Patent Publication Number: US-11387533-B2

Title: Semiconductor package with plastic waveguide

Description:
BACKGROUND 
     Dielectric Wave Guide (DWG) and Polymer Microwave Fiber (PMF) have been proposed to transport Radio Frequency (RF) signals over plastic. 
     A concept disclosed herein is to replace copper wire transporting signals in the gigabit/second data rate range with plastic waveguide. Typical applications include camera interfaces and Gigabit Automotive Ethernet. With increasing frequency, RF signals inside the plastic waveguide concentrate, isolation distance reduces, and bending losses decay, making this concept attractive for high frequency transmissions. 
     A critical performance parameter for high frequency components in the higher gigahertz range is output power loss. Therefore, it is desired to transport high frequency signals outside of a chip and/or package with low power loss transitions to drive and control a coupled plastic waveguide. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  illustrate semiconductor devices having Integrated Circuit (IC) packages with longitudinal waveguide at package side and embedded vertical antenna, in accordance with aspects of the disclosure. 
         FIG. 2  illustrates a semiconductor device having an IC package with longitudinal waveguide at package side and integrated MicroElectroMechanical System (MEMS) waveguide, in accordance with aspects of the disclosure. 
         FIG. 3  illustrates a semiconductor device having an IC package with longitudinal waveguide at package side and integrated waveguide cage, in accordance with aspects of the disclosure. 
         FIGS. 4A and 4B  illustrate semiconductor devices having an IC package with longitudinal waveguide at package top, in accordance with aspects of the disclosure. 
         FIG. 5  illustrates a semiconductor device having an IC package with vertical waveguide at package top, in accordance with aspects of the disclosure. 
         FIGS. 6A and 6B  illustrate semiconductor devices having an IC package with vertical waveguide and with Monolithic Microwave Integrated Circuit (MMIC) on top of MEMS elements, in accordance with aspects of the disclosure. 
         FIG. 7  illustrates a semiconductor device having an IC package with vertical waveguide at package top, and longitudinal waveguide at package side, in accordance with aspects of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure is directed to a high frequency Integrated Circuit (IC) package having attached thereto a plastic waveguide. The IC package includes a semiconductor chip and an embedded antenna configured as a feeding port to the plastic waveguide. 
     A waveguide is a device that transports Radio Frequency (RF) signals from one location to another. The waveguide acts as a high pass filter in that signal frequencies above a cutoff frequency pass through the waveguide, whereas signal frequencies below are attenuated. Waveguides are often used at microwave frequencies. 
       FIG. 1A  illustrates a semiconductor device  100 A having an Integrated Circuit (IC) package  110  with longitudinal waveguide  120  at package side and embedded vertical antenna  130 - 2 , in accordance with aspects of the disclosure. 
     The semiconductor device  100 A comprises an IC package  110 , a plastic waveguide  120 , an antenna  130 , a Printed Circuit Board (PCB)  140 , and Ball Grid Array (BGA) balls  150 . 
     The IC package  110  in this example is a Wafer Level Package (WLP). The IC package  110  in formed on the PCB  140  via an embedded Wafer Level Ball Grid (eWLB) comprising BGA balls  150 . The disclosure is not limited to the IC package being a WLP mounted via BGA balls  150 . The IC package  110  may be mounted to the PCB  140  using any suitable packaging technology. 
     The IC package  110  package comprises a semiconductor chip  112  encapsulated in a mold  110  for protection. The semiconductor chip  112  in this example is a Monolithic Microwave Integrated Circuit (MMIC), however, the disclosure is not limited in this respect. The semiconductor chip  112  may be any type of semiconductor chip suitable for the intended purpose. 
     Further, the semiconductor chip  112  in this example is in a face-down configuration, though the disclosure is not limited in this respect. The semiconductor chips described herein may be in a face-up or face-down orientation. The orientation of the semiconductor chip  112  is determined based on the orientation of the “face” of the chip  112 , which is the surface of the chip  112  that comprises the circuitry and BGA balls  150  for electrical connection to the PCB  140 . In a face-down orientation, the “face” of the chip  112  point in the direction of the PCB  140 , whereas in a face-up orientation, the face points away from the PCB  140 . 
     The antenna  130  comprises a planar duplex antenna using a Redistribution Layer (RDL)  130 - 1  (hereinafter, “RDL antenna”) and embedded vertical antenna (Embedded Z-Line (EZL)  130 - 2  (hereinafter, “EZL antenna”). The RDL antenna  130 - 1  is merely a galvanic interconnection through the RDL between the semiconductor chip  112  and the EZL antenna  130 - 2 . The RDL antenna  130 - 1  and the EZL antenna  130 - 2  may be comprised of copper, for example. 
