High yield is always demanded in IC manufacturing, however, as process variations and random particles are part of the manufacturing process in nature, yield and circuit performance are inevitably impacted by these factors especially in advanced nodes. Even so, there’s often some room to polish designs to be manufacturing friendly. The design for manufacturability (DFM) approach has been taken to optimize designs to minimize process variation impact on the yield and performance. One area gaining success toward yield improvement is VIA (Vertical Interconnect Access) design optimization. There are some technical approaches that designers may take: adding redundant VIA at possible spots without increasing the design area is a proven way to address random particle induced VIA void issues; increasing VIA enclosure area by shifting VIA to an optimum location effectively minimizes masks misalignment induced enclosure issues, and note that shifting VIA needs to consider some complex situations when clustered VIAs constrain each other. There are also other circumstances that need to be considered and handled depending on specific manufacturing process. All these contents will be presented in detail in the paper.
It’s desirable to gain high yield and good performance for memory products. Designers have to do some advanced DFM checking on their designs and fix all the critical design issues to be correct by construction before manufacturing. One of the DFM checking items is the litho hotspot checking, LFD (Litho Friendly Design) is the tool adopted for that checking due to its user friendly interface for designers and being able to be integrated with other tools for the advanced checking flow development. One challenge to enable this checking as the signoff item is the long runtime due to the computing-intensive litho simulation. Multiple ways have been figured out to reduce the runtime, for instance, hierarchical checking flow similar to hierarchical design flow under the assumption that many design blocks are reused on the top level; simulation only on the area selected by weak pattern candidates stored in a pattern matching library; simulation only on the unique pattern area by firstly decomposing the layout. All these approaches always tradeoff between runtime and simulation accuracy and come to use with different expectations as the process gradually matures. This paper introduces another technique to reduce the simulation time. This technique is essentially a pattern matching extended application and will be introduced in detail in the paper.
Standard cells are the most critical and reusable elements to build up the whole chip, therefore foundry has to fully qualify the standard cell libraries to ensure their high quality when releasing to the customers for the chip design. To prevent pattern dependent lithographic difficulty in manufacturing is one target of standard cell qualification and becomes mandatory especially in advanced nodes due to tighter design rules and smaller design size. To identify a lithographic problematic standard cell, we have to take its surroundings within the optical diameter range into consideration because lithographic effects are intrinsically context-dependent. One critical step is to imitate standard cells placements in real designs and consider some important factors like VIA location as it impacts the mask shape directly. When the placement is completed, lithographic simulation is performed by LFD (Litho Friendly Design) to highlight risky locations. Every standard cell has to occur enough number of times to make sure the statistics of possibility of being a problem is reliable. The final statistics will instruct engineers on how to handle the problematic standard cells, either standard cell layouts have to be optimized or building a pattern database to prevent the abutments of particular standard cell combinations.
Chemical-mechanical polishing (CMP) is a key process in integrated circuit (IC) manufacturing. Successful fabrication of semiconductor devices is highly dependent on the final planarity of the processed layers. Post-CMP topography variation may cause degradation of the circuit performance. Moreover, the depth-of-focus (DOF) requirement is critical for lithography of subsequent layers. As such, planarity requirements are critical for maintaining IC manufacturing technology scaling trends, and supporting device innovation. To mitigate post-CMP planarity issues, dummy fill insertion has become a commonly-used technique. Many factors impact dummy fill insertion results, including fill shapes, sizes, and the spacing between both fill shapes and the drawn layout patterns. The goal of the CMP engineer is to optimize design planarity, but the variety of fill options means just verifying the design rules for fill is a challenging task. This data collection currently requires a long development cycle, consuming a great deal of time and resources. In this paper, we show how CMP modeling can help resolve these issues by applying CMP modeling and simulations to drive Calibre YieldEnhancer SmartFill parameters that have been optimized for dummy fill. Additional capabilities in the SmartFill functionality automate CMP hotspot fixing steps. Using CMP simulations, engineers can get feedback about post-CMP planarity for given fill options in a much shorter time. Not only does this move dummy fill optimization experiments from a real lab into a virtual lab of CMP modeling and simulation, but it also provides more time for these experiments, providing improved results.
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