Abstract:
A 3D stacked multichip module comprises a stack of W IC die. Each die has a patterned conductor layer, including an electrical contact region with electrical conductors and, in some examples, device circuitry over a substrate. The electrical conductors of the stacked die are aligned. Electrical connectors extend into the stack to contact landing pads on the electrical conductors to create a 3D stacked multichip module. The electrical connectors may pass through vertical vias in the electrical contact regions. The landing pads may be arranged in a stair stepped arrangement. The stacked multichip module may be made using a set of N etch masks with 2 N-1  being less than W and 2 N  being greater than or equal to W, with the etch masks alternatingly covering and exposing 2 n-1  landing pads for each mask n=1, 2 . . . N.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a division of U.S. patent application Ser. No. 13/451,411, filed 19 Apr. 2012, entitled METHOD FOR CREATING A 3D STACKED MULTICHIP MODULE. 
     This application is related to the following U.S. patent applications: U.S. patent application Ser. No. 13/049,303, filed 16 Mar. 2011, entitled REDUCED NUMBER OF MASK FOR IC DEVICE WITH STACKED CONTACT LEVELS; and U.S. patent application Ser. No. 13/114,931, filed 24 May 2011, entitled MULTILAYER CONNECTION STRUCTURE AND MAKING METHOD. 
    
    
     BACKGROUND OF THE INVENTION 
     One type of three-dimensional integrated circuit (3D IC) is made using a number of semiconductor die stacked vertically and bonded to create the individual 3D ICs. Electrical connections from external bond pads to electrical conductors of the 3D ICs, and between electrical conductors of different layers of the 3D ICs, can be made using various methods. For example, in one wirebonding method the edges of adjacent chips can be staggered in a stair step fashion. This permits external bonding wires to be connected between pads on the chip and pads on a substrate. 
     Another method for making electrical connections between stacked chips, called through-silicon via (TSV), has generated significant interest. Interconnecting stacked chips by TSV has several advantages over conventional external wirebonding techniques. A stacked chip with TSV can exhibit a wider bandwidth and thus greater input/output compared to stacked chips connected via external wirebonding techniques. With TSV there is a shorter connection path which enhances speed and lowers power consumption. 
     TSV can be accomplished using wafer scale stacking with the aligned die separated or diced later. This provides for lower-cost, high throughput but it suffers from yield problems because the failure of one chip in a stack of chips causes that stack to fail resulting in lower yields. In addition, handling thinned down wafers is a manufacturing challenge that can result in damaged or destroyed product. TSV can also be accomplished using die scale stacking. This has the advantage that handling is relatively easy but at the expense of high cost. 
     Another disadvantage of conventional TSV is that a typical TSV process requires 11 steps for each die or wafer: TSV photoresist deposition, TSV etching, silicon dioxide deposition, barrier seed deposition, photoresist patterning, Cu/W deposition, photoresist removal, Cu/W chemical mechanical polishing, support/handling die bonding, die thinning, and bonding. In addition to the time and expense required for all the steps, the required handling and processing of each die results in lower yields. 
     BRIEF SUMMARY OF THE INVENTION 
     An example of a three-dimensional stacked multichip module comprises a stack of W integrated circuit die. Each die in the stack has a patterned conductor layer over a substrate. The patterned conductor layer includes an electrical contact region, the electrical contact region includes electrical conductors. At least one of the electrical conductors includes a landing pad. The stack of die comprises a first die at one end of the stack and a second die at the other end of the stack, the substrate of the first die faces the patterned conductor layer of the second die. The landing pads on each die are aligned with those on the other die in the stack. Electrical connectors extend from a surface of the stack of die and into the stack of die to electrically contact the landing pads to create a three-dimensional stacked multichip module having W die levels, W being an integer greater than 1. Other examples may also include one or more the following. The electrical connectors directly contact the landing pads. At least some of the die comprise device circuitry at a device circuitry location spaced apart from the electrical contact region. A material layer is over the patterned conductor layer of the first die. The electrical connectors pass through vertical vias in the electrical contact regions. Each electrical connector is electrically connected to one landing pad of one die level. The landing pads electrically contacted by the electrical connectors are arranged in a stair stepped arrangement. 
