TSV 103 in the electromagnetic wave propagation direction to 100 μm or more. Therefore, it is assumed that it is difficult to produce an SIW capable of propagating an electromagnetic wave having a frequency of 290 GHz or more.

13, in SIW shown in FIG. 11 shows the calculation results of the pass characteristic S ₂₁ when the spacing Wb of the electromagnetic wave propagation direction TSV103 a parameter. The diameter of the TSVs 103 was 40 μm, and the arrangement interval Wa of the TSVs 103 in the direction perpendicular to the electromagnetic wave propagation direction was 180 μm. From FIG. 13, it can be understood that when the interval Wb of the TSVs 103 in the electromagnetic wave propagation direction becomes large, the passing characteristic of the SIW is degraded. With the increase of the interval Wb, the pass characteristic starts to deteriorate from the high region around 290 GHz. The interval Wb = 110 μm at which the transmission characteristics at 290 GHz significantly deteriorate substantially matches the value 100 μm at 290 GHz of λg / 4 calculated in FIG. As described above, it can be understood that in order to prevent the leakage of electromagnetic waves in SIW, the interval Wb needs to be set to λg / 4 or less.

  Moreover, the mode of propagation of the electromagnetic wave in 300 GHz in the case of Wb = 110 micrometers is shown in FIG. FIG. 14 shows the distribution of the electric field intensity [V / m], and the bright part shows the position where the electromagnetic intensity is high. It is clear from FIG. 14 that the cause of the deterioration in the passing characteristic of the SIW is the electromagnetic wave leakage from the gap of the TSV 103 in the propagation direction. As described above, in the case of using an InP substrate with a thickness of 50 μm, if the minimum value of the spacing Wb of the TSV 103 is about 100 μm, as a result, using an InP substrate with a thickness of 50 μm It can be said that it is impossible to make SIWs that can propagate to loss. In addition, if it is necessary to set the minimum value of the interval Wb of the TSV 103 to be twice or more the thickness of the substrate, the frequency of the electromagnetic wave that can be propagated without leakage by SIW is further reduced.

  From the above discussion, the problem in making SIW in high frequency band became clear. That is, in the conventional SIW, there is a problem that there is a tradeoff between the upper limit of the frequency of the propagating electromagnetic wave and the mechanical strength of the substrate (that is, the interval Wb of the TSVs 103 in the propagation direction).

D. Deslandes, et al., "Integrated microstrip and rectangular waveguide in planar form", IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS, Vol. 11, No. 2, 2001

  The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to alleviate the trade-off between the upper limit of the frequency of an electromagnetic wave that can be propagated by SIW and the mechanical strength of the substrate.

  The substrate integrated waveguide according to the present invention comprises a substrate made of a dielectric or a semiconductor, a first metal layer formed on the first surface of the substrate, and the substrate opposite to the first surface. A second metal layer formed on the second surface and the first metal layer and the second metal layer are periodically formed on the substrate so as to be arranged in two lines along the propagation direction of the electromagnetic wave. Extending in the direction different from the propagation direction from the locations between the plurality of first substrate through vias connecting the first substrate through vias adjacent in each row of the plurality of first substrate through vias. And a plurality of stubs formed in the first metal layer, each stub, the substrate, and the second metal layer are formed of the first and second metal layers and the second row of the first metal layer. Leakage from the substrate, surrounded by one through-substrate via, through the location between the first through-substrate via When the wavelength of the desired electromagnetic wave to be transmitted by the substrate is λ, the length of the line is λ / 4 + n × λ / 2 (n is a non-negative integer). It is said that.

In one configuration example of the substrate integrated waveguide according to the present invention, the plurality of stubs are formed so as to protrude outward from the first metal layer, and the line is formed of each stub and the substrate. And a second metal layer.
Further, in one configuration example of the substrate integrated waveguide according to the present invention, the plurality of stubs are separated from the connection portion with the first metal layer by the grooves formed around the first metal layer, respectively. The line is a coplanar line consisting of stubs, the substrate, the first metal layer, and the second metal layer.

