Patent Application
20250233321
The present invention relates to an antenna apparatus, a communication apparatus, and an image capturing system.
The development of a semiconductor device that outputs or detects an electromagnetic wave such as a terahertz wave has been accelerated because of the frequency band used by the next generation communication standard 6G. An active antenna formed by integrating a Resonant Tunneling Diode (RTD) and an antenna is expected as a high frequency element that operates at room temperature in a frequency domain around 1 THz. Japanese Patent No. 6373010 discloses an active antenna array of a terahertz wave using an RTD. A material such as InGaAs (indium gallium arsenide) having high electron mobility is used for such high frequency element, and the high frequency element is formed on a semiconductor substrate such as an InP (indium phosphide) substrate. On the other hand, the control circuit of the high frequency element is formed on a semiconductor substrate using a semiconductor material such as Si (silicon).
If a substrate on which a high frequency element is formed and a substrate on which a control circuit is formed are different types of substrates, it is necessary to individually manufacture the substrates. In this case, depending on a method of connecting the substrates on which the high frequency element and the control circuit are formed, respectively, high-speed signal control may be impossible since a signal delay or signal loss occurs due to inductance caused by a wiring length. Furthermore, depending on the connection, the degree of freedom of control of an antenna array may degrade. That is, in an antenna apparatus including a substrate on which a high frequency element is formed and a substrate on which a control circuit is formed, connection between the substrates has not been examined in detail.
The present invention provides a preferable antenna apparatus including a plurality of substrates.
To achieve the above object, an antenna apparatus according to the present invention comprises: a first substrate including an antenna array in which a plurality of active antennas each including an antenna and a semiconductor structure configured to generate or detect an electromagnetic wave are provided, and a wiring electrically connected to the plurality of active antennas; and a second substrate stacked on the first substrate and including a control circuit of the antenna array, wherein the first substrate and the second substrate are bonded at a bonding surface, the control circuit is electrically connected to the antenna array via the wiring, and the control circuit of the second substrate controls oscillations of the plurality of active antennas of the first substrate.
According to the present invention, it is possible to provide a preferable antenna apparatus including a plurality of substrates.
Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings).
Hereinafter, embodiments will be described in detail with reference to the attached drawings. Note, the following embodiments are not intended to limit the scope of the claimed invention. Multiple features are described in the embodiments, but limitation is not made to an invention that requires all such features, and multiple such features may be combined as appropriate. Furthermore, in the attached drawings, the same reference numerals are given to the same or similar configurations, and redundant description thereof is omitted.
In the following description, a case in which an antenna apparatus is used as a reception apparatus that detects a terahertz wave will be described but the antenna apparatus can also be used as a transmission apparatus that emits a terahertz wave. A terahertz wave indicates an electromagnetic wave within a frequency range of 10 GHz (inclusive) to 100 THz (inclusive), for example, a frequency range of 30 GHz (inclusive) to 30 THz (inclusive).
The arrangement of an antenna apparatus 10 according to this embodiment will be described with reference to
Referring to
Each of active antennas AA11 to AAmn of the active antenna array 11 of the first substrate 151 includes a semiconductor structure as a semiconductor layer 100 (compound semiconductor layer) for transmitting/receiving a terahertz wave, and a conductor layer 101 in which a wiring is formed. The conductor layer 101 will also be referred to as an antenna wiring layer hereinafter. Therefore, as shown in
The second substrate 152 includes a control unit (control circuit) 165 for individually controlling the active antennas AA11 to AAmn. The control circuit 165 includes a plurality of control elements AC11 to ACmn. In this embodiment, the control elements AC11 to ACmn are connected to the active antennas AA11 to AAmn in one-to-one correspondence, and are arranged in a matrix, similar to the active antennas AA11 to AAmn. The control elements AC11 to ACmn of the second substrate 152 may be arranged in regions immediately below the corresponding antennas AA11 to AAmn, respectively. In this case, the wiring length between a corresponding antenna ANmn and the control element ACmn is shortest, and the lengths of wirings that couple the respective antennas to the control unit are substantially equal to each other, and it is thus possible to reduce wiring inductance. For example, as shown in
As in a line driving circuit shown in
In the active antenna array 11 described in this embodiment, the active antennas are coupled by a coupling line CL as a transmission line, and are electrically connected. The coupling line CL as a transmission line can perform mutual injection locking between the antennas at the frequency fTHz. For example, the active antennas AA1 and AA2 are connected by a coupling line CL12, and an impedance variable device VZ1 for adjusting the impedance of the coupling line between the active antennas AA1 and AA2 is provided at the intermediate point of the coupling line CL12. In the example of the 3×3 array shown in
As shown in
The active antenna AA1 includes the conductor layer 101, the semiconductor layer 100, the conductor layer 109 (reflector), the dielectric layers 104 and 105, and the via 103 that connects the conductor layer 101 and the semiconductor layer 100. To apply a control signal to the semiconductor layer 100, the conductor layer 102 forming the bias wiring, the via 107, a Metal Insulator Metal (MIM) capacitor 126, and a resistance layer 127, which are individually provided for each antenna, are connected to the active antenna AA1. The MIM capacitor 126 is a capacitive element that sandwiches an insulator layer by a metal, and is arranged to suppress a low-frequency parasitic oscillation caused by a bias circuit. The MIM capacitor 126 of this embodiment uses a structure in which part of a dielectric layer 106 is sandwiched by a conductor layer 113 and the conductor layer 109 as GND.
