Patent Publication Number: US-2015079733-A1

Title: Three-dimensional system-in-a-package

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a divisional of U.S. patent application Ser. No. 13/097,943, filed Apr. 29, 2011, the disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     For various reasons, it can be desirable to provide microelectronic assemblies which include a plurality of microelectronic elements, e.g., semiconductor chips in the same microelectronic assembly such as a microelectronic package. The microelectronic assembly can then be electrically and mechanically connected with contacts of a circuit panel, such as through solder balls or other mounting means at an external surface thereof. Such microelectronic assemblies can include a dielectric element with contacts thereon. 
     Some microelectronic assemblies incorporate microelectronic elements of different kinds, such as some microelectronic elements which primarily contain logic circuitry and other elements which primarily contain memory arrays, for example. Often, such microelectronic elements have different sizes, i.e., where the major surfaces of at least some of the microelectronic elements have different dimensions. 
     Further improvements can be made in view of the existing technology. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the invention, a microelectronic assembly can include first, second and third substantially planar elements, which can consist essentially of dielectric or semiconductor material, for example, and which may have a coefficient of thermal expansion (“CTE”) of less than 10 parts per million per degree Celsius (“ppm/° C.”). The first element may have a dielectric layer at a first surface thereof and a plurality of electrically conductive elements exposed at the first surface. A second element may at least partly overlie the first element, the second element having a first surface facing away from the first element and a dielectric layer at such first surface. The second element may have a plurality of electrically conductive elements exposed at the first surface of the second element. A third element of the microelectronic assembly can have a plurality of electrically conductive elements exposed at a first surface thereof, the third element having a second surface facing toward the first and second elements. At least one of the first, second or third elements may embody a plurality of active circuit elements. 
     A second electrically conductive element may entirely underlie the second surface of the third element. The second electrically conductive element may have a thickness of less than 10 microns, and may contact and electrically connect respective electrically conductive elements exposed at the first surfaces of the first and second elements. In a particular example, the second electrically conductive element can be formed by plating a metal layer onto a surface of a dielectric layer overlying the first element, the second element, or both, and in openings in the dielectric layer. 
     In accordance with an aspect of the invention, a microelectronic assembly may include first and second substantially planar elements, each having a first surface and an edge surface extending away from the respective first surface, and each of the first and second elements having a dielectric layer exposed at the first surface and a plurality of conductive elements exposed at the first surface. At least one of the first or second elements can be a microelectronic element embodying a plurality of active circuit elements. The second element may at least partly overlie the first surface of the first element, and the first surface of the second element may face away from the first element. 
     A monolithic dielectric region can overlie the first surface and at least one edge surface of at least one of the first and second elements. At least one of the conductive elements may be exposed within an opening of the monolithic dielectric region. At least one second electrically conductive element may overlie and extend along a surface of the monolithic dielectric region remote from the first edge surface and along the at least one edge surface of the at least one first or second element. The second conductive element may extend from the at least one conductive element to a location beyond the at least one edge surface. In a particular example, a third substantially planar element may at least partly overlie the first surface of the second element. 
     A system according to an aspect of the invention may include a structure, e.g., a microelectronic assembly such as described above, and one or more other electronic components electrically connected to the structure. The system may further include a housing, and the structure and other electronic components may be mounted to the housing. 
     In accordance with an aspect of the invention, a method is provided of making a dielectric assembly. Such method can include: forming openings in a dielectric region overlying a first surface of a first element, electrically conductive elements of the first element being exposed within the openings. The method can further include: then depositing a metal onto the dielectric region and into the openings to form second electrically conductive elements contacting the conductive elements and the dielectric region. The method can further include: stacking at least one second element at least partly overlying the first surface of the first element with a bonding layer between the first and second elements, the second element having a first surface facing away from the first element and electrically conductive elements exposed there at; and forming second openings in a second dielectric region overlying a first surface of the second element, electrically conductive elements of the second element being exposed within the second openings. The method can further include depositing a metal onto a surface of the second dielectric region and into the second openings to form third electrically conductive elements contacting the conductive elements of the second element and the second dielectric region, at least one of the third conductive elements directly contacting at least one of the second conductive elements at a location above the first surface of the first element; and may include: stacking at least one third element at least partly overlying the first surface of the second element with a second bonding layer between the second and third elements, the third element fully overlying at least one second and at least one third conductive element. The first, second and third elements can be substantially planar and at least one of the first, second and third elements can be a microelectronic element having a plurality of active circuit elements. 
