This application claims the priority benefit of Italian Application for Patent No. 102023000006129 filed on Mar. 29, 2023, the content of which is hereby incorporated by reference in its entirety to the maximum extent allowable by law.
The description relates to manufacturing semiconductor devices.
Solutions as described herein can be applied, for instance, to Quad Flat No-Leads (QFN) packages for integrated circuit (IC) semiconductor devices for automotive or industrial application.
In packages such as Quad Flat No-leads (QFN) packages, interconnections may be provided via laser direct structuring (LDS).
LDS is based on laser ablation of a molding compound having additive particles embedded therein and that are activated during laser ablation. Activated particles facilitate subsequent plating steps that form electrically conductive interconnections as desired.
In certain QFN packages comprising, for instance, a relatively thick die or two (or more) stacked dice, some interconnections may end up by being located deep inside the molding compound to provide a desired coupling and such deep interconnects (such as deep vias, for instance) may give rise to design and plating issues.
In fact, laser machining cannot drill “vertically” through a molding compound and through-mold-vias (TMVs) are rather formed with a conical shape. To adequately plate such a conical TMV the diameter of the via at the base of the conical shape should be approximately equal to the depth of the via (i.e., a 1:1 aspect ratio).
For deep interconnects, such a design rule may pose constraints in so far as vias may not fit with package dimensions.
There is a need in the art for solutions that address the issues discussed in the foregoing.
One or more embodiments relate to a method.
One or more embodiments relate to a corresponding (integrated circuit) semiconductor device.
Solutions as described herein provide a time- and cost-effective method of forming electrically conductive through-mold-vias via laser direct structuring, LDS.
Solutions as described herein facilitate manufacturing semiconductor devices comprising thick or stacked dice.
Solutions as described herein may be used to form die-to-lead as well as die-to-die interconnects.
In solutions as described herein, the thickness of the (LDS) molding compound that is laser drilled is reduced by removing a portion of molding compound prior to drilling.
Solutions as described herein are compatible with concurrent processing of a plurality of semiconductor devices.
One or more embodiments will now be described, by way of example only, with reference to the annexed figures, wherein:
Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated.
The figures are drawn to clearly illustrate the relevant aspects of the embodiments and are not necessarily drawn to scale.
The edges of features drawn in the figures do not necessarily indicate the termination of the extent of the feature.
In the ensuing description one or more specific details are illustrated, aimed at providing an in-depth understanding of examples of embodiments of this description. The embodiments may be obtained without one or more of the specific details, or with other methods, components, materials, etc. In other cases, known structures, materials, or operations are not illustrated or described in detail so that certain aspects of embodiments will not be obscured.
Reference to “an embodiment” or “one embodiment” in the framework of the present description is intended to indicate that a particular configuration, structure, or characteristic described in relation to the embodiment is comprised in at least one embodiment. Hence, phrases such as “in an embodiment” or “in one embodiment” that may be present in one or more points of the present description do not necessarily refer to one and the same embodiment.
Moreover, particular conformations, structures, or characteristics may be combined in any adequate way in one or more embodiments.
The headings/references used herein are provided merely for convenience and hence do not define the extent of protection or the scope of the embodiments.
For simplicity and ease of explanation, throughout this description, and unless the context indicates otherwise, like parts or elements are indicated in the various figures with like reference signs, and a corresponding description will not be repeated for each and every figure.
Laser direct structuring is a laser-based machining technique now widely used in various sectors of the industrial and consumer electronics markets, for instance for high-performance antenna integration, where an antenna design can be directly formed onto a molded plastic part.
In an exemplary process, the molded parts can be produced with commercially available insulating resins that include additives suitable for the LDS process; a broad range of resins such as polymer resins like PC, PC/ABS, ABS, LCP are currently available for that purpose.
In LDS, a laser beam can be used to transfer (“structure”) a desired electrically-conductive pattern onto a plastic molding that may then be subjected to metallization to finalize a desired conductive pattern.
Metallization (with copper, for instance) may involve electroless plating followed by electrolytic plating.
Electroless plating, also known as chemical plating, is a class of industrial chemical processes that creates metal coatings on various materials by autocatalytic chemical reduction of metal cations in a liquid bath.
In electrolytic plating, an electric field between an anode and a workpiece, acting as a cathode, forces positively charged metal ions to move to the cathode where they give up their charge and deposit as metal on the surface of the work piece.
Reference is made to United States Patent Publication Nos. 2018/0342453, 2019/0115287, 2020/0203264, 2020/0321274, 2021/0050226, 2021/0050299, 2021/0183748, or 2021/0305203 (all incorporated herein by reference) as exemplary of the possibility of applying LDS technology in manufacturing semiconductor devices.
As used herein the terms die/dice and chip/chips are regarded as synonymous.