To increase the gain of the active antenna array 11, it is considered that the plurality of active antennas AA1 to AA9 are arranged in an array. The semiconductor layer 100 including the RTD is arranged in each active antenna, as described above, and the gain of the active antenna is increased by performing mutual injection locking between the active antennas. To establish synchronization among the plurality of active antennas AA1 to AA9, the coupling lines CL each coupling adjacent antennas are necessary. Each active antenna and each coupling line are connected by capacitive coupling. The length of the coupling line CL is designed to satisfy a phase matching condition in one or both of the horizontal direction (magnetic field direction/H direction) and the vertical direction (electric field direction/E direction) if the adjacent antennas are connected by the coupling line. Note that the present invention is applicable not only to an antenna that emits a horizontally/vertically polarized wave but also to an antenna that emits a circularly polarized wave. For example, by setting the conductor layer 101 of the patch antenna to have a rectangular shape other than a square and forming a notch, it is possible to emit a circularly polarized wave. Alternatively, an antenna, different from a patch antenna, that emits a circularly polarized wave may be applied.
In an example, the coupling line is designed to have such length that the electrical length between the RTDs of the adjacent antennas is equal to an integer multiple of 2π. For example, the coupling line CL14 extending in the horizontal direction has such length that the electrical length between the semiconductor layers 100 of the active antennas AA1 and AA4 is equal to 4π. Furthermore, the coupling line CL12 extending in the vertical direction has such length that the electrical length between the semiconductor layers 100 of the active antennas AA1 and AA2 is equal to 2π. At this time, the electrical length indicates a wiring length considering the propagation speed of a high frequency wave that propagates in the coupling line. With this design, the semiconductor layers 100 of the active antennas AA1 to AA9 are mutual injection-locked in the positive phase. Note that the error range of the length is ±¼π.
The impedance variable device VZ12 for adjusting the impedance of the coupling line CL1 is provided at the intermediate point of the coupling line CL1 that connects the adjacent active antennas AA1 and AA2. In this embodiment, as the impedance variable device VZ, a MOSFET advantageous in circuit integration and a reduction in cost is used. The first substrate 151 on which an antenna array for transmitting/receiving a terahertz wave and the semiconductor layer 100 formed from a compound semiconductor (semiconductor structure) are integrated and the second substrate 152 including a CMOS integrated circuit for antenna array control are bonded at a bonding surface B.S. This arrangement is implemented by stacking, by a semiconductor stacking technique, an antenna substrate of a compound semiconductor including an antenna array and an Si integrated circuit substrate.
As shown in
One active antenna AA is formed from the conductor layer 101 of the antenna, the semiconductor layer 100, the conductor layer 109 (reflector), the dielectric layers 104 and 105, and the via 103 that connects the conductor layer 101 and the semiconductor layer 100. To apply a control signal to the semiconductor layer 100, the conductor layer 102 forming the bias wiring, the via 107, the MIM capacitor 126, and the resistance layer 127, which are individually provided for each antenna, are connected to the active antenna AA, as shown in
The bonding surface B.S. is provided on the lower surface of the first substrate 151 on which the antenna array and the compound semiconductor are integrated, and the first substrate 151 is bonded, via the bonding surface B.S., to the second substrate 152 including the integrated circuit. At this time, “bonded” is defined as sharing the same bonding surface B.S. by the first substrate 151 and the second substrate 152. The bonding second substrate 152 is formed by including a semiconductor substrate as a base material and an integrated circuit region where a driving circuit is formed. The two different kinds of substrates 151 and 152 are bonded by metal bonding such as Cu—Cu bonding, insulator bonding such as SiOx—SiOx bonding, hybrid bonding as a combination of these, adhesive bonding using an adhesive such as BCB, or the like. As a bonding process, low-temperature bonding using plasma activation or conventional thermocompression bonding is used. A method of bonding semiconductor wafers of the same size, a method of bonding semiconductor wafers of different sizes, a method (tiling) of separately bonding a plurality of semiconductor chips to a wafer, or the like is used.
