Electronic filtering circuit

Abstract

Electronic filtering circuit The present description relates to an electronic filtering circuit (100) comprising: – an integrated passive device (101); – a bulk acoustic wave filter (151) superimposed on the integrated passive device (101) on the side of a first face (103B) of the integrated passive device (101); and – at least one conductive pillar (181) passing through the integrated passive device (101) and connecting an electrode (157) of the bulk acoustic wave filter (151) to a contact recovery element (113) located on a second face (103A) of the integrated passive device (101) opposite the first face (103B) and intended to be connected to an external element (117). Figure for abstract: Fig. 1

Description

Title of the invention: Electronic filtering circuit Technical field

[0001] The present description relates generally to electronic devices, more particularly to electronic filtering circuits. Prior art

[0002] Many electronic devices include at least one electronic filtering circuit. Such circuits are, for example, integrated into mobile phones, or smartphones, to prevent the operation of a radiofrequency communications reception channel of the phone from being disturbed by interference caused by radiofrequency signals emitted by other electronic devices, or by noise from external radiofrequency sources. However, existing electronic filtering circuits suffer from various drawbacks. Summary of the invention

[0003] There is a need to overcome all or part of the disadvantages of existing electronic filtering circuits.

[0004] For this, one embodiment provides an electronic filtering circuit comprising: - an integrated passive device; - a bulk acoustic wave filter superimposed on the integrated passive device on the side of a first face of the integrated passive device; and - at least one conductive pillar passing through the integrated passive device and connecting an electrode of the bulk acoustic wave filter to a contact recovery element located on a second face of the integrated passive device opposite the first face and intended to be connected to an external element.

[0005] According to one embodiment, the integrated passive device forms a cover of the bulk acoustic wave filter.

[0006] According to one embodiment, the first face delimits, with a third face of the volume acoustic wave filter located opposite the first face, a cavity.

[0007] According to one embodiment, the cavity has a thickness defined by a height of said at least one conductive pillar, said at least one conductive pillar forming a projection on the first face.

[0008] According to one embodiment, the cavity is delimited laterally by a peripheral wall.

[0009] According to one embodiment, the peripheral wall is made of an insulating material, preferably a polymer material.

[0010] According to one embodiment, said at least one conductive pillar is located inside the cavity.

[0011] According to one embodiment, the integrated passive device comprises a first semiconductor substrate comprising a region in and on which at least one filter is formed, preferably at least one bandpass filter, more preferably an RLC filter.

[0012] According to one embodiment, the bulk acoustic wave filter comprises a second semiconductor substrate comprising a region in and on which is formed a bulk acoustic wave filter structure connected to the electrode.

[0013] One embodiment provides an electronic device, preferably a mobile phone or smartphone, comprising a radio frequency integrated circuit comprising the electronic filtering circuit as described. Brief description of the drawings

[0014] These characteristics and advantages, as well as others, will be explained in detail in the following description of particular embodiments given without limitation in relation to the attached figures among which:

[0015] [Fig.l] is a schematic and partial sectional view of an example of an electronic filtering circuit according to one embodiment;

[0016] [Fig.2A], [Fig.2B], [Fig.2C], [Fig.2D] and [Fig.2E] are each a schematic and partial sectional view of a structure obtained at the end of a step of a method of manufacturing an integrated passive device according to one embodiment;

[0017] [Fig.3A], [Fig.3B] and [Fig.3C] are each a schematic and partial sectional view of a structure obtained at the end of a step of a method of manufacturing an electronic filtering circuit according to one embodiment; and

[0018] [Fig.4] is a schematic and partial top view of an example of a device integrating an electronic filtering circuit. Description of the embodiments

[0019] The same elements have been designated by the same references in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same references and may have identical structural, dimensional and material properties.

[0020] For the sake of clarity, only the steps and elements useful for understanding the described embodiments have been shown and are detailed. In particular, the applications of the electronic filtering circuits have not been detailed, the described embodiments being compatible with all or most of the applications of the electronic filtering circuits, possibly subject to adaptations within the scope of the person skilled in the art upon reading this description.

