Simulating Spiral Inductors

Hi,

I am currently simulating a spiral inductor on Si Sbubstrate using both HFSS and ADS however the Q factor i got from simulations is at an unreasonably high value of 30-40 at 2GHz. I have tried other simulation setting like increasing the mesh density etc but still got a similar result. Can anybody provide advise on how to get a better accuracy in the simulation

Any help will be much appreciated

Thank You
Magneto

It's a bit hard to tell from this information, but are you taking into account all the losses? are you using 2D PEC sheets in HFSS rather than a lossy metal?

Most people I've talked to seem to think Sonnet is the best tool for these type of structures, I'm not sure if Sonnet Lite could manage your problem, but if so it is free (or at least it was, I'm sure Jim can tell you more)

Hi, magneto_cool:

Your suspect is right as the reported Q factor of spiral inductors on Si substrate with inductor value of several nH is absolute less than 20 even with a lot of Q-boost techniques included(such as thicker metal, etched substrate, high-resistivity substrate etc).

Your information is not enough for us to judge what's wrong with the modeling methodology, you may like to upload your projects here for us to take a look or you may like to try again with the following points in mind:
1. Metal trace with reasonable thickness and conductivity property should be set rather than using PEC.
2. Conductivity/Resistivity of SI substrate should be set correctly.
3. Choose all the objects(Metal trace and Substrate, Passivation etc) and make sure "Solve Inside" is checked if HFSS is used.
4. Fine mesh for the Metal trace should be used by using Mesh options.

Hope the above-mentioned "general rules" can help you a bit.

Best regards,

magneto_cool shalom,

Are you simulating a symmetric spiral or a non-symmetric spiral ?
Try increasing the aribox size (be generous).
Check you material assignment and properties.
Is the problem with the "L" or with the "R" ?

My best advise is contact your foundary and ask for an HFSS example for your exact process. This will give you a solid HFSS model to learn from.

Regards,
Itai