The present invention relates in general to semiconductor devices and, more particularly, to semiconductor packages with electromagnetic interference (EMI) shielding formed over an exposed die backside.
Semiconductor devices are commonly found in modern electronic products. Semiconductor devices perform a wide range of functions such as signal processing, high-speed calculations, transmitting and receiving electromagnetic signals, controlling electronic devices, transforming sunlight to electricity, and creating visual images for television displays. Semiconductor devices are found in the fields of communications, power conversion, networks, computers, entertainment, and consumer products. Semiconductor devices are also found in military applications, aviation, automotive, industrial controllers, and office equipment.
Semiconductor devices are often susceptible to electromagnetic interference (EMI), radio frequency interference (RFI), harmonic distortion, or other inter-device interference, such as capacitive, inductive, or conductive coupling, also known as cross-talk, which can interfere with their operation. The high-speed switching of digital circuits also generates interference.
Conductive layers are commonly formed over semiconductor packages to shield electronic parts within the package from EMI and other interference. Shielding layers absorb EMI before the signals can hit semiconductor die and discrete components within the package, which might otherwise cause malfunction of the device. Shielding layers are also formed over packages with components that are expected to generate EMI to protect nearby devices from malfunction.
Many factors can make proper EMI shielding difficult. Many prior art shielding methods do not allow sufficient thermal dissipation and are unable to produce a semiconductor package with a low enough profile to meet the demands of today's consumers. Therefore, a need exists for improvements to EMI shielding and manufacturing methods.
The present invention is described in one or more embodiments in the following description with reference to the figures, in which like numerals represent the same or similar elements. While the invention is described in terms of the best mode for achieving the invention's objectives, it will be appreciated by those skilled in the art that it is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims and their equivalents as supported by the following disclosure and drawings. The term “semiconductor die” as used herein refers to both the singular and plural form, and, accordingly, can refer to both a single semiconductor device and multiple semiconductor devices.
Semiconductor devices are generally manufactured using two complex manufacturing processes: front-end manufacturing and back-end manufacturing. Front-end manufacturing involves the formation of a plurality of die on the surface of a semiconductor wafer. Each die on the wafer contains active and passive electrical components, which are electrically connected to form functional electrical circuits. Active electrical components, such as transistors and diodes, have the ability to control the flow of electrical current. Passive electrical components, such as capacitors, inductors, and resistors, create a relationship between voltage and current necessary to perform electrical circuit functions.
Back-end manufacturing refers to cutting or singulating the finished wafer into the individual semiconductor die and packaging the semiconductor die for structural support, electrical interconnect, and environmental isolation. To singulate the semiconductor die, the wafer is scored and broken along non-functional regions of the wafer called saw streets or scribes. The wafer is singulated using a laser cutting tool or saw blade. After singulation, the individual semiconductor die are mounted to a package substrate that includes pins or contact pads for interconnection with other system components. Contact pads formed over the semiconductor die are then connected to contact pads within the package. The electrical connections can be made with conductive layers, bumps, stud bumps, conductive paste, or wirebonds. An encapsulant or other molding material is deposited over the package to provide physical support and electrical isolation. The finished package is then inserted into an electrical system and the functionality of the semiconductor device is made available to the other system components.
An electrically conductive layer 112 is formed over active surface 110 using PVD, CVD, electrolytic plating, electroless plating, or other suitable metal deposition process. Conductive layer 112 can be one or more layers of aluminum (Al), copper (Cu), tin (Sn), nickel (Ni), gold (Au), silver (Ag), or other suitable electrically conductive material. Conductive layer 112 operates as contact pads electrically connected to the circuits of active surface 110 and may include conductive traces for horizontal routing.
An electrically conductive bump material is deposited over conductive layer 112 using an evaporation, electrolytic plating, electroless plating, ball drop, or screen printing process. The bump material can be Al, Sn, Ni, Au, Ag, lead (Pb), bismuth (Bi), Cu, solder, and combinations thereof, with an optional flux solution. For example, the bump material can be eutectic Sn/Pb, high-lead solder, or lead-free solder. The bump material is bonded to conductive layer 112 using a suitable attachment or bonding process. In some embodiments, the bump material is reflowed by heating the material above its melting point to form balls or bumps 114. In one embodiment, bump 114 is formed over an under bump metallization (UBM) having a wetting layer, a barrier layer, and an adhesion layer. Bump 114 can also be compression bonded or thermocompression bonded to conductive layer 112. Bump 114 represents one type of interconnect structure that can be formed over conductive layer 112. The interconnect structure can also use bond wires, conductive paste, stud bump, micro bump, or other electrical interconnect.
In
Portions of conductive layers 122 can be electrically common or electrically isolated depending on the design and function of semiconductor die 104. Insulating layer 124 contains one or more layers of silicon dioxide (SiO2), silicon nitride (Si3N4), silicon oxynitride (SiON), tantalum pentoxide (Ta2O5), aluminum oxide (Al2O3), solder resist, polyimide, benzocyclobutene (BCB), polybenzoxazoles (PBO), and other material having similar insulating and structural properties. Insulating layer 124 provides isolation between conductive layers 122. Substrate 120 further includes core material 130, such as glass fabric, to reinforce the substrate and reduce warpage.
