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EMT 471/3 – Semiconductor Physics
Laboratory Module
BASIC LAB 1
INTRODUCTION TO BASIC PROCESS SIMULATION USING
TSUPREM4 & TWB
1. OBJECTIVE:
1.1
1.2
1.3
To introduce students to Synopsys TCAD software.
To familiarize students with Taurus WorkBench (TWB).
To introduce students to PMOS Process Simulation using TWB, and TSUPREM4
2. INTRODUCTION
Synopsys Taurus Workbench is a virtual IC factory that simulates semiconductor
manufacturing processes and predicts product characteristics. Taurus Workbench is part of
the Taurus Modeling Environment (TME), a unified scripting infrastructure that combines
Taurus Visual, Taurus Workbench, and Taurus Layout. A brief introduction of each tool
follows:
2.1 Taurus Visual (TV)
Taurus Visual (TV) is used to visualize results generated by physical simulation software
tools in one (1D), two (2D), and three dimensions (3D). You may visualize data for an initial
understanding and analysis, then modify the plots to gain a new perspective.
2.2 Taurus WorkBench (TWB)
Taurus WorkBench is a virtual IC factory that simulates semiconductor manufacturing
processes and predicts product characteristics. Taurus Workbench provides simulation
management and data management so that the engineer can easily and efficiently predict
product characteristics. Utilities include, statistical analysis, plotting, visualization,
optimization; and aids the engineer in exploring, refining, and centering a design. Job
farming allows simulations to be executed in parallel across a network for faster results
2.3 Taurus Layout
Taurus Layout is an interactive program that provides a direct interface to mask layout
information for a variety of Synopsys TCAD simulators including TSUPREM-4. Taurus
Layout also can be used within the Taurus WorkBench environment
3. COMPONENTS AND EQUIPMENTS
i.
ii.
Synopsys Taurus TCAD software
High-end PC
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4. PROCEDURE
4.1 CREATE A NEW PROJECT
4.1.1
Open new terminal and type ‘twb’ to invoke Taurus Workbench. A new twb
workspace will appear as in the figure below.
4.1.2 Go to ‘Project’  ‘New’  ‘Project’. A ‘NEW’ Project will be shown in the
workspace as follow.
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4.1.3
Laboratory Module
Select the ‘NEW’ project, right click to rename the project, click on ‘Edit name’,
change the project name to ‘LAB1’
4.2 CREATE A NEW EXPERIMENT
4.2.1 Select ‘LAB1’ project, right click and choose ‘New Experiment’
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4.2.2. A ‘NEW’ experiment will appear under ‘LAB1’ project. You need to rename the
experiment by selecting ‘NEW’ experiment and repeat step number 3. Fill in the ‘pMOS’
as the experiment name.
4.2.3 Double click on ‘pMOS’ to invoke twb Experiment window. It consists of a
complete simulation flow including Process Recipe and Wafer Flow, plus ToolKit and
Drivers Tap.
i. Project: The repository for Experiments and Libraries.
ii. Experiment: A complete simulation flow including Process Recipe and Wafer Flow,
plus ToolKit and Drivers (Figure 1.0).
iii. Process Recipe: The simulation recipe is constructed as a graph of Modules that
are either linear or contain splits. For example, multiple Modules at one or several
levels of the graph are displayed in the left panel of the Experiment window
(Figure 1.1).
iv. Wafer Flow: The wafer tree is a graphical data base viewer showing the simulation
status and availability of simulation results. Each Module of the Process Recipe
produces a Wafer at completion. The Wafer is a collection of data representing the
simulation results of a corresponding Module.
v. Module: A self-contained and context-independent part of a Process Recipe that
can be stored in libraries and reused in other simulations. A Module contains
commands and parameters to describe simulation data. It uses a Driver to perform
the simulation.
vi. Drivers: This Driver includes the UNIX shell script command to invoke a simulator,
the load command to load a structure file from previous simulation, and the save
command to save the structure file for further simulation.
vii. ToolKit: An experiment-specific set of tools. Each Tool is invoked interactively and
applies to a selection of Wafers. It is typically a graphical editing or visualization
program.
Figure 1.0: Structure of TWB Experiment.
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Figure 1.1: Actual TWB Experiment Window
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4.3 TAURUS LAYOUT: LAYOUT EDITOR
Now we will learn how to use the interactive features of Taurus Layout. These features allow
you to create, import, and pass IC mask information to a variety of Synopsys TCAD
simulators.
4.3.1
Go back to the ‘Edit’ panel and choose ‘Layout’ button. It will bring up a ‘Cross
Section Editor’ window, select the ‘Edit Layout’ to invoke Taurus-Layout main
window (Figure 1.2).
Figure 1.2: Taurus-Layout main Window
4.3.1 Information related to the Taurus-Layout main window are given below.
Feature
Menus
Mode Buttons
Tools Icons
Definition
Notice the menus across the top of the main window. Press
and hold the MENU mouse button on each of the menus (File,
Edit, and View) to see the choices.
The Mode buttons near the top left corner of the main window
allow you to switch between Mask, Structure, or IWB modes.
Structure is the default mode.
The Tools icons on the left side of the window allow you to
pan, zoom, draw polygons, define simulation regions, and so
on.
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Magnification
The Magnification field shows the magnification factor
when zooming the view of a mask layout. Initially, this
field displays a default value of 1.0.
Cursor Location
The Cursor Location field shows the X, Y coordinates
of the cursor when the cursor is in the central display
area.
Central Display
Area
The large rectangular area dominating the main
window is the central display area where Taurus
Layout displays the mask layout’s polygons. Horizontal
and vertical scroll bars are provided for panning the
mask layout.
The status line at the bottom of the main window displays various status messages. When Taurus Layout
is first invoked, the status line displays the current
version of the program. When you begin using Taurus
Layout, other information appears on this line.
Status Line
Mask Layers
4.3.2
Laboratory Module
The Mask Layers list appears to the right of the main
window and serves to label the polygons displayed in
the central display area. The colors, patterns, and
mask layer names are all user-changeable, as
described in “In this section, you learn how to use
Taurus Layout to make changes to the mask layer
properties. You may use the vertical scroll bar to scroll
through the Mask Layers list.
i.
Mask button to place Taurus Layout in Mask mode. Use this mode to prepare
input files for TSuprem4.
ii.
Structure button to place Taurus Layout in Structure mode. Use this mode to
create 2D and 3D structures.
iii.
IWB button to place Taurus Layout in IWB mode. Use this mode to create .tl2
files with Taurus-Lithography or Taurus-Topography 3D AAM for use with
Synopsys TCAD’s Interconnect WorkBench product.
When you click a Tools icon (Figure 1.3), a short explanation appears in the status
line at the bottom of the main window.
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Figure 1.3: Tools icon
ICON
FUNCTION
Select and highlight any polygon
appearing in the central display
area of the main window.
Select Polygons
Pan Layout
Pan the layout.
Zoom
Zoom in or zoom out of the layout.
Using left-mouse-button to zoom
in,
Using middle-mouse-button to
zoom out.
Draw Rectangles
Draw simple rectangles directly in
Taurus Layout.
Draw Polygons
Draw irregular polygons directly in
Taurus Layout.
Sim. Point
Define a simulation point.
Sim. Line
Define a simulation cut-line.
Sim. Rect
Define a simulation rectangle.
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4.3.3. Below is how to draw layout, allow you to edit the mask layers properties and rename
the mask layers (see Figure 1.4).
i.
In the Taurus Layout window, click on ‘Mask’ button to place Taurus-Layout in
Mask mode.
ii.
Refer to the Mask Layers list on the right side of the main window. Notice that
Taurus Layout has automatically provided default layer names for those layers
containing at least one polygon, and has moved those layers to the top of the list.
iii.
You may double click on the Mask Layer to change the mask layer names as
follows:
 Change ‘UNDEF_0’ to ‘source’
 Change ‘UNDEF_1’ to ‘metal’
 Change ‘UNDEF_2’ to ‘contact’
 Change ‘UNDEF_3’ to ‘active’
 Change ‘UNDEF_4’ to ‘poly’
Figure 1.4: Taurus Layout main window
iv.
Select ‘source’ under the Mask Layer and click on ‘Draw Polygons’ icon to start
drawing the source layout (Figure 1.5)
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Figure 1.5: Start drawing the first layout
v.




Draw the other layers with following coordinate (refer Figure 1.6),
metal layer (1.8 , 1.4) (3.4 , 3.2)
contact layer (2.0 , 1.6) (3.2 , 3.0)
active layer (0.0 , 0.8) (3.2 , 3.6)
poly layer (0.0 , -0.6) (1.0 , 4.8)
vi.
You may change the sequence of the mask layers. This affects the order in
which the layer names appear in lists and the display of polygons in the central
display area of the Taurus Layout main window.
vii.
To change the layer sequence, click the name of a layer and then click one of the
Move Layer buttons. For example, to move the Contact layer to the top, click
the “Contact” layer name in the Mask Layer Properties window, then click the
Top button in the Move Layer panel of the Mask Layer Properties window.
viii.
The Contact layer’s two polygons now appear on top in the central display area
of the main window. Also, the list of mask layer names now appears as follows in
the Mask Layer Properties window (as well as in the main window):
contact…
active…
Poly…
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Figure 1.6: Complete layout drawing in Taurus Layout
ix.
4.3.3
Before saving your layout, define your simulation line and simulation
rectangular. It is require you to save the layout in .tl1 and .tl2 format. You can
close the layout window once finished.
Before saving the layout, you have to define a simulation rectangle first. Go to
Taurus-Layout main window; define the simulation rectangle as follow.
Figure 1.7: Simulation rectangle
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4.3.4
Laboratory Module
To save the Taurus Layout using the Simulation Rectangle, execute ‘File’ > ‘Save
Layout To .tl2’ from the Taurus Layout main window menu Bar. This will open the
Define Simulation Rectangle window as shown below (Figure 1.7). Define the file
as ‘pmos1:0_0.tl2’. Click OK to save the layout file.
