Inductive component and manufacturing process

Abstract

A device comprising at least one integrated inductive component (1) having at least one metallic winding (2) at least partially embedded in a coating (3) comprising at least one ferromagnetic material and optionally one non-magnetic material, for example a dielectric. Figure for the abbreviation: Fig 1

Description

Title of the invention: Inductive component and manufacturing method

[0001] Implementation and embodiment modes relate to microelectronics, in particular inductive components and for example those used to produce transformers.

[0002] Currently there are discrete components incorporating metal coils forming inductances. However, in addition to the fact that such inductances may have unsatisfactory performance for certain applications, such discrete components have sizes that make them impossible to integrate at the substrate level of integrated circuit packages (between the chip and a printed circuit board) and make them very bulky at the level of the printed circuit board.

[0003] There are also inductors formed from spiral metal tracks, etched and formed within a stack of dielectric and metal layers of a substrate of an integrated circuit package. The value of the inductance is provided by the length of the metal track and the number of windings, but such an inductor has poor electromagnetic performance induced by the non-magnetic characteristic of the dielectric materials used and the low number of windings that can be produced.

[0004] There is therefore currently a need to have, for certain applications in microelectronics, inductive components, or inductances, which are compact and can have high inductive values ​​with improved performance such as an improved quality factor ("Q factor") and reduced losses such as, for example, a reduction in parasitic resistance and magnetic flux losses.

[0005] According to one aspect, a device is thus proposed comprising at least one integrated inductive component comprising at least one metal winding at least partially embedded in a coating comprising at least one ferromagnetic material and possibly also a non-magnetic material, for example a dielectric material.

[0006] An integrated inductive component, unlike a discrete component, is easily integrated into an integrated circuit package for example, and has a competitive manufacturing cost.

[0007] The presence of the ferromagnetic material contributes to increasing the electromagnetic performance of the inductive component and to increasing component integration.

[0008] For example, the use of a metal winding at least partially embedded in a ferromagnetic material allows a reduction in parasitic resistance and magnetic flux losses.

[0009] It is also possible to obtain with such an integrated, particularly compact component, high inductive values ​​with a high quality factor.

[0010] The ferromagnetic material is chosen according to the characteristics desired for the inductance taking into account the intended application.

[0011] For example, the ferromagnetic material may be a hardened resin.

[0012] This cured resin may comprise a dielectric material such as a polymer, for example nylon 6, nylon 12, or a polyamide, including a magnetic material for example a strontium ferrite (Sr), a neodymium-iron-boron alloy (NdFeB), a CoZrO alloy which has high frequency performance suitable for radio frequency applications, a cobalt-nickel-iron alloy (CoNiFe), or even amorphous iron-cobalt alloys, or any combination of at least some of the elements mentioned above.

[0013] A person skilled in the art will know how to choose the composition of the ferromagnetic material according to the desired properties for the inductive component taking into account the intended application.

[0014] The metal winding may comprise at least one flat metal track of a shape suitable for producing an inductive element, for example in the form of a spiral or a solenoidal shape.

[0015] The metal winding may also comprise several flat metal tracks respectively located in parallel planes, electrically connected and mutually separated at least for some of them by the ferromagnetic material.

[0016] Some tracks may be mutually separated by the non-magnetic material.

[0017] This electrical connection between the tracks of the different planes can be made by means of vias, hollow or solid, of any section, for example circular, square, rectangular, etc.

[0018] The metal winding can be completely embedded in said coating.

[0019] According to one embodiment, the metal winding has two ends, and the coating has several faces, and the device then has two metal contacts respectively located at the two ends and opening onto at least one of the faces of the coating.

[0020] These two metal contacts can thus allow, for example, an electrical connection of the inductive component with other components and / or a connection of the inductive component to a conventional support substrate of an integrated circuit package, for example a multilayer support substrate of the PCB type.

[0021] This being said, according to a particularly advantageous variant, the coating can itself form a support substrate.

[0022] If the coating only comprises a ferromagnetic material, then a magnetic support substrate is obtained.

[0023] If the coating comprises a ferromagnetic material and a non-magnetic material, a hybrid magnetic-non-magnetic substrate-support, for example magneto-dielectric, is obtained.

