Abstract:
Methods for identification and partial re-routing of selected areas (e.g., including critical areas) in a layout of an IC design and the resulting device are disclosed. Embodiments include comparing design data of an IC device against criteria of manufacturing processes to manufacture the IC device; identifying in the design data a layout area based, at least in part, on proximity of metal segments, interconnecting segments, or a combination thereof in the layout area; performing partial re-routing in the layout area to substantially meet the criteria, wherein at least one interconnecting element is shifted or extended; and integrating the partial re-routing into the design data for use in the manufacturing processes.

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to designing and fabricating integrated circuit (IC) devices. The present disclosure is particularly applicable to optimization of layout design of an IC device based on criteria of fabrication processes utilized in fabrication of IC devices. 
     BACKGROUND 
     Generally, manufacturing/fabrication of an IC device includes processing of its design data, which includes physical layout Information of structures such as circuit (e.g., transistors) and interconnecting elements that would form the device, where the data may be provided by a client, or its IC designers, to an IC manufacturing vendor. Typically, a photolithography (lithography) process may be utilized to optically print/pattern various layers of a circuit design onto a surface of a silicon (Si) substrate for creating the various elements and circuits. In lithography, a photomask is used to mask or expose areas on the substrate that are to be, respectively, blocked from or patterned by a light beam, such as light produced by an Argon-Fluoride laser (ArF), Krypton-Fluoride laser (KrF), extreme ultraviolet (EUV), or the like source. 
     A photomask may be developed by use of electron beam (e-beam) lithography, which enables patterning/writing very small patterns on substrates with a high level of precision. Unfortunately, optical proximity effects, along with mask pattern fidelity and photoresist processing limitations commonly cause errors in patterning the desired pattern onto the substrate. To increase viable resolution and pattern transfer reliability, resolution enhancement techniques such as optical proximity correction (OPC) models may be utilized to optimize a photomask for substrate processing. The object of OPC is to make systematic modifications to mask geometry to compensate for systematic errors. However, complex designs and continued efforts to miniaturize the IC devices present various limitations that may negatively impact the manufacturing processes and cause less throughput, less process margin, higher costs, lower yields, or the like issues. 
       FIG. 1A  is a layout illustration of an example IC device. IC designers utilize various electronic design automation (EDA) software tools in designing and analyzing the circuits in an IC device. Additionally, the design tools are utilized to render a layout of the IC design targeting a specific technology node (e.g., 28 nm, 20 nm, 14 nm, etc.) Moreover, an IC manufacturer, or a third party vendor, may use EDA tools to evaluate a client&#39;s IC design data, in a graphic data system file (e.g., GDSII), for determining manufacturability of the IC based on the manufacturer&#39;s production processes criteria and identifying any potential issues therein. Diagram  101  illustrates a layout of different layers in an IC device where a potential critical area  103  is highlighted and shown in greater detail as diagram  105  in  FIG. 1B . As noted, e-beam lithography and OPC may be impacted by an IC design and its layout; therefore, criteria, such as minimum spacing between elements, associated with the lithography and/or OPC may be utilized to identify potential critical areas in the layout. However, potential bridging (e.g., short circuiting) issues exist with the current solution even after new OPC re-targeting. In diagram  105 , a metal segment  107 , such as in a second level metal layer, and two adjacent metal segments  109  and  111  are connected, respectively, to connecting vias  113   a ,  113   b , and  113   c , which are between a first level metal layer segment and a second level metal layer segment. As a short-term solution, the spacing between connecting vias may be formed at an angle of 45 degrees (45°), as shown in  FIG. 1B , to increase the spacing to protect from the bridging issue of the nearby connecting vias after lithography in substrate processing. As shown in diagram  117  of  FIG. 1C , one potential issue may be due to insufficient distances, such as  115 , between the patterns of the connecting vias  113   a ,  113   b , and/or  113   c , where bridges may be formed causing signal interference. Another potential issue may be due to at least one border of the connecting vias  113   a ,  113   b , and  113   c  being at an angle of 45°, as  119  shown in  FIG. 1C , which may increase run times for the associated e-beam lithography and OPC processes. Additionally, a border rendered at a 45° angle may have a distorted edge, as  121 , which may require additional e-beam writer iterations to render a smoother edge  123  as shown in diagram  125  of  FIG. 1D . Although some of the stated issues may be addressed before the design of an IC is finalized (e.g., by an IC designer), it would be challenging and inefficient since the processes employed by different IC manufactures vary. Moreover, a potential bridging may be due to process variations in fabrication of the IC devices. It is noted that the above issues are not limited to any particular metal or any specific connecting via layer and may be associated with all backend interconnection layers. 
