Patent Document

RELATED APPLICATIONS 
     This application is a divisional of U.S. application Ser. No. 09/439,972, filed Nov. 12, 1999 issued as U.S. Pat. No. 6,144,675; which is a continuation of U.S. application Ser. No. 09/301,643, filed Apr. 28, 1999 and issued as U.S. Pat. No. 5,995,402; which is a continuation of U.S. application Ser. No. 09/023,254, filed Feb. 13, 1998, and issued as U.S. Pat. No. 5,936,877. 
    
    
     TECHNICAL FIELD 
     This invention relates generally to semiconductor devices. In particular, this invention relates to die architecture for semiconductor memory devices configured to execute high speed applications, such as those performed in synchronous dynamic random access memory devices. 
     BACKGROUND OF THE INVENTION 
     Assembling an integrated circuit package often involves attaching a die to a lead frame. As an additional part of assembly, bond wires are used to electrically connect the conductive leads of the lead frame to the die&#39;s bond pads. The die/lead frame assembly is then encased in a housing with the outer ends of the conductive leads remaining exposed in order to allow electrical communication with external circuitry. The die&#39;s architecture may represent one of many circuitry configurations, such as a Dynamic Random Access Memory (DRAM) circuit or, more specifically, a synchronous DRAM (SDRAM) circuit. 
     The high speed synchronous operations associated with SDRAM circuitry often involve communication with an external device such as a data bus. Occasionally, the data bus may be relatively wide in comparison to the standard width of prior art SDRAM dies. The width of the data bus, in turn, requires an appropriate number of conductive leads positioned to accommodate the bus. Further, the position of the conductive leads and their spacing limitations require a certain amount of die space for bond pad connection. However, the prior art does not provide a die having one particular region that can provide enough bond pads to accommodate all of the conductive leads. Rather, the architecture of the die as found in prior art allows for bond pads to be located in different areas of the die. Consequently, conductive leads of different lengths are needed to connect the bond pads to the relatively wide data bus. These differing lengths slow the operations of the SDRAM, or any semiconductor device for that matter, as it takes longer for signals to travel through the longer conductive leads. Thus, if synchronized signals are desired, the speed of the device is limited by the speed of signal propagation through the longest conductive lead. The longer leads also have a greater inductance associated with them, thereby further slowing signal propagation. Moreover, the inductance in the longer conductive leads is different from the inductance associated with the relatively short conductive leads. This imbalance in induction makes synchronizing the signals even more difficult. 
     Thus, it would benefit the art to have a die configuration that provides bond pads in a common location such that all of the conductive leads of the lead frame could be the same length. It would further benefit the art if the die configuration allowed uniformly short conductive leads. Indeed, this desire is mentioned in U.S. Pat. No. 5,408,129, by Farmwald, et al., which discloses a high-speed bus as well as memory devices that are adapted to use the bus. Specifically, Farmwald &#39;129 discloses a narrow multiplexed bus, as demonstrated by Farmwald&#39;s preferred embodiment, wherein the bus comprises only nine bus lines. Accordingly, Farmwald&#39;s narrow bus allows for a relatively low number of bond pads on the die of a memory device. Farmwald &#39;129 concludes that it would be preferable to place the small number of bond pads on one edge of each die, as that would allow for short conductive leads. Farmwald &#39;129 at col. 18, ln. 37-43. However, it is possible to do so under Farmwald &#39;129 only because the “pin count . . . can be kept quite small” due to the narrow architecture of the bus. Id. at ln. 17-18. 
     Contrary to the teachings in Farmwald &#39;129, it would be advantageous at times to accommodate a relatively wide bus requiring a large number of pins. It would therefore be additionally advantageous to provide a die capable of providing the correspondingly large number of bond pads on one side of the die. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention provides die architectures allowing for the relocation of the die&#39;s bond pads. One embodiment of this invention arranges for all of the die&#39;s bond pads to be located on one side of the die, with the corresponding memory banks arranged accordingly. In a preferred embodiment, the length of the die side having the bond pads is extended relative to prior architectures and the memory arrays are shaped to follow along the extended side. Consequently, the perpendicular sides contiguous to the extended side may be shortened. This architecture has the advantage of allowing the die to cooperate with a lead frame having conductive leads of the same length, thereby balancing inductance and aiding in the ability to synchronize signals. This architecture also has the advantage of allowing the conductive leads to be relatively short, which further increases the operational speed of the die&#39;s circuitry and decreases inductance. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 depicts the architecture of a SDRAM chip as found in the prior art. 
