Abstract:
One embodiment of the present invention provides for a master or universal base and base tooling which addresses the general purpose Structured ASIC requirements. Another embodiment of the present invention provides for a common set of base tooling from which the master/universal base is created as well as additional custom bases with customized selection and quantity of embedded Platform ASIC functions. Embodiments can utilize conventional Structured ASIC architecture and processing and are compatible with traditional probing and packaging.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. The Field of the Invention  
         [0002]     The present invention relates to the field of Application Specific Integrated Circuit (ASIC) design and tooling. In particular, the present invention relates to systems and methods for reducing the number of base wafer designs and reducing tooling costs associated with design and fabrication of structured and platform ASIC devices.  
         [0003]     2. Background and Related Art  
         [0004]     Various approaches are used to build custom logic Integrated Circuit (“IC”) devices. Different components, such as, for example, prefabricated Programmable Logic Devices (“PLDs”) (sometimes referred to as Field Programmable Gate Arrays (“FPGAs”)), gate arrays, standard cells (sometimes referred to as cell-based ICs), and hand-crafted custom logic, can be used to implement a custom logic IC device. Each of the different components is associated with a number of design parameters, such as, for example, development cost, unit cost, design cycle time, manufacturing cycle time, flexibility, risk, complexity, performance, and power consumption. Accordingly, selection of a particular component for use in a custom logic IC can be made based on the design parameters of the component.  
         [0005]     FPGA devices are essentially high-volume standard products and are cost effective for low-volume or low-complexity devices. On the other hand, cell-based and hand-crafted custom ICs may be more appropriate for high-volume high-complexity devices. In between, gate-array devices have typically been used to implement medium-complexity, medium-volume devices.  
         [0006]     However, gate arrays often lack the flexibility to support more complex functionality such as, for example, large amounts of memory, timing generator functions and other specialized functions (e.g., processors and I/O physical interfaces). Thus, cell-based and hand-crafted custom ICs are used to implement this more complex functionality. Unfortunately, with advances in process technology, the resulting development cost of cell-based and hand-crafted custom IC&#39;s is rising exponentially, due at least in part to the cost of photolithographic reticle tooling. This increased development cost essentially limits the use of cell-based and hand-crafted custom IC&#39;s to very high-volume cost-sensitive applications. That is, it may be difficult to implement high-complexity low-volume applications in a cost efficient manner.  
         [0007]     More recently, a new class of devices, often referred to as Structured ASICs, has emerged to fill the gap between the FPGA and cell-based approaches. Structured ASICs utilize pre-fabricated base wafers which include resources for logic, memory, timing generators and may include other specialized functional blocks, commonly referred to as Intellectual Property (IP). The base wafers are then personalized with a reduced number of customized metal and/or via interconnection levels to produce the desired custom logic device. Structured ASICs share similarity with gate arrays in that both use a base wafer approach. Like gate arrays, each Structured ASIC family requires a set of bases (e.g., from 6 to 12), covering a range of silicon die sizes to address the needs of different size devices and corresponding packages.  
         [0008]     However, structured ASICs differ from gate arrays by including more embedded functions and by pre-designing or fixing more interconnection layers. By minimizing the number of customized interconnection levels required, the tooling development costs can be reduced significantly. Other recent tooling mechanisms use more advanced process technology (i.e., more expensive tooling) for base wafers and less advanced process technology (i.e., less expensive tooling) for the customized levels. These more recent mechanisms distribute the development cost of the base wafer across multiple custom logic devices to reduce overall development cost. Along with relatively lower development cost for a small number of less expensive customized interconnect level tooling, the total tooling cost for a device may be substantially reduced.  
         [0009]     One challenge in selecting the architecture of structured ASIC devices is deciding what type of and in what quantity pre-designed functional blocks should be embedded in the base. If the appropriate IP functions are not included, the corresponding device will not be usable for certain applications. If too many embedded IP functions are unused in a particular application, significant silicon area will be unused, potentially making the cost of the device too high.  
         [0010]     One solution is to build a special type of structured ASIC called a platform ASIC that addresses the needs of a particular set of applications. For example, a communications platform ASIC might include I/O processing cores and I/O physical interfaces, whereas a signal processing platform ASIC might include Digital Signal Processing (DSP) processing components and A/D and D/A converters. However, developing multiple platforms each requiring a number of bases (e.g., 6 to 12) requires a significant financial investment.  
         [0011]     Further, there are other tooling costs in addition to the photolithographic reticles discussed above. These costs include reticles for flip-chip style pad ReDistribution Layers (“RDLs”), wafer probe cards, and customized IC package development. Each base in a Structured (or Platform) ASIC family will require these additional types of tooling, and thus, will incur some additional corresponding cost, which can usually be distributed across multiple custom logic devices.  