In the active antenna array 11, the mesa structure of the semiconductor layer 100 is embedded in the dielectric layer 105 to cover the periphery. The surface of the dielectric layer 105 on the side of the bonding surface B.S. is planarized, and the conductor layer 109 as a reflector is provided on the planarized surface. The dielectric layer 105 plays the role as a dielectric material forming the antenna and the role of a planarization film in a manufacturing process of transferring the mesa structure of the semiconductor layer 100 to the different type of substrate. As the dielectric layer 105, for example, an inorganic insulating material such as silicon oxide (SiOx), silicon nitride (SiNx), silicon oxynitride (SiON), carbon-containing silicon oxide (SiOC), or silicon carbide (SiC) is used. The active antenna array 11 is formed from an antenna region 52 (in the conductor layer 101 as the upper conductor of the patch antenna) where the antennas are provided, and a peripheral region 51, outside the antenna region, where the bias wiring and coupling lines CL are provided. The antenna region 52 indicates a region overlapping the conductor layer 101 as the upper conductor of each patch antenna in the stacking direction of the substrates, and the peripheral region 51 indicates a region not overlapping the conductor layer 101 as the upper conductor of each patch antenna. In an example, the peripheral region 51 is a region not overlapping the conductor layer 101 as the upper conductor of each patch antenna, and a region separated from the conductor layer 101 by 1/10 or more of the wavelength of the terahertz wave. That is, the antenna region 52 is a region including the near field of the terahertz wave, and the peripheral region 51 is a region not including the near field of the terahertz wave.
On the side of the first substrate 151 opposite to the second substrate 152, the conductor layer 109, the dielectric layer 105, the dielectric layer 104, and a dielectric layer 112 are stacked in this order. In the dielectric layers 105 and 104, the via 103, the via 107, and a via 124, and the conductor layer 101, the conductor layer 102, and the conductor layer 111 respectively connected to the vias are formed. The surface of the first substrate 151 on the side of the bonding surface B.S. to the second substrate 152 is arranged at a position facing the semiconductor layer 100 via the conductor layer 109 as the reflector. The conductor layer 102 as a wiring layer is provided at the intermediate point between the conductor layer 101 as an antenna layer and the conductor layer 109 as a reflector layer. On the planarized surface of the dielectric layer 105 of the first substrate 151 on the side of the second substrate 152, the conductor layer 109 and an insulator layer 131 are stacked in this order, and a through via 137 and a bonding electrode layer 138 are formed in the insulator layer 131. The insulator layer 131 and the electrode layer 138 are planarized at the bonding surface B.S., and undergoes a bonding process in a state in which the flat bonding surface B.S. is exposed. In the second substrate 152, a semiconductor substrate 134 as a base material, an insulator layer 133, a conductor layer 140, and an insulator layer 132 are stacked in this order, and a via 141 and a bonding electrode layer 139 are formed in the insulator layer 132. The insulator layer 132 and the electrode layer 139 are planarized at the bonding surface B.S., and undergoes a bonding process in a state in which the flat bonding surface B.S. is exposed. Therefore, the bonding surface B.S. is provided between the conductor layer 109 as a reflector and the second substrate 152 as a control circuit substrate. In this arrangement, since the antennas and the control circuit are separated, it is possible to reduce noise caused by radio frequency interference between the active antenna array operating at a terahertz frequency and the control circuit operating at an RF frequency. The insulator layers 131 to 133 can be formed using an inorganic insulating material such as silicon oxide (SiOx), silicon nitride (SiNx), silicon oxynitride (SiON), carbon-containing silicon oxide (SiOC), or silicon carbide (SiC). Furthermore, for the insulator layer 131, a compound semiconductor substrate may be used.
