Patent Publication Number: US-9904757-B2

Title: Test patterns for determining sizing and spacing of sub-resolution assist features (SRAFs)

Description:
BACKGROUND 
     The present disclosure relates to integrated circuit design and manufacturing, and more particularly, to sizing and spacing of sub-resolution assist features (SRAFs) added to integrated circuit designs in photolithographic processing. 
     Sub-resolution assist features (SRAFs) are added to integrated circuit designs to allow lithographically formed structures to be smaller and sharper than the minimum resolution of an exposure system would otherwise allow. Images printed on a photoresist for an isolated lithographic pattern are more sensitive to focus variations than images for a dense lithographic pattern, and such SRAFs are commonly added to main shapes in a photolithographic mask to create a denser environment for robust printing of integrated circuit features. The SRAFs are not intended to be reproduced as distinct features in the photoresist (e.g., they should not print in the photoresist) because SRAFs only perform the function of increasing the focus sharpness of the main shapes of the integrated circuit features that are printed in the photoresist. Therefore, SRAFs can increase the depth of focus or process window, but SRAFs should avoid being formed as separate structures because such structures could transfer to subsequent steps of the chip manufacturing process and cause unintended consequences. 
     Such integrated circuit designs that include SRAF features are modeled (tested using either a computer simulator, or by being subjected to a portion of a full manufacturing process, such as test patterning layers through different test exposure masks) before actually being manufactured, to allow any design defects to be detected and corrected prior to expending resources manufacturing potentially defective integrated circuit designs. Such test masks that include SRAF features are sometimes referred to as SRAF macros, and it is common to test how the different SRAF configuration affect a given integrated circuit design differently, using tens or hundreds of different SRAF configurations (e.g., different SRAF sizes and spacing). Each one of the different SRAF configuration on the macro utilizes SRAFs having a single and uniform shape, size, and spacing, such that each SRAF test case has SRAFs that are shaped, sized, and/or spaced differently from the other SRAF test case that are applied to the given integrated circuit design. The SRAF test case that produces the sharpest focus, without having the SRAFs print in the photoresist, identifies the best SRAF shape, size, and spacing for the given integrated circuit design. However, such processes require designers to make and expose many different SRAF test cases, and to evaluate many different resulting exposed photoresists. 
     A SRAF model is the numerical model that feeds the result of a previous exercise with different SRAF test cases, based on which the model will predict what SRAF configuration will print and what will not print. When building SRAF models, it is common to use images that show transition from non-SRAF printing to SRAF printing. Therefore, a large amount of time is spent designing the SRAF model calibration macro (e.g., the different SRAF test cases) and successful testing is not always guaranteed, because many parameters need to be accounted for with the different test case (SRAFs by themselves only, SRAFs combined integrated circuit features, SRAFs affecting one another, etc.). These parameters can include items such as SRAF size, SRAF to integrated circuit main feature size, SRAF to SRAF size. An exemplary factor that prevents such proper “transition printing” when performing SRAF model building, is that the lithographic development process may not be complete, which can prevent design structure information that accurately captures the transition zone from being known at the time of test mask including the different test case is built. Additional failures in transition printing can occur when engineers attempt to capture too many structures at transition printing zone. 
     SUMMARY 
     Various methods herein receive an integrated circuit design, divide the integrated circuit design into a test portion and a remaining portion, and add sub-resolution assist features (SRAFs) having different size and spacing parameters to the test portion of the integrated circuit design to generate a single test pattern. 
     The SRAFs are positioned between features of the integrated circuit design, and the SRAFs influence and modify how features of the integrated circuit design are printed in the single test photoresist. Features of the integrated circuit design within the test portion have consistent size and spacing parameters in regions where the SRAFs have inconsistent size and spacing parameters. Also, the size and spacing parameters of the SRAFs include SRAF size, SRAF to integrated circuit feature size and spacing, and SRAF to SRAF spacing. 
     Such methods perform a single exposure and development process of the single test pattern to produce a single test photoresist, and analyze the single test photoresist to determine which of the size and spacing parameters are unacceptable size and spacing parameters, and which of the size and spacing parameters are acceptable size and spacing parameters, based on differences between the single test photoresist and a model photoresist that the test portion of the integrated circuit design without the SRAFs would produce. More specifically, unacceptable size and spacing parameters cause the SRAFs to print within the single test photoresist, and the acceptable size and spacing parameters do not cause the SRAFs to print within the single test photoresist. 
