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This paper presents the development of advanced CMOS pixel sensors for radiation detection and imaging, with innovative architectures such as WIPS and SHARPS. The sensors demonstrate satisfactory response to different radiation stimuli and promising performance in terms of SNR. Further testing and analysis are ongoing to characterize the sensors and explore their potential applications.
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MAPS with advanced on-pixel processing D. Biagetti (1, 2), G.M. Bilei(1) , P. Ciampolini(1,3), P. Delfanti(1, 3), A. Marras(1,3), G. Matrella(1, 3), D. Passeri(1, 2), P. Placidi(1, 2), M. Petasecca(1, 2), L. Servoli(1) (1) Istituto Nazionale di Fisica Nucleare Sezione di Perugia – Italy (2) Dipartimento di Ingegneria Elettronica e dell’Informazione Università degli Studi di Perugia - Italy (3) Dipartimento di Ingegneria dell’Informazione Università di Parma - Italy
Outline • APS: • ray • particle • particle • innovative architectures • WIPS • SHARPS • in-pixel CDS
RAPS01 prototype RAPS 01 – 02 UMC 0.18 mm technology Digitally configurable photodiode bias point and decision threshold level RAPS02 prototype 4-14m 10.3m APS architecture WIPS architecture SHARPS architecture
APS: -ray detection • Source • Americium 241 • -ray : 60 keV 12-21 keV
APS: -particle detection single α hit causes cluster response > 30 pixels involved Source Americium 241 -particle : 5.4 MeV
APS: -particle detection Source Strontium 90 -particle : 0.546 MeV
Volt Test results Cluster signal distibution for 90Sr ( ) source. Cluster signal distibution for 141Am ( ) source. Volt MPV evaluated to be equivalent to about 20 MIPs
450 20 SNR > 19 MIP 1.16 Noise measurements -particle response (MPV evaluated to be equivalent to 15-20 IPs) 450 mV pixel (kTC) noise 1.16mV No SEU malfunction were reported
Photodiode ~tens of mV ~tens of nsec Pixel VDD RESET FTD OUT Particle 3D physical simulation (device/circuit)
Configurable amplification Source IR laser=875nm analog amplification photodiode
Configurable amplification Source IR laser=875nm photodiode digital amplification
α-particle detection “analog” readout mode single α hit causes cluster response > 30 pixels involved 300-400mV “digital” (on/off) readout mode cluster size limited to 4-9 pixels 1.6V
Innovative architectures: goals APS • source follower: low in-pixel amplification factor • 1 output pin per pixel: limits on scalability • sequential scan: limits on readout frequency Proposed solutions • exploit CMOS features to achieve a more efficient in-pixel amplification • x-y readout • event-triggered readout
BASIC IDEA column weakly inverted MOS VTH row Innovative architectures: WIPS
MIP simulated response Innovative architectures: WIPS uniform exposition to 976.2 nm, 1.41 W/mm2 laser source 10.3 mm pmos nwell: parassite charge collection risk weakly inverted MOS: power dissipation (20 W / pixel) x-y read-out approach may reduce read-out times by a (m +n )/(m xn) factor in a (m xn) array
BASIC IDEA column self reset A/D high-gain amplification stage row A/D Innovative architectures: SHARPS internal A/D conversion
offset from photodiode center Innovative architectures: SHARPS 10.3 mm MIP simulated response fill-factor15.08% power dissipation 823 nW / pixel Capable of both synchronous and x-y event-triggered readout Resolution: 2.6 m
GND delayed self reset VDD fast self reset A/D A/D A/D A/D A/D A/D A/D A/D A/D A/D Innovative architectures: SHARPS event triggered mode sequential scan mode
BASIC IDEA reset read CDS column output high ampl. 10.3 mm Innovative architectures: CDS in pixel on-pixel Correlated Double Sampling circuitry
CDS signal integration period VREF reset VREF RESET gnd VSIG SAMPLE VREF reference sampling signal sampling gnd VSIG VSIG VREF VSIG VSIG -VREF VSIG -VREF gnd Innovative architectures: CDS in pixel
Conclusions • Active Pixel Sensor systems have been designed and fabricated in a commercial 0.18 m CMOS technology. • TCAD tools thoroughly exploited in the design phase. • Preliminary test results: • satisfactory response to , , , X, IR stimuli • promising performance (SNR). • Innovative architectures introduced. • Extensive test to be completed: • statistical characterization; • dynamic performance; • radiation damage analysis; • beam test. • Next generation chip