# mcdeviceex02.in : 25-nm n-MOSFFET

Requires: MC Device

Minimum Versions: Atlas 5.28.1.R

This example demonstrates 2D Monte Carlo device modeling of a silicon n-MOSFET without quantum correction.

The first part of the input file specifies the algorithmic parameters of the Monte Carlo model. Many of the same parameters specified in the input file for the bulk example (mcdeviceex01) are used again here. In this case, the number of computational carriers (electrons) is set to 40,000 with the ** N ** parameter on the ** PARTICLE ** statement. ** N ** = 40000 is large enough to adequately sample the spatial distribution of mobile charge in the device. To better sample the tail of the distribution function, use a higher value of ** N ** or statistical enhancement.

On the ** ALGO ** statement, ** DT** = 0.1e-15 s = 0.1 fs is ten times smaller than in the bulk example since the electrons must sense small variations in the 2D doping and field profiles. To get even closer to the steady-state solution, change from ** ITER ** = 2500 to ** ITER** = 25000. With this change, MCDEVICE will take about 10 times longer to run the example, but the averages will be closer to the steady-state solution. As in the bulk case, you may want to change from ** TRANS** = 0 to ** TRANS** = 1000 to obtain a more accurate solution before TIME = 0 when MCDEVICE begins collecting data for its averages. We have kept this example short by using ** ITER** = 2500 and ** TRANS** = 0 so you can experience running a complete simulation in just a couple of minutes.

In this case, ** TSTEP** = 5 on the ** POISSON ** statement indicates that Poisson's equation will be solved every 5 iterations (or every 5 * ** DT** = 0.5 fs). This time must remain short in order for the electrons to properly sample spatial and temporal variations of the electric fields.

The second part of the input file specifies a rectangular tensor product mesh used to represent the physical structure of the device, to solve Poisson's equation, and to help enforce the MC carrier boundary conditions. A finer mesh captures more carrier-carrier interaction. A courser mesh captures less carrier-carrier interaction. In this example, we use a typical size of the 2D mesh for a 25-nm n-MOSFET. This 2D mesh is finer than what is typically used when solving for the steady-state solution of the drift diffusion or energy balance equations for the same device.

The third part of the input file specifies rectangular regions on the mesh. The REGION statements indicate both the material (MAT parameter) and type of region (TYPE parameter). When you specify the regions in your input file, always include regions with the TYPE of OUT, MC, BLOCK, and CONTACT. Please see the MCDEVICE chapter of the Atlas User's Manual for a complete description of the region types and how they control the Monte Carlo solution.

The fourth part of the input file specifies the rectangular current regions used to estimate the current in the device. In this case, the x-directed estimates of the current (dim=1 values in the mcdeviceex02_current.log file) from the first and third regions represent the terminal currents at the source and drain, respectively.

The fifth part of the input file specifies the doping profiles.

The last part of the input file includes a ** SOLVE ** statement. The ** SOLVE ** statement performs the Monte Carlo solve at the voltage biases provided by the ** V<NAME> ** parameters on the ** SOLVE ** statement. Additional commented ** SOLVE ** statements may be used to do perform voltage ramps or obtained solutions at other bias points.

To load and run this example, select the ** Load** button in DeckBuild > Examples. This will copy the input file and any support files to your current working directory. Select the ** Run** button in DeckBuild to execute the example.