Figure 1.8: Define Simulation Rectangle window
4.3.5
To save the layout using the simulation line, you have to do simulation cut-line as
follow.
Simulation cut-line
Figure 1.9: Simulation Cut-Line
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4.3.6
To define a simulation cut-line, you have to generate a corresponding .tl1 file
4.3.7
Click the ‘Sim. Line’ icon in the Taurus Layout main window to open the Define
Simulation Cut-Line window as shown in Figure 1.10 below, save the file as
pmos1:0_0.tl1. Define a simulation cut-line, and click OK to save the cut-line (.tl1)
file.
Figure 1.10: Define Simulation Cut-Line window
4.3.8
You can quit Taurus-Layout now.
4.4 IMPORT MASK LAYOUT FILE
4.4.1 In the Cross-Sections Editor window, click on ‘import from file’ button to import the
layout file ‘pmos1:0_0.tl1’.
4.4.2 ‘pmos1:0_0.tl1’ is located in:
‘twb_workspace’ > ‘libraries’ > ‘LAB1’ > ‘sessions’ > ‘pMOS’ > ‘pmos1:0_0.tl1’
4.4.3
‘Apply’ and ‘close’ the Cross-Sections Editor when done
4.4.4
Go to ‘Driver’ tap in Experiment window, double click the ‘ts4’ driver to specify which
mask file to be used (refer Figure 1.11). Add in the command and parameter as
follow,
Command: mask
Parameter: in.file=pmos1:0_0.tl1
4.4.5
‘OK’ to close the ‘Driver’ window
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Figure 1.11: The ts4 driver window
4.5 PROCESS DEFINITION
4.5.1. To specify the process name, double click on the icon ‘undef’ in TWB Experiment, in
the prompt out window, name the process as ‘pMOS’ and select ‘Do Not Load From Root
Wafer’.
Figure 1.12: Process name
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4.6 ICON CUSTOMIZATION
4.6.1 To do icon customization, click on the icon, this will invoke ‘Module Icon Chooser’. In
Module Icon Chooser, choose an appropriate icon to be used or draw a new icon. Add it into
User Pallete, by clicking ‘Add Standard’ button, now the icon is ready to be used. Finally
‘set and close’ the icon chooser window. Refer Figure 1.13 below.
Figure 1.13: Module Icon Chooser
4.7 PROCESS RECIPE DEVELOPMENT
4.7.1 Click on the ‘BreakUp’ button under the Process Recipe part (see Figure 1.14) to
create/edit process recipe.
4.7.2 To create a module in the Process Recipe, follow the instructions below;
i.
ii.
iii.
iv.
In ‘Process Recipe’ window, click on right mouse button,
Select ‘New Module’.
A new module with name ‘undef’ will appear in ‘Process Recipe’
window,
Place it after ‘pMOS’ module, this will be the
first process module
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Figure 1.14: Creating a New Module under the Process Recipe
4.7.3
Double click the new ‘undef’ module to edit its properties. A module window will
appear, as shown in Figure 1.15.
4.7.4
Click on the ‘icon’ to customize the icon. Refer to icon customization in 4.6 above.
4.7.5
A process simulator driver is needed to run process simulation. To get a simulator
driver (see Figure 1.16):
In ‘Experiment Window’, go to ‘Driver’ tap, select ‘ts4’ (TSuprem4 Process
Simulator Driver) then drags and drops it into ‘Driver’ column of ‘Module
Window’ using middle mouse button.
4.7.6
Change the module name from ‘undef’ to ‘Init’.
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Figure 1.15: An ‘undef’ module window
Figure 1.16: How to get a simulator driver for a Module
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4.7.7
To enter a command, Choose ‘Command’ > ‘New’ > ‘Append’ from Module
Window menu bar. A blank command cell will appears in command window. Click
on then blank cell and edit the name as ‘Init’. Then click apply or press enter to
apply the changes. See Figure 1.17.
4.7.8
To enter a new command after the existing command, select the existing command
and right click choose ‘New Command’ > ‘Append’. To enter a new command
above the existing command, select the existing command and right click choose
‘New Command’ > ‘Prepend’. This step also apply when you want to insert a new
parameter.
Figure 1.17: Incorporation of Command in a Module
4.7.9
Insert a parameter to ‘Init’ command by selecting ‘Init’ (Refer Figure 1.18), from
Module Window menu bar and choose ‘Parameter’ > ‘New’ > ‘Append’. Refer to
Figure 1.19. A blank parameter cell will appear in command window. Click on the
blank cell and edit the parameter as ‘arsenic=1e+15’. Then click apply or press
enter to apply the changes.
4.7.10 Add another parameter to the ‘init’ command. Repeat step 4.7.9, change the
parameter value to ‘width=5’ as given in the table below.
MODULE
Init
COMMAND
Init
18
PARAMETERS
Arsenic=1e+15
Width=5
EMT 471/3 – Semiconductor Physics
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Figure 1.18: Selecting ‘Init’ Command
Figure 1.19: Incorporating a parameter
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4.7.11 A complete Module with Command and Parameters are shown in the figure below.
Figure 1.20: Command and Parameters in Module
4.7.12 Continue to type the following details (in the following table) of the Commands and
Parameters into the Module. To create or edit New Module, always select
‘Breakup’ button. Repeat step 4.7.1 to 4.7.11.
MODULE
COMMAND
init
init
locos
Deposit
PARAMETERS
arsenic=1e+15
width=5
oxide
thickness=0.05
Deposit
nitride
thickness=0.05
Deposit
photo
thickness=0.5
Expose
mask=source
Develop
Implant
arsenic
dose=1e+15
energy=40
etch
nitride
diffuse
time=45
temp=1000
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wet
etch
photo
all
etch
nitride
all
deposit
photo
negative
thickness=0.5
expose
mask=source
develop
gate_formation
implant
arsenic
dose=1e+12
energy=40
etch
photo
all
Deposit
Poly
thickness=0.25
Deposit
photo
positive
thickness=0.5
Expose
mask=poly
Develop
active_formation
Etch
poly
Etch
photo
all
Deposit
Photo
Negative
thickness=0.5
Expose
mask=active
Develop
implantation
Etch
oxide
Etch
photo
all
Boron
dose=5e+15
energy=30
Implant
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Laboratory Module
Deposit
Oxide
thickness=0.05
Implant
boron
dose=5e+15
energy=40
Deposit
photo
negative
thickness=1
Expose
mask=contact
Develop
Etch
oxide
thickness=1
Etch
photo
all
Deposit
aluminum
thickness=0.25
Deposit
photo
positive
thickness=1
Expose
mask=metal
Develop
reflect_bottom_definition
Etch
aluminum
Etch
photo
all
Structure
Reflect
Left
Structure
Truncate
bottom y=4
4.7.13 If you are uncertain which command to be use, go to ‘CommandBuilder’ in the
Module window (see Figure 1.21). Select ‘Load’ and choose the library according
to the driver you are using. In this tutorial you can choose ‘TSUPREM4’.
4.7.14 You can copy and paste the command and its parameters into the TWB Module
window.
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Figure 1.21: Command Builder
4.8 RUN THE PMOS PROCESS SIMULATION
4.8.1 Click ‘Run’ button to start the simulation as shown in Figure 1.22 below.
Figure 1.22: Run the PMOS process simulation
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4.8.2 Observe the changes of the icon during the running process. The process simulation is
complete when all the wafers turn green. This indicates no error in the Process Recipe.
Simulation done with no error
Simulation fail, double click to see error message
Simulation is running
No action
4.9 HOW TO OBSERVE RESULTS USING TAURUS VISUAL
4.9.1
Make sure all the modules complete the simulation with
symbol.
4.9.2
In TWB ‘Workspace’, invoke ‘nmos experiment’ from standard library.
4.9.3
Go to ‘Toolkit’ tap, select ‘tv device structure’, use middle mouse button, drag
and drop it into ‘Toolkit’ tap in ‘pMOS experiment’ window (shown in Figure 1.23).
Figure 1.23: Incorporating ‘tv device structure’ in the ‘toolkit’ tap
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4.9.4
Laboratory Module
To view the wafer structure of pMOS, use the middle mouse button to select and
drag any wafer and drop it into ‘tv device structure box’ in the Toolkit library. A
Taurus Visual window will appear and show the selected wafer structure (as
shown in Figure 1.24). You can evaluate the result.
Figure 1.24: 2D plot of the pMOS structure
4.9.5
You can also use a 2D structure or cut plane plot
to create a 1D cutline plot
as shown in Figure 1.25 below. You can evaluate the result.
Figure 1.25: 1-D cut-line plot in Taurus Visual
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Finally, you can save all your work and exit.
5. RESULTS
5.1 Cut-line at the pMOS structure and get the 1-D plot of:
i.
ii.
iii.
iv.
Active boron
Active arsenic
Net doping
Total doping
5.2 To Capture the result and save it as jpeg format:
i.
ii.
iii.
iv.
v.
vi.
Use a graphic capture program called “gimp”
Go to terminal, type-in “gimp”
Then gimp program will be launched
Use the capture screen option to capture the window/terminal/picture that you want
Save it as jpeg format in the floppy A
Then use the jpeg file in your words/excel program
5.3 The saved results need to be included and discussed in your Basic Lab Report.
6. DISCUSSION
6.1 Write the discussions of the results in the Basic Lab Report.
7. CONCLUSION:
7.1 Conclude the lab work that has been done in Basic Lab 1 and the results obtained. Write
in Basic Lab Report.
8. REFERENCES
i.
ii.
iii.
iv.
v.
Taurus TSUPREM4 – User Guide (Sept. 2004). Version W-2004.09.
Taurus Modeling Environment: Taurus Workbench – User Guide (Dec. 2004).
Version W-2004.12
Taurus Modeling Environment: Taurus Visual – User Guide (Dec. 2004). Version W2004.12
Taurus Layout – Tutorial (June 2004). Version V-2004.06
S.m. Sze (2002). Semiconductor Devices: Physics and Technology, John Wiley &
Sons.
