Patent Publication Number: US-2021193603-A1

Title: Circuitry for electrical redundancy in bonded structures

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application No. 62/953,084, filed Dec. 23, 2019, the entire contents of which are hereby incorporated by reference herein in their entirety and for all purposes. 
    
    
     BACKGROUND 
     Field 
     The field relates to circuitry for electrical redundancy in bonded structures. 
     Description of the Related Art 
     Multiple semiconductor elements (such as integrated device dies) may be stacked on top of one another in various applications, such as high bandwidth memory (HBM) devices or other devices that utilize vertical integration. The stacked elements can electrically communicate with one another through arrays of contact pads. It can be important to ensure that the electrical connections between contact pads on two stacked elements are reliable. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Specific implementations will now be described with reference to the following drawings, which are provided by way of example, and not limitation. 
         FIG. 1A  is a schematic top plan view of a bonded structure showing locations of voids. 
         FIG. 1B  is a schematic cross sectional view of the bonded structure of  FIG. 1A . 
         FIG. 1C  is a schematic cross sectional view of a bonded structure according to an embodiment. 
         FIG. 2A  illustrates switching circuitry comprising a bi-directional circuit according to an embodiment. 
         FIG. 2B  illustrates switching circuitry comprising a bi-directional circuit according to another embodiment. 
         FIG. 2C  illustrates switching circuitry comprising a demultiplexer (DEMUX) according to an embodiment. 
         FIG. 2D  illustrates switching circuitry comprising a multiplexer (MUX) according to an embodiment. 
         FIG. 3  illustrates switching circuitry comprising an AND gate according to an embodiment. 
         FIG. 4  illustrates switching circuitry comprising a plurality of multiplexers (MUX) according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Two or more semiconductor elements (such as integrated device dies) may be stacked on or bonded to one another to form a bonded structure. Conductive contact pads of one element may be electrically connected to corresponding conductive contact pads of another element. Any suitable number of elements can be stacked in the bonded structure. In some embodiments, the elements are directly bonded to one another without an adhesive. In other embodiments, the elements may be bonded with a conductive adhesive, such as solder, etc. 
     In various embodiments, a dielectric field region of a first element (e.g., a first semiconductor device die with active circuitry) can be directly bonded (e.g., using dielectric-to-dielectric bonding techniques) to a corresponding dielectric field region of a second element (e.g., a second semiconductor device die with active circuitry) without an adhesive. For example, dielectric-to-dielectric bonds may be formed without an adhesive using the direct bonding techniques disclosed at least in U.S. Pat. Nos. 9,391,143 and 10,434,749, the entire contents of each of which are incorporated by reference herein in their entirety and for all purposes. Dielectrics that can be treated and activated for direct bonding include, for example, inorganic dielectrics, particularly those including silicon, such as silicon oxide (SiO), silicon nitride (SiN), silicon carbide (SiC), silicon oxynitride (SiON), silicon oxycarbide (SiOC), silicon carbonitride (SiCN), etc. 
     In various embodiments, hybrid direct bonds can be formed without an intervening adhesive. For example, dielectric bonding surfaces can be polished to a high degree of smoothness. The bonding surfaces can be cleaned and exposed to a plasma and/or etchants to activate the surfaces. In some embodiments, the surfaces can be terminated with a species after activation or during activation (e.g., during the plasma and/or etch processes). Without being limited by theory, in some embodiments, the activation process can be performed to break chemical bonds at the bonding surface, and the termination process can provide additional chemical species at the bonding surface that improves the bonding energy during direct bonding. In some embodiments, the activation and termination are provided in the same step, e.g., a plasma or wet etchant to activate and terminate the surfaces. In other embodiments, the bonding surface can be terminated in a separate treatment to provide the additional species for direct bonding. In various embodiments, the terminating species can comprise nitrogen. Further, in some embodiments, the bonding surfaces can be exposed to fluorine. For example, there may be one or multiple fluorine peaks near layer and/or bonding interfaces. Thus, in the directly bonded structures, the bonding interface between two dielectric materials can comprise a very smooth interface with higher nitrogen content and/or fluorine peaks at the bonding interface. Additional examples of activation and/or termination treatments may be found throughout U.S. Pat. Nos. 9,564,414; 9,391,143; and 10,434,749, the entire contents of each of which are incorporated by reference herein in their entirety and for all purposes. 