     An example of a three-dimensional stacked multi-wafer module includes a stack of integrated circuit wafers, each integrated circuit wafer comprising a grid of die regions. At least some of the die regions for each integrated circuit wafer are aligned with die regions of the other integrated circuit wafers of the stack of integrated circuit wafers. Each die region comprising a three-dimensional stacked multichip module described in the paragraph above. 
     An example of a first method for creating a three-dimensional stacked multichip module is carried out as follows. A set of W integrated circuit die are provided. Each die in the set includes a patterned conductor layer. The patterned conductor layer includes an electrical contact region, the electrical contact region comprising landing pads. A handling die is mounted to a selected die in the set. An exposed layer of the selected die is removed to create an enhanced handling die. The mounting and removing steps, using the enhanced handling die in each iteration, are repeated. This is carried out so that the landing pads on each die are aligned with those on the other die in the set, until all the die in the set are mounted, to create a three-dimensional stacked die. Connectors are formed from a surface of the module though the three-dimensional stacked die to contacts in the aligned landing pads in each die in the set. Doing so creates a three-dimensional stacked multichip module having W die levels. 
     Examples of the first method may also include one or more the following. The forming step is carried out with at least some of the die comprising device circuitry at a device circuitry location spaced apart from the electrical contact region. The mounting step further comprises depositing a dielectric, adhesion-enhancing layer between the handling die and the die. The die is selected so that it comprises a substrate having a first side, at which the patterned conductor region is located, and a second side opposite the first side, the exposed layer being removed from the second side of the substrate. At least a portion of the handling die is removed from the three-dimensional stacked multichip module to create an exposed surface. Contact openings are created in the surface, the contact openings overlying a landing pad of an electrical conductor for each die level; a set of N etch masks are selected with N being selected so that 2 N-1  is less than W and 2 N  is greater than or equal to W; the N masks are used to etch the contact openings to the W die levels, the N masks using step comprising etching 2n −1  die levels for effectively half of the contact openings for each mask n=1, 2 . . . N; and whereby electrical conductors can be formed in the contact openings to contact the electrical conductor elements at each of the die levels. The surface is covered with a dielectric material following the handling die removing step; and the contact openings creating step includes removing at least a portion of the dielectric material. The N etch masks using step further comprises alternatingly covering and exposing 2n−1 landing pads for each mask n=1, 2 . . . N. 
     A second method for creating a plurality of three-dimensional stacked multichip modules is carried out as follows. A set of W integrated circuit wafers is provided. Each wafer in the set includes a grid of die regions. Each die region has an integrated circuit die comprising a patterned conductor layer, the patterned conductor layer including an electrical contact region. The electrical contact region has landing pads. A handling wafer is mounted to a selected wafer in the set, over the patterned conductor layers. An exposed layer of the selected wafer is removed to create an enhanced handling wafer. The mounting and removing steps are repeated using the enhanced handling wafer in each iteration, and so that the landing pads on each die are aligned with those on the other die in the set of integrated circuit wafers, until all the wafers in the set are mounted. This creates a three-dimensional stacked wafer comprising a grid of three-dimensional stacked die. Connectors from a surface of the three-dimensional stacked wafer to contacts in the aligned landing pads are formed to create a grid of three-dimensional stacked multi-chip modules. The grid of three-dimensional stacked multi-chip modules are physically separated into individual three-dimensional stacked multi-chip modules. 
