Anthony Affolder University of Liverpool

Anthony Affolder University of Liverpool
Latest Developments in Planar n-on-p Sensors: Transitioning from R&D to pre-production Anthony Affolder University of Liverpool Material from a host of people: J. Bohm, M. Boscardin, G. Casse, M. Chistophersen , V. Cindro, A. Dierlamm, V. Fadeyev, D. Forshaw, A. Gallas, K. Hara, F. Hartmann, J. Kalliopuska, G. Kramberger, J. Lange, A. Macchiolo, G. Pellegrini, N. Unno, …

A. Affolder – VERTEX 2011, 19-24 June 2011, Rust, Austria
Outline A Little History Unexpected large collected charge Current Sensor Productions Strips/Pixels Thin/Thick Current R&D Reduced edges (thin, passivated, active) Enhanced multiplication (trenches, geometry) A. Affolder – VERTEX 2011, June 2011, Rust, Austria

Charge Collection Studies
RD50 Unannealed Neutrons 900 V 900 V Unannealed 26 MeV Protons All n-strip readout substrates studied become more and more similar with irradiation. This is true after neutron, proton and pion irradiations and with Hamamatsu and Micron devices. Micron Neutrons: A. Affolder, et. al., Nucl. Instr. Meth. A, Vol. 612 (2010), Micron 26 MeV Protons: A. Affolder, et. al., Nucl. Instr. Meth. A, Vol.623 (2010), HPK Neutrons: K. Hara, et. at., Nucl. Inst. Meth. A, Vol. 636 (2011) S83-S89. HPK 26 MeV Protons: New and unpublished A. Affolder – VERTEX 2011, June 2011, Rust, Austria

Charge Multiplication Studies
RD50 I. Mandic, et. al., Nucl. Instr. Meth. A, Vol. 603 (2009), G. Casse, et. al., Nucl. Instr. Meth. A, Vol. 624 (2010), full charge collection (300 mm) full charge collection (140 mm) 300 µm More than 100% charge collection seen at high bias voltages after irradiation for both n-in-p strips and EPI Multiplication is consistent with high fields at implants Multiplication largest at segmented implant Current also correlated with charge as expected J. Lange, et. al., PoS (VERTEX 2010), 025. A. Affolder – VERTEX 2011, June 2011, Rust, Austria

Edge-TCT Measurements
RD50 Micron; FZ n-in-p, neutrons 5e15 cm-2 G. Kramberger, et. al., IEEE Tran Nucl Sci., Vol. 57 (2010), 2294. ve+vh[arb.] Active base Micron; FZ n—in-p, neutrons 5e15 cm-2 Sensor sensitive over entire depth at all bias voltages after high fluences (>5×1015 neq cm-2) Fields are larger than expected from assumption of intrinsic carrier concentration in “non-active” region. At 5×1015 neq cm-2 can be as high as 1 V/mm at 1000 V. At higher fluences and bias voltages charge multiplication seen The relative importance of the active base vs. charge multiplication depends on fluence/bias voltage Multiplication 750 V A. Affolder – VERTEX 2011, June 2011, Rust, Austria

Current detectors Prototyping productions
Onto production Current detectors Prototyping productions

Active p-type Foundries for HEP
Producers Wafer Size Thicknesses Productions 4” 150/200/285 ATLAS pixels, CMS pixels, RD50 150/300 ATLAS endcap strips, LHCb pixels, RD50 6” 300 ATLAS barrel strips 200 ATLAS pixels 150/200/320 ATLAS pixels/strips, CMS pixels/strips, LHCb strips 4”/6” 150/300/500 ATLAS pixels, LHCb pixels, RD50 75/150 ATLAS strips/pixels 100/200/300/500 ATLAS pixels, LHCb pixels A. Affolder – VERTEX 2011, June 2011, Rust, Austria

LHCb VELO 1 module currently installed with n-in-p FZ sensors Same efficiency, occupancy and resolution as n-in-n FZ devices Entire replacement VELO is being made with n-in-p FZ sensors P-type cost 70% of n-type Both with double metal on segmented n-side 1st half should be delivered to CERN by mid-June. Remainder by autumn p-type A. Affolder – VERTEX 2011, June 2011, Rust, Austria

ATLAS Thick Strip Sensors
Collaboration of ATLAS with Hamamatsu Photonics (HPK) to develop 9.75x9.75 cm n+-strip in p-type substrate devices (6 inch wafers) for strip regions 4 segments (2 axial, 2 stereo), 1280 strip each, mm pitch, ~320 mm thick FZ1 <100> and FZ2 <100> material studied Miniature sensors (1x1 cm2) for irradiation studies Axial Stereo See N. Unno, et. al., Nucl. Inst. Meth. A, Vol. 636 (2011) S24-S30 for details Full-size sensor prototypes fully characterized that meet final specs Inter-strip capacitance & resistance, coupling capacitance, depletion voltage, leakage currents and polysilicon resistors qualified See J. Bohm, et. al., Nucl. Inst. Meth. A, Vol. 636 (2011) S104-S110 for details A. Affolder – VERTEX 2011, June 2011, Rust, Austria

