Lecture 8 Detectors for Ionizing Particles
Content Introduction Overview of detector systems Sources of radiation Radioactive decay Cosmic Radiation Accelerators Interaction of Radiation with Matter General principles Charged particles heavy charged particles electrons Neutral particles Photons Neutrons Neutrinos Definitions Detectors for Ionizing Particles Principles of ionizing detectors Gas detectors Principles Detector concepts Wiederholung V6
Semiconductor detectors Semiconductor basics Sensor concepts Different detector materials Readout electronics Scintillation detectors General characteristics Organic materials Inorganic materials Light output response Content Velocity Determination in Dielectric Media Cerenkov detectors Cerenkov radiation Cerenkov detectors Transition Radiation detectors Phenomenology of Transition Radiation Detection of Transition Radiation Complex Detector Systems Particle Identification with Combined Detector Information Tracking
Semiconductor Detectors
Semiconductor Detectors A semiconductor detector is a solid state ionization chamber Gas Semiconductor Z 2 18 14-50 E(e/ion) creation 30 40 ev 3 4.5 ev specific density 0.17 (He) 0.9 (Ne) g l -1 2.33 (Si) 5.3 (Ge) g cm -3 pairs per length 100 e/ions per cm 100 e/h per µm e mobility O(1000 cm 2 /Vs) 1000 9000 cm 2 /Vs ion(hole) mobility 1 2 cm 2 /Vs 50 2000 cm 2 /Vs
pn - junction p n
pn junction as particle detector p + n - thin, highly doped p + (~10 19 cm -3 ) layer on lightly doped n - (~10 12 cm -3 ) substrate Space charge region N A de dx x p N D x 1 ( x) n neutrality cond. Maxwell Electric field!! E( x) en en A D ( x x ( x x p n ) ) for for x p x 0 x x n 0 Potential V bi e N 2 A x 2 p N D x 2 n
pn junction under reverse bias (V ext ) 1. V bi V bi + V ext 2. no thermal equilibrium => E F (n) E F (p) no bias Hole current Electron current p n forward bias Depletion region Depl. I p n reverse bias Depl. I
pn junction as particle detector Depletion zone grows from the junction into the lower doped bulk
Metal-semiconductor junction metal semiconductor note work function M depends on type of metal S depends on doping S = electron affinity = E vac E C is independent of doping Schottky Contact =potential barrier i.e e S < e m
VORLESUNG 8
Silicon Detector (principle sketch)
Single sided processing
Single sided processing C f - U=Q in / C f + +HV DC - Coupling
Single sided processing -HV R bias C f - U=Q in / C f + AC - Coupling
Realisation of AC coupling
Photolithography n - silicon wafer oxidation at ~1000 C photolithography on SiO 2 p + -doping by ion implantation curing at 600 C, 30 min addition of Al layer lithography on Al oxidised Si wafer coating with photoresist mask exposure of photoresist development edging removal of photoresist
Single sided processing
Biasing Polysilicon Biasing
FOXFET & Punch-Through Biasing V < V pt V V pt Punch Through Biasing V > V pt
Biasing of Pixel Detectors Jörn Große-Knetter
Double sided readout: insulation problems p + n n +
Double sided microstrip detector top side read-out strips bias strips bottom side p-type insulation
n-on-n segmentation p-on-n sensor n-on-n sensor Initial undepleted state undepleted After irradiation undepleted undepleted
Capacitive charge division
Capacitive charge division read Q collected Q incoming particle intermed. strip incoming particle
- distribution for position-interpolation simple expectation: = Q L /(Q R +Q L ) x = η*d not quite correct, use more complex function:
- distribution for position-interpolation ideally symmetric but: parasitic capacitances and r/o specifics intermediate strips intermediate structure in η Jörn Große-Knetter
