EMI shielded wafer level fan-out pop package

[0001] This application claims priority to U.S. Provisional Patent Application No. 61/980,830 entitled “EMI SHIELDED WAFER LEVEL FAN-OUT POP PACKAGE” to Zhai et al. filed on Apr. 17, 2014, all of which is incorporated by reference herein.

[0002] 1. Technical Field

[0003] Embodiments described herein relate to semiconductor packaging and methods for packaging semiconductor devices. More particularly, some embodiments disclosed herein relate to shielding package-on-package (“PoP”) from electromagnetic interference.

[0004] 2. Description of the Related Art

[0005] Package-on-package (“PoP”) technology has become increasingly popular as the demand for lower cost, higher performance, increased integrated circuit density, and increased package density continues in the semiconductor industry. As the push for smaller and smaller packages increases, the integration of die and package (e.g., “pre-stacking” or the integration of system on a chip (“SoC”) technology with memory technology) allows for thinner packages. Such pre-stacking has become a critical component for thin and fine pitch PoP packages. FIG. 1 depicts an embodiment of a current package on package format 100. Package 100 may include several air gaps 110 which are formed within the package during manufacture. However, air is known as a very good insulator and as such results in poor thermal conduction between the components of the package.

[0006] EMI (“electromagnetic interference”) is the unwanted effects in the electrical system due to electromagnetic radiation and electromagnetic conduction. Electromagnetic radiation and electromagnetic conduction are different in the way an EM field propagates. Conducted EMI is caused by the physical contact of the conductors as opposed to radiated EMI which is caused by induction. Electromagnetic disturbances in the EM field of a conductor will no longer be confined to the surface of the conductor and may radiate away from it. Mutual inductance between two radiated electromagnetic fields may result in EMI.

[0007] Due to EMI, the electromagnetic field around the conductor is no longer evenly distributed (e.g., resulting in skin effects, proximity effects, hysteresis losses, transients, voltage drops, electromagnetic disturbances, EMP/HEMP, eddy current losses, harmonic distortion, and reduction in the permeability of the material).

[0008] EMI can be conductive and/or radiative and its behavior is dependent on the frequency of operation and cannot be controlled at higher frequencies. For lower frequencies, EMI is caused by conduction (e.g., resulting in skin effects) and, for higher frequencies, by radiation (e.g., resulting in proximity effects).

[0009] A high frequency electromagnetic signal makes every conductor an antenna, in the sense that they can generate and absorb electromagnetic fields. In the case of a printed circuit board (“PCB”), consisting of capacitors and semiconductor devices soldered to the board, the capacitors and soldering function like antennas, generating and absorbing electromagnetic fields. The chips on these boards are so close to each other that the chances of conducted and radiated EMI are significant. Boards are designed in such a way that the case of the board is connected to the ground and the radiated EMI is typically diverted to ground. Technological advancements have drastically reduced the size of chipboards and electronics; however, this means they are also much more sensitive to EMI. Typically electromagnetic shielding is used to inhibit EMI effects. However, EMI shielding can be expensive and may have negative consequences.

[0010] In some embodiments, an EMI self-shielded wafer level PoP structure is provided that provides high EMI shield effectiveness. In some embodiments, EMI self-shielding may be achieved by coating conductive material over the surface of the PoP package. The coating material may be applied by processes such as sputter/CVD/spray/etc. The high electrically conductive coating layer may consist of multiple layers having high permeability difference between adjacent layers that enhance EMI attenuation and reflectance. The shielding layer may be electrically connected to a redistribution layer, ground terminals, vias, or traces that are engineered to be exposed at the package side surface. In some embodiments, a metal lid applied on top of PoP for thermal enhancement purpose may be partially or fully connected to the shielding layer, and further enhances EMI shielding performance.

[0011] In some embodiments, a semiconductor device package assembly may include a first substrate. The first substrate may include a first surface and a second surface substantially opposite of the first surface. The first substrate may include a first set of electrical conductors coupled to the first surface. The first set of electrical conductors may function to electrically connect the semiconductor device package assembly. The first surface may be equivalent a lower surface of the semiconductor device package assembly. In some embodiments, the semiconductor device package assembly may include at least one electrical conductor. The electrical conductor may be electrically coupled to the first substrate. The electrical conductor may be such that at least one of the electrical conductors exposes through a perimeter surface of the semiconductor device package assembly. In some embodiments, the semiconductor device package assembly may include a first die. The first die may be electrically connected to the second surface of the first substrate using a second set of electrical conductors. In some embodiments, the semiconductor device package assembly may include an electronic memory module coupled to the first die. In some embodiments, the semiconductor device package assembly may include a shield. The shield may be applied to an upper surface of the semiconductor device package assembly. The shield may be electrically coupled to at least one of the exposed electrical conductors. The shield may inhibit, during use, electromagnetic interference.