         [0012]     Prior art contains various approaches to reducing the number of base wafers required to implement a gate array family. One approach uses a borderless gate array to print a sea of transistors across the surface of the die. The actual die border is defined by scribe lines in the programmable levels. In this manner a one-size-fits-all base is created from which different size die can be created.  
         [0013]     However, the borderless approach faces several problems. One problem is finding an effective way to achieve isolation from the scribe line region. Scribe lines defined in the programmable levels may provide good definition of the cutting region but since scribe lines typically do not extend into base layers, good isolation is difficult to achieve.  
         [0014]     A second problem arises due to the intrinsic differences between transistors designed for use in core logic functions and those intended for use in I/O functions. Typically the I/O transistors are much larger, operate with different voltages and require special ESD protection structures. With the borderless approach it is desirable to be able to use any part of the base for core logic functions and any part for I/O functions. Various approaches have been used to achieve dual-use transistors, but the disparity in core and I/O transistor requirements continues to widen, making it evermore difficult to create efficient dual-use structures.  
         [0015]     Most borderless approaches do not handle alignment marks and other photolithograhic and processing artifacts very efficiently, often resulting in significant wasted silicon real estate. Accordingly, it may be difficult to align repeating patterns on the base with repeating patterns on programmable levels. Many existing mechanisms avoid this alignment issue by intentionally wasting space. As such they are typically directed to prototyping and are typically not useful for volume production.  
         [0016]     Prior art also includes the concept of a base wafer with borders in one-dimension. These borders effectively create strips of core cell logic functions and I/O functions. The strip dimensions are fixed in one direction, but as wide as the wafer in the other direction, permitting a range of rectangular sized die to be created by defining scribe lines in the programmable levels.  
         [0017]     To some extent, the one-dimensional bordered arrays solve the problem of sharing core logic and I/O functions. However, one-dimensional bordered arrays require that I/O functions are restricted to running along the two side borders. Thus, problems with isolation in the scribe line regions in the unbordered direction and problems with repeating patterns of alignment and other manufacturing artifacts still exist.  
         [0018]     Additionally, prior art includes base wafers with borders in two-dimensions. The resulting rectangular regions may be clustered or stitched together to form a larger die. However, these two-dimensional bordered arrays have been limited to the traditional sea-of-transistor architecture. They use traditional I/O ring architectures and route I/O from the interior portions of the I/O rings to wire-bond pads around the periphery of the final die. Some two-dimensional bordered arrays include circuitry in the scribe line regions specifically for bridging signals from one region to another.  
         [0019]     The two-dimensional bordered arrays solve some of the scribe line, core logic and I/O function problems. However, problems related to isolating circuitry in the scribe line regions and dealing with the multitude of alignment, manufacturing and testing artifacts placed on a wafer surrounding the individual die still exist. These problems are particularly acute when the base die reticle fields have a different repeat sequence than the programmable level reticle fields. Accordingly, what would be advantageous are systems and methods for reducing the number of bases and reducing base tooling expenses associated with structured and platform ASICs while optimizing die size for individual applications.  
       BRIEF SUMMARY OF THE INVENTION  
       [0020]     The principles of the present invention are directed towards reducing the number of base wafer designs and reducing tooling costs associated with design and fabrication of Application Specific Integrated Circuit (ASIC) devices. One embodiment provides for a master or universal base and base tooling which addresses the general purpose Structured ASIC requirements. Another embodiment provides for a common set of base tooling from which the master/universal base is created as well as additional custom bases with customized selection and quantity of embedded Platform ASIC functions. Embodiments can utilize conventional Structured ASIC architecture and processing and are compatible with traditional wafer probing and packaging methods and technologies.  
         [0021]     Additional features and advantages of the invention will be set forth in the description that follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The features and advantages of the invention may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]     In order to describe the manner in which the above-recited and other advantages and features of the invention can be obtained, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:  
         [0023]      FIG. 1A  illustrates a universal integrated circuit base wafer with individual base die.  
         [0024]      FIG. 1B  illustrates the universal integrated circuit base wafer of  FIG. 1A  with individual base die grouped into corresponding customized die clusters.  
         [0025]      FIG. 1C  illustrates a more detailed view of an example die cluster region  
         [0026]      FIG. 1D  illustrates a more detailed view of an individual base die region.  
         [0027]      FIG. 1E  illustrates a more detailed view of a scribe line region between four individual base dies.  
         [0028]      FIG. 1F  illustrates customized die clusters formed from grouping corresponding pluralities of individual base die together.  