     Thus, the analysis of the single test photoresist determines how different ones of the SRAFs affect the test portion of the integrated circuit design. Later, such methods can add SRAFs that have the acceptable size and spacing parameters to the integrated circuit design to produce a production photoresist. 
     Various systems herein include (among other components) a processor that receives an integrated circuit design, divides the integrated circuit design into a test portion and a remaining portion, and adds sub-resolution assist features (SRAFs) having different size and spacing parameters to the test portion of the integrated circuit design to generate a single test pattern. 
     The SRAFs are positioned between features of the integrated circuit design, and the SRAFs influence and modify how features of the integrated circuit design are printed in the single test photoresist. Features of the integrated circuit design within the test portion have consistent size and spacing parameters in regions where the SRAFs have inconsistent size and spacing parameters. Also, the size and spacing parameters of the SRAFs include SRAF size, SRAF to integrated circuit feature size and spacing, and SRAF to SRAF spacing. 
     Such systems also include exposure and development equipment operatively (meaning directly or indirectly) connected to the processor. The exposure and development equipment perform a single exposure and development process of the single test pattern to produce a single test photoresist. The processor analyzes the single test photoresist to determine which of the size and spacing parameters are unacceptable size and spacing parameters, and which of the size and spacing parameters are acceptable size and spacing parameters based on differences between the single test photoresist and a model photoresist that the test portion of the integrated circuit design without the SRAFs would produce. The processor adds SRAFs having the acceptable size and spacing parameters to the integrated circuit design to produce a production photoresist. 
     More specifically, the processor analyzes the single test photoresist by determining how different ones of the SRAFs affected the test portion of the integrated circuit design. The unacceptable size and spacing parameters cause the SRAFs to print within the single test photoresist, and the acceptable size and spacing parameters do not cause the SRAFs to print within the single test photoresist. 
     Various devices herein include a SRAF test case that includes (among other features) integrated circuit design features within a test portion of an integrated circuit design. The integrated circuit design also includes a remaining portion in addition to the test portion. Further, the SRAF test case includes sub-resolution assist features (SRAFs) having different size and spacing parameters within the test portion of the integrated circuit design. 
     The SRAFs are positioned between features of the integrated circuit design, and the SRAFs influence and modify how features of the integrated circuit design are printed in the single test photoresist. Features of the integrated circuit design within the test portion have consistent size and spacing parameters in regions where the SRAFs have inconsistent size and spacing parameters. Also, the size and spacing parameters of the SRAFs include SRAF size, SRAF to integrated circuit feature size and spacing, and SRAF to SRAF spacing. 
     A single exposure and development process of the single test pattern produces a single test photoresist. Analysis of the single test photoresist determines which of the size and spacing parameters are unacceptable size and spacing parameters, and which of the size and spacing parameters are acceptable size and spacing parameters based on differences between the single test photoresist and a model photoresist that the test portion of the integrated circuit design without the SRAFs would produce. 
     The analysis of the single test photoresist determines how different ones of the SRAFs affected the test portion of the integrated circuit design. The unacceptable size and spacing parameters cause the SRAFs to print within the single test photoresist, and the acceptable size and spacing parameters do not cause the SRAFs to print within the single test photoresist. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments herein will be better understood from the following detailed description with reference to the drawings, which are not necessarily drawn to scale and in which: 
         FIG. 1  is a schematic diagram illustrating an exemplary SRAF test case herein; 
         FIG. 2  is a schematic diagram illustrating an exemplary patterned photoresist produced by the SRAF test cases shown in  FIG. 2 ; 
         FIG. 3  is a schematic diagram illustrating an exemplary SRAF test case herein; 
         FIG. 4  is a schematic diagram illustrating an exemplary patterned photoresist produced by the SRAF test cases shown in  FIG. 3 ; 
         FIG. 5  is a graph showing results produced herein; 
         FIG. 6  is a flowchart illustrating the processing performed by various methods herein; 
         FIG. 7  is a schematic diagram illustrating an exemplary system herein; and 
         FIG. 8  is a schematic diagram illustrating an exemplary computerized device herein. 