[0022] Specific embodiments are shown by way of example in the drawings and will be described herein in detail. It should be understood, however, that the drawings and detailed description are not intended to limit the claims to the particular embodiments disclosed, even where only a single embodiment is described with respect to a particular feature. On the contrary, the intention is to cover all modifications, equivalents and alternatives that would be apparent to a person skilled in the art having the benefit of this disclosure. Examples of features provided in the disclosure are intended to be illustrative rather than restrictive unless stated otherwise.

[0023] The headings used herein are for organizational purposes only and are not meant to be used to limit the scope of the description. As used throughout this application, the word “may” is used in a permissive sense (i.e., meaning having the potential to), rather than the mandatory sense (i.e., meaning must). The words “include,” “including,” and “includes” indicate open-ended relationships and therefore mean including, but not limited to. Similarly, the words “have,” “having,” and “has” also indicated open-ended relationships, and thus mean having, but not limited to. The terms “first,” “second,” “third,” and so forth as used herein are used as labels for nouns that they precede, and do not imply any type of ordering (e.g., spatial, temporal, logical, etc.) unless such an ordering is otherwise explicitly indicated. For example, a “third die electrically connected to the module substrate” does not preclude scenarios in which a “fourth die electrically connected to the module substrate” is connected prior to the third die, unless otherwise specified. Similarly, a “second” feature does not require that a “first” feature be implemented prior to the “second” feature, unless otherwise specified.

[0024] Various components may be described as “configured to” perform a task or tasks. In such contexts, “configured to” is a broad recitation generally meaning “having structure that” performs the task or tasks during operation. As such, the component can be configured to perform the task even when the component is not currently performing that task (e.g., a set of electrical conductors may be configured to electrically connect a module to another module, even when the two modules are not connected). In some contexts, “configured to” may be a broad recitation of structure generally meaning “having circuitry that” performs the task or tasks during operation. As such, the component can be configured to perform the task even when the component is not currently on. In general, the circuitry that forms the structure corresponding to “configured to” may include hardware circuits.

[0025] Various components may be described as performing a task or tasks, for convenience in the description. Such descriptions should be interpreted as including the phrase “configured to.” Reciting a component that is configured to perform one or more tasks is expressly intended not to invoke 35 U.S.C. §112 paragraph (f), interpretation for that component.

[0026] The scope of the present disclosure includes any feature or combination of features disclosed herein (either explicitly or implicitly), or any generalization thereof, whether or not it mitigates any or all of the problems addressed herein. Accordingly, new claims may be formulated during prosecution of this application (or an application claiming priority thereto) to any such combination of features. In particular, with reference to the appended claims, features from dependent claims may be combined with those of the independent claims and features from respective independent claims may be combined in any appropriate manner and not merely in the specific combinations enumerated in the appended claims.

[0027] This specification includes references to “one embodiment” or “an embodiment.” The appearances of the phrases “in one embodiment” or “in an embodiment” do not necessarily refer to the same embodiment. Particular features, structures, or characteristics may be combined in any suitable manner consistent with this disclosure.

[0028] FIG. 2 depicts an embodiment of a thermally enhanced package on package format 200 including two redistribution layers. At least some of the electrical conductors are not depicted for the sake of clarity. In some embodiments, a semiconductor device package assembly 200 may include a first substrate 210 (or a first redistribution layer) including a first surface 220, a second surface 230 substantially opposite of the first surface, and a first set of electrical conductors 240 coupled to the first surface. The first set of electrical conductors may function to electrically connect the semiconductor device package assembly to, for example, other electrical components. The semiconductor device package assembly may include a first die 250 electrically connected to the second surface of the first substrate using a second set of electrical conductors 260 such that the first die is directly bonded to the first substrate. The second set of electrical conductors may function to electrically connect 245 to at least some of the first set of electrical conductors through the redistribution layer 210. The semiconductor device package assembly may include a third set of electrical conductors 270 coupled to the second surface of the first substrate. The third set of electrical conductors may function to electrically connect 265 to at least some of the first set of electrical conductors 240 and/or to the second set of electrical connectors 260, through the redistribution layer 210. The semiconductor device package assembly may include a second substrate (or second redistribution layer) 280 including a first surface 290 and a second surface 300 substantially opposite of the first surface. The first surface may be directly bonded to a surface 275 of the first die opposite the second set of electrical conductors. The semiconductor device package assembly may include an electronic memory module 310. The electronic memory module may include a third substrate (or third redistribution layer) 320 including a first surface 330 and a second surface 340 substantially opposite of the first surface. The first surface may be directly bonded to the second surface of the second substrate using a fourth set of electrical conductors 350. The second surface may be coupled to a fifth set of conductors 420 on the second die 410.