     In various embodiments, conductive contact pads of the first element can be directly bonded to corresponding conductive contact pads of the second element. For example, a hybrid bonding technique can be used to provide conductor-to-conductor direct bonds along a bond interface that includes covalently direct bonded dielectric-to-dielectric surfaces, prepared as described above. In various embodiments, the conductor-to-conductor (e.g., contact pad to contact pad) direct bonds and the dielectric-to-dielectric bonds can be formed using the direct hybrid bonding techniques disclosed at least in U.S. Pat. Nos. 9,716,033 and 9,852,988, the entire contents of each of which are incorporated by reference herein in their entirety and for all purposes. 
     For example, dielectric bonding surfaces can be prepared and directly bonded to one another without an intervening adhesive. Conductive contact pads (which may be surrounded by nonconductive dielectric field regions) may also directly bond to one another without an intervening adhesive. In some embodiments, the respective contact pads can be recessed below the dielectric field regions, for example, recessed by less than 20 nm, less than 15 nm, or less than 10 nm, for example, recessed in a range of 2 nm to 20 nm, or in a range of 4 nm to 10 nm. The dielectric field regions can be initially directly bonded to one another without an adhesive and without external pressure at room temperature in some embodiments and, subsequently, the bonded structure can be annealed. Upon annealing, the contact pads can expand and contact one another to form a metal-to-metal direct bond. Beneficially, the use of the hybrid bonding techniques known by the trade name Direct Bond Interconnect, or DBI®, can enable high density of pads connected across the direct bond interface (e.g., small or fine pitches for regular arrays) and/or high density of pads connected across the direct bond interface (e.g., small or fine pitches for regular arrays). In some embodiments, the pitch of the bonding pads may be less 40 microns or less than 10 microns or even less than 2 microns. For some applications the ratio of the pitch of the bonding pads to one of the dimensions of the bonding pad is less than 5, or less than 3 and sometimes desirably less than 2. In various embodiments, the contact pads can comprise copper, although other metals may be suitable. 
     In various embodiments, the contact pads can be formed in respective first and second arrays of pads on the first and second elements. If any debris or surface contaminant is present at the surface of the first or second elements, voids may be created at the bond interface, or debris may intervene between opposing contact pads. In addition, reactant byproducts generated during bonding and annealing, e.g. hydrogen and water vapor, may also form voids at the bond interface. These voids may effectively inhibit the joining of particular contact pads in the vicinity, creating openings or other failures in the bond. For example, any void larger than the pad diameter (or pitch) can potentially create an opening and direct bond failure. 
       FIG. 1A  is a schematic top plan view of a bonded structure  1  showing locations of voids  10 .  FIG. 1B  is a schematic cross sectional view of the bonded structure  1 . The bonded structure  1  has voids  10  between a first element  12  and a second element  14 . The voids  10  can intervene between opposing contact pads  16 ,  18 . The voids  10  can cause faulty interconnects. 
       FIG. 1C  is a schematic cross sectional view of a bonded structure  2  according to an embodiment. The bonded structure  2  can comprise a first element  22  (e.g., a first semiconductor device die) and a second element  24  (e.g., a second semiconductor device die) stacked on and bonded to the first element  22  along a bonding interface  26 . Corresponding dielectric field regions (e.g., a first dielectric field region  28  and a second dielectric field region  30 ) and corresponding contact pads (e.g., first contact pads  16  and second contact pads  18 ) may be directly bonded without an intervening adhesive. The bonded structure  2  can include one or more trace(s)  32  can provide a redundant electrical connection. Thus, in the event of a void or debris (fault  10 ) the traces  32  ensure the desired connection between the elements  22 ,  24 . Although not shown, it will be understood that the contact pads  16 ,  18  each connect internally to circuitry of their respective elements  22 ,  24 , and that the traces ensure redundant connections of multiple pads to such internal circuitry. The bonded structure  2  can include switching circuitry that is connected to the trace(s)  32 . 
     Beneficially, various embodiments disclosed herein can provide circuitry (e.g., switching circuitry) for electrical redundancy such that if a first electrical connection between first and second elements fails, the failed electrical connection can be rerouted or switched through a redundant electrical connection between the first and second elements. The disclosed embodiments can accordingly improve device yield by ensuring that electrical connectivity between stacked dies remains even when one or more interconnection between the elements has failed, e.g., if a void or debris (fault  10 ) is disposed between contact pads of the elements. 
