importing and using tcad electric fields in allpix squared
TRANSCRIPT
Importing and Using TCAD Electric Fields in Allpix Squared
AllpixSquared User Workshop
27.11.2018
Magdalena Munker (CERN)
Motivation
—> See example from Daniel yesterday:
Without TCAD, Monte Carlo Simulations can adequately model linear electric fields (standard planar sensors)
However, our use cases are often different (non-linear fields):
HV-CMOS, CERN-THESIS-2018-114:HR-CMOS example:
Many more examples, e.g. Enhanced LAteral Drift (ELAD) sensors from Hendrik Jansen & Anastasiia Velyka (DESY)
—> It is essential for many applications to model the electric field
Note:AllpixSquared uses the results from TCAD —> you have to do the TCAD simulations fist … p. 1
Outline
- Synopsys Sentaurus Sentaurus Data Explorer tool- AllpixSquared: mesh converter, mesh plotter, electric field reader
Importing the electric field:
- An example - next generation of CMOS sensors with a small collection electrode
Using the electric field:
- Finite element simulation, e.g. Synopsys Sentaurus Simulating the electric field:
This talk focuses on
Synopsys Sentaurus
—> Tools from the Allpix side are
generic for any FE simulator that
produces DF-ISE files
p. 2
Simulating the electric field
For further more detailed material see:
TCAD Synopsys Sentaurus
p. 3
https://www.synopsys.com/silicon/tcad.html
Simulation of semiconductor processing, device operation and interconnect characterization for technology development and manufacturing
Getting started:
Commercialised tool —> need licence (depending on your Institute)
STROOT=‘path_to_software’
export STROOT
export PATH=$STROOT/bin:$PATH
export LM_LICENSE_FILE=‘your_licence_file’
export STDB=$PWD
Create your work directory with source file:
Open workbench:
swbGraphical user interface (GUI) Simplifies complex simulations by parametrisation & visualisation}
Using the Synopsys Sentaurus workbench
p. 4
Getting help, manuals and examples:
Creating a new project:Examples
Manuals
Using the Synopsys Sentaurus workbench
p. 5
Using tools:
Process simulation SPROCESS:
- Simulation of doping profiles
- GDS file and process details as input
Structure editor SDE:
- Generation of structure (geometry)
- Mesh generation
Device simulation SDEVICE:
- Simulation of device operation
- Simulation of charge deposition
Inspection INSPECT:
- Calculation or results, e.g. charge …
Using the Synopsys Sentaurus workbench
p. 6
Creating tools:
Using the Synopsys Sentaurus workbench
p. 7
Adding source code:The commands file will contain your source code:
- Written in scheme- Well documented in the manuals how to
write the source code for different tools
Using the Synopsys Sentaurus workbench
p. 8
Adding parameters:
Parameters read in command file:(define ‘code_name’ @‘swb_name’@)
Using the Synopsys Sentaurus workbench
p. 9
Running the simulation:
- Select the node and click on the run-bottom- Select queue (local, batch)
Using the Synopsys Sentaurus workbench
Visualising the simulation output:
p. 10
- The node explorer gives easy acess e.g. to log files, used command files, simulation results, ..
