importing and using tcad electric fields in allpix squared

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

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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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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

-

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