Known Problems and Solutions in Virtuoso Multi-Patterning Technology
This document describes the known issues with Virtuoso® Multi-Patterning Technology (MPT) and suggests the workarounds for these issues. Each issue is identified by a Cadence Change Request (CCR) number.
Related Topics
CCR 1546323: Cannot automatically change the color or color state of gray shapes in fully locked vias
Description: Prior to ICADV12.2 ISR1, vias were typically color locked on a per-via basis. In ICADV12.2 ISR1, the Property Editor was enhanced to enable via color locking on a per-layer basis. However, this capability requires the use of a new coloring infrastructure that can be read in ICADV12.1 and versions of ICADV12.2 prior to LA6, but not edited. To maintain compatibility with earlier releases, the Property Editor uses full via color locking whenever possible in ICADV12.2 ISR2. Via colors are locked on a per-layer basis only if you explicitly color and lock some layers, but keep at least one layer colored and unlocked. As a result, vias that have a mix of colored and locked layers, and uncolored but colorable layers, are marked as fully locked.
If a design has fully locked vias with any colorable layers that are gray (uncolored), the following situations may occur in ICADV12.2 ISR2:
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Shifting the color of a metal shape touching the via’s gray shape will result in the following warning from the coloring engine:
*WARNING* (MPT-20204): Could not shift color because the cluster contains some lock elements.
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Lock propagation from a wire that touches the via to the via’s gray layer will fail:
*WARNING* (MPT-20204): Coloring engine fails to propagate color information on some vias due to no color state precedence.
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Moving a shape locked to one color to touch an uncolored shape inside the hierarchy, which in turn touches the gray shape of a locked via, causes lock propagation to fail:
*WARNING* (MPT-20204): Coloring engine fails to propagate color information on some vias due to no color state precedence.
You cannot create a hierarchical color lock on a gray shape in a fully locked via in a child:
*WARNING* (MPT-20204): Cannot create a lock on the shape because it already has locked mask1Color. Creating locks on top of shapes that are already locked in the hierarchy is currently not allowed. Ensure that the hierarchical shape is not already locked before creating a lock on it.
Solution: Use the Property Editor to set the color lock state to unlocked for the colorable but gray layers of the via to unlocked.
CCR 1489934: Colored purposes cannot be changed during a session
Description: Only shapes on a predefined purpose in the list given by the explicitColoredPurposes environment variable will be colored by the color engine. Changes to the environment variable are not recognized during the current session.
Solution: Open a new session with the explicitColoredPurposes environment variable set to the correct list of purposes to be colored. For example, this command sets only the shapes on the drawing purpose to be colored by the color engine:
envSetVal( "mpt" "explicitColoredPurposes" 'string "drawing")
CCR 1284731: Mask color representation in the Multiple Patterning assistant cannot be customized
Description: The mask color representation in layout can be customized by setting the display resource file (display.drf). However, the custom colors are not represented in the Multiple Patterning assistant, which can only show the default mask colors.
Solution: There is no workaround available.
CCR 1278844: Outdated coloring is not detected if the design was saved prior to ICADV12.2 ISR2
Description: Outdated coloring can occur when the data is edited with the color engine off, and then is saved. It is possible that outdated coloring in a design that was saved prior to ICADV12.2 ISR2 will not be detected when the design is opened with the color engine activated. When this happens, the Automatic UpdateColor form will not appear and coloring is left in an unknown state, which can result in unusual behavior.
Solution: Save the design using ICADV12.2 ISR2 or a newer release.
CCR 1236699: Recolor All does not always sync color on connected metal within congested routing
Description: In most cases, Recolor All will color all connected shapes on a metal layer with one color. In dense routing areas after Recolor All, overlapping shapes on the same metal layer, primarily Metal1, might not have the same color.
Solution: The workaround is to run Virtuoso IPVS to resolve odd cycle loops.
CCR 1178544: mptReconstructStitch function cannot recreate hierarchical stitches
Description: Stream In and Stream Out now support the translation of stitch objects hierarchically. The mptReconstructStitch function must be run after streaming in data with stitches to reconstruct the stitch shapes. However, mptReconstructStitch does not traverse the layout hierarchy, so hierarchical stitch reconstruction is not currently supported.
Solution: There is no workaround available.
CCR 1177235: Cannot highlight locked shapes in instances using Multiple Patterning Assistant
Description: When Highlight Locked Color is enabled in the Multiple Patterning Assistant, the locked shapes in instances are not highlighted. This is because the Multiple Patterning Assistant Highlight function operates only on top-level shapes.
Solution: There is no workaround available.
CCR 1070535: Select and Unselect on color locked shapes through the hierarchy can pose significant performance degradation
Description: Selecting and deselecting locked color shapes shows significant performance degradation if the circuit is comprised of more than two hierarchies. The functions will traverse down to every hierarchy regardless of whether locked color shapes are present in the hierarchy and will perform exhaustive color state validation, slowing down performance.
Solution: There is no workaround available.
CCR 1050621: Verify — Design is not removing loop markers for pathSegs with Stitching
Description: Stitching is used in Virtuoso to fix multi-patterning odd loop conflicts. Currently, after fixing a multi-patterning odd loop conflict with Stitching, Verify – Design in Virtuoso IPVS mode still reports it as an odd loop violation.
Solution: There is no workaround available.
CCR 1042773: Vias are not displayed in correct stipple dashed outline for NetClass groups
Description: Vias in a precolored NetClass group are not colored with a default stipple dashed outline for grouped shapes. This occurs because only top-level shapes in precolored nets will be shown as grouped shapes with the dashed outline.
Solution: There is no workaround available.
CCR 1004586: Circles and ellipses are not being colored when using Virtuoso MPT for interactive coloring
Description: Virtuoso MPT interactive coloring supports most layout shapes, such as rectangles, polygons, paths, and path segments. However, automatic coloring of circles and ellipses is not currently supported.
Solution: Circles and ellipses are not expected to be used in advanced node designs. Contact Cadence Customer Support if you require this feature.
CCR 993382: Hierarchy flattening command cannot be used on designs with coloring
Description: Designs with coloring from Virtuoso Multi-Patterning Technology (MPT) do not support the Hierarchy Flattening command (Edit—Hierarchy—Flatten) in Virtuoso. When you run hierarchy flattening on a hierarchical design with coloring, the data reaches an inconsistent state. Running subsequent editing commands can result in a warning message, hang, or crash.
Solution: To avoid this problem, do not run hierarchy flattening on designs with coloring. Instead of flattening a cell, replace the instance of the cell with the contents of the cell by doing a simple copy of all the shapes in the cell.
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