 The Basic Lab 1 Report Format will be given in page 60.
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BASIC LAB 2
INTRODUCTION TO DEVICE SIMULATION USING MEDICI & TWB
1. OBJECTIVE:
1.1
1.2
1.3
1.4
To introduce semiconductor physics with TCAD software.
To familiarize students with Taurus WorkBench (TWB).
To introduce students to Diode Device Simulation using TWB, and MEDICI.
To understand the transient simulation of a PN Diode.
2. INTRODUCTION
Medici is a powerful device simulation program that can be used to simulate the behavior of
MOS and bipolar transistors and other semiconductor devices. Medici models the twodimensional (2D) distributions of potential and carrier concentrations in a device. The
program can be used to predict electrical characteristics for arbitrary bias conditions.
Interactive device simulation can be done in TWB by using Medici driver.
This lab will introduce the following two capabilities of the MEDICI program:
i.
ii.
A transient simulation of a PN diode.
The simulation uses the following files and structure:
a) The input file mdex3 develops the simulation structure and simulates the transient
turn-on characteristics for the diode.
b) The input file mdex3h plots the hole concentration through the device at various
times during the turn-on.
c) The input mdex3e plots electron concentrations through the device at various times
during the turn-on.
3. COMPONENTS AND EQUIPMENTS
i.
ii.
Synopsys Taurus TCAD software
High-end PC
4. PROCEDURE
4.1 INPUT FILE OF A PN DIODE SIMULATION
The input file mdex3 creates the simulation structure for the PN-diode device and then
simulates the transient turn-on characteristics. The output associated with the execution of
MEDICI for the input file mdex3 is shown in File 2.1.
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4.2 MESH GENERATION
4.2.1 The first step in creating the device structure is to generate an initial done in lines 3
through 5 of the input file shown in File 2.1.
1... TITLE
Synopsys MEDICI Example 3 - PN Diode Transient
... +
Simulation
2... COMMENT
Create an initial simulation mesh
3... MESH
^DIAG.FLI
4... X.MESH
X.MAX=3.0 H1=0.50
5... Y.MESH
Y.MAX=3.0 H1=0.25
6... COMMENT
Region and electrode statements
7... REGION
NAME=Silicon SILICON
8... ELECTR
NAME=Anode TOP X.MAX=1.0
9... ELECTR
NAME=Cathode BOTTOM
10... COMMENT Specify impurity profiles
11... PROFILE N-TYPE N.PEAK=1E15 UNIF
OUT.FILE=MDEX3DS
12... PROFILE P-TYPE N.PEAK=1E19 X.MIN=0 WIDTH=1.0 X.CHAR=.2
... +
Y.MIN=0 Y.JUNC=.5
13... COMMENT Refine the mesh with doping regrids
14... REGRID
DOPING LOG RAT=3 SMOOTH=1 IN.FILE=MDEX3DS
15... REGRID
DOPING LOG RAT=3 SMOOTH=1 IN.FILE=MDEX3DS
16... REGRID
DOPING LOG RAT=3 SMOOTH=1 IN.FILE=MDEX3DS
... +
OUT.FILE=MDEX3MS
17... PLOT.2D GRID TITLE=”Example 3 - Simulation Mesh” SCALE FILL
18... COMMENT Attach a lumped resistance to the Anode contact
19... CONTACT NAME=Anode RESIST=1E5
20... COMMENT Specify physical models to use
21... MODELS
SRH AUGER CONMOB FLDMOB
22... COMMENT Symbolic factorization
23... SYMB
NEWTON CARRIERS=2
24... COMMENT Create a log file for the transient I-V data
25... LOG
OUT.FILE=MDEX3I
26... COMMENT Perform a 0-volt steady state solution, then simulate
27... $
the transient turn-on characteristics for the diode.
28... SOLVE
OUT.FILE=MDE3S00
29... SOLVE
V(Anode)=2 TSTEP=1E-12 TSTOP=10E-9 OUT.FILE=MDE3S01
30... COMMENT Plot the diode current and contact voltage vs. time
31... PLOT.1D X.AXIS=TIME Y.AXIS=I(Anode)
... +
POINTS TOP=2E-5 RIGHT=.5E-9
... +
TITLE=”Example 3 - Current vs. Time” COLOR=2
32... PLOT.1D X.AXIS=TIME Y.AXIS=V(Anode)
... +
POINTS TOP=1.1 RIGHT=.5E-9
... +
TITLE=”Example 3 - Contact Voltage vs. Time” COLOR=2
File 2.1: Output of the simulation input file mdex3
To understand more about the command, please refer to CommandBuilder.
4.2.2 The MESH statement initiates the mesh generation. The X.MESH and Y.MESH
statements are used to define the placement of lines of nodes within the structure. The
structure created by the X.MESH and Y.MESH statements extends from 0 to 3 microns in
both the x and y directions. The grid spacing in each direction is uniform.
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4.2.3 With initial mesh defined, it is now the time to define the device. The entire device is
defined as silicon with the REGION statement in line 7.
4.2.4 The ELECTR statements locate the contacts within the device structure.
i.
ii.
The anode is placed along the left edge of the top surface and makes contact with
what will eventually be the p-type material of the diode.
The cathode is placed along the bottom surface and makes contact with what will
eventually be the n-type material of the diode.
4.2.5 Two PROFILE statements define the impurity distribution for the structure.
i.
ii.
The first PROFILE statement places a uniform concentration of n-type material over
the entire device.
The second PROFILE statement then adds a Gaussian distribution of p-type material
to the top-left portion of the structure to form the diode.
4.2.6 The profile information is saved in a file to be used during grid refinement by specifying
the OUT.FILE parameter on the first PROFILE statement.
4.3 DOPING REGRID
4.3.1 It is now necessary to refine the grid so it is adequate for simulation. In lines 14
through 16, the simulation grid is refined based on DOPING. If the impurity concentration
varies by more than three orders of magnitude over a triangle of the existing mesh, the
triangle is divided into four congruent triangles by adding new nodes.
4.3.2 Each REGRID statement creates one new level of triangles. The impurity
concentration at the new nodes of each refined mesh is calculated using the profile
information stored in the file specified by IN.FILE. Performing the regrids one level at a time
and using the doping file specified by IN.FILE avoids problems that may arise due to
interpolation errors.
4.3.3 The final refined mesh is shown in Figure 2.1 below,
Figure 2.1: Simulation mesh from PLOT.2D at line 17 in file mdex3 (File 2.1)
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4.4 TRANSIENT ANALYSIS
4.4.1 Models and Boundary Conditions
Before generating solutions, any special boundary conditions or physical models
to be used should be specified. For this example:
i.
A lumped resistance of is attached to the anode.
ii.
Specify that both Shockley-Read-Hall and Auger recombination are to be used.
iii.
Specify concentration and field-dependent mobilities.
4.4.2 Solution Methods
Since the behavior of both electrons and holes will be important in this Basic Lab 2, a twocarrier simulation is requested on the SYMB statement at line 23. Newton’s method is also
selected as the most efficient solution technique. Before actually performing the first solution,
a log file is specified that will store the terminal I-V data at each bias and/or time point of the
simulation.
4.4.3 Initial Solution
Since no bias values are specified on the first SOLVE statement (line 28), all biases default
to zero. The results of this solution point are stored for future processing or plotting in the file
specified by OUT.FILE.
4.4.4 Transient Solutions
The second SOLVE statement (line 29) begins the transient analysis of the turn-on
characteristics for the diode. The bias applied to the anode is instantaneously switched to 2
volts at time t=0.
To perform a transient analysis with Medici, it is only necessary to specify the first time step
to use and the stopping time. Medici will automatically choose the intermediate
time steps to insure an accurate solution. In this lab, a 1 picosecond initial time step is
chosen with the TSTEP parameter, and a stopping time of 10 nanoseconds is chosen with
the TSTOP parameter (line 29). Specifying the OUT.FILE parameter (line 29) causes the
solution information to be stored in files for future processing or plotting. The solution for
each time step will be stored in a separate file, with the identifier specified by OUT.FILE
being incremented for each solution.
4.4.5 Graphical Results
Line 31 requests that a plot of diode current versus time be drawn. This is shown in Figure
2.2. Note the variation in time step size selected automatically by Medici during the analysis.
It should also be noted that although the analysis above was carried out to 10 ns, the plot
shown in Figure 2.2 was limited to the first 0.5 ns.
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Figure 2.2: Current vs. time from PLOT.1D at line 31 in file mdex3 (File 2.1)
Line 32 requests that a plot of the anode voltage versus time be drawn. This is shown in
Figure 2.3. Although the applied bias remained at 2 volts during the entire analysis, the
actual contact voltage is always less than 2 volts and varies with time. This is due to the
lumped resistance attached between the applied bias and the anode.
Figure 2.3: Contact voltage from PLOT.1D at line 32 in file mdex3 (File 2.1)
4.5 LAB EXERCISE ON SIMULATION OF A DIODE
4.5.1 Invoke TWB (TAURUS WORKBENCH).
i. Create new project and new experiment.
ii. Name the new project as LAB2 and the new experiment as DIODE.
4.5.2
Open the DIODE experiment. Create a new module. Name the module as
DIODE_MESHING.
Tips: Refer to Basic Lab1, if you have problem with step 4.5.1 and 4.5.2
4.5.3
In the DIODE_MESHING module, select an icon and load the MEDICI driver.
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i. Open standard Library
from TWB workspace,
ii. In Tools tap, copy and paste layout icon into “Lab2” Library, Tools tap.
iii. Repeat the step, copy all the driver icons from SimulatorDrivers tap into
“Lab2”Library, SimulatorDrivers tap.
iv. From SimulatorDrivers tap, drag and drop the medici driver to Driver column of
Module “DIODE_MESHING”.
4.5.4
Go to the menu bar and select FILE > LOAD FROM COMMAND INPUT FILE. Load
the input file mdex3.inp (this file contain of the commands in File 2.1) from the
lab_file directory.