     Examples of the second method may also be carried out with the connectors forming step carried out as follows. Contact openings are created through said surface of the three-dimensional stacked wafer, the contact openings overlying landing pads of electrical conductors for each die level of a plurality of the three-dimensional stacked multi-chip modules. A set of N etch masks is selected with N being selected so that 2 N-1  is less than W and 2 N  is greater than or equal to W. The N masks are used to etch the contact openings to the W die levels by etching 2 n-1  die levels for effectively half of the contact openings for each mask n=1, 2 . . . N. Electrical conductors can be formed in the contact openings to electrically contact landing pads at each of the die levels. Examples of the second method may also be carried out so that the N etch masks using step further comprises alternatingly covering and exposing 2 n-1  landing pads for each mask n=1, 2 . . . N. 
     Other features, aspects and advantages of the present invention can be seen on review the figures, the detailed description, and the claims which follow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a simplified enlarged cross-sectional view of a portion of a die suitable for creating a 3D stacked multichip module illustrating the electrical contact region and device circuitry both within a patterned conductor layer, the device circuitry shown schematically and at a reduced scale, the device circuitry spaced apart from the electrical contact region. 
         FIG. 2  shows the structure of  FIG. 1  after a handling die has been mounted to the patterned conductor layer of the die of  FIG. 1 . 
         FIG. 3  shows the structure of  FIG. 2  after a lower portion of the substrate of the die of  FIG. 2  has been removed to create an enhanced handling die. 
         FIG. 4  shows the structure of  FIG. 3  after the structure of  FIG. 3  has been mounted on top of a further die, the further die being similar to the die of  FIG. 1 . 
         FIG. 5  shows the structure of  FIG. 4  after a lower portion of the substrate of the die has been removed to create a stacked die. 
         FIG. 6  shows the results of repeating the processing steps of  FIGS. 4 and 5  creating a first 3D stacked die. 
         FIG. 7  shows the structure of  FIG. 6  after the removal of at least a portion of the handling die of  FIG. 6  creating a second 3D stacked die including an exposed surface. 
         FIG. 8  shows the structure of  FIG. 7  after a dielectric material has been deposited on the exposed surface to create a third 3D stacked die. 
         FIGS. 9-18  show a sequence of steps used to create vertically oriented electrical connectors in contact with the horizontally oriented electrical conductors at the different levels. 
         FIG. 9  shows the structure of  FIG. 8  after creating openings in the dielectric material aligned with the ground conductor and electrical conductor locations. 
         FIG. 10  illustrates the result of using a first photoresist mask and etching through one layer. 
         FIG. 11  illustrates results of using a second photoresist mask and etching through two layers. 
         FIG. 12  shows a third photoresist mask and results of etching through four layers creating vias extending down to each level. 
       In  FIG. 13  the third photoresist mask has been removed followed by etching of the vias. 
         FIG. 14  shows result of lining the etched vias with a dielectric material. 
         FIG. 15  illustrates a fourth photoresist mask covering the lined etched vias of  FIG. 14  but exposing a ground conductor location and the result of etching through the levels down to the lowest conductor level. 
         FIG. 16  shows result of an isotropic etching of substrate layers followed by the removal of the fourth photoresist mask. 
         FIG. 17  illustrate an electrically insulating material deposited into the recessed regions formed in the step of  FIG. 16  followed by etching back of the exposed dielectric material to create an enlarged ground conductor via. 
         FIG. 18  shows the structure of  FIG. 17  after filling the vias with a suitable electrical conductor to create a three-dimensional stacked IC assembly together with contact pads and a handling die on top of the stacked IC assembly. 
         FIGS. 19 ,  20  and  21  are simplified plan views of three examples of a die including one or more electrical contact regions and one or more regions with device circuitry. 
         FIG. 22  is a top plan view of an IC wafer with a grid lines indicating die regions. 
         FIG. 23  is a side cross-sectional view of one of the die from the wafer of  FIG. 22 . 
         FIG. 24  illustrates an example in which four different wafers each having 90% good die and 10% bad die. 
