Optical Package of Integrated Circuit

Abstract

An optical package for an integrated circuit is disclosed. An electronic chip supports an optical device and an electrical connection region. An insulating coating is applied to the electronic chip, covering the electrical connection region and exposing the optical device. An optical plugging element is at least partially fixed on a first surface of the insulating coating and is optically coupled to the optical device. A through-hole passes through the insulating coating from its first surface to a second surface opposite the first surface. The inner wall of the through-hole supports a conductive path, and the conductive path is connected to the electrical connection region of the electronic chip through a conductive track provided on the first surface of the insulating coating. The conductive path of the through-hole also has an end portion protruding to the second surface of the insulating coating.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims the priority of French Patent Application No. 2013045 filed on December 11, 2020, and incorporates the content of this application in its entirety by reference to the maximum extent permitted by law. Technical Field

[0003] Embodiments and implementations relate to the field of microelectronics, and in particular, to the field of packaging integrated circuits, and more specifically, to optical packages for integrated circuits. Background Art

[0004] Generally, a package for an integrated circuit includes an electrically connected electronic integrated circuit chip connected to a support substrate by connecting wires, which are commonly referred to as wire bonds.

[0005] The use of such connecting wires increases the size of the package.

[0006] When an electronic chip supports an optical device (such as a sensor or a transmitter), one solution includes placing the chip and the connecting wires in a housing coated with resin, and placing an optical pad or element, such as made of glass, above the chip and the connecting wires and supported on the edge of the housing.

[0007] However, such a solution increases the size of such an optical package.

[0008] To reduce this size, the connecting wires can be embedded in a coating made of resin, the chip equipped with its optical device can be placed in a housing made in the coating, and the optical pad can be placed above the chip.

[0009] However, such a solution requires the use of chips with large sizes.

[0010] This method limits the minimum size of the optical package, which is a drawback for integrating such a package into a device where volume is an important factor.

[0011] For example, the integration of an ambient light sensor (ALS) of the smartphone type into a phone is currently limited by the size of the package of this type of sensor.

[0012] Therefore, there is an even greater need to further reduce the size of the optical package of an integrated circuit. Summary of the Invention

[0013] According to one aspect, an optical package for an integrated circuit is proposed.

[0014] The package includes an electronic chip that supports an optical device (such as, but not limited to, an ambient light sensor) and an electrical connection area (such as pads known to those skilled in the art).

[0015] The package further includes an insulating coating (such as a resin) that coats the chip, covers the electrical connection area, and exposes the optical device.

[0016] The package further includes an optical plugging element, such as, but not limited to, a pane of an optically transmissive material (such as a glass material), which is at least partially fastened to the first face of the insulating coating, typically on its upper surface, and is optically coupled to the optical device.

[0017] In this case, optical coupling means, for example, optical cooperation between the optical plugging element and the optical device in such a way that, for example, the light flux emitted from and / or intended for the optical device passes through.

[0018] Such optical cooperation may also include optical filtering.

[0019] The package further includes a through-hole that passes through the coating from the first face of the coating to the second face opposite the first face, the second face being typically its lower surface, and the through-hole has an inner wall equipped with a conductive path that is connected to the electrical connection area of the chip on one hand through a conductive track arranged on the first face of the coating, and has a protruding end on the second face of the coating.

[0020] Therefore, in such a package, electrical connections are made directly in and on the coating of the chip, which allows eliminating the need for traditional connecting wires (wire bonding) and thus reducing the volume compared to traditional packages of the prior art.

[0021] Furthermore, the coating is open to expose the optical device of the chip, which allows restricting the size of the optical plugging element that can be supported on the edge of the opening and thus helps to obtain a package with a reduced size.

[0022] Such a package can be directly fixed to a printed circuit board or a circuit board, for example, through the protruding ends of the conductive paths lining the through-holes, and these protruding ends can be equipped with solder balls.

[0023] That is, according to one embodiment, the package may further include a support substrate that is at least partially fastened to the second face of the coating and has an interconnect network connected to the protruding ends of the conductive paths.

[0024] In this case, it is the support substrate that is equipped with solder balls, for example, which will be fastened to the printed circuit card.

[0025] According to one embodiment, the package includes a material for fastening an optical plug-in element, the material including an electrically insulating glue that is at least partially located around the optical device.

[0026] And the insulating glue beads can be at least partially disposed on the conductive tracks on the first side of the coating without causing a short circuit.