4.5.5
Run the module. Observe the graphs. Write down your observation.
4.5.6
You can also plot the result using TV (Taurus-Visual).
i.
ii.
Open Experiment “nmos” from standard library,
Go to Toolkit tap, copy and paste “tv_device_structure” icon to Experiment
“DIODE” Toolkit tap.
4.5.7
Drag and drop “DIODE_MESHING” wafer into “tv_device_structure”.
4.5.8
From Taurus-Visual, sketch the relative NetDoping profile diagram.
4.5.9
Do a cutline, to plot the NetDoping concentration graph.
4.6 ONE-DIMENSIONAL PLOTS OF HOLE CONCENTRATIONS
4.6.1 The device structure that was created and saved by the input file mdex3 is read by the
input file mdex3h. Additionally, solution files created by the input file mdex3 at various
simulation times are read by the input file mdex3h and are used to plot the hole
concentration along a one-dimensional vertical slice through the structure at those times.
4.6.2 File 2.2 and Figure 2.4 contain the output associated with the execution of Medici
input file mdex3h.
4.6.3 In File 2.2, the UNCH parameter is used on the second and subsequent PLOT.1D
statements to allow all the curves to be plotted in the same figure with the scaling
established by the first PLOT.1D statement.
4.6.4 In Figure 2.4, the input file mdex3h adds labels to the figure to identify each curve
with the corresponding simulation time. The simulation times were obtained from the printed
output associated with the execution of mdex3.
1...
...
2...
3...
TITLE
+
COMMENT
COMMENT
Synopsys MEDICI Example 3H - PN Diode Transient
Simulation
Plot hole concentration at various times
Read in simulation structure
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4... MESH
5... TITLE
6... LOAD
7... PLOT.1D
8... LOAD
9... PLOT.1D
10... LOAD
11... PLOT.1D
12... LOAD
13... PLOT.1D
14... LOAD
15... PLOT.1D
16... LOAD
17... PLOT.1D
18... LOAD
19... PLOT.1D
20... LABEL
21... LABEL
22... LABEL
23... LABEL
24... LABEL
25... LABEL
26... LABEL
Laboratory Module
IN.FILE=MDEX3MS
Example 3H - Hole Concentration
IN.FILE=MDE3S00
HOLES Y.LOG X.ST=0. X.EN=0. Y.ST=0. Y.EN=3.
IN.FILE=MDE3S05
HOLES Y.LOG X.ST=0. X.EN=0. Y.ST=0. Y.EN=3.
IN.FILE=MDE3S07
HOLES Y.LOG X.ST=0. X.EN=0. Y.ST=0. Y.EN=3.
IN.FILE=MDE3S10
HOLES Y.LOG X.ST=0. X.EN=0. Y.ST=0. Y.EN=3.
IN.FILE=MDE3S15
HOLES Y.LOG X.ST=0. X.EN=0. Y.ST=0. Y.EN=3.
IN.FILE=MDE3S19
HOLES Y.LOG X.ST=0. X.EN=0. Y.ST=0. Y.EN=3.
IN.FILE=MDE3S28
HOLES Y.LOG X.ST=0. X.EN=0. Y.ST=0. Y.EN=3.
LABEL=”0”
X=1.10
Y=5.0E6
LABEL=”7”
X=1.3
Y=2.5E7
LABEL=”10”
X=1.5
Y=5.0E7
LABEL=”17”
X=1.80
Y=8.5E8
LABEL=”44”
X=2.10
Y=1.0E12
LABEL=”135”
X=2.13
Y=2.0E14
LABEL=”10000 psec” X=2.10
Y=1.5E16
UNCH
UNCH
UNCH
UNCH
UNCH
UNCH
File 2.2: Output of the simulation input file mdex3h
Figure 2.4: Hole concentration from PLOT.1D at lines 7, 9, 11, 13, 15, 17, and 19, and LABEL at
lines 20 through 26 in file mdex3h (File 2.2)
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4.7 LAB EXERCISE ON HOLE CONCENTRATION SIMULATION
4.7.1 Create new module under the same experiment. Name the module as HOLE
CONCENTRATION.
4.7.2 Open the module. Load an icon and MEDICI driver.
4.7.3 Load the input file mdex3h.inp (as shown if File 2.2) from lab_file directory.
4.7.4 Run the module. Observe the graphs. Write down your observation.
4.8 ONE-DIMENSIONAL PLOTS OF ELECTRON CONCENTRATION
The device structure that was created and saved by the input file mdex3 is read by
the input file mdex3e. Additionally, solution files created by the input file mdex3 at
various simulation times are read by the input file mdex3e and are used to plot the
electron concentration along a one-dimensional vertical slice through the structure
at those times.
File 2.3 and Figure 2.5 contain the output associated with the execution of Medici for
the input file mdex3e.
In File 2.3, the UNCH parameter is used on the second and subsequent PLOT.1D
statements to allow all the curves to be plotted in the same figure with the scaling
established by the first PLOT.1D statement.
In Figure 2.5, the input file mdex3e also adds labels to the figure to identify each curve with
the corresponding simulation time. The simulation times were obtained from the printed
output associated with the execution of mdex3.
1... TITLE
... +
2... COMMENT
3... COMMENT
4... MESH
5... TITLE
6... LOAD
7... PLOT.1D
... +
8... LOAD
9... PLOT.1D
10... LOAD
11... PLOT.1D
12... LOAD
13... PLOT.1D
14... LOAD
15... PLOT.1D
16... LOAD
17... PLOT.1D
18... LOAD
Synopsys MEDICI Example 3E - PN Diode Transient
Simulation
Plot electron concentration at various times
Read in simulation structure
IN.FILE=MDEX3MS
Example 3E - Electron Concentration
IN.FILE=MDE3S00
ELECT Y.LOG X.ST=0. X.EN=0. Y.ST=0. Y.EN=3.
TOP=1E18
IN.FILE=MDE3S05
ELECT Y.LOG X.ST=0. X.EN=0. Y.ST=0. Y.EN=3. UNCH
IN.FILE=MDE3S07
ELECT Y.LOG X.ST=0. X.EN=0. Y.ST=0. Y.EN=3. UNCH
IN.FILE=MDE3S10
ELECT Y.LOG X.ST=0. X.EN=0. Y.ST=0. Y.EN=3. UNCH
IN.FILE=MDE3S15
ELECT Y.LOG X.ST=0. X.EN=0. Y.ST=0. Y.EN=3. UNCH
IN.FILE=MDE3S19
ELECT Y.LOG X.ST=0. X.EN=0. Y.ST=0. Y.EN=3. UNCH
IN.FILE=MDE3S28
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19... PLOT.1D
ELECT Y.LOG X.ST=0. X.EN=0. Y.ST=0. Y.EN=3. UNCH
20...
21...
22...
23...
24...
25...
26...
LABEL=”0”
LABEL=”7”
LABEL=”10”
LABEL=”17”
LABEL=”44”
LABEL=”135”
LABEL=”10000 psec”
LABEL
LABEL
LABEL
LABEL
LABEL
LABEL
LABEL
X=0.77
X=0.65
X=0.60
X=0.57
X=0.57
X=0.65
X=0.75
Y=1.2E11
Y=8E11
Y=1E13
Y=2E14
Y=1.7E15
Y=6E15
Y=4E16
File 2.3: Output of the simulation input file mdex3e
Figure 2.5: Electron concentration from PLOT.1D at lines 7, 9, 11, 13, 15, 17, and 19, and LABEL at
lines 20 through 26 in file mdex3e (File 2.3)
4.9 LAB EXERCISE ON ELECTRON CONCENTRATION SIMULATION
4.9.1
Create new module under the same experiment. Name the module as ELECTRON
CONCENTRATION.
4.9.2
Open the module. Load an icon and MEDICI driver.
4.9.3
Load the mdex3e.inp (as shown in File 2.3 ) from lab_file directory.
4.9.4
Start the simulation. Observe the graphs. Write down your observation.
4.10 ENERGY BANDS IN TAURUS-VISUAL
4.10.1 Drag and drop “DIODE_MESHING” or “ELECTRON_CONCENTRATION” wafer
into “tv_device_structure”.
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4.10.2 From Taurus-Visual, do a cutline vertically at the structure. Select Conduct Band,
Vacuum Level and Valence Band from the list of fields.
Tips: use ctrl key to select more than one item in the list.
4.10.3 Sketch the Valence Band, Conduct Band and the Vacuum Level profile diagram.
Write down your observation.
5. RESULTS
5.1 Capture and save all the results from :
i.
ii.
iii.
Lab Exercise on Simulation of a Diode (4.5)
Lab Exercise on Hole Concentration Simulation (4.7)
Lab Exercise on Electron Concentration Simulation (4.9)
(refer Basic Lab 1 on how to capture and save figure in jpeg format)
5.3 The saved results need to be included and discussed in your Basic Lab Report.
6. DISCUSSION
6.1 Write the discussions based on the results in the Basic Lab Report.
7. CONCLUSION:
7.1 Conclude the lab work that has been done in Basic Lab 2 and the results obtained. Write
in Basic Lab Report.
8. REFERENCES
i.
ii.
iii.
iv.
v.
Taurus MEDICI-MEDICI– User Guide (Sept. 2004). Version W-2004.09.
Taurus MEDICI-Taurus Device-User Guide (Sept. 2004). Version W-2004.09.
Taurus Modeling Environment: Taurus Workbench – User Guide (Dec. 2004).
Version W-2004.12
Taurus Modeling Environment: Taurus Visual – User Guide (Dec. 2004). Version W2004.12
S.m. Sze (2002). Semiconductor Devices: Physics and Technology, John Wiley &
Sons.
 The Basic Lab 2 Report Format will be given in page 61
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BASIC LAB 3
SIMULATION ON HETEROJUNCTION DEVICES: SiGe HBT & HEMT
1. OBJECTIVE:
1.5
1.6
1.7
1.8
To introduce semiconductor physics with TCAD software.
