deep trench capacitors in GPDK45nm

[legendkiller]

Hi
I am using GPDK45nm technology for my design. I am thinking of simulating a DRAM memory cell. But problem is i cannot find deep trench capacitors that gives about 30-50f F to store the charge. I am onl able to use the default mimcap which needs a very large area for the required cap. could anyone point me to a way i can add a deep trench capacitor to the library. I am totally in the dark about adding new models. i am guessing u must need the capacitor coeffs and other data for adding the model? or does anyone know of any PDK available to students that support deep trench caps.


also pls point me if I understood something wrong above.

 

[legendkiller]

So I got a reply from cadence forum that I should be doing the following to introduce my own device.
you would need to introduce some different layer to indicate that this is different. You'd then need to modify the pcell to alter how the layout is drawn, alter the simulation models to reflect the higher capacitance per unit area, the CDF callbacks to compute dimensions from capacitance, and so on.

I am right now in the process of trying to access the cadence manuals dealing with the creation of PDKs through my univ. So if any one could add anything to the above, it would be gr8....

anyone know how to add a new layout for the device I am going to create? any resource you could point to?

 

[erikl]

anyone know how to add a new layout for the device I am going to create?

Just draw it like the layout for a different device: using the necessary technological layers + an extra layer for the deep trench etch, draw the layout for a single trench capacitor and make a corresponding cell from it.

any resource you could point to?

Don't know if this is helpful: View attachment Automatic_Creation_of_a_Customized_PDK_for_90nm.pdf

 

[legendkiller]

so I add a new layout for the device like u said in the GPDK library and give it a name like trenchmimcap......now i would have to make it get detected as a device model right how do i go about doing that... and I need to have a higher capacitance for the model. I assume i do that in the gpdk045_mimcap.scs..

section cap

subckt mimcap (n1 n2)
parameters w=1u l=1u
+ cmim_para=(w * l) * 1.025e-3 + 2 * (w + l)* 2.425e-10
model cmim_cap capacitor c=1.0f cj=1e-3 cjsw=1e-10 coeffs=[6.16e-5 -2.05e-5] tc1=-5.225e-5 tc2=1.00e-8 tnom=25
c1 (n1 n2) cmim_cap c=cmim_para*mimfacator
ends mimcap

endsection cap

i replace one of the coefficients in the above lines to reflect higher capacitance. and give it the corresponding device name..right?

 

[erikl]

I think so, this is for simulation purpose. You also need a symbol view for your schematic, which points to your trenchmimcap model.

If you wish to run DRC & LVS, you have to update the corresponding files, which needs to understand their syntax. If so, update your DRC file to find and check the new layer (min/max dimensions, spacing to other layers ...), and update extract rules in order to find (recognize), extract and check the trenchmimcap's dimensions and compare it to its schematic properties. You also need an LVS view (copied symbol view, I think).

If you always use the same trenchmimcap cell, you can suppress its full extraction/check by using a corresponding view order in the extraction stop list. And for DRC you then just need to check the min. spacing to other layers.

Get the necessary views by copying e.g. the mimcap views, and change them to your trenchmimcap name & properties.