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Creating circle in Virtuoso

zhengli
Hi, Can any one help me how to create a circle snapping to manufacturing grids defined in the technology file? I want to create a circle shape in virtuoso layout editor XL included in iCC 6.1.3. I found out that circle is actually created as a polygon. The problem is that when I export the layout into GDSII file, the ending points of the circle does not snapping to the manufacturing grids. I tried to create several real polygons, it is snapping to the grids. So I was wondering if there should be some additional setting to force circle shape snapping to grids. Please let me know if there is any solutions. Thanks a lot
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  •  Hi,

    Unless I am mistaken, it is not mathematically possible to snap a circle so that it is all on grid, but this might just be the terminology that you are using.

    After creating a circle you can use Edit -> Advanced-> Convert to Polygon to manually control the conversion of ellipses, donuts and circles to polygonal shapes.  There is a setting "Conic Sides" on the Layout Editor Options form which defaults to 20, but you can try other values. This is also available as a .cdsenv variable setting, for example:

    layout numSides int 20

     I hope that this information helps you.

    Regards,

    Lawrence.

Reply

  •  Hi,

    Unless I am mistaken, it is not mathematically possible to snap a circle so that it is all on grid, but this might just be the terminology that you are using.

    After creating a circle you can use Edit -> Advanced-> Convert to Polygon to manually control the conversion of ellipses, donuts and circles to polygonal shapes.  There is a setting "Conic Sides" on the Layout Editor Options form which defaults to 20, but you can try other values. This is also available as a .cdsenv variable setting, for example:

    layout numSides int 20

     I hope that this information helps you.

    Regards,

    Lawrence.

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