         [0029]      FIG. 1G  illustrates the section view of the customized die clusters of  FIG. 1F .  
         [0030]      FIG. 2A  illustrates a reticle field filled with a repeating pattern of base die.  
         [0031]      FIG. 2B  illustrates a reticle field filled with the outline of a die cluster pattern.  
         [0032]      FIG. 3  illustrates an example flowchart of a method for designing and fabricating universal base wafers.  
         [0033]      FIG. 4A  illustrates a customized base wafer with different types of individual base die.  
         [0034]      FIG. 4B  illustrates the customized base wafer of  FIG. 4A  with different types of individual base die grouped into corresponding customized die clusters.  
         [0035]      FIG. 4C  illustrates a customized die cluster region formed from grouping different types of individual base die.  
         [0036]      FIG. 4D  illustrates an individual base die region.  
         [0037]      FIG. 5A  illustrates a reticle field containing multiple different die patterns and blade space.  
         [0038]      FIG. 5B  illustrates a reticle field containing multiple different die patterns, special scribe-line patterns and blade space.  
         [0039]      FIG. 6  illustrates an example flowchart of a method for designing and fabricating universal multi-pattern base reticles.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0040]     The principles of the present invention are directed towards reducing the number of base wafer designs and reducing base tooling expenses associated with structured and platform ASICs while optimizing die size for individual applications.  
         [0041]     Generally, silicon wafers used in the fabrication of integrated circuits can be partially fabricated up through a desired processing level (e.g., to implement partial IC functionality). The wafer at this stage is commonly referred to as a “base wafer”. To accomplish this, one or more levels are created through a conventional photolithographic process involving a series of printing and processing steps. For each level, a pattern is printed on a reticle with appropriate alignment marks for aligning of the reticle to the previous levels on the base wafer. The pattern of the reticle is applied to the surface of the base wafer to print a pattern on a portion of the wafer. Then, the reticle is stepped to other locations on the wafer using the alignment marks to print the pattern on a different wafer location. The use of alignment marks facilitates alignment between different levels and across different regions of the base wafer. Printing, movement, and alignment can continue until an appropriate repeating pattern results. Base wafers can be stored for further processing at a later time.  
         [0042]      FIG. 1A  illustrates an integrated circuit (“IC”) base wafer  100  with individual base die. Base wafer  100  can be fabricated using a set of reticles, each having a pattern and appropriate alignment marks. As depicted in  FIG. 1A , base wafer  100  includes a plurality of repeating individual die (represented by the space within the lines). Base level scribe lines surround each of the individual die in base wafer  100  (indicating where individual die to are to be cut).  
         [0043]     Subsequently, the stored base wafers can be retrieved and further processed (e.g., to implement customized IC functionality). Unlike conventional IC fabrication, this invention allows processing which can include utilizing a grouping pattern on a customized reticle to group individual die into die clusters.  
         [0044]      FIG. 1B  illustrates the IC base wafer  100  with individual base die grouped into corresponding customized die clusters (represented by the space within thicker lines). Customized die clusters can be printed on top of individual die using a conventional IC photolithographic processing approach with customized reticles. Each of the customized die clusters can include one or more individual die.  FIG. 1B  depicts groupings of four-by-four individual die (16 individual die total) within each customized die cluster. However, the customization process can be utilized to create a wide variety of different individual die grouping configurations (e.g., 1×6, 2×3, etc.). It may be even that a customized die cluster includes a single individual die.  
         [0045]      FIG. 1C  illustrates a more detailed view of an example die cluster region  103 . Although the die cluster region  103  centers on a particular die cluster, portions of surrounding die clusters are also shown for context. Similarly, although the individual base die region  102  centers on an individual base die, surrounding individual base dies are also shown within the region for context. The size of an individual die cluster can vary across a range of appropriate sizes. However, in  FIG. 1B  the distances  180  and  181  can be some number of millimeters, such as, for example, in a range from 4 to 10 mm. Scribe line intersection region  104  includes an intersection of scribe lines included in base wafer  100 .  
         [0046]     The regular and repeating structure of base wafer  100  is thus customized by printing an appropriate interconnection pattern for each customized die cluster on the final layers. The resulting interconnection pattern of die cluster  103  interconnects various components of base wafer  100  to one another. Interconnections between individual base die as well as within individual base die can be facilitated with upper level interconnects. Scribe lines on the customized levels surround each of the custom die clusters (indicating where custom die clusters are to be cut) and thereby define the final die size.  