In one configuration example of the substrate integrated waveguide according to the present invention, the tip of the line is grounded.
Further, in one configuration example of the substrate integrated waveguide according to the present invention, the plurality of stubs are formed to protrude outward from the first metal layer, and the respective tips of the plurality of stubs and The semiconductor device further comprises a plurality of second through-substrate vias connecting the second metal layer, and the line is a microstrip line consisting of each stub, the substrate, and the second metal layer, Is characterized in that it is grounded.
Further, in one configuration example of the substrate integrated waveguide according to the present invention, the plurality of stubs are connected to the first metal layer by a groove formed in the periphery and a tip portion on the opposite side to the connection portion. And the line is a coplanar line consisting of stubs, the substrate, the first metal layer, and the second metal layer, and the tip of the line is separated from the first metal layer. It is characterized in that it is grounded.

  According to the present invention, in each row of the first through substrate vias, the plurality of stubs are extended outward in a direction different from the propagation direction from the location between the adjacent first through substrate vias. By forming the metal layer and setting the length of the line consisting of each stub, the substrate and the second metal layer to λ / 4 + n × λ / 2 for the wavelength λ of the desired electromagnetic wave to be transmitted by the substrate, It becomes possible to propagate an electromagnetic wave of a frequency higher than that of the conventional substrate integrated waveguide without leakage. As a result, in the present invention, it is possible to ease the tradeoff between the upper limit of the frequency of the propagating electromagnetic wave of the substrate integrated waveguide and the mechanical strength of the substrate.

FIG. 1 is a plan view and a sectional view showing the structure of a substrate integrated waveguide according to a first embodiment of the present invention. FIG. 2 is a plan view showing an equivalent configuration of a substrate integrated waveguide according to a first embodiment of the present invention. FIG. 3 is a plan view and a sectional view showing the structure of a substrate integrated waveguide according to a second embodiment of the present invention. FIG. 4 is a plan view and a sectional view showing the structure of a substrate integrated waveguide according to a third embodiment of the present invention. FIG. 5 is a plan view and a sectional view showing the structure of a substrate integrated waveguide according to a fourth embodiment of the present invention. FIG. 6 is a perspective view showing a calculation model of a substrate integrated waveguide according to a fifth embodiment of the present invention. FIG. 7 is a view showing the pass characteristic of the substrate integrated waveguide according to the fifth embodiment of the present invention. FIG. 8 is a perspective view showing a calculation model of a substrate integrated waveguide according to a sixth embodiment of the present invention. FIG. 9 is a diagram showing the pass characteristic of the substrate integrated waveguide according to the sixth embodiment of the present invention. FIG. 10 is a plan view showing the configuration of a substrate integrated waveguide according to a seventh embodiment of the present invention. FIG. 11 is a perspective view showing the configuration of a conventional substrate integrated waveguide. FIG. 12 is a diagram showing the frequency dependency of the size of a quarter wavelength of the wavelength in the transmission line of TE ₁₀ mode propagating in the conventional substrate integrated waveguide. FIG. 13 is a diagram showing the pass characteristic of the substrate integrated waveguide when the distance between the through-substrate vias in the electromagnetic wave propagation direction is used as a parameter. FIG. 14 is a view showing propagation of electromagnetic waves in a conventional substrate integrated waveguide.

First Embodiment
Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 (A) is a plan view showing the configuration of the SIW according to the first embodiment of the present invention, FIG. 1 (B) is a sectional view taken along the line A-A of FIG. 1 (A), and FIG. It is a BB sectional drawing of 1 (A). The SIW of this embodiment includes a substrate 100 made of dielectric or semiconductor, a substrate upper surface metal layer 101 a formed on the first surface of the substrate 100, and a second surface opposite to the first surface of the substrate 100. The substrate lower surface metal layer 102 formed on the entire surface and the substrate upper surface metal layer 101a and the substrate lower surface metal layer 102 are periodically arranged in two lines along the electromagnetic wave propagation direction (left and right direction in FIG. 1A). And a plurality of TSVs 103 connecting the Hereinafter, the first surface and the second surface of the substrate 100 are referred to as “upper surface” and “lower surface”, respectively.