Similarly, the conductor layer 109 as a reflector in the antenna of the first substrate 151 is electrically connected to a through via 137g provided in the insulator layer 131, and a bonding electrode layer 138g in this order to reach the bonding surface B.S. The conductor layer 140 as GND of the second substrate 152 is connected to a via 141g formed in the insulator layer 132 and a bonding electrode layer 139g in this order to reach the bonding surface B.S. The electrode layer 138g of the first substrate 151 and the electrode layer 139g of the second substrate 152 are electrically connected at the bonding surface B.S., thereby sharing the GND potential of both the substrates. As an example of enhancing the bonding strength, dummy electrode layers 138d and 139d not connected to signal lines may be provided on the bonding surface B.S. By widely distributing the dummy electrode layers 138d and 139d in a region where no wiring electrode is necessary, the bonding strength can be enhanced, thereby improving the yield and reliability. Furthermore, by widely distributing and arranging the GND electrode layers 138g and 139g and the dummy electrode layers 138d and 139d over the entire bonding surface B.S., it is possible to reduce the influence of electromagnetic wave noise on the terahertz antennas of the first substrate 151, which is caused by the integrated circuit of the second substrate 152.
Similarly, the conductor layer 109 as a reflector in the antenna of the first substrate 151 is electrically connected to the through via 137g provided in the insulator layer 131, and the bonding electrode layer 138g in this order to reach the bonding surface B.S. The conductor layer 101 as the upper conductor and the conductor layer 109 having an area larger than that of the upper conductor formed in the conductor layer 101 and operating as GND function as a patch antenna that resonates with the terahertz wave. The conductor layer 140 as GND of the second substrate 152 is connected to the via 141g formed in the integrated circuit region 154 and the bonding electrode layer 139g in this order to reach the bonding surface B.S. The electrode layer 138g of the first substrate 151 and the electrode layer 139g of the second substrate 152 are electrically connected at the bonding surface B.S., thereby sharing the GND potential of both the substrates. By arranging the conductor layer 140 as second GND separately from the conductor layer 109 as a reflector and first GND, it is possible to reduce noise caused by radio frequency interference between the active antenna operating at a terahertz frequency and the control circuit operating at an RF frequency. To increase the effect of noise reduction, the conductor layers 109 and 140 each serving as GND are preferably formed in a solid pattern. As an example of enhancing the bonding strength, dummy electrode layers 138b and 139b not connected to signal lines may be provided on the bonding surface B.S. By widely distributing the dummy electrode layers 138b and 139b in a region where no wiring electrode is necessary, the bonding strength can be enhanced, thereby contributing to improvement of the yield and reliability. Furthermore, by widely distributing and arranging the GND electrode layers 138g and 139g and the dummy electrode layers 138b and 139b on the bonding surface B.S., it is possible to reduce the influence of electromagnetic wave noise on the antennas of the first substrate 151, which is caused by the integrated circuit of the second substrate.
Similarly, the transistor TRb formed in the integrated circuit region 154 of the second substrate 152 is electrically connected to the via 141b formed in the integrated circuit region 154 and the bonding electrode layer 139b in this order to be electrically connected to the bonding surface B.S. When the electrode layer 138b of the first substrate 151 and the electrode layer 139b of the second substrate 152 are electrically connected at the bonding surface B.S., the bias wiring layer 102 of the antenna array and the transistor TRa of the integrated circuit region 154 are rendered conductive. This can make it possible to individually apply a control signal to each antenna.
The transistor TRa as a phase control circuit adjusts the impedance of the coupling line CL by a variable resistance or a switch operation by connecting the source-drain path of the MOSFET to the intermediate point of the coupling line CL. The transistor TRa for phase control can be used as a variable capacitor by connecting the gate-source path. The MOSFET of the transistor TRa as a bias control circuit also serves as a bias control unit, and operates as a switching regulator to supply a bias signal to the semiconductor layer 100. As another arrangement, an arrangement in which a voltage is supplied from the outside of the second substrate 152 by additionally providing a terminal for applying a bias signal on the second substrate 152 and causing the transistor TRa to operate as an analog switch may be adopted.
The active antenna array 11 shown in
In the active antenna array of the terahertz wave, to individually control each antenna, a plurality of wirings such as a bias line for supplying power to the compound semiconductor, a synchronization line for controlling synchronization between the antennas, and a control line for injecting a baseband signal into the antenna are necessary. On the other hand, to improve the gain of the antenna, it is necessary to increase the number of antennas but wiring inductance caused by the layout increases along with an increase in number of antennas, thereby interfering with implementation of a high frequency. To the contrary, in this embodiment, the antenna substrate (first substrate 151) of the compound semiconductor including the antenna array and the Si integrated circuit substrate (second substrate 152) are stacked by a semiconductor bonding technique. This eliminates the need to take an implementation form of integrating or externally connecting a peripheral circuit necessary to control the active antenna array onto the compound semiconductor substrate. This can suppress an increase in inductance caused by wiring routing, and typically suppress inductance to 1 nH or less, thereby suppressing a signal loss or signal delay of the baseband signal subjected to modulation control at a high frequency of 1 GHz or more.
