Reconfigurable transmitarray antenna with monolithic integration of elementary cells

Abstract

A structure including a first wafer, including first active components configured so as to introduce a phase shift; a first metal layer, formed on a first surface of the first wafer; a first interconnect structure, formed on a second surface of the first wafer, including first bias lines; a set of first planar antennas, formed on the first interconnect structure; a second wafer; a second metal layer, formed on a first surface of the second wafer; a set of second planar antennas, formed on a second surface of the second wafer; the first and second wafers being joined by way of the first and second metal layers such that the first and second planar antennas are aligned, the first and second metal layers forming a ground plane.

Claims

1. A structure for manufacturing integrated circuits that are intended to provide an electromagnetic lens function for a reconfigurable transmitarray antenna, the structure comprising: a first wafer, comprising a set of first active components configured so as to introduce a phase shift, and having opposing first and second surfaces; a first metal layer, formed on the first surface of the first wafer; a first interconnect structure, formed on the second surface of the first wafer, and electrically connected to the first active components; the first interconnect structure comprising first bias lines designed to bias the first active components; a set of first planar antennas, formed on the first interconnect structure; a second wafer, having opposing first and second surfaces; a second metal layer, formed on the first surface of the second wafer; a set of second planar antennas, formed on the second surface of the second wafer; the first and second wafers being joined by way of the first and second metal layers such that the sets of the first and second planar antennas are aligned, the first and second metal layers forming a ground plane.

2. The structure according to claim 1, wherein the set of first active components comprises pairs of switches, each pair of switches being associated with a first planar antenna.

3. The structure according to claim 1, wherein the first wafer comprises a first demultiplexer configured so as to transmit a control signal on the first bias lines.

4. The structure according to claim 1, wherein the second wafer comprises a set of second active components configured so as to introduce a phase shift; the structure further comprising a second interconnect structure, formed on the second surface of the second wafer, and electrically connected to the second active components; the second interconnect structure comprising second bias lines designed to bias the second active components; the set of second planar antennas being formed on the second interconnect structure.

5. The structure according to claim 4, wherein the set of second active components comprises pairs of switches, each pair of switches being associated with a second planar antenna.

6. The structure according to claim 4, wherein the second wafer comprises a second demultiplexer configured so as to transmit a control signal on the second bias lines.

7. The structure according to claim 1, further comprising vias designed to electrically connect the first planar antennas with the second planar antennas facing them, the vias being electrically isolated from the ground plane.

8. The structure according to claim 7, wherein each first planar antenna comprises separate first and second radiating surfaces; the first radiating surfaces of the first planar antennas being electrically connected to the vias; the second radiating surfaces of the first planar antennas being electrically connected to the first active components.

9. The structure according to claim 7, wherein the second wafer comprises a set of second active components configured so as to introduce a phase shift; the structure further comprising a second interconnect structure, formed on the second surface of the second wafer, and electrically connected to the second active components; the second interconnect structure comprising second bias lines designed to bias the second active components; the set of second planar antennas being formed on the second interconnect structure; wherein each second planar antenna comprises separate first and second radiating surfaces; the first radiating surfaces of the second planar antennas being electrically connected to the vias; the second radiating surfaces of the second planar antennas being electrically connected to the second active components.

10. The structure according to claim 1, wherein the first active components are chosen from among a diode, a field-effect transistor, a bipolar transistor, a microelectromechanical system.

11. The structure according to claim 1, further comprising solder balls designed to establish a metallic bond between the first and second metal layers.

12. The structure according to claim 1, wherein the first and second wafers are based on a semiconductor material, or consist of a semiconductor material.

13. An integrated circuit, intended to provide an electromagnetic lens function for a reconfigurable transmitarray antenna, the integrated circuit comprising: a portion of a first wafer, comprising first active components configured so as to introduce a phase shift, and having opposing first and second surfaces; a part of a first metal layer, formed on the first surface of the portion of the first wafer; a part of a first interconnect structure, formed on the second surface of the portion of the first wafer, and electrically connected to the first active components; the part of the first interconnect structure comprising first bias lines designed to bias the first active components; a part of a set of first planar antennas, formed on the part of the first interconnect structure; a portion of a second wafer, having opposing first and second surfaces; a part of the second metal layer, formed on the first surface of the portion of the second wafer; a part of a set of second planar antennas, formed on the second surface of the portion of the second wafer; the portions of the first and second wafers being joined by way of the parts of the first and second metal layers such that the parts of the sets of the first and second planar antennas are aligned, the parts of the first and second metal layers forming a ground plane, the integrated circuit comprising a plurality of elementary cells, each comprising a first planar antenna and a second planar antenna facing it, so as to provide an electromagnetic lens function.