  As in the prior art, the electromagnetic wave propagates through the region of the substrate 100 surrounded by the substrate upper surface metal layer 101a, the substrate lower surface metal layer 102, and the two rows of TSVs 103. The difference between the conventional example and the present embodiment is that the direction from the electromagnetic wave propagation direction toward the outside of the SIW from the location between each of the plurality of TSVs 103 periodically arranged along the electromagnetic wave propagation direction (usually the electromagnetic wave propagation direction And a plurality of stubs 104 extending in a direction perpendicular to the above are formed on the outer surface of the substrate upper surface metal layer 101 a of each of the two rows of TSVs 103. The length in the extension direction of each stub 104 is set to a quarter length (λ / 4) of the wavelength λ of the desired electromagnetic wave to be propagated by the SIW. The planar shape of the substrate upper surface metal layer 101 a having such stubs 104 can be realized by processing the metal layer formed on the upper surface of the substrate 100.

  The reduction of electromagnetic wave leakage from SIW according to this embodiment can be described as follows. Looking at the portions of the stubs 104 (portions of the broken line 105 in FIG. 1C), the stubs 104, the substrate 100 and the substrate lower surface metal layer 102 constitute a microstrip transmission line. Therefore, by providing the transmission lines extending from the points between the TSVs 103, the electromagnetic waves leaked from the points between the TSVs 103 are coupled to the propagation mode of the transmission line. The coupled electromagnetic waves are reflected by the open end of the transmission line (the tip of the stub 104) and return to the SIW. At this time, since the length of the transmission line is set to λ / 4, the impedance when the transmission line side is viewed from the location between each TSV 103 is a short circuit at the wavelength λ.

  That is, in the present embodiment, as shown in FIG. 2, in the conventional SIW, an effect equivalent to arranging the TSV 106 between each TSV 103 can be obtained. As a result, in the present embodiment, the density of the TSVs 103 on the side walls of the SIW is equivalently improved, and the leakage of the electromagnetic wave can be prevented even at a higher frequency. As a result, in the present embodiment, the trade-off between the upper limit of the frequency of the electromagnetic wave capable of propagating SIW and the mechanical strength of the substrate (that is, the interval of the TSV 103 in the electromagnetic wave propagation direction) can be relaxed.

Second Embodiment
Next, a second embodiment of the present invention will be described. FIG. 3 (A) is a plan view showing the configuration of the SIW according to the second embodiment of the present invention, FIG. 3 (B) is a cross-sectional view taken along the line AA of FIG. 3 (A), and FIG. It is a BB sectional drawing of 3 (A), and the same code | symbol is attached | subjected to the structure same as FIG. 1 (A)-FIG.1 (C). In the first embodiment, the substrate upper surface metal layer 101a around each stub 104 is removed, but in this embodiment, each stub 104 is surrounded by the substrate upper surface metal layer 101b. A groove 107 from which the substrate upper surface metal layer 101b is removed is formed around the stub 104 except for the connection portion with the substrate upper surface metal layer 101b. As a result, the location excluding the connection portion between the stub 104 and the substrate upper surface metal layer 101 b is separated from the substrate upper surface metal layer 101 b by the groove 107.

  Looking at the portion of each stub 104 (the portion of the broken line 108 in FIG. 3C), the stub 104, the substrate upper surface metal layer 101b around the stub 104, the substrate 100, and the substrate lower surface metal layer 102 are coplanar type transmissions. It constitutes a track. With such a configuration, also in this embodiment, the same effect as that of the first embodiment can be obtained.

Third Embodiment
Next, a third embodiment of the present invention will be described. 4 (A) is a plan view showing the configuration of the SIW according to the third embodiment of the present invention, FIG. 4 (B) is a sectional view taken along the line A-A of FIG. 4 (A), and FIG. It is a BB sectional view of 4 (A), and the same numerals are given to the same composition as Drawing 1 (A)-Drawing 1 (C).