## Input Deck

# (c) Silvaco Inc., 2019 go atlas mcdevice # 25-nm MOSFET definition # see http://www-mtl.mit.edu/researchgroups/Well/ # MIT's "well-tempered" MOSFET # Reduce from iter=200000 to iter=2500 to make a short test. # Note that this test will not have fully reached staty-state at iter=2500. algo mode=2 carrier=e iter=2500 dt=0.1e-15 poisson tstep=5 #Turn off enhancement for now! #enhan mode=2 tstep=20 estep=300 xstep=(1,1,0) hithre=10.0 nfrac=0.8 # save output at regular intervals # (-1 will default to a reasonable value) output tstep=500 init=1 \ currentlogfile ="mcdeviceex02_current.log" \ currentramplogfile="mcdeviceex02_current_ramp.log" \ solstrfile ="mcdeviceex02_sol.str" \ summaryoutfile ="mcdeviceex02_summary.out" # Set the maximum number of particles (i.e. electrons). particle n=40000 # X Mesh Lines xmesh node=1 loc=0.0000 xmesh node=45 loc=0.0225 ratio=1.00 xmesh node=145 loc=0.0725 ratio=1.00 xmesh node=189 loc=0.0950 ratio=1.00 # Y Mesh Lines ymesh node=1 loc=-0.0615 ymesh node=6 loc=-0.0015 ratio=0.400 ymesh node=11 loc= 0.0000 ratio=0.800 ymesh node=90 loc= 0.0800 ratio=1.035 # Simulation Box region n=1 mat=SiO2 type=out boundp=(0.0,0.095,-0.0615,0.08) # Substrate region n=2 mat=Si type=mc boundp=(0.0,0.095,0.0,0.08) # Gate oxide region n=3 mat=SiO2 type=block boundp=(0.0,0.095,-0.0015,0.0) # Source contact region n=4 mat=Si type=contact boundp=(0.0,0.0026,0.0026,0.0073) \ name="source" # Drain contact region n=5 mat=Si type=contact boundp=(0.0924,0.095,0.0026,0.0073) \ name="drain" usefermi=1 # Poly gate region n=6 mat=Poly type=contact boundp=(0.0225,0.0725,-0.0615,-0.0015) \ name="gate" # Substrate contact region n=7 mat=Si type=contact boundp=(0.0,0.095,0.0771,0.08) \ name="substrate" # calculate current in cregions cregion boundp=(0.0275,0.0675,0.0,0.08) cregion boundp=(0.0325,0.0475,0.0,0.080) cregion boundp=(0.0475,0.0625,0.0,0.08) ## background doping dopant=B conc=1e15 boundp=(0.0000,0.0950,0.0,0.0800) ## source doping dopant=As conc=2e20 \ boundp=(0.0000,0.0293,0.0, 0.0001) \ char =(0.0040,0.0040,0.0001,0.0170) ## source halo doping dopant=B conc=1e19 \ boundp=(0.0000,0.0293,0.0179,0.0181) \ char =(0.0182,0.0182,0.0160,0.0160) ## drain doping dopant=As conc=2e20 \ boundp=(0.0657,0.0950,0.0, 0.0001) \ char =(0.0040,0.0040,0.0001,0.0170) ## drain halo doping dopant=B conc=1e19 \ boundp=(0.0657,0.0950,0.0179,0.0181) \ char =(0.0182,0.0182,0.0160,0.0160) ## gate doping dopant=As conc=5e20 \ boundp=(0.0225,0.0725,-0.0615,-0.0015) #Uncomment to use surface scattering in this region #ssregion boundp=(0.0153,0.0355,0.0,0.0006) #Make rough=0.0 for the Si-SiO2 interface when using ssREGION #matdef n=4 name="SiO2" eps=3.9 barrier=3.15 rough=0.0 # Do a single solve at vgate=vdrain=1.0 V. solve vgate=1.0 vdrain=1.0 tonyplot mcdeviceex02_current.log -set mcdeviceex02_current_log.set tonyplot mcdeviceex02_sol.str -set mcdeviceex02_sol_str.set # Do a 3-step voltage ramp from vdrain=3.0 V to vdrain=0.0 V. #solve vgate=1.0 vdrain=3.0 name="drain" vfinal=0.0 vstep=-1 # Do a 3-step voltage ramp from vdrain=0 V to vdrain=3 V. #solve vgate=1.0 vdrain=0.0 name="drain" vfinal=3.0 vstep=1.0 # Do a longer 5-step voltage ramp from vdrain=5.0 V to vdrain=0.0 V. #algo iter=7500 #solve vgate=1.0 vdrain=5.0 name="drain" vfinal=0.0 vstep=-1 # Do a second solve at Vgate=vdrain=2.0 V. #output currentlogfile="mcdeviceex02_current2.log" \ # solstrfile ="mcdeviceex02_sol2.str" #solve vgate=2.0 vdrain=2.0 #tonyplot mcdeviceex02_current2.log -set mcdeviceex02_current_log.set #tonyplot mcdeviceex02_sol2.str -set mcdeviceex02_sol_str.set quit