Patent Publication Number: US-2023138349-A1

Title: Embedded packaging structure

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This non-provisional application claims priority under 35 U.S.C. § 119(a) on Pat. Application No(s). 63/273,597 filed in U.S. on 2021/10/29, the entire contents of which are hereby incorporated by reference. 
    
    
     BACKGROUND 
     1. Technical Field 
     This present disclosure relates to a packaging structure for electronic component. 
     2. Related Art 
     With the improvement of integrated circuit fabrication technology, some novel packaging methods have been developed in the related technology for packaging the integrated circuit. Recently, embedded packaging technology, which was previously applied to circuit board manufacturing, has been noticed and widely applied to system-in-package (SIP) of power semiconductor components. Since wearable electronic devices and portable devices are the future trend of electronic products, the embedded packaging technology is considered having a certain research value due to its advantages of low cost and small packaging size. An embedded packaging structure generally consists of a semiconductor die embedded in a dielectric material, and a signal trace (circuit for signal transmission) outside the dielectric material. The electrical connection between the semiconductor die and the signal trace is accomplished by a metallic conductive via. Usually, a blind hole is formed in the dielectric material by a laser drilling process to expose the semiconductor die for electrical connection, and the blind hole is filled with metal to form a metallic conductive via contacting a contact point of the semiconductor die. 
     A high power laser source used in the laser drilling process may strike a metal layer serving as the contact point of the semiconductor die or even a main body of the die Therefore, the fabrication of embedded packaging structure includes a step of forming a barrier layer (or called stop layer) for laser drilling above the metal layer. 
     SUMMARY 
     According to one embodiment of the present disclosure, an embedded packaging structure includes a die, a sintered metal layer, an encapsulation layer and a conductive via. The die includes a metallic bonding layer. sintered metal layer is bonded to the metallic bonding layer. The encapsulation layer covers the die. The conductive via is provided in a blind hole of the encapsulation layer, and the conductive via is electrically connected with the metallic bonding layer through the sintered metal layer. 
     According to another embodiment of the present disclosure, an embedded packaging structure includes a die, a sintered metal layer, a copper foil, an encapsulation layer and a conductive via. The die includes a metallic bonding layer. The sintered metal layer is bonded to the metallic bonding layer. The copper foil is bonded to the sintered metal layer, and the sintered metal layer is provided between the metallic bonding layer and the copper foil. The encapsulation layer covers the die. The conductive via is provided in a blind hole of the encapsulation layer, and the conductive via is electrically connected with the metallic bonding layer through the copper foil and the sintered metal layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic view of an embedded packaging structure according to one embodiment of the present disclosure; 
         FIG.  2    is a partially enlarged view of the embedded packaging structure in  FIG.  1   ; 
         FIG.  3    is a scanning electron microscope (SEM) image of a sintered metal layer according to one embodiment of the present disclosure; 
         FIGS.  4  through  7    are schematic views of fabricating the embedded packaging structure in  FIG.  1   ; 
         FIG.  8    is a schematic view of an embedded packaging structure according to another embodiment of the present disclosure; and 
         FIG.  9    is a partially enlarged view of the embedded packaging structure in  FIG.  8   . 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. According to the description, claims and the drawings disclosed in the specification, one skilled in the art may easily understand the concepts and features of the present disclosure. The following embodiments further illustrate various aspects of the present disclosure, but are not meant to limit the scope of the present disclosure. 
     Please refer to  FIG.  1    and  FIG.  2   .  FIG.  1    is a schematic view of an embedded packaging structure according to one embodiment of the present disclosure.  FIG.  2    is a partially enlarged view of the embedded packaging structure in  FIG.  1   . In this embodiment, an embedded packaging structure  1   a  includes a substrate  10 , a die  20 , a sintered metal layer  30 , an encapsulation layer  40 , a conductive via  50 , a signal trace layer  60  and a plating through hole (PTH)  70 . The substrate  10  of the embedded packaging structure  1   a  may be bonded to a printed circuit board (not shown in the drawings). 
     The substrate  10 , for example but not limited to, is a metal substrate made of aluminum (Al), lead (Pb) or copper (Cu). The die  20  includes a main body  210  and a metallic bonding layer  220 . The die  20 , for example but not limited to, is a power semiconductor component, a radio frequency (RF) component, an insulated gate bipolar transistor (IGBT), a power diode or other electronic components containing semiconductor material (e.g. Si, GaAs, SiC, GaN, Ga 2 O 3 ), and the die  20  is bonded to the substrate  10 . The metallic bonding layer  220  may be a contact pad of the die  20 , and the main body  210  may be a portion of the die  20  containing silicon-based semiconductor or a portion of the die  20  except the metallic bonding layer  220 . 