     
    
    
     DETAILED DESCRIPTION 
     As mentioned above, it is common to test how the different sub-resolution assist feature (SRAF) configuration (number, size, spacing) affect a given integrated circuit design differently, to calibrate a SRAF model to be used to guide the SRAF placement process, using tens or hundreds of different SRAF test case patterns (e.g., different SRAF configuration). Each different SRAF test case utilizes SRAFs having a single and uniform shape, size, and spacing, such that each SRAF test case has SRAFs that are shaped, sized, and/or spaced differently from the other SRAF test cases that are applied to the given integrated circuit design. The SRAF test case that produces the sharpest focus, without having the SRAFs print in the photoresist, identifies the best SRAF shape, size, and spacing for the given integrated circuit design. However, such processes require designers to make and expose many different SRAF test cases, and to evaluate many different resulting exposed photoresists. 
     Therefore, SRAFs should be as large as possible to give us the most benefit, without being large enough to actually print. As noted above, sizing of the SRAFs for specific design features is done with a numerical model that is called an SRAF model. The SRAF model is “trained” to know what SRAF size will print and what size will not print. To train the SRAF model different SRAF configuration (test cases) that contain different sizes, spacing, number, are evaluated. Such test cases should have SRAFs that print and SRAFs that do not print to be useful. All these requirements for the SRAF test patterns make building such SRAF models hard to achieve, and many different SRAF patterns are typically evaluated, which consumes too much effort and metrology, without a guarantee of success. In view of this, the systems, devices, and methods herein provide a way to produce this SRAF test pattern that is easier, conserves recourses and engineering time, and very usefully, is guaranteed to work. The systems, devices, and methods herein allow designers to invest the time to design a comprehensive pattern that satisfies all the requirements for success, and in the end, the measurement time and analyses effort is highly decreased, with a much higher success probability. 
     Thus, numerous issues can arise during testing of a sub-resolution assist features (SRAF) model. For example, a large amount of time is spent designing the SRAF model calibration macro (e.g., the different test masks that are used to test the SRAF) and successful testing is not always guaranteed, because many parameters need to be accounted for with the different test masks (SRAFs by themselves only, SRAFs combined integrated circuit features, SRAFs affecting one another, etc.). In view of these issues, systems and methods herein provide a single test mask pattern for SRAF model calibration. 
     Instead of using many different test masks, each with its own SRAF parameters, where each different test mask relates to a single SRAF parameter, the systems and methods herein use a single test mask pattern that includes such different SRAF parameters (such as different SRAF sizes and spaces, from both integrated circuit features and from other SRAF structures). This single test mask pattern can be exposed on a wafer image, which cuts the data collection time, and makes sure that the transition printing zone is captured. This single test mask pattern includes both SRAFs that print, and those that do not print. 
     Therefore, systems and methods herein combine many SRAF parameters into a single test mask pattern that only requires one image capture from metrology. The metrology time saving is highly useful, as the tool used for research and development is the same tool used for production, so savings in research and development tool time, allows higher production and has a direct and effective economic benefit. Using a single test mask pattern to calibrate and verify a SRAF model cuts down the metrology data collection time, especially compared to the tens or hundreds of test mask patterns used conventionally (when multiple test mask patterns are applied to a SRAF model). This single test mask pattern provides a simpler structure design, requires less space, requires a simpler calibration, and produces higher success rates because the single test mask pattern has a higher chance of capturing the print transition zone, which leads to better SRAF models. 
       FIGS. 1 and 3  illustrate various exemplary SRAF test cases herein.  FIGS. 2 and 4  illustrate various exemplary patterned photoresists produced respectively by the SRAF test cases shown in  FIGS. 1 and 3 .  FIG. 5  is a graph showing results produced herein, and  FIG. 6  is a flowchart illustrating the processing performed by various methods herein. More specifically, as shown in item  180  in  FIG. 6 , various methods herein receive an integrated circuit design in item  180 , divide the integrated circuit design into a test portion and a remaining portion in item  182 .  FIGS. 1 and 3  illustrate two different test portions  100 ,  130  of one or more integrated circuit designs. 
