Patent Publication Number: US-2021175162-A1

Title: Secure semiconductor integration

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     The present application claims benefit and is a continuation of application Ser. No. 16/724,319 filed on Dec. 22, 2019, the content of which is incorporated herein by reference in its entirety. Application Ser. No. 16/724,319 claims benefit and is a continuation of application Ser. No. 15/810,050 filed on Nov. 11, 2017 (now U.S. Pat. No. 10,515,886 issued on Dec. 24, 2019), the content of which is incorporated herein by reference in its entirety, whereby Ser. No. 15/810,050 claims benefit and is a continuation of application Ser. No. 14/746,045 filed on Jun. 22, 2015, the content of which is incorporated herein by reference in its entirety, whereby application Ser. No. 14/746,045 claims benefit and is a continuation-in-part of application Ser. No. 14/717,798 filed May 20, 2015, the content of which is incorporated herein by reference in its entirety 
     The present application claims benefit and is a continuation of allowed application Ser. No. 14/746,045 filed on Jun. 22, 2015 which claims benefit under 35 USC 119 (e) of U.S. Provisional Application No. 62/015,459 filed Jun. 22, 2014 (now expired), the content of which is incorporated herein by reference in its entirety. 
     The present application claims benefit and is a continuation of allowed application Ser. No. 14/746,045 filed on Jun. 22, 2015 which claims benefit and is a continuation-in-part of allowed application Ser. No. 14/717,798 filed May 20, 2015 which claims benefit under 35 USC 119 (e) of U.S. Provisional Application No. 62/002,794 filed May 24, 2014 (now expired), the content of which is incorporated herein by reference in its entirety. 
    
    
     FIELD 
     The subject matter herein relates to packaging semiconductor devices. 
     BACKGROUND 
     The packaging of electronic devices is becoming more important as demands increase for miniaturization, speed, improved reliability, weight reduction and security. A variety packages are under development such as a die-scale package, at a wafer level; and a die stack-type package. Die have been attached to an interposer to mount the die onto a printed circuit board (PCB) through an organic package substrate to translate the fine geometries of the interposer to the much larger spacing of the printed circuit board. An increasing number of conductive pads of the printed circuit board must be coordinated with more bonding pads on the semiconductor die to improve input/output (I/O) throughput. 
     As Moore&#39;s law approaches its decrescendo and the cost per transistor increases below the  22  nm node, device makers are seeking alternative solutions to stay competitive. Semiconductor device manufacturers have been relying on Multi-Chip-Module (MCM)  100  shown in  FIGS. 1A and 1B .  2 D monolithic dies ( 120 ,  130 ) are integrated on an organic substrate  160  assembled on a Printed Circuit Board (PCB)  110 .  2 D monolithic dies  120  may be flip chip dies mechanically and electrically connected to organic substrate  160  by way of solder bumps  140 . Alternatively, 2D monolithic dies  130  may be electrically connected to organic substrate  160  by way of wirebonds  131 . Ball Grid Array (BGA)  150  may be used to connect organic substrate  160  to PCB  110 . This approach results in a relatively low yield due to the increase in substrate size which causes mechanical stresses and other yield killing effects. 
     These shortcomings were partially addressed by moving to a Package-on-Package (POP) architecture as shown in  FIGS. 2A and 2B . A Package-on-Package architecture may possess a vertical stacking of one monolithic die  201  above a second monolithic die  202  in the depicted manner. Monolithic die  201  and monolithic die  202  each have their own organic substrate ( 231  and  232 , respectively). Monolithic die  201  is individually packaged on organic substrate  231  using solder balls  221  whereas monolithic die  202  is individually packaged onto organic substrate  232  using solder balls  222 . Clearance is provided for monolithic die  202  by incorporating organic substrates  210  which may provide electrical connections between organic substrate  231  and organic substrate  232  through additional solder balls  220 . Practical considerations (e.g. reliability and maintaining a low profile) limit the number of levels which can be implemented in this Package-on-Package architecture. A perspective view is provided in  FIG. 2B  to help visualize the completed package in three dimensions. The size of the solder bumps may be increased and provide the clearance for monolithic die  202  which does indeed lower the profile, however, the technique also reduces the number of electrical connections which may be made between organic substrate  231  and organic substrate  232 . 
     More recently, “2.5D” and “3D” integration techniques have been developed to improve yield, profile and performance. 2.5D/3D approaches may also increase the reuse of monolithic integrated circuit (“chip”) designs whose development costs have already been amortized. Various chip designs (often referred to as IP) perhaps from differing process nodes and perhaps from different foundries can be integrated together to form a functional circuit device. In a homogeneous 2.5D/3D integration approach, as illustrated in  FIG. 3A , a single chip  300  is partitioned into number of smaller chips ( 305 ,  310 ,  315 ,  320 ). Smaller chips ( 305 ,  310 ,  315 ,  320 ) are then assembled onto interposer  325  and wired together to form an electronic package.  FIG. 3B  shows a heterogeneous 2.5D/3D integration approach. Single chip  330  includes a number of circuitry blocks including memory  335 , logic  340 , DSP  345 , and RF  350  manufactured separately and mounted on interposer  355  and wired together to form an electronic package. Smaller chips ( 335 ,  340 ,  345 ,  350 ) may be manufactured by different foundries and may have different process nodes selected for performance, availability and/or cost reasons. 