  In the SIW of this embodiment, as in the first embodiment, a direction different from the electromagnetic wave propagation direction from the location between each of the plurality of TSVs 103 periodically arranged along the electromagnetic wave propagation direction. Although a plurality of stubs 104 extending in the direction perpendicular to the electromagnetic wave propagation direction are formed on the substrate upper surface metal layer 101c, unlike the first embodiment, the tip of each stub 104 is a substrate via the TSV 109 It is short-circuited with the lower surface metal layer 102.

  The principle of this embodiment is as follows. An electromagnetic wave leaked from a point between each TSV 103 and coupled to the propagation mode of the transmission line consisting of the stub 104, the substrate 100, and the substrate lower surface metal layer 102 is reflected at the short end (the tip of the stub 104) of this transmission line. Then return to the SIW side. At this time, since the length of the transmission line is set to λ / 4, the impedance when the transmission line side is viewed from the location between each TSV 103 is open at the wavelength λ. Therefore, the electromagnetic waves can not leak into the substrate, and as a result, they are confined within the SIW and propagate the SIW.

  In the case of the present embodiment, the short circuit end is formed by connecting the substrate lower surface metal layer 102 (ground metal) and the end of the stub 104 by the TSV 109. Therefore, in the present embodiment, there is a concern that the mechanical strength of the substrate 100 may be reduced by the TSV 109. However, with some exceptions, this embodiment does not reduce the mechanical strength of the substrate 100.

As described above, the interval Wb between the TSVs 103 in the electromagnetic wave propagation direction needs to be set to a value that maintains the mechanical strength of the substrate 100. However, if the distance Wb is set to one-quarter or more of the wavelength λg in the transmission line of the mode in which the SIW is propagated, leakage of the electromagnetic wave from the SIW becomes remarkable and the SIW can not be used as a good transmission line. there were. Therefore, assuming that the minimum arrangement interval of the TSVs 103 in the electromagnetic wave propagation direction determined by the mechanical strength of the substrate 100 is Wmin, a good SIW without electromagnetic wave leakage can be manufactured by the usual design method if the following equation is satisfied. It is.
λg / 4 ≧ Wb ≧ Wmin (2)

The object of the present invention is that, since the frequency of the electromagnetic wave to be propagated is extremely high, the following equation (3) is satisfied even if the minimum arrangement interval is equal to Wmin when the interval Wb is equal to It is a case where strength and SIW characteristics can not be compatible.
Wb = Wmin ≧ λg / 4 (3)

In this embodiment, the distance between the TSV 109 disposed at the short-circuit end of the transmission line (microstrip line) consisting of the stub 104, the substrate 100 and the substrate lower surface metal layer 102 and the TSV 103 disposed at the sidewall of the SIW (FIG. The mechanical strength of the substrate 100 is reduced if a) in the above a) does not satisfy the following equation as in the equation (3).
a W Wb = Wmin (4)

However, it can be explained as follows that the interval a between the TSV 109 and the TSV 103 satisfies the equation (4) with some exceptions. In FIG. 4 (A), the following equation is established from the theorem of three squares.
a = ((λ / 4) ² + (Wb / 2) ² ) ^1/2 (5)

That is, the interval a between the TSV 109 and the TSV 103 is a monotonically increasing function with respect to the interval Wb of the TSV 103 in the electromagnetic wave propagation direction. Now, from the equation (3), since Wbλλg / 4, the following equation is established from this relationship and the equation (5).
a (((λ / 4) ² + (λg / 8) ² ) ^1/2 (6)

Here, if it can be proved that the following equation (7) holds, the equations (6) to (8) hold, and from this equation (8), the equation (3) and the equation (4), the interval a is The minimum value can be selected to be the same value as the interval Wb, and can be larger than the minimum arrangement interval Wmin of the TSVs 103 determined by the mechanical strength of the substrate 100.
λ ≧ λg (7)
a 5 5 ^1/2 λg / 8 = 0.2795 λg λ λg / 4 (8)

That equation (7) usually holds is explained as follows. Assuming that the frequency of the electromagnetic wave propagating through the SIW is f, the wavelength within the transmission line of the electromagnetic wave propagating through the SIW and the microstrip line can be written as follows.
λg = c / (ε _s ^1/2 f) (9)
λ = c / (ε _m ^1/2 f) (10)