     The metallic bonding layer  220  of the die  20  is provided on the surface of main body  210 . In detail, the metallic bonding layer  220  is formed on the top surface  212  of the main body  210 . In other words, one side of the die  20  is bonded to the substrate  10 , and a metallic bonding layer  220  is provided at the opposite side of the die  20 . The metallic bonding layer  220  may include a metallic layer contain aluminum-copper or aluminum-silicon alloy, and another layer or a stack of sub-layers which is formed on the metallic layer. The stack of sub-layers may include Cu sub-layer, Cu—Au sub-layer, Ni—Pd—Au sub-layer or Ni—Ag sub-layer, and gold (Au) or silver (Ag) is taken as the outermost sub-layer to protect the metallic bonding layer from oxidation. The die  20  may further include a lower metallic bonding layer  230  contacting the bottom surface  211  of the main body  210  and is bonded to the substrate  10  through a metallic adhesive layer  21 . The metallic adhesive layer  21  may be a solder or a sintered metal such as sintered silver, sintered copper, sintered copper with sintered silver sintered Cu—Ag and sintered nickel. 
     The sintered metal layer  30  is bonded to the metallic bonding layer  220  of the die  20 . The sintered metal layer  30  includes solid metal formed by fusing raw materials in a heating process or a pressurization process. More specifically, the sintered metal layer  30  may include sintered copper, sintered silver or a combination thereof. The sintered metal layer  30  may have physical properties suitable for transmitting signals for telecommunications; for example, the thickness of the sintered metal layer  30  may be equal to or less than 60.0 µm, the thickness of the sintered metal layer  30  may be from 10.0 µm to 30.0 µm, the thermal conductivity of the sintered metal layer  30  may be equal to or greater than 190.0 W/m·K, and the electrical resistivity the sintered metal layer  30  may be from 2.5 × 10 -8  Ω-m to 8.0 × 10 -8  Ω·m.  FIG.  3    is a SEM image of a sintered metal layer according to one embodiment of the present disclosure, wherein the sintered metal layer  30  includes a submicron porous structure. 
     The encapsulation layer  40  covers the die  20 . In detail, the encapsulation layer  40  is formed on the substrate  10  and covers the die  20  and the sintered metal layer  30 . The encapsulation layer  40  may include one or more dielectric layers, and the dielectric layer may be a silicon oxide layer or a nitrogen oxide layer. 
     The conductive via  50  is provided in a blind hole  410  of the encapsulation layer  40 . Specifically, the blind hole  410  may be formed in the encapsulation layer  40  by using a laser drilling process to remove part of the encapsulation layer  40  and thereby obtain the blind hole  410  exposing the sintered metal layer  30 , and then the conductive via  50  is formed in the blind hole  410 . The conductive via  50  is electrically connected with the metallic bonding layer  220  of the die  20  through the sintered metal layer  30 . 
     The signal trace layer  60  is provided on the encapsulation layer  40  and the conductive via  50 , and the conductive via  50  is electrically connected with the signal trace layer  60 . The signal trace layer  60  may be made of the same metal material as the substrate  10 . In addition, the signal trace layer  60  may be covered with electrically insulated material (not shown in the drawings) to ensure a safe design for the prevention of leakage current. 
     The PTH  70  extends through the encapsulation layer  40 . A metal film is coated on the inner wall of the PTH  70  to connect the signal trace layer  60  with the substrate  10 , and this metal film may be made of the same metal material as the substrate  10  and the signal trace layer  60 . 
     The following describes a method of fabricating the embedded packaging structure  1   a .  FIG.  4    through  FIG.  7    are schematic views of fabricating the embedded packaging structure in  FIG.  1   . As shown in  FIG.  4   , the substrate  10 , the die  20  mounted on the top surface  110  of the substrate  10 , and the sintered metal layer  30  bonded to the metallic bonding layer  220  of the die  20  are provided, wherein the sintered metal layer  30  serves as a barrier layer for the subsequent laser drilling process. In detail, a wafer which has been processed to form integrated circuits may be cut by a diamond cutter to obtain one or more dies  20 . The die  20  is then bonded to the top surface  110  of substrate  10 , and the sintered metal layer  30  is formed on the die  20 . The bonding of the die  20  to the substrate  10 , for example, is referred to that the lower metallic bonding layer  230  on the bottom surface  211  of the main body  210  of the die  20  is bonded to the top surface  110  of the substrate  10  by a metallic adhesive layer  21 . 
     The sintered metal layer  30  may be formed on the die  20  in several ways. In one way, a sintered metal is firstly obtained by a conventional sintering process and then shaped into a sheet; next, the sintered metal sheet is placed on the metallic bonding layer  220  of the die  20  and thermocompressed at a temperature of 220° C. to 300° C. to form the sintered metal layer  30  on the die  20 . In another way, a slurry containing metal powder is spread on the metallic bonding layer  220 , and then thermocompressed at a temperature of 220° C. to 300° C. to form the sintered metal layer  30  bonded to the metallic bonding layer  220 . As to the two exemplary ways, the sintered metal sheet or the slurry containing metal powder is provided at the location where the metallic bonding layer  220  exists, and the sintered metal layer  30  has substantially the same pattern area as or smaller pattern area than the corresponding metallic bonding layer  220 ; that is, in a top view, it may be observed that the pattern of the sintered metal layer  30  has substantially the same shape as that of the metallic bonding layer  220 , and an area of the pattern of the sintered metal layer  30  is equal to or slightly smaller than that of the metallic bonding layer  220 . 