     Hardware is needed which further increase the number of transistors per device to improve processing performance and/or lower the cost per transistor. 
     SUMMARY 
     Semiconductor packages are described which increase the density of electronic components within. The semiconductor package may incorporate interposers with cavities formed into the top and/or bottom. The cavities may then be used as locations for the electronic components. Alternatively, narrow spacer interposers may be used to space apart standard more laterally elongated interposers to form the indentations used to house the electronic components. The height of the clearance is equal to the height of the standoff interposers in embodiments. The semiconductor package designs described herein may be used to reduce footprint, reduce profile and increase electronic component and transistor density for semiconductor products. The cavities and clearances may form a conduit configured to promote fluid flow and enhance cooling of the integrated circuits during operation in embodiments. 
     Embodiments disclosed herein pertain to electronic packages including a substantially-planar first semiconductor interposer. The first semiconductor interposer includes a first plurality of through-substrate vias perpendicular to the major plane of the first semiconductor interposer and passing through the entire thickness of the first semiconductor interposer. Embodiments further include a substantially-planar second semiconductor interposer having a second major plane parallel to the first major plane. The second semiconductor interposer includes a second plurality of through-substrate vias perpendicular to the major plane of the second semiconductor interposer and passing through the entire thickness of the second semiconductor interposer. Embodiments further include at least one standoff interposer disposed between the first semiconductor interposer and the second semiconductor interposer. The at least one standoff interposer is affixed to each of the first semiconductor interposer and the second semiconductor interposer. The at least one standoff interposer forms a clearance between the first semiconductor interposer and the second semiconductor interposer. The standoff interposer includes an intervening plurality of through-substrate vias passing through the entire thickness of the at least one standoff interposer. A portion of the second plurality of through-substrate vias are electrically connected to a portion of the first through-substrate vias by way of a portion of the intervening through-substrate vias. Embodiments further include at least one electronic component disposed within the clearance and electrically coupled to the first semiconductor interposer by a first plurality of electrical connections. 
     Each of the first semiconductor interposer, the second semiconductor interposer and the standoff interposer may be crystalline silicon or single crystal silicon. The at least one standoff interposer may include at least two standoff interposers forming two parallel lines near two opposing edges of the first semiconductor interposer. The clearance may be the region between the two parallel lines and between the first semiconductor interposer and the second semiconductor interposer. The at least one standoff interposer may encircle the clearance resulting in no pathways for fluid egress or ingress. In other words, the standoff may go all the way around the perimeter of the interposers above and below to increase security in embodiments. The at least one standoff interposer may include at least nine standoff interposers arranged in a regular grid pattern. A width of the standoff interposer may be between 5% and 45% of a width of the interposer. A height of the standoff interposer may be between 50 μm and 300 μm. Embodiments may further include a cloaking plurality of through-substrate vias through the standoff interposer ground on the outside of the intervening plurality of through-substrate vias. A cloaking linear density of the cloaking plurality of through-substrate vias may exceed the intervening linear density of the intervening plurality of through-substrate vias. 
     Embodiments disclosed herein pertain to electronic packages including a substantially-planar first semiconductor interposer having a rectilinear cavity formed into one or more of a top surface of the first semiconductor interposer or the bottom surface of the first semiconductor interposer when the first major plane of the first semiconductor interposer is positioned horizontally. The first semiconductor interposer includes a first plurality of through-substrate vias perpendicular to the major plane of the first semiconductor interposer and passing through the entire thickness of the first semiconductor interposer. The first through-substrate vias are disposed outside the rectilinear cavity. Embodiments further include a substantially-planar second semiconductor interposer having a second major plane parallel to the first major plane. The second semiconductor interposer includes a second plurality of through-substrate vias perpendicular to the major plane of the second semiconductor interposer and passing through the entire thickness of the second semiconductor interposer. A portion of the second plurality of through-substrate vias are electrically connected to a portion of the first plurality of through-substrate vias. Embodiments further include at least one electronic component disposed entirely within the rectilinear cavity and electrically coupled to the first semiconductor interposer by a first plurality of electrical connections within the rectilinear cavity. 
     At least one electronic component may include at least one monolithic integrated circuit. Each of the first semiconductor interposer and the second semiconductor interposer may be silicon interposers. A width of the rectilinear cavity may be between 10% and 90% of the width of the first semiconductor interposer. The widths of the first semiconductor interposer and the second semiconductor interposer may be essentially the same. A depth of the rectilinear cavity may be between 50 μm and 300 μm. 