Since, in the periphery of the antenna, there is no circuit that is not related to transmission/reception of the terahertz wave or the number of such circuits can be made sufficiently small, noise by unnecessary reflection is reduced, thereby making it possible to exhibit the characteristic of the antenna at the maximum. If the bias signal of the compound semiconductor and the like are controlled for each antenna, each bias wiring needs to be individually arranged. To the contrary, in this embodiment, the first substrate 151 including the antenna array can directly be connected to the integrated circuit of the second substrate 152 via the through vias 137b, 137c, 137d, and 137g. If the active antenna array is used, a wiring can be arranged on the rear side (that is, the rear side of the conductor layer 109 as a reflector) of the antenna substrate (first substrate 151) of the compound semiconductor including the antenna array. Therefore, it is possible to increase the number of active antennas included in the antenna array without receiving the influence of the layout. Furthermore, the second substrate 152 including the integrated circuit can form a complex circuit such as a detection circuit or a signal processing circuit using the conventional CMOS integrated circuit technique. Therefore, by using the arrangement described in this embodiment, it is possible to sophisticate the antenna apparatus and reduce the cost, and thus readily use an electromagnetic wave in the terahertz band.
A bonding surface B.S. is provided on the lower surface of the semiconductor substrate 131 as a base material of the first substrate 151, and a second substrate 152 including an integrated circuit is bonded. In this embodiment, hybrid bonding of Cu—Cu bonding and SiOx—SiOx bonding is used to perform tiling of bonding the cut first substrate 151 to the 12-inch Si integrated circuit substrate.
In the first substrate 151, an insulator layer 148, the semiconductor substrate 131, a conductor layer 109, and dielectric layers 105, 104, and 112 are stacked in this order from the side of the bonding surface B.S. to the second substrate 152. In the dielectric layers 105 and 104, vias 103, 107, and 117 and conductor layers 101, 102, and 111 are formed. The surface of the first substrate 151 on the side of the bonding surface B.S. to the second substrate 152 is arranged at a position facing the semiconductor layer 100 via the conductor layer 109 as the reflector. A through via 137 formed to extend through the insulator layer 131 is formed in the semiconductor substrate 131. As the material of the through via 137, copper (Cu) or gold (Au) is preferably used. The insulator layer 148 and an electrode layer 138 for bonding are planarized at the bonding surface B.S., and undergoes a bonding process in a state in which the flat bonding surface B.S. is exposed. In the second substrate 152, a semiconductor substrate 134 as a base material and an insulator layer 132 are stacked in this order, and a conductor layer 140 forming a multilayer wiring, a via 141, and a bonding electrode layer 139 are formed in the insulator layer 132. An insulator layer 132 and the electrode layer 139 are planarized at the bonding surface B.S., and undergoes a bonding process in a state in which the flat bonding surface B.S. is exposed. For the insulator layers 132 and 148, an inorganic insulating material such as silicon oxide (SiOx), silicon nitride (SiNx), silicon oxynitride (SiON), carbon-containing silicon oxide (SiOC), or silicon carbide (SiC) is used. As described above, the board thickness is designed within a range of 1/10 or less of the wavelength of the terahertz wave to be operated. Therefore, the distance between the conductor layer 111 and the semiconductor substrate 134 can be made 1/10 or less of the wavelength of the terahertz wave, and it is possible to reduce the impedance of the through via 137, the bonding electrode layers 138 and 139, and the via 141.
At the bonding surface B.S. between the electrode layer 138b of the first substrate 151 and the electrode layer 139b of the second substrate 152, each antenna is individually, electrically connected. This renders the bias wiring layer 102 of the antenna array and the transistor TRa of the integrated circuit region 154 conductive, thereby making it possible to individually apply a control signal to each antenna. When the MOSFET of the transistor TRb also serves as a bias control unit, and operates as a switching regulator, the bias control wiring layer 102 individually controls a bias signal to the semiconductor layer 100. An arrangement in which a voltage is supplied from the outside of the second substrate 152 by additionally providing a terminal for applying a bias signal on the second substrate 152 and causing the transistor TRa to operate as an analog switch for individually turning on/off the antenna may be adopted. With this arrangement, a phase difference is given between adjacent antennas by individually changing the bias of each active antenna, thereby making it possible to implement beamforming.