     In accordance with another aspect of the invention, a method is provided of making a dielectric assembly, which can include: forming a monolithic dielectric region overlying a first surface of a second element and an edge surface extending away from the second element, the second element at least partly overlying a first element; and forming an electrically conductive element extending along a surface of the dielectric region and through an opening in the dielectric region to a contact exposed at the first surface of the second element, the electrically conductive element extending beyond the edge surface of the second element. At least one of the first or second elements may be a microelectronic element embodying active circuit elements. 
     In accordance with another aspect of the invention, a method is provided of making a dielectric assembly. The method can include: forming a dielectric region overlying a first surface of a second element and overlying an edge surface extending away from the second element, the second element at least partly overlying a first element; forming an electrically conductive element extending along a surface of the dielectric region and through an opening in the dielectric region to a contact exposed at the first surface of the second element, the conductive element extending beyond the edge surface of the second element and being electrically connected to the first element; and mounting a third element at least partly overlying the first and second elements and overlying the electrically conductive element, the third element having contacts electrically connected to at least one of the first or second elements. At least one of the first, second or third elements can be a microelectronic element embodying active circuit elements. 
     In accordance with another aspect of the invention, a method is provided of making a dielectric assembly, which can include: forming openings in a dielectric region overlying a first surface of a substantially planar first element, at least some electrically conductive elements of the first element being exposed within the openings; depositing a metal onto a surface of the dielectric region and within the openings to form second electrically conductive elements extending from the at least some first conductive elements onto the surface of the dielectric region; stacking at least one substantially planar second element at least partly overlying the first surface of the first element with a bonding layer between the first and second elements, the second element having a first surface facing away from the first element and first electrically conductive elements exposed thereat; forming second openings in a second dielectric region overlying the first surface of the second element, at least some of the conductive elements of the second element being exposed within the second openings; depositing a metal onto a surface of the second dielectric region and within the second openings to form third electrically conductive elements extending from the at least some first conductive elements of the second element, at least one of the third conductive elements directly contacting at least one of the second conductive elements at a location above the first surface of the first element; and stacking at least one substantially planar third element at least partly overlying the first surface of the second element with a second bonding layer between the second and third elements, the third element fully overlying the at least one second and third conductive elements. At least one of the first, second and third elements may be a microelectronic element having a plurality of active circuit elements, and the first, second and third elements are bonded together using the first and second bonding layers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a sectional view depicting a microelectronic assembly in accordance with an embodiment herein. 
         FIG. 1B  is a top plan view corresponding to the sectional view of  FIG. 1A , wherein the sectional view of  FIG. 1A  is taken through line  1 A- 1 A of  FIG. 1B . 
         FIG. 2  is a sectional view illustrating a method of fabricating a microelectronic assembly in accordance with an embodiment herein. 
         FIG. 3  is a sectional view illustrating a further stage in a method of fabricating a microelectronic assembly in accordance with an embodiment herein. 
         FIG. 4  is a sectional view illustrating a further stage in a method of fabricating a microelectronic assembly in accordance with an embodiment herein. 
         FIG. 5  is a sectional view illustrating a further stage in a method of fabricating a microelectronic assembly in accordance with an embodiment herein. 
         FIG. 6  is a sectional view illustrating a further stage in a method of fabricating a microelectronic assembly in accordance with an embodiment herein. 
         FIG. 7  is a sectional view illustrating a further stage in a method of fabricating a microelectronic assembly in accordance with an embodiment herein. 
         FIG. 8  is a sectional view illustrating a further stage in a method of fabricating a microelectronic assembly in accordance with an embodiment herein. 
