JP4541922B2 - Antenna device - Google Patents

Description

  The present invention relates to an antenna device for manufacturing a planar antenna on a high dielectric constant substrate using micromachining technology.

  In recent years, the demand for antennas has increased with the development of communication systems in the microwave and millimeter wave bands. Here, if a micromachining technology based on semiconductor technology is used, a small antenna for the millimeter wave band can be created using an inexpensive semiconductor material such as silicon. Since it is manufactured at the wafer level, it is suitable for mass production and very low cost.

  As the antenna used in the RF band, a planar antenna is frequently used because of its thinness and small size and ease of processing. A typical example of this planar antenna is a microstrip antenna (hereinafter referred to as MSA), which is made of a conductor such as copper having a circular or square open boundary on a substrate and has a function as a radiator. It is. The variety of power feeding methods and the simplicity of arraying are also reasons why MSA is frequently used.

  When creating an MSA using micromachining technology, the relative dielectric constants of semiconductor substrates such as silicon and GaAs are as high as 11.9 and 10.2, respectively, which increases the dielectric loss and lowers the radiation efficiency. In particular, the influence is remarkable in the RF band.

  As an example of a conventional planar antenna using micromachining technology that takes this problem into account, there is a method of providing a hollow portion directly under the antenna to reduce the equivalent relative permittivity of the dielectric (for example, non-patent Reference 1).

IEEE Transaction on Antennas and Propagation, 1998, I. Papapolymerou, L. P. B. Katehi, "Micromachined Patch Antennas", Fig. 8

  However, when an antenna is formed as described above, the existing silicon wafer thickness is defined. Although this wafer can be thinned, there is a problem in strength in the subsequent process when the substrate is uniformly thinned, and the thickness of the silicon cannot be reduced below a certain size, that is, the depth of the cavity that can be realized, that is, There is a limit to the equivalent dielectric constant that can be realized. For this reason, there is a limit to adjusting and optimizing the antenna characteristics.

  The present invention has been made in view of the above points, and an antenna device that enables adjustment with a high degree of freedom by an equivalent relative dielectric constant when a planar antenna is manufactured on a high dielectric constant substrate using micromachining technology. The purpose is to obtain.

The antenna device according to the present invention is manufactured on one side of a semiconductor substrate by a micromachine technique, and is manufactured on one side of a semiconductor substrate by a micromachine technique. , it consists of a layered structure of a second semiconductor substrate covered by a conductor as a ground portion or the entire surface of the cavity opening side including the bottom surface of the cavity, the first semiconductor substrate, the patch antenna patterning The second semiconductor substrate is placed under the first semiconductor substrate so that the cavity opening faces the surface of the first semiconductor substrate on which the patch antenna is not patterned. It is characterized by having been arranged in.

  According to the antenna device of the present invention, when a planar antenna is manufactured on a high dielectric constant substrate using micromachining technology, adjustment with a high degree of freedom can be made possible by an equivalent relative dielectric constant. Since only inexpensive silicon is used, there is mass production, resulting in low cost.

Embodiments of the present invention will be described below with reference to the drawings.
Embodiment 1 FIG.
1A and 1B show an antenna device according to Embodiment 1 of the present invention, in which FIG. 1A is a perspective view, FIG. 1B is a cross-sectional view along line aa ′ shown in FIG. 1A, and FIG. It is a top view seen from the upper surface of).
As shown in FIG. 1, a cavity 12 having an arbitrary depth is provided in the first semiconductor substrate 11, and a patch antenna 13 is patterned on the bottom surface of the cavity 12. The second semiconductor substrate 14 is provided with a cavity 15, and the surface of the second semiconductor substrate 14 including the bottom surface of the cavity 15 is covered with a ground (conductor) 16.

  That is, the antenna device shown in FIG. 1 enables adjustment with a high degree of freedom by an equivalent relative permittivity when a planar antenna is manufactured on a high permittivity substrate using micromachining technology. Between the first semiconductor substrate 11 on which the patch antenna 13 is patterned and the second semiconductor substrate 14 in which a part or the entire surface of the cavity opening side including the bottom surface of the cavity 15 is covered with a conductor serving as a ground 16. The first semiconductor substrate 11 has a laminated structure, the patterned surface of the patch antenna 13 is arranged upward, and the second semiconductor substrate 14 is a patch of the first semiconductor substrate 11 with the opening side of the cavity 15 being the opening side. The antenna 13 is disposed under the first semiconductor substrate 11 so as to face the surface that is not patterned.

  In the structure of FIG. 1, the equivalent relative dielectric constant is determined by the thickness of the semiconductor substrate below the patch antenna 13 installed on the first semiconductor substrate 11 and the thickness of the cavity 15 of the second semiconductor substrate 14. By adjusting the substrate / air layer ratio, the specific bandwidth can be adjusted at the design frequency.