     As shown in  FIG.  5   , the encapsulation layer  40  is formed on the substrate  10  and covers the die  20 , the sintered metal layer  30  and the substrate  10 . A metal film  61  is formed on the encapsulation layer  40  as a part for forming the signal trace layer  60  in a subsequent step. The encapsulation layer  40  may be configured by chemical vapor deposition epoxy resin, glass fibre epoxy resin or a stack thereof, and the metal film  61  may be formed by copper foil lamination, sputtering or electroplating. 
     As shown in  FIG.  6   , the blind hole  410  and the PTH  70  are formed in the encapsulation layer  40 . In detail, in a specific region, the encapsulation layer  40  and the metal film  61  may be removed by laser drilling to form the blind hole  410 ; in another region, the substrate, the encapsulation layer  40  and the metal film  61  may be removed by mechanical drilling to form the PTH  70 . The blind hole  410  exposes the sintered metal layer  30 . The sintered metal layer  30  features good electrical conductivity and thus has less influence on signal transmission. In addition, the sintered metal layer  30  also features high thermal conductivity and high melting point, such that a laser beam is difficult to breakthrough the sintered metal layer  30 , and the heat generated by laser strike can be quickly transferred and does not accumulate nearby the metallic bonding layer  220  of the die  20 . Thus, it is helpful to increase the service life of the die  20 . 
     As shown in  FIG.  7   , the conductive via  50  is formed in the blind hole  410 , and a metal film  71  is formed on the inner wall of the PTH  70 . In detail, a metal layer, such as copper layer, titanium layer, tungsten layer and so on, may be deposited on the inner wall of the PTH  70  by electroplating to form the conductive via  50  and the metal film  71 . The metal film  71  is also formed on the metal film  61  in  FIG.  6   , and both of the metal films  61  and  71  may be jointly patterned to form the signal trace layer  60 . The patterning of the metal films can be accomplished by photolithography and etching processes. In this embodiment, compared to a conventional barrier layer containing electroplated or electroless metal, the sintered metal layer  30  including submicron porous structure is advantageous to increase a contact area between the conductive via  50  containing electroplated copper and the sintered metal layer  30 , thereby improving the bonding strength and the reliability of the packaging structure. 
     The embedded packaging structure disclosed therein may include a copper foil bonded to the sintered metal layer. Please refer to  FIG.  8    and  FIG.  9   .  FIG.  8    is a schematic view of an embedded packaging structure according to another embodiment of the present disclosure, and  FIG.  9    is a partially enlarged view of the embedded packaging structure in  FIG.  8   . In this embodiment, an embedded packaging structure  1   b  includes a substrate  10 , a die  20 , a sintered metal layer  30 , an encapsulation layer  40 , a conductive via  50 , a signal trace layer  60  and a PTH  70 . Any specific configuration of the aforementioned elements can be referred to the previous description related to the embedded packaging structure  1   a   FIG.  1   , and the detail description will be omitted hereafter. 
     The embedded packaging structure  1   b  further includes a copper foil  80 . The copper foil  80  is bonded to the top side of the sintered metal layer  30 , and a thickness of the copper foil  80  is from 50.0 µm to 100.0 µm. The sintered metal layer  30  is provided between the metallic bonding layer  220  of the die  20  and the copper foil  80 , and the copper foil  80  contacts the conductive via  50 . An exemplary method of bonding the copper foil  80  to the sintered metal layer  30  is that the copper foil  80  is attached to a sintered metal sheet (sintered metal layer  30 ), and bonded to the sintered metal sheet by thermocompression; or, the copper foil  80  is placed on a slurry containing metal powder (sintered metal layer  30 ), bonded to the sintered metal layer  30  by thermocompression. The double-layer structure including the sintered metal layer  30  and the copper foil  80  serves as a barrier layer for laser drilling to prevent heat damage due to laser strike from the die  20 . 
     According to the present disclosure, the embedded packaging structure includes the sintered metal layer bonded to the metallic bonding layer of the die. The sintered metal layer features good thermal conductivity and electrical conductivity and thus can be taken as a barrier layer for laser drilling in the fabrication of the embedded packaging structure. Since the sintered metal layer is taken as the barrier layer, the barrier layer can be formed on a die after the wafer is cut into multiple dies. Compared to a conventional barrier layer which is formed to cover all dies before wafer dicing, the sintered metal layer on the die enjoys less internal stress and is less likely to warp and break or even peel off. 
     Moreover, the sintered metal layer includes submicron porous structure, such that it is advantageous to increase a contact area between the conductive via and the sintered metal layer, thereby improving the bonding strength and the reliability of the packaging structure. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the present disclosure. It is intended that the specification and examples be considered as exemplary embodiments only, with a scope of the disclosure being indicated by the following claims and their equivalents.