powerex22.in : UMOS Device
Requires: Victory Process - Victory Device
Minimum Versions: Victory Process 7.76.1.R, Victory Mesh 1.9.0.R, Victory Device 1.20.0.R
By default Victory Process and Device run on just one processor. To ensure better performance on your computer the following simulation condition simflags="-P all" could be specified in the go line starting Victory Process or Device. This means that all processors available will be used. If you want to use a smaller number of processors you can substitute "all" with a desired number, e.g. simflags="-P 4".
This example demonstrates 2D process simulation and basic device tests for a U-shaped trench MOSFET or UMOS .
UMOS device belongs to family of Vertical MOSFET devices which differ from standard (horizontal) MOSFETs by the fact that the gate is "vertical" and the drain is on the bottom of device. In UMOS, the vertical gate is formed by etching and oxidizing of a deep trench in silicon. The device uses two connections to the source which results in much larger area through which the current can flow. This reduces the ON resistance of the device which allow to handle higher powers than standard MOSFETs. The vertical nature of the UMOS structure allows to achieve good device characteristics with smaller "layout footprint" than conventional power MOSFETs.
Since UMOS is a symmetrical device only half of the structure is simulated. The full structure is later generated using Mirror capability within Victory Mesh .
Most of important geometrical and process parameters of the UMOS structure are parameterized using set capability of DeckBuild which allows easy process and device optimization using VWF.
The key process step, the trench formation, is simulated by combination of two etch models:
- geometrical angled dry etch
- geometrical wet etch with the curvature of the trench bottom specified by RADIUS
This deck takes advantage of Victory Process capability of adjusting volume mesh for specific implant/diffusion steps. It starts with a very coarse volume mesh which allow to speed up epitaxy and trench formation steps. Then additional volume mesh lines are placed in important areas around the trench as well as in implanted areas. Also, the fine grid initially required to capture a sharp peak of N+ Arsenic implant was later coarsened by using Line remove capability of Victory Process.
In this example, in order to decrease simulation time the default analytical model is used for all implant steps. The Monte Carlo implant model is recommended for most real device simulation.
Several parameters of the device structure are extracted along the way and can be used for process optimization.
Finally, the full structure is prepared for device simulation using Victory Mesh . First, the final status of Victory process simulation is loaded, then the structure is mirrored, and remeshed and refined using Delaunay mesh. The finest refinement takes place along the gate to obtain reproducible Vt. The mesh is also refined at other interfaces and along the junction for accurate Breakdown Voltage simulation.
In the end Victory Device is used to extract two basic device characteristics:
- Threshold voltage Vt
- Breakdown voltage BV .
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., 2022 go victoryprocess # Set geometrical parameters of the device # Substrate depth set SUBSTRATETHICK=2 # Substrate doping set SUBSTRATEDOP=3e19 # Half of the pitch set PITCH2=2.4 #Thickness of Epi layer set EPITHICK=4 # Phosphorus concentration in epi layer set EPIDOP=2e16 # Trench slope angle set ANGLE=87 # Half of trench width set TRENCHWIDTH2=0.5 # Trench depth set TRENCHDEPTH=1.5 # Radius at the bottom of the trench as portion of WIDTH2 # This parameter should be 0 < RAD < 0.9 set RAD=0.5 # Radius at the bottom of the trench in microns set RADIUS=$RAD*$TRENCHWIDTH2 # Thickness of nirtide mask used for geometrical etch of "slopped" and "rounded" trench set MASKTHICK=0.5 set PI=3.141593 # Base resolution for etch/depo and oxidation set RESOLUTION=0.04 # Init meshdepth=2 orientation=100 from=0.0 to=$PITCH2 depth=$SUBSTRATETHICK gasheight=10 resolution=$RESOLUTION material=silicon dopants="phosphorus" dopingvalues=$SUBSTRATEDOP surface.z=$EPITHICK # Base volume grid Line x location=0.0 spacing=0.2 Line x location=$PITCH2 spacing=0.2 # Line z location=-2 spacing=0.5 Line z location=0.5*$EPITHICK spacing=1 Line z location=$EPITHICK spacing=0.2 Line z location=$SUBSTRATETHICK+$EPITHICK spacing=1 # Epitaxy time=15 temperature=1100 thickness=$EPITHICK dopants="phosphorus" dopingvalues=$EPIDOP # Form a trench with rounded bottom by combitation of DRY and WET etch steps Deposit material=nitride thickness=$MASKTHICK