     Embodiments disclosed herein pertain to electronic packages including a substantially-planar first semiconductor interposer. The first semiconductor interposer includes a first plurality of electrical connections generally perpendicular to the major plane of the first semiconductor interposer and passing through the thickness of the first semiconductor interposer. Embodiments further include a substantially-planar second semiconductor interposer having a second major plane parallel to the first major plane. The second semiconductor interposer includes a second plurality of electrical connections generally perpendicular to the major plane of the second semiconductor interposer and passing through the thickness of the second semiconductor interposer. A portion of the second plurality of electrical connections are electrically connected to a portion of the first plurality of electrical connections. A first space is disposed between the first semiconductor interposer and the second semiconductor interposer. Embodiments further include a substantially-planar third interposer having a third major plane parallel to the first major plane. A second space is disposed between the third interposer and the second semiconductor interposer. Embodiments further include at least one first electronic component disposed between the first semiconductor interposer and the second semiconductor interposer. 
     The first space may include a cavity. The first space may include a clearance between two or more standoff interposers. The first space may be configured to pass a cooling fluid to keep an operating temperature of the at least one first electronic component below a threshold value. The at least one first electronic component may be encapsulated within a molding compound filling the remainder of the first space. All electrical connections between the first semiconductor interposer and the second semiconductor interposer may be direct ohmic contacts. The third interposer may have no electrical connections on top as a security measure. The portion of the first plurality of electrical connections and the portion of the second plurality of electrical connections are essentially directly electrically connected to one another with no intervening interposer. The portion of the first plurality of electrical connections and the portion of the second plurality of electrical connections are electrically connected by way of one or more standoff interposer. The third semiconductor interposer may include a third plurality of electrical connections generally perpendicular to the major plane of the third semiconductor interposer and passing through the thickness of the third semiconductor interposer. A portion of the third plurality of electrical connections are electrically connected to a portion of the second plurality of electrical connections. Embodiments may further include a sensor affixed to the top of the third semiconductor interposer and electrically connected to a portion of the third plurality of electrical connections. At least one of the at least one first electronic component and at least one of the at least one second electronic component may be a monolithic integrated circuit, a passive electronic component, an antenna, a sensor, or a power source. The third interposer may be a cap having no electronic connections on top. Embodiments may further include at least one second electronic component disposed between the semiconductor interposer and the third interposer. At least two of the at least one first electronic component may be keyed such that two of the electronic components will only operate properly when both are present. 
     Additional embodiments and features are set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the specification or may be learned by the practice of the disclosed embodiments. The features and advantages of the disclosed embodiments may be realized and attained by means of the instrumentalities, combinations, and methods described in the specification. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       A further understanding of the nature and advantages of the embodiments may be realized by reference to the remaining portions of the specification and the drawings. 
         FIG. 1A  is a side-view schematic of a Multi-Chip-Module package according to the prior art. 
         FIG. 1B  is a top-view schematic of a Multi-Chip Module package according to the prior art. 
         FIG. 2A  is a side-view schematic of a Package-on-Package architecture according to the prior art. 
         FIG. 2B  is a perspective-view schematic of a Package-on-Package architecture according to the prior art. 
         FIG. 3A  is a top-view schematic of homogeneous partitioning according to the prior art. 
         FIG. 3B  is a top-view schematic of heterogeneous partitioning according to the prior art. 
         FIGS. 4A, 4B and 4C  are side-view schematics of interposers during the formation of cavities according to embodiments. 
         FIGS. 5A and 5B  are side-view schematics of portions of semiconductor packages with electronic components positioned in cavities according to embodiments. 
         FIGS. 6A and 6B  are side-view schematics of portions of semiconductor packages with electronic components positioned in a clearance created by standoff interposers according to embodiments. 
         FIG. 6C  is a perspective view of a portion of a semiconductor package with electronic components positioned in a clearance created by standoff interposers according to embodiments. 
         FIGS. 7A and 7B  are side view schematics of portions of semiconductor packages with electronic components positioned in clearance formed by a combination of standoff interposers and a cavity according to embodiments. 
         FIG. 8A  is a side view schematic of a portion of a semiconductor package with electronic components positioned in multiple stacked cavities according to embodiments. 
         FIG. 8B  is a side view schematic of a portion of a semiconductor package with electronic components positioned in cavities on both sides of a single interposer according to embodiments. 
         FIG. 9A  is a side-view schematic of a portion of a semiconductor package with electronic components positioned in clearances created by standoff interposers according to embodiments. 
         FIG. 9B  is a perspective view of a portion of a semiconductor package with electronic components positioned in clearances created by standoff interposers according to embodiments. 