Electrically conductive formations 181, 182, 183 as illustrated in
In the case exemplified in
As mentioned, plating metallic material (metallization) may involve an electroless plating step (facilitated by the activated LDS particles in the molding compound 20) followed by electrolytic plating step.
Providing interconnects as illustrated in
It is thus desirable to provide interconnects using the LDS processing technique to as many device/package classes or types as possible.
Conventional LDS technique as described in the foregoing may suffer from limitations such as, for instance: laser ablation cannot drill “vertically” through the molding compound, and through-mold-vias (TMVs) are formed with a conical shape; and in order to adequately plate such a conical TMV the diameter of the via at the base of the cone should be approximately equal to the depth of the via (i.e., a 1:1 aspect ratio).
For instance,
If electrical coupling is desired to be provided between the die 14 (the die pad 16 on the front/top surface thereof) and the lead 12B, the relatively large thickness of the die 14 will cause the (through-mold) via 183 to extend in the LDS material for a depth T1 that, in certain cases, may be up to 600 microns.
As illustrated, application of a conventional LDS technique as described in the foregoing produces a via 183 having a diameter (indicated as D in the figure) at the front surface of the encapsulation approximately equal to the depth T1 of the via 183 (so as to achieve the 1:1 aspect ratio).
Forming a via 183 as illustrated in
Furthermore, the large area occupied by the via 183 at the front surface of the encapsulation may pose design constraints to the packages.
Similar issues may arise in a device as illustrated in
Solutions as described herein propose a time-effective method for forming electrically conductive through-mold-vias or interconnects via laser direct structuring, LDS.
Solutions as described herein may advantageously be applied to form interconnects in packages comprising thick or stacked dice.
In solutions as described herein, the thickness of the (LDS) molding compound that is drilled to form a via is reduced by removing a portion of molding compound, prior to laser drilling/ablation.
Solutions as described herein are compatible with concurrent processing of a plurality of semiconductor devices.
In the following, various embodiments of the present description will be described. The particular applications described are, however, merely exemplary in as much as the method described herein provides an improved and time-efficient way to provide through-mold-vias in an LDS molding compound/material. As those skilled in the art may appreciate, such a method may be applied in other cases than those discussed in the present description.
In current manufacturing processes of semiconductor devices, plural devices are manufactured concurrently to be separated into single individual device in a final singulation. For simplicity and ease of explanation, the following description will first refer to manufacturing a single device and the case of a plurality of semiconductor devices will be discussed in a later section.
The sequence of steps of
The substrate S may be a tape or a carrier, for instance, that facilitates concurrent processing of a plurality of (IC) semiconductor devices.
According to various embodiments of the present description the substrate S may be a so-called leadframe and the semiconductor die 14 is arranged at a die mounting location (die pad) of the leadframe.
According to various embodiments of the present description the substrate S may be a sacrificial substrate, intended to be removed after processing.
In the case exemplified in
Cavities or trenches 100 as illustrated in
Partial cutting as illustrated in the figure is oftentimes referred to as “half-cutting”: this is a common designation in the art, which does not imply that such partial cutting is by necessity to exactly half the total thickness of LDS molding material 20.
Partially removing the LDS material 20 results in a second surface 100A of the LDS material being exposed on the front/top of the assembly.
As illustrated in the figure, the thickness of the molding material 20 between the second surface 100A thereof and the lead 12B has been reduced from the thickness T1 to a thickness T2.
Vias 181′ to the die pad 16 and traces 182′ providing a path between vias 183′ and 181′ are provided via laser ablation/drilling as well.
It is noted that traces 182′ extend from the top/front surface of the LDS material 20 and the second surface 100A of the LDS molding material exposed as a result of the formation of a trench 100.
Traces 182′ may also comprise a portion extending in the trench/cavities 100, at a side wall thereof, as well as portion extending on the front/top surface of the encapsulation of LDS material 20.
Laser ablation as illustrated in
As mentioned, metallization may involve two plating steps: an electroless plating step where the growth of a seed layer (of copper, for instance) in regions 181′, 182′ and 183′ is facilitated by the LDS molding compound 20 being activated therein; and an electrolytic plating step to grow further electrically conductive material on the seed layer deposited previously to form the electrically conductive path 181, 182, 183 (now referenced without an accent in order to highlight the fact that electrically conductive material has been grown therein).
As illustrated in
It is noted that metallization as illustrated occurs only in those regions (181′, 182 and 183′ in the case exemplified in the figures) where the LDS molding compound 20 has been (laser-) activated. Removing LDS material to form trenches 100 does not activate the LDS material and, as illustrated, no electrically conductive material is deposited on the side surfaces of the trench 100, for instance.
The second molding compound may be a standard (that is, non-LDS) molding compound such as an epoxy resin, for instance.