[0021] Unless otherwise specified, when referring to two elements connected to each other, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") to each other, this means that these two elements can be connected or be connected by means of one or more other elements.

[0022] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "upper", "lower", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made, unless otherwise specified, to the orientation of the figures.

[0023] Unless otherwise specified, the expressions “about”, “approximately”, “substantially”, and “of the order of” mean to within 10%, preferably to within 5%.

[0024] In the following description, the terms “insulator” and “conductor” mean respectively, unless otherwise specified, electrically insulating and electrically conductive.

[0025] [Fig.l] is a schematic and partial sectional view of an example of an electronic filtering circuit 100 according to one embodiment.

[0026] In the example shown, the electronic filtering circuit 100 comprises an integrated passive device 101 comprising a semiconductor substrate 103, for example a piece of wafer made of a semiconductor material such as silicon. In this example, the semiconductor substrate 103 comprises a region 105 flush with a face 103A of the semiconductor substrate 103 (the lower face of the substrate 103, in the orientation of [Fig. 1]) and in which is formed, for example, at least one bandpass filter, for example an IPD filter (from the English “Integrated Passive Device”). The region 105 comprises, for example, several passive electronic components, for example each chosen from: - a resistive component, for example a resistor; - a capacitive component, for example a capacitor; and - an inductive component, for example an inductor.

[0027] By way of example, region 105 comprises an RLC filter comprising at least one resistive component, at least one capacitive component and at least one inductive component. The structure of region 105 has not been detailed in [Fig.l] so as not to overload the drawing. In particular, the passive electronic components formed in region 105 of the semiconductor substrate 103 have not been shown.

[0028] In the illustrated example, the integrated passive device 101 further comprises an interconnection structure 107 covering the face 103A of the semiconductor substrate 103. The interconnection structure 107 comprises, for example, a stack of layers insulating layers 109 and conductive tracks 111 located in and / or between the insulating layers 109, some of the conductive tracks 111 being in contact with the region 105.

[0029] In the example shown, each conductive track 111 is connected to a contact recovery element 113 located on the face 103A of the semiconductor substrate 103. The conductive tracks 111 make it possible, for example, to connect the contact recovery elements 113 to terminals of the passive electronic components formed in the region 105. The contact recovery elements 113 are, for example, intended to be connected to elements external to the circuit 100. In the example shown, the contact recovery elements 113 are each connected, by a solder ball 115, to a contact recovery element 117 carried by a support substrate 119. By way of example, the support substrate 119 is a printed circuit board.Each contact recovery element 117 is for example a conductive pad or a conductive track.

[0030] In the example shown, the circuit 100 further comprises a bulk acoustic wave (BAW) filter 151, or BAW filter, superimposed on the integrated passive device 101 on the side of a face 103B of the semiconductor substrate 103 opposite its face 103A (on the side of the upper face of the substrate 103, in the orientation of [Fig. 1]). In the example shown, the bulk acoustic wave filter 151 comprises a semiconductor substrate 153, for example a piece of wafer made of a semiconductor material such as silicon, in and on which is formed a bulk acoustic wave filter structure 155 connected to electrodes 157.

[0031] The structure 155 is for example of the FBAR type (from the English “thin-Film Bulk Acoustic Resonator”), also called a “membrane” bulk acoustic wave filter. In this case, the structure 155 comprises for example a membrane made of an insulating material suspended above an air-filled cavity formed in the substrate 153 and at least one piezoelectric layer located on the membrane, for example interposed between the electrodes 157. The structure 155 has not been detailed in [Fig.l] so as not to overload the drawing. As a variant, the structure 155 may be of the SMR type (from the English “Solidly Mounted Resonator”). In this case, the structure 155 comprises, for example, a membrane made of an insulating material located on and in contact with a Bragg mirror and at least one piezoelectric layer located on the membrane, for example interposed between the electrodes 157.