         FIG. 10A  is a side-view schematic of a portion of a semiconductor package with electronic components positioned in clearances created by standoff interposers according to embodiments. 
         FIG. 10B  is a perspective view of a portion of a semiconductor package with electronic components positioned in clearances created by standoff interposers according to embodiments. 
         FIGS. 11A and 11B  are side-view schematics of portions of semiconductor packages with electronic components positioned in clearances created by standoff interposers according to embodiments. 
         FIG. 12A  is a side-view schematic of a portion of a semiconductor package with electronic components positioned in clearances created by standoff interposers according to embodiments. 
         FIG. 12B  is a perspective view of a portion of a semiconductor package with electronic components positioned in clearances created by standoff interposers according to embodiments. 
         FIGS. 13A and 13B  are top-view schematics of portions of semiconductor packages with electronic components positioned in clearances created by standoff interposers according to embodiments. 
         FIG. 14  is a top-view schematic of a portion of a semiconductor package with electronic components positioned in clearances created by standoff interposers according to embodiments. 
         FIG. 15  is a top-view schematic of a portion of a standoff interposer according to embodiments. 
         FIGS. 16A, 16B, 16C and 16D  are top-view schematics of portions of semiconductor packages according to embodiments. 
         FIG. 17  is a side view schematic of a portion of a semiconductor package with keyed electronic components positioned within a clearance according to embodiments. 
         FIGS. 18A and 18B  are side-view schematics of portions of semiconductor packages with electronic components positioned in clearances created by standoff interposers according to embodiments. 
         FIG. 19  is a perspective view of a portion of a semiconductor package according to embodiments. 
         FIG. 20  is a perspective view of a portion of a semiconductor package according to embodiments. 
     
    
    
     In the appended figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label. 
     DETAILED DESCRIPTION 
     Semiconductor packages are described which increase the density of electronic components within. The semiconductor package may incorporate interposers with cavities formed into the top and/or bottom. The cavities may then be used as locations for the electronic components. Alternatively, narrow spacer interposers may be used to space apart standard more laterally elongated interposers to form the indentations used to house the electronic components. The height of the clearance is equal to the height of the standoff interposers in embodiments. The semiconductor package designs described herein may be used to reduce footprint, reduce profile and increase electronic component and transistor density for semiconductor products. The cavities and clearances may form a conduit configured to promote fluid flow and enhance cooling of the electronic components during operation in embodiments. 
     The semiconductor packages described herein possess cavities and/or standoff interposers to create spaces for a plurality of electronic components in a high density and high performance configuration. In embodiments, the semiconductor packages described may result in a smaller footprint, lower profile, miniaturized, higher performance, and thermally enhanced, and more secure packages. The packages may involve a combination of interposers, redistribution layers (RDL), through-substrate vias (TSV), so-called “zero-ohm” links, copper pillars, solder bumps, compression bonding, and bumpless packaging. In addition to these techniques, cavities may be made into the interposer and/or standoff interposers may be used to provide spaces (clearance) for a plurality of electronic components (e.g. passives, antennas, integrated circuits or chips) in embodiments. The standoff interposers may include redistribution layers on the top and/or bottom while a through-substrate via passes vertically through the standoff interposer. Standoff interposers may be formed, for example, by bonding multiple interposers together by thermocompression bonding or another low-profile connection technique. Oxide bonding techniques or laterally shifting any standoff interposer described herein enable wirebonds to be used to connect the standoff interposer to a printed circuit board, a substrate, or an underlying interposer in embodiments. Generally speaking, any interposer described herein may be shifted relative to the other interposers in the stack to allow the formation of wirebonds. The semiconductor interposer may be a silicon interposer according to embodiments. 
     Electronic packages formed in the manner described herein possess improved reliability, lower cost, and higher performance due to a shortening of electrical distance and an increase in density of integrated circuit mounting locations. Reliability may be improved for embodiments which use the same semiconductor (e.g. silicon) for all interposers used to form the semiconductor package. The techniques presented also provide improvement in solder joint reliability and a reduction in warpage. Warping may occur during the wafer processing and thinning of the semiconductor interposer. The second opportunity for warping occurs during the packaging and assembly. The chance of warping increases for larger interposer lengths and package dimensions which is currently necessary for a variety of 2.5D/3D integration applications (e.g. networking). The vertical density of integrated circuits may be increased which allows the horizontal area to be reduced to achieve the same performance. 
       FIG. 4A, 4B and 4C  are side-view schematics of interposers during the formation of cavities according to embodiments. An interposer  400 - 1  is shown in  FIG. 4A  prior to forming any cavities for electronic components.  FIG. 4B  shows an interposer  400 - 2  having a top cavity  410  as well as a bottom cavity  420 .  FIG. 4C  shows an interposer  400 - 3  having four cavities ( 430 ,  440 ,  450 ,  460 ) formed into its top and bottom surfaces. The dotted lines define the extent of the cavity in the direction of the opening for the purposes of determining whether a die is within the cavity or entirely within the cavity herein. 