[0024] This can be advantageous when it is desired to produce a device forming a high-performance transformer comprising a first inductive element (the primary) embedded in a ferromagnetic material and a second inductive element (the secondary) embedded in a ferromagnetic material, the two elements being separated by a dielectric resin making it possible to create galvanic isolation.

[0025] A hybrid support substrate, comprising certain turns insulated by a non-magnetic material, for example dielectric, instead of being separated by the magnetic material, allows the choice of coupling or decoupling certain turns within the support substrate.

[0026] The support substrate has two opposite faces, for example a mounting face, the other face, for example the lower face, comprising electrically conductive connection means.

[0027] An encapsulating means may be attached to the mounting face to form an integrated circuit package.

[0028] In this particularly advantageous variant, two functions are then achieved with the same means, namely the ferromagnetic coating.

[0029] A first function is to contribute to the production of the inductive component and to contribute to obtaining good electromagnetic performance, even with small metal windings.

[0030] A second function is to form a support substrate and in this respect as indicated previously, the coating then has a mounting face and a lower face comprising electrically conductive connection means, for example solder balls, allowing for example its connection to a printed circuit board (PCB: “Printed Circuit Board”).

[0031] The device may then further comprise, as indicated previously, an encapsulation means, a cover or a molding resin, fixed to the mounting face of the support substrate (the coating), so as to form an integrated circuit package.

[0032] If a molding resin is used to form the encapsulating means, it may be different from the ferromagnetic resin or it may also be the same ferromagnetic resin.

[0033] According to this variant in which the coating forms the support substrate, the coating may further comprise at least one integrated circuit located within the coating in a zone distinct from that containing the metal winding.

[0034] The mounting face of the coating forming the support substrate can support also at least one electronic chip encapsulated by the encapsulation means.

[0035] According to another possible variant, the device may comprise a support substrate having a mounting face supporting said at least one integrated inductive component.

[0036] This support substrate may be, for example, a multilayer support substrate of an integrated circuit package.

[0037] Also in this variant, the device may comprise at least one electronic chip, said at least one integrated inductive component supporting said at least one electronic chip.

[0038] It is also possible for the support substrate to also support at least one electronic chip located on the mounting face of the support substrate laterally relative to said at least one inductive component.

[0039] Also according to this variant, the device may comprise at least one integrated circuit located within the coating in a zone distinct from that containing the metal winding.

[0040] Here again, the device may further comprise an encapsulation means, for example a cover or a molding resin, fixed on the mounting face of the support substrate and encapsulating said at least one inductive component and said at least one possible chip, so as to form an integrated circuit package.

[0041] According to another aspect, there is provided a method of manufacturing an integrated inductive component, comprising a. A formation of at least one metallic winding at least partially embedded in a coating comprising at least one ferromagnetic material and possibly also a non-magnetic material, for example dielectric.

[0042] As indicated above, such a ferromagnetic material may be, for example, a thermoset magnetic resin.

[0043] This thermoset resin can result, for example, from polymerization at room temperature of a resin initially in liquid or viscous form.

[0044] This initial resin can be deposited for example from a liquid, a thin film, a powder of a dielectric material such as that mentioned above, mixed with a magnetic material such as that mentioned above in liquid form, a thin film, a powder, granular films, ... and all combinations of at least some of the preceding elements.

[0045] According to one embodiment, the metal winding comprises at least one first flat metal track in the form of a spiral, and step a) comprises -al) a formation above a first face of a support of a first layer of the ferromagnetic material having a free face and -a2) a formation of said at least one first spiral-shaped metal track on said free face.

[0046] According to one embodiment, the metal winding comprises a formation of a second layer of ferromagnetic material encapsulating said at least one first flat metal track.

[0047] According to one embodiment, the metal winding comprises a formation of a first pad and a second electrically conductive pad above the first face of the support, respectively intended to be in contact with a first end and a second end of the metal winding.

[0048] According to one embodiment, the first pad is in contact with a first end of the first metal track and the second pad is not in contact with this first metal track, and step a) comprises after step a2) and before step a3), -a20) a formation of a first via and a second electrically conductive via respectively connecting a second free end of the first metal track and the second pad, and after step a3), -a4) a formation of a second spiral metal track on the second layer of ferromagnetic material, the two ends of this second metal track contacting the two vias respectively.