     The RDL antenna  130 - 1  is coupled to the semiconductor chip  112  and configured to transport RF signals between the semiconductor chip  112  and the EZL antenna  130 - 2 . The EZL antenna  130 - 2  is configured to transport the RF signals between the RDL antenna  130 - 1  and the plastic waveguide  120 . The EZL antenna  130 - 2  is formed in a vertical direction, as illustrated in the expanded portion identified by the dotted oval. In this example, the EZL antenna  130 - 1  comprises a dipole antenna, though the disclosure is not limited in this respect. The dipole antenna may alternatively be any type of antenna as suitable for the intended purpose. The EZL antenna  130 - 2  radiates in two directions (towards and was from the plastic waveguide  120 ). An integrated reflector formed on the backside of the EZL antenna  130 - 2  reflects RF signals traveling in an undesired direction, as illustrated by the U-shaped, two-headed arrow. 
     The plastic waveguide  120  may be a Dielectric Wave Guide (DWG) or Polymer Microwave Fiber (PMF) having an inner plastic fiber  122  and an outer coating  124 . The plastic waveguide  120  is attached longitudinally at the end of the IC package  110 , and RF signals transport between the plastic waveguide  120  and the EZL antenna  130 - 2 . The plastic waveguide  120  is configured to transport RF signals between the EZL antenna  130 - 2  and outside of the IC package  110 . The plastic waveguide  120  in this example extends in a longitudinal direction from a side of the IC package  110 . The plastic waveguide  120  may have a supporting structure inside or outside of the IC package  110  to guide the plastic waveguide  120 . When the plastic waveguide  120  is integrated in the IC package  120 , a portion of the plastic waveguide  120  may project from the IC package  120 . The length “L” is zero if there is no plastic waveguide  120  projecting, or the length may be greater than zero (L&gt;0) if there is some plastic waveguide  120  projecting. Alternatively, the plastic waveguide  120  need not be integrated into the IC package  110 . The plastic waveguide  120  may instead be attached to the EZL antenna  130 - 2  at the end of the IC package  110 . Whether or not the plastic waveguide  120  is integrated into the IC package  110  often depends on which connection is preferable from a mechanical perspective. The chosen connection may also depend on output power loss resulting from the air gap  126 , for example. 
       FIG. 1B  illustrates a semiconductor device  100 B having an IC package  110  with longitudinal waveguide  120  at package side and EZL antenna  130 - 2 , in accordance with aspects of the disclosure. 
     The semiconductor device  100 B of  FIG. 1B  is similar to the semiconductor device  100 A of  FIG. 1A , except that the plastic waveguide  120  is not arranged at least partially within the IC package  110 . Instead, a spherical resonator  160  is arranged between the IC package  110  and the plastic waveguide  120  to bridge the air gap  126 . The spherical resonator  160  may comprise ceramic material or another material having a suitable dielectric constant. The spherical resonator  160  is sized such that it resonates with sufficient radiation performance in a preferred direction and radiation losses other directions. 
       FIG. 2  illustrates a semiconductor device  200  having an IC package  210  with longitudinal waveguide  220  at package side and integrated MicroElectroMechanical Systems (MEMS) waveguide  230 - 3 , in accordance with aspects of the disclosure. 
     Semiconductor device  200  comprises similar elements as semiconductor devices  100 A and  100 B of  FIGS. 1A and 1B , respectively, but the reference numerals begin with “2” rather than “1”. For the sake of brevity, descriptions of these elements are not repeated here. 
     The antenna  230  of semiconductor device  200  differs from the antenna  130  of semiconductor devices  100 A and  100 B in that in place of the EZL antenna  130 - 2  there is a MicroElectroMechanical Systems (MEMS) waveguide  230 - 2  formed by etching silicon and metallizing some or all of the silicon walls. The Si-MEMS waveguide  230 - 3  is configured to transport RF signals from the RDL antenna  230 - 1  to a center of the plastic waveguide  220 , as indicated by the arrows, and also in the reverse direction in the case of received RF signals. 
     The plastic waveguide  220  is attached to a side of the IC package  210 , and may have a supporting structure inside or outside of the IC package  210 . The plastic waveguide  220  in this example is attached to an outside of the IC package  210 . As a supporting structure, the plastic waveguide  220  may be fastened to the IC package  210  by a plastic waveguide fastener (not shown). 
     Optionally, the Si-MEMS waveguide  230 - 3  may project out of the mold  214  of the IC package  210  and be inserted into a hollow center of the plastic waveguide  220  providing a mechanical fixture of the plastic fiber  222 . This is relevant for a carrier wavelength requiring a plastic waveguide  220  of dimensions that are larger than the thickness of the Si-MEMS waveguide  230 - 3 . For a case in which the plastic fiber  222  has an asymmetrical aspect ratio (e.g., rectangular), such an arrangement can also be used to encode the correct adaptation to the Si-MEMS waveguide  230 - 3  to receive the intended polarization mode that preferably expands in the plastic fiber  222 . 
