

			A HMOS FET


This example is a simulation of a HMOS mosfet.  This example will show
some tricks one can play with the grid refinement.  It also is a good
example that leads the user sequentially through the subthreshold, linear
and saturation.



The simulation starts with a file called fig03.p2.  This file generates
the mesh and saves it to a file called hmos.msh.  The device has a 1.5um
channel and measures 3um x 2um.  The rectangular grid is distorted using
spread statements.  Electrodes are defined for the gate, substrate, drain
and source.  The substrate doping and source and drain diffusions are
put in using the doping statements.  The file then plots the grid, junction,
and doping contours.



Files fig04.p2 and fig05.p2 are not important to this simulation, but they
are there to show how the final grid is obtained in the file called fig03.p2.



An example of regrid is in the file called fig08.p2.  The file starts with
a rectangular mesh on a device similar to fig03.p2.  The doping and the
interface charge is exactly the same as fig03.p2.  Regriding is done in
the silicon region of the device and the regrid mesh files are saved in
hmos1.msh and hmos2.msh.  Next, instead of performing regriding on the doping,
the regrid is done on the potential.  Since the regrid files are saved
as hmos3.msh and hmos4.msh, the user can compare how the regrid changes
the mesh for both potential and doping.  Regriding on potential after an
intial solution is obtained, refines the triangles showing the greatest
change in potential.



The subthreshold curve is solved for by the file called fig15.p2.  This
file uses the last regrid on potential mesh file (hmos4.msh).  A single
carrier gummel method is used to solve for the intial solution and it is
saved in a file called hmos0.slv.  The remainder of the solution is
obtained using a single carrier newton solution.  A log file called
IVsub.log keeps track of the generated data.  The solution for Vds=0.1 volts
is solved and saved in a file called hmos1.slv.  Next, Vgs is stepped from
-0.5 to 2.0 volts.  The plot gate voltage versus the drain current is then
plotted.



In much the same way the subthreshold curve was obtained, the drain charac-
teristics are solved for in a similar manner.  This time the gate voltage is
first stepped up to 3 volts.  The log file this time is called IVdrain.log.
The drain voltage is then slowly stepped up to 3 volts.  At 3 volts the
solution is saved in a file called hout30.slv.  The drain characteristic
is then plotted.