[0049] According to one embodiment, the method further comprises forming a third layer of ferromagnetic material encapsulating said second flat metal track.

[0050] At this stage, three levels of metallization have been produced in the coating, two of which have two metal tracks in spirals of the metal winding.

[0051] Of course, it would have been possible to make only one spiral metal track. It is also possible to repeat some of the previous steps to make other spiral metal tracks of the metal winding.

[0052] It is also possible for the method to comprise at least one replacement of a layer of ferromagnetic material by a layer of a non-magnetic material so as to obtain at least one non-magnetic layer adjacent to a ferromagnetic layer.

[0053] This allows galvanic isolation to be created between turns.

[0054] When forming the turns on each of the levels, it is also possible to form additional tracks serving only for the interconnection of a chip integrated in the device with the lower face provided with solder balls for example, or else serving only for the interconnection of several chips integrated in the device.

[0055] According to an implemented variant, the method further comprises a removal of the support after step a).

[0056] According to another possible implementation variant, the support is a multilayer support substrate which is preserved at the end of step a).

[0057] Other advantages and characteristics of the invention will appear on examining the detailed description of embodiments and implementations, which are in no way limiting, and the appended drawings in which:

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[0088] [Fig.l] [Fig.2] [Fig.3] [Fig.4] [Fig.5] [Fig.6] [Fig.7] [Fig.8] [Fig.9] [Fig.10] [Fig.11] [Fig.12] [Fig.13] [Fig.14] [Fig.15] [Fig.16] [Fig.17] [Fig.18] [Fig.19] [Fig.20] [Fig.21] [Fig.22] [Fig.23] [Fig.24] [Fig.25] [Fig.26] [Fig.27] [Fig.28] [Fig.29] [Fig.30] [Fig.31] schematically illustrate embodiments and embodiments of the invention.

[0089] In [Fig.l], the DIS reference designates a device comprising here a component. integrated inductive 1.

[0090] This component 1 comprises a metal winding 2 here completely embedded in a ferromagnetic coating 3 which comprises a lower face FI and an upper face FM.

[0091] In this example, the ferromagnetic material forming the coating 3 is a hardened resin.

[0092] This cured resin may comprise a dielectric material such as a polymer, for example nylon 6, nylon 12, or a polyamide including a magnetic material for example a strontium ferrite (Sr), a neodymium-iron-boron alloy (NdFeB), a CoZrO alloy which has high frequency performance suitable for radio frequency applications, a cobalt-nickel-iron alloy (CoNiFe), or even amorphous iron-cobalt alloys, and any combination of at least some of the elements mentioned above.

[0093] A person skilled in the art will know how to choose the composition of the ferromagnetic material according to the desired properties for the inductive component taking into account the intended application.

[0094] By way of non-limiting example, such a resin may be the AFT INNOVA resin from the Japanese company AJINOMOTO, which has good electromagnetic performance at 100 MHz and which may, for example, be used in switching power supplies operating up to this frequency.

[0095] In the embodiment of [Fig.l], the metal winding 2 comprises a first spiral metal track 20 and a second spiral metal track 21, also located in two parallel planes, here at the second and third metal levels.

[0096] By way of non-limiting example, the two tracks 20 and 21 may be separated by a thickness of resin of between the order of ten micrometers and several hundred micrometers, for example of the order of 20 to 160 micrometers.

[0097] The first metal track 20 comprises a first end 201 and a second end 202.

[0098] The second metal track 21 comprises a first end 211 and a second end 212.

[0099] The first end 201 forms the first end of the metal winding while the second end 212 forms the second end of the metal winding.

[0100] The component 1 further comprises a first contact or pillar 41 in contact with the first end 201 and also opening onto the lower face FI of the coating 3.

[0101] The component 1 also comprises a first metal via 51 connecting the second end 202 and first end 211.

[0102] The component 1 also comprises a second via 52 connecting the second end 212 to a second contact or pillar 42 also opening onto the lower face FI of the coating 3.

[0103] The free surfaces of the contacts or pillars 41 and 42 make it possible, for example, to connect the inductive component 1 to another circuit or to solder this component onto a conventional carrier substrate, for example multilayer, of an integrated circuit package.

[0104] The metal used for the metal winding as well as the pillars and vias can be, for example, copper.

[0105] The shape of the spiral of each metal track can be any.