14. A reconfigurable transmitarray antenna, comprising: a printed circuit board, having opposing first and second surfaces; at least one integrated circuit according to claim 13, formed on the first surface of the printed circuit board; at least one transceiver, designed to emit and receive an electromagnetic wave propagating within the printed circuit board; at least one control electronics component, configured so as to control the transceiver and the first active components of the at least one integrated circuit, and formed on the second surface of the printed circuit board.

15. The antenna according to claim 14, wherein the at least one integrated circuit is manufactured by cutting the first interconnect structure, and the at least one control electronics component is configured so as to control second active components of the at least one integrated circuit.

16. The antenna according to claim 14, further comprising additional planar antennas formed on the first surface of the printed circuit board, and facing the elementary cells of the at least one integrated circuit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other features and advantages will become apparent in the detailed description of various embodiments of the invention, the description being accompanied by examples and references to the accompanying drawings.

(2) FIG. 1 is a partial schematic sectional view of a structure according to the invention, illustrating the first wafer provided with the first active components, the first interconnect structure, the first planar antennas and the first metal layer.

(3) FIG. 2 is a partial schematic sectional view of a structure according to the invention, illustrating a first embodiment where the second wafer does not have any active components.

(4) FIG. 3 is a partial schematic sectional view of a structure according to the invention, illustrating a second embodiment where the second wafer is provided with second active components.

(5) FIG. 4 is a schematic sectional view of a structure according to the invention, illustrating an embodiment where the second wafer does not have any active components. The dashed lines indicate an elementary cell of the transmitarray.

(6) FIG. 5 is a schematic sectional view of a structure according to the invention, illustrating an embodiment where the second wafer is provided with second active components. The dashed lines indicate an elementary cell of the transmitarray.

(7) FIG. 6 is a schematic plan view of a structure according to the invention, illustrating the formation of patterns on the surface of the structure, for example through photolithography using a mask (reticle). The excerpt in FIG. 6 is a magnified plan view of a pattern, formed on the surface of the structure, and comprising a plurality of elementary cells.

(8) FIG. 7 is a schematic sectional view of a reconfigurable antenna according to the invention.

(9) FIG. 8 is a schematic plan view of a reconfigurable antenna according to the invention.

(10) FIG. 9 is a schematic sectional view of a reconfigurable antenna according to the invention, illustrating an embodiment where additional planar antennas are formed on the surface of the printed circuit board.

(11) FIG. 10 is a schematic sectional view of a reconfigurable antenna according to the invention, illustrating an embodiment where the printed circuit board is provided with a plurality of transceiver modules. The dashed lines indicate a beamforming region over a bandwidth.

(12) FIG. 11 is a schematic sectional view of a reconfigurable antenna according to the invention, illustrating an embodiment where the printed circuit board is provided with a digital transceiver module. The dashed lines indicate a beamforming region over a bandwidth.

(13) The figures are not shown to scale for the sake of legibility and for ease of understanding thereof.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(14) Elements that are identical or perform the same function will bear the same references for the various embodiments, for the sake of simplicity.

(15) One subject of the invention is a structure 1 for manufacturing integrated circuits IC that are intended to provide an electromagnetic lens function for a reconfigurable transmitarray antenna 2, the structure 1 comprising:

(16) a first wafer W1, comprising a set of first active components C1 configured so as to introduce a phase shift, and having opposing first and second surfaces W10, W11;

(17) a first metal layer M1, formed on the first surface W10 of the first wafer W1;

(18) a first interconnect structure 3, formed on the second surface W11 of the first wafer W1, and electrically connected to the first active components C1; the first interconnect structure 3 comprising first bias lines 30 designed to bias the first active components C1;

(19) a set of first planar antennas A1, formed on the first interconnect structure 3;

(20) a second wafer W2, having opposing first and second surfaces W20, W21;

(21) a second metal layer M2, formed on the first surface W20 of the second wafer W2;

(22) a set of second planar antennas A2, formed on the second surface W21 of the second wafer W2;

(23) the first and second wafers W1, W2 being joined by way of the first and second metal layers M1, M2 such that the sets of the first and second planar antennas A1, A2 are aligned, the first and second metal layers M1, M2 forming a ground plane PM.