Here, c is the speed of light in vacuum, ε _s is the effective relative permittivity of TE ₁₀ mode propagating SIW, and ε _m is the effective relative permittivity of the mode propagating microstrip line. The effective relative permittivity is represented by the average relative permittivity contained in the space where the propagation mode of the electromagnetic wave is present. In the case of SIW, since the propagation mode propagates through the substrate 100, the effective permittivity ε _s of the propagation mode substantially matches the relative permittivity ε _{sub of the} substrate 100. In the case of a microstrip line, the propagation mode propagates under the influence of the relative permittivity of both the substrate 100 and the upper cladding (usually air) made of a dielectric on the substrate. Therefore, assuming that the relative permittivity of the upper cladding is ε _clad , the effective relative permittivity ε _m of the mode propagating through the microstrip line takes an average value between the relative permittivity ε _sub and ε _clad .

In most cases, dielectrics such as alumina and semiconductors such as Si and InP are used as the substrate 100 of SIW. However, the dielectric constants of these dielectrics and semiconductors are as high as 9-12. On the other hand, the upper cladding is most often air (dielectric constant 1). Although the resin or the like other than air may be used as the upper clad in very rare cases, the relative dielectric constant of the resin is about 2-3, which is smaller than the relative dielectric constant of the substrate 100 of SIW. In such a case, the average relative dielectric constant ε _m is always smaller than the relative dielectric constant ε _sub of the substrate 100. As described above, since the effective relative permittivity ε _s of the TE ₁₀ mode propagating SIW is substantially equal to the relative permittivity ε _sub of the substrate 100, the following equation (11) is established as a result, and this equation (11) The equation (7) is established from the equation (9) and the equation (10).
ε _s > ε _m (11)

The only exception in which the equation (7) does not hold is only in the case of using a material with a relative dielectric constant higher than that of the substrate 100 in the upper cladding, but such a case hardly exists practically.
From the above discussion, according to the present embodiment, it is described that the leakage of the electromagnetic wave from the SIW can be prevented without impairing the mechanical strength of the substrate 100.

  In the first and second embodiments, the end of the transmission line added to the SIW is open, but there are cases where it is difficult to produce an ideal open end in a high frequency circuit. For example, when the circuit elements are densely arranged, it is conceivable that the circuit elements are arranged in the vicinity of the transmission line added to the SIW. In such a case, depending on the frequency of the electromagnetic wave to be handled, the parasitic capacitance between the adjacent circuit elements can not be ignored, and the end of the transmission line added to the SIW has characteristics different from the ideal opening. The case is also conceivable. In such a case, this embodiment may be used.

Fourth Embodiment
Next, a fourth embodiment of the present invention will be described. FIG. 5 (A) is a plan view showing the configuration of an SIW according to a fourth embodiment of the present invention, FIG. 5 (B) is a cross-sectional view taken along the line A-A of FIG. 5 (A), and FIG. It is a BB sectional view of 5 (A), and the same numerals are given to the same composition as Drawing 3 (A)-Drawing 3 (C).

  In the second embodiment, the tip of each stub 104 and the substrate upper surface metal layer 101d are separated by the groove 107, but in this embodiment, the tip of each stub 104 and the substrate upper surface metal layer 101d are separated. The groove separating the That is, the grooves 110 are formed in the substrate upper surface metal layer 101d on both sides of each stub 104 extending in a direction different from the electromagnetic wave propagation direction (normally, the direction perpendicular to the electromagnetic wave propagation direction). Each stub 104 is connected to the substrate upper surface metal layer 101 d at each (tip), and both sides of each stub 104 are separated from the substrate upper surface metal layer 101 d by the grooves 110.

  Looking at each stub 104, the stub 104, the substrate upper surface metal layer 101d around the stub 104, the substrate 100 and the substrate lower surface metal layer 102 constitute a coplanar transmission line, and the tip of the coplanar transmission line Is the short circuit end. With such a configuration, the same effect as that of the third embodiment can be obtained also in this embodiment.