         FIG. 25  illustrates results of stacking the four wafers of  FIG. 24  with an indication of the number of good die within each die region having at least one bad die. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description will typically be with reference to specific structural embodiments and methods. It is to be understood that there is no intention to limit the invention to the specifically disclosed embodiments and methods but that the invention may be practiced using other features, elements, methods and embodiments. Preferred embodiments are described to illustrate the present invention, not to limit its scope, which is defined by the claims. Those of ordinary skill in the art will recognize a variety of equivalent variations on the description that follows. Like elements in various embodiments are commonly referred to with like reference numerals. 
     The present invention can be carried out using wafer scale stacking or die scale stacking. In  FIGS. 1-21 , the invention will generally be described in terms of die scale stacking. The additional advantages which accrue from carrying out the invention using wafer scale stacking are described in the description of the present invention with respect to  FIGS. 22-25 . Like reference numerals will be typically used when referring to like elements of dies and wafers. 
       FIG. 1  is a simplified enlarged cross-sectional view of an IC die  12  suitable for creating a 3D stacked multichip module as discussed below. Die  12  of  FIG. 1  illustrates an electrical contact region  18  and schematically illustrates active device circuitry  20  for die  12 , both within a patterned conductor layer  22 . Patterned conductor layer  22  includes a dielectric layer  26  overlying and supported by a substrate  28  of die  12 . Substrate  28  is typically silicon. Electrical contact region  18  includes a number of electrical conductors  24 , typically made of a suitable metal such as copper or tungsten. Dielectric layer  26  is typically an oxide such as SiO 2 . Electrical conductors  24  and device circuitry  20  are, in this example, formed in dielectric layer  26  and are spaced apart from one another by the material of dielectric layer  26 . The active device circuitry  20 , which includes circuits for the mission function of the die, is preferably spaced apart from the electrical contact region  18  and thus does not underlie electrical contact region  18 . The active device circuitry  20  can comprise a flash memory circuit, another type memory circuit, an application specific circuit, a general purpose processor, a programmable logic device, combinations of circuit types as in a system of a chip device, and combinations of these and other types of circuits. In  FIG. 1 , active device circuitry  20  is illustrated as a relatively small element only for the purpose of the drawing. The relative size compared to the contact region  18  depends on the particular implementation. 
       FIG. 2  shows the die  12  of  FIG. 1  after a hard mask layer  30  has been deposited on the upper surface  32  of patterned conductor layer  22  of  FIG. 1 . Hard mask layer  30  is an optional dielectric layer used for isolation and enhanced adhesion. A handling die  34  is mounted to hard mask layer  30  of die  12 . Handling die  34  is preferably sufficiently thick and strong to help prevent damage to the underlying die  12 , and subsequently added die  12 , during the subsequent processing steps. Handling die  34  is typically a bare Si die. When wafer scale stacking is used, a handling wafer is mounted to wafer  12 . 1 , typically on a hard mask layer corresponding to hard mask layer  30  applied to wafer  12 . 1 . The handling wafer is preferably sufficiently thick and strong to help prevent damage to the underlying wafer  12 . 1 , and subsequently added wafers  12 . 1 , during the subsequent processing steps. The handling wafer is typically a bare Si wafer. 
       FIG. 3  shows the structure of  FIG. 2  after a lower portion  36 , see  FIG. 2 , of the substrate  28  of the die  12  of  FIG. 2  has been removed to create an enhanced handling die  38  having a lower, bonding surface  40  on the remaining substrate  41 . This die thinning step can be undertaken because of the strength provided to the underlying die  12  by handling die  34 . During wafer scale operations, these operations would result in creation of an enhanced handling wafer corresponding to enhanced handling die  38 . 
       FIG. 4  shows the enhanced handling die  38  of  FIG. 3  mounted on top of a further die  42 . Further die  42  is similar to the die  12  of  FIG. 1  but preferably includes hard mask layer  30  formed on upper surface  32  of patterned conductor layer  22 . Lower surface  40  of enhanced handling die  38  is mounted to hard mask layer  30  of further die  42 . Similarly, during wafer scale operations, the lower surface of the enhanced handling wafer is mounted to the hard mask layer of the further wafer. 