In
In
Encapsulant 140 is deposited with back surface 108 of semiconductor die 104 exposed from the encapsulant. A back surface of encapsulant 140 is coplanar with back surface 108 of semiconductor die 104. In some embodiments, encapsulant 140 is deposited with a mold plate in contact with back surface 108, using film assisted molding, or by another suitable molding process to keep the top of semiconductor die 104 free from encapsulant 140. In other embodiments, encapsulant 140 is deposited covering semiconductor die 104 and then backgrinded to expose back surface 108.
In
A conductive material is deposited over packages 160 to form conformal shielding layer 162. Shielding layer 162 is formed by any suitable metal deposition technique, e.g., chemical vapor deposition, physical vapor deposition, other sputtering methods, spraying, or plating. Shielding layer 162 completely covers the exposed top and side surfaces of semiconductor die 104, encapsulant 140, and substrate 120. The singulation of the panel of packages 160 before forming shielding layer 162 exposes the side surfaces of each package so that the shielding layer is formed down the side surfaces to contact substrate 120. Shielding layer 162 physically and electrically contacts conductive layers 122, which can be used to connect the shielding layer to a ground voltage or other reference voltage node through a bump 142. Shielding layer 160 directly contacts back surface 108 of semiconductor die 104, which improves heat dissipation.
Trenches 200 are formed by deep reactive ion etching (DRIE), chemical etching, saw blades, or another suitable process. Trenches 200 only extend partially through wafer 100 so that semiconductor die 104 remain physically connected by semiconductor material 102 within saw streets 106. In other embodiments, trenches 200 extend completely through wafer 100 to singulate semiconductor die 104, and the relative positions of the semiconductor die are maintained by an adhesive material on a carrier.
In
In
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Copper layer 212 can remain as the top layer of shielding layer 162 as shown in
Alternatively, protection layer 214 can be a tin or lead based pre-soldering layer. Pre-solder can be applied using an easy solder paste printing method. In one embodiment, a tin-silver-copper (SnAgCu or SAC) solder paste or another tin-based material is used. Pre-solder is applied in embodiments where a heatsink or other component will subsequently be soldered onto the top of the shielding layer as shown below in
In
Electronic device 240 can be a stand-alone system that uses the semiconductor packages to perform one or more electrical functions. Alternatively, electronic device 240 can be a subcomponent of a larger system. For example, electronic device 240 can be part of a tablet computer, cellular phone, digital camera, communication system, or other electronic device. Electronic device 240 can also be a graphics card, network interface card, or another signal processing card that is inserted into a computer. The semiconductor packages can include microprocessors, memories, ASICs, logic circuits, analog circuits, RF circuits, discrete active or passive devices, or other semiconductor die or electrical components.
In
In some embodiments, a semiconductor device has two packaging levels. First level packaging is a technique for mechanically and electrically attaching the semiconductor die to an intermediate substrate. Second level packaging involves mechanically and electrically attaching the intermediate substrate to PCB 242. In other embodiments, a semiconductor device may only have the first level packaging where the die is mechanically and electrically mounted directly to PCB 242.
For the purpose of illustration, several types of first level packaging, including bond wire package 246 and flipchip 248, are shown on PCB 242. Additionally, several types of second level packaging, including ball grid array (BGA) 250, bump chip carrier (BCC) 252, land grid array (LGA) 256, multi-chip module (MCM) 258, quad flat non-leaded package (QFN) 260, quad flat package 262, and embedded wafer level ball grid array (eWLB) 264 are shown mounted on PCB 242 along with package 180. Conductive traces 244 electrically couple the various packages and components disposed on PCB 242 to package 180, giving use of the components within the package to other components on the PCB.
Depending upon the system requirements, any combination of semiconductor packages, configured with any combination of first and second level packaging styles, as well as other electronic components, can be connected to PCB 242. In some embodiments, electronic device 240 includes a single attached semiconductor package, while other embodiments call for multiple interconnected packages. By combining one or more semiconductor packages over a single substrate, manufacturers can incorporate pre-made components into electronic devices and systems. Because the semiconductor packages include sophisticated functionality, electronic devices can be manufactured using less expensive components and a streamlined manufacturing process. The resulting devices are less likely to fail and less expensive to manufacture resulting in a lower cost for consumers.
While one or more embodiments of the present invention have been illustrated in detail, the skilled artisan will appreciate that modifications and adaptations to those embodiments may be made without departing from the scope of the present invention as set forth in the following claims.
The present application is a continuation of U.S. patent application Ser. No. 17/008,997, now U.S. Pat. No. 11,342,278, filed Sep. 1, 2020, which is a continuation of U.S. patent application Ser. No. 16/529,486, now U.S. Pat. No. 10,804,217, filed Aug. 1, 2019, which claims the benefit of U.S. Provisional Application No. 62/717,415, filed Aug. 10, 2018, which applications are incorporated herein by reference.
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“EMI Shielding for Die Backside Exposed Flip Chip Package”, IP.COM, Jun. 12, 2017. |
Number | Date | Country | |
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20220246541 A1 | Aug 2022 | US |
Number | Date | Country | |
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Number | Date | Country | |
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Parent | 17008997 | Sep 2020 | US |
Child | 17660093 | US | |
Parent | 16529486 | Aug 2019 | US |
Child | 17008997 | US |