[0106] It may for example be circular in shape as illustrated schematically in [Fig.2] for track 20 or rectangular in shape as illustrated schematically in [Fig.3].

[0107] For example, the length of each track can be of the order of a hundred millimeters with a number of turns of the order of ten for an inductive element surface area of ​​4x4 mm2.

[0108] Using an AFT INNOVA resin, it is possible to obtain, for a track length of 47 mm and 3 turns, an inductive value of the order of 95 nH at 100 MHz, whereas only an inductive value of 50 nH would be obtained using a conventional non-ferromagnetic casting resin.

[0109] As illustrated schematically in Figures 4 to 6, the coating 3 can itself form a support substrate having a mounting face FM which is here the upper face and a lower face FI which comprises electrically conductive connection means 300, for example but not limited to solder balls, allowing for example the support substrate to be fixed on a printed circuit board.

[0110] The DIS device may also comprise an encapsulation means 7, for example here a cover, fixed on the mounting face so as to form an integrated circuit package.

[0111] This encapsulation means could also be a molding resin.

[0112] As illustrated in [Fig.4], the DIS device may also comprise at least one electronic chip 6 supported by the integrated inductive component 1.

[0113] The encapsulation means 7 may then optionally be a molding resin encapsulating the chip 6.

[0114] It is also possible, as illustrated in [Fig.5], that the coating 3 (substrate-support) supports an electronic chip 6 located above a zone Z2 distinct from the zone ZI in which the metal winding of the component is located. inductive 1 while in [Fig.4], chip 6 was located above inductive component 1.

[0115] It is also possible, as illustrated in [Fig.6], that the device DIS comprises within the coating 3 and in the zone Z2 distinct from the zone Z1, at least one integrated circuit 8.

[0116] While in Figures 4 to 6, the coating 3 formed a support substrate, the DIS device may comprise, as schematically illustrated in Figures 7 and 8, a support substrate 9 separate from the inductive component 1.

[0117] This support substrate 9 may be a conventional multi-layer substrate equipped on its lower face with electrically conductive connection means 90, again for example, but not limited to, solder balls, to allow the fixing of this support substrate 9 on a printed circuit board for example.

[0118] Opposite this lower face, the support substrate comprises an FMI mounting face supporting the inductive component 1.

[0119] Here again, as illustrated in [Fig.7], the DIS device may comprise an electronic chip 6 supported by the inductive component 1 and located above the metal winding of this inductive component.

[0120] An encapsulation means 7, for example a cover or a molding resin, can complete the DIS device so that it forms an integrated circuit package.

[0121] It is also possible, as illustrated in [Fig. 8], that the coating 3 comprises an integrated circuit 8 located in a zone Z2 distinct from the zone Z1 in which the metal winding of the inductive component 1 is located.

[0122] The DIS device may also comprise at least one electronic chip 6 located laterally relative to the inductive component 1 and supported by the mounting face of the support substrate 9.

[0123] Reference is now made more particularly to Figures 9 to 20 to describe an embodiment of a method for manufacturing an integrated inductive component.

[0124] As illustrated in [Fig.9], in an STI step, a seed layer 100 and 101, for example a very thin copper film, is formed on each of the faces 100 and 101 of a metal support 10, for example made of stainless steel.

[0125] Then, a first metallization level is formed on the layer 100 in a step ST2 ([Fig. 10]), comprising in particular contact pads L1, L2. This first metallization level may also comprise metal tracks and possibly a first spiral metal track of the metal winding of the future inductive component.

[0126] That being said, in the example illustrated here, the first metal level does not include a spiral metal track of the metal winding of the future inductive component.

[0127] The contact pads L2 and L1 as well as any other metal tracks of the first level of metallization are for example formed by an electrolytic or (possibly autocatalytic) deposition of copper (“plating”).

[0128] Then, as illustrated in [Fig.l 1], the first pad or pillar 41 and the second pad or pillar 42 are formed in a step ST3, also by electrolytic deposition of copper.

[0129] Then, in step ST4 ([Fig. 12]), after having prepared the resin in the form of a viscous material, with the elements indicated above and chosen according to the ferromagnetic properties desired for the envisaged application, a preliminary layer 30 of resin is deposited so as to embed the pillars 41 and 42.