         [0047]     Since customized die cluster patterns  103  are printed on top of individual die patterns (e.g., of base wafer  100 ), not all scribe lines between individual die will be completed during the fabrication process. That is, based on the customized die cluster configuration, only some of the base level scribe lines will be co-incident with custom level scribe lines. Co-incident base level scribe lines are extended up into the customized levels resulting in a completed scribe line. A customized die cluster can be cut from the wafer using this completed scribe line.  
         [0048]     However, other base level scribe lines (e.g., base level scribe lines not on a boundary between customized die clusters) will be internal to a customized die cluster. That is, the customized die cluster interconnections between the individual die essentially cover over these internal base level scribe lines. Accordingly, these internal base level scribe lines are left incomplete and are not used during the wafer fabrication process. Since these covered internal base level scribe lines remain intact during fabrication, functional resources embedded in the covered internal base level scribe lines can also be interconnected to and used by the rest of circuitry forming a customized die cluster.  
         [0049]      FIG. 1D  illustrates a more detailed view of an individual base die region  102 . As depicted, an individual base die (as bounded by scribe line regions  109 ) can include, but is not limited to, logic gates  105 , memory  106 , I/O resource  107 , and flip-chip solder bump sites or bond pads  108 . Scribe line regions  109  surround these other components of the individual base die. Scribe line regions  109  are essentially isolation regions designed to surround the active silicon device area and protect the device from the destructive effects of scribing and cutting of a wafer into individual die.  
         [0050]     In some embodiments, I/O resources are distributed around the periphery of an individual base die and can include bond pads for bond wire connections to the package. In other embodiments, a flip-chip redistribution layer (“RDL”) is utilized to spread out I/O cell connections to flip-chip solder bumps. Thus, in these other embodiments, I/O cells may be grouped together in large rectangular regions, allowing electro-static discharge (“ESD”) energy to dissipate and allowing creation of I/O cells with efficient aspect ratios.  
         [0051]     The size of an individual base die cluster can vary across a range of appropriate sizes. However, in  FIG. 1D , distances  182  and  183  can be some number of millimeters and are smaller than or equal to distance  180 . For example, referring back to  FIG. 1C , a four-by-four array of individual die are included in each customized die cluster.  
         [0052]      FIG. 1E  illustrates a more detailed view of a scribe line intersection region  104 . Scribe line intersection region  104  depicts scribe line regions  109  that separate four individual base dies. Some of the components of the individual base dies, such as, for example, I/O module  107  and flip-chip solder bump sites or bond pads  108  of the upper left individual base die, are also depicted. Furthermore, there are also other components even within the scribe line regions  109 . Such other components include, for example, guard rings  110 , alignment marks  111 , process monitor devices  112 , scribe-line monitor devices  113 , and embedded circuit or function region  114 . Alignment marks  111 , process monitor devices  112 , and scribe-line monitor devices  113  can be used during the wafer fabrication process. Process monitor devices  112  and scribe-line monitor devices  113  can be probed and examined before they are destroyed during the scribing process. During printing, alignment marks  111  can be utilized to align a reticle for a die cluster with alignment marks on previous layers, such as, for example, associated with the individual die of base wafer  100 .  
         [0053]     Guard rings  110  isolate active silicon regions (i.e., the portions that would remain after scribing) from inactive silicon regions (i.e., the portions separated by scribing). Scribing may then occur along finished (or completed) scribe lines as defined by the clusters. This provides significant flexibility in the configuration of the resulting die. Furthermore, the scribe lines that are not cut during die separation (e.g., covered internal base level scribe lines) may themselves contain useful circuitry. For example, if a vertical scribe line is cut and an intersecting horizontal scribe line remains uncut, circuitry in the horizontal scribe line area remains protected and useable.  
         [0054]     The guard ring locations can be pre-designated in a repeating interconnect pattern along all scribe lines that are potentially subject to scribing. Guard rings can extend into the scribe line area such that corresponding portions of circuitry (in a partially completed scribe line) are protected and can remain intact after a cut along a perpendicular adjacent (or intersecting) finished (or completed) scribe line.  
         [0055]      FIG. 1F  illustrates customized die clusters formed from grouping corresponding pluralities of individual base die together. More specifically, portion  115  represents a portion of the surface of a customized IC wafer. Portion  115  depicts two customized die clusters  122  each including four individual die (in a two-by-two configuration). Finished scribe lines  116  (represented by the solid lines following the mid-line of the scribe lines) at the boundaries of each customized die cluster  122  indicate locations where portion  115  is to be cut. Alignment marks  111 , process monitor devices  112 , and scribe-line monitor devices  113  are also depicted.  