     When describing all embodiments herein, “Top” and “Up” will be used herein to describe portions/directions perpendicularly distal from the printed circuit board (PCB) plane and further away from the center of mass of the PCB in the perpendicular direction. “Vertical” will be used to describe items aligned in the “Up” direction towards the “Top”. Other similar terms may be used whose meanings will now be clear. “Major planes” of objects will be defined as the plane which intersects the largest area of an object such as an interposer. Some standoff interposers may be “aligned” in “lines” along the longest of the three dimensions and may therefore be referred to as “linear” standoff interposers. Electrical connections may be made between interposers (standoff or planar interposer) and the pitch of the electrical connections may be between 1 μm and 150 μm or between 10 μm and 100 μm in all embodiments described herein. Electrical connections between neighboring semiconductor interposers herein may be direct ohmic contacts which may include direct bonding/oxide bonding or adding a small amount of metal such as a pad between, for example, through silicon vias. 
       FIG. 5A and 5B  are side-view schematics of interposers with electronic components positioned in cavities according to embodiments. Following the formation of cavities in interposer  500 , four electronic components (dies  510 ,  515 ,  520 ,  525 ) are then assembled within the cavities using a variety of electrical connection methods (e.g. copper pillar or micro bumps). A plurality of dies are placed within or entirely within a cavity of an interposer in embodiments. Interposer  500  is then electrically and mechanically attached to printed circuit board  530  using solder balls  540 . Multiple interposers having dies placed in cavities may be stacked vertically and electrically/mechanically attached to a printed circuit board, according to embodiments, as further shown in  FIG. 5B . 
       FIGS. 6A, 6B and 6C  are side-view and perspective view schematics of interposers with electronic components positioned in a clearance created by standoff interposers according to embodiments. No cavity is created in interposer  630 , however, clearance for die is provided by standoff interposers  600 . Silicon cap  650  may be used to create a confined channel for fluid flow. Silicon cap  650  may include a redistribution layer on the bottom for routing electrical signals in the completed semiconductor package which is shown assembled in  FIG. 6B . Silicon cap  650  (or a cap more generally) may include passive components or active components in embodiments. Silicon cap  650  may have no electrical connections on the top, according to embodiments, to increase security and to provide protection against probing by electrical taps. Alternatively, silicon cap  650  may be replaced by an interposer with through-connections such as through-substrate vias in embodiments. All elements of the package depicted in  FIG. 6A  can be manufactured separately and may have bonding pads ( 610 ,  620 ,  640 ) included for electrical connections in the assembled configuration of  FIG. 6B . Thermocompression bonding or low temperature bonding method may be used to fuse all the elements together according to embodiments. The perspective view of  FIG. 6C  shows the assembled device with silicon cap  650  removed to allow viewing of some 3-d aspects of the semiconductor package. Standoff interposers  600  may be linearly parallel to one another as shown and may be positioned near two edges of interposer  630  to create a path for fluid or air flow in embodiments. Standoff interposers, interposers and caps may all be formed from the same semiconducting material (e.g. silicon), in embodiments, to match the coefficients of thermal expansion and reduce application of repetitive stresses. 
     The dimensions of interposers and standoff interposers described herein vary widely. Interposers may be as large as a full wafer, e.g. hundreds of millimeters across. Interposers may be as small as several millimeters across (e.g. 5 mm×5 mm). The interposers may be asymmetric as well for certain applications. Cavities may vary in dimensions as well and may depend on the size of the electronic component (e.g. a monolithic integrated circuit) ultimately placed within the cavity as well as the number of connections across the interposer outside the cavity (where the interposer-interposer direct connection is made). Cavity widths may be between 10% and 90%, 20% to 70% or 20% to 40% of the width of the interposer itself according to embodiments. Correspondingly, standoff interposer widths may be between 5% and 45%, between 15% and 40% or between 30% and 40% of the width of the interposer in embodiments. Cavity depths may be between 50 μm and 300 μm, between 75 μm and 250 μm or between 100 μm and 200 μm according to embodiments. Correspondingly, standoff interposer heights may be between 25 μm and 1,000 μm, between 50 μm and 300 μm, between 75 μm and 250 μm or between 100 μm and 200 μm according to embodiments. These dimensions apply to all embodiments described herein. 