     Having the redundant pads close to one another risks both or all of the redundant pads being affected by the same bonding fault (e.g., void or debris). Spacing redundant electrical interconnects relatively far apart makes it more likely that if one connection is compromised by a bonding fault, a redundant pad can ensure the electrical connection to the other die is not lost. Embodiments disclosed herein can beneficially enable the use of redundant pads at relatively large spacings without significant electrical losses. The use of active circuitry can enable high frequency operation at large distances with little electrical loss. 
     In various embodiments, the bonded structure can include first and second elements (e.g., first and second active integrated device dies) bonded to one another. Each element can comprise corresponding first and second pluralities of contact pads that can be electrically connected to one another to define a plurality of electrical connections along the bonding interface between the first and second elements. The connections can include contacts configured to carry relatively high frequency signals (e.g., greater than about 50 Mhz, greater than about 100 MHz, or greater than 200 MHz). In some embodiments, the connectivity of electrical connections between the first and second elements can be tested to identify one or more failed electrical connections (for example, connections in which a void, debris or other fault is disposed between opposing contact pads). In various embodiments, a boundary scan or built-in self-test (BIST) engine can be used to determine connectivity. For example, the BIST engine can run a boundary scan diagnostic which identifies the faulty connections and verifies that there are functional alternate locations that can work before connections are reassigned or rerouted. An e-fuse or other similar mechanisms, along with non-volatile look-up tables (LUTs) can logically reassign the electrical connections to redundant connections. The reassignment or switching of connections can feed both sides of the connections (at least two dies involved) so that the linkage and connection is completed. 
     Thus, based upon available connectivity, a subset of spare pins or contact pads to be reassigned to the broken interconnects can be identified. The one or more failed electrical connections can be rerouted or reassigned to one or more redundant electrical connections on both sides of the bonding interface (e.g., on both dies) to complete the desired connection between the first and second elements. The reroutings or reassignments can be implemented by switches or multiplexers (MUXes) to re-route the nets. A longer distance can be enabled by reconditioning the signal with flops, redrivers, retimers, inverters, repeaters or similar structures disposed along the route or at the circuitry (e.g., at switching circuitry). By leveraging circuitry such as a switch or a multiplexer, the electrical load of the alternate electrical paths should not consume power other than leakage power, which may occur from the repeaters (or other logic) used to carry the signal to the alternate location. 
     The electrical connectivity of the plurality of electrical connections can be re-tested to verify connectivity of the one or more redundant electrical connections. For example, in some embodiments, the boundary scan can be re-run with the reassignments to validate the self-repair of the failed electrical connection. The embodiments disclosed herein can be used in conjunction with directly bonded structures, as described above, but may also be used with other interconnections, such as copper pillars, solder balls, etc. 
     In  FIG. 1C , the bonded structure  2  employs circuitry in each of first and second elements  22 ,  24  to selectively re-route signals to alternate or redundant contact pads. As explained above, the first and second elements  22 ,  24  can be bonded to one another along a bonding interface  26 . In the illustrated embodiment, the first and second elements  22 ,  24  are directly bonded to one another without an adhesive. For example, as explained above, corresponding first and second dielectric field regions  28 ,  30  of the first and second elements  22 ,  24  may be directly bonded without an adhesive. Corresponding first and second pluralities of contact pads  16 ,  18  of the first and second elements  22 ,  24  may also be directly bonded to one another without an intervening adhesive. For example, the two bonded elements  22 ,  24  can be hybrid bonded such that respective dielectric regions  28 ,  30  are directly bonded without an adhesive and respective contact pads  16 ,  18  are directly bonded without an adhesive. In  FIG. 1C , the first element  22  includes first and second contact pads  16   a ,  16   b  spaced apart from one another. In some embodiments, the first and second contact pads  16   a ,  16   b  can be spaced apart from one another by at least 10 microns, at least 50 microns, or at least 100 microns, for example, in a range of 10 microns to 5 mm, in a range of 10 mm to 1 mm, or in a range of 50 microns to 1500 microns. In some embodiments, the first and second contact pads  16   a ,  16   b  can be spaced apart by at least twice a pitch of the plurality of contact pads  16 , or at least 5 times the pitch. The second element  18  includes third and fourth contact pads  18   a ,  18   b  spaced apart from one another. The third and fourth pads  18   a ,  18   b  can be spaced apart by a spacing similar to that of the first and second pads  16   a ,  16   b . The first and third contact pads  16   a ,  18   a  can be disposed opposite one another and configured to electrically connect to one another. Similarly, the second and fourth contact pads  16   b ,  18   b  can be disposed opposite one another and configured to electrically connect to one another. In other embodiments, conductive adhesives may be used between corresponding contact pads along the bonding interface. 