[0032] In the illustrated example, the integrated passive device 101 is separated from the bulk acoustic wave filter 151 by a cavity 171. In this example, the cavity 171 extends vertically from the face 103B of the semiconductor substrate 103 (i.e., from the upper face of the integrated passive device 101, in the orientation of [Fig. 1]) to a face 153A of the semiconductor substrate 153 of the bulk acoustic wave filter volume 151 located opposite the face 103B (i.e. up to the lower face of the volume acoustic wave filter 151, in the orientation of [Fig.l]). In the example shown, the cavity 171 is laterally delimited, or laterally bordered, by a peripheral wall 173. In the example illustrated in [Fig.l], the peripheral wall 173 extends vertically from the face 103B of the substrate 103 to the face 153A of the substrate 153. By way of example, the peripheral wall 173 is made of an insulating material, for example a polymer. The cavity 171 defined by the wall 173 and by the faces 103B and 153A is for example filled with air. As a variant, the interior of the cavity 171 may be subjected to a partial vacuum.

[0033] In the example shown, the circuit 100 further comprises conductive pillars 181 passing through the integrated passive device 101 and each connecting one of the electrodes 157 of the bulk acoustic wave filter 151 to one of the contact recovery elements 113. In the example shown, each conductive pillar 181 projects from the face 103B of the semiconductor substrate 103, passes through the cavity 171 and is located on and in contact with one of the electrodes 157. By way of example, the height of each pillar 181 defines the height, or thickness, of the cavity 171.

[0034] The peripheral wall 173 has, for example, in top view, an annular shape surrounding the conductive pillars 181. This advantageously protects the conductive pillars 181 against external attacks, for example mechanical shocks. This also makes it possible to reduce the lateral dimensions of the electronic filtering circuit, for example compared to a structure in which the electrodes 157 of the BAW filter 151 would be connected to the contact recovery elements 117 of the support substrate 119 by pillars located outside the cavity 171. By way of example, the peripheral wall 173 has, in top view, a periphery of any shape, for example substantially rectangular, oval, square, circular, etc. The cavity 171 is for example hermetic, or sealed. This makes it possible to prevent particles or moisture from penetrating inside the cavity 171.As a variant, the peripheral wall 173 may include openings allowing in particular air exchanges between the interior of the cavity 171 and the external environment. This promotes, for example, a pressure balance between the interior and exterior of the cavity 171, for example in order to take into account heating of the circuit 100 during its operation.

[0035] In the circuit 100, the integrated passive device 101 advantageously acts as a cover, or lid, for the bulk acoustic wave filter 151. This advantageously makes it possible to avoid the use of a dedicated cover not comprising any electronic components. In other words, the use of the integrated passive device 101 as a cover for the bulk acoustic wave filter 151 makes it possible to combine, in the same element, a mechanical protection function, provided in particular by the substrate 103 and the peripheral wall 173, and a filtering function, carried out in particular by the region 105.

[0036] [Fig.l] illustrates an example in which the circuit 100 comprises two conductive pillars 181 each connecting one of the contact recovery elements 113 of the integrated passive device 101 to one of the electrodes 157 of the bulk acoustic wave filter 151. This example is however not limiting, the circuit 100 being able more generally to comprise an integer number, greater than or equal to one, of conductive pillars each connecting a contact recovery element of the integrated passive device 101 to an electrode of the bulk acoustic wave filter 151.

[0037] Filters using an integrated passive device advantageously exhibit, in attenuation bands located on either side of their passband, high rejection performances. However, these filters have the disadvantage of exhibiting, interposed between their passband and each of their attenuation bands, wide transition bands. Conversely, bulk acoustic wave filters have the advantage of exhibiting transition bands that are narrower than those of filters using an integrated passive device, but suffer from inferior rejection performances. Combining, in the circuit 100, the integrated passive device 101 and the bulk acoustic wave filter 151 makes it possible to combine the advantages and eliminate, or reduce, the disadvantages of these two types of filters.The circuit 100 thus has, for example, a narrower transition band than that of the integrated passive device 101 taken in isolation, and rejection performances superior to those of the bulk acoustic wave filter 151 taken in isolation.

[0038] Furthermore, because the integrated passive device 101 and the bulk acoustic wave filter 151 of the circuit 100 are superimposed, this advantageously results in a saving of space. This also makes it possible to provide shorter connections, and therefore lower resistance, between the integrated passive device 101 and the bulk acoustic wave filter 151.

