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inductor model - variation of inductor at different models

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fanshuo

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inductor model

Hi,
I found in my model file that the variation of inductor at different models could be up to +-15%. And the parasitic resistance and capacitance are correlated(when Rs is max,Cox is min and vice versa)
I can not find any theoretical explanation on the big variation of L and the correlation.
Are these numbers are trustworthy?
 

inductor model

Modelling of an inductor can be done in various ways, wht type of model can be used is depends upon the design methodology and the end objective of the circuit design.
 

inductor model

I am not going to model the inductor
I just need to use the model of inductor which provided by the foundry
 

inductor model

Then use the technology file details provided by the foundry
 

inductor model

As I said,
I can not explain the big variation of the inductance value. What could be the possible reason?
 

Re: inductor model

It could be attributed to a variety of reasons. For example, what is the process node you are working on? Or which are the metal thickness and width variations for this process?

Another reason for this big variation could be the poor inductor modeling offered by the specific PDK. Generally, foundry inductor models may not be as trustworthy due to the characterization process applied and issues related to de-embedding that are not efficiently addressed. Needless to say that those models are topology-agnostic since they do not account for mutual coupling phenomena.

--padpan
 

inductor model

Thanks!
I am working on 0.13um
top metal thickness is 2um
I check the graphs provided by the foundry
it seems the model is good at typical situation
But no data found on corners from measurement
 

Re: inductor model

What's the metal thickness and width variation? Those parameters are expected to dominate L variations...

--padpan
 

inductor model

well
what I found from the process manual is that its metal length can varies for 15%,which cause the inductance to vary
According to my opinion, the metal should have a accurate control.It should not vary 15%
 

Re: inductor model

they probably refer to the overall spiral length variation. This may come up when the inductor dimensions are not precisely taped out during fabrication but still this is a huge variation... What's the Q variation by the way? If L is 15%, Q will be by far higher...

--padpan
 

inductor model

of course Q would be more.
But I cannot find it in the process manual.
I have no idea why the variation is this big

Also according to the manual, the series parasitic resistance increases when parasitic capacitance decreases.
I do not know why those two parameters are correlated.
 

Re: inductor model

I suppose it refers to the width. If the conductor gets wider its capacitance increases and resistance decreases and vice versa...

--padpan
 

inductor model

to padpan,
ok I see.
Thanks.

But still the width does not effect the L value.
Do you have any idea of why the length varies a lot?
 

Re: inductor model

It's huge variation. Frankly, I have no idea. Perhaps the foundry wants to extend the variation range to avoid customer complaints in case of inconsistency of the PDK model against measured silicon...

--padpan
 

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    fanshuo

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