Design and Characterization of a Novel, Radiation-Resistant Active Pixel Sensor in a Standard 0.25 m CMOS Technology P.P. Allport, G. Casse, A. Evans, M. Tyndel, R. Turchetta, J.J. Velthuis, G. Villani

CMOS APS detectors: principle & characteristics Outline CMOS APS detectors: principle & characteristics Novel CMOS detector structure HEPAPS3 Conclusions

readout control MAPS CMOS detectors Column parallel ADC 3 MOS APS structure Data processing -out stage Detector and readout integrated onto the same substrate

CMOS detectors for HEP Nwell Pwell Pepi P++ - - Pepi + - P++ Internal electric field 3D view Vbias = 2V applied to N+ Well Generated charge diffuses through epitaxial layer and substrate until recombines or gets collected by cathode 30 ns Transient Electron Current

CMOS detectors for HEP-Charge collection and response time epi subs Reference : HEPAPS2 0.25 μm CIS TSMC Simulated ∆v in-cell Tests results ∆v in-cell

CMOS detectors for HEP-Radiation Hardness T = 300 K T = 253 K No RAD RAD 1014 J. Velthuis University of Liverpool Example of simulation radiation degradation @ to bulk damage Ф = 1014 24GeV p Example of S/N calculation under Hard Reset assumption Vbias = 2V HEPAPS2 0.25 μm CIS TSMC Test results S/N ratio vs number of pixels Charge collected mainly by diffusion: Radiation Bulk damage seriously impacts onto charge collection efficiency

Novel CMOS structure for HEP Deep N Well process allows electric field to be introduced into active region Deep N Well Cell structure comparison Internal electric field plot N P epi subs

Deep N Well Epi collected charge HEPAPS DNW-Epi simulation conditions: Vbias = 2V Cstray = 2 fF Tint = 20 ns 3x3 Cells ( size 15x15 m) HEPAPS DNW-Epi Heavy Ion MIP Simulation Results: Collection time max: 8 nS <Collected charge> (Ф = 0) = 261 e- <Voltage Drop> (Ф = 0) = 1.8 mV Leakage Current (Ф = 0 ) 65 fA Capacitance ( Ф = 0 ) 22 fF Ilk vs. bias voltage Capacitance vs. bias voltage

Radiation Hardness and Signal to noise ratio comparison Deep N Well Epi Example of S/N calculation HR Vbias = 2 APS2 0.25 μm DNW 8 m Epitaxial layer TSMC MS No RAD RAD 1014 HEPAPS2 Example of S/N calculation HR Vbias = 2 APS2 0.25 μm 8 m Epitaxial layer TSMC CIS

HEPAPS3 Deep N Well N P subs HEPAPS3: No Epitaxial layer, Lowly Doped Substrate TSMC MS Slower collection Higher spread Charge collected much dependent on diffusion in undepleted substrate HEPAPS3 Simulation Results: Collection time max: 14 nS <Collected charge> (Ф = 0) = 338 e- <Voltage Drop> (Ф = 0) = 1.9 mV Leakage Current (Ф = 0 ) 65 fA Capacitance ( Ф = 0 ) 26 fF TSMC MS 0.25 m No epitaxial layer Different flavors on chip

HEPAPS3 test results J. Velthuis University of Liverpool HEPAPS3: example of noise signal distribution DNW HEPAPS3: No Epitaxial layer Lowly Doped Substrate TSMC MS Large signal Huge cluster size( charge diffusion trough undepleted substrate) HEPAPS3: example of cluster signal distribution DNW 106Ru source HEPAPS3: example of cluster in S/N 106Ru source

Conclusions Topology optimization of MAPS still ongoing, but future HEP experiments call for uncompromisingly high radiation resistant structures Deep N Well with Epitaxial layer introduces drift component in collection charge process HEPAPS3 preliminary tests results and simulations suggest Deep N Well process with epitaxial layer might show good performances at high level of radiation Synergy between new design topologies and Deep N Well process required to fully exploit the potential benefits

HEPAPS2 simulation 4 Diodes version Cell structure Simulation shows better charge collection at 1014 Irradiation Tests ongoing