     A need therefore exists for a methodology enabling identification and partial re-routing of selected areas, including potential critical areas, in a layout of an IC design and the resulting device. 
     SUMMARY 
     An aspect of the present disclosure is a lithography photomask with partial re-routing of selected areas, including potential critical areas, in a layout of an IC design. 
     Another aspect of the present disclosure is a method for identification and partial re-routing of selected areas, including potential critical areas, in a layout of an IC design. 
     Additional aspects and other features of the present disclosure will be set forth in the description which follows and in part will be apparent to those having ordinary skill in the art upon examination of the following or may be learned from the practice of the present disclosure. The advantages of the present disclosure may be realized and obtained as particularly pointed out in the appended claims. 
     According to the present disclosure some technical effects may be achieved in part by a method including comparing design data of an integrated circuit (IC) device against criteria of manufacturing processes to manufacture the IC device; identifying in the design data a layout area based, at least in part, on proximity of metal segments, interconnecting via segments, or a combination thereof in the layout area; performing partial re-routing in the layout area to substantially meet the criteria, wherein at least one interconnecting element is shifted or extended; and integrating the partial re-routing into the design data for use in the manufacturing processes. 
     In one aspect, the partial re-routing includes forming a staircase-like extension on a portion of each of the metal segments in the layout area. In another aspect, the partial re-routing includes a widening of a portion of each of the metal segments in the layout area. 
     In some aspects, the partial re-routing includes a combination of forming a staircase-like extension on a portion of each of the metal segments in the critical area and a widening of a portion of each of the metal segments in the layout. 
     In one aspect, the staircase-like extension includes diffusing the metal segments in a target layer and corresponding metal segments in at least one adjacent layer in the layout area; and moving portions of the metal segments in opposite horizontal or vertical directions to create a step difference along a linear edge of the metal segments and the corresponding metal segments; and moving an interconnecting element, corresponding to each of the metal segments, aligned with a linear edge of each of the moved portions of the metal segments. 
     In another aspect, the widening includes diffusing the metal segments in a target layer and corresponding metal segment in adjacent layers in the layout area; and adding new parallel sections along a linear edge of each of the diffused metal segments and the corresponding metal segments. 
     In one aspect, the criteria are associated with an optical proximity correction process. In another aspect, the criteria are associated with an electron beam writing process. In a further aspect, the criteria include a minimum distance between connection points of the metal segments in adjacent layers, adjacent connecting metal and via layers, or a combination thereof. In an additional aspect, the target layer and the adjacent layer are created by a single or multiple patterning. In one aspect, parameters for the staircase-like extension and the widening are based, at least in part, on a percentage of a size of the metal segments and the corresponding metal segments. 
     Another aspect of the present disclosure includes a device including a semiconductor layout that includes parallel segments of adjacent metal and via layers; and a via connected to each of the metal segments in a layout area, wherein each of the metal segments include a portion parallel to the corresponding metal segment but adjacent an edge remote from the other metal segment, and the corresponding via connects to the portion. 
     In an additional aspect, the portion for each of the adjacent metal segments includes a widening of the corresponding metal segment in a direction remote from the other metal segment. 
     In some aspects, the portion for each of the adjacent metal segments includes a staircase-like extension of the corresponding metal segment in a direction remote from the other segment. 