(24) Some examples of a structure 1 are illustrated in FIGS. 4 and 5.

(25) First Wafer

(26) The first wafer W1 is notably illustrated in FIG. 1. The first wafer W1 is advantageously made from a semiconductor material, preferably selected from among silicon and germanium. The first wafer W1 may therefore be a semiconductor. The first wafer W1 may be based on a semiconductor material. The first wafer W1 may consist of a semiconductor material.

(27) The first wafer W1 may also be made from a dielectric material such as quartz. It is also possible to contemplate a semiconductor-on-insulator (SeOI) first wafer W1, preferably a silicon-on-insulator (SOI) first wafer.

(28) First Active Components

(29) The first active components C1 are advantageously integrated into the first wafer W1 by an FEOL (“Front-End-Of-Line”) initial manufacturing unit, using for example photolithography, etching, dopant diffusion and implantation, metal deposition, passivation techniques known to a person skilled in the art. If the first wafer W1 is made from a dielectric material, the first active components C1 may be integrated into the first wafer W1 using thin-film deposition techniques.

(30) Each first planar antenna A1 advantageously comprises separate first and second radiating surfaces A10, A11, separate in the sense that they are separated from one another by a separating region so as to be electrically isolated from one another. The set of first active components C1 advantageously comprises pairs of switches, each pair of switches being associated with a first planar antenna A1. Each pair of switches belongs to a phase shift circuit, and comprises first and second switches respectively alternately having an on state and an off state, the on or off states corresponding to a respectively authorized or blocked flow of a current between the separate first and second radiating surfaces A10, A11 of each first planar antenna A1. “Alternately” is understood to mean that the first switch alternates between the on state and the off state, while, simultaneously, the second switch alternates between the off state and the on state. In other words, at all times, the first and second switches belonging to the same phase shift circuit have two opposing states, either on/off or off/on. On/on or off/off states are not authorized.

(31) The first active components C1 are advantageously chosen from among a diode, a field-effect transistor, a bipolar transistor, a microelectromechanical system. The field-effect transistor is preferably a MOS (“Metal Oxide Semiconductor”) transistor. The diode may be a PIN diode, an electro-optical diode, or else a varactor diode. PIN diodes may be made from AlGaAs.

(32) First Metal Layer

(33) The first metal layer M1 is preferably made from copper. The first metal layer M1 may be formed on the first surface W10 of the first wafer W1 through a metallization process.

(34) First Interconnect Structure

(35) The first interconnect structure 3 is advantageously formed on the second surface W11 of the first wafer W1 by a BEOL (“Back-End-Of-Line”) final manufacturing unit.

(36) The first bias lines 30 are metal tracks, preferably made from copper.

(37) The first wafer W1 advantageously comprises a first demultiplexer DMUX1 configured so as to transmit a control signal on the first bias lines 30. In order to limit the number of inputs (and therefore the number of wires), for the sake of compactness, it is possible to organize the first bias lines 30 in matrices, and to provide an address decoder.

(38) Set of First Planar Antennas

(39) The set of first planar antennas A1 is formed on the first interconnect structure 3 such that each first planar antenna A1 is electrically connected to the first active components C1. The set of first planar antennas A1 is formed on the first interconnect structure 3 such that the first planar antennas A1 are electrically isolated from one another so as not to be short-circuited.

(40) As mentioned above, each first planar antenna A1 advantageously comprises separate first and second radiating surfaces A10, A11, separate in the sense that they are separated from one another by a separating region so as to be electrically isolated from one another. To this end, a slot is advantageously formed in each first planar antenna A1 in order to electrically isolate the separate first and second radiating surfaces A10, A11. The slot defines the separating region. The slot is preferably annular, with a rectangular cross section. Of course, other shapes may be contemplated for the slot, such as an elliptical or circular shape. According to one variant implementation, the first and second radiating surfaces of the second planar antenna may be electrically isolated by a dielectric material.