  In any of the first to fourth embodiments, the phase rotation amount of the electromagnetic wave in the transmission line added to the SIW is 90 ° + 180 ° × n (n is a non-negative integer of 0, 1, 2,... ) Can prevent the leakage of electromagnetic waves from SIW. That is, the length of the transmission line (the length of the stub 104) is not limited to λ / 4, and may be λ / 4 + n × λ / 2. The definition of the length of such a transmission line is apparent from the nature of a general quarter-wave line.

Fifth Embodiment
Next, a fifth embodiment of the present invention will be described. This embodiment shows a specific example of the first embodiment and shows an example applied to SIW on an InP substrate. Since the basic configuration of the SIW is as described in the first embodiment, it will be described using the symbols of FIG. 1 (A) to FIG. 1 (C). The calculation model used in this example is shown in FIG. As in the calculation example of FIG. 13, the thickness T of the substrate 100 made of InP is 50 μm, and the dielectric constant of InP is 12.3. The width Wc of the SIW was 180 μm, and the diameter D of the TSV 103 was 40 μm. In addition, the interval Wb between the TSVs 103 in the electromagnetic wave propagation direction is set to 110 μm in which the passing characteristic of the SIW begins to deteriorate remarkably in FIG.

  In FIG. 6, the upper clad 111 formed so as to cover the substrate upper surface metal layer 101a is described. However, in practice, the characteristics of the SIW are calculated without the upper cladding 111 covering the substrate upper surface metal layer 101a. In other words, the characteristics of the SIW are calculated on the assumption that air of relative dielectric constant 1 is present as the upper cladding 111 on the substrate upper surface metal layer 101a. The calculation is performed with the same setting also for FIG. 13 shown above. In general, even if the upper cladding 111 has a dielectric constant lower than the dielectric constant of the substrate 100 constituting the SIW, the effects of the present invention are not lost.

  In the present example, a stub 104 having a length L in the stretching direction of 80 μm and a width Wd in the direction perpendicular to the stretching direction of 35 μm was added to the substrate upper surface metal layer 101a. That is, as described in the first embodiment, a microstrip transmission line with an open tip, which comprises the stub 104, the substrate 100, and the substrate lower surface metal layer 102, is added. The length L = 80 μm is equal to a quarter wavelength of the microstrip transmission line at 300 GHz.

The results of calculating the pass characteristics S ₂₁ of SIW using the model shown in FIG. 6 is shown in FIG. For comparison, in the conventional SIW shown in FIG. 11, it is also shown passing characteristic S ₂₁ in the case where the distance Wb = 110 [mu] m of electromagnetic wave propagation direction TSV103. 70 in Figure 7 indicates the pass characteristic S ₂₁ of a conventional SIW, 71 indicates a pass characteristic S ₂₁ of SIW in this embodiment.

  As apparent from FIG. 7, it can be seen that the remarkable deterioration of the passage characteristic observed at 290 GHz or more in the conventional SIW is improved in the present embodiment. In addition, it can be seen that the pass characteristic of this embodiment is better than that of the conventional SIW at all frequencies of 220 GHz to 300 GHz. As described above, the reason why the pass characteristic is good is that the microstrip transmission line whose tip is opened can prevent the leakage of the electromagnetic wave from the SIW.

  The effects obtained by the present embodiment will be described below. First, according to this embodiment, the tradeoff between the upper limit of the frequency of the electromagnetic wave that can be propagated by SIW and the mechanical strength of the substrate 100 (that is, the interval Wb of the TSVs 103 in the electromagnetic wave propagation direction) can be relaxed. Since the frequency can be increased while maintaining the mechanical strength of the substrate 100, an ultrahigh frequency component can be manufactured without a decrease in yield due to mechanical strength shortage. Therefore, according to the present embodiment, the cost reduction of the ultrahigh frequency components can be realized.

  Further, in the present embodiment, since the interval Wb of the TSVs 103 in the electromagnetic wave propagation direction can be made larger than a quarter wavelength of the electromagnetic wave propagating through the SIW, the number of TSVs 103 conventionally required for SIWs of lower frequencies. Can be reduced. Therefore, not only the mechanical strength is improved, but also the reduction of the product yield due to the accidental failure of the TSV 103 can be prevented. Therefore, cost reduction is expected also for products using low frequency SIW.

