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MOSFET Split CV Simulation
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Objectives
==================================================

* learn the basic flows of running device TCAD
* perform split CV simulation
* vary parameters of MOSFET structure to see impact on CV
* using split CV to understand poly depletion effect
* get a feel of computing via command lines
* get to know various scripts


Required Programs 
====================================================

* sde
* sdevice
* tecplot_sv
* inspect


Overview
==============================

See lecture notes on mos capacitor and mosfet capacitors.

Files You Need
=============================

*   the structure specification and mesh generation command file. There
    are two versions. You have used the version with graphical user interface to 
    input structural parameters, which can also be downloaded here
    :download:`mosfet.scm <./mosfetcv/mosfet.scm>`
  
    The other version does not use the GUI. 
    Instead, you will use a text editor to change the parameters. See the 
    tutorial below.
    That file can be downloaded here
    :download:`mosfet_fixed.scm <./mosfetcv/mosfet_fixed.scm>`. 

    
*   In the mosfet_fixed.scm file, an inspection of the program will quickly show that 
    the variables have the following meanings
  
    * w1: "Substrate Width" 
    * w2: "Gate Width" 
    * w3 "Spacer Width"  
    * h1 "Substrate Height"  
    * h2 "Oxide Thickness"
    * h3 "Spacer Height"
    * Nsub "Substrate Doping"
    * xj "S/D Junction Depth"  
    
*   the device simulation command file split_cv_des.cmd, which can also be downloaded here
    :download:`split_cv_des.cmd <./mosfetcv/split_cv_des.cmd>`. It needs to be placed in the same directory 
    as your other files, presumably, ~/mosfetcv, which was created earlier.
    
*   the inspect command file for plotting AC simulated CV curves, cv_ins.cmd, 
    which can also be downloaded 
    :download:`cv_ins.cmd <./mosfetcv/cv_ins.cmd>`.
        
    
  
Video Tutorial
============================

First download all the files above, place them in the mosfetcv folder.

Watch `a 15 minute tutorial`_ I prepared tonight. Do not have my good mic with me. So bare with the default laptop mic. It is audible.

.. _a 15 minute tutorial: http://www.eng.auburn.edu/~niuguof/videos/moscv/moscv.html

Follow the tutorial. You should see CV curves pop up.


Steps
==============================

Meshing
---------

To generate the mesh, first edit structural parameters in the mosfet_fixed.scm file.
If you are on command line, working inside the mosfetcv folder already, just run ::

    gedit mosfet_fixed.scm&
    
After editing, save the file. You do not have to close the editor as it is running in background.

Next, run ::

    sde -l mosfet_fixed.scm
    
You will see sde working to generate the MOSFET mesh, and tecplot displaying the end result. You 
can examine the structure or doping etc inside tecplot. No need to save anything when asked. It has all
been saved with commands inside the command file.

You can then close tecplot and sde programs.


Simulating
----------------

Examine split_cv_des.cmd file first. Set all voltages to desired values. For vp.dc, make 
it stop at 
3V if you are using thin oxide just a few nm thick.
You could modify the start gate voltage to say -3V too.

Then run ::

    sdevice split_cv_des.cmd
    
You should see reporting of solution process. It should take about 1 minute cpu time to finish.


Plotting
-----------------

Examine cv_ins.cmd file first. You do not have to completely understand it, but just a quick look
will give you some useful idea about what it does. You may modify it for your purpose. You are not
required to write such programs. See our notes about how and why we need to take the absolution values of 
certain capacitances. We talked about this in class too. 

For thin gate oxide, set the vdd parameter to a value consistent with the vp.dc set above in the 
split_cv_des.cmd file.  Then, run ::

    inspect -f cv_ins.cmd
    
You should see some nice split CV plots.