         [0056]     Scribe line regions internal to a cluster (e.g., scribe line regions  109 ) represent unused silicon area. Through appropriate isolation, each scribe line region can include a region where resources can be embedded. For example, embedded region  114  depicts a region where resources can be embedded in scribe line region  109 . Any number of different resources can be embedded in embedded region  114 , such as, for example, logic fabric (e.g., sea of gates or sea of macros), I/O blocks (e.g., I/O cells, bond pads, flip-chip solder bumps, or ESD protection), memory, timing generators (e.g., delay locked loops or phase locked loops), I/O physical interfaces (e.g., dual-data-rate PHYs, or high-speed serial/de-serializers), and processors. Thus, at least some of the space consumed by scribe line regions can be reclaimed and used to implement the desired functionality of an IC device.  
         [0057]      FIG. 1G  illustrates a section view of the customized die clusters of  FIG. 1F . Interconnects on the upper customizable levels  117  personalizes the design by connecting with the predefined interconnect  118  and active devices  119  in base wafer portion  115 . Interconnect on the upper customized levels  117  can span the partially formed base isolation regions  120  (covered base level scribe lines) as necessary to complete connections in and between the regions. The customized  117  can thereby be used to define the size of the final die cluster depending on how many individual die are used and in what configuration.  
         [0058]     The customized levels also place scribe lines  116  around each of the (two-by-two) customized die clusters  122 . These scribe lines complete those base level scribe lines (e.g., in region  123 ) which correspond to the size of the final customized die cluster. Any number of predefined interconnect levels  118  and customizable levels  117  may be used. The customizable interconnect levels  117  may include any mix of predefined and customizable metal and via levels in any configuration.  
         [0059]     Embodiments of the present invention can facilitate creation of a universal base wafer. Any number of reticle tooling levels can be utilized to create a universal base wafer. Reticle tooling can be used as part of a photolithographic process to imprint a reticle field on a wafer. The photolithographic process can be optimized by placing multiple die images in the reticle field, which are then stepped and repeated or scanned across the wafer, exposing a photoresist. Other examples of photolithographic processes that can be used to create a base wafer include: full field, stepper, scanner, laser, and e-beam. When complete, the surface of the wafer contains a uniform array of individual base die.  
         [0060]      FIG. 2A  illustrates an example reticle field  224  that includes reticle tooling  223  for one level of a universal base wafer. Reticle tooling  223  is configured in a six-by-six configuration  225  of individual die images (e.g., each representing an area bounded by thin lines in  FIGS. 1A and 1B ). Reticle field  224  can be can be repeatedly moved and printed on a wafer as previously described. For example, multiple imprints of reticle tooling  223  can be used to create the pattern of base wafer  100 . Scribe line regions of a reticle field can be designed separately from the base die themselves and create a pattern which repeats every field dimension, as opposed to every die dimension (freeing up space to place circuitry and functions in scribe line regions that are to be covered over). The scribe line regions are designed such that any special embedded resources  114  are repeated on the die dimension.  
         [0061]     A wide variety of reticle tooling configurations can be used to create the pattern of base wafer  100 . For example, it may be that reticle tooling configured as a six-by-six or even three-by-five configuration of individual die images is used to create the pattern of base wafer  100 . Increasing the number of individual die images in reticle tooling  223  reduces the number of times reticle field  224  must be imprinted to create the pattern of base wafer  100 . Thus, it may that reticle field  224  is filled with as many die images  225  as possible to correspondingly reduce the number of wafer printing steps to as few as possible  
         [0062]      FIG. 2B  illustrates a reticle field  227  that includes reticle tooling  226  representing the outline of a die cluster pattern. Reticle tooling  226  defines a custom die cluster configuration that is to group four-by-four individual die when printed on a base wafer. For example, reticle tooling  226  can be printed on base wafer  100  to create the areas bounded by the thicker lines in  FIG. 1B . The vertical dashed lines  228  and horizontal dashed lines  229  represent underlying individual die boundaries (e.g., scribe line regions that result from printing reticle tooling  223 ) that are to be covered over (and thus become internal to a custom die cluster) when reticle field  227  is printed on a wafer (e.g., as depicted in  FIG. 1G ).  
         [0063]     Reticle field  227  can include tooling for completing embedded artifacts in base level scribe line regions that are to be covered (i.e., internal base level scribe line regions). Since base reticle fields and customized cluster reticle fields may be of different configurations (in arrangement and/or number of individual die), scribe line artifacts can be organized in repeating patterns such that no interference is created between artifacts in these fields. For example, artifacts can be placed on a regular repeating grid based on pre-defined internal base level scribe line regions. For example, artifacts can be placed in internal base level scribe line regions corresponding to the locations of vertical dashed lines  228  and horizontal dashed lines  229  (i.e., the covered die boundaries). Artifacts can be placed in patterns which permit any repeat frequency of cluster configuration patterns (e.g., the pattern represented in reticle field  226 ) to overlay the base pattern (e.g., the pattern of base wafer  100 ).  