       FIG. 3  illustrates a semiconductor device  300  having an IC package  310  with longitudinal waveguide  320  at package side and integrated waveguide cage  330 - 4 , in accordance with aspects of the disclosure. 
     Semiconductor device  300  comprises similar elements as semiconductor devices  100 A,  1006 , and  200 , but the reference numerals begin with “3”. For the sake of brevity, descriptions of these elements are not repeated here. 
     The semiconductor device  300  differs from that of semiconductor devices  100 A and  100 B of  FIGS. 1A and 1B , respectively, in that in place of the EZL  130 - 2 , there is an embedded planar antenna  330 - 2  and an embedded waveguide cage  330 - 4  arranged between the RDL antenna (not shown) and the plastic waveguide  320 . 
     The plastic waveguide  320  is attached to a side of the IC package  310  next to the waveguide cage  330 - 4 . The plastic waveguide  320  may have a supporting structure inside or outside of the IC package  310 , as discussed above with respect to the other figures. 
     The embedded waveguide cage  330 - 4  comprises densely-spaced metallized vias to form walls. Realizing walls using vias is an alternative to plane metallization. The ceiling and floor of the waveguide cage  330 - 4  are metallized. The RF signals more or less reflect within the waveguide cage  330 - 4  until the RF signals transport through the plastic waveguide  320 , or in the case of receiving RF signals, transport to the IC chip  312 . 
       FIG. 4A  illustrates a semiconductor device  400 A having an IC package  410  with longitudinal plastic waveguide  420  at package top, in accordance with aspects of the disclosure. 
     Semiconductor device  400 A comprises similar elements as semiconductor devices  100 A,  100 B,  200 , and  300 , but the reference numerals begin with “4”. For the sake of brevity, descriptions of these elements are not repeated here. 
     The semiconductor chip  412  is embedded in a face-up configuration, so the RDL antenna  430 - 1  is formed on the top of the semiconductor chip  412  rather than on the bottom. RF signals are routed to the ball and board-side of the semiconductor chip  412  via an EZL/via bar  416 , which is not part of the antenna, but is instead for realizing a vertical interconnection. 
     The plastic waveguide  420  in this example is configured to extend from a top the IC package  410  in a longitudinal direction on top of the RDL antenna  430 - 1 . A triangular reflector  430 - 5  is configured to redirect RF signals from the RDL antenna  430 - 1  to the plastic waveguide  420 , as indicated by the arrows, and in the opposite direction in the case of received RF signals. The triangular reflector  430 - 5  redirects RF signals so that the plastic waveguide  420  need not be formed vertically, but instead longitudinally. The triangular reflector  430 - 5  may comprise a dielectric with a metallized hypotenuse surface. 
       FIG. 4B  illustrates a semiconductor device  400 B having an IC package  410  with longitudinal waveguide  420  at package top, in accordance with aspects of the disclosure. 
     Semiconductor device  400 B comprises similar elements as semiconductor device  400 A. For the sake of brevity, descriptions of these elements are not repeated here. 
     The semiconductor device  400 B of  FIG. 4B  is similar to the semiconductor device  400 A of  FIG. 4A , except that in place of the triangular reflector  430 - 5 , there is a spherical resonator  430 - 6 . The spherical resonator  430 - 6  does not have a metallized surface because the spherical resonator  430 - 6  functions to absorb energy rather than reflect the RF signal. The shape of the resonator concentrates energy, and since the plastic waveguide  420  touches the spherical resonator  430 - 6 , the energy can be transported through the plastic waveguide  420 , and in the opposite direction in the case of a received RF signal. 
       FIG. 5  illustrates a semiconductor device  500  having an IC package  510  with vertical waveguide  520  at package top, in accordance with aspects of the disclosure. 
     Semiconductor device  500  comprises similar elements as semiconductor devices  100 A,  100 B,  200 ,  300 ,  400 A, and  400 B, but the reference numerals begin with “5”. For the sake of brevity, descriptions of these elements are not repeated here. 
     The RF signal is transported from the semiconductor chip  512  to the RDL antenna  530 - 1 . To suppress signal losses, there may be reflectors (metallizations)  530 - 2  on the PCB/EZL to reflect RF signals, as indicated by the double-headed curved arrows. 
     The plastic waveguide  520  is attached to a top of the IC package  510  and configured to extend in a vertical direction. The plastic waveguide  520  may have a supporting structure (not shown) inside or outside of the IC package  510  to guide the plastic waveguide  520 . 