A method according to embodiments of the present description may applied to the case of a “stacked” dice arrangement, as illustrated in the sequence of
The sequence of
It is noted that in such a stacked arrangement as illustrated in
The semiconductor dice 14A, 14B have respective die pads 16A, 16B on the front/top surface thereof.
The total thickness of the stacked dice 14A, 14B may in certain cases exceed 600 microns but is less than the thickness T1.
As illustrated, in addition to form vias 181′, 183′ and traces 182′, additional “standard” vias 281′, and traces 282′ may be concurrently formed (via laser ablation/drilling) to provide a path between the die pads 16A and 16B.
The assembly may be processed in a similar way to what has been discussed in relation to
As mentioned, the method described herein is not limited to formation of vias towards a lead 12B as discussed in the foregoing, but it can be applied to form vias to electrically conductive formations in general.
For instance, the method described herein may be advantageously applied in a stacked dice arrangement as exemplified in
In certain cases, it is desirable to provide electrical coupling between a first semiconductor die 14A (600 microns thick, for instance) arranged on a second die 14B in a stacked dice configuration.
As illustrated in
Processing to obtain a device as illustrated in
It is noted that, in the example illustrated in
The method described herein may advantageously be applied in cases other than those presented in the foregoing, as it provides an advantageous way to provide electrical coupling to a component (such a lead 12B or a die 14B, for instance) via LDS technique.
More generally, a method as described herein may be summarized as follows.
LDS material 20 is molded onto a semiconductor die/chip 14 (or 14A) arranged on a substrate S (or 14B) with a first (front) surface facing away from the substrate.
At least one electrically conductive formation 12B/16B is arranged on the substrate S/14B, adjacent to semiconductor chip 14/14A.
The LDS material 20 has a first thickness T1 between a front surface of the LDS material 20) and the substrate S/14B.
Laser beam energy LB is applied to the LDS material 20 in order to laser structure therein at least one via 183′ towards the electrically conductive formation 12B/16B.
The first surface of the semiconductor chip 14/14A and the electrically conductive formation 12B/16B are electrically coupled (via the conductive path formed by 181, 182, 183) with electrically conductive material (for instance, copper) in the at least one via 183′ laser structured in the LDS material 20.
Unstructured LDS material is removed (for instance, via sawing B) from the front surface of the LDS material 20 to form therein a cavity (or trench) 100 having an end wall 100A between the front surface of the LDS material 20 and the electrically conductive formation 12B/16B, so that the LDS material at the cavity 100 has a second thickness T2 smaller than the first thickness T2<T1.
Laser beam energy LB is applied to the LDS material 20 at the end wall 100A of the cavity/trench 100 to laser structure therein the via 183′ that extends between the end wall 100A of the cavity 100 and the conductive formation 12B/16B.
Laser beam energy LB may also be applied to laser structure the LDS material 20 at a side wall of the cavity 100 adjacent the semiconductor chip 14/14A with electrically conductive material 182 grown on LDS material 20 laser-structured at the side wall of the cavity 100, thus forming.
The LDS material 20 may be laser structured also to form one further via 181′ towards the first surface of the semiconductor chip 14/14A.
The method of manufacturing described so far may also be applied to the case where a plurality of integrated circuit semiconductor devices is processed concurrently.
Concurrent processing may be done by arranging a plurality of semiconductor dice on a carrier such as a tape, a panel or a wafer carrier; as those skilled in the art may appreciate, the method described herein may be applied irrespective of the particular shape of the carrier.
As illustrated, LDS molding compound 20 is molded onto the plurality of semiconductor dice 14 arranged on the carrier.
In the case exemplified in
Trenches 100 are formed in the LDS compound 20 running at the periphery of the devices and passing over the leads 12B. As illustrated trenches 100 may be formed extending throughout the length and the width of the panel (or tap or wafer), thus reducing the thickness of the LDS molding compound 20 above the leads 12B of a plurality of semiconductor device with a single (half-) cut.
Vias 181′ to the die pads (not visible for simplicity), vias 183′ to the leads 12B and traces 182′ with a desired pattern are formed via laser ablation.
As illustrated, vias 183′ are laser drilled at trenches 100 through the LDS compound 20 layer with reduced thickness.
Further processing steps may comprise: a second molding step, possibly with a non-LDS compound; and a singulation step where the panel is cut into individual devices by cutting/sawing (full cut) along the cutting lines CL with a blade, for instance.
Without prejudice to the underlying principles, the details and embodiments may vary, even significantly, with respect to what has been described by way of example only without departing from the extent of protection.
The claims are an integral part of the technical teaching provided in respect of the embodiments.
The extent of protection is determined by the annexed claims.
Number | Date | Country | Kind |
---|---|---|---|
102023000006129 | Mar 2023 | IT | national |