       FIGS. 1-4 and 6  also illustrate (in item  184 ) that such processing adds sub-resolution assist features (SRAFs)  102  having different size and spacing parameters to the test portion of the integrated circuit design  100 ,  130  to generate a single test pattern. As shown in  FIGS. 1 and 3 , the SRAFs  102  are positioned between features of the integrated circuit design  104 . More specifically, in  FIGS. 1 and 3 , the features of the integrated circuit design  104  are illustrated using boxes having crosshatching in the drawings, while the SRAFs  102  are illustrated using shaded boxes. 
     As can be seen in  FIGS. 1 and 3 , features of the integrated circuit design  104  within the test portions  100 ,  130  have consistent size and spacing parameters in regions where the SRAFs  102  have inconsistent size and spacing parameters. Also, the size and spacing parameters of the SRAFs  102  include SRAF size, SRAF to integrated circuit feature size and spacing, and SRAF to SRAF spacing. 
     In item  186 , such methods perform a single exposure and development process of the single test pattern to produce a single test photoresist. The SRAFs  102  influence and modify how features  104  of the integrated circuit design are printed in the single test photoresist. This is shown, for example, in the exposed and developed photoresists  120 ,  140  shown in  FIGS. 2 and 4 . More specifically,  FIG. 2  illustrates a photoresist  120  exposed to the pattern shown in  FIG. 1 ; and  FIG. 4  illustrates the photoresist  140  exposed using the pattern shown in  FIG. 3 . 
     In item  188 , such methods automatically or manually analyze the single test photoresist to determine which of the size and spacing parameters are unacceptable size and spacing parameters, and which of the size and spacing parameters are acceptable size and spacing parameters, based on differences between the single test photoresist and a model photoresist that the test portion of the integrated circuit design without the SRAFs would produce. 
     More specifically, the analysis of the single test photoresist in item  188  determines how different ones of the SRAFs affected the test portion of the integrated circuit design. The unacceptable size and spacing parameters cause the SRAFs to print within the single test photoresist, and the acceptable size and spacing parameters do not cause the SRAFs to print within the single test photoresist. This is shown, for example, in region  110  shown in  FIGS. 1 and 2 . As can be seen in area  110  in  FIG. 2 , portions of some of the SRAFs  102  are printed in the photoresist  120 , while other SRAFs  102  are not printed in the photoresist  120 , and such differences in printing occur because of the different sizes, shapes, and spacings of the SRAFs  102 . 
     Note, that  FIGS. 2 and 4  include the outlines of the SRAFs  102 , and that such outlines are only included in the drawings in order to help the viewer see where the SRAFs  102  would be located within the photoresists  120 ,  140 ; however, such outlines are not actually printed in the photoresists  120 ,  140 , and the only features that actually appear in the photoresists  120 ,  140  are the solid features. 
     In another example, as can be seen when comparing area  112  in  FIGS. 1 and 2 , no SRAFs  102  print in the photoresist  120  in area  112 . To the contrary, in area  114 , some portions of the SRAFs  102  print within the photoresist  120 . As can be seen in  FIG. 1 , the SRAFs  102  in areas  112  and  114  are different because they have different lengths, different widths, they are spaced differently from one another and from integrated circuit features  104 , and there are a different number of SRAFs  102  in areas  112  and  114 . Note however, that the integrated circuit features  104  are consistently sized and spaced in both areas  112  and  114 . The difference in size, spacing, number, etc., between the SRAFs  102  in areas  112  and  114  results in the SRAFs  102  in area  112  not being printed, but the SRAFs  102  in area  114  being printed. 
     As noted above, it is not desirable to have SRAFs print in the photoresist. Therefore, the analysis performed an item  188  classifies the sizing, spacing, and number of SRAFs appearing in the area  112  to be acceptable for an integrated circuit design having the size and shape of the integrated circuit design  104  appearing in area  112  because the SRAFs did not print. To the contrary, the sizing, spacing, and the number of SRAFs in area  114  is considered unacceptable for such sized, spaced, and shaped integrated circuit structures  104  for an integrated circuit design having the size and shape of the integrated circuit design  104  appearing in area  112  because the SRAFs did print. 