         [0064]     A number of different types of artifacts, such as, for example, artifacts required only in the base, artifacts required only in the customizable levels, and artifacts which are composed of features in the base and customizable levels, can be utilized.  
         [0065]     Scribe line artifacts which are only required in the base levels can be repeated with a frequency determined by the dimensions of the base reticle field pattern  223 . Where these artifacts become part of internal base level scribe lines (e.g. they are covered by customizable levels  228 ,  229 ) they can be covered with interconnect. They may optionally be made accessible by cut-outs in the customizable levels. These cut outs can be repeated at all possible beat frequencies of the base reticle field pattern  223  and the customizable field pattern  226 .  
         [0066]     Scribe line artifacts which are only required in the customizable levels need not have any special provision in the base levels.  
         [0067]     Artifacts which originate in the base level scribe line regions and require additional features in the customizable levels to form complete structures can be repeated at all possible beat frequencies of the base reticle field pattern  223  and the customizable field pattern  226 .  
         [0068]      FIG. 3  illustrates an example flowchart of a method  300  for designing and fabricating universal base wafers. The method  300  will be described with some reference to the elements in  FIGS. 1A-1G  and  2 A and  2 B. The method  300  includes an act of designing a base die (act  301 ). Act  301  can occur before any particular customized integrated circuit is planned. A designer can use an appropriate software application to configure various blocks of the base die from cell libraries. A base die can be designed according to conventional ASIC die architecture with I/O cells distributed around the periphery of the base die and with logic and other embedded functions in the core of the base die. Alternately, a base die can be designed according to a modular die architecture with I/O cells, logic and other embedded functions included in blocks and/or I/O cell clusters for ESD dissipation. A base die can be designed such that the used portions of scribe line regions (e.g., corresponding to base level scribe lines potentially covered during customization) can be filled with embedded resources, such as, for example, timing generators and logic fabric.  
         [0069]     The method  300  includes an act of creating a set of one or more base die reticles for the base die (act  302 ). Act  302  can include assembling a set of reticles for a corresponding base based on one or more of the field size, process monitor and scribe line monitor requirements, and any special embedded resources (e.g., to be embedded in embedded region  114 ). For example, base die reticle with reticle field  224  can be created. Scribe line artifacts (alignment marks, process monitor devices, and scribe line monitor devices) can be organized in a reticle field to avoid interference with customized reticle fields. Scribe lines can be back-filled with embedded functions, such as, for example, timing generators and logic fabric.  
         [0070]     The method  300  includes an act of fabricating base wafers (act  303 ) and an act of storing the base wafers (act  304 ). At any time, for example, determined by fabrication lead times, base wafers are fabricated and subsequently held in inventory (e.g., in a stockroom). Fabrication of a base wafer can include repeatedly printing a base reticle field (e.g., reticle field  224 ) on a wafer. This process can be repeated with each reticle in the base reticle set to build up the base wafer with the desired number of levels. A single type of base wafer (e.g. base wafer  100 ) can be fabricated and held in inventory. This single type of base wafer (a universal base) can then be used for any mix of customized die cluster configurations.  
         [0071]     The method  300  includes an act of designing a custom application (act  306 ) and an act of defining an appropriate die cluster configuration (act  307 ). A die cluster configuration can be defined to meet the resource requirements of the custom application. A die cluster configuration can be defined to include any number of individual die and can be any of a variety of different arrangements (including square, for example, six-by-six and rectangular, for example, four-by-three). Based on the dimensions of individual die (e.g., 1 mm, 2 mm, etc.), the dimensions of the corresponding die cluster can be determined (e.g., 8 mm, 10 mm, etc.) such that cluster boundaries fall on individual die boundaries. A designer can utilize an appropriate software application to configure a cluster from die libraries.  
         [0072]     In some embodiments, one of a set of standardized configurations is defined so as to simplify flip-chip RDL, wafer probing and packaging. In other embodiments, each die cluster configuration is fully customized (e.g., having a different arrangement and/or different number of individual die). In some embodiments, all clusters across a given base wafer are the same. However, in other embodiments, it is possible to mix different sized clusters on a given base wafer.  
