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Graphical Pcell creation help needed

custom

I'm having several problems trying to create a finger cap pcell where the user can size the cell, spacing between metals, width of metal fingers, layers available, and via size. My problems are 1)when I resize the finger width the vias come off the metal (these are flat rectangles)  2) I want the vias to size to whatever the technology allows. Is there a way to do this or will the user have to define the size. (I want to be able to use this no matter the technology). Does anyone know how I can fix these problems?

thanks, Mark

PS - I'm using 6.1.3

  • Hi Mark,

    I think that the best approach would be to change this from graphical to a SKILL-based PCell. One of the reasons that I say this is so that the vias can be actual via objects rather than flat shapes. However I can understand if you are not much of a coder that this could be daunting and perhaps very difficult.  With graphical PCells you can allow more than one shape to be affected by a parameter at the same time, so the distance between vias could be some function of the finger width and number of fingers plus whatever minimum inclusion or spacing values that you need.  I don't have any examples to hand right now for a coded approach but I will look.  Also, I want to make sure that I understand the structure - for your fingered capacitor are the two "plates" like combs that have the "fingers" interleaved, so that the capacitance is a sidewall / lateral effect, and in this case, when you talk about the metal layers, are they the same shape on the layers above (and below)?  By the way, you can pick up values from the technology file for values such as minimum separation and minimum inclusion etc. and have this in the calculation mentioned above, but to be honest, this would be much better done in a SKILL PCell asthis level of coding in a graphical PCell becomes very hard to write, read and debug.

    Regards,

    Lawrence.

  • Hey Lawrence,

    You are correct on both accounts. I am not much of a coder and the combed “fingers” are interleaved and they are the same shape. If you have any examples that would be a great starting place for me to learn. For now I will go read everything there is about doing it in SKILL-based.

    thanks,

    Mark

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