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After creating a pcell, the device size cannot be changed

DS202409251254

I created a pcell for my device, where L is its length and W is its width. But these two parameters did not appear in the schematic and layout, and my device size has always maintained the default values of L and W.So which parameter should I modify in the schematic to make the device dimensions in the layout change accordingly.

  • My assumption is that you have CDF defined for this device. If there is no CDF defined, the create instance and edit properties will show the PCell parameters; if there is CDF, then it will only show the parameters defined in the CDF.

    As a result, when there is CDF defined (use Tools->CDF->Edit and choose "Base") you need to define your PCell parameters (W and L) there too - you should ensure they have the same default values as the PCell defaults too.

    Andrew

  • in reply to Andrew Beckett

    Thanks for your apply. I have now set CDF defined for W and L, with the default value for L being 0.4. When I set L to 0.4 in 'edit instance properties', no error occurred. However, once I set it to a different value, it displays ' pcell eval failed '. Isn't the function of PCell to allow me to scale the size of the device when adjusting parameters? But now, once I change the parameters, errors occur. This is my first time encountering PCell, and I am very grateful for your answer to my question.

  • in reply to DS202409251254

    From the first picture, my assumption is that the PCell parameters are in microns, whereas you've entered the values in metres. Does it work if you put 0.3? (and an appropriate value for W too)?

    Andrew

  • in reply to Andrew Beckett

    oh,it work. Thank you very much for your help.

    Da

  • in reply to Andrew Beckett

    Hi, dear Andrew, the default unit for Pcell parameters is microns. How can I change it to meters.

  • in reply to DS202409251254

    Firstly, the graphical PCell environment is something that we discourage the use of (it's old, and has not had any significant work done on it in many years - in fact there's a warning given in IC23.1 that we plan to remove it in a future release). Instead you should use a more modern tool such as PCell Designer (please speak to your account team) or write SKILL PCells.

    However, if you want to do this, you could set the Name or Expression to be either:

    L*1e6

    (reference dimension still in microns)

    and then on PCell->Parameters->Edit you set the default value (in metres). 

    I would probably set the expression to be:

    cdfParseFloatString(L)*1e6

    and then set the parameter type (on PCell->Parameters->Edit) to be a string rather than float. This tends to work better if you are using CDF and want the same component to work with simulation flows.

    Andrew

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