[0039] [Fig.2A], [Fig.2B], [Fig.2C], [Fig.2D] and [Fig.2E] are each a schematic and partial sectional view of a structure obtained at the end of a step of a manufacturing method of the integrated passive device 101 according to one embodiment.

[0040] [Fig.2A] represents the structure obtained after the formation of the region 105 and the formation of the interconnection structure 107 on the face 103A of the substrate 103. One or more electronic components, not shown, are formed in and / or on the region 105. According to one embodiment, at this stage of the method, the substrate 103 corresponds to a wafer, and the regions 105 of several integrated passive devices are formed in and / or on the substrate 103, the regions 105 possibly being identical or different. In [Fig.2A], a single region 105 is represented and the interconnection structure 107 comprises the conductive tracks 111 connected to the region 105 and the insulating layer 109 covering the conductive tracks 111 and the face 103A of the substrate 103 around the conductive tracks 111. At this stage of the process, the thickness of the substrate 103 is strictly greater than the desired final thickness of the substrate 103. The thickness of the substrate 103, at this stage of the process, is for example between 500 pm and 1.3 mm.

[0041] [Fig.2B] shows the structure obtained after forming an opening 201 at the desired location of each connection pillar 181 and forming an opening 203 at the desired location of insulating walls 205. The openings 201 and 203 pass completely through the interconnection structure 107 and extend over a portion of the thickness of the substrate 103 from the face 103A. The openings 201 have the same depth and the openings 203 have the same depth. The depth of the openings 201 is greater than the depth of the openings 203.The depth of the openings 203 is for example substantially equal to the desired final thickness of the substrate 103. The depth of the openings 203 is for example between 50 and 300 μm. The openings 201 and 203 are for example produced by deep reactive ion etching (DRIE) steps. Depending on the method used for forming the openings 201 and 203, the openings 201 and the openings 203 can be produced simultaneously or can be produced in separate steps. In particular, with deep reactive ion etching, the etching speed depends on the diameter of the opening so that the openings 203, which for example have a width smaller than the average diameter of the openings 201, can be produced simultaneously with the openings 201.

[0042] Each opening 201 may have a cross-section of any shape. For example, each opening 201 has, in top view, a substantially circular shape, a rectangular shape with rounded corners, an oval shape, etc. The openings 201 have, for example, a depth depending on the desired height of the pillars 181.

[0043] [Fig.2B] further shows the structure obtained after the formation of an insulating layer 207 in each opening 201 and the formation of the insulating wall 205 in each opening 203. At this stage of the method, the insulating layer 207 coats the side walls and the bottom of the opening 201. This step may comprise the deposition of an insulating layer simultaneously on the walls of the opening 203 and on the walls of the opening 201, the thickness of the insulating layer being such that it fills, i.e. completely fills, the opening 203 but does not fill each opening 201 so that a cavity 209 is present in each opening 201 after the formation of the insulating layer.

[0044] [Fig.2C] represents the structure obtained after the formation, for each connection pillar to be produced, of an opening 211 in the insulating layer 109 to expose one of the conductive tracks 111, the deposition of a mask (not shown) on the insulating layer 207 comprising, for each connection pillar to be produced, an opening exposing the cavity 209, the opening 211 and the part of the insulating layer 109 connecting the cavity 209 to the opening 211, and the formation of an interface layer 215 in each opening. At this stage of the method, the interface layer 215 covers all the walls of the cavity 209, in particular the side walls and the bottom of the cavity 209, the walls of the opening 211, and the exposed part of the insulating layer 109 connecting the cavity 209 to the corresponding opening 211. The mask may correspond to a film which is applied to the insulating layer 109.

[0045] [Fig.2C] further represents the structure obtained after, for each connection pillar to be produced, a complete filling of each cavity 209 with a conductive material, thus forming a trunk of the connection pillar 181, and the formation of a connection portion 217 of each connection pillar. The connection portion 217 corresponds for example to one of the contact recovery elements 113 of the circuit 100. The conductive material composing the trunk can be deposited by electrodeposition on the interface layer 215. In this case, the deposition of the conductive material is carried out from the interface layer 215 in a direction substantially perpendicular to the interface layer 215.This advantageously makes it possible to fill the cavity 209 even if the form factor of the cavity 209, i.e. the ratio between the height of the cavity and the diameter of the cavity, is high, since the deposition of the conductive material is carried out in particular from the side walls of the cavity 209.

