Patent Publication Number: US-11664776-B2

Title: Band stop filter structure and method of forming

Description:
PRIORITY CLAIM 
     The present application is a continuation of U.S. application Ser. No. 17/109,908, filed on Dec. 2, 2020, which is a continuation of U.S. application Ser. No. 16/660,913, filed Oct. 23, 2019, now U.S. Pat. No. 10,868,509, issued Dec. 15, 2020, which is a continuation of U.S. application Ser. No. 15/863,184, filed Jan. 5, 2018, now U.S. Pat. No. 10,483,936, issued Nov. 19, 2019, which claims the priority of U.S. Provisional Application No. 62/564,757, filed Sep. 28, 2017, which are incorporated herein by reference in their entireties. 
    
    
     BACKGROUND 
     Integrated circuit (IC) packages are often used for applications in which power is distributed among one or more IC dies. Power is commonly routed to an IC die in an IC package through a post-passivation interconnect (PPI) structure that includes multiple redistribution layers (RDL). 
     As IC applications become increasingly complex and depend on increasing clock speeds and decreasing power supply voltages, sensitivity to noise such as simultaneous switching noise (SSN) and ground bounce noise (GBN) increases. Performance of filters used to suppress such noise is sometimes gauged by an S21 parameter, also referred to as a transmission coefficient, which indicates the amount of power transmitted by the filter at a given frequency. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. 
         FIGS.  1 A and  1 B  are diagrams of a band stop filter structure, in accordance with some embodiments. 
         FIG.  2    is a diagram of a cross-sectional view of an IC package, in accordance with some embodiments. 
         FIGS.  3 A- 3 D  are diagrams of band stop filter structures, in accordance with some embodiments. 
         FIGS.  4 A and  4 B  are diagrams of band stop filter structures, in accordance with some embodiments. 
         FIG.  5    is a diagram of an inductive device, in accordance with some embodiments. 
         FIGS.  6 A- 6 C  are plots of band stop filter structure parameters, in accordance with some embodiments. 
         FIG.  7    is a flowchart of a method of forming a band stop filter structure, in accordance with some embodiments. 
         FIG.  8    is a flowchart of a method of filtering a signal, in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components, values, operations, materials, arrangements, or the like, are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. Other components, values, operations, materials, arrangements, or the like, are contemplated. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. 
     Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly. 
     In various embodiments, a band stop filter structure includes a ground plane in a first metal layer of an IC package, a plate in a second metal layer of the IC package, and a dielectric layer between the ground plane and the plate, thereby forming a capacitive device. An inductive device in a third metal layer of the IC package is electrically connected to the plate, and the resultant LC circuit functions to reduce a high frequency noise component of a signal transmitted from a first terminal of the filter structure to a second terminal of the filter structure. Compared to other approaches, e.g., printed circuit board (PCB) filters, the disclosed embodiments occupy less area and avoid additional processing steps that increase manufacturing costs. 
       FIGS.  1 A and  1 B  are diagrams of a band stop filter structure  100 , in accordance with some embodiments.  FIG.  1 A  is a diagram based on a plan view of band stop filter structure  100 , and  FIG.  1 B  is a diagram based on a cross-sectional view of band stop filter structure  100  along the plane indicated by line A-A′ in  FIG.  1 A . In addition to band stop filter  100 ,  FIG.  1 A  depicts directions X and Y, and  FIG.  1 B  depicts directions X and Z. 
     Band stop filter structure  100  is a component of an IC package. In some embodiments, band stop filter structure  100  is part of a power distribution path among one or more of IC package dies, IC package interconnects, or IC package bump structures. In some embodiments, one or more band stop filter structures  100  are part of an IC package  200 , discussed below with respect to  FIG.  2   . 
     In some embodiments, band stop filter structure  100  is a component of a 2.5D IC package. In some embodiments, band stop filter structure  100  is a component of a 3D IC package. In some embodiments, band stop filter structure  100  is a component of an integrated fan-out (InFO) package. In some embodiments, band stop filter structure  100  is one band stop filter structure of a plurality of band stop filter structures in an IC package. 
     Band stop filter structure  100  includes a unit cell  100 A and a unit cell  100 B. Unit cell  100 A includes an inductive device  110 A, a plate  120 A, and a ground plane portion  130 A. Inductive device  110 A is positioned in a metal layer ML 3  of the IC package, has a perimeter  110 AP, overlies plate  120 A, and is electrically connected to plate  120 A by a via  115 A through a dielectric layer DL 2  of the IC package. Plate  120 A is positioned in a metal layer ML 2  of the IC package, has a perimeter  120 AP, overlies ground plane portion  130 A, and is electrically isolated from ground plane portion  130 A by a dielectric layer DL 1  of the IC package. Ground plane portion  130 A is a portion of a ground plane  130  positioned in a metal layer ML 1  of the IC package. 
     Plate  120 A, ground plane portion  130 A, and dielectric layer DL 1  are thereby configured as a capacitive device  140 A electrically connected to inductive device  110 A through via  115 A. 
     Unit cell  100 B includes an inductive device  110 B, a plate  120 B, and a ground plane portion  130 B. Inductive device  110 B is positioned in metal layer ML 3 , has a perimeter  110 B, overlies plate  120 B, and is electrically connected to plate  120 B by a via  115 B through dielectric layer DL 2 . Plate  120 B is positioned in metal layer ML 2 , has a perimeter  120 B, overlies ground plane portion  130 B, and is electrically isolated from ground plane portion  130 B by dielectric layer DL 1 . Ground plane portion  130 B is a portion of ground plane  130 . 
     Plate  120 B, ground plane portion  130 B, and dielectric layer DL 1  are thereby configured as a capacitive device  140 B electrically connected to inductive device  110 B through via  115 B. 
     Each of metal layers ML 1 , ML 2 , and ML 3  is a metal layer of an IC package. In some embodiments, each of metal layers ML 1 , ML 2 , and ML 3  is a metal redistribution layer of an IC package. In some embodiments, one or more of metal layers ML 1 , ML 2 , or ML 3  includes copper. In some embodiments, one or more of metal layers ML 1 , ML 2 , or ML 3  includes a seed layer containing copper or a copper alloy. In some embodiments, one or more of metal layers ML 1 , ML 2 , or ML 3  includes a diffusion barrier layer containing titanium. 
     In some embodiments, one or more of metal layers ML 1 , ML 2 , or ML 3  has a thickness (not labeled) ranging from 3 μm to 20 μm. In some embodiments, one or more of metal layers ML 1 , ML 2 , or ML 3  has a thickness ranging from 5 μm to 10 μm. One or more of metal layers ML 1 , ML 2 , or ML 3  having a smaller thickness value reduces the ability of the one or more of metal layers ML 1 , ML 2 , or ML 3  to provide desired electrical properties, e.g., conductivity, in some instances. 
     Each of dielectric layers DL 1  and DL 2  is an IC package layer including one or more materials capable of providing physical separation and high electrical resistance between one or more overlying package layers and one or more underlying package layers or an ambient environment. In some embodiments, one or both of dielectric layers DL 1  and DL 2  includes a polymer or another material suitable for physically and electrically isolating one or more overlying package layers. In some embodiments, one or both of dielectric layers DL 1  and DL 2  includes polybenzoxazole (PBO) or polyimide (PI). 
     In some embodiments, one or both of dielectric layers DL 1  and DL 2  has a thickness (not labeled) ranging from 2 micrometers (μm) to 20 μm. In some embodiments, one or both of dielectric layers DL 1  and DL 2  has a thickness ranging from 4 μm to 10 μm. One or both of dielectric layers DL 1  and DL 2  having a smaller thickness value reduces the ability of the one or both of dielectric layers DL 1  and DL 2  to provide physical and electrical isolation in some instances. 
     In some embodiments, one or both of dielectric layers DL 1  and DL 2  has a dielectric constant ranging from 2 to 5. In some embodiments, one or both of dielectric layers DL 1  and DL 2  has a dielectric constant ranging from 3 to 4. 
     Via  115 A is a conductive structure in dielectric layer DL 2  that overlies and contacts signal plate  120 A, thereby being configured to provide an electrical connection between inductive device  110 A and plate  120 A. In some embodiments, via  115 A includes a seed layer and/or a diffusion barrier layer. In some embodiments, via  115 A includes one or more metals such as copper, a copper alloy, aluminum, tungsten, and/or titanium. 