         FIG. 9  is a sectional view illustrating a further stage in a method of fabricating a microelectronic assembly in accordance with an embodiment herein. 
         FIG. 10  is a sectional view illustrating a further stage in a method of fabricating a microelectronic assembly in accordance with an embodiment herein. 
         FIG. 11  is a sectional view illustrating a further stage in a method of fabricating a microelectronic assembly in accordance with an embodiment herein. 
         FIG. 12  is a sectional view illustrating a further stage in a method of fabricating a microelectronic assembly in accordance with an embodiment herein. 
         FIG. 13  is a sectional view illustrating a further stage in a method of fabricating a microelectronic assembly in accordance with an embodiment herein. 
         FIG. 14  is a sectional view illustrating a further stage in a method of fabricating a microelectronic assembly in accordance with an embodiment herein. 
         FIG. 15  is a sectional view illustrating a further stage in a method of fabricating a microelectronic assembly in accordance with an embodiment herein. 
         FIG. 16  is a sectional view illustrating a further stage in a method of fabricating a microelectronic assembly in accordance with an embodiment herein. 
         FIG. 17  is a sectional view schematically illustrating a system in accordance with an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     The incorporation of microelectronic elements of different types or sizes in a package poses a particular challenge because the edges of the microelectronic elements may not be aligned. Moreover, the patterns of contacts, e.g., conductive pads, etc. on the microelectronic elements can vary. 
     A microelectronic assembly as further described herein may be a microelectronic package and may incorporate active semiconductor devices in one, two or more of the first, second or third elements to permit cooperative function therein as a system-in-a-package. In an embodiment of the invention, a microelectronic assembly is provided in which an electrically conductive element entirely underlying a substantially planar element (e.g., a dielectric element with contacts thereon, or a microelectronic element such as a semiconductor chip) can electrically connect lower substantially planar elements over which such substantially planar element at least partly lies. Typically, the electrically conductive element is formed by plating a metal element within openings in a dielectric layer that overlies the substantially planar elements and on a surface of the dielectric layer to electrically connect the substantially planar elements. Subsequently, one or more additional substantially planar elements can be placed over the lower substantially planar elements, after which similar processing may be performed for the additional elements.  FIG. 1  illustrates a microelectronic assembly  100  in accordance with an embodiment of the invention. As seen therein, the microelectronic assembly includes a plurality of substantially planar elements, e.g., first element  102 , second elements  112 A,  112 B and third element  122 . Typically, each of the substantially planar elements is flat, rectangular, and thin in relation to the surface dimensions. For example, one or more of the substantially planar elements can be a microelectronic element such as a semiconductor chip embodying active circuit devices, e.g., transistors, among others. Semiconductor chips are flat thin bodies with surfaces typically having dimensions of a few to a few tens of millimeters on each side, and thicknesses typically under one millimeter. In certain examples provided herein, the microelectronic elements have thicknesses of up to 150 microns. Each of the substantially planar elements has a respective first surface  104 ,  114 ,  124 , with a dielectric layer  105 ,  115 ,  125  exposed at such first surface and a plurality of electrically conductive elements  106 ,  116 ,  126 , respectively, exposed at such first surface. As used in this disclosure, a terminal “exposed at” a surface of a dielectric element may be flush with such surface; recessed relative to such surface; or protruding from such surface, so long as the terminal is accessible for contact by a theoretical point moving towards the surface in a direction perpendicular to the surface. 
     As seen in  FIG. 1 , one or more of the second elements  112 A,  112 B may at least partly overlies the first surface  106  of the first element  102 , and the third element  122  may at least partly overlies the first surfaces  116  of the second elements. The first surfaces of the second elements may face away from the first element. The first surface  124  of the third element may face away from the first and second elements, such that a second surface  128  of the third element opposite such first surface  124  faces toward the first and second elements. 