[0046] [Fig.2C] further represents the structure obtained after the removal of the film and the formation, for each connection pillar 181, of an insulating layer 219 covering the connection portion 217.

[0047] [Fig.2D] represents the structure obtained after etching the substrate 103 from its face 103B. At the end of the etching step, for each connection pillar 181, a part of the trunk, surrounded by the interface layer 215 and the insulating layer 207, projects from the substrate 103 from the face 103B over a height H. The height H corresponds for example substantially to the thickness of the future cavity 171. The etching step may comprise a selective chemical etching with respect to the material composing the insulating layer 207. The etching of the substrate 103 is for example stopped when the end of the wall is flush with the lower face 103B. The height H is fixed by the etching step.

[0048] [Fig.2D] further represents the structure obtained after the formation of an insulating layer 221 on the face 103B of the substrate 103. The insulating layer 221 is for example made of the same material as the insulating layer 207 and the thickness of the insulating layer 221 is for example, at this stage of the method, substantially equal to the sum of the thickness of the insulating layer 207 and the desired final thickness of the layer insulating layer 221, for example equal to twice the thickness of the insulating layer 207.

[0049] [Fig.2E] represents the structure obtained after the complete etching of the portion of the insulating layer 207 which is exposed on the side of the face 103B of the substrate 103. This step can further result in the etching of the insulating layer 221 over the thickness of the insulating layer 207. The insulating layer 221 having the desired final thickness is then obtained.

[0050] [Fig.2E] further represents the structure obtained after, for each connection pillar 181, the etching of the interface layer 215 covering the end face, the formation of a finishing layer 223 and the formation of a block of connecting material 225.

[0051] [Fig.2E] further represents the structure obtained after a cutting step to separate the integrated passive devices 101. For example, the cutting lines are located between the walls 205 of adjacent devices 101.

[0052] Each integrated passive device 101 thus individualized can then be fixed to an external element, for example the support substrate 119. The wall 205 protects the region 105 of the integrated passive device 101 in particular against electrostatic discharges at the level of the side walls of the device 101 during handling and fixing of the device 101 to the external element.

[0053] [Fig.3A], [Fig.3B] and [Fig.3C] are each a schematic and partial sectional view of a structure obtained at the end of a step of a method of manufacturing an electronic filtering circuit, for example the circuit 100 of [Fig.1], according to one embodiment. The steps described below in relation to FIGS. 3A to 3C can be implemented indifferently before, during or after the steps of manufacturing the integrated passive device 101 previously described in relation to FIGS. 2A to 2E.

[0054] [Fig.3A] represents the structure obtained after the formation of the structure 155 in and on the semiconductor substrate 153, and after the formation of the electrodes 157.

[0055] [Fig.3A] further represents the structure obtained after the formation of the peripheral wall 173 on the face 153A of the semiconductor substrate 153. At the end of this step, the peripheral wall 173 has, for example, a height substantially equal to the height H of the pillars 181.

[0056] [Fig. 3B] represents the structure obtained after transferring the integrated passive device 101 of [Fig. 2E] onto the bulk acoustic wave filter 151 of [Fig. 3A]. For example, the integrated passive device 101 is turned over with respect to the orientation of [Fig. 2E], so that the face 103B of the semiconductor substrate 103 is located opposite the face 153A of the bulk acoustic wave filter 151. The blocks of connecting material 225 of the integrated passive device 101 are for example then brought into contact with the electrodes 157 of the bulk acoustic wave filter 151, the wall peripheral 173 coming to bear on the face 103B of the semiconductor substrate 103. The electronic filtering circuit 100 is for example thus obtained.

[0057] [Fig.3C] represents the structure obtained after fixing the electronic filtering circuit 100 on the support substrate 119. By way of example, the insulating layer 219 is previously opened in line with the contact recovery elements 113 in order to free their face opposite the pillars 181. The circuit 100 is for example then transferred onto the support substrate 119 so that the face 103A of the semiconductor substrate 103 is located opposite the contact recovery elements 117 of the support substrate 119.