[0029] Generally, the redistribution layers 210, 280, and 320 may include conductors and electrically insulating material to form connections between conductors bonded to the top surface of the redistribution layer and conductors bonded to the bottom surface of the redistribution layer. That is, the redistribution layer may provide connection between conductors that are not vertically aligned with each other (although vertically aligned connections may also be made). Since the redistribution layers include metal conductors, they may also be efficient heat conductors as well. The redistribution layers may also serve as substrates for carrying the various semiconductor die 250 and 410, providing structure as well, in the illustrated embodiments. Other embodiments may include other types of substrates as desired.

[0030] Each of the die 250 and 410 may be encapsulated using any suitable encapsulant. The encapsulant may protect the die and provide structural stability.

[0031] The semiconductor device package assembly may include a thermally conductive material 360 directly applied to a second surface 370 of the electronic memory module. The semiconductor device package assembly may include a heat spreader 380 including a first side 390 and a second side 400 substantially opposite the first side. The first side may be directly bonded to the thermally conductive material. The heat spreader may function to transfer heat from the first die and the electronic memory module through the heat spreader from the first side to the second side.

[0032] The heat spreader may function as a heat exchanger that moves heat between a heat source, and a secondary heat exchanger whose surface area and geometry are more favorable than the source. Such a spreader is most often simply a plate made of copper, which has a high thermal conductivity. In some embodiments, if height is not an issue, and heat spreader may further include a heat sink (e.g. fins to conduct the heat into the air or the like).

[0033] Heat spreaders transfer heat from electronic components to passive or active heat sinks. Typically they are used to cool chips in personal computers, laptops, notebooks, cell phones, and other electronic devices. Heat spreaders are used in critical locations for more efficient heat removal. Heat spreaders may be used to reduce electrical component hot spots, such that the component's lifetime is increased and the component's performance is improved.

[0034] In some embodiments, the heat spreader may provide structural stability to the package assembly. The cover may be formed from, for example, copper, aluminum alloys, high thermal conductivity ceramics, composite graphite, etc.

[0035] Directly bonding the different layers of the package directly to one another substantially removes any air gaps in the package relative to the configuration illustrated in FIG. 1. In some embodiments, substantially no air gap is present between the electronic memory module and the second substrate. In some embodiments, heat travels from the first die to the heat spreader without traversing an air gap. In the current embodiments described herein have significantly improved thermal resistance compared to packages produced with air gaps.

[0036] Directly bonding layers of the package together may result in low profile (e.g., Z height<1 mm) packages. Z height may be reduced by using fan out configurations for one or more components of the package. For example, the electronic memory module 310 may include two or more die 410 (e.g., as depicted in FIGS. 2-3) in what is commonly known as a fan out configuration. In some embodiments, first and/or second die may be coupled as flip chip configurations.

[0037] FIG. 3 depicts an embodiment of a thermally enhanced package on package format 200 including one redistribution layer. At least some of the electrical conductors are not depicted for the sake of clarity. In some embodiments, the package may include only one redistribution layer. For example, as depicted in FIG. 3 the package 200 may not include a second substrate 280. In such an embodiment fourth set of electrical conductors 350 may be directly bonded to the first die 250 and the third set of conductors 270. Those conductors 350 that are connected to conductors 270 may be used for signal and power/ground interconnect. Those conductors 350 that contact the die 250 may not be used electrically (e.g. they may be “no connects” in the redistribution layer 320), but they may provide a low thermal resistance path for heat from the die 250.

[0038] Each of the conductors 240, 260, 270, 350, and 420 may be formed in any desired fashion. For example, in an embodiment, the conductors 260 and 420 may be controlled-collapse chip connect (C4) bumps deposited as part of the manufacturing process for the die 250 and 410. The conductors 240, 270, and 350 may be ball grid array (BGA) solder balls. Other conductors may be used as desired.