ATLAS Strip Sensor Charge Collection
Annealed 80 min at 60 C Unannealed 900V 10:1 Signal-to-Noise 240 MeV Pions K. Hara, et. at., Nucl. Inst. Meth. A, Vol. 636 (2011) S83-S89. Unannealed Miniature devices irradiated to strip barrel fluences with neutrons, pions, protons Charge collection measured with 90Sr b-source S/N greater than 10:1 for strip sensor types with expected noise performance ~ e- short strips, ~ e- long strips See H. Sadrozinski, et.al., Nucl. Inst. Meth. A, doi: /j.nima for details NIEL scaling good after annealing corrections Charge sufficient for pixel layers as long as adequate bias voltage and cooling provided!!! 10:1 Signal-to-Noise Neutrons A. Affolder – VERTEX 2011, June 2011, Rust, Austria

e2v Thick Strip Sensors Prototyping with e2v to make n+-strip in p-type substrate devices in ATLAS strip geometry First submission of miniature sensors (1x1 cm2) only to determine optimal isolation/production parameters So far, no surprises with performance before/after irradiation Currently finalizing masks for axial-only full-size sensor in ATLAS strip geometry Designed to match with both 128 channel ABCn 250 nm ASIC and future 256 channel ABCn 130 nm ASIC A. Affolder – VERTEX 2011, June 2011, Rust, Austria

CMS Joint Strip-Pixel Sensors
Structures Objectives: Pixel Multi-geometry strips Multi-geometry pixel Baby_std Baby_PA Baby_Strixel Diodes Test-structures Add_Baby more rad. hard planar pixel Geometry/ thickness Irradiation/annealing Routing/design Irradiation/annealing/material Design/process/surface Lorentz angle 158 wafers ~ 30 pieces per wafer ~ 5000 pieces A. Affolder – VERTEX 2011, June 2011, Rust, Austria

CMS Joint Strip-Pixel Sensors
n-type p-type (p-stop) p-type (p-spray) FZ320 6 / 6 FZ200 deep diff. FZ120 deep diff. MCz200 physical Epi100 2 / 6 Epi70 4 / 0 - Epi50 FZ200 deep diff. & 2.metal FZ200 physical 0 / 6 0 / 4 FZ120 on carrier 200µm low conc. 120µm high conc. 320µm FZ200 deep diff. “Deep diffused” wafers are about 20% cheaper than 200µm thin wafers Additional material ordered lately and expected Sept./Nov. 158 pieces One vendor – one testing protocol – different technologies Electrical characterization AND signal/noise Irradiation study Irradiate with mixed particle types according to different radii Check long term annealing behavior 500kCHF for material 158 pieces + 200kCH for study A. Affolder – VERTEX 2011, June 2011, Rust, Austria 13

CiS Thick Pixels RD50 Bump bonding to the FE-I3 chips (present ATLAS pixel read-out) performed by IZM-Berlin UBM pads Sensor surface covered with 3 mm of BCB (Benzocyclobutene ®) during post-processing at IZM Berlin higher isolation capabilities with respect to SiO2 Common PPS ATLAS -CMS pixel production within RD50 Stable operation at 1000 V!! FZ p-type material, 285 mm thick Inter-pixel isolation: moderated p-spray homogenous p-spray See A. Macchilo, et.al, “Performance of Silicon n-in-p Pixel Detectors irradiated up to 5x1015 neq /cm2 for the future ATLAS Upgrades ”at TIPP 2011, Chicago, IL A. Affolder – VERTEX 2011, June 2011, Rust, Austria

Micron Thick Pixels 6” wafers, 300 mm thick, fabricated by Micron in the double metal n-in-p FZ Bondable pixels based on FEI3 2048 pixels: by 50µm DC Coupled 8 interleaved pixels per column/row Pixel matrix 16x128 implants Allows for separate irradiation of pixel sensors and readout chips Allows for simpler resolution and charge collection studies Wire bondable pixels FE-I4 FE-I3 Row parallel Column parallel A. Affolder – VERTEX 2011, June 2011, Rust, Austria