     In a particular example, one or more of the substantially planar elements can be a substrate such as a dielectric element in which the dielectric layer  105 ,  115  or  125  thereof alternatively extends throughout a thickness of such element. In certain examples provided herein, the substrates have thicknesses of up to 150 microns. It is also possible for at least one of the substantially planar elements to be a passive element, which in one example may be an “integrated passives on chip” (“IPOC”) element which can include a layer of semiconductor or dielectric material or both, and can embody a plurality of passive devices. In a particular example, without limitation, one or all of the substantially planar elements can consist essentially of or include at least a layer of a material, e.g., a semiconductor or dielectric material, having a coefficient of thermal expansion of less than 10 parts per million/° C. (hereinafter “ppm/° C.”). 
     Any or all of the first, second and third elements can be electrically connected to one another or to terminals exposed at an exterior of the microelectronic assembly. Electrical interconnection can be provided, for example, by electrically conductive elements which extend within openings in one or more dielectric regions overlying the first surfaces of the first, second or third elements. For example, as seen in  FIG. 1 , a first dielectric region  107  can overlie and be in contact with a first surface  104  of first element, having openings  108  therein through which conductive elements  106  e.g., pads, traces or contacts such as conductive pads, of the first element are exposed. The thickness of the dielectric region  107  typically is 5 to 30 microns. Similarly, a second dielectric region  117  can overlie and be in contact with a first surface  114  of a second element  112 A, having openings  118  therein through which conductive elements  116  such as traces or contacts, e.g., conductive pads of the second element  112 A are exposed. The second dielectric region  117  may also overlie and be in contact with the first surface  114  of second element  112 B, and have openings  118  through which similar conductive elements  116  of that second element  112 B are exposed. Similarly, a third dielectric region  127  can overlie and be in contact with a first surface  124  of a third element  122 , having openings  130  therein through which conductive elements  126  such as traces or contacts, e.g., conductive pads of the third element  122  are exposed. In a particular example, the second elements can be a plurality of elements which are spaced apart from each other in a lateral direction which is parallel to the first surfaces of the second elements. The thicknesses of each dielectric region  107 ,  117 ,  127  can be about the same or comparable, e.g., 5 to 30 microns, or may be different. 
     As further seen in  FIG. 1 , the substantially planar elements typically have edge surfaces  109 ,  119 ,  129  extending away from their first surfaces  104 ,  114 ,  124 . In one embodiment, the dielectric regions  107 ,  117 ,  127  which overlie the first, second or third elements, respectively, can be continuous monolithic dielectric regions. Such monolithic dielectric regions can also overlie and be in contact with the edge surfaces  109 ,  119 ,  129  of the first, second and third elements, respectively. In one example, the monolithic dielectric regions can consist essentially of a material such as polymeric dielectric material which is deposited in liquid form or laminated onto the first and edge surfaces of the corresponding first, second or third elements. 
     The edge surfaces  109 ,  119 ,  129  of the first, second and third elements may or may not be aligned in a vertical plane of the microelectronic assembly, “vertical” being a direction transverse to directions parallel to the first surface  104  of the first element. In a particular example as shown in  FIG. 1A , an edge surface  119  of one or more of the elements, for example, second element  112 A, can be disposed beyond an edge surface of another element, such as edge surfaces  109 ,  120  of the first and third elements  102 ,  122 . 
     A bonding layer  111 , such as an adhesive or other material forming a sufficiently strong bond, for example, can be disposed between the dielectric region overlying a particular element, e.g., the first element  102 , and the next higher element, e.g., the second element  112 A, or the third element  122  above such element. Typically, the bonding layer is a dielectric material and is applied to one or both surfaces to be bonded, e.g., a surface  110  of dielectric region  107  and a second surface  113  of a second element to be bonded thereto. The bonding layer may maintain the first and second elements in fixed positions. In a particular embodiment, the bonding layer  111  can be a B-stage, i.e., partially cured, dielectric material, just as dielectric region  105  can be a B-stage dielectric material. In an exemplary embodiment, dielectric region  107  and bonding layer  111  can both be made of the same B-stage dielectric material when applied to the structure. 