Next, a power feeding method to the antenna device according to Embodiment 1 of the present invention will be described.
As a well-known method for supplying power to the MSA, a method of directly supplying power by connecting a microstrip line to the end of the MSA, a microstrip provided on a separate substrate through a slot hole provided in the ground conductor of the MSA Examples include an electromagnetic field coupling method in which power is supplied from a line or a triplate line, and a method in which a coaxial line is connected to the back surface of the MSA.

  In the millimeter wave band, it is difficult to connect a coaxial line, and therefore, an electromagnetic coupling that can be integrated by a semiconductor technology or direct feeding by a strip line can be considered as a feeding method. In addition, the electromagnetic coupling method has advantages in that it is easier to manufacture a feeder line than other methods and that it can be manufactured by a simple process of laminating a substrate on which a microstrip line is patterned with an MSA substrate.

Here, as a power feeding method for the antenna device according to the first embodiment of the present invention, a method using electromagnetic coupling will be taken up and described with reference to FIG. 2A is a perspective view, FIG. 2B is a cross-sectional view taken along the line aa ′ in FIG. 2A, and FIG. 2C is a perspective view seen from the direction b in FIG.
As shown in FIG. 2, a cavity 22 having an arbitrary depth is provided in the first semiconductor substrate 21, and a patch antenna 23 is patterned on the bottom surface of the cavity 22. The second semiconductor substrate 24 is provided with a cavity 25, and the surface of the second semiconductor substrate 24 including the bottom surface of the cavity 25 is covered with a ground 26.

  In addition, a slot hole 27 is provided in the ground 26 at the bottom of the cavity 25 of the second semiconductor substrate 24, and a microstrip line 28 is patterned on the back surface of the second semiconductor substrate 24. The microstrip line 28 is arranged so as to be orthogonal to the slot hole 27, and power is supplied through the slot hole 27.

  The length of the slot hole 27 is about half a wavelength so as to resonate at the center frequency. If the open end of the microstrip line 28 is a stub opened at a position of λg / 4 from the slot hole, the current flowing directly under the slot hole becomes maximum, and the magnetic field generated by the stub becomes maximum. Therefore, at this time, it is strongly coupled to the slot hole 27 and efficiently supplies power to the antenna. Here, λg is the in-tube wavelength of the microstrip line 28. At this time, by changing the width of the slot hole 27 and the width of the microstrip line 28 as a stub, the respective characteristic impedances are changed to achieve matching with the MSL line.

  The slot hole 27 is provided on the bottom surface of the cavity 25. In the micromachining process, first, the cavity is engraved and then a mask having a size smaller than the actual pattern is used. Such patterning is also possible. Further, the shape of the slot hole 27 is not limited to a rectangle as shown in the figure, but may be an H shape or a dog bone shape. If the shape of the slot hole 27 is changed, the amount of coupling to the patch antenna 23 can be adjusted over a wide band.

Next, the operation when power is supplied to the upper surface through the slot hole 27 will be described.
This antenna can resonate at the design frequency by resonating the slot hole 27 and selecting the size of the patch antenna 23 optimally. If there is no patch antenna 23 and only the slot hole 27 is present, more electromagnetic waves are radiated downward due to the presence of the cavity 25, but the patch antenna 23 acts as a waveguide and radiates radio waves to the upper surface.

As an advantage of the antenna of this structure, the relative permittivity can be adjusted by adjusting the depth of the cavities 22 and 25, and the specific bandwidth can be varied. Numerical analysis results showing this are shown below. In FIG. 2B, the semiconductor wafer thickness d of the first semiconductor substrate 21 and the second semiconductor substrate 24 is defined. Therefore, the result of numerical analysis of the relationship between the antenna substrate thickness (Substrate depth) and the specific bandwidth (Bandwidth) when the t1 / t2 ratio is changed under the constraint condition that the antenna substrate thickness (t1 + t2) = d is shown in FIG. Shown in In FIG. 3, 31 is a case where t1 = 0.17d, and 32 is a case where t1 = 0.3d. Here, the specific bandwidth is a value normalized by the input impedance viewed from the slot hole 27 toward the antenna side when resonating at the design frequency. Even when this input impedance is deviated from the impedance of the feeder line, matching is possible by adopting a method of providing a stub or a transformer on the microstrip line 28 of the feeder line.

  As shown in FIG. 3, it can be seen that the specific bandwidth increases in proportion to the substrate thickness. Also, when the t1 / t2 ratio is different, the smaller the t1 is, the larger the specific bandwidth is. Further, in the numerical analysis example shown in FIG. 3, the antenna having this structure has a specific bandwidth of about 18% at the maximum, and has a broadband property compared with a normal patch antenna. This is presumably because when t2 is thick, the patch antenna 23 operates as a perturbation element in the cavity antenna mainly composed of the cavity 26.