[0027] According to one embodiment, the optical plug-in element contains or supports a conductive element, and the material for fastening includes at least two discontinuous volumes of conductive glue configured to connect the two ends of the conductive element to the conductive tracks of the coating.

[0028] Thus, these tracks can be connected to a device configured to detect a possible breakage of the conductive element or the detachment of the optical plug-in element, and the device can be provided in the chip itself or outside the package.

[0029] Thus, such a conductive element integrated into the optical plug-in element allows indicating that the optical plug-in element is neither broken nor detached.

[0030] In particular, in the case where the optical device includes a laser source, the failure of the optical plug-in element can damage the observer's eyes; thus, it is advantageous to know the integrity state of the optical plug-in element.

[0031] According to one embodiment, the optical plug-in element is a sheet of material such as glass, which can be optically transmissive or filtering, or have various properties such as polarization, for example, but not limited to this.

[0032] According to one embodiment, the optical device is a device that emits and / or receives a light flux.

[0033] According to one embodiment, the optical device is an ambient light sensor.

[0034] According to another aspect, a method for manufacturing an optical package of an integrated circuit is provided, including: providing an electronic chip that supports an optical device and an electrical connection region; forming a thermally degradable protective layer covering the optical device; forming an insulating coating of the chip while covering the connection region except the protective layer; thermally degrading the protective layer to expose the optical device; generating a through hole passing through the coating from a first side to a second side opposite the first side, and a first pattern disposed on the first side of the coating and extending from the through hole to the electrical connection region and a second pattern extending from the through hole on the second side of the coating; generating a conductive path on the inner wall of the through hole, and generating conductive tracks in the first pattern and the second pattern so as to electrically connect the conductive path to the electrical connection region of the chip on the one hand and form an end portion of the conductive path protruding to the second side of the coating on the other hand; and fastening the optical plug-in element at least partially on the first side of the coating or on the conductive path so as to allow optical coupling between the optical plug-in element and the optical device.

[0035] According to one embodiment, via a direct shaping laser (e.g., laser direct structuring (LDS) technology), via holes, a first pattern, and a second pattern are formed, and conductive paths, traces, and ends of the conductive paths are formed by electroless plating.

[0036] According to one embodiment, the method further includes fastening a support substrate to a second surface of the coating, including connecting protruding ends of the conductive paths to an interconnection network of the support substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Other advantages and features of the present invention will become apparent upon examination of the detailed description of the embodiments and examples, which are in no way limiting, as well as the drawings, wherein:

[0038] Figure 1 A cross-sectional view of an optical package is schematically shown;

[0039] Figure 2 Shows a reference Figure 1 Top view of the optical package shown;

[0040] Figure 3 Shows steps of a method for manufacturing a package similar to the reference Figure 1 and Figure 2 described package;

[0041] Figure 4 A cross-sectional view of an optical package is schematically shown; and

[0042] Figure 5 Shows a reference Figure 4 Top view of the optical package shown. DETAILED DESCRIPTION

[0043] Figure 1 A cross-sectional view of an optical package BT of an integrated circuit according to one embodiment is schematically shown.

[0044] The package BT includes an electronic integrated circuit chip PO that supports an optical device DO and a connection area or pad ZC at its upper surface FS.

[0045] The package BT further includes a coating EN that coats the chip and an optical plug-in element MO that covers the optical device DO and forms the front face of the package BT.

[0046] The optical device DO of the chip PO can be, for example, an ambient light sensor of the ALS type. More generally, the optical device DO can be a device that emits and / or receives a light flux, such as a laser source.

[0047] The coating EN covers the upper surface of the chip PO, in particular the connection zone ZC of the chip, while leaving the optical device DO exposed to allow optical coupling with the optical plug-in element MO.

[0048] The coating has a first face F1 on the side of the optical device DO and a second face F2 opposite the first face, and the second face F2 includes conductive protruding ends ED forming the external connection zones of the package.

[0049] For example, the package BT can be directly connected to a printed circuit board through these electrical connection zones ED and optional solder balls.

[0050] Optionally, as Figure 1 shown, the second face F2 of the coating EN can be fastened to the support substrate SS, and the protruding ends ED are thus soldered to the interconnect network (not explicitly shown) of the substrate SS.

[0051] Electrical connections are provided in the coating EN to electrically connect the contact zone ZC of the chip PO and the protruding ends ED located on the second face F2 of the coating EN.