To familiarize students with Taurus WorkBench (TWB).
To introduce students to Device Simulation using TWB, and MEDICI.
To understand the simulation of a SiGe HBT and HEMT.
2. INTRODUCTION
The Medici Heterojunction Device AAM (HD-AAM) can be used to model a wide variety of
semiconductor devices which employ heterojunctions. This lab provides examples of
analyses of the following cases:

A 1-D SiGe Heterojunction Bipolar Transistor (HBT). The base region of this
structure consists of Si0.8Ge0.2 with mole fraction transitions occurring in the emitterbase and base-collector regions. The forward bias characteristics of this HBT are
simulated.

A High Electron Mobility Transistor (HEMT) that employs three different materials
(GaAs, AlGaAs, and InGaAs). Gate characteristics for the device are calculated, and
band diagrams and current flowlines are plotted.
3. COMPONENTS AND EQUIPMENTS
i.
ii.
Synopsys Taurus TCAD software
High-end PC
4. PROCEDURE
4.1 SiGe HETEROJUNCTION BIPOLAR TRANSISTOR
A Heterojunction Bipolar Transistor (HBT) is formed by introducing a heterojunction at the
emitter-base junction of a bipolar device. Such devices are extremely attractive due to their
potential for high speed operation. HBTs typically have an emitter with a bandgap that is
wider than the bandgap in the base. The potential barrier formed at the emitter-base junction
under these conditions reduces the minority carrier injection from the base into the emitter to
an insignificant level. This results in improved emitter efficiency and higher current gain, and
leaves the base doping free as a parameter that can be adjusted for optimizing the
performance of these devices. In this example, the forward characteristics of a onedimensional npn Si1-xGex HBT are simulated. This structure uses silicon for the emitter and
collector regions, and the alloy Si1-xGex for the base region. Si1-xGex has a narrower
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bandgap than silicon with most of the offset occurring at the valence band. Thus, hole
injection into the emitter is drastically reduced for this device, resulting in a very high current
gain. In this example, a Ge mole fraction of x=0.2 is used.
4.1.1 Device Structure and Plots
The structure for this simulation is generated using the input file mdex16 shown in File 3.1
and 3.2. The three REGION statements that have the SIGE parameter specified are used to
define the Si0.8Ge0.2 section of the device. The first and third such statements are used to
specify graded transitions in the emitterbase and base-collector regions. The mesh and
structure for the device are shown in Figure 3.1. The specified doping and mole fraction are
shown in Figure 3.2. This input file also performs an initial zero bias solution and then plots
the equilibrium band diagram. This is shown in Figure 3.3.
1... TITLE
2... COMMENT
Synopsys MEDICI - 1D SiGe HBT Simulation
Specify a ”1D” Mesh Structure
3... MESH
4... X.MESH
5... Y.MESH
6... Y.MESH
7... Y.MESH
OUT.FILE=MDEX16M
WIDTH=0.50
N.SPACES=1
DEPTH=0.1
H2=0.005
DEPTH=0.1
H1=0.005
DEPTH=0.6
H1=0.005
8... COMMENT
... +
9... REGION
10... REGION
11... REGION
12... REGION
Use a SiGe base (X.MOLE=0.2) with a graded mole fraction
for the emitter-base and base-collector transitions.
SILICON
SIGE
Y.MIN=0.100
Y.MAX=0.125
X.MOLE=0.0
SIGE
Y.MIN=0.125
Y.MAX=0.200
X.MOLE=0.2
SIGE
Y.MIN=0.200
Y.MAX=0.230
X.MOLE=0.2
13... COMMENT
14... ELECTR
15... ELECTR
16... ELECTR
17... PROFILE
18... PROFILE
19... PROFILE
20... PROFILE
Electrodes: Use a majority carrier contact for the base.
NAME=Emitter
TOP
NAME=Base
Y.MIN=0.125
Y.MAX=0.125
MAJORITY
NAME=Collector BOTTOM
N-TYPE N.PEAK=2E16
UNIFORM
N-TYPE N.PEAK=5E19
Y.MIN=0.80
Y.CHAR=0.125
P-TYPE N.PEAK=2E18
Y.MIN=0.12
Y.JUNC=0.200
N-TYPE N.PEAK=7E19
Y.JUNC=0.10
21... PLOT.2D
22... FILL
23... PLOT.2D
... +
24... LABEL
25... LABEL
26... LABEL
27... PLOT.1D
... +
28... LABEL
29... LABEL
30... LABEL
31... PLOT.1D
... +
32... LABEL
... +
GRID
FILL
SCALE TITLE=”SiGe HBT Mesh”
SET.COLOR
C.SIGE=5
C.SILI=3
^NP.COLOR
BOUND FILL
SCALE JUNC
L.JUNC=1
^CLEAR
X.OFF=11.5
TITLE=”SiGe HBT Structure”
LABEL=”n-emitter”
X=0.17 Y=0.05
LABEL=”SiGe p-base”
X=0.17 Y=0.18
LABEL=”n-collector”
X=0.17 Y=0.50
DOPING
LOG
X.ST=0 X.EN=0 Y.ST=0 Y.EN=0.8
COLOR=2
TITLE=”Doping Through Emitter”
LABEL=”n”
X=0.05 Y=1E16
LABEL=”p”
X=0.15 Y=1E16
LABEL=”n”
X=0.50 Y=1E16
X.MOLE
X.ST=0 X.EN=0 Y.ST=0 Y.EN=0.8 COLOR=4 LINE=2
^CLEAR ^AXES ^MARKS
^LABELS
LABEL=”mole fraction (max=0.2)”
X=0.3 Y=0.18 START.LE
LX.FIN=0.22
ARROW
C.SI=0.2
RATIO=1.2
H2=0.050
X.END=0.2
X.END=0.0
File 3.1: First part of the simulation input file mdex16
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33... COMMENT
... +
34... SYMBOL
35... SOLVE
36... PLOT.1D
... +
37... PLOT.1D
38... PLOT.1D
39... PLOT.1D
40... LABEL
41... LABEL
42... LABEL
43... LABEL
Laboratory Module
Perform a 0-bias solution and plot the equilibrium
band diagram.
CARR=2
NEWTON
VAL
NEG
X.ST=0 X.EN=0 Y.ST=0 Y.EN=0.8 MIN=-1.2 MAX=1.2
TITLE=”HBT Band Diagram, Vce=0.0, Vbe=0.0”
CON
NEG
X.ST=0 X.EN=0 Y.ST=0 Y.EN=0.8
UNCH
POT
NEG
X.ST=0 X.EN=0 Y.ST=0 Y.EN=0.8
UNCH
QFP
NEG
X.ST=0 X.EN=0 Y.ST=0 Y.EN=0.8 UNCH COL=2 LINE=2
LABEL=”conduction”
X=0.40 Y=0.25
LABEL=”potential”
X=0.40 Y=-0.3
LABEL=”valence” X=0.40 Y=-0.85
LABEL=”Fermi level”
X=0.26 Y=0.05
File 3.2: Second part of the simulation input file mdex16
Figure 3.1: Mesh and structure generated by lines 21 through 26 in file mdex16
Figure 3.2: Doping and mole fraction generated by lines 27 through 32 in file mdex16
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Figure 3.3: Equilbrium band generated by lines 36 through 43 in file mdex16
4.1.2 Lab Exercise (Device Structure and Plots)
i.
Invoke TWB (TAURUS WORKBENCH).
Create new project and new experiment.
Name the new project as LAB3 and the new experiment as SIGE.
ii. Open the SIGE experiment. Create a new module. Name the module as
SIGE_STRUCTURE.
Tips: Refer to Lab1, if you have problem with step i and ii
iii. In the SIGE_STRUCTURE module, select an icon and load the MEDICI driver.
Tips: Open standard Library
from TWB workspace,
In Tools tap, copy and paste layout icon into “Lab4” Library, Tools tap.
Repeat the step, copy all the driver icons from SimulatorDrivers tap into
“Lab4”Library, SimulatorDrivers tap.
From SimulatorDrivers tap, drag and drop the medici driver to Driver column
of Module “SIGE_STRUCTURE”.
iv. Go to the menu bar and select FILE > LOAD FROM COMMAND INPUT FILE.
Load the input file mdex16.inp from the lab_file directory
v. Run the module. Observe the graphs. Write down your observation.
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4.1.3 Forward Bias Simulation
The input file mdex16f, shown in File 3.3 is used to read in the HBT structure that was
created with the input file mdex16, and then simulates its forward bias characteristics. By
default, Medici uses an energy bandgap model for strained Si1-xGex as a function of mole
fraction x. A model for unstrained Si1-xGex can also be used by specifying a MATERIAL
statement with the parameters “SIGE EG.MODEL=3” prior to the SOLVE statement.
4.1.4 Plots
The output generated by this example includes a Gummel plot (Ic and Ib versus Vbe) and a
plot of current gain versus Ic. These plots are shown in Figures 3.4 and 3.5, respectively.
The current gain shown in Figure 3.5 is one to two orders of magnitude higher than it would
be for a device of the same dimensions and doping levels that uses a silicon base instead of
a Si1-xGex base.
1... TITLE
Synopsys MEDICI - 1D SiGe HBT Simulation
2...
3...
4...
5...
Read in mesh, specify contact and model parameters
IN.FILE=MDEX16M
NAME=Emitter
SURF.REC
VSURFN=1E5
VSURFP=1E5
CONMOB
FLDMOB
CONSRH
AUGER BGN
COMMENT
MESH
CONTACT
MODELS
6... COMMENT
7... SYMBOLIC
8... METHOD
9... LOG
10... SOLVE
... +
11... EXTRACT
Use Vc=2.0, ramp the base voltage
NEWTON
CARRIERS=2
CONT.STK
OUT.FILE=MDE16BI
V(Collector)=2.0
V(Base)=0.0
ELEC=Base VSTEP=0.05
NSTEPS=16
NAME=Beta EXPRESS=@I(Collector)/@I(Base)
12...