conformal Etch thick=$TRENCHDEPTH-$RADIUS+$MASKTHICK dry angle=$ANGLE left.to=$TRENCHWIDTH2-$RADIUS+$MASKTHICK/tan($PI*$ANGLE/180.0) ref.z=-$MASKTHICK Etch wet thickness=$RADIUS left.to=$TRENCHWIDTH2-$RADIUS+$MASKTHICK/tan($PI*$ANGLE/180.0) Strip material=nitride #Trench oxideation Diffuse time=30 temperature=1050 dryo2 press=1.00 hcl=3 # Wet etch to adjust gate oxide thickness Etch material=oxide thickness=0.03 wet # # Extract gate oxide thicknesses set MEASUREPOSY=0.5*$TRENCHDEPTH extract name="gateox_bottom" thickness oxide mat.occno=1 x.val=0.05 extract name="gateox_side" thickness oxide mat.occno=1 y.val=$MEASUREPOSY # # Deposit and Etch-back Polysilicon gate set POLYDEPOTHICK=$TRENCHWIDTH2+0.3 Deposit material=polysilicon thick=$POLYDEPOTHICK dopants="phosphorus" dopingvalues="1e20" conformal Etch thickness=$POLYDEPOTHICK+0.02 dry # Add grid lines along the channel extract name="Xgate_position" max.bound oxide mat.occno=1 y.val=$MEASUREPOSY extract name="TrenchBottom" max.bound oxide mat.occno=1 x.val=0.01 set XSP=0.02 Line x loc=$Xgate_position-$RADIUS-$XSP spacing=$XSP Line x location=$Xgate_position+$XSP spacing=$XSP set ZSP=0.04 line z location=0.4 spacing=$ZSP line z location=$TRENCHDEPTH+0.5*$RADIUS spacing=$ZSP #Vt adjust "vertical" doping Implant boron energy=150 dose=5e12 Implant boron energy=300 dose=7e12 Implant boron energy=500 dose=9e12 set BDIFFTIME=60 Diffuse time=$BDIFFTIME temperature=1050 # Add fine grid to capture N+ implant Line z location=0.02 spacing=0.01 # N+ Implant and drive set NplusDOSE=2e15 Implant arsenic dose=$NplusDOSE energy=30 tilt=0 Diffuse time=30 temperature=950 # Adjust vertical mesh after N+ diffusion Line z location=0.1 spacing=$ZSP Line remove z location=0.02 spacing=0.01 # Isolation oxide and recessed etch for P= implant and source contact Deposit material=oxide thick=1 conformal Etch material=oxide right.to=$PITCH2-0.5 dry thickness=2 Etch material=silicon thick=0.5 dry # P+ implant and drive set PplusDOSE=2e15 Implant boron dose=$PplusDOSE energy=25 tilt=0 Diffuse time=15 temperature=1000 #Surface concentration in the "middle" of the vertical gate extract name="SurfC" surf.conc impurity="Net Doping" material="Silicon" mat.occno=1 y.val=$MEASUREPOSY # extract name="J1" xj material="Silicon" mat.occno=1 x.val=$TRENCHWIDTH2+0.2 junc.occno=1 extract name="J2" xj material="Silicon" mat.occno=1 x.val=$TRENCHWIDTH2+0.2 junc.occno=2 extract name="GateLength" $J2-$J1 if cond=($J2 > $TrenchBottom) extract name="Jlat" xj material="Silicon" mat.occno=1 y.val=$TrenchBottom junc.occno=1 if.end # Contact metal deposition Deposit material=aluminum thick=0.3 conformal # Assign electrods Electrode name=gate x=0.05 z=0.5*$TRENCHDEPTH Electrode name=source x=0.05 Electrode name=drain substrate save name=powerex22_vp # Use VictoryMesh to prepare the structure for VictoryDevice simulation go victorymesh load in="powerex22_vp" # Mirror the structure mirror axes="-x" set MaxSIZE=0.5 set MaxMOSSIZE=0.001 set MaxJuncSIZE=0.03 set MaxIntSIZE=0.01 remesh delaunay refine max.size=$MaxSIZE regions="*" refine max.size=0.4*$MaxSIZE regions="material:aluminum" refine max.size=0.2*$MaxSIZE regions="material:polysilicon" refine max.interface.size=$MaxMOSSIZE grading="quadratic" refine max.junction.size=$MaxJuncSIZE grading="quadratic" refine regions="material:sio2" max.interface.size=$MaxIntSIZE grading="quadratic" \ interface.regions="material:sio2" other.interface.regions="material:polysilicon,silicon" save out=powerex22.str tonyplot powerex22.str -set powerex22.set ############# Vt Test : Returns Threshold Volatage ################ go victorydevice mesh infile="powerex22.str" width=10 # set material models models cvt srh print contact name=gate n.poly interface qf=3e10 method newton solve init # Bias the drain solve vdrain=0.1 # Ramp the gate log outf=powerex22_vt.log master solve vgate=0 vstep=0.2 vfinal=5.0 name=gate # extract Vt parameters extract name="Vth" (xintercept(maxslope(curve(abs(v."gate"),abs(i."drain")))) \ - abs(ave(v."drain"))/2.0) extract name="MaxId" y.val from curve (abs(v."gate"),abs(i."drain")) where x.val = 5 tonyplot powerex22_vt.log -set powerex22_vt.set ############# BV Test : Returns Breakdaown volatage ################ go victorydevice simflags="-80" mesh infile="powerex22.str" width=10 models cvt srh print impact selb contact name=gate n.poly solve init method newton climit=1e-4 solve init # log outf=powerex22_BV.log solve vdrain=0.03 solve vdrain=0.1 solve vdrain=0.25 vstep=0.25 vfinal=2 name=drain solve vstep=1 vfinal=10 name=drain solve vstep=2 vfinal=70 name=drain cname=drain compliance=1e-11 extract name="BV" max(v."drain") tonyplot powerex22_BV.log -set powerex22_BV.set quit
