Update on TCAD Simulation Mathieu Benoit

Introduction The Synopsis Sentaurus Simulation tool – Licenses at CERN – Integration in LXBatch vs Engineering Machine Principles of TCAD simulation – Process simulation implantation Lithography Diffusion/Activation – Device simulation DC Simulation Transient simulation Simulation results on medipix-like n-in-p thin pixel sensors

The Synopsis Sentaurus Simulation tool 2 Licenses available at CERN through europractice – One license for RD50 – One license available to all (microelectronics group) – 20 licenses (2000 €) to be delivered to CLIC-LCD in mid-February 2 possibility to perform simulation : – Sentaurus workbench tools allow for automatic handling of LSF protocol -> lxbatch Limited number of CPU, RAM per simulation – Running on a local engineering machine Many CPU available for parallel computing Large amount of RAM Parameter exploration 3D simulation

The Synopsis Sentaurus Simulation tool Example : 2D Process Pixel simulation – nodes, 7 min of simulation – 64.7% of time spent in solver Pardisio (277.6 s) Example : 2D DC Device simulation – 157s of simulation to obtain solution a one bias point Example : 2D Transient simulation (mip) – 3h09m of simulation -> 1h06m of real time running on 3 CPU (lxplus) – Gb of RAM used

Process Simulation 1st Backside implantation – Oxide deposition (40nm) – Boron implantation (10^15/cm2, 60 keV) – Contact etching (oxide) 2nd P-Spray Implantation (n-readout) – Deposition of a screening oxide (200nm) – Deposition of a nitride layer (200nm) – Boron implantation (10^12/cm2, 120 keV ) 3rd Read-out implantation – Etching of the nitride layer in implant location – Etch of oxide in implanted down (40 nm of screening oxide left) – Implantation of phosphorus (10^15/cm2, 60 keV) 4th Diffusion/activation of the implants – Heating of the wafer in the oven in a nitrogen atmosphere (3 C (RTA) or ≈10 min at 960C (classic) ) 5th Contact etching and metal deposition – Opening of pillar in 40nm oxide for contact between metal and implants – Deposition of ≈ 800nm of Aluminum – Passivation (not simulated) – Opening in passivation (not simulated)

Process Simulation N+ Implant Provide Ohmic contact with Aluminum Form the main junction of the diode Al Electrode Provide Ohmic contact with implant Formation of field plates around implant P-Spray insulation Cut the electron channel between electrodes Increase radiation hardess (ionizing damage)

Process Simulation N+ Implant Provide Ohmic contact with Aluminum Form the main junction of the diode Al Electrode Provide Ohmic contact with implant Formation of field plates around implant P-Spray insulation Cut the electron channel between electrodes Increase radiation hardess (ionizing damage)

Process Simulation Doping width Pixel pitch Thickness P-Spray Dose/Energy N implant dose/Energy P+ implant dose/Energy Diffusion time/temperature The 2D Pixel model is parametrized

TCAD Device simulation principles 5th "Trento" Workshop on Advanced Silicon Radiation Detectors, Manchester, UK 9 It can be proven the analytical solution is part of an Hilbert space. By choosing a set of basis function covering this Hilbert space, we can truncate this set and obtain an aproximate solution if the solution is locally polynomial over each mesh element ’s domain

Physics Models Mobility Concentration-dependent mobility (fit to experimental data), Parallel field dependent mobility (fit to experimental saturation velocities) Generation recombination and trapping Modified concentration dependent Shockley-Read-Hall Generation/recombination (for treatment of defects) Impact ionization Selberherr’s Impact ionization model Tunneling Band-to-band tunnelling, Trap-Assisted tunneling Oxide physics Fowler-Nordheim tunnelling, interface charge accumulation 10

Generation/Recombination Modified Shockley-Read-Hall G/R – A sum of SRH contribution by each trap – Γ is the degeneracy of the trap, n i the intrinsic concentration of carriers 11

Generation/Recombination Transient behaviour of traps σ n,p is trap capture cross-section v n,p is thermal velocity n i is intrinsic concentration F tA,TD the probability of ionization N tA,TD space charge density 12 Electron capture Electron capture Electron emmision Electron emmision Hole capture Hole capture Hole emmision Hole emmision hole capture hole capture hole emmision hole emmision electron capture electron capture electron emmision electron emmision

Device Simulation While computing power is limited, focus was put on 2D simulation of pixel geometries – Valid for « decoupled » region of a pixel Rise time of the pulse Charge sharing – Not valid for corners region, fondamentally 3D quantities Leakage current 3-4 pixel charge sharing 2D simulation assume a z dimension of 1um to conserve dimension in the drift-diffusion equation

Device Simulation DC Simulation : – Three thicknesses studied : 50,100,150 um – Three doped region width studied : 35,40,45 um – 4 bias voltages : -2.5V, -5V,-7.5V, -10V Transient simulation : – M.I.P trajectory normal to surface – impact a 0, 1,2,3, 5 um from middle point between pixels

Device Simulation: Potential distribution -2.5V-5V -7.5V-10V

P-spray insulation -2.5V-5V -7.5V-10V

Charge collection See AnimationAnimation

Pulse Shape and Rise time 50 um thick sensors, 55um pitch, 45um electrodes

Pulse Shape and Rise time 50,100,150 um thick sensors, 55um pitch, 45um electrodes

Pulse Shape and Rise time 50,100,150 um thick sensors, 55um pitch, 45um electrodes

Pulse Shape and Rise time 50 um thick sensors, 55um pitch, 45um electrodes

Charge Sharing 50um thick sensors, 55um pitch, 45um electrodes ΔX is the distance front middle point between pixels

Charge Sharing 50um thick sensors, 55um pitch, 40um electrodes ΔX is the distance front middle point between pixels

Conclusion TCAD Simulation software deployed at CERN – 20 license on the way to perform massive parameter scan and analysis – Possibility right now to perform complex 2D Simulation – Preliminary results show rise time not an issue for timing, timing in pixel cluster might be an issue To-Do – Extend simulation to 3D – Input Eta functions in digitizer to compare with actual results – More studies possible (biasing through vias ?, Heat, stress effects ?)