  In the present embodiment, the transmission line formed of the stubs 104 is a microstrip transmission line, but the same result is obtained in the case of the coplanar transmission line as shown in the second embodiment. It is clear that

Sixth Embodiment
Next, a sixth embodiment of the present invention will be described. This embodiment shows a specific example of the third embodiment and shows an example applied to SIW on an InP substrate. Since the basic configuration of the SIW is as described in the third embodiment, it will be described using the reference numerals of FIGS. 4 (A) to 4 (C). The calculation model used in the present embodiment is shown in FIG. As in the calculation example of FIG. 13, the thickness T of the substrate 100 made of InP is 50 μm, and the dielectric constant of InP is 12.3. The width Wc of the SIW is 180 μm, and the diameter D of the TSVs 103 and 109 is 40 μm. In addition, the interval Wb between the TSVs 103 in the electromagnetic wave propagation direction is set to 110 μm in which the passing characteristic of the SIW begins to deteriorate remarkably in FIG. Similar to the fifth embodiment, the characteristics of SIW are calculated on the assumption that air of relative dielectric constant 1 is present as the upper cladding 111 on the substrate upper surface metal layer 101c.

  In the present example, a stub 104 having a length L in the stretching direction of 80 μm and a width Wd in the direction perpendicular to the stretching direction of 35 μm was added to the substrate upper surface metal layer 101c. That is, as described in the third embodiment, the microstrip type transmission line including the stub 104, the substrate 100, and the substrate lower surface metal layer 102 and having the tip grounded by the TSV 109 is added. The length L = 80 μm is equal to a quarter wavelength of the microstrip transmission line at 300 GHz.

The results of calculating the pass characteristics S ₂₁ of SIW using the model shown in FIG. 8 is shown in FIG. For comparison, in the conventional SIW shown in FIG. 11, it is also shown passing characteristic S ₂₁ in the case where the distance Wb = 110 [mu] m of electromagnetic wave propagation direction TSV103. 70 in Figure 9 indicates the pass characteristic S ₂₁ of a conventional SIW, 72 indicates a pass characteristic S ₂₁ of SIW in this embodiment. As in the fifth embodiment, it can be seen that the passage characteristics are significantly improved by the present embodiment.

  The effects obtained by the present embodiment will be described below. According to this embodiment, the trade-off between the upper limit of the frequency of electromagnetic waves that can be propagated by SIW and the mechanical strength of the substrate 100 (that is, the interval Wb of the TSVs 103 in the electromagnetic wave propagation direction) can be relaxed. Therefore, as in the fifth embodiment, an ultra high frequency component using SIW can be manufactured inexpensively. In this embodiment, the transmission line formed by the stubs 104 is a microstrip transmission line. However, as shown in the fourth embodiment, similar results are obtained in the case of the coplanar transmission line. It is clear that

  Further, in the case of the microstrip transmission line, the TSV 109 is required to make the tip of the transmission line a short circuit end. On the other hand, when the coplanar transmission line is used, the front end of the coplanar transmission line can be made as a shorted end simply by connecting the front end of the stub 104 to the substrate upper surface metal layer 101d. Is unnecessary, so the number of TSVs 103 can be reduced in SIW for low frequency propagation as in the fifth embodiment. Therefore, not only the mechanical strength is improved, but also the reduction of the product yield due to the accidental failure of the TSV 103 can be prevented. Therefore, cost reduction is expected also for products using low frequency SIW.

Seventh Embodiment
Next, a seventh embodiment of the present invention will be described. FIG. 10 is a plan view showing the configuration of the SIW according to the seventh embodiment of the present invention, and the same reference numerals as in FIGS. 1A to 1C denote the same components. In the first and fifth embodiments, stubs 104 having a constant width are formed in the upper surface metal layer of the substrate. On the other hand, in the present embodiment, the stubs 104e whose width gradually increases toward the outside of the SIW are formed on the substrate upper surface metal layer 101e. That is, the stub 104e of the present embodiment, the substrate 100 and the lower surface metal layer below it constitute a microstrip transmission line (radial stub) whose line width gradually increases toward the open end.