- Simulation results stored in binary *.tdr files
- Plot interface opened by double click
Importing the electric field
- Results of TCAD simulations are stored in tdr-binary file format - Accessible with workbench, e.g. for plotting
TCAD Synopsys Sentaurus output format:
- Easy to use command line interface- Conversion to editable DF-ISE files:
Synopsys Sentaurus data explorer:
DF-ISE output file:- *.grd file containing all mesh points- *.dat file containing results calculated on mesh
tdx --tdr2dfise ‘tdr_input_file’ ‘dfise_output_file’
Importing the electric field - Synopsys Sentaurus Data Explorer
Used as input for AllpixSquared}
More infos and help:
—> Sentaurus™ Data Explorer
User Guide
3D simulation of electric field for CMOS sensors with a small collection electrode:
p. 11
AllpixSquared mesh converter (Mateus Vincente)
allpix-squared/bin/mesh_converter
-f ‘dfise_output_file’
-c ‘mesh_converter.conf’
-o ‘converter_output_file’
Mesh converter:- Load fine TCAD mesh once
- Selected model region is scanned in regular x,y,z-steps (regular mesh)
- Barycentric interpolation using nearest neighbours is used to calculate results on regular mesh—> Binary ‘mesh_converter’executable with following arguments:
Note:
—> Tools from the Allpix side are
generic for any FE simulator that
produces DF-ISE files
Electric field and TCAD mesh (black lines):
p. 6p. 12
AllpixSquared mesh converter
region = bulk
dimensions = 3
observable = ElectricField
xyz = x,z,-y
mesh_tree = true
Dimension of TCAD simulations
Model region of TCAD simulations
Observable to convert to regular mesh in model region
Flip coordinate system
Creation of *.root file with TCAD output (nice for debugging)
(Mateus Vincente)
Mesh plotter:
Example of config file for mesh converter:
Visualisation of mesh interpolation:
p. 7p. 13 bin/tcad_dfise_converter/mesh_plotter -f ‘converter_output_file’
AllpixSquared electric field reader (Koen Wolters, Simon Spannagel)
ElectricFieldReader:
file_name = ‘converter_output file’
model = ‘init’
depletion_depth = ‘depth simulated in TCAD’
[ElectricFieldReader]
Example of section in global config to import TCAD field:
- Load electric field from ‘converter_output_file’ by setting the parameter of the model
- If a two dimensional field is stored in the ‘converter_output_file’ the third dimension is stretched —> strip like geometry
A note on dimensions:
- The parameter ‘depletion_depth’ has to be set to the depth of the electric field simulated in TCAD- A zero field is used in the rest of the simulated structure
- If not, the electric field is scaled to the thickness of the value of ‘depletion_depth’
A note on parameters:2D TCAD simulation:
Stretch of 3rd dimension in AllpixSquared:
Depletion depthRest of simulated structure
with zero field
name = ‘detector you want to apply it on’
p. 8p. 14
Allpix electric field reader (Koen Wolters, Simon Spannagel)
Different geometries simulated in TCAD:
Collection electrode
[ElectricFieldReader]
Default
field_scale = 1 1
field_offset = 0 0
field_scale = 1 1
[ElectricFieldReader]
field_offset = 0.5 0.5
field_scale = 0.25 0.25
[ElectricFieldReader]
field_offset = 0.5 0.5field_scale = 2 2
[ElectricFieldReader]
field_offset = 0 0
Centre of AP2-CS
Unit cell simulated in TCAD
Ensure correct mapping into AllpixSquared Coordinate System (AP2-CS) with two parameters:- field_scale: Allows to use electric field for multiple or fraction of pixels, normalised to single pixel cell- field_offset: Allows to shift the Unit cell simulated in TCAD w.r.t. the AP2-CS
p. 9p. 15
Using the electric field
Example use case - next generation of HR CMOS sensors
p. 10p. 16
Faster charge collection (known from transient TCAD simulations)
Electrode P-well
HR epi layer
Electrode P-well
HR epi layer
N-layer
Electrode P-well
HR epi layer
N-layer
Question:Which design is favorable in view of spatial resolution?
Simulation setup:CLICTD - fully monolithic CLIC tracker chip with a pixel size of 30 µm x 37.5 µmSetup as explained in Simons talk
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p. 17
Next generation of HR CMOS sensors - charge sharing
CLICdp work in progress
CLICdp work in progress
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Next generation of HR CMOS sensors - charge sharing
CLICdp work in progress
CLICdp work in progress
p. 18
0.02− 0.015− 0.01− 0.005− 0 0.005 0.01 0.015 0.02
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σ ~ 3 μm
Next generation of HR CMOS sensors - resolution
Residual in x [μm] Residual in x [μm]
σ ~ 4 μm
p. 19
CLICdp work in progress
CLICdp work in progress
Threshold of 50 electronsThreshold of
50 electrons
Summary
Why to use results of electrostatic TCAD simulation in AllpixSquared:- Modelling of non linear electric fields
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How to use results of electrostatic TCAD simulation in AllpixSquared:- Little intro to TCAD- Intro to mesh converter and electric field reader in AllpixSquared - Presentation of use-case for CLIC
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p. 20
Backup
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Allpix lineplots
p. 17
DF-ISE output files
DF-ISE output files:- Data is grouped in model regions- Observables of TCAD simulations (e.g. electric field vector) are stored for each mesh point- Definition of model regions (name and geometry) and mesh are defined in TCAD