     In some embodiments, via  115 A has a thickness (not labeled) that matches the thickness of dielectric layer DL 2 . In some embodiments, unit cell  100 A includes one or more layers (not shown) in addition to dielectric layer DL 2  between inductive device  110 A and plate  120 A, and via  115 A has a thickness greater than the thickness of dielectric layer DL 2 . 
     Inductive device  110 A includes a terminal  110 A 1  and a terminal  110 A 2 . In the embodiment depicted in  FIGS.  1 A and  1 B , terminal  110 A 1  is a first terminal of inductive device  110 A, terminal  110 A 2  is a second terminal of inductive device  110 A, and via  115 A is a third terminal of inductive device  110 A so that inductive device  110 A is a three-terminal inductive device. In some embodiments, via  115 A is electrically connected to one of terminal  110 A 1  or terminal  110 A 2  so that inductive device  110 A is a two-terminal inductive device. 
     In the embodiment depicted in  FIGS.  1 A and  1 B , inductive device  110 A comprises two paths  112 A electrically connected at via  115 A at a center of inductive device  110 A, the two paths  112 A configured to provide a predetermined inductance between terminal  110 A 1  and via  115 A and between terminal  110 A 2  and via  115 A. In some embodiments, inductive device  110 A is inductive device  500 , discussed below with respect to  FIG.  5   . In some embodiments, inductive device  110 A comprises a configuration other than two paths  112 A electrically connected at via  115 A at a center of inductive device  110 A. 
     In the embodiment depicted in  FIGS.  1 A and  1 B , perimeter  110 AP is aligned with perimeter  120 AP in the Z direction so that substantially all of inductive device  110 A overlies substantially all of plate  120 A. In some embodiments, perimeter  110 AP is not aligned with perimeter  120 AP in the Z direction, and a portion or all of inductive device  110 A overlies a portion of plate  120 A. In some embodiments, perimeter  110 AP is not aligned with perimeter  120 AP in the Z direction, and a portion of inductive device  110 A overlies a portion or all of plate  120 A. 
     In the embodiment depicted in  FIGS.  1 A and  1 B , perimeter  120 AP is positioned along the inside of perimeter  110 AP. In some embodiments, perimeter  120 AP is positioned directly below perimeter  110 AP. In some embodiments, a portion of perimeter  120 AP is positioned outside of perimeter  110 AP and a portion of perimeter  120 AP is positioned inside of perimeter  110 AP. 
     Ground plane  130  has a perimeter  130 P. In the embodiment depicted in  FIGS.  1 A and  1 B , each of perimeter  110 AP and  120 AP is positioned along the inside of a portion of perimeter  130 P. In some embodiments, one or both of perimeter  110 AP or perimeter  120 AP is positioned directly above a portion of perimeter  130 P. In some embodiments, one or both of perimeter  110 AP or perimeter  120 AP is positioned along the outside of a portion of perimeter  130 P. 
     Plate  120 A has a length L along the X direction and a height H along the Y direction. An effective capacitance of capacitive device  140 A is determined in part by values of length L and height H, and by a ratio L/H of length L to height H. 
     In some embodiments, one or both of length L or height H has a value ranging from 100 micrometers (μm) to 1000 μm. In some embodiments, one or both of length L or height H has a value ranging from 300 μm to 600 μm. 
     In some embodiments, ratio L/H has a value ranging from 0.8 to 1.2. In some embodiments, ratio L/H has a value ranging from 0.9 to 1.1. In some embodiments, ratio L/H has a value approximately equal to 1.0. 
     In the embodiment depicted in  FIGS.  1 A and  1 B , inductive device  110 A, plate  120 A, and ground plane portion  130 A have a spatial relationship in which inductive device  110 A, positioned in metal layer ML 3 , overlies plate  120 A, positioned in metal layer ML 2 , and plate  120 A overlies ground plane portion  130 A, positioned in metal layer ML 1 . In some embodiments, one or more of inductive device  110 A, plate  120 A, or ground plane portion  130 A is positioned in a layer other than metal layers ML 3 , ML 2 , or ML 1 , respectively, such that inductive device  110 A, plate  120 A, and ground plane portion  130 A have a spatial relationship that differs from that depicted in  FIGS.  1 A and  1 B . 
     In some embodiments, inductive device  110 A, plate  120 A, and ground plane portion  130 A have an inverted spatial relationship corresponding to ground plane portion  130 A being positioned in metal layer ML 3 , plate  120 A being positioned in metal layer ML 2 , and inductive structure  110 A being positioned in metal layer ML 1 . In some embodiments, inductive device  110 A, plate  120 A, and ground plane portion  130 A have a spatial relationship corresponding to one of band stop filter structures  400 A or  400 B, discussed below with respect to  FIGS.  4 A and  4 B . 
     The elements of unit cell  100 B are composed and configured in the manner discussed above for the corresponding elements of unit cell  100 A. In some embodiments, unit cells  100 A and  100 B have a same configuration. In some embodiments, unit cells  100 A and  100 B have configurations that differ from each other. 
     In the embodiment depicted in  FIGS.  1 A and  1 B , band stop filter structure  100  includes two unit cells, unit cells  100 A and  100 B. In some embodiments, band stop filter structure  100  includes a single unit cell, and ground plane  130  includes only one of ground plane portions  130 A or  130 B. In some embodiments, band stop filter structure  100  includes greater than two unit cells and ground plane  130  includes one or more ground plane portions (not shown) in addition to ground plane portions  130 A and  130 B. 
     In the embodiment depicted in  FIGS.  1 A and  1 B , band stop filter structure  100  includes unit cells  100 A and  100 B configured as a 1×2 array of unit cells, i.e., one row and two columns. In some embodiments, band stop filter structure  100  includes unit cells  100 A and  100 B as part of an array of unit cells having more than two unit cells. In some embodiments, a unit cell, e.g., unit cell  100 A, is one unit cell of an array of unit cells  100 A included in a band stop filter structure such as one of band stop filter structures  300 A- 300 D, discussed below with respect to  FIGS.  3 A- 3 D . 
     Plates  120 A and  120 B are separated by a distance D along the X direction. A capacitive coupling between capacitive devices  140 A and  140 B is determined in part by a value of distance D. In some embodiments, distance D is a minimum value of a manufacturing rule for metal layer ML 2 , in which each of plates  120 A and  120 B is positioned. 
     In some embodiments, distance D has a value ranging from 10 μm to 100 μm. In some embodiments, distance D has a value ranging from 20 μm to 50 μm. Distance D having larger values increases the area occupied by band stop filter structure  100  in some instances. 
     In the embodiment depicted in  FIGS.  1 A and  1 B , via  115 A is positioned at a center of unit cell  100 A, and via  115 B is positioned at a center of unit cell  100 B. In some embodiments, one or both of vias  115 A or  115 B is positioned at another location within the corresponding unit cell  100 A or  100 B. 
     Inductive device  110 B includes a terminal  110 B 1  and a terminal  110 B 2 . Terminal  110 A 2  is electrically connected to terminal  110 B 1 . In the embodiment depicted in  FIGS.  1 A and  1 B , the entirety of inductive devices  110 A and  110 B, including each of terminals  110 A 1 ,  110 A 2 ,  110 B 1 , and  110 B 2 , is positioned in metal layer ML 3 . In some embodiments, substantially all of inductive devices  110 A and  110 B is positioned in metal layer ML 3 , and some or all of terminals  110 A 1 ,  110 A 2 ,  110 B 1 , or  110 B 2  is positioned in one or more metal layers (not shown) other than metal layer ML 3 . 
     In some embodiments, band stop filter structure  100 , in operation, receives a signal at terminal  110 A 1 , the signal comprising a power component and a noise component. In some embodiments, the power component is substantially a direct current (DC) signal and is propagated through inductive device  110 A from terminal  110 A 1  to terminal  110 A 2 , and through inductive device  110 B from terminal  110 B 1  to terminal  110 B 2 . In some embodiments, the power component is substantially a low frequency alternating current (AC) signal and is propagated through inductive device  110 A from terminal  110 A 1  to terminal  110 A 2 , and through inductive device  110 B from terminal  110 B 1  to terminal  110 B 2 . 