     As seen in  FIG. 1A , one or more second electrically conductive elements  132  can contact and electrically connect respective electrically conductive elements  116 ,  106  which are exposed at the first surfaces  104 ,  114  of the first and second elements, respectively. The second electrically conductive element can extend at least partly along surfaces of the monolithic dielectric region, such as monolithic dielectric region  117 , for example. As further seen in  FIGS. 1A-B , the second conductive element  132  can entirely underlie the second surface  128  of the third element  122 . The second conductive element  132  can be such that the thickness of at least a portion of the second conductive element, i.e., thickness  133  in a direction away from a surface of the dielectric layer  117  can be less than 10 micrometers (hereinafter, microns). 
     In a particular embodiment, although not shown in  FIGS. 1A-B , a second electric conductive element can contact and electrically connect the conductive elements  116 , e.g., conductive pads, which are exposed at respective first surfaces  114  of two or more second elements. 
     In a particular embodiment, the first and second elements are microelectronic elements each of which embodies active circuit elements. The microelectronic assembly may further include a fourth element which embodies a plurality of passive circuit elements, e.g., transistors, diodes, etc. 
     An encapsulant region  134  may overlie the first surface  124  of the third element  122  and define an upper unit surface  136  which is disposed at a height  138  above the first surface  124  of the third element  122 . 
     As further seen in  FIG. 1A , a plurality of lower unit contacts  140  can be exposed at a lower unit surface  142  of the microelectronic assembly, which is a surface  142  remote from the upper unit surface  136 . The lower unit surface  142  can be a surface of a support element  144  or carrier, e.g., a dielectric element such as a polymer tape, resin element, which may or may not be reinforced. In a particular embodiment, the dielectric element can be an epoxy-glass composite such as FR-4 (reinforced fiberglass), or BT resin, etc. One or more of the lower unit contacts  140  may overlie the second surface  103  of the first element. 
     With reference to  FIG. 2 , a method of fabricating a microelectronic assembly according to an embodiment will now be described. As in  FIG. 2 , a plurality of substantially planar first elements  102  can be placed face up on a support element or carrier  144  such as that described above, such that conductive elements  106 , e.g., pads, contacts or traces exposed at a dielectric layer  105  thereon, at first surface  104 , face away from the support element  144 . An additional temporary carrier element  146  may underlie carrier  144 . Various ways are contemplated for forming the dielectric region  107 , which may include one or more of depositing a liquid-phase material onto the first elements, e.g., by dispensing, spin-on, roller coating, screening or stenciling, etc. Alternatively, the dielectric region  107  can be formed by laminating a dielectric film thereon which may be fully or partially cured, e.g., a B-stage material prior to being laminated to the first elements  102  and support element  144 . When the dielectric region  107  is a B-stage material, in one embodiment it may be possible to laminate the material to the first elements  102  without using an adhesive between the first elements  102  and the dielectric region  107 . As seen in  FIG. 3 , this step produces a monolithic dielectric region  107  which overlies the first surfaces  104  and edge surfaces  109 ,  109 A of the first elements  102 . 
     Then, as seen in  FIG. 4 , the dielectric region  107  can be patterned to form openings  108  therein which at least partly expose conductive elements  106 . In an exemplary embodiment, patterning can be performed using a laser to ablate portions of the dielectric region covering the conductive elements. If the dielectric region  107  is a B-stage material, the B-stage material can undergo a curing process, e.g., with drying, heat or both, prior to being patterned. 
     A step of forming second electrically conductive elements  131  ( FIG. 5 ) can now be performed, which can include depositing a metal to contact the conductive elements  106 , the metal extending along the dielectric region  107 . In one example, this step can include forming a conductive seed layer on the dielectric region  107 , e.g., by sputtering or electroless deposition. Then, a photoresist mask can be formed thereon and exposed photolithographically. The photoresist mask then can be used to pattern the seed layer, after which a thicker metal layer can be plated electrolytically onto the part of the seed layer which remains after the patterning step. 