  In the antenna according to the first embodiment described above, when both the thicknesses t1 and t2 are increased, the size of the patch antenna 23 is reduced, and the processing accuracy becomes severe. A countermeasure at this time is shown in FIG. In FIG. 4, the same components as those in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted. 4 (a) and 4 (b) correspond to FIGS. 2 (a) and 2 (b), and FIG. 4 (c) is a perspective view seen from the upper surface of FIG. 4 (b). As shown in FIG. 4, by making a large number of holes 41 in the patterned substrate portion of the patch antenna 23 of the first semiconductor substrate 21, the dielectric constant is lowered and the size of the matching patch antenna 23 is increased. . Thus, there is an effect that it is not necessary to set a strict processing accuracy even when the antenna substrate thickness is increased.

Next, a second example of the power feeding method for the first embodiment of the present invention will be described with reference to FIG.
In FIG. 5, the same components as those in FIG. 5 (a) and 5 (b) correspond to FIGS. 2 (a) and 2 (b), and FIG. 5 (c) is a perspective view seen from the direction b in FIG. 5 (a). In FIG. 5, reference numeral 61 denotes a resin substrate. A ground 62 is applied to the back surface of the resin substrate 61, and a triplate line signal line 63 constituted by the ground 62 and the ground 26 is formed on the surface of the resin substrate 61. ing. In addition, a via 64 penetrating the resin substrate 61 and the second semiconductor substrate 24 is provided. As described above, when the resin substrate 61 is provided to form a triplate line, when a substrate provided with a phase shifter and an amplifier is laminated under the resin substrate 61, radiation from the feeder line to these circuit elements is eliminated. There is an advantage that can be.

  The signal line 63 of the triplate line is an open stub extending about λg / 4 from directly below the slot hole 27. At this time, in order to prevent the parallel plate mode from being caused by the ground 26 which is the ground conductor of the antenna provided with the slot hole 27 and the ground 62 which is the ground conductor of the triplate line parallel to the ground 26, in the vicinity of the slot hole 27. Need to make several vias 64 for conduction. The required number is arbitrarily arranged at an optimal position, not limited to the figure. Here, in order to prevent resonance between the vias 64, the interval between the vias 64 is set to λg / 4 or less. In the micromachining process, it is possible to pass such a via 64. Here, the minimum diameter of the via 64 depends on the aspect ratio with the substrate. For example, when the aspect ratio is 3 and the substrate thickness is 300 μm, the minimum diameter of the via 64 that can be hit on the substrate is 100 μm.

Embodiment 2. FIG.
FIG. 6 shows an antenna apparatus according to Embodiment 2 of the present invention. FIGS. 6 (a) and 6 (b) correspond to FIGS. 2 (a) and 2 (b), and FIG. It is the top view seen from the upper surface of 6 (b). In FIG. 6, the same components as those in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted. The patch antenna 23 patterned on the bottom surface of the cavity of the first semiconductor substrate 21 is patterned and extended with a conductor as a feed signal line 81 serving as a strip line, and a signal line is formed on the back surface of the first semiconductor substrate 21. The conductor 83 is patterned, and a via 82 penetrating the first semiconductor substrate 21 is provided at the end of the signal line 81 so that the signal line 81 and the signal line 83 are electrically connected. Further, a coplanar line 84 is patterned on the side surface of the ground 26 inside the cavity 25 of the second semiconductor substrate 24, and a conductor which is a signal line 86 is patterned on the back surface of the second semiconductor substrate 24. A via 85 that conducts the signal line 84 and the signal line 86 is provided, and the coplanar line 84 is fed by a penetrating structure from the back surface of the second semiconductor substrate 24. The ground 26 is not provided with the slot hole 27 as shown in FIG.

  Next, the operation will be described. Now, when an RF signal is input from the signal line 86, the RF signal reaches the patch antenna 23 through the via 85, the coplanar line 86, the signal line 83, the via 82, and the signal line 81. Unlike the first embodiment, since the MSA is directly fed with a signal line rather than electromagnetic coupling, the first embodiment operates as a cavity antenna and a director, but in this embodiment, it operates as a patch antenna.

  In the antenna of the second embodiment, as in the first embodiment, the relative permittivity can be adjusted by providing a large number of air holes in the substrate below the patch antenna 23, and the specific bandwidth and the size of the antenna can be changed. . Further, as in the first embodiment, by stacking the specific excitation elements, the bandwidth can be increased.

  In the first and second embodiments described above, for the lamination and adhesion of semiconductor substrates, a method in which a mixture of gold (Au) and chromium (Cr) is applied onto a substrate and crimped, or solder is applied and thermocompression bonded. The way to do is taken.