     The noise component is substantially an AC signal including one or more high frequencies, e.g., a radio frequency (RF) and/or a microwave frequency. In some embodiments, the noise component includes one or more frequencies above 1 gigahertz (GHz). By the configuration depicted in  FIGS.  1 A and  1 B , inductive device  110 A and capacitive device  140 A have a frequency response that, in operation, prevents a portion of the noise component from propagating from terminal  110 A 1  to terminal  110 A 2  and instead causes the portion of the noise component to propagate through inductive device  110 A and capacitive device  140 A to ground plane  130 . 
     By the configuration depicted in  FIGS.  1 A and  1 B , inductive device  110 B and capacitive device  140 B have a frequency response that, in operation, prevents a further portion of the noise component from propagating from terminal  110 B 1  to terminal  110 B 2  and instead causes the further portion of the noise component to propagate through inductive device  110 B and capacitive device  140 B to ground plane  130 . 
     By the configurations discussed above, band stop filter structure  100 , compared to other noise filtering approaches, e.g., PCB filters, occupies less area and is capable of being formed without relying on additional processing steps that increase manufacturing costs. 
       FIG.  2    is a diagram of a cross-sectional view of an IC package  200 , in accordance with some embodiments. IC package  200  includes bump structures  210 P and  210 G, power distribution paths  220 P and  220 G, band stop filter structures  230  and  240 , and IC dies  250  and  260 . Band stop filter structure  100 , discussed above with respect to  FIG.  1   , is usable as one or both of band stop filters  230  or  240 . 
     Power distribution path  220 P is configured to provide an electrical connection from bump structure  210 P to each of IC dies  250  and  260 , and power distribution path  220 G is configured to provide a ground connection between bump structure  210 G and each of IC dies  250  and  260 . 
     Band stop filter structure  230  is part of power distribution path  220 P between bump structure  210 P and IC die  250 , and part of power distribution path  220 G between bump structure  210 G and IC die  250 . In some embodiments, band stop filter structure  100 , discussed above with respect to  FIGS.  1 A and  1 B , is used as band stop filter structure  230 , one or both of inductive devices  110 A or  110 B is part of power distribution path  220 P, and ground plane  130  is part of power distribution path  220 G. 
     Band stop filter structure  240  is part of power distribution path  220 P between IC die  250  and IC die  260 , and part of power distribution path  220 G between IC die  250  and IC die  260 . In some embodiments, band stop filter structure  100 , discussed above with respect to  FIGS.  1 A and  1 B , is used as band stop filter structure  240 , one or both of inductive devices  110 A or  110 B is part of power distribution path  220 P, and ground plane  130  is part of power distribution path  220 G. 
     Bump structures  210 P and  210 G are conductive structures that overlie and contact portions of power distribution paths  220 P and  220 G, respectively, thereby being configured to provide electrical connections between power distribution paths  220 P and  220 G and corresponding external conductive elements (not shown). In some embodiments, bump structures  210 P and  210 G include lead. In some embodiments, bump structures  210 P and  210 G include lead-free materials such as tin, nickel, gold, silver, copper, or other materials suitable for providing electrical connections to external conductive elements. 
     In some embodiments, bump structures  210 P and  210 G have substantially spherical shapes. In some embodiments, bump structures  210 P and  210 G are controlled collapse chip connection (C4) bumps, ball grid array bumps, microbumps or the like. 
     Power distribution paths  220 P and  220 G are conductive structures in IC package  200 . In some embodiments, power distribution paths  220 P and  220 G are part of a PPI structure in IC package  200 . In some embodiments, power distribution paths  220 P and  220 G are part of a power distribution network within IC package  200 . In some embodiments, IC package  200  is one IC package in a plurality of IC packages, and power distribution paths  220 P and  220 G are part of a power distribution network within the plurality of IC packages. 
     Power distribution paths  220 P and  220 G include conductive and dielectric elements composed and configured in the manner of metal layers ML 1 , ML 2 , and ML 3 , dielectric layers DL 1  and DL 2 , and vias  115 A and  115 B, discussed above with respect to band stop filter structure  100  and  FIGS.  1 A and  1 B . 
     By including one or more band stop filter structures  100 , IC package  200 , compared to other approaches, e.g., IC packages including PCB filters, is capable of filtering noise using one or more filters that occupies less area and is capable of being formed without relying on additional processing steps that increase manufacturing costs. 
       FIGS.  3 A- 3 D  are diagrams of band stop filter structures  300 A- 300 D, in accordance with some embodiments. Each of band stop filter structures  300 A- 300 D includes an array of unit cells  100 A, discussed above with respect to band stop filter structure  100  and  FIGS.  1 A and  1 B . 
     As depicted in  FIG.  3 A , band stop filter structure  300 A includes a 1×4 array of unit cells  100 A, a terminal  300 A 1 , and a terminal  300 A 2 . Between terminals  300 A 1  and  300 A 2 , each of four unit cells  100 A in a single row is electrically connected to an adjacent unit cell  100 A by a shared terminal (not labeled). 
     In the manner discussed above with respect to band stop filter structure  100  and  FIGS.  1 A and  1 B , band stop filter structure  300 A is thereby configured to, in operation, receive a signal at terminal  300 A 1 , propagate a power component of the signal through inductive devices  110 A to terminal  300 A 2 , prevent a portion of a noise component of the signal from propagating from terminal  300 A 1  to terminal  300 A 2 , and instead cause the portion of the noise component to propagate through inductive devices  110 A and capacitive devices  140 A to ground plane  130 . 
     By including four unit cells  100 A, band stop filter structure  300 A is capable of propagating a larger portion of the noise component to ground in comparison to embodiments that include fewer than four unit cells, e.g., band stop filter structure  100  including unit cells  100 A and  100 B. 
     As depicted in  FIG.  3 B , band stop filter structure  300 B includes a 1×8 array of unit cells  100 A, a terminal  300 B 1 , and a terminal  300 B 2 . Between terminals  300 B 1  and  300 B 2 , each of eight unit cells  100 A in a single row is electrically connected to an adjacent unit cell  100 A by a shared terminal (not labeled). 
     In the manner discussed above with respect to band stop filter structure  100  and  FIGS.  1 A and  1 B , band stop filter structure  300 B is thereby configured to, in operation, receive a signal at terminal  300 B 1 , propagate a power component of the signal through inductive devices  110 A to terminal  300 B 2 , prevent a portion of a noise component of the signal from propagating from terminal  300 B 1  to terminal  300 B 2 , and instead cause the portion of the noise component to propagate through inductive devices  110 A and capacitive devices  140 A to ground plane  130 . 
     By including eight unit cells  100 A, band stop filter structure  300 B is capable of propagating a larger portion of the noise component to ground in comparison to embodiments that include fewer than eight unit cells, e.g., band stop filter structure  100  including unit cells  100 A and  100 B. 
     As depicted in  FIG.  3 C , band stop filter structure  300 C includes a 2×3 array of unit cells  100 A, a terminal  300 C 1 , and a terminal  300 C 2 . Between terminals  300 C 1  and  300 C 2 , each of three unit cells  100 A in each of two rows is electrically connected to an adjacent unit cell  100 A by a shared terminal (not labeled). 
     In the manner discussed above with respect to band stop filter structure  100  and  FIGS.  1 A and  1 B , band stop filter structure  300 C is thereby configured to, in operation, receive a signal at terminal  300 C 1 , propagate a power component of the signal through inductive devices  110 A to terminal  300 C 2 , prevent a portion of a noise component of the signal from propagating from terminal  300 C 1  to terminal  300 C 2 , and instead cause the portion of the noise component to propagate through inductive devices  110 A and capacitive devices  140 A to ground plane  130 . 
     By including six unit cells  100 A, band stop filter structure  300 C is capable of propagating a larger portion of the noise component to ground in comparison to embodiments that include fewer than six unit cells, e.g., band stop filter structure  100  including unit cells  100 A and  100 B. 
     As depicted in  FIG.  3 D , band stop filter structure  300 D includes a 3×3 array of unit cells  100 A, a terminal  300 D 1 , and a terminal  300 D 2 . Between terminals  300 D 1  and  300 D 2 , each of three unit cells  100 A in each of three rows is electrically connected to an adjacent unit cell  100 A by a shared terminal (not labeled). 