       FIG. 6A  illustrates a semiconductor device  600 A having an IC package  610  with vertical waveguide  620  and Monolithic Microwave Integrated Circuit (MMIC)  612 A formed on top of MEMS elements  670 , in accordance with aspects of the disclosure. 
     Semiconductor device  600 A comprises similar elements as semiconductor devices  100 A,  100 B,  200 ,  300 ,  400 A,  400 B, and  500 , but the reference numerals begin with “6”. For the sake of brevity, descriptions of these elements are not repeated here. 
     The semiconductor device  600 A comprises an IC package  610  with semiconductor chip  612 A, Si-MEMS elements  670  external to the IC package  610 , and a plastic waveguide  620 . The IC package  610  comprises an RDL antenna  630 - 1  and is attached to the Si-MEMS elements  670  via BGA balls  650 . 
     The Si-MEMS elements  670  is lined internally with planar metallizations, and may comprise elements such as tunable filters, tunable shifters, low loss couplers, etc. The Si-MEMS elements  670  also comprises two openings, a first opening  672  through which the RDL antenna  630 - 1  radiates, and a second opening  674  through which the plastic waveguide  620  radiates. The second opening  674  of the Si-MEMS elements  670  may have approximately a same diameter as the plastic waveguide  620 . 
     The plastic waveguide  620  may have a supporting structure outside of the second opening  674  of the Si-MEMS elements  670  to guide the plastic waveguide  620 . Optionally, the opening  672  of the Si MEMS elements  670  could be of the size of the plastic fiber  622 , and the plastic waveguide  620  could project into the opening  674 . For a case in which the plastic fiber  622  has an asymmetrical aspect ratio (e.g., rectangular), the shape of the opening  674  can also be used to encode a correct adaptation to the Si MEMS elements  670  to receive the intended polarization mode that preferably expands in the fiber  622 . 
     The RF signal radiates from the RDL antenna  630 - 1  through the opening  672  as shown by the arrows, reflects within the Si MEMS elements  670  until the RF signal passes through the second opening  674  and transports through the plastic wave guide  620  as shown by the arrows. Of course in the case of receiving an RF signal, the RF signals transport in the opposite direction, that is, through the plastic waveguide  620 , through the opening  674 , within the Si MEMs elements  670 , through the opening  672 , and into the IC package  610 . 
     The plastic waveguide  620  in this example is formed to project vertically from the top of the Si MEMS elements  670 . Alternatively, the plastic waveguide  620  may be formed to project longitudinally from a side of the Si MEMS elements  670 . An advantage of forming the plastic waveguide  620  on the top of the Si MEMS elements  670  is attachment with greater surface area is easier. 
       FIG. 6B  illustrates a semiconductor device  600 B having a semiconductor chip  612  and vertical waveguide  620  on top of MEMS elements  670 , in accordance with aspects of the disclosure. 
     Semiconductor device  600 B is similar to the semiconductor device  600 A of  FIG. 6A , except that rather than an IC package  610 , semiconductor device  600 B has a chip  612 B formed using flip-chip technology. The chip  612 B comprises an on-chip antenna  630 - 2  and is attached to the integrated MEMs elements  670  using stud bumps  652 . 
       FIG. 7  illustrates a semiconductor device  700  having an IC package with vertical waveguide  720 V at package top, and longitudinal waveguide  720 L at package side, in accordance with aspects of the disclosure. 
     Semiconductor device  700  comprises similar elements as semiconductor devices  100 A,  1006 ,  200 ,  300 ,  400 A,  400 B,  500 ,  600 A, and  600 B, but the reference numerals begin with “7”. For the sake of brevity, descriptions of these elements are not repeated here. 
     The plastic waveguide  720  comprises both a longitudinal plastic waveguide  720 L configured to extend in a longitudinal direction from a side of the IC package  710  and a vertical plastic waveguide  720 V configured to extend in a vertical direction from a top of the IC package  710 . 
     While specific examples for the semiconductor devices have been described herein, the disclosure is not limited to these examples. The disclosure covers semiconductor devices having any suitable combination of the describe features, for example, vertical versus longitudinal plastic waveguide, waveguide attached to top of IC package versus side or plastic waveguides attached to both top and side, triangular reflector versus spherical resonator, DWG versus PMF plastic waveguide, package versus flip-chip, plastic fiber at least partially embedded within the IC package or attached thereto, MEMS waveguide versus waveguide cage, MEMS elements formed separate from IC package, etc. 
     While the foregoing has been described in conjunction with exemplary aspects, it is understood that the term “exemplary” is merely meant as an example, rather than the best or optimal. Accordingly, the disclosure is intended to cover alternatives, modifications and equivalents, which may be included within the scope of the disclosure. 
     Although specific aspects have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. This disclosure is intended to cover any adaptations or variations of the specific aspects discussed herein.