[0058] [Fig.4] is a schematic and partial top view of an example of a device 400 integrating an electronic filtering circuit, for example the circuit 100. In the example shown, the device 400 is a mobile telephone, or smartphone.

[0059] In this example, the device 400 comprises a processing circuit 401 (AP), for example a microcontroller or a main microprocessor of the device 400. The processing circuit 401 is for example connected to a radiofrequency integrated circuit 403 (RFIC) comprising the electronic filtering circuit 100. In the illustrated example, the radiofrequency integrated circuit 403 is connected to an antenna 405 (ANT), for example a radiofrequency communication antenna of the device 400. Although this has not been detailed in [Fig. 4] in order not to overload the drawing, the radiofrequency integrated circuit 403 may further comprise components and circuits intended to implement impedance matching, amplification, modulation / demodulation, switching functions, etc.

[0060] The device 400 may further comprise other elements, for example other electronic components or circuits not detailed in [Fig.4]. These elements have been symbolized, in [Fig.4], by a functional block 407 (FCT).

[0061] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will occur to those skilled in the art. In particular, those skilled in the art are able, from the indications of the present description, to provide and fabricate a circuit similar to circuit 100 but comprising several integrated passive devices 101 stacked on top of each other.

[0062] Furthermore, although [Fig. 4] takes as an example the case of an integration of the circuit 100 into a mobile telephone or a smartphone, the embodiments described are not limited to this example but apply more generally to any device or system equipped with wireless communication functions, for example in the field of telematics. In particular, the circuit 100 can be integrated into motor vehicles, for example to implement functionalities of wireless Internet access, communication of the vehicle with external equipment or systems, autonomous driving, etc.

[0063] Finally, the practical implementation of the described embodiments and variants is within the reach of those skilled in the art from the functional indications given above. In particular, the described embodiments are not limited to the particular examples of materials and dimensions mentioned in the present description.

Claims

Claims

1. Electronic filtering circuit (100) comprising: - an integrated passive device (101); - a bulk acoustic wave filter (151) superimposed on the integrated passive device (101) on the side of a first face (103B) of the integrated passive device (101); and - at least one conductive pillar (181) passing through the integrated passive device (101) and connecting an electrode (157) of the bulk acoustic wave filter (151) to a contact recovery element (113) located on a second face (103A) of the integrated passive device (101) opposite the first face (103B) and intended to be connected to an external element (117).

2. The circuit (100) of claim 1, wherein the integrated passive device forms a cover of the bulk acoustic wave filter.

3. Circuit (100) according to claim 1 or 2, in which the first face (103B) delimits, with a third face (153A) of the volume acoustic wave filter (151) located opposite the first face (103B), a cavity (171).

4. Circuit (100) according to claim 3, wherein the cavity (171) has a thickness defined by a height (H) of said at least one conductive pillar (181), said at least one conductive pillar (181) protruding from the first face (103B).

5. Circuit (100) according to claim 3 or 4, in which the cavity (171) is delimited laterally by a peripheral wall (173).

6. Circuit (100) according to claim 5, wherein the peripheral wall (173) is made of an insulating material, preferably a polymeric material.

7. A circuit (100) according to any one of claims 3 to 6, wherein said at least one conductive pillar (181) is located inside the cavity (171).

8. Circuit (100) according to any one of claims 1 to 7, wherein the integrated passive device (101) comprises a first semiconductor substrate (103) comprising a region (105) in and on which is formed at least one filter, preferably at least one bandpass filter, more preferably an RLC filter.

9. A circuit (100) according to any one of claims 1 to 8, wherein the bulk acoustic wave filter (151) comprises a second semiconductor substrate (153) comprising a region (155) in and on which is formed a bulk acoustic wave filter structure connected to the electrode (157).

10. Electronic device (400), preferably mobile phone or smartphone, comprising a radiofrequency integrated circuit (403) comprising the electronic filtering circuit (100) according to any one of claims 1 to 9.

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