     The same is true for areas  132  and  134  in  FIGS. 3 and 4 , where in area  132  in  FIGS. 3 and 4 , no SRAFs  102  print in the photoresist  140 . To the contrary, in area  134 , some portions of the SRAFs  102  print within the photoresist  140 , and such undesirable printing is shown as item  142  in  FIG. 4 . As can be seen in  FIG. 4 , the SRAFs  102  in areas  132  and  134  are different because they are spaced differently from one another and from the integrated circuit features  104 . Note however, that the integrated circuit features  104  are consistently sized and spaced in both areas  132  and  134 . The difference in spacing, etc., between the SRAFs  102  in areas  132  and  134  results in the SRAFs  102  in area  132  not being printed (SRAF sizing and spacing acceptable), but the SRAFs  102  in area  134  being printed, e.g., printed area  142  (SRAF sizing and spacing not acceptable). 
     Also,  FIGS. 3 and 4  illustrate a SRAF  136  that has decreasing size (decreasing width) as it runs between two integrated circuit features  104  that are unchanging in size, spacing, etc. As can be seen in  FIG. 4 , item  140  represents the printing that occurs in the wider regions of SRAF  136 , but does not occur in the more narrow regions of SRAF  136 . This allows the analysis in item  188  to provide an indication of SRAF width that will result in printed features and that which will not (when evaluating situations of integrated circuit features  104  spaced as shown on either side of SRAF  136  in  FIG. 3 ). 
     The indication of SRAF width that will result in printed features (for integrated circuit features  104  spaced as shown on either side of SRAF  136 ) can also be output graphically, by methods, devices, and systems herein, as shown in  FIG. 5 . More specifically,  FIG. 4  includes gauges  150 ,  152 ,  154  along the length of SRAF  136 , and such gauges are shown graphically in the output of  FIG. 5 . Note, that such gauges do not appear in the photoresist  140 , but are only included in the drawings as reference lines. In addition, the output graph in  FIG. 5  includes a linear print threshold line  158  (intersected by the gauges  150 ,  152 ,  154 ) and an aerial image line  156 . Portions of the aerial image line  156  that are to the right of the print threshold line  158  will result in SRAFs printing; however, portions of the aerial image line  156  that are to the left of the print threshold line  158  will not result in SRAFs printing. The output graph shown in  FIG. 5  allows the user to understand that the SRAF widths below gauge  154  will not result in SRAF printing. 
     The methods, devices, and systems herein can output the results of the analysis occurring in item  188  in  FIG. 6  to the user in many different ways. One example is the graph shown in  FIG. 5 . Another example is an image of the photoresists  120 ,  140  shown in  FIGS. 2 and 4 , with the SRAFs shown as outline boxes (as  FIGS. 2 and 4  do). Additionally, the analysis in item  188  in  FIG. 6  can provide absolute or relative measures of acceptable and unacceptable SRAF shape, spacing, and size. Therefore, the size, shape, and spacing thresholds for SRAFs can be output relative to the size, shape, and spacing of other features, or can be output in absolute measures irrespective of any surrounding structures. 
     Later, in item  190 , such methods can add SRAFs that have the acceptable size and spacing parameters to the integrated circuit design to produce a production photoresist to increase focus sharpness of all integrated circuit features in the test portion and the remaining portion. The production photoresist is used to actually manufacture the integrated circuit devices, and is therefore different from the single test photoresist, and the SRAFs in the production photoresist are only those SRAFs that have the acceptable size and spacing parameters. The processing in item  190  can be automatic or manual. Therefore, the user can manually space, size, etc., the SRAF on the existing integrated circuit design, or the processor can automatically only add SRAFs that have acceptable spacing, sizes, and shapes considering the surrounding structures. The user can then be provided an option to alter such SRAFs that have been automatically added to the integrated circuit design. 
     Therefore, rather than having to utilize many different SRAF test masks (each of which includes only one sized and spaced type of SRAF) the devices, systems, and methods herein utilize many different sized, spaced, and shaped SRAFs in a single test mask. This allows a single exposure and development process to produce results for many differently spaced, sized, and shaped SRAFs. 
     Various items herein include a mask that provides a SRAF test case (examples of which are shown in  FIGS. 1 and 3 ) that includes integrated circuit design features  104  within a test portion  100 ,  130  of an integrated circuit design. The integrated circuit design also includes a remaining portion in addition to the test portion  100 ,  130  shown in  FIGS. 1 and 3 . Further, the SRAF test case includes sub-resolution assist features (SRAFs  102 ) having different size and spacing parameters within the test portion  100 ,  130  of the integrated circuit design. 