  In the first and second embodiments described above, when the inside of the cavity is filled and sealed with air, the thin layer of the etched semiconductor substrate becomes a diaphragm, and the shape of the cavity may change due to atmospheric pressure. is there. In order to prevent this, a minute hole may be formed in the semiconductor substrate.

  In the first and second embodiments, the cavity may be filled with a dielectric having a low dielectric constant. Examples include polyimide having a relative dielectric constant of 3.5, porous silicon capable of adjusting the relative dielectric constant by making air holes in the silicon, curing it, and adjusting the ratio of the air.

Embodiment 3 FIG.
FIG. 7 is a cross-sectional view showing an antenna apparatus according to Embodiment 3 of the present invention.
As shown in FIG. 7, the antenna device according to the third embodiment includes a third semiconductor substrate 72 on which a patch antenna 71 is patterned on the bottom surface of the cavity 73, and is the same antenna device as in the first and second embodiments. The third semiconductor substrate 21 is formed on the first semiconductor substrate 21 such that the opening of the cavity 22 of the first semiconductor substrate 21 faces the surface of the third semiconductor substrate 72 where the patch antenna 71 is not patterned. 72 are stacked.

  For this reason, the patch antenna 71 also functions as a non-excitation element, and as a result, the band can be further expanded. At this time, the beam width and beam directivity can also be controlled by adjusting the size and thickness of the cavity 73 of the semiconductor substrate 72.

  Furthermore, the antenna devices according to Embodiments 1 to 3 described above can be arrayed to provide high functionality such as beam scanning.

It is a figure which shows the antenna apparatus which concerns on Embodiment 1 of this invention. It is a figure for demonstrating the 1st electric power feeding method to the antenna device which concerns on Embodiment 1 of this invention. It is a figure which shows the effect of the antenna device which concerns on Embodiment 1 of this invention. It is a figure for demonstrating a countermeasure when the antenna board | substrate thickness of the antenna apparatus which concerns on Embodiment 1 of this invention becomes large, the size of a patch antenna becomes small, and processing precision becomes severe. It is a figure for demonstrating the 2nd electric power feeding method to the antenna apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the antenna apparatus which concerns on Embodiment 2 of this invention. It is a figure which shows the antenna apparatus which concerns on Embodiment 3 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Conductor, 2 Cavity part, 3 Ground, 4 Signal conductor, 5 Dielectric, 11, 14 Semiconductor substrate, 12, 15 Cavity part, 13 Patch antenna, 16 Ground, 21, 24 Semiconductor substrate, 22, 25 Cavity part, 26 Ground, 27 slot hole, 28 microstrip line, 41, 42 hole, 51 via, 61 resin substrate, 62 ground, 63 signal line, 64 via, 71 patch antenna, 72 semiconductor substrate, 73 cavity, 81 signal line, 82 , 85 vias, 83, 86 signal lines, 84 coplanar lines.

Claims (5)

A first semiconductor substrate manufactured on one side of a semiconductor substrate by micromachine technology and patterned with a patch antenna on the bottom surface of the cavity, and a cavity including the bottom surface of the cavity portion similarly manufactured on one side of the semiconductor substrate by micromachine technology It is composed of a laminated structure with a second semiconductor substrate covered with a conductor serving as a ground on a part or the entire surface on the part opening side,
The first semiconductor substrate is arranged with the patterned surface of the patch antenna facing upward,
The second semiconductor substrate is disposed under the first semiconductor substrate such that a cavity opening faces a surface of the first semiconductor substrate on which the patch antenna is not patterned. apparatus. The antenna device according to claim 1,
A slot hole is provided in the bottom surface of the cavity portion of the second semiconductor substrate, and a microstrip line having the bottom surface of the cavity portion as a ground is disposed on the bottom surface of the second semiconductor substrate so as to be orthogonal to the slot hole, An antenna device, wherein power is fed from a microstrip line through the slot hole. The antenna device according to claim 1,
A coplanar line is provided on the conductor inside the hollow portion of the second semiconductor substrate, and the coplanar line is fed by a through structure from the back surface of the second semiconductor substrate, and a strip line is extended from the patch antenna. The antenna device is characterized in that a via that penetrates the first semiconductor substrate is provided at an end portion of the strip line and is connected to the coplanar line. In the antenna device according to any one of claims 1 to 3,
A third semiconductor substrate having a patch antenna patterned on the bottom of the cavity,
Laminating the third semiconductor substrate on the first semiconductor substrate such that the cavity opening of the first semiconductor substrate faces the surface of the third semiconductor substrate on which the patch antenna is not patterned. An antenna device characterized by that. The antenna device according to any one of claims 1 to 4, wherein the antenna device is arrayed on the same substrate.

Images