       FIG. 5  shows the structure of  FIG. 4  after the lower portion  36 , see  FIG. 4 , of the substrate  41  of each of the die  12  has been removed to create a stacked die  46 .  FIG. 6  shows the results of repeating the processing steps of  FIGS. 4 and 5  using additional further die  42  to create a first 3D stacked die  48 . One advantage resulting from reducing the thickness of stacked die  46  is that the depth of the via that must be etched and then filled, see  FIGS. 9-18 , is reduced. This simplifies manufacturing because increasing the depth of the via often requires increasing the diameter of the via. In practice, the vias may be tapered and the technology for filling the vias become limiting with large aspect ratios (depth divided by the width of the via). During wafer scale operations, a stacked wafer is created in a similar manner followed by creation of a first 3-D stacked wafer. 
       FIG. 7  shows the first 3D stacked die  48  of  FIG. 6  after the removal of at least a portion of the handling die  34  of  FIG. 6  creating a second 3D stacked die  50  with an exposed surface  52 .  FIG. 8  shows the structure of  FIG. 7  after a dielectric material  54  has been deposited on the exposed surface  52  to create a third 3D stacked die  56 . Likewise, during wafer scale operations, the second 3-D stacked wafer and the third 3-D stacked wafer  56 . 1 , see  FIG. 25 , are created.  FIGS. 9-18  illustrate a sequence of steps creating electrical connectors  60 , shown as a part of stacked multichip module  61  in  FIG. 18 , in contact with electrical conductors  24 . Electrical connectors  60  connect the landing pads  98  of electrical conductors  24  at the different levels to contact pads  62 . The different electrical connectors  60  are identified in  FIG. 18  as electrical connectors  60 . 0  through  60 . 7  with the left most being  60 . 0 . The locations for the electrical connectors  60  for contact with the corresponding electrical conductors  24  are labeled  0  through  7  in the figures. The position labeled GC identifies the location of ground connector  64  which typically electrically contacts electrical conductors  24  at each level. While only one electrical connector  60  is shown to contact an electrical conductor  24  at each level, in practice, many different electrical connectors  60  would be used to contact electrical conductors  24  at the same level. During wafer scale operations, the same basic processing steps are used on a third 3-D stacked wafer  56 . 1  to create an array of stacked multichip modules  61 . 
       FIG. 9  shows the structure of  FIG. 8  after creating an initial-processing photoresist mask  57  on dielectric material  54  followed by etching through dielectric material  54  down to hard mask layer  30 . This creates openings  58  aligned with ground conductor location GC and electrical conductor locations  0 - 7 . 
     A first photoresist mask  66 , shown in  FIG. 10 , is created on the structure of  FIG. 9  except for openings  58  at electrical conductor locations  1 ,  3 ,  5  and  7 . These openings, which are aligned with the electrical conductors  24 , are then etched one level through hard mask layer  30 , electrical conductors  24  at the first, topmost levels  68 , dielectric layer  26  and the silicon substrate  41  stopping just above electrical conductors  24  at the second level  70 . While electrical connectors  60  are shown in the figures to be aligned in a row, other layouts are possible. For example, electrical connectors  60  could be arranged in a number of parallel or transversely extending rows. For example, electrical contact region  18  of  FIG. 1  could include two or more rows of electrical connectors  60 . 
     Next, as shown in  FIG. 11 , first photoresist mask  66  is removed and then a second photoresist mask  72  is formed on the resulting structure of  FIG. 10  to cover ground conductor locations GC, electrical conductor locations  0 ,  1 ,  4 ,  5 , and following location  7 . The etching of two levels proceeds as follows. The portions of the resulting structure underlying locations  2  and  6  are etched two levels through first and second levels  68 ,  70  down to the electrical conductors  24  at those levels. The portions of the resulting structure underlying locations  3  and  7  are etched two levels through second and third levels  70 ,  74  down to the electrical conductors  24  at those levels. Doing so creates the structure shown in  FIG. 11 . 
