Plotting Vth while sweeping L from the tree

[salma shabayek]

.measure dc vth

i tried plotting Vth while sweeping L from the tree when clicking the result browser
but it appears constant it neither increase nor decrease ..i want to check also the curves if there is halo doping or not but it stays constant ...so anybody have any idea how could i fix this?

 

[yschuang]

Re: Plotting Vth against L

What simulator are you using ? In hspice, I usually set the length to be a parameter. Then you can sweep the length.

mn dn gn sn bn nmos L=L1 W=W1 M=1
.param L1=0.2u W1=2u

.probe vth = par('LV9(mn)')

 

[jianjing526]

Plotting Vth against L

There are several standards to estimate the vth of a MOSFET. Which is your choice? Hspice simulation result is just the default one. Or you can measure it from the i-v curve.

 

[salma shabayek]

Re: Plotting Vth against L

I am using SPECTRE as the simulator .

 

[oermens]

Re: Plotting Vth against L

i tried plotting Vth while sweeping L from the tree when clicking the result browser
but it appears constant it neither increase nor decrease

what folder are you getting vth from? if it is from modelParameter-info then you will be getting `vtho` which is nominal vth for the model. i tried with nmos transistor, Vg=Vd=VDD, Vs=0, made length a variable and did dc sweep on that variable from lmin to lmax, plot from results browser->dc-dc->T0/vth and saw change in vth with l. to do this you need to save dc op point and have a line such as 'save * sigtype=all' an include file.

 

[standup]

Re: Plotting Vth against L

hello，I do the simulation as you given, but I can't understand the last line
"have a line such as 'save * sigtype=all' an include file", Can you explain how to set in spectre?
Thank you very much!

i tried plotting Vth while sweeping L from the tree when clicking the result browser
but it appears constant it neither increase nor decrease

what folder are you getting vth from? if it is from modelParameter-info then you will be getting `vtho` which is nominal vth for the model. i tried with nmos transistor, Vg=Vd=VDD, Vs=0, made length a variable and did dc sweep on that variable from lmin to lmax, plot from results browser->dc-dc->T0/vth and saw change in vth with l. to do this you need to save dc op point and have a line such as 'save * sigtype=all' an include file.

 

[oermens]

Plotting Vth against L

create a file, i named mine saveop.scs, and add that line to it and save it somewhere convenient. then i added that file after my model file in ade->setup->model file.

 

[kidmanbasha]

Re: Plotting Vth against L

oermens, what does the command that you stated do in comparison with the save M0 : oppoint command?

 

[oermens]

Re: Plotting Vth against L

from $CDS_TOP_DIR/MMSIM/doc/spectreuser/spectreuser.pdf

save * sigtype=all

Saves all node voltages, subcircuit terminal
currents and all available device information
including terminal currents and operating point
parameters.

for some reason save *ppoint didn't work for me, i would have to put instance names explicitly.