     In one example, the conductive elements  131  can be formed using a process such as described in commonly owned U.S. application Ser. No. 12/842,669, the disclosure of which is incorporated herein by reference. In such process, a sacrificial layer can be provided overlying the dielectric layer which may conform to a contour of the underlying dielectric layer. The process can include forming a groove in at least the sacrificial layer, which may extend along a top surface of the dielectric layer and along at least one sloped surface within openings in the dielectric layer. The groove can extend along the at least the sloped surface or can merge with the opening in the dielectric layer. In one example, the groove can be formed by removing a portion of the sacrificial layer by a method that does not require casting an image upon a photo-imageable material layer using a fixed reticle or photomask. Thus, particular processes can include directing an illumination spot of a laser or a stream of particles towards the sacrificial layer and moving the spot or stream to form the groove. 
     Thereafter, a conductive element can be formed which has cross-sectional dimensions at least partly defined by the groove. In one example, a catalyst or seed layer can be deposited to overlie the sacrificial layer, after which the sacrificial layer can be removed so as to remove the catalyst or seed layer from areas other than within the groove. Thereafter, one or more plating processes can then be used to complete the conductive element by selectively plating a metal onto an exposed portion of a seed layer defined by the above-described processing. 
     The second conductive elements may fully or partially fill the patterned openings  108  ( FIG. 4 ) in the dielectric layer  107  as seen at  150  ( FIG. 5 ), or may extend along interior surfaces of the openings, conforming to contours of interior surfaces of such openings  108 , as seen at  152 . Some of the second conductive elements  131  may electrically connect a plurality of the first elements  102 . 
     As seen in  FIG. 6 , the second, e.g., rear surfaces of a plurality of second elements  112 A,  112 B can be bonded to the underlying dielectric region  107 , with a dielectric material  111  such as an adhesive. In a particular embodiment, the dielectric material can be a B-stage, i.e., partially cured, dielectric material which bonds the rear surfaces  113  of second elements  112 A,  112 B with the dielectric region  107  below. 
     Next, as seen in  FIG. 7 , a second dielectric region  117  can be formed atop the second elements  112 A,  112 B, and patterned ( FIG. 8 ), such as by the processing similar to that described above with respect to  FIGS. 3 and 4 , respectively. However, at locations between edges  119 A between adjacent second elements, openings  118  can be formed in which one or more second conductive elements  131  of the assembly are exposed. 
     Then, additional electrically conductive elements  132  can be formed ( FIG. 9 ) contacting conductive elements  116 , such as by processing similar to that required to form conductive elements  131  as described above ( FIG. 5 ). As seen in  FIG. 9 , the additional conductive elements  132 , together with conductive elements  131 , may electrically connect some conductive elements  106  of the first elements  102  with conductive elements  116  of the second elements. 
     Next, as seen in  FIG. 10 , third elements can be bonded to the underlying structure, such as by one or more of the above-described techniques, e.g., bonding using an adhesive  141  or a B-stage dielectric material between the second surfaces  128  of the third elements  122  and the adjacent dielectric region  117  and conductive elements  132  thereon. 
     Further processing forms a third dielectric region  127  ( FIG. 11 ) overlying the third elements  122 . The dielectric region  127  can then be patterned ( FIG. 12 ) to form openings  129  therein, such as, for example, by laser ablation, among others, as described above. Third electrically conductive elements  151  then can be formed ( FIG. 13 ) within the openings  129 , the conductive elements  151  contacting conductive elements  126 , e.g., pads, contacts or traces, of the third elements  122 . As seen in  FIG. 13 , some ( 151 B) of the third conductive elements can be electrically connected with the second conductive elements  132  so as to electrically connect conductive elements  116 ,  126  on the second and third elements  112 ,  122 , respectively. Others of the third conductive elements ( 151 C) can electrically connect conductive elements  131  of adjacent first elements so as to electrically connect conductive elements  106  on the first elements at a first level of the assembly. In another example, a single conductive element selected from conductive elements  151 B,  151 C, and  151 D depicted in  FIG. 13  may electrically connect two or more substantially planar elements, e.g., two or more of any of elements  102 ,  112 , or  122  at one level of the assembly, any of two different levels, or between any of the different levels of the microelectronic assembly. In a particular example, such conductive element may provide an electrical connection between a first element  102  and a third element  122 , which may or may not also be electrically connected with the second element  112 . 