       FIGS. 2A-2B  illustrate examples of circuitry  3 ,  4  comprising respective bi-directional circuits, including tri-stated interconnections. Reference numerals used in conjunction with  FIGS. 2A and 2B  may represent the same or generally similar components as those of  FIG. 1C , unless otherwise noted. First transmit and receive flip-flops  36 ,  38  can be provided in the first element  22 . Second transmit and receive flip-flops  40 ,  42  can be provided in the second element  24 . The first and second transmit flip-flops  36 ,  40  can comprise transmit transistors, and the first and second receive flip-flops  38 ,  42  can comprise receive transistors. The flip-flops  36 ,  38 ,  40 ,  42  can each comprise a single-transistor flip-flop and/or a multi-transistor flip-flop. An output line  37  of the first transmit flip-flop  36  can be electrically connected at least partially through the trace  32  to an input line  39  of the first receive flip-flop  38  and to the second contact pad  16   b . The input line  39  of the first receive flip-flop  38  is connected to the first contact pad  16   a . An output line  41  of the second transmit flip-flop  40  can be electrically connected at least partially through the trace  32  to an input line  43  of the second receive flip-flop  42  and to the fourth contact pad  18   b . The input line  43  of the second receive flip-flop  42  is connected to the third contact pad  18   a.    
     In various embodiments, if, for example, an electrical connection between the second and fourth contact pads  16   b ,  18   b  is faulty, the signal can be rerouted to a redundant electrical connection between the first and third contact pads  16   a ,  18   a . Similarly, if an electrical connection between the first and third contact pads  16   a ,  18   a  is faulty, the signal can be rerouted to a redundant electrical connection between the second and fourth contact pads  16   b ,  18   b . Therefore, the circuitry  3 ,  4  can have a first state in which an electrical signal is transferred between the first and third contact pads  16   a ,  18   a  and a second state in which the electrical signal is transferred between the second and fourth contact pads  16   b ,  18   b.    
     The circuitry  3 ,  4  can comprise a first tri-state driver  44  and a second tri-state driver  46  that enable tri-stated interconnections. In some embodiments, the first tri-state driver  44  can be positioned between the first transmit flip-flop  36  and the trace  32  that connects the first and second contact pads  16   a ,  16   b . In some embodiments, the second tri-state driver  46  can be positioned between the second transmit flip-flop  40  and the trace  32  that connects the third and fourth contact pads  18   a ,  18   b . The circuitry  4  can comprise a third tri-state driver  48  and a fourth tri-state driver  50 . As shown in  FIG. 2B , in some embodiments, the third tri-state driver  48  can be positioned between the first receive flip-flop  36  and the trace  32  that connects the first and second contact pads  16   a ,  16   b . In some embodiments, the fourth tri-state driver  50  can be positioned between the second receive flip-flop  42  and the trace  32  that connects the third and fourth contact pads  18   a ,  18   b.    
       FIGS. 2C-2D  illustrate another example of circuitry  5 ,  6  that includes a multiplexer (MUX)  54  or demultiplexer (DEMUX)  52  in at least one of the first and second elements. Reference numerals used in conjunction with  FIGS. 2C and 2D  may represent the same or generally similar components as those of  FIGS. 1C-2B , unless otherwise noted.  FIG. 2C  shows a DEMUX device. In  FIG. 2D , a MUX device can be used. The circuitry  5 ,  6  can include a first and second transistors  53 ,  55 . The circuitry  5  can connect the second transistor  55  to an input of the DEMUX  52 , and the circuitry  6  can connect the second transistor  55  to an output of the MUX  54 . As shown in  FIGS. 3A and 3B , the DEMUX  52  and/or MUX  54  in the second element  24  can be configured to select which of first and second electrical paths  56 ,  58  are to be used for a particular electrical signal. One or more repeaters  60  can also be provided along the first and second paths  56 ,  58 . If it is determined that a first electrical connection between first and third pads  16   a ,  18   a  is faulty, for example, the DEMUX  52  and/or MUX  54  can switch to route the electrical signal along the second path  58  to the redundant connection between the second and fourth pads  16   b ,  18   b.    