       FIG. 7A and 7B  are side view schematics of interposers with electronic components positioned in clearance formed by a combination of standoff interposers and a cavity according to embodiments. A cavity  700  is formed on the top side of silicon interposer  710 . Electrical components are then electrically and mechanically attached to silicon interposer  710  and attachment may occur prior to assembly in embodiments. The electrical components in the example include two (e.g. monolithic) integrated circuits  760  and  770 . The electrical components may be entirely within cavity  700  according to embodiments (as with all components and cavities described herein). A silicon cap  740  is also formed and electrical components may be electrically and mechanically attached to the underside of silicon cap  740  in embodiments.  FIG. 7B  shows an integrated circuit  783 , a passive electrical component  781  and an antenna  782 . Electronic components will be used herein to describe integrated circuits or other active component, a passive electrical component such as an inductor, an antenna or a power source such as a battery according to embodiments. Integrated circuits may be used to refer to monolithic integrated circuits in embodiments. Standoff interposers  720  (which may be silicon as with all interposers herein) are also formed and used to attach a cap  740  to interposer  710  (each of which may also be silicon in all examples herein) and also to leave an additional clearance for the additional electronic components ( 783 ,  781  and  782 ). Standoff interposers  720  may also provide high density electrical routing and connectivity between interposer  710  and cap  740 . Again, cap  740  may be included to improve security (as with all embodiments described herein) and also to confine a fluid flow channel to increase the speed and concentration of the coolant flow. The height of the cavity and/or the height of the silicon stand-off help determine the cooling effectiveness and may be selected based on thermal management considerations. 
       FIG. 8A  is a side view schematic of a portion of a semiconductor package with electronic components positioned in multiple stacked cavities according to embodiments.  FIG. 8A  shows an embodiment where no silicon standoffs are used but electronic components  830  (e.g. monolithic integrated circuits) are placed among a plurality of vertically arranged cavities in a stack of interposers  810 . Thermocompression or low temperature bonding may be used to bond interposers  810  directly together for enhanced miniaturization and to form a low profile package. In all embodiments herein, the clearances and/or cavities may or may not be filled with molding compound. All sides of the semiconductor packages described herein may be closed to enhance security especially in cases where the design does not require a coolant fluid (e.g. air) to be flowed through the channel to cool the (e.g. monolithic) integrated circuits. 
       FIG. 8B  is a side view schematic of a portion of a semiconductor package with electronic components positioned in cavities on both sides of a single interposer according to embodiments. Standoff interposers  820  are also present to create a clearance between interposer  810 - 5  and interposer  810 - 6 . Note that the top interposers ( 810 - 4  and  810 - 6 ) may also be caps or silicon caps as before in embodiments. Electronic components  830  of  FIG. 8B  may be located entirely within cavities made in an interposer as shown. The cavities are defined as stopping at the top or bottom plane of the interposer (e.g. the dotted line) and the clearance begins at the dotted line and continues to the top or bottom surface of the nearest neighboring interposer. In other words, the clearance is defined by the height of standoff interposers  820 . Electronic components may be placed partially or wholly inside a cavity, not only to increase packing density, but also to make electronic probing of the electrical connections (e.g. ball grid arrays) on the underside of the electronic components according to embodiments. 
       FIGS. 9A and 9B  are a side-view schematic and a perspective view of a portion of a semiconductor package with electrical components  930  positioned in clearances created by standoff interposers  920  according to embodiments. Components may be assembled using direct thermocompression or low temperature bonding methods on an interposer  910  without a cavity in embodiments.  FIGS. 9A and 9B  illustrate an example of a very low profile semiconductor package in which there is little or no gap on the side of the electrical component  930  opposite from the electrical and mechanical attachment according to embodiments. The height of the standoff interposers  920  may be the same or within 5% of the height of the electrical components  930  located on the same level in embodiments. The front and back of the semiconductor package ( FIGS. 9A-9B ) may still be left open to allow some small amount of cooling fluid flow. 
       FIGS. 10A and 10B  are a side-view schematic and a perspective view of a portion of a semiconductor package with electrical components  1030  positioned in clearances created by standoff interposers  1020  according to embodiments. Components may be assembled using direct thermocompression or low temperature bonding methods on an interposer  1010  without a cavity in embodiments. Alternatively, solder balls may be used when the clearance is adequate according to embodiments.  FIGS. 10A and 10B  illustrate an example of a high electric component density semiconductor package in which there are electronic components  1030  near the top and bottom a clearance created by standoff interposers  1020  between interposers  1010  in embodiments. In applications where thermal generation is more significant, thicker standoff interposers may be used to create adequate passage for fluid flow according to embodiments. The height of the standoff interposers  1020  may be greater than twice the height of electronic components  1030  or greater than thrice the height of electronic components  1030  in embodiments. As with all embodiments described herein, the front and back of the semiconductor package ( FIGS. 10A-10B ) may be left open to allow some small amount of cooling fluid flow or else the remaining clearance may be filled with molding compound to encapsulate the electronic components  1030  according to embodiments. 