To generate a terahertz wave, in the semiconductor layer 100, an upper electrode layer 163, a semiconductor structure 162, and a lower electrode layer 164 are stacked in this order. The semiconductor structure 162 is the RTD formed in the semiconductor layer having nonlinearity or an electromagnetic wave gain with respect to a terahertz wave. The upper electrode layer 163 and the lower electrode layer 164 have a structure including an electrode layer for connecting contact electrodes above and below the semiconductor structure 162 and upper and lower wiring layers in order to apply a potential difference or a current to the RTD as the semiconductor structure 162. In this structure, the upper electrode layer 163 is connected to the via 103 and the lower electrode layer 164 is connected to the conductor layer 109, thereby giving a potential difference or a current to the semiconductor structure 162. Therefore, it can be said that the upper electrode layer 163 and the via 103, and the lower electrode layer 164 and the conductor layer 109 are connected to two power lines, respectively.
To apply a bias control signal to the semiconductor layer 100, a common bias wiring layer 102 is provided for all the active antennas AA1 to AA9. The position of the wiring layer 102 is set to be connected, at the position of the node of a resonance electric field formed on the active antennas AA1 to AA9 at a frequency fTHz, to the active antennas AA1 to AA9 by vias 107a and 107b arranged for the respective antennas. The wiring layer 102 is connected to a MIM capacitor 126 and a resistance layer 127 arranged for each antenna, and AC short-circuits a high frequency other than the frequency fTHz, thereby reducing an impedance at the high frequency. This suppresses multi-mode oscillation in the array antenna.
Each of the active antennas AA1 to AA9 has a via 130 for coupling an injection locking signal from a master oscillator 60. The via 130 is capacitively coupled to the conductor layer 101 of the active antenna via a capacitor C, and the master oscillator 60 and the active antenna AA are electrically connected to be short-circuited with respect to a terahertz band and to be open with respect to an RF band. Furthermore, the connection position of the via 130 is set to be connected at the position of the node of the resonance electric field of the frequency fTHz in each of the active antennas AA1 to AA9. Thus, the via 130 has a high impedance at the frequency fTHz and a low impedance at a subharmonic frequency in the antenna, thereby implementing the terahertz radiation efficiency and the injection efficiency of a master signal.
The master oscillator 60 is an oscillation source that oscillates at the subharmonic frequency (for example, fTHz/2) of the terahertz wave, and controls the phase of each active antenna. The master oscillator 60 outputs a signal of an output larger than the output of a single active antenna serving as a slave. The active antenna AA is electrically connected, via the via 130 for master oscillation, to the gate of a transistor TRa (MOSFET) of the master oscillator 60 provided in the integrated circuit region 154 of the second substrate 152. The via 130 for master synchronization formed in the dielectric layers 104 and 105 of the first substrate 151 is electrically connected to a wiring layer 135a provided in an opening 136a of the conductor layer 109, a through via 137a provided in the insulator layer 131, and a bonding electrode layer 138a in this order to be electrically connected to the bonding surface B.S. Similarly, the transistor TRa formed in the integrated circuit region 154 of the second substrate 152 is electrically connected to a via 141a formed in the integrated circuit region 154 and a bonding electrode layer 139a in this order to be electrically connected to the bonding surface B.S.
The electrode layer 138a of the first substrate 151 and the electrode layer 139a of the second substrate 152 are electrically bonded at the bonding surface B.S. Therefore, the active antennas AA1 to AA9 and the transistor TRa for individually controlling each antenna arranged in the integrated circuit region 154 are rendered conductive in the terahertz band, thereby making it possible to apply a control signal. Each active antenna forms, with the upper electrode layer 163, the via 103, the lower electrode layer 164, and the conductor layer 109, a bias structure that gives a potential difference from above and below the semiconductor structure 162. A subharmonic signal from the master oscillator 60 is injected into the semiconductor layers 100a and 100b via the bias structure. Therefore, a power signal of the subharmonic frequency (for example, fTHz/2) from the master oscillator 60 is injected into the semiconductor layers 100a and 100b each formed from the RTD having the role of the oscillation source in the antenna, thereby making it possible to control the phase of each active antenna. The device having such arrangement serves as a master oscillator that is a low frequency oscillation circuit for outputting a low frequency (fTHz/n, n is a natural number) of 1/integer of the terahertz band, thereby performing mutual injection locking for the active antenna operating at the frequency fTHz. This can execute timing control of the active antenna array at the frequency fTHz, thereby reducing phase noise.