13...
...
...
14...
...
15...
16...
COMMENT
PLOT.1D
+
+
PLOT.1D
+
LABEL
LABEL
Plot Ic and Ib vs. Vbe
IN.FILE=MDE16BI X.AXIS=V(Base) Y.AXIS=I(Collector) LOG
LEFT=0
RIGHT=0.9
BOTTOM=1E-15 TOP=1E-3
POINTS
TITLE=”Example 16F - HBT Gummel Plot”
COLOR=2
IN.FILE=MDE16BI X.AXIS=V(Base) Y.AXIS=I(Base)
LOG
UNCH
COLOR=3
LINE=2
POINTS
LABEL=”Ic”
X=0.5 Y=7E-8
LABEL=”Ib”
X=0.5 Y=2E-11
17...
18...
...
...
...
COMMENT
PLOT.1D
+
+
+
Plot the current gain vs. collector current
IN.FILE=MDE16BI X.AXIS=I(Collector) Y.AXIS=Beta X.LOG
Y.LOG
LEFT=1E-10
RIGHT=1E-3
BOT=10 TOP=1E3 COLOR=2
TITLE=”Example 16F - HBT Gain vs. Collector Current”
POINTS
File 3.3: Output of the simulation input file mdex16f
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Laboratory Module
Figure 3.4: Gummel plot generated by lines 13 through 16 in file mdex16f (File 3.3)
Figure 3.5: Current gain generated by line 18 in file mdex16f (File 3.3)
4.1.5 Lab Exercise (Forward Bias Simulation)
i.
Create new module under the same experiment. Name the module as
FORWARD_BIAS.
ii.
Open the module. Load an icon and MEDICI driver.
iii.
Load the input file mdex16f.inp from the lab_file directory above.
iv.
Run the module. Observe the graphs. Write down your observation
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4.2 HIGH ELECTRON MOBILITY TRANSISTOR
The High Electron Mobility Transistor (HEMT) is a small geometry heterojunction device that
exploits the high electron mobility in an undoped region to achieve high speed operation.
Heterojunctions are used to create a narrow undoped electron well which forms the channel
for current flow. Electrons from surrounding doped regions of the device become trapped in
the well resulting in a high concentration of electrons in the channel. This channel is below
the surface of the device and separated from the impurity atoms (doping) which supply the
electrons for the conduction process. The lack of scattering sites in the channel results in
high electron mobility. In addition, the channel itself is normally constructed from a material
which possesses a high mobility such as InGaAs.
4.2.1 Structure Generation
The HEMT simulated is shown in Figure 3.6 and the input file mdex17 that generated the
simulation in File 3.4 and 3.5 (this device is loosely based upon a device described in the
article: “DC and Microwave Characteristics of Sub- 0.1-Length Planar-Doped
Pseudomorphic HEMT’s,” P.-C. Chao et al., IEEE Trans. Electron Devices, vol. 36, no. 3,
pp. 461-473, Mar. 1989).
4.2.2 Device Structure
The device structure is largely planar with constant doping in most of the regions. The
device regions and grid were generated using Synopsys TCAD’s Michelangelo. A refine box
was used in the channel of the device to create fine grid needed to resolve the channel. The
structure and mesh generated by Michelangelo is stored in the ASCII file mdex17.msh.
4.2.3 Doping
Lines 18-24 specify the doping for the device, as shown below:
i.
The bulk (region 1), AlGaAs spacer (region 10), and the InGaAs channel (region
2) are left undoped (although an insignificant doping concentration of 1e2/cm3 is
specified).
ii.
The source and drain contact regions (5 and 6) are heavily doped (n-type, 1e20).
iii.
The AlGaAs region under the gate serves as the source of channel electrons and
is doped n-type, 1e18.
iv.
At line 24 a 2D- (delta-) doping is used as an additional source of electrons.
v.
Line 25 sets the colors that are used to fill various material regions during
subsequent plotting.
1... TITLE
GaAs - AlGaAs - InGaAs HEMT Device
2... COMMENT Read in the mesh file (created by the Device Editor)
3... MESH
IN.FILE=mdex17.tif TIF
4... $
5... $
6... $
7... $
8... $
9... $
10... $
11... $
12... $
13... $
14... $
Region
Region
Region
Region
Region
Region
Region
Region
Region
Region
#1
#2
#3
#4 =
#5
#6
#7 =
#8 =
#9 =
#10
GaAs Body
InGaAs InGaAs channel
AlGaAs n AlGaAs(under gate)
Electrode #1 Electrode gate
GaAs source N+
GaAs drain N+
Electrode #2 Electrode source
Electrode #3 Electrode drain
Electrode #4 subst
AlGaAs AlGaAs Spacer
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15... $
16...
17...
18...
19...
20...
21...
22...
23...
24...
25...
$
COMMENT
PROFILE
PROFILE
PROFILE
PROFILE
PROFILE
PROFILE
INTERFACE
FILL
26...
27...
28...
29...
30...
31...
32...
$
MATERIAL
MATERIAL
MATERIAL
$
CONTACT
$
Specify Doping
REGION=1
N.TYPE
CONC=1E2
REGION=2
P.TYPE
CONC=1E2
REGION=3
N.TYPE
CONC=1E18
REGION=5
N.TYPE
CONC=2E20
REGION=6
N.TYPE
CONC=2E20
REGION=10
N.TYPE
CONC=1E2
REGION=(3,10)
QF=2e12
^NP.COL
SET.COL
C.GAAS=2
UNIF
UNIF
UNIF
UNIF
UNIF
UNIF
C.ALGAAS=3
REGION=(1,5,6) GAAS
REGION=2
INGAAS
X.MOLE=0.85
REGION=(3,10)
ALGAAS
X.MOLE=0.2
NAME=Gate
SCHOTTKY
WORK=5.17
File 3.4: The first part of simulation input file mdex17
4.2.4 Material and Mobility Parameters
Lines 27-29 assign the appropriate material types and mole fractions to the various regions.
Mole-fraction and material dependent models are used during the simulation for quantities
such as the band-gap, electron affinity, low- and high field mobility etc. (see the
Heterojunction Device AAM chapter in the first volume of the manual for more details). The
plot displayed in Figure 3.6 is generated by lines 34-41 of the input file (see File 3.5).
4.2.5 Simulation
This section describes the HEMT simulation and generated plots. Line 43 enables models
for concentration dependent recombination SRH recombination, Auger recombination, and
the analytic mobility model. For gate characteristics in this particular device, it is easiest to
start the simulation with the device ON and reduce the gate voltage until the device cuts off.
33...
34...
35...
36...
37...
38...
39...
40...
41...
42...
43...
44...
45...
46...
47...
48...
49...
50...
COMMENT
PLOT.2D
FILL
LABEL
LABEL
LABEL
LABEL
LABEL
LABEL
$
MODELS
$
COMMENT
SYMB
SOLVE
SYMB
SOLVE
$
Generate plot of device structure
BOUNDARY
FILL
REGION=2
COLOR=5
^NP.COL
LABEL=GaAs
x=.5
y=.1
LABEL=GaAs
x=.1
y=.01
LABEL=GaAs
x=.9
y=.01
LABEL=AlGaAs x=.5
y=.056
LABEL=InGaAs x=.5
y=.065
LABEL=AlGaAs x=.5
y=.037
CONSRH
AUGER
Initial solution
NEWT
CARR=0
V(Drain)=0.05
NEWT
CARR=2
ANALYTIC
V(Gate)=0.6
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51...
52...
...
53...
54...
55...
56...
57...
...
58...
59...
60...
61...
62...
63...
64...
...
65...
66...
67...
68...
69...
70...
71...
...
SOLVE
PLOT.1D
+
PLOT.1D
LABEL
LABEL
$
PLOT.1D
+
PLOT.1D
PLOT.1D
LABEL
LABEL
LABEL
$
PLOT.2D
+
FILL
CONTOUR
$
COMMENT
SOLVE
$
PLOT.1D
+
Laboratory Module
ELEC=Gate
VSTEP=-0.1
NSTEP=4
X.ST=0.5
X.END=0.5
Y.ST=-1 Y.EN=1 DOPING LOG
TITLE="MDEX17 Channel Doping & Electrons Device ON"
X.ST=0.5 X.END=0.5 Y.ST=-1 Y.EN=1 ELECT LOG UNCH COL=2
LABEL=Electrons
COL=2 X=1.08
Y=1e13
LABEL=Doping X=1.08
Y=1e5
X.ST=0.5 X.EN=0.5 Y.ST=-1 Y.EN=1 COND TOP=1 BOT=-2
NEG TITLE="MDEX17 Band structure Device ON"
X.ST=0.5 X.EN=0.5 Y.ST=-1 Y.EN=1 VAL UNCH NEG
X.ST=0.5 X.EN=0.5 Y.ST=-1 Y.EN=1 QFN UNCH NEG COL=2
LABEL=Cond
X=1.08
Y=0.5
LABEL=Qfn
X=1.08
Y=0.05
LABEL=Val
X=1.08
Y=-1.3
FILL
BOUND
TITLE="MDEX17 Current Flow, Device ON"
REGION=2
COLOR=5
^NP.COL
FLOW
Calculate the gate characteristics.
ELEC=Gate
VSTEP=-0.1
NSTEP=6
X.AX=V(Gate) Y.AX=I(Drain)
POINTS
TITLE="MDEX17 Gate Characterics of HEMT Device"
File 3.5: Second part of the simulation input file mdex17
Figure 3.6: HEMT device generated by lines 34 through line 41 in file mdex17
4.2.6 Solution
At lines 46 and 47, a zero carrier (Poisson only) solution is performed as an initial guess
with 0.05V on the drain and 0.6V on the gate. Then, a two carriers is performed (lines 54
and 55). Then, the gate voltage is reduced in -0.1V steps, stopping at Vg=0.2V, and some
plots are generated (line 57).