     In one aspect, the portion for each of the adjacent metal segments includes a combination of a widening of the corresponding metal segment in a direction remote from the other metal segment and a staircase-like extension of the corresponding metal segment in a direction remote from the other metal segment. 
     Additional aspects and technical effects of the present disclosure will become readily apparent to those skilled in the art from the following detailed description wherein embodiments of the present disclosure are described simply by way of illustration of the best mode contemplated to carry out the present disclosure. As will be realized, the present disclosure is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the present disclosure. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawing and in which like reference numerals refer to similar elements and in which: 
         FIGS. 1A through 1D  illustrate an example layout of an IC device and process issues of current layouts; 
         FIG. 2  illustrates an example process flow for creating a photomask used in substrate manufacturing of an IC device; 
         FIG. 3  illustrates a process flow for creating a photomask including a step for partial re-routing of critical areas in an IC layout, in accordance with an exemplary embodiment; 
         FIG. 4  illustrates a process flow for identifying and a partial re-routing of critical areas in an IC layout, in accordance with an exemplary embodiment; 
         FIGS. 5A through 5E  illustrate layers in an IC device and processes for widening a segment of a structure identified in a critical area of a layout of the IC device, in accordance with an exemplary embodiment; 
         FIGS. 6A through 6D  illustrate a process to add an extended staircase-like feature to a segment of a structure in a critical area of a layout of an IC device, in accordance with an exemplary embodiment; and 
         FIGS. 7A through 7C  illustrate combining a widening and an addition of a staircase-like feature to a segment of a structure in a critical area of a layout of an IC device, in accordance with an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of exemplary embodiments. It should be apparent, however, that exemplary embodiments may be practiced without these specific details or with an equivalent arrangement. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring exemplary embodiments. In addition, unless otherwise indicated, all numbers expressing quantities, ratios, and numerical properties of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” 
     The present disclosure addresses and solves the problems of identifying and partial re-routing of complex and critical areas in a layout of an IC design. The present disclosure addresses and solves such problems, for instance, by, inter alia, analyzing design data of an IC device, identifying complex/critical areas in a target layer in the layout based on criteria of a manufacturing process that will be used to manufacture the IC device, and performing a partial re-route of the complex/critical areas in the target layer as well as pre and post interconnecting layers adjacent to the target layer so that the re-routed areas would meet or exceed the criteria. 
       FIG. 2  illustrates an example process flow for creating a photomask used in manufacturing of an IC device. In a typical IC fabrication process, in step  201 , original design target shapes are drawn based on the circuit target by an IC design house (e.g., input GDSII files). At  203 , the target shapes created during the IC design phase may be evaluated and/or modified based on the manufacturing criteria. Then at  205 , sub-resolution assist features (SRAF) are optimized for maximizing the accuracy and processing window. SRAFs are non-printing shapes that are placed on the mask in proximity to OPC shapes to assist or improve the image quality during photolithography. At  207 , sizing compensations are implemented to improve limits of manufacturing processes and circuit performance. At  209 , the originally drawn or optimized shapes are targeted for the manufacturing process that is to be used in an OPC process. The OPC process at  211  is executed to generate an output file  213  (e.g., GDSII) for the photomask writing. 
       FIG. 3  illustrates a process flow for creating a photomask including a step for partial re-routing of critical areas in an IC layout, in accordance with an exemplary embodiment. The process flow in  FIG. 3  is similar to that of  FIG. 2 , but with some differences. In an additional process step at  301 , potential critical areas in the layout of an IC design may be identified and re-routed based on the manufacturing criteria. The processes of step  301  will be further discussed. Also, processes of step  207  may be performed at a different point in the process flow, for example, after the OPC process at step  211 , which may be an interface (e.g., hand-shaking) between OPC run such as OPC model and recipe. 