     FIG. 2 illustrates an SDRAM chip within a lead frame as found in the prior art. 
     FIGS. 3 a  and  3   b  portray a first exemplary embodiment of the present invention. 
     FIG. 4 represents an embodiment of the present invention in cooperation with a lead frame. 
     FIGS. 5 a  and  5   b  demonstrate a second exemplary embodiment of the present invention. 
     FIGS. 5 c  and  5   d  illustrate a third exemplary embodiment of the present invention. 
     FIGS. 6 a  and  6   b  depict a fourth exemplary embodiment of the present invention. 
     FIGS. 6 c  and  6   d  depict a fifth exemplary embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 depicts the architecture of an SDRAM  20  as it exists in the prior art. The SDRAM  20  is fabricated on a die  22  and includes sixteen memory banks B 0  through B 15 . The shape of each bank is determined by the number and arrangement of component sub-arrays. In this prior art example, each bank comprises a row of sixteen sub-arrays. Bank B 0 , for example, comprises sub-arrays  000  through  015 . Similarly, bank B 1  comprises sub-arrays  100  through  115 . For purposes of explaining the current invention, it is understood that each bank is analogously numbered, ending with sub-arrays  1500  through  1515  comprising memory bank B 15 . Each sub-array contains a number of memory bit components and accompanying n/p channel sense amplifier circuitry  26  as well as row decoder circuitry  28 . The banks B 0 -B 15  are also serviced by a first 64×DC sense amp  30  and a second 64×DC sense amp  32 . It should be noted that the size and number of DC sense amps can vary based on the compression rate desired. Column decoder circuitry  34  is located next to the DC sense amps  30  and  32 ; and a column select line  36  extends from the column decoder circuitry  34  through all of the memory banks B 0 -B 15 . Logic circuitry is located in a region  38  on the other side of the DC sense amps  30  and  32  relative to the memory banks B 0 -B 15 . Bond pads  40  are placed on the perimeter of the die  22  to allow easy access. For purposes of this application, the term “bond pad” includes any conductive surface configured to permit temporary or permanent electrical communication with a circuit or node. Further, it should be noted that there exists a series of bond pads—defined here as access pads, wherein each access pad of the series is coupled to one sub-array of each bank, thereby allowing electrical signals to access those sub-arrays. For example, access pad  40 A is defined to be coupled to sub-arrays  000 ,  100 ,  200 ,  300 ,  400 , through  1500 . Access pad  40 G is coupled to sub-arrays  006  through  1506 . Access pad  40 P, in turn, is defined to be coupled to sub-arrays  015  through  1515 . Accordingly, there are thirteen other access pads, each associated with a corresponding column comprising one sub-array from every bank. In order to keep connective circuitry to a minimum, these sixteen access pads are located near their respective sub-arrays. It should be noted that, in FIG. 1, the group of sub-arrays  000  through  1500  is highlighted in bold for purposes of indicating the common association those sub-arrays have with a particular access pad (such as  40 A, for these sub-arrays). Groups  006 - 1506  and  015 - 1515  are similarly highlighted. Other bond pads  40 , representing additional input and output terminals for communicating with the die  22 , are placed in the remaining available spaces on the die  22 , which may include more than one side of the die  22 . 
     Packaging of the die  22  may be influenced by the fact that the internal circuitry of the die  22  will be interacting with a data bus. Specifically, as seen in FIG. 2, the die  22  can be placed within a lead frame wherein the conductive leads  48 ,  50  extend from the die  22  and eventually orient in one direction in anticipation of connecting to the data bus. In FIG. 2, bond pads  40  that are on the die&#39;s near side  42 —the side that will be closest to the external device—require only relatively short conductive leads  48 . However, bond pads  40  along the sides  44 ,  46  contiguous to the near side  42  require longer conductive leads  50 . Assuming that the signal propagation rate through the conductive leads  48 ,  50  is generally the same, the longer conductive leads  50  will take a longer time to transmit any signals. Moreover, inductance of the longer conductive leads  50  will be greater than inductance of the shorter conductive leads  48 . 