[0052] In this regard, the package BT includes a through-hole VA passing through the coating EN from the first face F1 to the second face F2.

[0053] Between the first face F1 and the second face F2 of the coating EN, the inner wall of the through-hole VA is lined with a conductive path CC made of, for example, metal.

[0054] On the first face of the coating EN, the conductive path CC of the through-hole VA is connected to a conductive track PC arranged on the coating surface up to the connection zone ZC of the chip PO, such as metal.

[0055] In particular, the perforations in the coating provided above the connection zone ZC are filled with a conductive material to connect the conductive track PC to these connection zones.

[0056] On the second face of the coating EN, the conductive path CC of the through-hole VA is connected to the protruding ends ED.

[0057] The conductive path CC, the conductive track PC, and the protruding ends ED can be made in the same conductive layer, such as a metal made of copper, a metal made of nickel, or a metal made of gold, or made in a combination of these three metals.

[0058] Furthermore, the optical plug-in element MO is fastened to the first face of the coating by a fastening material MF so as to protect the optical device DO on the one hand and optically couple with the optical device DO on the other hand.

[0059] The optical plug-in element MO can be an optically transmissive or filtering glass sheet fastened to the coating EN by the fastening material MF.

[0060] For example, the optical plug-in element MO may further include a scattering glass panel to render the laser source harmless to the eyes of an observer.

[0061] The fastening material MF may be continuous or discontinuous electrically insulating glue beads deposited on the first face of the coating EN around the optical device DO.

[0062] Such electrically insulating glue is conventional and known per se.

[0063] The glue beads may be in contact with the coating EN and / or with the metal tracks PC.

[0064] Figure 2 A top view of the package BT described with reference Figure 1 is shown, in which the optical plug-in element and the fastening material are not shown in order to expose the first face F1 of the coating EN and the conductive tracks PC.

[0065] The coating EN partially covers the upper surface FS of the electronic chip PO, thus covering the connection areas (pads) of the chip while leaving the area occupied by the optical device DO.

[0066] The coating EN includes a boundary around the side edges of the chip PO, in which through-holes VA are hollowed out perpendicular to the first face F1 of the coating EN.

[0067] Figure 3 An example of steps of a method for manufacturing a package similar to that described above with reference Figure 1 and Figure 2 is shown.

[0068] The method includes providing an electronic chip PO that supports the optical device DO and the electrical connection areas (pads).

[0069] Although only providing the electronic chip is mentioned herein, in practice the method includes providing a wafer or sheet of a semiconductor substrate, for example made of silicon, including a set of already manufactured electronic chips PO ready to be separated or individualized along the tangents of the sheet (a process or technique known in the art as singulation).

[0070] The method includes the formation S1 of a thermally degradable protective layer MSS of the optical devices covering the entire sheet and thus each electronic chip PO of the sheet.

[0071] The protective layer MSS is formed of a temporary sacrificial material that can be thermally destroyed, such as the foam REVALPHA N°3195VS produced by NITTO Corporation.

[0072] Forming the thermally degradable protective layer MSS on each optical device includes, for example, depositing the protective layer over the entire sheet and then performing lithography so as to leave the protective layer only on the optical devices.

[0073] The deposition of the protective layer MSS is carried out, for example, by a spin coater by rotating the wafer using a rotating support and by using a tool for dispensing the material of the protective layer MSS.

[0074] The viscosity of the material of the protective layer MSS, the rotation speed of the support, and the amount of deposited material allow for the dispersion and control of the final thickness and flatness of the protective layer. In fact, the thickness and flatness of the protective layer MSS allow ensuring the quality of the openings in the coating that allow the exposure of the optical devices DO of the chip PO.

[0075] Then, the method includes separating or individuating the S2 electronic chips PO by cutting the wafer along a tangent (i.e., a single cut).

[0076] In step S3, the electronic chips PO are prepared to form a coating EN with a coating material.

[0077] The coating material includes, for example, a resin including a metal-organic complex primer, and the metal-organic complex primer can be locally activated by a method called laser direct structuring (LDS) to subsequently allow electroless plating of a metal layer on the activated part of the coating.

[0078] Step S3 includes, for example, flipping the chips and then coating the protective layer MSS of each chip PO onto a plastic film.