[0130] This formation of the layer 30 is carried out for example by injecting the viscous resin at 175°C, with a transfer pressure of 8MPa and a pressure on the substrate of 350 kN, then polymerization is carried out, for example by cooling to room temperature or possibly with ultraviolet radiation, of this viscous layer so as to solidify the resin.

[0131] In step ST5 ([Fig. 13]), the preliminary layer 30 is then thinned, for example by chemical-mechanical polishing, so as to obtain a first layer 31 of hardened ferromagnetic resin exposing the upper faces of the pads 41 and 42.

[0132] The second metallization level is then formed in step ST6, also for example by forming a metal bonding layer followed by electrolytic deposition (growth) of copper, here comprising the first metal track 20 in the form of a spiral of the metal winding of the future inductive component.

[0133] This first metal track 31 comes into contact with the exposed upper face of the first pad 41.

[0134] Then, in step ST7 of [Fig. 15], the two vias 51 and 52 are formed, also by electrolytic deposition of copper, respectively contacting the second end of the first metal track 20 and the exposed upper face of the second pad 42.

[0135] Then, in step ST8 of [Fig. 16], the structure obtained in step ST7 is covered with a new layer 32 of ferromagnetic resin.

[0136] The formation of this layer 32 is carried out under the same conditions as those for the formation of the layer 30 of [Fig. 12].

[0137] In step ST9 of [Fig. 17], this layer 32 is then thinned, for example by chemical-mechanical polishing, so as to obtain a second layer 33 of ferromagnetic resin leaving the upper faces of the vias 51 and 52 free.

[0138] Then, in step ST10 of [Fig. 18], we form, also by electrolytic deposition of copper, a second spiral metal track 21 of the metal winding of the inductive component having one end connected to the free upper face of the via 51 and another end connected to the free upper face of the via 52.

[0139] Then, in step STI 1 of [Fig. 19], the structure obtained in step ST 10 with a third layer of ferromagnetic resin. The formation of this third layer 34 is analogous to the formation of the previous resin layers.

[0140] Finally, in step ST12 of [Fig.20], the metal support is removed. 10 so as to obtain component 1 illustrated in [Fig.l].

[0141] Reference is now made more particularly to Figures 21 to 31 to illustrate another mode of implementation of a method of manufacturing a device according to the invention.

[0142] In this embodiment, the metal support 10 of [Fig.9] is replaced in [Fig.21] by a support substrate 9, for example a conventional multilayer support substrate of an integrated circuit package.

[0143] Then, in step ST20, the pattern of a first metallization level is defined using an SM mask.

[0144] This mask makes it possible to define an orifice OR in which we will, in step ST21 of [Fig.22], define in particular the contact pads L1 and L2 similar to the contact pads L1 and L2 of [Fig.10].

[0145] Steps ST22 to ST30 are analogous to steps ST3 to ST1 1 described previously.

[0146] At the end of step ST30, component 1 of [Fig.7] is obtained, supported by the support substrate 9.

[0147] Unlike the implementation mode illustrated in FIGS. 9 to 20, the support substrate 9 is not removed after step ST30.

[0148] Of course, if one wishes to produce an inductance having more than two spiral metal tracks, one can repeat steps ST7 to ST1 1 or ST 26 to ST30 as many times as necessary.

[0149] The invention is not limited to the modes of implementation and embodiment which have just been described.

[0150] Thus, once produced at the end of step ST12, component 1 of [Fig.20] could be soldered onto a printed circuit board so as to obtain the structure illustrated in [Fig.31].

[0151] It is also possible to replace certain ferromagnetic layers with non-magnetic layers, for example dielectric ones.

[0152] Thus, for example, in figures 16, 17 and 28, 29, the layers 32 and 33 could be dielectric layers, which makes it possible to have within the coating 3 of the component 1 of [Fig. 1] (or of [Fig. 7]) a dielectric layer between the turns 20 and 21 and so to decouple them.

Claims

Claims

1. Device comprising at least one integrated inductive component (1) comprising at least one metal winding (2) at least partially embedded in a coating (3) comprising at least one ferromagnetic material.

2. A device according to claim 1, wherein the coating further comprises a non-magnetic material.

3. Device according to claim 1 or 2, in which the metal winding comprises at least one flat metal track (20) having a shape suitable for producing an inductance.