(41) The first and second radiating surfaces A10, A11 of the first planar antennas A1 are electrically connected to the first active components C1

(42) Second Wafer

(43) The second wafer W2 is notably illustrated in FIGS. 2 and 3. The second wafer W2 is advantageously made from a semiconductor material, preferably selected from among silicon and germanium. The second wafer W2 may therefore be a semiconductor. The second wafer W2 may be based on a semiconductor material. The second wafer W2 may consist of a semiconductor material.

(44) The second wafer W2 may also be made from a dielectric material such as quartz. It is also possible to contemplate a semiconductor-on-insulator (SeOI) second wafer W2, preferably a silicon-on-insulator (SOI) second wafer.

(45) Second Active Components

(46) The second wafer W2 advantageously comprises a set of second active components C2 configured so as to introduce a phase shift. The second active components C2 are advantageously integrated into the second wafer W2 by an FEOL (“Front-End-Of-Line”) initial manufacturing unit, using for example photolithography, etching, dopant diffusion and implantation, metal deposition, passivation techniques known to a person skilled in the art. If the second wafer W2 is made from a dielectric material, the second active components C2 may be integrated into the second wafer W2 using thin-film deposition techniques.

(47) Each second planar antenna A2 advantageously comprises separate first and second radiating surfaces A20, A21, separate in the sense that they are separated from one another by a separating region so as to be electrically isolated from one another. The set of second active components C2 advantageously comprises pairs of switches, each pair of switches being associated with a second planar antenna A2. Each pair of switches belongs to a phase shift circuit, and comprises first and second switches respectively alternately having an on state and an off state, the on or off states corresponding to a respectively authorized or blocked flow of a current between the separate first and second radiating surfaces A20, A21 of each second planar antenna A2. “Alternately” is understood to mean that the first switch alternates between the on state and the off state, while, simultaneously, the second switch alternates between the off state and the on state. In other words, at all times, the first and second switches belonging to the same phase shift circuit have two opposing states, either on/off or off/on. On/on or off/off states are not authorized.

(48) The second active components C2 are advantageously chosen from among a diode, a field-effect transistor, a bipolar transistor, a microelectromechanical system. The field-effect transistor is preferably a MOS (“Metal Oxide Semiconductor”) transistor. The diode may be a PIN diode, an electro-optical diode, or else a varactor diode. PIN diodes may be made from AlGaAs.

(49) Second Metal Layer

(50) The second metal layer M2 is preferably made from copper. The second metal layer may be formed on the first surface W20 of the second wafer W2 through a metallization process.

(51) Second Interconnect Structure

(52) The structure 1 advantageously comprises a second interconnect structure 4, formed on the second surface W21 of the second wafer W2, and electrically connected to the second active components C2. The second interconnect structure 4 is advantageously formed on the second surface W21 of the second wafer W2 by a BEOL (“Back-End-Of-Line”) final manufacturing unit. The set of second planar antennas A2 is then formed on the second interconnect structure 4.

(53) The second interconnect structure 4 comprises second bias lines 40 designed to bias the second active components C2. The second bias lines 40 are metal tracks, preferably made from copper.

(54) The second wafer W2 advantageously comprises a second demultiplexer DMUX2 configured so as to transmit a control signal on the second bias lines 40. In order to limit the number of inputs (and therefore the number of wires), for the sake of compactness, it is possible to organize the second bias lines 40 in matrices, and to provide an address decoder.

(55) Set of Second Planar Antennas

(56) The set of second planar antennas A2 is formed on the second interconnect structure 4 such that each second planar antenna A2 is electrically connected to the second active components C2. The set of second planar antennas A2 is formed on the second interconnect structure 4 such that the second planar antennas A2 are electrically isolated from one another so as not to be short-circuited.

(57) As mentioned above, each second planar antenna A2 advantageously comprises separate first and second radiating surfaces A20, A21, separate in the sense that they are separated from one another by a separating region so as to be electrically isolated from one another. To this end, a slot is advantageously formed in each second planar antenna A2 in order to electrically isolate the separate first and second radiating surfaces A20, A21. The slot defines the separating region. The slot is preferably annular, with a rectangular cross section. Of course, other shapes may be contemplated for the slot, such as an elliptical or circular shape. According to one variant implementation, the first and second radiating surfaces of the second planar antenna may be electrically isolated by a dielectric material.