  The radial stub is known to be able to obtain broadband characteristics as compared to a conventional open stub. Therefore, according to this embodiment, the low loss pass characteristics obtained in the first and fifth embodiments can be broadened more. The effects obtained by the present embodiment are the same as those of the fifth embodiment.

  In the first to seventh embodiments, as an example of the extending direction of the stubs 104 and 104e, a direction perpendicular to the electromagnetic wave propagation direction is described as an example, but the present invention is not limited to this. In addition, even if the extending directions of the stubs 104 and 104 e are different, the effect of the present invention is not lost. However, in order to arrange the plurality of stubs 104 and 104 e periodically along the electromagnetic wave propagation direction, it is easiest in terms of layout to make the extension direction of each stub 104 and 104 e perpendicular to the electromagnetic wave propagation direction.

  In the fifth and sixth embodiments, the width of the stub 104 is set to 35 μm. However, in the first to seventh embodiments, the widths of the stubs 104 and 104e may be set arbitrarily. Absent.

  In the first to seventh embodiments, the TSVs 103 and 109 only need to be able to electrically connect between the substrate upper surface metal layers 101a to 101e and the stubs 104 and 104e and the substrate lower surface metal layer 102, and metal films on the via sidewalls Because all electrical connections can be realized, the inside of the via may or may not be filled with metal.

  The present invention can be applied to circuit technology that handles high frequency electrical signals.

  100 ... substrate, 101a to 101e ... substrate upper surface metal layer, 102 ... substrate lower surface metal layer, 103, 109 ... substrate penetrating via, 104, 104e ... stub, 107, 110 ... groove, 111 ... upper clad.

Claims (6)

A substrate made of dielectric or semiconductor,
A first metal layer formed on the first surface of the substrate;
A second metal layer formed on the second side of the substrate opposite the first side;
A plurality of first through substrate vias formed periodically on the substrate so as to be arranged in two lines along the propagation direction of the electromagnetic wave, and connecting the first metal layer and the second metal layer;
A plurality of layers formed on the first metal layer so as to extend outward in a direction different from the propagation direction from locations between adjacent first substrate through vias in each row of the first substrate through vias Equipped with stubs,
The first substrate through via from the substrate surrounded by the stubs and the substrate and the second metal layer is the first and second metal layers and the first row of through substrate vias. Where the length of the line is λ / 4 + n × λ / 2, where n is the wavelength of the desired electromagnetic wave to be transmitted by the substrate. Substrate integrated waveguide characterized by being nonnegative integer). In the substrate integrated waveguide according to claim 1,
The plurality of stubs are respectively formed to protrude outward from the first metal layer,
The substrate integrated waveguide according to claim 1, wherein the line is a microstrip line consisting of each stub, the substrate and the second metal layer. In the substrate integrated waveguide according to claim 1,
The plurality of stubs are separated from the first metal layer at locations excluding the connection with the first metal layer by grooves formed in the periphery, respectively.
A substrate integrated waveguide according to claim 1, wherein the line is a coplanar line consisting of stubs, the substrate, the first metal layer, and the second metal layer. In the substrate integrated waveguide according to claim 1,
The said board | substrate is a board | substrate integrated waveguide characterized by the point being earth | grounded. In the substrate integrated waveguide according to claim 1,
The plurality of stubs are respectively formed to protrude outward from the first metal layer,
And a plurality of second through substrate vias connecting tips of the plurality of stubs and the second metal layer,
The said line is a microstrip type line which consists of each stub, the said board | substrate, and the said 2nd metal layer, and the front-end | tip is earth | grounded, The board | substrate integrated waveguide characterized by the above-mentioned. In the substrate integrated waveguide according to claim 1,
The plurality of stubs are separated from the first metal layer in locations other than the connection portion with the first metal layer and the tip end opposite to the connection portion by a groove formed around each of the plurality of stubs.
The said line is a coplanar type line which consists of each stub, the said board | substrate, the said 1st metal layer, and the said 2nd metal layer, and the front-end | tip is earth | grounded, The board | substrate integrated waveguide characterized by the above-mentioned.