         [0073]     The method  300  includes an act of laying out the custom application (act  308 ). For example, after the die cluster configuration is defined, the custom application can be laid out to the die cluster configuration. The method  300  includes an act of creating custom reticles for the custom application (act  309 ). For example, die cluster reticle with reticle field  227  can be created. Depending on the size of a reticle field and the size of different die clusters, the reticle field of a custom reticle can include one or more (potentially different) die clusters. The method  300  includes an act of accessing base wafers (act  311 ). For example, it may be that previously fabricated base wafers  100  are pulled from a stockroom.  
         [0074]     The method  300  includes an act of fabricating custom levels based on the custom reticle (act  312 ). For example, reticle field  227  can be repeatedly printed on base wafer  100  to create a customized base wafer. It may be that a base reticle field configuration is similar to a die cluster reticle field configuration. For example, a base reticle field may be a five-by-five configuration of individual die and a die cluster reticle field may be defined to cover a five-by-five configuration of individual die. However, it may also be that a base reticle field configuration differs from a die cluster reticle field configuration. For example, reticle field  224  is a six-by-six configuration of individual die, while reticle field  227  defines a die cluster to cover a four-by-four configuration of individual die. Accordingly, act  312  can include utilizing a photolithographic process capable of maintaining alignment between the base level and other customizable levels with similar or different repeat sequences.  
         [0075]     When appropriate, a reticle field with one or more (potentially different) die clusters can be utilized to customize a base wafer. For example, such a reticle field can be repeatedly printed on base wafer  100  to create multiple clusters.  
         [0076]     The method  300  includes an act of scribing a custom die cluster (act  313 ). Individual die clusters are tested with wafer probe test equipment, with good dies scribed and cut from the customized base wafer. For example, good die clusters can be cut from base wafer  100  by cutting along the thicker lines depicted in  FIG. 1B .  
         [0077]     Other examples of photolithographic processes that can be used to customize a wafer include: laser and e-beam techniques. Laser and e-beam techniques use a raster scan technique to print stripes many individual/cluster die per pass. When many stripes are printed, a full row of die, such as, for example, in  FIG. 1B , can be created.  
         [0078]      FIG. 4A  illustrates a customized base wafer  400  with different types of individual base die. As depicted, customized base wafer  400  includes different individual base die regions  401  and  402 . Customized base wafer  400  can be created from a universal base reticle set having multiple different individual die patterns. The multiple different individual die patterns can be selectively printed to a base to create customized base wafer  400 . Different die patterns can be of similar (or even the same) dimensions. Utilizing alternate die patterns with the same dimensions makes it possible to interchange the alternate die patterns (on the base), while having little, if any, impact on the ability to cluster and scribe arbitrary numbers of base die for larger customized die.  FIG. 4B  illustrates the customized base wafer of  FIG. 4A  with different types of individual base die grouped into corresponding customized die clusters.  
         [0079]     The different base die patterns can contain various pre-defined embedded function blocks, such as, for example, included in alternate individual base die region  401 .  FIG. 4C  illustrates a customized circuit die cluster region  403  formed from different types of individual base die, such as, for example, individual die included in individual base die regions  401  and  402 .  FIG. 4C  illustrates how the customized levels would then interconnect these customized circuit die cluster regions  403  as described previously. Interconnection of customized levels facilitates creation of platform ASIC type devices of different sizes and compositions from a single reticle set, potentially significantly reducing NRE cost. The size of an individual die cluster can vary across a range of appropriate sizes. However, in  FIG. 4C  the distances  480  and  481  can be some number of millimeters, such as, for example, 8 mm. Thus, in  FIG. 4D , it may be that distances  482  and  483 , for 0&lt;example, represent a 2 mm by 2 mm die size.  
         [0080]      FIG. 4D  illustrates an individual based die region  401 . Individual base die  401  is an example composition of an alternative die pattern (from individual base die region  402 ) which contains a high-speed SerDes I/O block  404  and logic gates  406 . Any number of different die patterns containing a variety of different embedded functions is possible. The number of different die patterns can be based on the standardized base die size and the number of alternative die patterns that fit in the reticle field. Alignment marks  411  can be used during the wafer fabrication process.  
         [0081]      FIG. 5A  illustrates a reticle field  540  containing multiple different die patterns and blade space. One of these die patterns can be used to print a first type of individual die, while another one of these patterns can be used to print a second type of individual die. For example, pattern  532  can correspond to individual die in individual base die regions  402  and pattern  537  can correspond to individual base die in individual base die regions  401 .  
         [0082]     Within reticle field  540 , four different base die patterns are depicted, including a standard die pattern  532 , a SerDes die pattern  537 , a die pattern  541  that contains larger memory blocks, and a die pattern  542  that contains dedicated high-speed I/O PHYs. Various mechanisms can be used to selectively expose just a portion of reticle field  540  on a base wafer. These mechanisms can include blading or masking out appropriate (and/or non-desirable) die. Blading or masking out can require extra space  543  between the different die patterns in reticle field  540 . Blading or masking techniques can include full field, stepper and scanner.  