     In the illustrated embodiments, the DEMUX  52  and the MUX  54  are configured to select between the first and second electrical paths  56 ,  58 , and a 1-to-2 demultiplexer and a 2-to-1 multiplexer are used as the DEMUX  52  and the MUX  54  respectively. However, in some embodiments, the circuitry  5 ,  6  can be configured to select between more than two electrical paths and implement other types of DEMUX and MUX. 
       FIG. 3  illustrates another example of circuitry  7  that includes an AND gate  62  in one or both of the first and second elements  22 ,  24 . Reference numerals used in conjunction with  FIG. 3  may represent the same or generally similar components as those of  FIGS. 1C-2D , unless otherwise noted. Similar to the embodiment of  FIGS. 2C and 2D , if both inputs to the AND gate  62  indicate a good connection, then the electrical signal can be transferred along the second path  58  to the second and fourth pads  16   b ,  18   b  (or the first path  56  to the first and third pads  16   a ,  18   a ). If one of the inputs to the AND gate  62  indicates a faulty connection (e.g., when the second and fourth pads  16   b ,  18   b  have a faulty connection), then the electrical signal can be transferred along the first path  56  to the first and third pads  16   a ,  18   a . Although  FIG. 3  illustrates an AND gate  62 , it should be appreciated that other types of logic gates or active circuitry can be used to switch between electrical pathways to the bonding interface. 
       FIG. 4  illustrates another example of circuitry  8  that includes a hash topology including a plurality of multiplexers (MUX)  54   a ,  54   b ,  54   c ,  54   d ,  54   e  in the first and second elements  22 ,  24 . Reference numerals used in conjunction with  FIG. 4  may represent the same or generally similar components as those of  FIGS. 1C-3 , unless otherwise noted. The hash topology can enable the use of many-to-many interconnections, as opposed to one-to-one or many-to-one. As shown in  FIG. 4 , the first flip-flop  53  can electrically connect to a plurality of multiplexers  54   a ,  54   b ,  54   c , which can receive the electrical signal from the first flip-flop  53 . If the electrical connection along the bonding interface  26  is faulty for one of the plurality of MUX  54   a ,  54   b ,  54   c ,  54   d ,  54   e , then another of the MUX  54   a ,  54   b ,  54   c ,  54   d ,  54   e  can transfer the electrical signal to a corresponding contact pad at the bonding interface  26 . Also, one or a plurality of repeaters  60  can be provided along the signal lines so as to boost or repeat the signal along possibly large distances, which can maintain high signal quality. The use of the hash topology can beneficially increase redundancy for the bonded structure, since each MUX  54   a ,  54   b ,  54   c ,  54   d ,  54   e  can connect to multiple flip-flops  53 ,  55 ,  63 ,  65  on a particular element. 
     For example, for each contact pad, accordingly, there may be more than one redundant pad, which can share signal boosters, flops, retimers, drivers, inverters, etc. Thus, the many-to-many redundancy of  FIG. 4  enables every pin or contact pad to potentially access multiple redundant pads. For example, if there are 100 original pads or pins and 10 redundant pads, then each of the 100 pins can access each of the  10  redundant pads. This example can correct for 10 faults, but any suitable number of redundancies can be provided. For example, in some embodiments, a ratio of a first plurality of operational contact pads to a second plurality of redundant contact pads can be in a range of 2:1 to 15:1, or in a range of 5:1 to 10:1. 
     The foregoing described actively connected redundant pads for signals. In some embodiments, each of the first and second elements  22 ,  24  can comprise corresponding ground and power pads. Passively connected redundant pads can be provided for the ground and power pads. The redundant ground and power pads can be passively connected, for example, without active circuitry along the interconnecting path. Passively connected redundant pads can be spaced apart from the corresponding faulty power or ground pad by at least 10 microns, or at least 50 microns. Passively connected redundant pads can be spaced apart from the corresponding faulty power or ground pad by at least twice a pitch (e.g., twice a minimum pitch) of the contact pads. 