     Next, second photoresist mask  72  is removed and a third photoresist mask  78  is formed to cover ground conductor location GC, electrical conductor locations  0 ,  1 ,  2 ,  3 , and following location  7 . The exposed portions of the structure overlying locations  4 ,  5 ,  6  and  7  are then etched four levels, that is down to fifth level  80 , sixth level  82 , seventh level  84  and eighth level  86  at locations  4 ,  5 ,  6  and  7 , respectively, to create vias  77  in the structure of  FIG. 12 . 
     Third photoresist mask  78  is then removed followed by an isotropic etch of the exposed portions of substrates  41  at vias  77  to create recessed regions  88 . See  FIG. 13 . An isotropic etch of electrical conductors  24  at vias  77  is then conducted to create conductor recessed regions  90  along the vias  77 . These etching steps create modified vias  92 . 
       FIG. 14  shows the results of lining modified vias  92  with a dielectric material  94 , such as an oxide material  94 , thus filling in recessed regions  88 ,  90  with the oxide material  94 . Oxide material  94  could be, for example, SiN. The resulting vias  96  are extended to open onto the portions of the underlying electrical conductors  24  acting as landing pads  98 . 
       FIGS. 15-17  show processing steps used to form the electrical conductors  60  and ground conductor  64  shown in  FIG. 18 . In  FIG. 15 , a fourth photoresist mask  100  is shown covering everything except for ground conductor location GC.  FIG. 15  also shows the result of etching through first through seventh levels  68 ,  70 ,  74 ,  76 ,  80 ,  82 ,  84  and down to electrical conductor  24  at eighth level  86  creating a ground conductor via  102 .  FIG. 16  shows result of an isotropic etching of substrates  41  at ground conductor via  102  to create recessed regions  104  opening onto ground conductor via  102 . This is followed by the removal of fourth photoresist mask  100 . 
       FIG. 17  illustrates the result of depositing an electrically insulating material  106 , such as an organic material, for example a polymer, within recessed regions  104 . In addition, the exposed dielectric material at layers  26  is etched back to create an enlarged ground conductor via  108 . This causes an increase in the exposed sidewall contact surfaces of the electrical conductors  24  through which enlarged ground conductor via  108  passes. 
       FIG. 18  illustrates the structure of  FIG. 17  following filling resulting vias  96  and enlarged ground conductor via  108  with a metal or other suitable electrical conductor to create ground connector  64  and electrical connectors  60 . 0 - 60 . 7 . Doing so also creates three-dimensional stacked multichip module  61 . Multichip module  61  is shown with contact pads  62  captured between multichip module  61  and a structure  110 . The structure  110  could be, for example, a handling die or a die with active components, such as memory elements or logic devices, or a combination thereof, due to the flexibility provided by the technology. When structure  110  includes active components, structure  110  could be interconnected with stacked multichip module  61  through electrical connections to contact pads  62  and thus electrical connectors  60 . Ground conductor  64  and electrical conductors  60  are lengths of substantially homogeneous electrically conductive material. By substantially homogeneous, it is meant herein that the conductors  60  lack physical boundaries between the levels. The conductors  60  are substantially homogeneous as used herein even if the conductive material used to form them includes multiple layers of different materials deposited in the vias, which may vary in relative concentration in each level as a result of the manufacturing process. This is in contrast to the electrical connectors formed by conventional TSV processes in which the electrical connectors within the individual via of each layer are separately formed and then are electrically connected to one another when the chips or wafers are stacked and bonded to one another, forming seams often with a separate conductive material joining the opposed electrode conductors. 