MPI-HLL Thin Pixels/Strips
Production characteristics: 8 n-in-p 6“ wafers with ATLAS FE-I3 compatible sensors Different active thicknesses: 75μm and 150μm Pre-irradiation characterization: Excellent device yield (79/80) Low currents (~10 nA /cm2) - Good breakdown behaviour (Vbd >>Vfd) Charge collection measured with thin p-type strip sensors – Alibava read-out system ~7 mm strip sensors with the same structure as the pixels (punch-through biasing, DC coupling) Excellent collected charge after high fluences A. Macchiolo et al. NIMA, doi: /j.nima A. Affolder – VERTEX 2011, June 2011, Rust, Austria

HPK Thin Pixel Sensors n-in-p 6-in. wafer process in HPK ATLAS FE-I3 and FE-I4 pixel sensors Bias: Punth-thru (PT) or PolySi resisters Isolation: p-stop (common, individual) or p-spray Thinning Finished 320 µm wafer thinned to 150 µm Completing the backside FE-I4 2-chip pixels FE-I4 1-chip pixels FE-I3 1-chip pixels FE-I3 4-chip pixels HPK n-in-p 6-in. wafer 1 µA FE-I4 1-chip, FE-I3 4-chip FE-I4 2-chip 1000 V FE-I3 1-chip I-V performance (before UBM and dicing) Most hold up to 1000 V. p-spray sensors earlier breakdown (900 V) A number of FEI4 devices at IZM ready for bump bonding See Y. Unno, et.al, “Latest results in developing n-in-p pixel and microstrip sensors for very high radiation environments”at Pixel 2010 A. Affolder – VERTEX 2011, June 2011, Rust, Austria

Other Thin Pixel Productions
n-in-p, single metal FZ process Micron 6” wafers 140, 300 mm without handle wafer At IZM now for UBM and bump bonding to FEI4 FEI4 SCM FEI4 SCM 2x1 FEI4 2x1 FEI4 FEI4 SCM FEI4 SCM FEI4 SCM FEI4 SCM FEI4 SCM 2x1 FEI4 FEI4 SCM FEI4 SCM 2x1 FEI4 FEI4 SCM FEI4 SCM FEI4 SCM 2x1 FEI4 FEI4 SCM FEI4 SCM New n-in-p pixel production at CiS on 4” wafers Pixel sensors compatible with FE-I4 (new ATLAS chip for IBL and outer layers at HL-LHC) Thinner bulk: 150, 200 & 300 mm (process without handle wafer)  better CCE expected A. Affolder – VERTEX 2011, June 2011, Rust, Austria

LHCb VELO Upgrade Strips Several wafers with various manufacturers CNM/USC : 150μm p-in-n sensors, μm n-in-p sensor single ASICs with future 3x1 ASICs tiles Micron/Liverpool: n-in-p (150 and 300μm thick) VTT: slim edge (active) 50,100μm edge, different GR, μm thick See Abraham Gallas’s talk for details Pixels Sensor Angle (deg) A. Affolder – VERTEX 2011, June 2011, Rust, Austria

Slim Edges Passivated Edge Active Edges Multiplication Enhancement
Back to R&D Slim Edges Passivated Edge Active Edges Multiplication Enhancement

Slim Edges Much work on reducing the inactive edge- Improves efficiency, allows for tiling Above 1000 V Hamamatsu test structures Wafer thickness 320 µm Both N- and P-sub wafers Dependence of square root of Vbias on the distance to edge Linear, reflecting the lateral depletion along the surface Pre-irradiation distance to hold 1000 V is ~ µm The necessary edge width to reach ~1000V reduces with fluence Non-irrad. After irrad. Y.Unno et al. NIMA, doi: /j.nima A. Affolder – VERTEX 2011, June 2011, Rust, Austria

Edge Potential vs. Passivation
n-strip n-strip silicon oxide p-type (20k Wcm) alumina -40 -112 -145 -40 -112 -145 p-type (20k Wcm) Positive charge (+1E11 cm-2) Negative charge (-1E11 cm-2) Oxide passivation leads to: high electric field at trench edge, no control potential drop towards the cut edge. Alumina passivation leads to: high electric field strip edge, partially controlled potential drop towards the cut edge. Collaboration between SCIPP and NRL to passivate sensors with Alumina after laser scribbing and cleaving using atomic layer deposition (ALD) A. Affolder – VERTEX 2011, June 2011, Rust, Austria

Edge Passivation Low leakage up to 1,000 V. 29 mm ATLAS07 Diode (HPK) 14 mm alumina layer Reference cleaved edge diode edge Cleaved 29 mm from single guard ring Cleaved 14 mm from active area (no GR) Initial results really promising New RD50 common project funded for further study See M. Chistophersen, et.al, “ Laser scribing and sidewall passivation of p-type sensors” at 6th Trento Workshop A. Affolder – VERTEX 2011, June 2011, Rust, Austria

Active Edges RD50 Detector thicknesses of 100, 200 mm Support wafer P-stop or p-spray isolation Under bump and flip-chip in-house A. Affolder – VERTEX 2011, June 2011, Rust, Austria