[0079] Advantageously, a controlled distance can be maintained between the chips to account for the shrinkage of the coating resin after drying. In addition, the plastic film is provided with reduced adhesion during the heat treatment.

[0080] Once the chips are bonded, step S3 includes molding the coating material so as to form a sheet of the coating material that connects the chips PO to each other.

[0081] The formation of the insulating coating EN includes, for example, applying pressure to the coating material to fill the voids so as to particularly form a first face F1 of each coating EN that covers the connection areas (pads) of each chip PO.

[0082] Then, step S3 includes a first heat treatment to cure the coating resin.

[0083] The first heat treatment includes heating the coating resin to a temperature between, for example, 150 - 160 degrees Celsius in order to polymerize it.

[0084] In this example, the protective layer MSS starts to degrade while the coating resin cures, but the onset of this degradation is not harmful here due to the lack of movement of the wafer.

[0085] That is, the method then advantageously includes completing the thermal degradation of the protective layer MSS in step S4, allowing the exposure of each optical device DO.

[0086] This thermal degradation S4 of the protective layer MSS can be achieved by a second heat treatment, which includes heating the wafer to a temperature of, for example, about 180 degrees Celsius. During the second heat treatment, the protective layer MSS completely disintegrates, but the polymerized coating resin remains unaffected.

[0087] After the thermal degradation step S4, the package BT undergoes a cleaning S5, for example with water, in particular cleaning the optical devices DO on the chip PO.

[0088] Then, an electrical connection is produced that includes metal tracks PC, vias lined with conductive tracks CC, and protruding ends ED.

[0089] The production of the electrical connection can be achieved in two stages, for example by combining electroless plating and direct laser writing.

[0090] First, the production of the connection includes, for example, creating S6 vias, as well as a first pattern MF1 and a second pattern MTF2, using, for example, a direct laser writer.

[0091] The creation S6 of the vias VA includes the hollowing out of vias extending from a first side of the coating EN to a second side in the coating EN.

[0092] The creation S6 of the first pattern MTF1 includes etching the resin at the location of the future conductive tracks PC on the first side of the coating EN such that the first pattern extends from the via VA to the electrical connection area ZC.

[0093] The creation S6 of the second pattern MTF2 includes etching the resin at the location of the future protruding ends ED on the second side of the coating EN such that the second pattern extends from the via VA on the second side F2.

[0094] Then, in step S7, conductive paths CC, conductive tracks PC, and protruding ends ED are formed by electroless plating, for example by dipping the wafer into an electroless plating solution.

[0095] Once the electrical connection has been made, the method then includes sawing S8 the wafer along a cutting path in such a way that each chip PO coated in its coating EN is individualized (likewise, this process is called singulation).

[0096] The method can also include an optional fastening S9 of the support substrate SS under the coating EN.

[0097] The fastening S9 of the support substrate to the second side of the coating EN includes, for example, soldering the protruding ends ED to the interconnect network of the substrate SS.

[0098] There is also provided a method of fastening an optical plug-in element S10 to a first side of a coating EN by using a fastening material MF so as to allow optical coupling between the optical plug-in element MO and an optical device DO.

[0099] The fastening of the optical plug-in element may include dispensing insulating glue beads around the optical device DO, for example, on the first side of the coating EN, optionally on a conductive track PC.

[0100] The present invention is not limited to the implementations and embodiments just described.

[0101] Thus, as Figure 4 schematically shown, optionally, the package BT may be provided with a conductive element ELM that allows verification of the integrity of the optical plug-in element MO.

[0102] The optical plug-in element MO may be, for example, a glass sheet including a conductive element, such as a conductive wire ELM that weaves through the glass sheet.

[0103] Optionally, the conductive element formed by the wire ELM may be wound around the surface of the glass panel.

[0104] The conductive element is connected to the chip by conductive glue MF1 spots provided on different parts of the conductive path PC, thereby forming a conductive path.

[0105] As Figure 5 more specifically shown, Figure 5 is a top view of the optical plug-in element, and the fastening of the optical plug-in element MO to the coating and the conductive track may be accomplished by insulating glue beads MF provided between the spots of the conductive glue MF1.

[0106] Two tracks that are respectively electrically connected to the conductive element are also respectively connected to, for example, a current source that allows current to be injected into the conductive element wire ELM and a device (such as a circuit) for detecting current.

[0107] The current source and the current detection device may be incorporated into the chip or may be provided outside the package.