     In the manner discussed above with respect to band stop filter structure  100  and  FIGS.  1 A and  1 B , band stop filter structure  300 D is thereby configured to, in operation, receive a signal at terminal  300 D 1 , propagate a power component of the signal through inductive devices  110 A to terminal  300 D 2 , prevent a portion of a noise component of the signal from propagating from terminal  300 D 1  to terminal  300 D 2 , and instead cause the portion of the noise component to propagate through inductive devices  110 A and capacitive devices  140 A to ground plane  130 . 
     By including nine unit cells  100 A, band stop filter structure  300 C is capable of propagating a larger portion of the noise component to ground in comparison to embodiments that include fewer than nine unit cells, e.g., band stop filter structure  100  including unit cells  100 A and  100 B. 
     By the configurations discussed above, each of band stop filter structures  300 A- 300 D, compared to other noise filtering approaches, e.g., PCB filters, occupies less area and is capable of being formed without relying on additional processing steps that increase manufacturing costs. 
       FIGS.  4 A and  4 B  are diagrams of band stop filter structures  400 A and  4 B, in accordance with some embodiments. Each of band stop filter structures  400 A and  400 B includes features corresponding to inductive device  110 A, via  115 A, plate  120 A, and ground plane portion  130 A, discussed above with respect to unit cell  100 A of band stop filter structure  100  and  FIGS.  1 A and  1 B . 
     Band stop filter structure  400 A ( FIG.  4 A ) includes an inductive device  410 A, a conductive element  415 A, a plate  420 A, and a ground plane portion  430 A. Inductive device  410 A is positioned in metal layer ML 3  and overlies ground plane portion  430 A, positioned in metal layer ML 2 , and ground plane portion  430 A overlies plate  420 A, positioned in metal layer ML 1 . 
     Conductive element  415 A extends from inductive device  410 A to plate  420 A, thereby providing an electrical connection between inductive device  410 A and plate  420 A. In some embodiments, conductive element  415 A extends through an opening in ground plane  430 A. In some embodiments, conductive element  415 A extends outside a perimeter of ground plane  430 A. 
     Ground plane  430 A, dielectric layer DL 1 , and plate  420 A are thereby configured as a capacitive device (not labeled) electrically connected to inductive device  410 A through conductive element  415 A, and band stop filter structure  400 A is thereby configured as a unit cell having the properties discussed above with respect to unit cell  100 A of band stop filter structure  100  and  FIGS.  1 A and  1 B . 
     In some embodiments, the configuration of band stop filter structure  400 A causes band stop filter structure  400 A to have properties that differ from those of band stop filter structure  100  having similar dimensions. For example, in some embodiments, conductive element  415 A having a length greater than a length of via  115 A reduces an amount of coupling between inductive device  410 A and the capacitive device formed by ground plane  430 A, dielectric layer DL 1 , and plate  420 A, as compared to an amount of coupling between inductive device  110 A and capacitive device  140 A. 
     Band stop filter structure  400 B (depicted in  FIG.  4 B ) includes inductive devices  410 B 1  and  410 B 2 , conductive elements  415 B 1  and  415 B 2 , plates  420 B 1  and  420 B 2 , and a ground plane portion  430 B. Inductive device  410 B 1  is positioned in a metal layer ML 5  and overlies plate  420 B 1 , positioned in a metal layer ML 4 , and plate  420 B 1  overlies ground plane portion  430 B, positioned in metal layer ML 3 . A dielectric layer DL 4  is positioned between metal layers ML 5  and ML 4 , and a dielectric layer DL 3  is positioned between metal layers ML 4  and ML 3 . 
     Conductive element  415 B 1  extends from inductive device  410 B 1  to plate  420 B 1  through dielectric layer DL 4 , thereby providing an electrical connection between inductive device  410 B 1  and plate  420 B 1 . Plate  420 B 1 , dielectric layer DL 3 , and ground plane portion  430 B are configured as a capacitive device (not labeled) electrically connected to inductive device  410 B 1  through conductive element  415 B 1 . 
     Ground plane portion  430 B overlies plate  420 B 2 , positioned in metal layer ML 2 , and plate  420 B 2  overlies inductive device  410 B 2 , positioned in metal layer ML 1 . Ground plane  430 B, dielectric layer DL 2 , and plate  420 B 2  are thereby configured as a capacitive device (not labeled). Conductive element  415 B 2  extends from plate  420 B 2  to inductive device  410 B 2  through dielectric layer DL 1 , thereby providing an electrical connection between plate  420 B 2  and inductive device  410 B 2 . 
     Band stop filter structure  400 B is thereby configured as a first unit cell including inductive device  410 B 1 , conductive element  415 B 1 , plate  420 B 1 , and ground plane portion  430 B, and a second unit cell including inductive device  410 B 2 , conductive element  415 B 2 , plate  420 B 2 , and ground plane portion  430 B, each unit cell having the properties discussed above with respect to unit cell  100 A of band stop filter structure  100  and  FIGS.  1 A and  1 B . 
     In some embodiments, band stop filter  400 B includes one or more conductive elements (not shown) configured to provide an electrical connection between inductive devices  410 B 1  and  410 B 2 . 
     In some embodiments, band stop filter  400 B band stop filter  400 B includes one or more conductive elements configured to provide an electrical connection between inductive devices  410 B 1  and  410 B 2 , and does not include one of plates  420 B 1  or  420 B 2 , so that band stop filter  400 B is configured as a single unit cell including inductive devices  410 B 1  and  410 B 2  as a single, combined inductive device. 
     In some embodiments, the configuration of band stop filter structure  400 B causes band stop filter structure  400 B to have properties that differ from those of band stop filter structure  100  having similar dimensions. For example, in some embodiments, dielectric layer DL 3  having a thickness larger than a thickness of dielectric layer DL 1  reduces a capacitance value of the capacitive device formed by plate  420 B 1 , dielectric layer DL 3 , and ground plane portion  430 B, as compared to a capacitance value of capacitive device  140 A. 
     By the configurations discussed above, each of band stop filter structures  400 A and  400 B, compared to other noise filtering approaches, e.g., PCB filters, occupies less area and is capable of being formed without relying on additional processing steps that increase manufacturing costs. 
       FIG.  5    a diagram of an inductive device  500 , in accordance with some embodiments. Inductive device  500  is usable as any of inductive devices  110 A or  110 B, discussed above with respect to band stop filter structure  100  and  FIGS.  1 A and  1 B , inductive device  410 A, discussed above with respect to  FIG.  4 A , or inductive devices  410 B 1  or  410 B 2 , discussed above with respect to  FIG.  4 B . 
     Inductive device  500  comprises two rotationally symmetrical spiral paths, path  500 P 1  and path  500 P 2 . Path  500 P 1  is an electrically conductive path extending from a terminal  500 T 1  to a terminal  500 T 3  positioned at the center of inductive device  500 . Path  500 P 2  is an electrically conductive path extending from a terminal  500 T 2  to terminal  500 T 3 . Paths  500 P 1  and  500 P 2  are thereby configured to provide a predetermined inductance between corresponding terminals  500 T 1  and  500 T 3 , and terminals  500 T 2  and  500 T 3 . 
     In the embodiment depicted in  FIG.  5   , each of paths  500 P 1  and  500 P 2  has three vertical segments and four horizontal segments. In some embodiments, each of paths  500 P 1  and  500 P 2  has fewer than three vertical segments and/or fewer than four horizontal segments. In some embodiments, each of paths  500 P 1  and  500 P 2  has greater than three vertical segments and/or greater than four horizontal segments. 
     Each of paths  500 P 1  and  500 P 2  has a width  500 W, and paths  500 P 1  and  500 P 2  are separated by a distance  500 S. An effective inductance of inductive device  500  is determined in part by a value of a ratio  500 S/ 500 W. 
     In some embodiments, ratio  500 S/ 500 W has a value ranging from 1 to 2. In some embodiments, ratio  500 S/ 500 W has a value ranging from 1.5 to 1.7. In some embodiments, ratio  500 S/ 500 W has a value approximately equal to 1.6. 