     Beneficially, the embodiments disclosed herein can provide electrical redundancy for connections across a bonding interface  26  between two bonded elements  22 ,  24 . The disclosed embodiments can be used for signals at relatively high frequencies, since active devices (such as repeaters, flops, redrivers, retimers, inverters, etc.) can be provided to recondition the signal, even across relatively large distances. Thus, even for significantly increased point-to-point distances (for example, distances in a range of 0.3 mm to 1 mm, or greater than 1 mm) for a given signal shunted to a redundant pad due to a faulty connection, signal strength at high frequencies can be maintained. In various embodiments, the disclosed embodiments can be operated at frequencies of 50 MHz or greater, 100 MHz or greater, or 200 MHz or greater. 
     The illustrated embodiments accordingly illustrates circuitry  3 ,  4 ,  5 ,  6 ,  7 ,  8  that reroutes signal(s) from one contact pad to another, redundant contact pad. Although the illustrated embodiments show surface pads with various or arbitrary types of internal, lateral connections, the concepts disclosed herein can be applicable to through substrate vias (TSVs), whether the TSVs are internal to the element or pass therethrough. If the TSVs pass completely through a particular element, then the circuitry can provide for switching between outer dies of a stack (e.g., with one or more intervening elements). 
     Thus, in one embodiment, a bonded structure is disclosed. The bonded structure can include a first element having a first plurality of contact pads on a first surface, the first plurality of contact pads including a first contact pad and a second redundant contact pad spaced apart from one another along the first surface. The bonded structure can include a second element bonded to the first element. The second element can have a second plurality of contact pads on a second surface. The second plurality of contact pads can include a third contact pad and a fourth redundant contact pad spaced apart from one another along the second surface. The first contact pad can be disposed opposite to and configured to connect to the third contact pad. The second contact pad can be disposed opposite to and configured to connect to the fourth contact pad. The bonded structure can include circuitry disposed in at least the first element, the circuitry having a first state in which an electrical signal is transferred to the first contact pad and a second state in which the electrical signal is transferred to the second contact pad. 
     In some embodiments, the bonded structure can include second circuitry in the second element, the second circuitry having a first state in which an electrical signal is transferred to the third contact pad and a second state in which the electrical signal is transferred to the fourth contact pad. The circuitry can form at least a portion of a bidirectional tri-stated interconnect structure. The circuitry can comprise a first receive flip-flop and a first transmit flip-flop, an output line of the first transmit flip-flop electrically connected to an input line of the first receive flip-flop and to the second contact pad, the input line of the first receive flip-flop connected to the first contact pad. The second circuitry can comprise a second receive flip-flop and a second transmit flip-flop, an output line of the second transmit flip-flop electrically connected to an input line of the second receive flip-flop and to the fourth contact pad, the input line of the first receive flip-flop connected to the third contact pad. The circuitry can comprise a multiplexer (MUX) or demultiplexer (DEMUX) electrically connected to a first flip-flop, and wherein the MUX or DEMUX is configured to selectively transfer the electrical signal to the first contact pad or the second contact pad. The bonded structure can comprise a second flip-flop in the second element, the MUX or DEMUX configured to transfer the electrical signal to the second flip-flop along a first path through the first contact pad or along a second path through the second contact pad. The circuitry can comprise an AND gate configured to selectively transfer the electrical signal to the first contact pad or the second contact pad. The circuitry can comprise a first plurality of multiplexers (MUX) electrically connected to a first flip-flop in the first element. A first MUX of the first plurality of MUX can be configured to transfer the electrical signal to the first contact pad. The first MUX can be configured to receive the electrical signal from the first flip-flop or a second electrical signal from a second flip-flop in the first element. A second MUX of the first plurality of MUX can be configured to receive the electrical signal from the first flip-flop and to transfer the electrical signal to the second contact pad. The second circuitry can comprise a second plurality of multiplexers (MUX) electrically connected to a second flip-flop. The first plurality of contact pads can be directly bonded to the second plurality of contact pads without an intervening adhesive. The bonded structure can comprise first and second dielectric field regions on the first and second elements, the first and second dielectric field regions directly bonded to one another without an adhesive. A void can be disposed between at least a portion of the first and third contact pads, and wherein the second and fourth contact pads can be physically and electrically contact one another. The first and third contact pads may not be directly electrically connected to one another. The circuitry can be in the second state. The first and second contact pads can be spaced apart by at least 50 microns. The first and second contact pads can be spaced apart by at least twice a pitch of the first plurality of contact pads. 