[0108] If the chip detects the presence (no current interruption) of the conductive path (current interruption), this indicates compliance with the integrity of the optical plug-in element MO.

[0109] Conversely, if the chip detects an interruption of the conductive path, this indicates that the optical plug-in element is broken or separated, and thus the integrity of the optical plug-in element MO is no longer complied with.

[0110] Of course, in this embodiment, Figure 3Step S10 further includes a previous step of forming two volumes of conductive glue MF1 between the insulating glue MF and manufacturing the optical plug-in element MO in a manner including the conductive element wire ELM.

Claims

1. A method for manufacturing an optical package, the optical package including an electronic integrated circuit chip that supports an optical device and an electrical connection region, the method comprises: forming a thermally degradable protective layer covering the optical device; forming an insulating coating that coats the electronic integrated circuit chip while covering the electrical connection region but not covering the thermally degradable protective layer; performing a heat treatment to degrade the thermally degradable protective layer and expose the optical device; generating a through-hole that passes through the insulating coating from a first surface to a second surface opposite the first surface; generating a first pattern disposed on the first surface of the insulating coating and extending from the through-hole to the electrical connection region; generating a second pattern extending from the through-hole on the second surface of the insulating coating; forming a conductive path in the through-hole; forming conductive tracks in the first pattern and the second pattern; wherein the conductive tracks electrically connect the conductive path to the electrical connection region of the electronic integrated circuit chip at the first surface of the insulating coating and form a protruding structure on the second surface of the insulating coating; and fastening an optical plug-in element at least partially to a position on the first surface of the insulating coating that supports an optical coupling between the optical plug-in element and the optical device.

2. The method according to claim 1, wherein generating the through-hole and generating the first pattern and the second pattern are achieved by applying a direct molding laser.

3. The method according to claim 2, wherein forming the conductive path and the conductive tracks includes performing electroless plating.

4. The method according to claim 1, further comprising fastening a support substrate to the second surface of the insulating coating.

5. The method according to claim 4, further comprising electrically connecting the protruding structure at the second surface of the insulating coating to the support substrate.

6. The method according to claim 5, wherein the support substrate includes an interconnect network that is electrically connected to the protruding structure.

7. The method according to claim 1, further comprising forming the optical plug-in element to include a conductive element, and wherein fastening the optical plug-in element further includes electrically connecting an end of the conductive element to the conductive track.

8. The method according to claim 7, wherein fastening includes using a conductive adhesive.

9. The method according to claim 1, wherein the optical plug-in element is a sheet of material that is one or more of optically transmissive, filtering, and polarizing.

10. The method according to claim 1, wherein the optical device is an integrated circuit configured to perform one or more of the following: emitting a light flux and receiving a light flux.

11. The method according to claim 1, wherein the optical device is an ambient light sensor.

12. An optical package, comprising: an electronic integrated circuit chip that supports an optical device and an electrical connection region; An insulating coating that coats the electronic integrated circuit chip by exposing the optical device while covering the electrical connection regions and the peripheral sides of the electronic integrated circuit chip; A sheet of optically transmissive material that is at least partially fastened to a first face of the insulating coating and optically coupled to the optical device; And Through holes that pass through the insulating coating from the first face to a second face opposite the first face, each through hole having an electrical conduction path that is connected at a first end to the electrical connection region of the electronic integrated circuit chip by a conductive track disposed on the first face of the insulating coating, and each through hole having a second end located on the second face of the insulating coating; Wherein the sheet of optically transmissive material includes a wire extending from a first end to a second end over the optical device; Electrically insulating beadlets that are at least partially located around the optical device to fasten the sheet of optically transmissive material to the first face of the insulating coating; Spots of conductive adhesive that electrically connect the first and second ends of the wire to the conductive tracks disposed on the first face of the insulating coating.

13. The package according to claim 12, further comprising a support substrate that is at least partially fastened to the second face of the insulating coating, wherein the second end of the electrical conduction path for the through hole is electrically connected to the support substrate.

14. The package according to claim 13, wherein the support substrate includes an interconnect network that is electrically connected to the second end of the electrical conduction path.

15. The package according to claim 12, wherein the sheet of optically transmissive material is one or more of filtering and polarization.

16. The package according to claim 12, wherein the optical device is an integrated circuit configured to perform one or more of: emitting a light flux and receiving a light flux.

17. The package according to claim 12, wherein the optical device is an ambient light sensor.

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