     The SRAFs  102  are positioned between features  104  of the integrated circuit design, and the SRAFs  102  influence and modify how features  104  of the integrated circuit design are printed in the single test photoresist (as shown in  FIGS. 2 and 4 ). Features  104  of the integrated circuit design within the test portion have consistent size and spacing parameters in regions where the SRAFs  102  have inconsistent size and spacing parameters. Also, the size and spacing parameters of the SRAFs  102  include SRAF size, SRAF to integrated circuit feature size and spacing, and SRAF to SRAF spacing. 
     A single exposure and development process of the single test pattern produces a single test photoresist (as shown in  FIGS. 2 and 4 ). Analysis of the single test photoresist determines which of the size and spacing parameters are unacceptable size and spacing parameters, and which of the size and spacing parameters are acceptable size and spacing parameters based on differences between the single test photoresist and a model photoresist that the test portion of the integrated circuit design without the SRAFs  102  would produce (e.g., a comparison of  FIGS. 1 and 2 , or of  FIGS. 3 and 4 ). 
     The analysis of the single test photoresist determines how different ones of the SRAFs  102  affected the test portion of the integrated circuit design. The unacceptable size and spacing parameters cause the SRAFs  102  to print within the single test photoresist, and the acceptable size and spacing parameters do not cause the SRAFs  102  to print within the single test photoresist. 
       FIG. 7  illustrates various systems herein. Such systems can include various computerized devices  12  connected to various manufacturing equipment  204  through a computerized network  202 . The computerized devices  12  can include servers, mainframes, personal computers, laptops, personal digital assistants (PDA&#39;s), portable electronic devices (such as smart phones, tablets, etc.), etc. The network  202  can include any form of local or wide area network, including wired and wireless networks. The manufacturing equipment  204  may or may not be located at many different locations  206 . The manufacturing equipment  204  can perform any of the manufacturing processing discussed herein, including exposing and developing photoresists. The details of such devices are well-known to those ordinarily skilled in the art, and such details are intentionally omitted herefrom in order to focus the reader upon the salient features of the methods, systems, and devices herein. 
     When patterning any material herein, the material to be patterned can be grown or deposited in any known manner and a patterning layer (such as an organic photoresist) can be formed over the material. The patterning layer (resist) can be exposed to some pattern of light radiation (e.g., patterned exposure, laser exposure, etc.) provided in a light exposure pattern, and then the resist is developed using a chemical agent. This process changes the physical characteristics of the portion of the resist that was exposed to the light. Then one portion of the resist can be rinsed off, leaving the other portion of the resist to protect the material to be patterned (which portion of the resist that is rinsed off depends upon whether the resist is a positive resist (illuminated portions remain) or negative resist (illuminated portions are rinsed off). A material removal process is then performed (e.g., plasma etching, etc.) to remove the unprotected portions of the material below the resist to be patterned. The resist is subsequently removed to leave the underlying material patterned according to the light exposure pattern (or a negative image thereof). 
       FIG. 8  illustrates that the components of computerized device  12  may include, but are not limited to, one or more processors or processing units  16 , a system memory  28 , and a bus  18  that couples various system components including system memory  28  to processor  16 . 
     Bus  18  represents one or more of any of several types of bus structures, including a memory bus or memory controller, a peripheral bus, an accelerated graphics port, and a processor or local bus using any of a variety of bus architectures. By way of example, and not limitation, such architectures include Industry Standard Architecture (ISA) bus, Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA) bus, Video Electronics Standards Association (VESA) local bus, and Peripheral Component Interconnect (PCI) bus. Computerized device  12  typically includes a variety of computer system readable media. Such media may be any available media that is accessible by computerized device  12 , and it includes both volatile and non-volatile media, removable and non-removable media. 