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4.2.7 Plots
The first plot (lines 52-55) is shown in Figure 3.7, and displays electron concentration and
doping as a function of depth at the center of the channel. The peak in doping due to the
Gaussian profile is plainly evident. It is also clear how the electrons have moved away from
the doped region and flowed into the undoped InGaAs well. Expect these electrons to have
very high mobility due to the absence of the ionized doping atoms which cause scattering
and reduce the mobility. Lines 57-62 generate a band diagram (Figure 3.8) by plotting the
following:
• Conduction band
• Valence band
• Electron quasi-Fermi level
Figure 3.7: Doping and electron concentration generated by lines 52 through 55 in file mdex17
Figure 3.8: Band structure generated by lines 57 through 62 in file mdex17
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4.2.8 NEGATIVE Parameter
Note the specification of the NEGATIVE parameter on the PLOT.1D statements. This is
necessary since band diagrams are calculated as the electron charge multiplied by the
potential and the electron charge is negative. The channel well in the conduction band is
clearly visible.
The quasi-Fermi level is flat in this plot since there is no current flowing in the vertical
direction. Also, the conduction band has dipped below the quasi-Fermi level within the
quantum well indicating an extremely large concentration of electrons there.
If the gate bias is increased, the first dip in the conduction band becomes closer and closer
to the quasi-Fermi level. This results in a large concentration of electrons at the top edge of
the AlGaAs spacer (where the delta doping is located). Current would then flow along the
top edge of the spacer rather than in the channel. This is undesirable since the mobility of
electrons flowing in the heavily doped spacer is much lower than in the undoped channel.
4.2.10 2D Plots
A 2D plot is now generated (lines 64-66) showing current flow in the device (see Figure
3.9). Observe that the current is flowing within the channel as expected, but that a small
amount of current (about 10%) is flowing along the top of the spacer. The FILL statement is
used to set color for a specified region.
Line 69 continues to reduce the gate bias in -0.1V steps until the gate voltage is - 0.8V. Line
71 plots the gate characteristics (Id versus Vgs) for the device (Figure 3.10). The device
cuts off at about -0.6V. The decreasing slope of the gate characteristic at higher gate biases
is caused by electrons from the channel being pulled out of the well and flowing along the
highly doped upper edge of the spacer, where the mobility is lower
Figure 3.9: Current flow generated by lines 64 through 66 in file mdex17
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Figure 3.10: Gate characteristics generated by line 71 in file mdex17
4.2.11 Lab Exercise (HEMT Simulation)
i.
Create new module under the same experiment. Name the module as
HEMT_SIMULATION.
ii.
Open the module. Load an icon and MEDICI driver.
iii.
Load the input file mdex17.inp from the lab_file directory.
iv.
Copy the mdex17.tif from lab_file directory, to twb library
% cp mdex17.tif <home_dir>/twb_workspace/libraries/LAB4/session/SIGE
v.
Run the module. Observe the graphs. Write down your observation
5. RESULTS
5.1 Capture and save all the results from :
i.
ii.
iii.
Lab Exercise: Device Structure and Plots (4.1.2)
Lab Exercise: Forward Bias Simulation (4.1.5)
Lab Exercise: HEMT Simulation (4.2.11)
(refer Basic Lab 1 on how to capture and save figure in jpeg format)
5.3 The saved results need to be included and discussed in your Basic Lab Report.
6. DISCUSSION
6.1 Write the discussions based on the results in the Basic Lab Report.
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7. CONCLUSION:
7.1 Conclude the lab work that has been done in Basic Lab 3 (based on simulation of SiGe
HBT & HEMT) and the results obtained. Write in Basic Lab Report.
8. REFERENCES
i.
ii.
iii.
iv.
v.
Taurus MEDICI-MEDICI– User Guide (Sept. 2004). Version W-2004.09.
Taurus MEDICI-Taurus Device-User Guide (Sept. 2004). Version W-2004.09.
Taurus Modeling Environment: Taurus Workbench – User Guide (Dec. 2004).
Version W-2004.12
Taurus Modeling Environment: Taurus Visual – User Guide (Dec. 2004). Version W2004.12
S.m. Sze (2002). Semiconductor Devices: Physics and Technology, John Wiley &
Sons.
 The Basic Lab 3 Report Format will be given in page 62
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BASIC LAB 4
INTRODUCTION TO DEVICE SIMULATION USING DAVINCI & TWB
1. OBJECTIVE:
1.4
1.5
1.6
To introduce students to Synopsys TCAD software.
To familiarize students with Taurus WorkBench (TWB).
To introduce students to NMOS Simulation using TWB and DAVINCI
2. INTRODUCTION
Davinci is a powerful device simulation program that can be used to simulate the behavior of
MOS and bipolar transistors, and other semiconductor devices. It models the threedimensional distributions of potential and carrier concentrations in a device. This program
can be used to predict electrical characteristics for arbitrary bias conditions. This Basic Lab
4 will use Davinci to analyze an N-channel MOS device.
3. COMPONENTS AND EQUIPMENTS
i.
ii.
Synopsys Taurus TCAD software
High-end PC
4. PROCEDURE
4.1 GENERATING THE SIMULATION STRUCTURE
The input file dvex1 creates the simulation structure for the n-channel MOS device. The
output associated with the execution of Davinci for the input file dvex1 is shown in File 4.1
through Figure 4.6.
1... TITLE
2... COMMENT
Synopsys DAVINCI Example 1 - 1.5 Micron N-Channel MOSFET
Specify a rectangular mesh
3... MESH
4... X.MESH
SMOOTH=1
WIDTH=3.0 H1=0.15
5...
6...
7...
8...
9...
NODE=1 L=-0.025
NODE=3 L=0.0
DEPTH=1.0 H1=0.125
DEPTH=1.0 H1=0.250
WIDTH=1.5 H1=0.200
Y.MESH
Y.MESH
Y.MESH
Y.MESH
Z.MESH
10... COMMENT
11... ELIMIN
Eliminate some unnecessary substrate nodes
COLUMNS Y.MIN=1.1
12... COMMENT
13... REGION
14... REGION
Specify oxide and silicon regions
SILICON
OXIDE IY.MAX=3
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15...
16...
17...
18...
19...
COMMENT
ELECTR
ELECTR
ELECTR
ELECTR
Electrode definition
NAME=Gate TOP X.MIN=0.75 X.MAX=2.25
NAME=Substrate BOTTOM
NAME=Source X.MAX=0.6 IY.MAX=3 Z.MAX=0.75
NAME=Drain X.MIN=2.4 IY.MAX=3 Z.MAX=0.75
20...
21...
22...
23...
... +
24...
... +
25...
26...
COMMENT
PROFILE
PROFILE
PROFILE
Specify impurity profiles and fixed charge
P-TYPE N.PEAK=3E15 UNIFORM OUT.FILE=DVEX1DS
P-TYPE N.PEAK=2E16 Y.CHAR=.25 Z.MAX=0.75
N-TYPE N.PEAK=2E20 Y.JUNC=.34 XY.RAT=.75 ZY.RAT=.75
X.MAX=0.6 Z.MAX=0.75
N-TYPE N.PEAK=2E20 Y.JUNC=.34 XY.RAT=.75 ZY.RAT=.75
X.MIN=2.4 Z.MAX=0.75
QF=1E10
BOX GRID BOUND TITLE=”Example 1 - Initial Grid” FILL
PROFILE
INTERFAC
PLOT.3D
27... COMMENT
28... REGRID
... +
29... PLOT.3D
Regrid on doping
DOPING LOG IGNORE=OXIDE RATIO=2 SMOOTH=1
IN.FILE=DVEX1DS ^Z.REGRID
BOX GRID BOUND TITLE=”Example 1 - Doping Regrid” FILL
30... COMMENT
31... CONTACT
Specify contact parameters
NAME=Gate N.POLY
32... COMMENT
33... MODELS
Specify physical models to use
CONMOB SRFMOB FLDMOB
File 4.1: Davinci output showing first part of simulation input file dvex1
34...
35...
36...
37...
COMMENT
SYMB
METHOD
SOLVE
Symbolic factorization, solve, regrid on potential
CARRIERS=0
ICCG DAMPED
38... REGRID
... +
39... SAVE
40... PLOT.3D
... +
POTEN IGNORE=OXIDE RATIO=.2 MAX=1 SMOOTH=1
IN.FILE=DVEX1DS
MESHFILE OUT.FILE=DVEX1MS W.MODELS
BOX GRID BOUND TITLE=”Example 1 - Potential Regrid”
FILL
41...
42...
43...
44...
45...
... +
... +
46...
... +
... +
47...
48...
49...
Solve using the refined grid,save solution for later use
CARRIERS=0
OUT.FILE=DVEX1S
Impurity profile plots
DOPING Y.LOG X.START=.25 X.END=.25 Y.START=0 Y.END=2
Z.START=0.25 Z.END=0.25 POINTS BOT=1E15 TOP=1E21
COLOR=2 TITLE=”Example 1 - Source Impurity Profile”
DOPING Y.LOG X.START=1.5 X.END=1.5 Y.START=0 Y.END=2
Z.START=0.25 Z.END=0.25 POINTS BOT=1E15 TOP=1E17
COLOR=2 TITLE=”Example 1 - Gate Impurity Profile”
BOX BOUND TITLE=”Example 1 - Impurity Contours” FILL
DOPING LOG MIN=16 MAX=20 DEL=.5 COLOR=2
DOPING LOG MIN=-16 MAX=-15 DEL=.5 COLOR=1 LINE=2
COMMENT
SYMB
SOLVE
COMMENT
PLOT.1D
PLOT.1D
PLOT.3D
CONTOUR
CONTOUR
File 4.2: Davinci output showing second part of simulation input file dvex1
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4.1.1 Mesh
The structure of the device is created through the mesh. Various regions of the device, such
as semiconductor, insulator, and electrodes, are defined in terms of the mesh. Distortions of
the mesh are then used to give the device its designed surface topography.
4.1.2 Defining the Initial Mesh
The first step in creating a device structure is to define an initial mesh, as in lines 3 through
9 of the input file shown in File 4.1.