     As shown in  FIG. 14 , a fourth dielectric region  154 , which can be an encapsulant, can then be formed overlying the third elements  122 , third dielectric region  127  and third conductive elements  151 . In one embodiment, the dielectric region can be molded onto the in-process structure, as by inserting the structure between mold plates (not shown) and injecting an encapsulant into the volume defined by the mold plates. In one example, the encapsulant region can be a solder mask. 
       FIG. 15  illustrates a further stage in which openings  158  can be formed in the fourth dielectric region  154 , in which the third conductive elements  151  can be exposed. 
     Thereafter, as seen in  FIG. 16 , further, fourth conductive elements  161  can be formed which contact the third conductive elements  151  and extend to heights at or adjacent to a plane defined by a surface  162  of the dielectric region  154 , e.g., the encapsulant region. In one example, as seen in  FIG. 16 , the fourth conductive elements include electrically conductive pads  164  exposed at or overlying the surface  162  of the dielectric region. However, as seen at  166 , the fourth conductive elements may simply fill or partially fill the openings in at least the dielectric region  154 . In one example, encapsulant region may further include a solder mask  170  overlying layer  154 , and the fourth conductive elements can function as upper unit contacts exposed within openings in the solder mask  170 . 
     Referring again to  FIGS. 1A-B , in an exemplary embodiment, the temporary carrier  146  can be removed, and the structure depicted in  FIG. 16  can be severed along the periphery of individual first elements, for example. Optionally, to form conductive contacts, e.g., pads at a lower unit surface of the microelectronic assembly  100  ( FIGS. 1A-B ) further patterning and metal deposition, or both can be used to form fifth conductive elements  140  at the lower unit surface  142  which are available at the lower unit surface for electrically interconnecting the microelectronic assembly  100  with an external element, such as a circuit panel, passive component, or other electrical component. 
     The structures discussed above provide extraordinary three-dimensional interconnection capabilities. These capabilities can be used with chips of any type. Merely by way of example, the following combinations of chips can be included in structures as discussed above: (i) a processor and memory used with the processor; (ii) plural memory chips of the same type; (iii) plural memory chips of diverse types, such as DRAM and SRAM; (iv) an image sensor and an image processor used to process the image from the sensor; (v) an application-specific integrated circuit (“ASIC”) and memory. The structures discussed above can be utilized in construction of diverse electronic systems. For example, a system  900  ( FIG. 17 ) in accordance with a further embodiment of the invention includes a structure  906  as described above in conjunction with other electronic components  908  and  910 . In the example depicted, component  908  is a semiconductor chip whereas component  910  is a display screen, but any other components can be used. Of course, although only two additional components are depicted in  FIG. 26  for clarity of illustration, the system may include any number of such components. The structure  906  as described above may be, for example, a microelectronic assembly  100  as discussed above in connection with  FIGS. 1A-B . In a further variant, both may be provided, and any number of such structures may be used. Structure  906  and components  908  and  910  are mounted in a common housing  901 , schematically depicted in broken lines, and are electrically interconnected with one another as necessary to form the desired circuit. In the exemplary system shown, the system includes a circuit panel  902  such as a flexible printed circuit board, and the circuit panel includes numerous conductors  904 , of which only one is depicted in  FIG. 17 , interconnecting the components with one another. However, this is merely exemplary; any suitable structure for making electrical connections can be used. The housing  901  is depicted as a portable housing of the type usable, for example, in a cellular telephone or personal digital assistant, and screen  910  is exposed at the surface of the housing. Where structure  906  includes a light-sensitive element such as an imaging chip, a lens  911  or other optical device also may be provided for routing light to the structure. Again, the simplified system shown in  FIG. 17  is merely exemplary; other systems, including systems commonly regarded as fixed structures, such as desktop computers, routers and the like can be made using the structures discussed above. 
     As these and other variations and combinations of the features discussed above can be utilized without departing from the present invention, the foregoing description of the preferred embodiments should be taken by way of illustration rather than by way of limitation of the invention. 
     Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.