As the fourth embodiment, an example of using the present invention for a reception apparatus will be described.
Each reception antenna 503 is a patch antenna having a structure in which a negative resistance element 300 and a dielectric 312 are sandwiched by a conductor layer 507 as an upper conductor for the reception antenna and a conductor layer 309 as a reflector. The upper terminal of the negative resistance element 300 is electrically connected to a via 301, and the via 301 is electrically connected to the conductor layer 507. Furthermore, the lower terminal of the negative resistance element 300 is electrically connected to the conductor layer 309 also serving as GND. The conductor layer 507 is set to be connected to a conductor layer 303 for an individual bias via a feeding via 307 for supplying power for a bias at the position of the node of a resonance electric field at a frequency fTHz. This structure can apply a bias above and below the negative resistance element 300. The conductor layer 303 is connected to a MIM capacitor 320 via a MIM capacitor connection portion 321. The MIM capacitor connection portion 321 includes a resistance layer using TiW, and plays the role of an AC short circuit series-connected to the MIM capacitor structure. If a signal of a predetermined bias voltage for generating a negative resistance is applied to the negative resistance element, self-oscillation is performed. At this time, destabilization of oscillation and a decrease in output caused by a parasitic oscillation are prevented. The transmission antenna 504 has substantially the same arrangement as that of the reception antenna except that a conductor layer 1001 as an upper conductor for the transmission antenna is provided. These antennas are connected by a plurality of transmission lines 1808a to 1808r and synchronized.
Referring to
Referring to
Bias control will be described. A through via 305 connected to the conductor layer 303, a wiring layer 135b provided in an opening 136b of the conductor layer 309 as a reflector, and a through via 137b formed in the semiconductor substrate 302 are electrically connected, in this order, to the conductor layer (electrode layer) 1910 that forms an electrode as a bias terminal formed on the bonding surface B.S. Similarly, in the second substrate 152, the conductor layer 1911 as a bias terminal formed on the bonding surface B.S. is electrically connected to a MOSFET 322 as a transistor formed in the integrated circuit region 154. The MOSFET 322 forms a gate-grounded amplification circuit as an amplifier of the first stage. An amplified signal is further amplified by a source-grounded amplification circuit including a MOSFET 324. The gate-grounded amplification circuit and the source-grounded amplification circuit are coupled by a MIM capacitor 323 for AC coupling. The MIM capacitor 323 is merely an example, and may have an arrangement using the gate insulating film capacity of an FET. The MOSFET 322 also serves as a bias control unit, and the semiconductor substrate is connected via the MOSFET 322 to apply a bias voltage to the negative resistance element 300. Alternatively, an arrangement in which a terminal for applying a bias voltage may be provided on the second substrate 152 and a voltage is externally supplied may be adopted.
As in this embodiment, the first substrate 151 including the transmission/reception active antennas and the second substrate 152 including the electronic integrated circuit are bonded by a semiconductor bonding technique, thereby eliminating the need to integrate or implement the control circuit of the active antennas on the same plane. This reduces the space in the antenna, where the control circuit is arranged on the same plane, and it is possible to prevent the characteristic of the antenna from degrading due to coupling between the control circuit and the antennas. If bias control and the like are individually executed for each antenna, it is necessary to prepare a bias terminal for each antenna. However, in this embodiment, it is possible to readily perform connection to the integrated circuit region 154 by the through via 305. In this way, if the control circuit can be wired on the rear side of the first substrate 151, even if the active antenna array is used as in the above-described embodiment, it is possible to increase the number of antenna arrays without receiving the influence of an arrangement restriction and the like. Since the electronic integrated circuit of the second substrate 152 as the control circuit is made by the conventional CMOS technique, a complex circuit can be formed as a detection circuit or a signal processing circuit. This can broaden the utility of the terahertz wave reception apparatus using the active antennas according to this embodiment.
This embodiment will describe a case in which the antenna apparatus of one of the above-described embodiments is applied to a terahertz camera system (image capturing system). The following description will be provided with reference to
The terahertz wave emitted from the transmission unit 1101 is reflected by an object 1105, and detected by the reception unit 1102. The camera system including the transmission unit 1101 and the reception unit 1102 can also be called an active camera system. Note that in a passive camera system without including the transmission unit 1101, the antenna apparatus of each of the above-described embodiments can be used as the reception unit 1102.