       FIGS. 11A and 11B  are side-view schematics of portions of semiconductor packages with electronic components positioned in clearances created by standoff interposers according to embodiments. Embodiments implementing solder bumps in place of thermocompression or low temperature bonding are shown. A cap (e.g. an interposer cap or a silicon cap) may be incorporated at the top of the stack to increase security of the completed semiconductor package in embodiments. As with all embodiments described herein, electronic components may be assembled on interposers using solder bumps or copper pillars according to embodiments. The underside of the caps may be configured with redistribution layers but no connections may be present on the top or through the caps in embodiments. A semiconductor interposer right below the cap (e.g. the silicon cap in  FIG. 11B ) may provide additional routing channels on the top for routing signals or power according to embodiments. The cap on the top may contain one or more antennas to allow package-to-package or stack-to-stack wireless communication in embodiments.  FIGS. 12A and 12B  are side-view schematics of portions of semiconductor packages showing a standoff interposer between two other standoff interposers. Complex scalable systems may be formed using multiple standoff interposers placed at various intervals to allow high bandwidth chip-to-chip communication in embodiments. Three or more standoff interposers may be implemented to provide additional structure to a semiconductor package according to embodiments. 
       FIGS. 13A and 13B  are top-view schematics of portions of semiconductor packages with electronic components positioned in clearances created by standoff interposers according to embodiments. Shown are interposer  1310 , electronic component  1330 , standoff interposer  1320 , a battery and a storage register. Standoff interposer  1320 - 1  may encircle electronic components or standoff interposer  1320 - 2  may not encircle electronic components (which allows an air channel for example) in embodiments. Security may be increased by reducing or eliminating access to electrical signals within a semiconductor package in embodiments. An energy source (e.g. a battery) may be included, according to embodiments, to allow continued operation of electronic components for a period of time when power is interrupted. During this period of time, stored code may be executed which completes an operation such as a transfer, cleans up (e.g. zeros storage locations), scrambles and/or encrypts the data present in various memory locations in or near an integrated circuit (e.g. the storage register). The energy source is shown inside the package in  FIGS. 13A and 13B  but may be located outside or completely off the semiconductor package in embodiments. 
       FIG. 14  is a top-view schematic of a portion of a semiconductor package with electronic components positioned in clearances created by standoff interposers according to embodiments. The standoff interposer shown in  FIG. 14  encircles electronic components as was the case for standoff interposer  1320 - 1  in  FIG. 13A  to increase security by making signals more difficult to tap into during operation in the field. Signal vias ( 1401 ,  1450 ) pass through the standoff interposer and expanded views are included as a visual convenience. Dummy vias ( 1410 ,  1420 ,  1430 ,  1440 ,  1460 ,  1470 ) may be included to obscure electromagnetic signals which may otherwise be read, e.g. outside the semiconductor package, according to embodiments. Two columns of dummy vias ( 1410 ,  1420 ) are included outside of signal vias  1401 . The example involves dummy vias but dummy vias may also be replaced by power supply vias which then serve two purposes in embodiments. According to alternative embodiments, power supply vias may be protected by dummy vias since sensitive signals may sometimes ride on the power supply voltage. All vias which are helpful in shielding or obscuring sensitive signals may be referred to as signal-blocking vias. Two columns of dummy vias are shown outside ( 1430 ,  1440 ) and inside ( 1460 ,  1470 ) the signal vias  1450 . The dummy vias may simply obscure an electromagnetic signal outside the semiconductor package or may conduct dummy/gibberish electrical signals intentionally included to further obscure the electromagnetic signal from signal vias ( 1401 ,  1450 ) or from power supplies in some cases. One column of dummy vias may be included on the outside or inside of a column of signal vias in embodiments. One column of dummy vias may be included on the outside and inside of a column of signal vias according to embodiments. Two or more columns of dummy vias may be included on the outside or inside of a column of signal vias in embodiments. The two (or more) columns of dummy vias may be staggered (as shown e.g. with dummy vias  1410  and  1420 ) to further avoid having meaningful electromagnetic signals pass to the outside of a semiconductor package according to embodiments. Generally speaking, a variety of signal transmission items may be used beyond the exemplary vias ( 1401 ,  1450 ). The signal transmission items may, for example, be vias, solder bumps or pads in embodiments. 
       FIG. 15  is a top-view schematic of a portion of a standoff interposer according to embodiments. Signal vias  1501  (or power vias in embodiments) may be shielded on the outside, the inside or both sides by a column of signal-blocking vias (e.g. ground supply, power supply or dummy vias  1510 ) according to embodiments. The column of signal-blocking vias  1510  (also referred to herein as cloaking vias) may be more closely spaced together compared to signal vias  1501  (or power vias in embodiments) to increase the security by discouraging propagation of electromagnetic signals outside a semiconductor package in embodiments. 