(58) The first and second radiating surfaces A20, A21 of the second planar antennas A2 are electrically connected to the second active components C2.

(59) Joining of the First and Second Wafers

(60) By way of non-limiting example, the ground plane PM may have a thickness of the order of 17 μm when the operating frequency of the transmitarray antenna 2 is 29 GHz.

(61) The structure 1 advantageously comprises solder balls designed to establish a metallic bond between the first and second metal layers M1, M2. According to one alternative, the first and second wafers W1, W2 may be joined by way of the first and second metal layers M1, M2 through eutectic bonding.

(62) The first and second wafers W1, W2 are joined such that the sets of the first and second planar antennas A1, A2 are aligned. The sets of the first and second planar antennas A1, A2 may be aligned using an alignment technique known to a person skilled in the art, for example using CCD (“Charge Coupled Device”) cameras.

(63) After joining the first and second wafers W1, W2, the surface of the structure 1 is divided into patterns 10, as illustrated in FIG. 6. The patterns 10 are formed on the surface of the structure 1, for example through photolithography using a mask (reticle). By way of non-limiting example, each pattern 10 may be square in shape (D being the dimension of the sides) and may have a surface area of 20×20 mm.sup.2 when the first and second wafers W1, W2 have a diameter of 200 mm. The number of elementary cells CE present in a pattern 10 depends on the operating frequency of the antenna 2, which defines the pitch p of the elementary cells CE. By way of non-limiting example, for an operating frequency of 28 GHz, a square pattern 10 with a surface area of 20×20 mm.sup.2 may contain 3×3 elementary cells CE.

(64) Electrical Connection Between the First and Second Planar Antennas

(65) The structure 1 advantageously comprises vias V designed to electrically connect the first planar antennas A1 with the second planar antennas A2 facing them, the vias V being electrically isolated from the ground plane PM. The vias V pass through apertures formed in the ground plane PM. The apertures formed in the ground plane PM allow both electrical isolation with the vias V and the propagation of electromagnetic waves through the ground plane PM. When the first and second wafers W1, W2 are made of silicon, the vias V are TSVs (“Through Silicon Vias”). By way of example, for an operating frequency of 29 GHz, the vias V have a diameter of the order of 150 μm. The vias V are preferably connected to the first and second planar antennas A1, A2 by connection points. In general, the position of the connection points varies depending on the specific geometry of the planar antennas, so as to excite the fundamental mode of resonance. The vias V advantageously extend along the normal to the surfaces of the first and second planar antennas A1, A2.

(66) When each first planar antenna A1 has separate first and second radiating surfaces A10, A11, the first radiating surfaces A10 of the first planar antennas A1 are electrically connected to the vias V.

(67) When each second planar antenna A2 has separate first and second radiating surfaces A20, A21, the first radiating surfaces A20 of the second planar antennas A2 are electrically connected to the vias V.

(68) Integrated Circuit

(69) One subject of the invention is an integrated circuit IC, manufactured by cutting a structure 1 according to the invention, the cutting being performed such that the integrated circuit IC comprises a plurality of elementary cells CE, each comprising a first planar antenna A1 and a second planar antenna A2 facing it, so as to provide an electromagnetic lens function.

(70) The cutting may be performed using a precision circular saw, with a metal core or resinoid diamond core blade. The cutting is performed along the normal to the surfaces W10, W11; W20, W21 of the first and second wafers W1, W2.