Disturbing effects incoming particle ~300μm -electron reconstr. position effect of -electrons 100 kev -electron occurs in 300 µm Si with 6% probability; has range of 60 µm
Disturbing effects measured width of the charge distribution no B-field with B-field influence of Lorentz angle
Small pixel effect - II weighting potential for different pixel sizes first central neighbour
{ Weighting field and signal formation moving charge moving charge signal observed here
Sideward Depletion 37
Silicon Drift Detectors ~ 10 µm resolution over 5 10 cm drift distances drift velocity must be predictable low trapping problem with radiation damage 38
Cylindrical Si-Drift Detector 39
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MONOLITHIC DETECTORS
MOS (optical) CCD 43
s y m m e t r y a x i s 50 µm DEPleted Field Effect Transistor source top gate drain MIP clear bulk Potential distribution: ~1µm p+ + p n+ p+ n+ n+ ----- + - + - + - n internal gate n - Backcontact Source internal Gate Drain p+ rear contact [TeSCA-Simulation] FET-Transistor integrated in every pixel (first amplification) Electrons are collected in internal gate and modulate the transistor-current Signal charge removed via clear contact 44
s y m m e t r y a x i s 50 µm DEPleted Field Effect Transistor source top gate drain +15 V 0V clear 0V bulk Potential distribution: p+ p n+ p+ n+ n+ ----- n internal gate Backcontact internal Gate Drain n - Source p+ rear contact [TeSCA-Simulation] FET-Transistor integrated in every pixel (first amplification) Electrons are collected in internal gate and modulate the transistor-current Signal charge removed via clear contact 45
Minosa Active PixelS Signal created in low-doped epitaxial layer (typically ~10 μm) Charge sensing in n-well/p-epi junction Charge collection mainly through thermal diffusion (~100 ns), reflective boundaries at p-well and substrate Sensor and signal processing integrated in the same silicon wafer Standard commercial CMOS technology High granularity Fast readout, low noise, low power dissipation 46
SOI Pixel Detector Monolithic detector using Bonded wafer (SOI : Silicon-on-Insulator) of Hi-R and Low-R Si layers. No mechanical bump bondings -> High Density, Low material budget -> Low parasitic Capacitance, High Sensitivity Standard CMOS circuits can be built Thin active Si layer (~40 nm) -> No Latch Up, Small SEE Cross section. Based on Industrial standard technology 47 Seamless connection to Vertical Integration Yasuo Arai 47
OKI 0.2 mm FD-SOI Pixel Process Process SOI wafer Backside 0.2mm Low-Leakage Fully-Depleted SOI CMOS (OKI) 1 Poly, 4 (5) Metal layers, MIM Capacitor, DMOS option Core (I/O) Voltage = 1.8 (3.3) V Diameter: 200 mm, Top Si : Cz, ~18 -cm, p-type, ~40 nm thick Buried Oxide: 200 nm thick Handle wafer: Cz ~700 -cm (n-type), 650 mm thick Thinned to 260 mm and sputtered with Al (200 nm). An example of a SOI Pixel cross section Yasuo Arai 48
3D-Integration
3D-Integration R. Yarema
3D-Integration
3D-Integration
3D-Integration
3D-Sensors
3D-Sensors
Enver Alagoz
Size of Collider Si-Detectors 54 cm 57
ATLAS Silicon Tracker Micro Strip Detector 15.000.000 Strips Pixel Detector 80.000.000 Pixel 58
ATLAS silicon strip detector 60 m 2 of Si, ~4000 modules barrel during module mounting 59
Micro Strip Detector 60
ATLAS Si-Strip Detector 61
CMS silicon strip detector ~19000 modules 250m 2 of Si 62
ATLAS pixel module viewed from sensor side MCC sensor flex-hybrid FE-Chip FE-Chip pigtail viewed from chip side 16 IC, 46080 pixels
ATLAS pixel detector 1m close (5cm) to interaction point ~10 8 pixels (50x400 µm 2 ) ~1000 pixels hit every 25 ns ASIC Chip Development 64
ATLAS Pixel-Detector 65