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Other CAD Tools >> Physical Verification, Extraction and Analysis >> Extract a non-regular resistor with Assura
https://designers-guide.org/forum/YaBB.pl?num=1305734300

Message started by ywguo on May 18^th, 2011, 8:58am

Title: Extract a non-regular resistor with Assura
Post by ywguo on May 18^th, 2011, 8:58am

Hi Guys,

I am trying to extract a non-regulat resistor with Assura. It reports "Mal-formed Device" and stops. I will attach the schematic and layout in the following. Any comments are appreciated.

Yawei

Title: Re: Extract a non-regular resistor with Assura
Post by ywguo on May 18^th, 2011, 9:00am

The layout of the 4 resistors is a continuous poly silicon strip, instead of 4 poly strips connected by metal path and contacts.

Title: Re: Extract a non-regular resistor with Assura
Post by ywguo on May 18^th, 2011, 9:01am

It is zoomed in to show the detail of the tap.

Title: Re: Extract a non-regular resistor with Assura
Post by boe on May 19^th, 2011, 7:46am

Ywguo,
it seems your PDK does not support this.

B O E

Title: Re: Extract a non-regular resistor with Assura
Post by ywguo on May 19^th, 2011, 7:31pm

B O E,

You are right. I don't think that PDK has a non-rectangular shaped resistor pcell. But is it possible to modify Assura/Calibre runset so that this is recognized?

Thanks
Yawei

Title: Re: Extract a non-regular resistor with Assura
Post by boe on May 20^th, 2011, 1:08pm

Ywguo,

It is not only a question of the pcell.

You should decide how to handle the following problems:
How do you want your non-rectangular resistor to be extracted? What is its value(s)?

With answers to that you can try to write rules for Assura or Calibre implementing that.

B O E

Title: Re: Extract a non-regular resistor with Assura
Post by rfidea on May 21^st, 2011, 12:37am

Why just not put four real resistors in the layout and connect them by metal1? Probably you can put the contact areas on top of eachother to save some length if that is your problem.

Title: Re: Extract a non-regular resistor with Assura
Post by rf-design on Jun 6^th, 2011, 5:46am

Multitap resistors is a typical examples where standard analog techniques and minimum designkits are conflicting. Typical designkits serve the bare minimum analog design. They exclude many good analog methods and there modelling hide often important technology effects worth knowing because of liability reasons.

The multitap poly resistor requires a complete separation of the pure poly resistor rectangle and a second poly resistor tap rectangle. The extracted net where the tap contact the poly bar must be created by separating the poly bar into multiple resistor recognition rectangles touching each other. The touching line with the poly tap rectangle produce a T-form. For precision application there is a nonlinear correction function with change the pure rectangle extraction values of the three resistors depending on the width ratio of the tap to the bar.