[0039] In some embodiments, the electronic memory module may include at least one second die electrically connected to the second surface of the third substrate. The second die may electrically connect the second surface using a fifth set of electrical conductors such that the second die is directly bonded to the third substrate.

[0040] In some embodiments, the method may include forming a semiconductor device package assembly. FIG. 4 depicts an embodiment of flow chart representing a method of forming at least a portion of a thermally enhanced package on package format. FIGS. 5A-D depict an embodiment of an assembly of several thermally enhanced package on package formats 200. The method may include forming 500 a first substrate. The method may include electrically connecting the semiconductor device package 510. The method may include directly bonding 520 a first die to the first substrate using a second set of electrical conductors. The method may include electrically connecting 530 the second set of electrical conductors to the first set of electrical conductors. The method may include electrically connecting 540 a third set of electrical conductors coupled the first substrate to the first set of electrical conductors. The method may include directly bonding 550 a second substrate 280 to the first die 250 (e.g., as depicted in FIG. 5A). The method may include directly bonding 560 a third substrate 320 forming at least a portion of an electronic memory module 310 to the second substrate 280 (e.g., as depicted in FIG. 5B). The method may include applying 570 a thermally conductive material directly to a second surface of the electronic memory module. The method may include directly bonding 580 a first side of a heat spreader to the thermally conductive material, wherein the heat spreader comprises a second side substantially opposite the first side. The method may include transferring 590 heat from the first die and the electronic memory module through the heat spreader from the first side to the second side of the heat spreader.

[0041] In some embodiments, a method may include directly bonding the third substrate 320 to the first die 250 using fourth set of electric conductors 350 (e.g., as depicted in FIG. 5C-D).

EMI Shielding

[0042] In order to address problems associated with electromagnetic interference discussed herein, in some embodiments, an EMI shield is applied (e.g., directly) to a PoP. Applying a shield directly to a wafer level fan-out PoP may result in extremely thin SOC and memory packages.

[0043] FIG. 6 depicts an embodiment of a package on package format 200 including two redistribution layers (e.g., 280 and 320) and an EMI shield 600. At least some of the electrical conductors are not depicted for the sake of clarity. In some embodiments, a semiconductor device package assembly 200 may include a first substrate 210. The first substrate may include a first surface 220 and a second surface 230 substantially opposite of the first surface. In some embodiments, the first surface 220 may be equivalent to a lower surface of the semiconductor device package assembly. The first substrate may include a first set of electrical conductors 240 coupled to the first surface. The first set of electrical conductors may function to electrically connect the semiconductor device package assembly.

[0044] In some embodiments, the semiconductor device package assembly may include at least one electrical conductor 610. In some embodiments, the electrical conductor may be electrically coupled such that during use the electrical conductor is electrically grounded. In some embodiments, the electrical conductor may be electrically coupled to the first substrate such that during use the electrical conductor is electrically grounded. In some embodiments, the electrical conductor may be such that at least one of the electrical conductors exposes through a perimeter surface 620 of package format 200. In some embodiments, only a small portion of the electrical conductor 610 may exposed through the perimeter surface 620 of package format 200. In some embodiments, almost an entire length of the electrical conductor 610 may exposed through the perimeter surface of the package 200.

[0045] In some embodiments, the exposed electrical conductor may include a copper elongated member or post.

[0046] In some embodiments, the semiconductor device package assembly may include a first die 250. The first die may be electrically connected to the second surface 230 of the first substrate 210 using a second set of electrical conductors 260. In some embodiments, the semiconductor device package assembly 200 may include an electronic memory module 410 coupled to the first die 250.

[0047] In some embodiments, the semiconductor device package assembly may include a shield 600. Electromagnetic shielding reduces or inhibits the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. The shielding may reduce the coupling of, for example, radio waves, electromagnetic fields and electrostatic fields.

[0048] The amount of reduction depends upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest. The amount of reduction depends upon the size, shape and orientation of apertures in a shield to an incident electromagnetic field. Any holes in the shield or mesh must be significantly smaller than the wavelength of the radiation that is being kept out (or the shield will not effectively approximate an unbroken conducting surface).

[0049] In some embodiments, the shield comprises an electrically conductive material. The shield may be applied to an upper surface of the semiconductor device package assembly. The shield may be electrically coupled to at least one of the exposed electrical conductors. The shield may function to inhibit, during use, electromagnetic interference. In some embodiments, the exposed electrical conductor electrically grounds the shield. In some embodiments, the exposed electrical conductor is electrically coupled such that the shield is electrically grounded during use.