     In another embodiment, a method of providing electrical connectivity along a bonding interface of a bonded structure including a first element bonded to a second element is disclosed. The method can include testing electrical connectivity of a plurality of electrical connections between the first element and the second element to identify one or more failed electrical connections. The method can include rerouting the identified one or more failed electrical connections to one or more redundant electrical connections between the first and second elements. 
     The method can include re-testing the electrical connectivity of the plurality of electrical connections to verify connectivity of the one or more redundant electrical connections. The first element can be directly bonded to the second element without an intervening adhesive. 
     In another embodiment, a bonded structure is disclosed. The bonded structure can include a first element having a first plurality of operational contact pads and a second plurality of redundant contact pads, wherein the first plurality of operational contact pads includes more contact pads than the second plurality of redundant contact pads. The bonded structure can include a second element bonded to the first element. The second element can have a third plurality of operational contact pads and a fourth plurality of redundant contact pads. The first plurality of operational contact pads can be disposed opposite to and configured to connect to the third plurality of operational contact pads. The second plurality of redundant contact pads can be disposed opposite to and configured to connect to the fourth plurality of redundant contact pads. The bonded structure can include circuitry disposed in at least the first element, the circuitry configured to transfer one or more electrical signals from a first number of pads from the first plurality of operational pads to a second number of pads from the second plurality of redundant pads, the first number greater than the second number. 
     In some embodiments, a ratio of the first plurality to the second plurality and of the third plurality to the fourth plurality can be in a range of 2:1 to 15:1. The ratio of the first plurality to the second plurality and of the third plurality to the fourth plurality can be in a range of 5:1 to 10:1. The first plurality of operational contact pads can comprise signal pads. Each of the first and second elements can further comprise corresponding ground and power pads. The bonded structure can include passively connected redundant pads for the ground and power pads. 
     In another embodiment, a bonded structure is disclosed. The bonded structure can include a first element having a first plurality of through substrate vias (TSVs), the first plurality of TSVs including a first TSV and a second redundant TSV spaced apart from one another. The bonded structure can include a second element stacked on a first side of the first element, the second element having a plurality of contact pads. The plurality of contact pads can include a first contact pad and a second redundant contact spaced apart from one another. The first TSV can be disposed opposite to and configured to connect to the first contact pad. The second TSV can be disposed opposite to and configured to connect to the second contact pad. The bonded structure can include circuitry disposed in at least the second element, the circuitry connecting the first contact pad with the second contact pad, the circuitry having a first state in which an electrical signal is transferred to the first TSV and a second state in which the electrical signal is transferred to the second redundant TSV. 
     In some embodiments, the bonded structure can include a third element stacked on a second side of the first element opposite to the first side. The third element can have a second plurality of contact pads. The second plurality of contact pads can include a third contact pad and a fourth redundant contact pad spaced apart from one another. The third contact pad can be disposed opposite to and configured to connect to the first TSV. The fourth contact pad can be disposed opposite to and configured to connect to the second TSV. The circuitry can be disposed in the first and/or third element. The first state can transfer the electrical signal along the first contact pad, the first TSV and the third contact pad. The second state can transfer the electrical signal along the second contact pad, the second TSV and the fourth contact pad. One or more of the first through fourth contact pads can be connected to TSVs in the first and/or third elements. 
     All of these embodiments are intended to be within the scope of this disclosure. These and other embodiments will become readily apparent to those skilled in the art from the following detailed description of the embodiments having reference to the attached figures, the claims not being limited to any particular embodiment(s) disclosed. Although this certain embodiments and examples have been disclosed herein, it will be understood by those skilled in the art that the disclosed implementations extend beyond the specifically disclosed embodiments to other alternative embodiments and/or uses and obvious modifications and equivalents thereof. In addition, while several variations have been shown and described in detail, other modifications will be readily apparent to those of skill in the art based upon this disclosure. It is also contemplated that various combinations or sub-combinations of the specific features and aspects of the embodiments may be made and still fall within the scope. It should be understood that various features and aspects of the disclosed embodiments can be combined with, or substituted for, one another in order to form varying modes of the disclosed implementations. Thus, it is intended that the scope of the subject matter herein disclosed should not be limited by the particular disclosed embodiments described above, but should be determined only by a fair reading of the claims that follow.