     By including inductive device  500 , a band stop filter structure, compared to other noise filtering approaches, e.g., PCB filters, occupies less area and is capable of being formed without relying on additional processing steps that increase manufacturing costs. 
       FIGS.  6 A- 6 C  are plots of band stop filter structure parameters, in accordance with some embodiments.  FIGS.  6 A- 6 C  depict non-limiting examples of values of the S21 parameter, also referred to as a transmission coefficient, which indicates the amount of power transmitted by the filter at a given frequency.  FIGS.  6 A- 6 C  depict the logarithmic expression of the S21 parameter, given by:
 
 S 21=20 log 10 ( b/a )  (1)
 
where a represents input signal magnitude and b represents output signal magnitude.
 
     The non-limiting examples depicted in  FIGS.  6 A- 6 C  are based on measurements of band stop filter structures  300 A- 300 D, discussed above with respect to  FIGS.  3 A- 3 D , including inductive device  500 , discussed above with respect to  FIG.  5   . In each of  FIGS.  6 A- 6 C , S21 values are plotted along the y-axis, and frequency is plotted along the x-axis. 
     In the embodiments depicted in  FIGS.  6 A- 6 C , S21 parameter values are equivalent to S12 parameter values (representing the reverse direction transmission coefficient) based on the reciprocal configuration of band stop filter structures  300 A- 300 D including inductive device  500 . In some embodiments that do not include a reciprocal configuration, S21 parameter values are not equivalent to S12 parameter values. 
       FIG.  6 A  depicts a plot of S21 values for embodiments of band stop filter structure  300 A corresponding to 1×4 arrays of square unit cells having varying sizes. Curve M 2  depicts S21 values for a 1×4 array of unit cells having length L and height H equal to 300 μm, for which a resonance frequency is 8.5 GHz. Curve M 3  depicts S21 values for a 1×4 array of unit cells having length L and height H equal to 400 μm, for which a resonance frequency is 4.7 GHz. Curve M 4  depicts S21 values for a 1×4 array of unit cells having length L and height H equal to 500 μm, for which a resonance frequency is 2.7 GHz. Curve M 5  depicts S21 values for a 1×4 array of unit cells having length L and height H equal to 600 μm, for which a resonance frequency is 1.7 GHz. 
     Curves M 2 -M 5  provide a non-limiting example of a relationship between unit cell size to resonance frequency, in which resonance frequency increases as unit cell size decreases. 
       FIG.  6 B  depicts a plot of S21 values for embodiments of band stop filter structures  300 A and  300 B. Curve M 6  depicts S21 values for an embodiment of band stop filter structure  300 A corresponding to a 1×4 array of square unit cells having length L and height H equal to 600 μm. Curve M 7  depicts S21 values for an embodiment of band stop filter structure  300 B corresponding to a 1×8 array of square unit cells having length L and height H equal to 600 μm. 
     Curves M 6  and M 7  provide a non-limiting example of a relationship between unit cell array size and S21 values in which S21 values are lower for a 1×8 unit cell array than for a 1×4 unit cell array. 
       FIG.  6 C  depicts a plot of S21 values for embodiments of band stop filter structures  300 C and  300 D. Curve M 8  depicts S21 values for an embodiment of band stop filter structure  300 C corresponding to a 2×3 array of square unit cells having length L and height H equal to 500 μm. Curve M 9  depicts S21 values for an embodiment of band stop filter structure  300 D corresponding to a 3×3 array of square unit cells having length L and height H equal to 500 μm. 
     Curves M 8  and M 9  provide a non-limiting example of a relationship between unit cell array size and S21 values in which S21 values are lower for a 3×3 unit cell array than for a 2×3 unit cell array. 
       FIG.  7    is a flowchart of a method  700  of forming a band stop filter structure, in accordance with some embodiments. Method  700  is operable to form any of band stop filter structures  100 ,  300 A- 300 C,  400 A, or  400 B, discussed above with respect to  FIGS.  1 A,  1 B,  3 A- 3 C,  4 A, and  4 B . 
     In some embodiments, the operations of method  700  are performed in the order depicted in  FIG.  7   . In some embodiments, the operations of method  700  are performed in an order other than the order depicted in  FIG.  7   . In some embodiments, one or more additional operations are performed before, during, and/or after the operations of method  700 . 
     In some embodiments, operations of method  700  are a subset of operations of a method of forming an IC package. In some embodiments, the operations of method  700  are a subset of operations of a method of forming a 2.5D IC package. In some embodiments, the operations of method  700  are a subset of operations of a method of forming a 3D IC package. In some embodiments, the operations of method  700  are a subset of operations of a method of forming an InFO package. In some embodiments, the operations of method  700  are a subset of operations of a method of forming IC package  200 , discussed above with respect to  FIG.  2   . 
     At operation  710 , a ground plane is formed in a first PPI layer of an IC package. In some embodiments, forming the ground plane in the first PPI layer of the IC package includes forming the ground plane in IC package  200 , discussed above with respect to  FIG.  2   . 
     In some embodiments, forming the ground plane in the first PPI layer of the IC package includes forming ground plane  130  in metal layer ML 1 , discussed above with respect to band stop filter structure  100  and  FIGS.  1 A and  1 B . In some embodiments, forming the ground plane in the first PPI layer of the IC package includes forming ground plane  430 A in metal layer ML 2 , discussed above with respect to band stop filter structure  400 A and  FIG.  4 A . In some embodiments, forming the ground plane in the first PPI layer of the IC package includes forming ground plane  430 B in metal layer ML 3 , discussed above with respect to band stop filter structure  400 B and  FIG.  4 B . 
     In some embodiments, forming the ground plane in the first PPI layer of the IC package includes forming one ground plane of a plurality of ground planes in the first PPI layer of the IC package. 
     In some embodiments, forming the ground plane in the first PPI layer of the IC package includes depositing a metal such as copper. In some embodiments, forming the ground plane in the first PPI layer of the IC package includes depositing a seed layer containing copper or a copper alloy. In some embodiments, forming the ground plane in the first PPI layer of the IC package includes forming a diffusion barrier layer containing titanium. 
     In some embodiments, forming the ground plane in the first PPI layer of the IC package includes depositing one or more materials through a patterned photoresist layer that is then removed. In some embodiments, forming the ground plane in the first PPI layer of the IC package includes performing one or more deposition processes followed by performing one or more etching processes. 
     In some embodiments, forming the ground plane in the first PPI layer of the IC package includes forming the ground plane to a thickness ranging from 3 μm to 20 μm. In some embodiments, forming the ground plane in the first PPI layer of the IC package includes forming the ground plane to a thickness ranging from 5 μm to 10 μm. Forming the ground plane to the thickness values discussed above enables the ground plane to provide electrical conductivity and to be formed by processes consistent with one or more other IC package formation processes, thereby avoiding additional processes that increase production costs in some instances. 
     At operation  720 , a plate is formed in a second PPI layer of the IC package. In some embodiments, forming the plate in the second PPI layer of the IC package includes forming the plate in IC package  200 , discussed above with respect to  FIG.  2   . 
     In some embodiments, forming the plate in the second PPI layer of the IC package includes forming one or both of plates  120 A or  120 B in metal layer ML 2 , discussed above with respect to band stop filter structure  100  and  FIGS.  1 A and  1 B . 
     In some embodiments, forming the plate in the second PPI layer of the IC package includes forming plate  420 A in metal layer ML 1 , discussed above with respect to band stop filter structure  400 A and  FIG.  4 A . In some embodiments, forming the plate in the second PPI layer of the IC package includes forming plate  420 B 1  in metal layer ML 4 , discussed above with respect to band stop filter structure  400 B and  FIG.  4 B . In some embodiments, forming the plate in the second PPI layer of the IC package includes forming plate  420 B 2  in metal layer ML 2 , discussed above with respect to band stop filter structure  400 B and  FIG.  4 B . 
     In some embodiments, forming the plate in the second PPI layer of the IC package includes forming one plate of a plurality of plates in the second PPI layer of the IC package. In some embodiments, forming the plate in the second PPI layer of the IC package includes forming one plate of a plurality of plates in an array of unit cells of a band stop filter structure. In some embodiments, forming the plate in the second PPI layer of the IC package includes forming one plate of a plurality of plates in an array of unit cells  100 A of one of band stop filter structures  300 A- 300 D, discussed above with respect to  FIGS.  3 A- 3 D . 