     FIGS. 3 a  and  3   b  illustrate one embodiment of the current invention that solves these problems. In this embodiment, the memory banks are separated into discontiguous portions. Despite placing portions of the banks in separate locations, the columnar arrangement of sub-arrays, one from each bank, is retained, and the columns are rotated ninety degrees relative to the configuration addressed above. Thus, rather than being parallel to the contiguous sides  44  and  46 , the columns are now parallel to the near side  42 . For example, the sixteen sub-arrays associated with access pad  40 A ( 000  through  1500 ) extended along contiguous side  44  in the prior art die depicted in FIG.  1 . Again, this group of sub-arrays commonly coupled to access pad  40 A is highlighted to show the new orientation of the sub-arrays and of the group in general. In FIG. 3 a , this group of sub-arrays now extends along the near side  42 . While this group of sub-arrays  000  through  1500  is still relatively near contiguous side  44 , this is not necessary for purposes of the current invention; this group could occupy any of the columnar positions depicted in FIG.  2 . Regardless of the particular position of the columns, it is preferred that their respective access pad remain relatively close by. Moreover, given this new configuration, each sub-array is now oriented perpendicular to the near side  42  of the die  22 . 
     Further, it should be noted that, while the arrangements of sub-arrays in FIG. 2 might be described as “rows” given the ninety degree rotation, the arrangements are referred to as “columns” or “columnar positions” for purposes of demonstrating the continuity with portions of the die architecture in FIG.  1 . 
     As an example of this continuity, the row decoder circuitry  28  and column decoder circuitry are also rotated ninety degrees and, therefore, retain their orientation relative to each sub-array. Column decoder devices in this embodiment include a first modified column decoder circuit  60  interposed between a  700  series of sub-arrays ( 700  to  703 ) and an  800  series of sub-arrays ( 800 - 803 ). In addition, a first modified column select line  62  extends from the first modified column decoder circuit  60  through sub-arrays  700  to  000 . Similarly, a second modified column select line  64  extends from the first modified column decoder circuit  60  through sub-arrays  800  to  1500 . This embodiment also includes three other similarly configured modified column decoder circuits  66 ,  61 , and  67 , each with their own modified column select lines  68  and  70 ,  63  and  65 , and  69  and  71 , respectively. 
     Moreover, instead of two 64×DC sense amps  30  and  32 , this embodiment of the present invention uses four 32×DC sense amps  52 ,  54 ,  56 , and  58 . However, as in the prior art, the size and number of DC sense amps merely affect data compression and no one DC sense amp configuration is required for any embodiment of the current invention. 
     In this exemplary embodiment, the columns are further arranged in groups of four. In doing so, this embodiment partially retains some of the bank continuity found in the prior art. For example, the sub-array sequence  000 ,  001 ,  002 , and  003  of Bank  0  remain contiguous. The Bank  0  sequence continues in the next four rotated columns with sub-arrays  004 ,  005 ,  006 , and  007  remaining next to each other. These intervals of bank continuity apply to the other memory banks as well and aid in minimizing the complexity of row decoder and column decoder circuitry. Arranging the columns in groups of four also means that certain columns will be further away from the near side  42  than other columns. As a result, there may be unassociated sub-arrays between a column and its access pad. For example, connective circuitry (not shown) coupling column  003 - 1503  to access pad  40 D will probably pass by sub-arrays within columns  002 - 1502 ,  001 - 1501 , and  000 - 1500 . 
     Additionally, this arrangement of rotated columns allows for altering the dimensions of the die  22 . Not only can the near side  42  be extended to a length commensurate with the data bus, but the contiguous sides  44  and  46  may also be shortened. Moreover, extending the near side  42  provides chip space for the bond pads  40  that had been along the contiguous sides  44 ,  46  in the prior architecture. FIG. 4 demonstrates the result of this architecture: when the die  22  is attached to a lead frame  76  having conductive leads on only one side, the die&#39;s formation accommodates short conductive leads  78  of uniform length. Packaging the die  22  with this lead frame  76 , in turn, allows for fast operation of the die  22  in conjunction with a device having a relatively large number of data terminals, such as a wide data bus. 