         [0083]      FIG. 5B  illustrates a reticle field  544  containing multiple different die patterns, special scribe-line patterns, and blade space. Depicted in reticle field  544  is large scribe line frame  545  and masked regions  546 . The large scribe line frame  545  can be exposed first and then individual die  532 ,  537 ,  541 , and  542  can be exposed over the masked regions  546  in the desired pattern. Accordingly, a number of alternating die patterns can be used in a manner that has little, if any, adverse effect on requirements of process monitors, scribe line monitors, and embedded functions (e.g., embedded in embedded region  114 ).  
         [0084]      FIG. 6  illustrates an example flowchart of a method  600  for designing and fabricating universal multi-pattern base reticles. The method  600  will be described with some reference to the elements in  FIGS. 4A-4D ,  5 A, and  5 B. The method  600  includes an act of designing a multiple base die (act  601 ). For example, before any particular customized integrated circuit is planned, a universal base reticle (e.g., based on reticle field  540  or  544 ) can be designed. Design of a multiple base die can include using a software program to configure various blocks of each base die from cell libraries.  
         [0085]     The method  600  includes an act of creating a set of multi-patterned base reticles (act  602 ). For example, a photolithographic process can include printing a number of different die patterns on the same reticle to create a multi-patterned reticle. Multi-patterned reticles can be created based on a die size, process monitor and scribe line monitor requirements, and any special embedded resources.  
         [0086]     The method  600  includes an act of designing a custom application (act  603 ) and an act of defining an appropriate die cluster configuration (act  604 ). A die cluster configuration can be defined to meet the resource requirements of the custom application. A die cluster configuration can be defined to include any number of different individual die and can be any of a variety of different arrangements (including square, for example, six-by-six and rectangular, for example, four-by-three). Based on the dimensions of individual die (e.g., 1 mm, 2 mm, etc.), the dimensions of the corresponding die cluster can be determined (e.g., 8 mm, 10 mm, etc.). A designer can utilize an appropriate software application to configure a cluster from die libraries.  
         [0087]     The method  600  includes an act of fabricating custom base wafers (act  606 ) and an act of storing the custom base wafers (act  607 ). At any time, for example, determined by fabrication lead times, custom base wafers are manufactured and subsequently held in inventory (e.g., in a stockroom). Custom base wafers can be fabricated from the multi-patterned recticle, with stepping (or scanning) and blading (or masking sequence) specified by the custom die cluster configuration. For example, during a stepping process, the desired pattern can be selected and exposed. Thus, if there are two die patterns, A and B, on a multi-patterned reticle, rows of individual die can be exposed with the various patterns such as, AAAA, BBBB, ABAB, AAAB, etc. as appropriate.  
         [0088]     The method  600  includes an act of laying out the custom application (act  608 ). For example, after the die cluster configuration is defined, the custom application can be laid out to the die cluster configuration. The method  600  includes an act of creating custom reticles for the custom application (act  609 ). For example, act  609  is similar to act  309  that can be used to create reticle field  227 . Depending on the size of a reticle field and the size of different die clusters, reticle fields of custom reticles can include one or more (potentially different) die clusters.  
         [0089]     The method  600  includes an act of accessing custom base wafers (act  611 ). For example, it may be that previously fabricated custom base wafers are pulled from a stockroom. The method  600  includes an act of fabricating custom levels based on the custom reticles (act  612 ). When appropriate, a reticle field with one or more (potentially different) die clusters can be utilized to customize a base wafer. For example, such a reticle field can be repeatedly printed on customized base wafer  400  to create multiple clusters. The method  600  includes an act of scribing a die cluster (act  613 ). For example, individual die clusters are tested with wafer probe test equipment, with good dies scribed and cut from the customized base wafer.  
         [0090]     Other photolithographic processes such as, for example, laser and e-beam techniques can be used to customize a wafer that has different individual die. When many stripes are printed, a full row of die, such as, for example, as in  FIG. 4B , are created.  
         [0091]     Embodiments of the present invention reduce the tooling NRE required to build a master/universal base for structured ASIC and platform ASIC devices. Embodiments of the present invention can utilize conventional architectures to promote compatibility with conventional design and processing tools and flows. Embodiments of the present invention (possibly significantly) reduce the tooling NRE required to build customized bases for platform ASIC devices, for example, by using a single set of reticles.  
         [0092]     The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes, which come within the meaning and range of equivalency of the claims, are to be embraced within their scope.