     In some embodiments, forming the plate in the second PPI layer of the IC package includes depositing a metal such as copper. In some embodiments, forming the plate in the second PPI layer of the IC package includes depositing a seed layer containing copper or a copper alloy. In some embodiments, forming the plate in the second PPI layer of the IC package includes forming a diffusion barrier layer containing titanium. 
     In some embodiments, forming the plate in the second PPI layer of the IC package includes depositing one or more materials through a patterned photoresist layer that is then removed. In some embodiments, forming the plate in the second PPI layer of the IC package includes performing one or more deposition processes followed by performing one or more etching processes. 
     In some embodiments, forming the plate in the second PPI layer of the IC package includes forming the plate to a thickness ranging from 3 μm to 20 μm. In some embodiments, forming the plate in the second PPI layer of the IC package includes forming the plate to a thickness ranging from 5 μm to 10 μm. Forming the plate to the thickness values discussed above enables the plate to provide electrical conductivity and to be formed by processes consistent with one or more other IC package formation processes, thereby avoiding additional processes that increase production costs in some instances. 
     At operation  730 , a dielectric layer is deposited between the ground plane and the plate. In some embodiments, depositing the dielectric layer between the ground plane and the plate includes depositing the dielectric layer in IC package  200 , discussed above with respect to  FIG.  2   . 
     In some embodiments, depositing the dielectric layer between the ground plane and the plate includes depositing dielectric layer DL 1 , discussed above with respect to band stop filter structure  100  and  FIGS.  1 A and  1 B  and with respect to band stop filter structure  400 A and  FIG.  4 A . In some embodiments, depositing the dielectric layer between the ground plane and the plate includes depositing dielectric layer DL 3 , discussed above with respect to band stop filter structure  400 B and  FIG.  4 B . In some embodiments, depositing the dielectric layer between the ground plane and the plate includes depositing dielectric layer DL 2 , discussed above with respect to band stop filter structure  400 B and  FIG.  4 B . 
     In some embodiments, depositing the dielectric layer between the ground plane and the plate includes depositing a polymer or another material suitable for physically and electrically isolating one or more overlying package layers. In some embodiments, depositing the dielectric layer between the ground plane and the plate includes depositing PBO or PI. 
     In various embodiments, depositing the dielectric layer between the ground plane and the plate includes performing a physical vapor deposition (PVD) or chemical vapor deposition (CVD) process, a laser chemical vapor deposition (LCVD) process, an evaporation process, an electron beam evaporation (E-gun) process, or another suitable deposition process. 
     In some embodiments, depositing the dielectric layer between the ground plane and the plate includes depositing the dielectric layer to have a thickness ranging from 2 μm to 20 μm. In some embodiments, depositing the dielectric layer between the ground plane and the plate includes depositing the dielectric layer to have a thickness ranging from 4 μm to 10 μm. Depositing the dielectric layer to have a smaller thickness value reduces the ability of the dielectric layer to provide physical and electrical isolation in some instances. 
     At operation  740 , an inductive device is formed in a third PPI layer of the IC package. In some embodiments, forming the inductive device in the third PPI layer of the IC package includes forming the inductive device in IC package  200 , discussed above with respect to  FIG.  2   . 
     In some embodiments, forming the inductive device in the third PPI layer of the IC package includes forming one or both of inductive devices  110 A or  110 B in metal layer ML 3 , discussed above with respect to band stop filter structure  100  and  FIGS.  1 A and  1 B . 
     In some embodiments, forming the inductive device in the third PPI layer of the IC package includes forming inductive device  410 A in metal layer ML 3 , discussed above with respect to band stop filter structure  400 A and  FIG.  4 A . In some embodiments, forming the inductive device in the third PPI layer of the IC package includes forming inductive device  410 B 1  in metal layer ML 5 , discussed above with respect to band stop filter structure  400 B and  FIG.  4 B . In some embodiments, forming the inductive device in the third PPI layer of the IC package includes forming inductive device  410 B 2  in metal layer ML 1 , discussed above with respect to band stop filter structure  400 B and  FIG.  4 B . In some embodiments, forming the inductive device in the third PPI layer of the IC package includes forming inductive device  500 , discussed above with respect to  FIG.  5   . 
     In some embodiments, forming the inductive device in the third PPI layer of the IC package includes forming one inductive device of a plurality of inductive devices in the third PPI layer of the IC package. In some embodiments, forming the inductive device in the third PPI layer of the IC package includes forming one inductive device of a plurality of inductive devices in an array of unit cells of a band stop filter structure. In some embodiments, forming the inductive device in the third PPI layer of the IC package includes forming one inductive device of a plurality of inductive devices in an array of unit cells  100 A of one of band stop filter structures  300 A- 300 D, discussed above with respect to  FIGS.  3 A- 3 D . 
     In some embodiments, forming the inductive device in the third PPI layer of the IC package includes depositing a metal such as copper. In some embodiments, forming the inductive device in the third PPI layer of the IC package includes depositing a seed layer containing copper or a copper alloy. In some embodiments, forming the inductive device in the third PPI layer of the IC package includes forming a diffusion barrier layer containing titanium. 
     In some embodiments, forming the inductive device in the third PPI layer of the IC package includes depositing one or more materials through a patterned photoresist layer that is then removed. In some embodiments, forming the inductive device in the third PPI layer of the IC package includes performing one or more deposition processes followed by performing one or more etching processes. 
     In some embodiments, forming the inductive device in the third PPI layer of the IC package includes forming the inductive device to a thickness ranging from 3 μm to 20 μm. In some embodiments, forming the inductive device in the third PPI layer of the IC package includes forming the inductive device to a thickness ranging from 5 μm to 10 μm. Forming the inductive device to the thickness values discussed above enables the inductive device to provide electrical conductivity and to be formed by processes consistent with one or more other IC package formation processes, thereby avoiding additional processes that increase production costs in some instances. 
     At operation  750 , an electrical connection is constructed between the plate and the inductive device. In some embodiments, constructing the electrical connection between the plate and the inductive device includes constructing the electrical connection in IC package  200 , discussed above with respect to  FIG.  2   . 
     In some embodiments, constructing the electrical connection between the plate and the inductive device includes constructing a via between the second PPI layer and the third PPI layer. In some embodiments, constructing the electrical connection between the plate and the inductive device includes constructing one or both of vias  115 A or  115 B in dielectric layer DL 2 , discussed above with respect to band stop filter structure  100  and  FIGS.  1 A and  1 B . 
     In some embodiments, constructing the electrical connection between the plate and the inductive device includes constructing conductive element  415 A in dielectric layers DL 1  and DL 2  and in metal layer ML 2 , discussed above with respect to band stop filter structure  400 A and  FIG.  4 A . In some embodiments, constructing the electrical connection between the plate and the inductive device includes constructing conductive element  415 B 1  in dielectric layer DL 4 , discussed above with respect to band stop filter structure  400 B and  FIG.  4 B . In some embodiments, constructing the electrical connection between the plate and the inductive device includes constructing conductive element  415 B 2  in dielectric layer DL 1 , discussed above with respect to band stop filter structure  400 B and  FIG.  4 B . 
     In some embodiments, constructing the electrical connection between the plate and the inductive device includes constructing one electrical connection of a plurality of electrical connections between a corresponding plurality of plates and a corresponding plurality of inductive devices. In some embodiments, constructing the electrical connection between the plate and the inductive device includes constructing one electrical connection of a plurality of electrical connections in an array of unit cells of a band stop filter structure. In some embodiments, constructing the electrical connection between the plate and the inductive device includes constructing one electrical connection of a plurality of electrical connections in an array of unit cells  100 A of one of band stop filter structures  300 A- 300 D, discussed above with respect to  FIGS.  3 A- 3 D . 
     In some embodiments, constructing the electrical connection between the plate and the inductive device includes depositing copper. In some embodiments, constructing the electrical connection between the plate and the inductive device includes depositing a seed layer containing copper or a copper alloy. In some embodiments, constructing the electrical connection between the plate and the inductive device includes depositing a diffusion barrier layer containing titanium. 