       FIG. 4  illustrates a process flow for identifying and a partial re-routing of critical areas in an IC layout (step  301 ), in accordance with an exemplary embodiment. The process may begin at  201  with the originally drawn shapes in the layout of an IC design. At  401 , one or more algorithms may evaluate the layout for identifying critical areas based on criteria of the IC manufacturing process. For example, identifying a critical area may be based on shapes, types, or spacing of structures (e.g., metal segments, connecting vias, etc.) in a given layout area when compared to criteria of the manufacturing process. At  403 , borders of the shapes of the structures in the critical area as well as in surrounding layout area are defined. At  405 , routing schemes of the critical areas are assessed based on criteria of a targeted manufacturing process. At  407 , a critical area on a target layer and in adjacent interconnect layers are extracted. At  409 , partial re-routes of the critical areas (as further illustrated and explained with respect to  FIGS. 5A through 5E, 6A through 6D , and  7 A through  7 C) may be performed in order to meet or exceed the manufacturing criteria, for example, to achieve better manufacturing process margins. At  411 , the partial re-routings are analyzed to determine if the manufacturing criteria are met; for example, with respect to criteria of spacing between adjacent interconnecting layers, maintaining connectivity to upper or lower levels, or the like. If the criteria are not met, the processes at step  409  may be repeated until the criteria are met or are within an acceptable margin, which may be defined by the manufacturer. For example, when re-routing a second or upper level metal layer segment and shifting a connecting via that connects the second or upper level metal layer segment to a first or lower level metal layer segment, the process may also analyze the layout area in adjacent layers to determine if the re-routing has caused any unintended or undesired results in the adjacent layers. Generally, upper and lower level metal layers are in perpendicular layout directions where the re-routing of the upper level metal layer and connecting via may not affect the connection of the lower level metal layer (as the re-routing may be perpendicular to the direction of the metal lines in the metal layer at issue, and therefore along the metal lines in the adjacent metal layer). At  413 , the partial re-routings may replace the original routings so the overall layout may be re-targeted as in step  203 . These process steps and potential solutions for the partial re-routing will be further illustrated and discussed below. 
       FIGS. 5A through 5E  illustrate layers in an IC device and processes for widening a segment of a structure identified in a critical area of a layout of the IC device.  FIG. 5A  illustrates a structure including different level metal layers in a layout of an IC device where a lower (e.g., a first) level metal layer  500   a  may be connected to an upper (e.g., a second) level metal layer  500   b  by a connecting via  501   a . Also, the upper level metal layer  500   b  may be connected to a next upper (e.g., a third) level metal layer  500   c  by a connecting via  501   b . However, the structure and connections therein may be applicable to other level metal layers and connecting vias. 
       FIG. 5B  illustrates an upper level metal segment  502  and adjacent segments  503  and  505 , wherein the segments may be generated by different patterning photomask exposures (e.g., multiple patterning). The segments  502 ,  503 , and  505  may have connectivity to connecting vias  507   a ,  507   b , and  507   c  that may be connected to the upper and lower level metal layers. In one scenario, e.g., at step  401  of  FIG. 4 , the algorithm may analyze distances  509   a ,  509   b , and  509   c  in between the via connections of the upper level metal segments  502 ,  503  and  505 , wherein if any of the distances does not meet (e.g., is less than) the manufacturing criteria, then that layout area may be selected and identified as a critical area in the IC design layout.  FIG. 5C  illustrates the process to widen portions  511  and  513  of, respectively, the upper level metal segments  503  and  505  along parallel edges of the portions where there are connections to the connecting vias  507   a  and  507   b . The process may also include analyzing adjacent layer areas that are close to the widened portions  511  and  513  to determine if there are any adverse effects, such as insufficient spacing, to the adjacent layers.  FIG. 5D  illustrates shifting of the connecting vias  507   a  and  507   b  into new positions  515  and  517  in the widened portions of the upper level metal segments  503  and  505 , where distance  510  is greater than the original distance  509   a ; for example, to meet the manufacturing criteria. In  FIG. 5E , an algorithm may re-evaluate the layout to determine if the partially re-routed structures in the critical areas now meet the manufacturing criteria; for example, distance  519  ( a ) between a widened portion  511  of upper level metal segments  503  and  503   a , or distance  521  ( b ) between upper level metal segments  503  and  505 , or distance  523  ( c ) between a widened portion  513  of upper level metal segments  505  and  505   b . Also, the spacing between shifted segments and adjacent interconnecting layers (e.g., lower metal level and connecting via between upper level metal and a further upper level metal segment) are evaluated or re-evaluated for any unintended results such as a disconnection (e.g., open) between a via and an adjacent (e.g., upper or lower) level metal layer. However, this process is not limited to lower or upper level metal layers or to the connecting vias between them. It may be applied to all level metal and connecting via layers. 