4. Device according to claim 3, in which the metal winding comprises several flat metal tracks (20, 21) respectively located in parallel planes, electrically connected and mutually separated for at least some of them by the ferromagnetic material.

5. A device according to claims 2 and 4, wherein some tracks are mutually separated by the non-magnetic material.

6. Device according to one of the preceding claims, in which the metal winding (2) is completely embedded in said coating (3).

7. Device according to one of the preceding claims, in which the metal winding comprises two ends (201, 212), the coating comprises several faces (FI, FM) and the device comprises two metal contacts respectively connected to the two ends and opening onto at least one (FI) of the faces.

8. Device according to one of claims 1 to 7, in which said coating (3) forms a support substrate having two opposite faces (FM, FI).

9. Device according to claim 8, in which one of the faces is a mounting face (FM) and the other face (FI) comprises electrically conductive connection means.

10. A device according to claim 9, further comprising encapsulating means (7) secured to the mounting face so as to form an integrated circuit package.

11. Device according to one of claims 8 to 10, in which the coating (3) further comprises at least one integrated circuit (8) located within the coating in a zone (Z2) distinct from that (Z1) containing the metal winding.

12. Device according to one of claims 8 to 11 taken in combination with claims 10 and 11, in which the mounting face of the coating also supports at least one electronic chip (6) encapsulated by the encapsulation means.

13. Device according to one of claims 1 to 7, comprising a support substrate (9) having a mounting face (FMI) supporting said at least one integrated inductive component (1).

14. Device according to claim 13, comprising at least one electronic chip (6), said at least one integrated inductive component (1) supporting said at least one electronic chip (6).

15. Device according to claim 13 or 14, wherein the support substrate (9) also supports at least one electronic chip (6) located on the mounting face (FMI) laterally relative to said at least one inductive component (1).

16. Device according to one of claims 13 to 15, further comprising at least one integrated circuit (8) located within the coating (3) in a zone (Z2) distinct from that (Zl) containing the metal winding.

17. Device according to one of claims 13 to 16, further comprising an encapsulation means (7) fixed on the mounting face (FMI) and encapsulating said at least one inductive component and said at least one possible chip, so as to form an integrated circuit package.

18. Method for manufacturing an integrated inductive component, comprising -a) forming at least one metal winding (2) at least partially embedded in a coating (3) comprising at least one ferromagnetic material.

19. Method according to claim 18, wherein the metal winding comprises at least one first spiral-shaped planar metal track (20), and step a) comprises -a1) a formation (ST4, ST5) above a first face of a support of a first layer of the ferromagnetic material (31) having a free face and -a2) a formation (ST6) of said at least one first spiral-shaped metal track on said free face.

20. Method according to claim 19, further comprising after step a2): -a3) a formation (ST8, ST9) of a second layer (33) of the ferromagnetic material encapsulating said at least one first me- track flat metal.

21. Method according to claim 19 or 20, in which step a) comprises, prior to step a1), -aO) a formation (ST3) of a first pad (41) and a second pad (42) electrically conductive above the first face of the support, respectively intended to be in contact with a first end and a second end of the metal winding.

22. Method according to claims 20 and 21, in which the first pad is in contact with a first end of the first metal track and the second pad is not in contact with this first metal track, and step a) comprises after step a2) and before step a3), a20) a formation (ST7) of a first via and a second electrically conductive via respectively connecting a second free end of the first metal track and the second pad, and after step a3), -a4) a formation (ST8, ST9) of a second spiral metal track (33) on the second layer of ferromagnetic material, the two ends of this second metal track respectively contacting the two vias.

23. Method according to claim 22, further comprising after step a4): -a5) a formation (STI 1) of a third layer of the ferromagnetic material (34) encapsulating said second flat metal track.

24. Method according to one of claims 18 to 23, comprising at least one replacement of a layer of ferromagnetic material by a layer of a non-magnetic material so as to obtain at least one non-magnetic layer adjacent to a ferromagnetic layer.

25. Method according to one of claims 18 to 24 taken in combination with claim 19, further comprising a removal (ST 12) of the support (10) after step a).

26. Method according to one of claims 18 to 24 taken in combination with claim 19, in which the support (10) is a multilayer support substrate which is preserved at the end of step a).

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