     In some embodiments, performing operations  720  and  740  includes forming a perimeter of the plate and a perimeter of the inductive device aligned in a direction perpendicular to a plane of the ground plane. In some embodiments, performing operations  720  and  740  includes forming one or both of perimeters  110 AP or  110 BP aligned with corresponding one or both of perimeters  120 AP or  120 BP in the Z direction, discussed above with respect to band stop filter structure  100  and  FIGS.  1 A and  1 B . 
     The operations of method  700  are capable of being performed as part of a method of forming an IC package and are usable to form a band stop filter structure that includes at least one L/C circuit, thereby obtaining the benefits discussed above with respect to band stop filter structures  100 ,  300 A- 300 D,  400 A, and  400 B. 
       FIG.  8    a flowchart of a method  800  of filtering a signal, in accordance with some embodiments. Method  800  is usable with a band stop filter structure, e.g., band stop filter structure  100  ( FIGS.  1 A and  1 B ), band stop filter structures  300 A- 300 D ( FIGS.  3 A- 3 D ), or band stop filter structures  400 A and  400 B ( FIGS.  4 A and  4 B ), or with an IC package, e.g., IC package  200 , discussed above with respect to  FIG.  2   . 
     At operation  810 , an input signal is received at a first terminal of a filter structure in an IC package. The input signal includes a low frequency component and a high frequency component. 
     In some embodiments, the low frequency component includes a substantially DC signal. In some embodiments, the low frequency component includes an AC signal having one or more frequency components below a predetermined frequency. In some embodiments, the predetermined frequency defining the low frequency component has a value ranging from 100 hertz (Hz) to 100 megahertz (MHz). In some embodiments, the predetermined frequency defining the low frequency component has a value ranging from 1000 Hz to 100 kilohertz (kHz). 
     The high frequency component is an AC signal including one or more high frequency components above a predetermined frequency. In some embodiments, the predetermined frequency defining the high frequency component has a value ranging from 100 MHz to 100 GHz. In some embodiments, the predetermined frequency defining the high frequency component has a value ranging from 1 GHz to 10 GHz. 
     In some embodiments, the low frequency component is a power component and/or the high frequency component is a noise component, as discussed above with respect to band stop filter structure  100  and  FIGS.  1 A and  1 B . 
     In some embodiments, receiving the input signal at the first terminal of the filter structure includes receiving the input signal within IC package  200 , discussed above with respect to  FIG.  2   . In some embodiments, receiving the input signal at the first terminal of the filter structure includes receiving the input signal at terminal  110 A 1  of inductive device  110 A, discussed above with respect to band stop filter structure  100  and  FIGS.  1 A and  1 B . In some embodiments, receiving the input signal at the first terminal of the filter structure includes receiving the input signal at terminal  110 B 1  of inductive device  110 B, discussed above with respect to band stop filter structure  100  and  FIGS.  1 A and  1 B . 
     In some embodiments, receiving the input signal at the first terminal of the filter structure includes receiving the input signal at terminal  300 A 1  of band stop filter structure  300 A, discussed above with respect to  FIG.  3 A . In some embodiments, receiving the input signal at the first terminal of the filter structure includes receiving the input signal at terminal  300 B 1  of band stop filter structure  300 B, discussed above with respect to  FIG.  3 B . In some embodiments, receiving the input signal at the first terminal of the filter structure includes receiving the input signal at terminal  300 C 1  of band stop filter structure  300 C, discussed above with respect to  FIG.  3 C . In some embodiments, receiving the input signal at the first terminal of the filter structure includes receiving the input signal at terminal  300 D 1  of band stop filter structure  300 D, discussed above with respect to  FIG.  3 D . 
     In some embodiments, receiving the input signal at the first terminal of the filter structure includes receiving the input signal at inductive device  410 A, discussed above with respect to band stop filter structure  400 A and  FIG.  4 A . In some embodiments, receiving the input signal at the first terminal of the filter structure includes receiving the input signal at inductive device  410 B 1 , discussed above with respect to band stop filter structure  400 B and  FIG.  4 B . In some embodiments, receiving the input signal at the first terminal of the filter structure includes receiving the input signal at inductive device  410 B 2 , discussed above with respect to band stop filter structure  400 B and  FIG.  4 B . In some embodiments, receiving the input signal at the first terminal of the filter structure includes receiving the input signal at terminal  500 T 1  of inductive device  500 , discussed above with respect to  FIG.  5   . 
     At operation  820 , the high frequency component of the input signal is reduced using the filter structure to generate an output signal. In some embodiments, reducing the high frequency component of the input signal includes reducing a noise component, as discussed above with respect to band stop filter structure  100  and  FIGS.  1 A and  1 B . 
     Reducing the high frequency component of the input signal using the filter structure includes using the filter structure including an inductive device and a capacitive device. The inductive device is located in a first metal layer of the IC package and the capacitive device is electrically connected to the inductive device. The capacitive device includes a first metal plate in a second metal layer of the IC package and a second metal plate in a third metal layer of the IC package. 
     In some embodiments, the inductive device and the capacitive device are located within IC package  200 , and reducing the high frequency component of the input signal includes reducing the high frequency component of the input signal within IC package  200 , discussed above with respect to  FIG.  2   . 
     In some embodiments, reducing the high frequency component of the input signal includes using one or both of unit cells  100 A or  100 B, discussed above with respect to band stop filter structure  100  and  FIGS.  1 A and  1 B . 
     In some embodiments, reducing the high frequency component of the input signal includes using one of band stop filter structures  300 A- 300 D, discussed above with respect to  FIGS.  3 A- 3 D . 
     In some embodiments, reducing the high frequency component of the input signal includes using inductive device  110 A, discussed above with respect to band stop filter structure  100  and  FIGS.  1 A and  1 B . In some embodiments, reducing the high frequency component of the input signal includes using inductive device  110 B, discussed above with respect to band stop filter structure  100  and  FIGS.  1 A and  1 B . 
     In some embodiments, reducing the high frequency component of the input signal includes using inductive device  410 A, discussed above with respect to band stop filter structure  400 A and  FIG.  4 A . In some embodiments, reducing the high frequency component of the input signal includes using inductive device  410 B 1 , discussed above with respect to band stop filter structure  400 B and  FIG.  4 B . In some embodiments, reducing the high frequency component of the input signal includes using inductive device  410 B 2 , discussed above with respect to band stop filter structure  400 B and  FIG.  4 B . In some embodiments, reducing the high frequency component of the input signal includes using inductive device  500 , discussed above with respect to  FIG.  5   . 
     In some embodiments, reducing the high frequency component of the input signal includes using one or both of capacitive devices  140 A or  140 B, discussed above with respect to band stop filter structure  100  and  FIGS.  1 A and  1 B . 
     In some embodiments, the capacitive device including the first plate in the second metal layer of the IC package includes one or both of capacitive devices  140 A or  140 B including ground plane  130 , discussed above with respect to band stop filter structure  100  and  FIGS.  1 A and  1 B . In some embodiments, the capacitive device including the second plate in the third metal layer of the IC package includes capacitive device  140 A including plate  120 A, discussed above with respect to band stop filter structure  100  and  FIGS.  1 A and  1 B . In some embodiments, the capacitive device including the second plate in the third metal layer of the IC package includes capacitive device  140 B including plate  120 B, discussed above with respect to band stop filter structure  100  and  FIGS.  1 A and  1 B . In some embodiments, the capacitive device including the first plate in the second metal layer of the IC package includes the capacitive device including plate  420 A, discussed above with respect to band stop filter structure  400 A and  FIG.  4 A . In some embodiments, the capacitive device including the first plate in the second metal layer of the IC package includes the capacitive device including plate  420 B 1 , discussed above with respect to band stop filter structure  400 B and  FIG.  4 B . In some embodiments, the capacitive device including the first plate in the second metal layer of the IC package includes the capacitive device including plate  420 B 2 , discussed above with respect to band stop filter structure  400 B and  FIG.  4 B . 
     In some embodiments, the filter structure includes another inductive device in the first metal layer electrically connected to another capacitive device including the first plate and a third plate in the third metal layer of the IC package. 