By using the antenna apparatus of each of the above-described embodiments that can perform beamforming, it is possible to improve the detection sensitivity of the camera system, thereby obtaining a high quality image.
This embodiment will describe a case in which the antenna apparatus of one of the above-described embodiments is applied to a terahertz communication system (communication apparatus). The following description will be provided with reference to
The embodiments of the present invention have been described above. However, the present invention is not limited to these embodiments and various modifications and changes can be made within the spirit and scope of the present invention.
For example, each of the above-described embodiments assumes that carriers are electrons. However, the present invention is not limited to this and holes may be used. Furthermore, the materials of the substrate and the dielectric are selected in accordance with an application purpose, and a semiconductor layer of silicon, gallium arsenide, indium arsenide, gallium phosphide, or the like, glass, ceramic, and a resin such as polytetrafluoroethylene or polyethylene terephthalate can be used.
In each of the above-described embodiments, a square patch antenna is used as a terahertz wave resonator but the shape of the resonator is not limited to this. For example, a resonator having a structure using a patch conductor having a polygonal shape such as a rectangular shape or triangular shape, a circular shape, an elliptical shape, or the like may be used.
The number of negative differential resistance elements integrated in an element is not limited to one and a resonator including a plurality of negative differential resistance elements may be used. The number of lines is not limited to one, and an arrangement including a plurality of lines may be used. By using the antenna apparatus described in each of the above embodiments, it is possible to oscillate and detect a terahertz wave.
In each of the above-described embodiments, a double-barrier RTD made of InGaAs/AlAs growing on the InP substrate has been described as an RTD. However, the present invention is not limited to the structure and material system, and even another combination of a structure and a material can provide an element of the present invention. For example, an RTD having a triple-barrier quantum well structure or an RTD having a multi-barrier quantum well structure of four or more barriers may be used. It can be said that the RTD includes bonding between different semiconductors, that is, heterojunction.
As the material of the RTD, each of the following combinations may be used.
The above-described structure and material can appropriately be selected in accordance with a desired frequency and the like.
Furthermore, as the semiconductor layer 100, a Quantum Cascade Laser (QCL) having a semiconductor multilayer structure of several hundred to several thousand layers may be used. In this case, the semiconductor layer 100 is a semiconductor layer including the QCL structure. As the semiconductor layer 100, a negative resistance element such as a Gunn diode or IMPATT diode often used in the millimeter wave band may be used. As the semiconductor layer 100, a high frequency element such as a transistor with one terminal terminated may be used, and a heterojunction bipolar transistor (HBT), a compound semiconductor field effect transistor (FET), a high electron mobility transistor (HEMT), or the like is preferably used as the transistor. As the semiconductor layer 100, a negative differential resistance of the Josephson device using a superconductor layer may be used. As the semiconductor layer 100, an element including heterojunction may be used.
Any form of the relationship between the active antenna array 11 and the control circuit 165 may be possible. The active antenna array 11 includes a plurality of active antennas AA11 to AAmn, and the control circuit 165 includes a plurality of control elements AC11 to ACmn.
Each of the plurality of active antennas AA11 to AAmn may be controlled by a signal from each of the control elements AC11 to ACmn. That is, one control element may control one active antenna. It is possible to increase the degree of freedom of control of the antenna. Note that the control circuit 165 is not limited to the form including the plurality of control elements AC11 to ACmn, and need only be able to individually control the active antennas.
Furthermore, one control element may control a plurality of active antennas included in one group. In this case, the plurality of active antennas included in one group can correspond to each row or each column of the plurality of active antennas AA11 to AAmn arranged in a matrix. The plurality of active antennas included in one group can correspond to each region of a plurality of rows and a plurality of columns. Each group of the plurality of active antennas is operated, thereby facilitating control. In addition, the output can be increased for each group of the plurality of active antennas.
Furthermore, a plurality of control elements may control one active antenna. In this case, the degree of freedom of the operation can be increased. For example, each active antenna is controlled at each timing, or a plurality of active antennas are controlled at each timing.
If a complicated operation is performed, the above connection methods can arbitrarily be combined.
At least some of the above embodiments can be summarized as follows.
Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD) (registered trademark)), a flash memory device, a memory card, and the like.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-067824 | Apr 2022 | JP | national |
This application is a national phase of PCT Application No. PCT/JP2023/014967, filed Apr. 13, 2023, which in turn claims benefit of Japanese Patent Application No. 2022-067824 filed Apr. 15, 2022, the contents of each of which is incorporated by reference herein.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2023/014967 | 4/13/2023 | WO |