Multiplication Enhancement
RD50 Trench filled with doped polysilicon along the centre of the strip pitch CNM devices with deep implants in order to enhance charge multiplication Polytrench or deep diffusion Devices in hand under evaluation and ready for start of irradiation programme 285µm 80µm n+ p- p+ 32µm 5µm 8µm p-stop poly trench Poly Trench P-type diffusion along the centre of the strip pitch p- p+ 285µm 32µm 80µm 8µm n+ 5µm p-stop p-type diffusion p Diffusion Guard Rings Bias Ring Micron devices to study effects of implant geometry on charge multiplication 100 um, 80 um and 40 um pitch with 3 different implant widths and optional intermediate strips (biased and floating) Pad detectors for further slim edge studies (number of guard rings, GR implant width, via/trench contact) Delivery of first wafers in ~1 month A. Affolder – VERTEX 2011, June 2011, Rust, Austria

Conclusions N-strip readout (n-in-n and n-in-p) planar sensors have a remarkable collected charge after HL-LHC fluences Understood to be a combination of mobility, trapping, active base and charge multiplications A large number of submissions at multiple foundries are in-process to take advantage of this performance Further studies are underway to reduce the inactive edges and to enhance/study the charge multiplication effects A. Affolder – VERTEX 2011, June 2011, Rust, Austria

Backup

LHCb VELO Pixel Upgrade
The new mask should have: VELO tiles (can be 7, my suggestion: 7/wafer), R&D single VELOPix chip (my suggestion 8/wafer, 4 flavours), diodes to fill gaps (can be useful for R&D). A. Affolder – VERTEX 2011, June 2011, Rust, Austria

Edge-TCT 1.5 GHz scope laser 1060 nm 100 ps pulse 200 Hz repetition detectors on Peltier cooled support in dry air atmosphere (down to -20oC) lens system Advantages (compared to pixel test beam – grazing technique): Position of e-h generation can be controlled by 3 sub-micron moving tables (x,y,z) The amount of injected e-h pairs can be controlled by tuning the laser power Easier mounting and handling Not only charge but also induced current is measured – a lot more information Drawbacks: Light injection side has to be polished to sub-micron level to have a good focus – depth resolution It is not possible to study charge sharing due to illumination of all strips Absolute charge measurements are very difficult A. Affolder – VERTEX 2011, June 2011, Rust, Austria

Comparison of Room Temperature and Accelerated Annealing of the collected charge, HPK FZ n-in-p, 1and 1.5E15 n cm-2 (26MeV p irradiation) Accepted acceleration factor Acceleration factor divided by 2.1 A. Affolder – VERTEX 2011, June 2011, Rust, Austria

Leakage current guard rings not bonded Increase of leakage current with annealing  multiplication A. Affolder – VERTEX 2011, June 2011, Rust, Austria

ATLAS Strip Module Irradiation
Irradiated at CERN-PS irradiation facility 24 GeV proton beam scanned over inclined modules Module biased, powered, and clocked during irradiation Total dose of 1.9x1015 neq cm-2 achieved Max predicted fluence for barrel modules is x1015 neq cm-2 Sensor and module behave as expected Noise increase consistent with shot noise expectations AL Foil AL Foil Noise Column 0 Column 1 Pre-Irrad 610 e- 589 e- Post-Irrad 675 e- 650 e- Difference 65 e- 61 e- Expected 670 e- 640 e- Pre-irradiation Post-irradiation Motorized, Cooled Irradiation Stage A. Affolder – VERTEX 2011, June 2011, Rust, Austria

Thickness Comparisons
With same masks and base material (n-in-p FZ) used to make three thicknesses, a clear pattern emerges At low fluences (<5×1014 neqcm-2), “classic” model of VFD, neff and charge trapping holds At higher fluences (3×1015 neqcm-2), “active” base and multiplication are dominant effects 500 V 900 V Shown at 5th Trento Workshop, Manchester, 24th-26th Feb 2010 Paper under review IEEE Trans. Nucl. Sci. Below 5×1014 neqcm-2, charge advantage to being thicker Above 3×1015 neqcm-2, charge advantage to being thinner A. Affolder – VERTEX 2011, June 2011, Rust, Austria

Influence of Surface Charge Concentration: P-Si/Al2O3
1010 cm-2 1011 cm-2 1012 cm-2 p-type (20k Wcm) p-type (20k Wcm) p-type (20k Wcm) -50 -110 -150 -50 -110 -150 -50 -110 -150 increasing negative surface charge Typical literature values for alumina are ~ 1011 – 1013 cm-2 depending on deposition conditions. BUT most research is focused on increasing (not decreasing) surface charge. The potential drop at edge depends strongly on surface charge density. 35

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