Note:
The initial mesh is refined later for a simulation. At this point it needs to be only fine enough
to define the regions of the device.
Specify a MESH statement to initiate the mesh generation. Use MESH also to request
smoothing. Smoothing minimizes problems caused by obtuse triangles that may be
generated if SPREAD statements are used subsequently. The X.MESH, Y.MESH, and
Z.MESH statements specify the number and placement of grid lines in the structure.
The x-direction spacing of mesh lines with the X.MESH statement. The X.MESH statement
at line 4 creates a grid section extending from x=0 microns (the default starting location) to
x=3 microns. Specifying the single parameter H1=0.15 creates a uniform mesh in the xdirection with a grid spacing of 0.15 microns. Specify the y-direction spacing of mesh lines
with the Y.MESH statements. The first three horizontal mesh planes define a surface oxide
with a thickness of 0.025 microns. This is the gate oxide thickness for this device. Use
Y.MESH statements to explicitly place the first line of nodes at y=-0.025 microns and the
third line of nodes at y=0 microns.
Note:
It is convenient to set up a grid which places the insulator-semiconductor interface at y=0.
The Y.MESH statement at line 7 adds a grid section to the structure with a depth of 1 micron
and a uniform spacing between mesh lines of 0.125 microns. The final Y.MESH statement
adds another 1 micron grid section which has a uniform spacing of 0.250 microns
Specify the z-direction spacing of mesh lines is specified with the Z.MESH statement on line
9. This creates a 1.5 micron section with a spacing between consecutive z planes of 0.2
microns.
4.1.3 Eliminating Excess Nodes
A requirement of fine grid in one region of the device propagates fine grid throughout the
device. This makes a rectangular grid inefficient. Davinci uses a triangular prismatic grid that
does not have this limitation in the xy plane. To take best advantage of the triangular grid,
the program terminates many of the ydirection grid lines within the device, since a fine mesh
is only needed near the surface and not deep in the bulk. The ELIMIN statement in line 11
removes every other column of nodes in the structure for values of y greater than 1.1
microns.
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4.1.4 Device Regions
The regions of the device are defined beginning with Line 13 by the REGION statements.
The first REGION statement defines the entire structure to be silicon. The second REGION
statement redefines the elements contained by the three uppermost grid lines to be oxide.
4.1.5 Electrode Locations
The ELECTRODE statements specify the location of the electrodes within the device. In this
example:
• The gate is placed at the top surface of the oxide.
• The substrate contact placed along the bottom of the device.
• The source and the drain are driven through the oxide to contact the oxide-silicon interface
at the left and right edges of the device.
4.1.6 Impurity Profiles
The impurity profiles are created analytically from Gaussian functions. Alternatively, they can
be read from Medici, TMA SUPREM-3, TMA SUPRA, TSUPREM-4, or 1D, 2D, or 3D
formatted files. In this example, since a n-channel enhancement device is being created:
• The first PROFILE statement specifies use of a uniform p-type substrate.
• The second PROFILE introduces a p-type threshold adjustment profile.
• The remaining PROFILE statements define the n+ source and drain regions. The source
and drain are specified to have a junction depth of 0.34 microns with a lateral out-diffusion
that is 0.75 times their vertical extent.
• The INTERFAC statement at line 25 places a uniform fixed charge along the entire oxidesilicon interface.
4.1.7 Output File Specification
Specify the output file on the first PROFILE statement to save the profile information.
Thereafter, whenever the grid is refined, you can regenerate the impurity distribution from
the original profile specification.
CAUTION
Always specify an output file to avoid interpolation errors. If this is not done, the doping at the
nodes of the refined mesh is interpolated from the doping at the nodes of the unrefined mesh.
4.1.8 Initial Grid Plot
Figure 4.1 shows the device structure and the grid before any refinement.
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Figure 4.1: Initial grid generated by the PLOT.3D statement at line 26 in the simulation input file
dvex1 (File 4.1 & 4.2)
4.1.9 Grid Refinement
At this point the device structure has been defined. It is now necessary to refine the grid so
that it is adequate for a simulation.
4.1.10 Doping Regrid
Request the first phase of grid refinement with the REGRID statement on Line 28 in File 4.1.
The REGRID statement causes an existing triangular prism to be subdivided longitudinally
into four congruent prisms. This occurs whenever the impurity concentrations at the nodes
of the triangle differ by more than two orders of magnitude.
Note:
To reduce the number of nodes required by the simulation, and reduce the running time,
^Z.REGRID parameter was specified on this REGRID statement.
Normally, both xy regrids and z regrids are performed by default, which would cause prisms
to be subdivided both longitudinally and lengthwise. Specify smoothing to minimize the
adverse effects caused by obtuse triangles. The IGNORE parameter is set equal to oxide so
that neither grid refinement nor smoothing is done in the oxide. The saved profile file is used
for finding the impurity concentrations on the new grid. The resulting grid is shown in Figure
4.2 where the junction locations are clearly seen with the increased grid density.
The second grid refinement is based on the potential difference between nodes and requires
a solution be obtained on the existing grid. Before solving, choose from various MODELS on
line 33 of the dvex1 input file.
i.
Select the gate material to be n+ polysilicon.
ii.
Choose concentration and electric field-dependent mobility models with the
parameters CONMOB and FLDMOB, respectively.
iii.
Specify surface mobility reduction by SRFMOB.
iv.
Since only the potential is needed at this point, a Poisson-only solution is
selected by setting CARRIERS equal to zero on the SYMB statement.
54
EMT 471/3 – Semiconductor Physics
v.
vi.
vii.
viii.
Laboratory Module
In most cases, specifying ICCG and DAMPED on the METHOD statement
results in the most efficient zero carrier simulation.
The SOLVE statement generates the solution. The initial biases are defaulted to
zero. The grid refinement based on potential (line 38) is similar to the refinement
based on impurity concentration.
The absence of the LOG parameter means that refinement is based on the
absolute change in potential. The change in potential is specified to be 0.2V with
RATIO.
Set the MAX parameter to one to prevent the elements of the original mesh from
being subdivided more than once. MAX is the maximum number of times any
grid element can be subdivided, relative to the original grid. It defaults to one
more than the current maximum level of the grid. The most effective grid
refinement occurs when MAX is one more than the previous maximum for a
refinement based on the same quantity.
Figure 4.2: Davinci graphical output generated by the PLOT.3D statement at line 29 in the simulation
input file dvex1 (File 4.1 & 4.2)
As is the last refinement, the mesh is saved in an output file for subsequent simulations.
Figure 4.3 shows the final mesh.
Figure 4.3: Potential regrid generated by the PLOT.3D statement at line 40 in the simulation input file
dvex1 (File 4.1 & 4.2)
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4.1.11 Saving Initial Solution
To provide a starting point for subsequent simulations, a zero bias solution is obtained and
saved for the final mesh.
The SYMB statement must be specified again before using the SOLVE statement to obtain
the next solution. This is due to the number of nodes in the mesh having changed since the
last solution was obtained.
The current level in the device is expected to be very low with no bias applied. Therefore, it
is sufficient to obtain and save a zero carrier solution.
4.1.12 Impurity Distribution Plots
Figures 4.4 through 4.6 show the impurity distribution for this device as a consequence of
the plot statements at the end of the input file.
Figure 4.4: Source impurity profile generated by the PLOT.1D statement at line 45 in the simulation
input file dvex1
Figure 4.5: Gate impurity profile generated by the PLOT.1D statement at line 46 in the simulation
input file dvex1
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Figure 4.6: Impurity contours generated by the PLOT.3D and CONTOUR statements at line 47
through 49 in the simulation input file dvex1
4.1.12 Lab Exercise: Generating the Simulation Structure
i.
Invoke TWB (TAURUS WORKBENCH).
Create new project and new experiment.
Name the new project as LAB6 and the new experiment as THREE_D_NMOS.
ii. Open the THREE_D_NMOS experiment. Create a new module. Name the module
As THREE_D_NMOS_STRUCTURE.
Tips: Refer to Lab1, if you have problem with step i and ii
iii. In the THREE_D_NMOS_STRUCTURE module, select an icon and load the
DAVINCI driver.
Tips: Open standard Library
from TWB workspace,
In Tools tap, copy and paste layout icon into “Lab6” Library, Tools tap.
Repeat the step, copy all the driver icons from SimulatorDrivers tap into
“Lab6”Library, SimulatorDrivers tap.
From SimulatorDrivers tap, drag and drop the davinci driver to Driver column
of Module “THREE_D_NMOS_STRUCTURE”.
iv. Go to the menu bar and select FILE > LOAD FROM COMMAND INPUT FILE.
Load the input file dvex1.inp from the lab_file directory
v. Run the module. Observe the graphs. Write down your observation.
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EMT 471/3 – Semiconductor Physics
Laboratory Module
5. RESULTS
5.1 Capture and save all the results from Lab Exercise: Device Structure and Plots (4.1.12)
(refer Basic Lab 1 on how to capture and save figure in jpeg format)
5.3 The saved results need to be included and discussed in your Basic Lab Report.
6. DISCUSSION
6.1 Write the discussions based on the results in the Basic Lab Report.
7. CONCLUSION:
7.1 Conclude the lab work that has been done in Basic Lab 4 and the results obtained. Write
in Basic Lab Report.
8. REFERENCES
i.
ii.
iii.
iv.
v.
Taurus MEDICI-DAVINCI– User Guide (Sept. 2004). Version W-2004.09.
Taurus MEDICI-Taurus Device-User Guide (Sept. 2004). Version W-2004.09.
Taurus Modeling Environment: Taurus Workbench – User Guide (Dec. 2004).
Version W-2004.12
Taurus Modeling Environment: Taurus Visual – User Guide (Dec. 2004). Version W2004.12
S.m. Sze (2002). Semiconductor Devices: Physics and Technology, John Wiley &
Sons.
 The Basic Lab 4 Report Format will be given in page 63
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