     While the die  12  used to form first 3D stacked die  48  of  FIG. 6  could have electrical conductors  24  at different positions and patterns on the individual die, it may be preferred that the positions and patterns for electrical conductors for each die  12  be the same to facilitate manufacturing processes. In particular, it is typically desired that landing pads  98  at each level be aligned. 
     The above-described process for creating electrical connectors  60  can be referred to as a binary process, based on 2 0  . . . 2 n-1  with n being the number of etching steps. That is, first photoresist mask  66 , see  FIG. 10 , alternatingly covers 2 0  landing pads  98  and exposes 2 0  landing pads  98 ; second photoresist mask  72 , see  FIG. 11 , alternatingly covers 2 1  landing pads  98  and exposes 2 1  landing pads  98 ; third photoresist mask  78 , see  FIG. 12 , alternatingly covers 2 2  landing pads  98  and exposes 2 2  landing pads  98 ; and so on. Using this binary process, n masks can be used to provide access to 2 n  landing pads  98  for 2 n  electrical conductors  24  at 2 n  levels. Thus, using 3 masks provides access to 8 landing pads  98  for 8 electrical conductors  24  at 8 levels. Using 5 masks would provide access to 32 landing pads  98  for 32 electrical conductors  24 . The order of etching need not be in the order of n−1=0, 1, 2 . . . . For example, the first etching step could be with n−1=2, the second could be with n−1=0, and the third could be with n−1=1. The result will be the same structure as shown in  FIG. 12 . During typical operations half of the contact openings are etched during each etching step. When the number of levels which can be etched is equal to or greater than the number of levels which are etched, such as when five photoresist masks are used to etch 29 contact openings to reach 29 different landing pads  98 , the masks will not all be used to etch to half of the contact openings, but rather will be used to etch to what will be referred to as effectively half of the contact openings. 
     Further information on techniques and methods for connecting electrical connectors  60  to landing pads  98  of electrical conductors  24  are disclosed in co-pending U.S. patent application Ser. No. 13/049,303, filed 16 Mar. 2011, entitled REDUCED NUMBER OF MASK FOR IC DEVICE WITH STACKED CONTACT LEVELS; and in U.S. patent application Ser. No. 13/114,931, filed 24 May 2011, entitled MULTILAYER CONNECTION STRUCTURE AND MAKING METHOD, the disclosures of which are incorporated by reference. These two applications have a common assignee with the present application. 
       FIGS. 19-21  are simplified plan views of three examples of die  12 , each with one or more electrical contact region  18  and one or more regions of active device circuitry  20 . The die  12  may all be the same or they could be different. For example, logic die such as CPU or controllers, could be used with memory die. In the example of  FIG. 18 , active device circuitry  20  constitutes a major portion of die  12  while electrical contact region  18  is positioned along one edge of die  12 . In the example of  FIG. 19 , electrical contact region  18  is found at three different locations along three different sides of active device circuitry  20 . In  FIG. 20 , there are two regions of active device circuitry  20  separated, in this example, by a single electrical contact region  18 . It is expected that each die  12  will have many electrical contact regions like region  18  because one of the benefits of the stacked process is shorter connection path than with stacked chips using, for example, external bonding pads and connecting wires. It is expected that a minimum distance, such as 2 μm, be maintained between the one or more electrical contact regions  18  and active device circuitry  20 . Such a minimum distance is likely to be required because of stresses induced by the process. Therefore, in some embodiments, the devices in one or more levels can include a wide I/O structuring, including many connectors, such as a hundred or more, between the levels. In other embodiments, fewer connectors between the levels are used. 
     An advantage of this invention is that it can be employed to create a three-dimensional, stacked multichip module, such as one including three-dimensional stacked memory devices, while drastically reducing the time and expense associated with the steps required to create conventional TSV stacked semiconductor devices. In addition, the invention reduces the required handling and processing of each die in comparison with conventional TSV procedures which can lead to improved yields. In addition to providing a thinner device, which is important for devices such as cell phones, the reduction in the thickness of the resulting stack of die  12  by the removal of lower portions  36  has several advantages. These advantages include reducing the length of the electrical connectors coupling electrical connectors  24  to one another and to landing pads  98 , thus reducing the resistance and associated heat loss, and increasing speed. 