     In some embodiments, the filter structure including another inductive device includes the filter structure including inductive device  110 B, discussed above with respect to band stop filter structure  100  and  FIGS.  1 A and  1 B . In some embodiments, the filter structure including another inductive device includes the filter structure including inductive device  410 A, discussed above with respect to band stop filter structure  400 A and  FIG.  4 A . In some embodiments, the filter structure including another inductive device includes the filter structure including one of inductive devices  410 B 1  or  410 B 2 , discussed above with respect to band stop filter structure  400 B and  FIG.  4 B . In some embodiments, the filter structure including another inductive device includes the filter structure including inductive device  500 , discussed above with respect to  FIG.  5   . 
     In some embodiments, the filter structure including another capacitive device includes the filter structure including capacitive device  140 B, discussed above with respect to band stop filter structure  100  and  FIGS.  1 A and  1 B . In some embodiments, the another capacitive device including the third plate in the third metal layer of the IC package includes capacitive device  140 B including plate  120 B, discussed above with respect to band stop filter structure  100  and  FIGS.  1 A and  1 B . 
     In some embodiments, the another capacitive device including the third plate in the third metal layer of the IC package includes the capacitive device including plate  420 A, discussed above with respect to band stop filter structure  400 A and  FIG.  4 A . In some embodiments, the another capacitive device including the third plate in the third metal layer of the IC package includes the capacitive device including one of plates  420 B 1  or  420 B 2 , discussed above with respect to band stop filter structure  400 B and  FIG.  4 B . 
     In some embodiments, the filter structure including an inductive device and a capacitive device includes the filter structure including a first unit cell  100 A, and the filter structure including another inductive device and another capacitive device includes the filter structure including a second unit cell  100 A, discussed above with respect to band stop filter structures  300 A- 300 D and  FIGS.  3 A- 3 D . 
     In some embodiments, reducing the high frequency component of the input signal includes transmitting a remaining portion of the high frequency component corresponding to a transmission coefficient. In some embodiments, reducing the high frequency component of the input signal includes transmitting the remaining portion of the high frequency component corresponding to transmission coefficients M 2 -M 9 , discussed above with respect to  FIGS.  6 A- 6 C . 
     In some embodiments, reducing the high frequency component of the input signal includes reducing the high frequency component based on a predetermined resonance frequency corresponding to a size of the inductive device and a size of the capacitive device. In some embodiments, the predetermined resonance frequency is greater than 1 GHz. 
     At operation  830 , the output signal is provided at a second terminal of the filter structure. In some embodiments, providing the output signal at the second terminal of the filter structure includes providing the output signal within IC package  200 , discussed above with respect to  FIG.  2   . 
     In some embodiments, providing the output signal at the second terminal of the filter structure includes providing the output signal at terminal  110 A 2  of inductive device  110 A, discussed above with respect to band stop filter structure  100  and  FIGS.  1 A and  1 B . In some embodiments, providing the output signal at the second terminal of the filter structure includes providing the output signal at terminal  110 B 2  of inductive device  110 B, discussed above with respect to band stop filter structure  100  and  FIGS.  1 A and  1 B . 
     In some embodiments, providing the output signal at the second terminal of the filter structure includes providing the output signal at terminal  300 A 2  of band stop filter structure  300 A, discussed above with respect to  FIG.  3 A . In some embodiments, providing the output signal at the second terminal of the filter structure includes providing the output signal at terminal  300 B 2  of band stop filter structure  300 B, discussed above with respect to  FIG.  3 B . In some embodiments, providing the output signal at the second terminal of the filter structure includes providing the output signal at terminal  300 C 2  of band stop filter structure  300 C, discussed above with respect to  FIG.  3 C . In some embodiments, providing the output signal at the second terminal of the filter structure includes providing the output signal at terminal  300 D 2  of band stop filter structure  300 D, discussed above with respect to  FIG.  3 D . 
     In some embodiments, providing the output signal at the second terminal of the filter structure includes providing the output signal at inductive device  410 A, discussed above with respect to band stop filter structure  400 A and  FIG.  4 A . In some embodiments, providing the output signal at the second terminal of the filter structure includes providing the output signal at inductive device  410 B 1 , discussed above with respect to band stop filter structure  400 B and  FIG.  4 B . In some embodiments, providing the output signal at the second terminal of the filter structure includes providing the output signal at inductive device  410 B 2 , discussed above with respect to band stop filter structure  400 B and  FIG.  4 B . In some embodiments, providing the output signal at the second terminal of the filter structure includes providing the output signal at terminal  500 T 2  of inductive device  500 , discussed above with respect to  FIG.  5     
     By performing operations of method  800 , a signal has a high frequency component reduced between a first terminal and a second terminal of a filter structure in an IC package, the signal therefore being communicated in accordance with the benefits discussed above with respect to band stop filter structures  100 ,  300 A- 300 D,  400 A, and  400 B. 
     In some embodiments, a filter structure includes a ground plane in a first metal layer of an IC package; a plate in a second metal layer of the IC package; a dielectric layer between the ground plane and the plate, the ground plane, the dielectric layer, and the plate thereby being configured as a capacitive device; and an inductive device in a third metal layer of the IC package. The inductive device is electrically connected to the plate, and the plate and the inductive device are configured to have a resonance frequency greater than 1 GHz. In some embodiments, the plate is positioned between the ground plane and the inductive device. In some embodiments, a perimeter of the plate is aligned with a perimeter of the inductive device. In some embodiments, the inductive device comprises two symmetrical spiral paths electrically connected at a center of the inductive device. In some embodiments, the filter structure further includes a via extending from the center of the inductive device to the plate. In some embodiments, each path of the two symmetrical spiral paths has a width w, the two symmetrical spiral paths are separated by a spacing s, and a ratio s/w has a value ranging from 1 to 2. In some embodiments, the plate and the inductive device are part of a first unit cell, and the filter structure comprises an array of unit cells including the first unit cell. In some embodiments, each unit cell of the array of unit cells includes the ground plane. In some embodiments, the array of unit cells is one of a 1×4 array, a 1×8 array, a 2×3 array, or a 3×3 array. In some embodiments, the inductive device is part of a power distribution path of the IC package. 
     In some embodiments, a method of forming a filter structure includes forming a ground plane in a first PPI layer of an IC package; forming a plate in a second PPI layer of the IC package; depositing a dielectric layer between the ground plane and the plate; forming an inductive device in a third PPI layer of the IC package; and constructing an electrical connection between the plate and the inductive device. The plate and inductive device have dimensions corresponding to a resonance frequency greater than 1 GHz. In some embodiments, constructing the electrical connection between the plate and the inductive device includes constructing a via between the second PPI layer and the third PPI layer. In some embodiments, forming the plate and the forming the inductive device includes forming a perimeter of the plate and a perimeter of the inductive device aligned in a direction perpendicular to a plane of the ground plane. In some embodiments, forming the inductive device includes forming a spiral path having a width w and a spacing s, and a ratio s/w has a value ranging from 1 to 2. In some embodiments, forming the plate is part of forming a plurality of plates, forming the inductive device is part of forming a plurality of inductive devices, each inductive device of the plurality of inductive devices being electrically connected to a corresponding plate of the plurality of plates, and constructing the capacitive device is part of constructing a plurality of capacitive devices, each capacitive device of the plurality of capacitive devices including the ground plane and a corresponding plate of the plurality of plates. 
     In some embodiments, a method of forming a filter structure includes constructing a capacitive device by forming a ground plane in a first PPI layer of an IC package, forming a plate in a second PPI layer of the IC package, and depositing a dielectric layer between the ground plane and the plate; constructing a via between the plate and a third PPI layer of the IC package; and forming an inductive device in the third PPI layer of the IC package by electrically connecting first and second conductive paths to the via. Forming the plate and the inductive device includes forming each of the plate and inductive device having a length L and a height H corresponding to a resonance frequency greater than 1 GHz. In some embodiments, electrically connecting the first and second conductive paths to the via includes forming a plurality of vertical segments and a plurality of horizontal segments. In some embodiments, forming the inductive device in the third PPI layer includes the second PPI layer being between the first and third PPI layers. In some embodiments, forming the plate includes forming the plate having a length L and a height H and a ratio L/H having a value ranging from 0.9 to 1.1. In some embodiments, depositing the dielectric layer between the ground plane and the plate includes depositing polybenzoxazole (PBO) and/or polyimide (PI). 
     The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.