       FIGS. 16A, 16B, 16C and 16D  are top-view schematics of portions of semiconductor packages according to embodiments. To further minimize or eliminate tampering with the package from top and bottoms sides a series of mesh is created to mask the signal traces on layer below. In embodiments, ground mesh  1610 - 1  is created on a layer (e.g. layer one in the figure) with power mesh  1601 - 1  created in staggered position with respect to layer one on a separate layer (e.g. layer two). The presence of ground mesh  1610 - 1 , a dummy mesh (not shown) and/or power mesh  1601 - 1  may mask signal traces  1620  (and power traces in embodiments) routed on layer three increasing privacy and security. Ground mesh  1610 - 2  and power mesh  1601 - 2  may both be present on a single layer or each of multiple layers in embodiments.  FIG. 16D  shows power mesh  1601 - 2  and ground mesh  1610 - 2  on each of layer one and layer two to thwart attempts to tap the electromagnetic signals formed by signal traces  1620 . These techniques may also be used inside or on the integrated circuits to improve security as well. 
       FIG. 17  is a side view schematic of a portion of a semiconductor package with keyed electronic components positioned within a clearance according to embodiments. A security code/master key may be stored inside integrated circuit  1701  in embodiments such that only select additional chips (also storing the corresponding key) may operate properly when present in the same semiconductor package. Integrated circuits ( 1710 ,  1720 ,  1730 ) are equipped with the proper security code in the example. According to embodiments, some or all keyed integrated circuits may be located within a clearance as shown, or located in a cavity according to embodiments. One or a plurality of integrated circuits may have the matching code to select the difficulty associated with a potential counterfeiting operation. 
     Electronic packages described herein may include high-performance miniature scalable and secure processing units equipped with a variety of integrated circuit types. A plurality of processors may be mounted on one side of an interposer while a plurality of memory dies may be mounted on the opposite side in embodiments. Processor cores may be mounted on one side of an interposer while memory is mounted on the opposite side according to embodiments. Processor cores and memory dies may be interspersed on both sides of an interposer in embodiments. According to embodiments, processor cores and memory dies may be both present on each side of an interposer but segregated into homogeneous integrated circuit groups. A homogeneous group of processor cores may be separated from a homogeneous group of memory dies by a standoff interposer in embodiments. 
       FIGS. 18A and 18B  are side-view schematics of portions of semiconductor packages with electronic components positioned in clearances created by standoff interposers according to embodiments. Semiconductor packaged described herein may be scalable heterogeneous units for interne-of-things (IOT) applications. A plurality of sensors may be place on one side of the interposer while an analog-to-digital convertor maybe placed on the opposite side or same side as the sensors. Processors and memory units may be placed in the lower stacks of the semiconductor package. A cap (e.g. a silicon cap) may be used, in embodiments, in situations where the presence of a silicon cap may not interfere with the operation of the sensors (see  FIG. 18A ). Sensors may be placed on top of an uppermost interposer ( FIG. 18B ) to facilitate access of the sensors to environmental conditions. 
     Semiconductor packages described herein may include heterogeneous or homogeneous memory units in embodiments. Memory dies may be placed on one side or both sides interposers while high bandwidth standoff interposers may be used with bumps or compression bonding attachments method. Dimensions of the high bandwidth standoff interposers may be selected to manage heat generated during the operation of the electronic components (memory in this case). 
       FIG. 19  and  FIG. 20  are perspective views of portions of semiconductor packages according to embodiments. Previous examples showed standoff interposers in the form of walls aligned in the same direction, in part, to guide airflow and promote cooling in embodiments. Standoff interposers may also be more discrete elements positioned at regular intervals in a two-dimensional array ( FIG. 19 ) according to embodiments.  FIG. 20  shows a more irregular distribution of standoff interposers still positioned discretely across the two-dimensional surface of an interposer. The distribution may be random in embodiments. Generally speaking, standoff interposers may be of any size or shape and may be located anywhere on the substrate to provide high speed and/or high bandwidth local connections among nearby electronic components (e.g. die as shown). 
     Semiconductor packages and devices formed according to the designs described herein may be used to form higher performance, cooler, more secure and tamper resistant, and more scalable 2.5D/3D heterogeneous systems than prior art designs. 
     Having disclosed several embodiments, it will be recognized by those of skill in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the disclosed embodiments. Additionally, a number of well-known processes and elements have not been described to avoid unnecessarily obscuring the embodiments described herein. Accordingly, the above description should not be taken as limiting the scope of the claims. 
     Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limits of that range is also specifically disclosed. Each smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in that stated range is encompassed. The upper and lower limits of these smaller ranges may independently be included or excluded in the range, and each range where either, neither or both limits are included in the smaller ranges is also encompassed within the embodiments described, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included. 
     As used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a process” includes a plurality of such processes and reference to “the dielectric material” includes reference to one or more dielectric materials and equivalents thereof known to those skilled in the art, and so forth. 
     Also, the words “comprise,” “comprising,” “include,” “including,” and “includes” when used in this specification and in the following claims are intended to specify the presence of stated features, integers, components, or steps, but they do not preclude the presence or addition of one or more other features, integers, components, steps, acts, or groups.