[0050] Typical materials used for electromagnetic shielding may include copper or nickel, in the form of very small particulates. The material may be sprayed on to the package assembly and, once dry, produces a continuous conductive layer of metal. The shielding layer may include aluminum, ferrite, carbonyl iron, stainless steel, nickel silver, low-carbon steel, silicon-iron steel, foil, conductive resin, and other metals and composites capable of blocking or absorbing EMI, RFI, and other inter-device interference. In some embodiments, the shield may include a non-metal material such as carbon-black or aluminum flake to reduce the effects of EMI and RFI. The shield may be deposited using an electrolytic plating, electroless plating, sputtering, physical vapor deposition (“PVD”), chemical vapor deposition (“CVD”), or other suitable metal deposition process. For non-metal materials, the shield may be applied by lamination, spraying, or painting.

[0051] In some embodiments, the shield 600 comprises a plurality of layers 600a-b (e.g., as depicted in FIG. 6). The shield comprises a plurality of layers comprising a permeability difference between adjacent layers. Layering using different materials with different properties may allow the shield to inhibit interference resulting from different wavelengths of radiation.

[0052] In some embodiments, the semiconductor device package assembly may include a thermally conductive material 360 directly applied to a second surface 370 of the electronic memory module. The semiconductor device package assembly may include a heat spreader 380 including a first side 390 and a second side 400 substantially opposite the first side. The first side may be directly bonded to the thermally conductive material. The heat spreader may function to transfer heat from the first die and the electronic memory module through the heat spreader from the first side to the second side. FIG. 7 depicts an embodiment of a thermally enhanced package on package format 200 including two redistribution layers (e.g., 280 and 320), a heat spreader 380, and an EMI shield 600. At least some of the electrical conductors are not depicted for the sake of clarity. FIG. 8 depicts an embodiment of a thermally enhanced package on package format including one redistribution layer and an EMI shield. At least some of the electrical conductors are not depicted for the sake of clarity.

[0053] In some embodiments, the heat spreader 380 may be at least partially connected to shield 600. In many instances heat spreaders are formed from metals which are not only thermally conductive but electrically conductive as well. As such the heat spreader may be connected to the shield such that the heat spreader may function to enhance the EMI shielding. If the heat spreader is at least electrically coupled to the shield (or at least grounded in some other manner) then (depending upon what the heat spreader is formed from) the heat spreader may function as an EMI shield as well further enhancing the EMI shielding performance.

[0054] In some embodiments, shielded wafer level fan-out packages may be manufactured in a number of manner. FIGS. 9A-D depict an embodiment of an assembly of several package on package formats including EMI shields. FIG. 9A depicts a set of packages manufactured at the same time as a single unit 630. This may be done in order to decrease costs of manufacture. Multiple first dies 250 may be assembled together on a single substrate 210 with a first redistribution layer 280. Units 630 may include electrical conductors 270. In some embodiments, units 630 may be formed without

[0055] FIG. 9B depicts a set of packages manufactured at the same time as a single unit 630 after second dies 410 mounted on second redistribution layers 320 are coupled to unit 630. Second dies 410 may be mounted in a fan-out configuration in order to reduce the profile or Z height. In some embodiments, second dies 410 may form an electronic memory module. In some embodiments, units 630 may be formed without first redistribution layer 280 and second dies 410 mounted on second redistribution layers 320 may be coupled to first dies 250.

[0056] FIG. 9C depicts a set of packages 200 which have been singulated from a single unit 630. Singulation (e.g., saw singulation) cuts a large set of packages into individual packages 200. Singulation may be conducted such that electrical conductors 270 are cut forming electrical conductors 610 which are at least partially exposed along the perimeter surface 620 of package 200. Electrical conductors 610 may be electrically coupled, for example, to substrate 210 such that the exposed electrical conductors are grounded during use.

[0057] FIG. 9D depicts a set of packages 200 which have been after a shield 600 has been applied the packages 200. The shield may inhibit interference (e.g., electromagnetic interference). The shield may include one or more layers. The shield may be deposited using electrolytic plating, electroless plating, sputtering, spray, physical vapor deposition (“PVD”), chemical vapor deposition (“CVD”), or other suitable metal deposition process. For non-metal materials, the shield may be applied by lamination, spraying, or painting. In some embodiments, the shield may be electrically coupled (e.g., grounded) during use. The shield may be electrically coupled to exposed electrical conductors 610. The shield may form a substantially continuous layer over the package and be coupled to the exposed electrical conductors 610 through direct contact.

[0058] Numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to embrace all such variations and modifications.