     System memory  28  can include computer system readable media in the form of volatile memory, such as random access memory (RAM)  30  and/or cache memory  32 . Computerized device  12  may further include other removable/non-removable, volatile/non-volatile computer system storage media. By way of example only, storage system  34  can be provided for reading from and writing to a non-removable, non-volatile magnetic media (not shown and typically called a “hard drive”). A magnetic disk drive for reading from and writing to a removable, non-volatile magnetic disk (e.g., a “floppy disk”), and an optical disk drive for reading from or writing to a removable, non-volatile optical disk such as a CD-ROM, DVD-ROM or other optical media can be provided. In such instances, each can be connected to bus  18  by one or more data media interfaces. As will be further depicted and described below, memory  28  may include at least one program product having a set (e.g., at least one) of program modules that are configured to carry out the functions of embodiments of the invention. 
     Program/utility  40 , having a set (at least one) of program modules  42 , may be stored in memory  28  by way of example, and not limitation, as well as an operating system, one or more application programs, other program modules, and program data. Each of the operating system, one or more application programs, other program modules, and program data or some combination thereof, may include an implementation of a networking environment. Program modules  42  generally carry out the functions and/or methodologies of embodiments of the invention as described herein. 
     Computerized device  12  may also communicate with one or more external devices  14  such as a keyboard, a pointing device, a display  24 , etc.; one or more devices that enable a user to interact with computerized device  12 ; and/or any devices (e.g., network card, modem, etc.) that enable computerized device  12  to communicate with one or more other computing devices. Such communication can occur via Input/Output (I/O) interfaces  22 . Still yet, computerized device  12  can communicate with one or more networks such as a local area network (LAN), a general wide area network (WAN), and/or a public network (e.g., the Internet) via network adapter  20 . As depicted, network adapter  20  communicates with the other components of computerized device  12  via bus  18 . It should be understood that although not shown, other hardware and/or software components could be used in conjunction with computerized device  12 . Examples include, but are not limited to, microcodes, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data archival storage systems, etc. 
     Therefore, as shown in  FIGS. 7 and 8 , various systems herein include (among other components) a processor  16  that receives an integrated circuit design, divides the integrated circuit design into a test portion and a remaining portion, and adds sub-resolution assist features (SRAFs) having different size and spacing parameters to the test portion of the integrated circuit design to generate a single test pattern. 
     The SRAFs are positioned between features of the integrated circuit design, and the SRAFs influence and modify how features of the integrated circuit design are printed in the single test photoresist. Features of the integrated circuit design within the test portion have consistent size and spacing parameters in regions where the SRAFs have inconsistent size and spacing parameters. Also, the size and spacing parameters of the SRAFs include SRAF size, SRAF to integrated circuit feature size and spacing, and SRAF to SRAF spacing. 
     Such systems also include exposure and development equipment  204  operatively (meaning directly or indirectly) connected to the processor  16 . The exposure and development equipment  204  perform a single exposure and development process of the single test pattern to produce a single test photoresist. The processor  16  analyzes the single test photoresist to determine which of the size and spacing parameters are unacceptable size and spacing parameters, and which of the size and spacing parameters are acceptable size and spacing parameters based on differences between the single test photoresist and a model photoresist that the test portion of the integrated circuit design without the SRAFs would produce. The processor  16  adds SRAFs having the acceptable size and spacing parameters to the remaining portion of the integrated circuit design. 
     More specifically, the processor  16  analyzes the single test photoresist by determining how different ones of the SRAFs affected the test portion of the integrated circuit design. The unacceptable size and spacing parameters cause the SRAFs to print within the single test photoresist, and the acceptable size and spacing parameters do not cause the SRAFs to print within the single test photoresist. 
     The method as described above is used in the fabrication of integrated circuit chips. The resulting integrated circuit chips can be distributed by the fabricator in raw wafer form (that is, as a single wafer that has multiple unpackaged chips), as a bare die, or in a packaged form. In the latter case, the chip is mounted in a single chip package (such as a plastic carrier, with leads that are affixed to a motherboard or other higher level carrier) or in a multichip package (such as a ceramic carrier that has either or both surface interconnections or buried interconnections). In any case, the chip is then integrated with other chips, discrete circuit elements, and/or other signal processing devices as part of either (a) an intermediate product, such as a motherboard, or (b) an end product. The end product can be any product that includes integrated circuit chips, ranging from toys and other low-end applications to advanced computer products having a display, a keyboard or other input device, and a central processor. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. In the drawings herein, the same identification numeral identifies the same or similar item. The descriptions of the various embodiments of the present invention have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein was chosen to best explain the principles of the embodiments, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.