       FIGS. 6A through 6D  illustrate a process to add an extended staircase-like feature to a segment of a structure in a critical area of a layout of an IC device.  FIG. 6A  illustrates the upper level metal segments  502 ,  503 , and  505 , wherein each segment has connection to the connecting vias  507   a ,  507   b , and  507   c . In  FIG. 6B , portions  601  and  603  of, respectively, the upper level metal segments  503  and  505  are moved in opposite directions to create a staircase-like feature along parallel edges of the segments  503  and  505 . Next, in  FIG. 6C , portions  605  are added to each side of the portions  601  and  603  to extend the staircase-like feature. After evaluating the partial re-route, it may be shifted into the original layout where the connecting vias  507   a ,  507   b , and  507   c  may be re-established onto the extended staircase-like portions as shown in  FIG. 6D . Additionally, the spacing between shifted segments and adjacent interconnect layers (e.g., lower lever metal segment and connecting via between upper level metal and further upper level metal segment) may be evaluated or re-evaluated to identify any potential negative impacts to the adjacent layers. 
       FIGS. 7A through 7C  illustrate combining a widening and an addition of a staircase-like feature to a segment of a structure in a critical area of a layout of an IC device.  FIG. 7A  illustrates a combining of the processes discussed in relation to  FIGS. 5A through 5E and 6A through 6D . In  FIG. 7A , the portions  511  and  513  may be added to the staircase-like features of  601  and  603 , respectively. Additionally, in  FIG. 7B , the portions  511  and  513  may be extended by addition of portions  605  to meet the spacing criteria, wherein concave areas  701  and  703  in  FIG. 7C  may be narrower than the areas in  FIG. 7B . Moreover, the spacing between shifted segments and adjacent connecting layers (e.g., lower level metal layer and connecting via between upper level metal layer and the next upper level metal layer) are evaluated or re-evaluated for meeting the manufacturing criteria. 
     It should be noted that although in each of the examples the modification (i.e., the widening and/or addition of a staircase-like feature) is employed symmetrically on segments  503  and  505 , the modifications do not need to be symmetrical. For example, one segment may be widened, whereas the other may not be modified at all. Alternatively, one segment may be widened while the other may include the staircase-like addition or both types of modifications. Also, the widening may be larger on one segment than on the other segment. Further, all of the examples show a critical area including three segments  502 ,  503 , and  505  with three vias, but a critical area is not limited to three segments and three vias. 
     The embodiments of the present disclosure can achieve several technical effects, including improved fabrication and mask-house patterning process as well as e-beam lithography processes utilized in creating photomasks used in manufacturing of IC devices. Further, the embodiments enjoy utility in various industrial applications as, for example, microprocessors, smart phones, mobile phones, cellular handsets, set-top boxes, DVD recorders and players, automotive navigation, printers and peripherals, networking and telecom equipment, gaming systems, digital cameras, or other devices utilizing logic or high-voltage technology nodes. The present disclosure therefore enjoys industrial applicability in any of various types of highly integrated semiconductor devices, including devices that use SRAM memory cells (e.g., liquid crystal display (LCD) drivers, synchronous random access memories (SRAM), digital processors, etc.), particularly for 7 nm technology node devices and beyond. 
     In the preceding description, the present disclosure is described with reference to specifically exemplary embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the present disclosure, as set forth in the claims. The specification and drawings are, accordingly, to be regarded as illustrative and not as restrictive. It is understood that the present disclosure is capable of using various other combinations and embodiments and is capable of any changes or modifications within the scope of the inventive concept as expressed herein.