     Other embodiments of the present invention can lead to the same packaging advantages. The exemplary embodiment in FIGS. 5 a  and  5   b , for instance, demonstrates that, although the sub-arrays are rotated ninety degrees as in FIGS. 3 a  and  3   b , it is not necessary to retain the columnar arrangement of the previous embodiment. Instead of the 16×1 columns, the sub-arrays in FIGS. 5 a  and  5   b  have been grouped into 4×4 associations. As demonstrated in the previous embodiment, there is a repetition of the sub-array pattern at continuous intervals. In the embodiment shown in FIGS. 5 a  and  5   b , sequential sub-arrays of a particular bank are separated by sub-arrays of other banks. Sub-arrays  000  and  001  of Bank  0 , for example, are separated by sub-arrays  400 ,  800 , and  1200 . As further demonstrated in the previous embodiment, it is still preferred to configure the access pads near their respective grouping. Nevertheless, because the associated sub-arrays in FIGS. 3 a  and  3   b  extend along one dimension and include one sub-array from every bank, there is more sharing of row decoder circuitry  28  as well as column select circuitry  62 ,  64 ,  68 ,  70 ,  63 ,  65 ,  69 , and  71  in that embodiment than in the more fragmented sub-array groupings depicted in FIGS. 5 a  and  5   b . Accordingly, the embodiment in FIGS. 3 a  and  3   b  is the more preferred embodiment of the two. FIGS. 5 c  and  5   d  represent an alternate configuration of 4×4 associations. 
     There are also alternative embodiments that do not involve rotating the orientation of the sub-arrays, as demonstrated in FIGS. 6 a  and  6   b . Whereas there are sixteen rows of sub-arrays extending back from the near side  42  of the die  22  in FIG. 1, the die  22  in FIGS. 6 a  and  6   b  has a memory configuration only eight sub-arrays “deep.” Further, the sub-arrays are gathered into 8×2 groupings, again with one sub-array from every bank in each group and with each group associated with a particular access pad. Moreover, each group is oriented perpendicular to the near side  42  of die  22 . Group  90  has been defined to contain sub-arrays  000  through  1500 , group  92  contains sub-arrays  001  through  1501 , and group  94  contains sub-arrays  002  through  1502 . While no particular order of groups is required, it is noteworthy in this embodiment that the sub-arrays  800  through  1500  in group  90  are next to sub-arrays  801  through  1501  in group  92 . In effect, groups  90  and  92  could be considered “mirror images” of each other. This mirror image configuration is useful in compressing data for test modes and in maximizing the opportunity to share row decoder circuitry  28 . It can further be seen in FIGS. 6 a  and  6   b  that group  94  is a mirror image of group  92 , wherein sub-arrays  002  through  702  are respectively contiguous to sub-arrays  001  through  701 . While these mirror image configurations are preferable in a die architecture having 8×2 sub-array groupings, they are not necessary to realize the current invention. As in other embodiments, this one has a die shape capable of including bond pads in a configuration accommodatable to communication with an external device, with a memory arrangement generally conforming to the die shape. 
     The embodiment in FIGS. 6 a  and  6   b  also benefits from four 32×DC sense amps  80 ,  81 ,  82 , and  83 . Further, there are two column decoder circuits  84  and  85 , each associated with respective column select lines  86  and  87 . Unlike the previous embodiments, however, each sub-array is oriented parallel to the near side  42  of the die  22 . FIGS. 6 c  and  6   d  represent an alternate configuration of 8×2 associations or groupings of sub-arrays. 
     One of ordinary skill can appreciate that, although specific embodiments of this invention have been described for purposes of illustration, various modifications can be made without departing from the spirit and scope of the invention. For example, embodiments of die architecture covered by this invention need not be restricted to placing bond pads on only one side of a die. It may be desirable in certain applications to use a lead frame having conductive leads facing two or more sides of a die. Die architectures included within the scope of this invention could locate the die&#39;s bond pads to allow for conductive leads of a uniform length and, more specifically, a uniformly short length on all relevant sides. In addition, the dimensions of the memory banks could be adapted to conform to a particular die&#39;s requirements. If, for example, the number of bond pads and the conductive lead pitch limitations require a die side even longer than the near side  42  in FIGS. 5 a  and  5   b  , the 4×4 banks of rotated sub-arrays can be replaced with an embodiment having a series of rotated sub-arrays grouped into 2×8 banks. Accordingly, the invention is not limited except as stated in the claims.

Technology Category: 3