(71) In other words, one subject of the invention is an integrated circuit IC, intended to provide an electromagnetic lens function for a reconfigurable transmitarray antenna 2, manufactured by cutting a structure 1 according to the invention, the integrated circuit IC comprising:

(72) a portion of the first wafer W1, comprising first active components C1 configured so as to introduce a phase shift, and having opposing first and second surfaces W10, W11;

(73) a part of the first metal layer M1, formed on the first surface W10 of the portion of the first wafer W1;

(74) a part of the first interconnect structure 3, formed on the second surface W11 of the portion of the first wafer W1, and electrically connected to the first active components C1; the part of the first interconnect structure 3 comprising first bias lines 30 designed to bias the first active components C1;

(75) a part of the set of first planar antennas A1, formed on the part of the first interconnect structure 3;

(76) a portion of the second wafer W2, having opposing first and second surfaces W20, W21;

(77) a part of the second metal layer M2, formed on the first surface W20 of the portion of the second wafer W2;

(78) a part of the set of second planar antennas A2, formed on the second surface W21 of the portion of the second wafer W2;

(79) the portions of the first and second wafers W1, W2 being joined by way of the parts of the first and second metal layers M1, M2 such that the parts of the sets of the first and second planar antennas A1, A2 are aligned, the parts of the first and second metal layers M1, M2 forming a ground plane PM.

(80) The integrated circuit IC comprises a plurality of elementary cells CE, each comprising a first planar antenna A1 and a second planar antenna A2 facing it, so as to provide an electromagnetic lens function.

(81) Reconfigurable Antenna

(82) As illustrated in FIG. 7, one subject of the invention is a reconfigurable transmitarray antenna 2, comprising:

(83) a printed circuit board 5, having opposing first and second surfaces 50, 51;

(84) at least one integrated circuit IC according to the invention, formed on the first surface 50 of the printed circuit board 5;

(85) at least one transceiver 6, designed to emit and receive an electromagnetic wave propagating within the printed circuit board 5;

(86) at least one control electronics component 60, configured so as to control the transceiver 6 and the first active components C1 of the integrated circuit IC, and formed on the second surface 51 of the printed circuit board 5.

(87) Printed Circuit Board

(88) The printed circuit board 5 is made of a dielectric material. By way of non-limiting example, the printed circuit board 5 may be made of a commercial material such as RT/duroid® 6002. The printed circuit board 5 has a thickness typically of between 100 μm and 1500 μm for an operating frequency of the antenna 2 of between 10 GHz and 300 GHz. By way of non-limiting example, the printed circuit board 5 may have a thickness of the order of 254 μm when the operating frequency of the antenna 2 is 29 GHz.

(89) The integrated circuit or integrated circuits IC may be formed on the first surface 50 of the printed circuit board 5 through a flip-chip bonding operation. The integrated circuits IC may be arranged on the first surface 50 of the printed circuit board 5 in the form of a matrix, as illustrated in FIG. 8.

(90) As illustrated in FIG. 9, the antenna 2 advantageously comprises additional planar antennas A1′ formed on the first surface 50 of the printed circuit board 5, and facing the elementary cells CE of the integrated circuit IC.

(91) Transceiver

(92) Each transceiver 6 comprises at least one radiating source S designed to emit electromagnetic waves. The radiating source S may be embodied in the form of a planar antenna formed within the printed circuit board 5, extending in a focal plane whose Euclidean distance to the electromagnetic lens defines the focal length F (illustrated in FIG. 7). The or each radiating source S is advantageously configured so as to operate at a frequency greater than 30 GHz (millimetre and sub-THz frequencies).

(93) As illustrated in FIG. 10, the antenna 2 may comprise a plurality of transceivers 6. When the integrated circuits IC are arranged on the first surface 50 of the printed circuit board 5 in matrix form, each transceiver 6 may be dedicated to a region of the matrix.

(94) As illustrated in FIG. 11, the plurality of transceivers 6 may be controlled by digital control electronics 60, the output channels of which are electrically connected to the radiating sources S.

(95) Control Electronics

(96) The control electronics 60 are preferably integrated within an electronic chip mounted on the second surface 51 of the printed circuit board 5. The control electronics 60 are advantageously configured so as to also control the second active components C2 of the integrated circuit IC.

(97) In the absence of demultiplexers DMUX1, DMUX2 integrated into the first and second wafers W1, W2, demultiplexers may be moved to within the control electronics 60. One example of controlling bias lines is given in the doctoral thesis “Conception d'antennes à réseaux transmetteurs à dépointage et/ou formation de faisceau” [Design of depointing and/or beamforming transmitarray antennas], A. Clemente, October 2012, on pages 159-161.

(98) The invention is not limited to the embodiments disclosed. A person skilled in the art has the ability to consider technically operative combinations thereof and to substitute them for equivalents.