     The invention can be carried out using die scale stacking procedures, such as those discussed above, and can also be carried out using wafer scale stacking procedures which results in additional advantages discussed below.  FIG. 22  is a top plan view illustrating an integrated circuit wafer  120  with grid lines  122  indicating die regions  123  where individual die  12  will be created from wafer  120 .  FIG. 23  shows a simplified cross-sectional view of a typical die  12 , substantially identical to die  12  of  FIG. 1 , from location C- 7  on wafer  120 . In this example there are a total of 50 die  12  to be created from wafer  120 . For purposes of illustration, it is assumed that 5 of the die  12  are defective or bad die  124  as indicated by being crosshatched in  FIG. 22 . In this case 90% of the die on wafer  120  would be good die  126  while 10% of die  120  would be bad die  124 . 
       FIG. 24  illustrates an example in which four different IC wafers  120  each have 50 die regions  123  with 10% of die regions  123  being bad. If the IC wafers  120  are individually diced, then the good die can be selected and stacked using a die scale stacking technique resulting in a 90% yield for the stacked multichip modules  61 . However, the need to individually process each multichip module  61  using die scale stacking techniques makes the processing much more expensive than processing on a wafer scale in which all 50 stacked multichip modules  61  are processed in unison. 
     IC wafers  120  of  FIG. 24  are stacked to produce the third 3-D stacked wafer  56 . 1  of  FIG. 25 . Stacked wafer  56 . 1  has 15 of the die regions  123  marked with either a 2, indicating two out of the four stacked die are good die, or 3, indicating three out of the four stacked die are good die. No marking indicates that all levels are good die. If the four different IC wafers  120  are stacked, bonded to one another, diced and then processed in a conventional manner, such as using wirebonding techniques or TSV, each stacked multichip module with even one bad die would cause that stacked multichip module to be rejected as defective because all of the die need to be good for the stacked multichip module to be good. In this example the yield would be only 70% good stacked multichip modules, that is 35 out of 50. This technique would, however, eliminate the processing expenses associated with die scale stacking and processing techniques discussed in the paragraph immediately above. 
     With the present invention the stacked multi-die modules  61  which are partially defective can be segregated as non-perfect die. For example, if each die  12  is one core of a CPU, the non-perfect module  61  can be identified as a two core module  61  if there are two good die  12  or a three core module  61  if there are three good die  12 . Similarly, if each die is a 1 GB memory die, the non-perfect modules  61  can be marked as 3 GB memory modules or 2 GB memory modules as the case may be. In this example there would be 35 good stacked multichip module  61  but also 5 non-perfect modules  61  with two good die  12  and 10 non-perfect modules  61  with three good die  12 . The interconnection technology described herein enables isolation of the defective die in the stack, because of the individual connectors reaching to a single landing pad on one level of the stack. During the manufacturing process to stack the die and make the connectors, the defective die can be isolated from operable die, in one approach, using masks for the formation of the connectors that are selected according to the number and locations of the defective die in each stack. Being able to salvage the non-perfect module  61  helps to reduce cost over conventional wafer scale processing techniques. 
     The above descriptions may have used terms such as above, below, top, bottom, over, under, et cetera. These terms may be used in the description and claims to aid understanding of the invention and not used in a limiting sense. 
     While the present invention is disclosed by reference to the preferred embodiments and examples detailed above, it is to be understood that these examples are intended in an illustrative rather than in a limiting sense. It is contemplated that modifications and combinations will occur to those skilled in the art, which modifications and combinations will be within the spirit of the invention and the scope of the following claims. 
     Any and all patents, patent applications and printed publications referred to above are incorporated by reference.