AD vanced MO nolithic S ensors for Radiation hardness of fully depleted CMOS Monolithic Active Pixel Sensors Tobias Bus, Benjamin Linnik, Michael Deveaux
MAPS – Monolithic Active Pixel Sensors MimoSIS design goals: MIMOSIS – Expected performance The CBM-MVD CMOS Process Tower/Jazz 0.18 µm Quad-Well Pixel dimensions 30.1 x 26.9 µm² Spatial resolution ~ 5µm Material budget 50 µm Si (0.05 % X 0 ) Radiation tolerance > 3Mrad (@-20°C). > 3x10 13 n eq /cm² T. Bus, DPG 2017, Münster 2
MAPS – Monolithic Active Pixel Sensors +3.3V Reset +3.3V Output SiO 2 SiO 2 SiO 2 N++ N++ N+ P+ P- 50µm 15µm P+ T. Bus, DPG 2017, Münster 3
Effects of non-ionizing radiation Readout Readout Trapping & recombination of signal electrons Diode Leakage current → higher noise Cooling decreases this effect e- e- e- Detecting layer Particle Defects due to radiation Depleting the sensor allows to accelerate the charge collection. => More radiation tolerance. T. Bus, DPG 2017, Münster 4
Pipper – 2: A fully depleted HR-MAPS Standard pixel Issue: Vdiode Standard CMOS restricted to few volts bias => Too few for full depletion. Analysis: Collecting diode Restriction due to transistor gates. read Diodes and metal lines tolerate higher voltages. Column Pipper - 2 OUTPUT Vdiode Approach: bias Use AC-couping to separate vulnerable transistors from HV on diode. ⇒ Depletion voltage up to 40V possible. Collecting diode read Apply to 22x22 µm 2 pixels. Column OUTPUT T. Bus, DPG 2017, Münster 5
Standard sensor – Test results Fe-55 2200 2000 Not irradiated 13 neq/cm 2 Irradiated with 10 1800 1600 Depleted volume 1400 Epi-layer 1200 Epi-layer 1000 800 Depleted volume 600 400 200 0 0 200 400 600 800 1000 1200 1400 1600 1800 2000 Standard sensor – Only few hits from depleted volume. Other hits: Reduced amplitude (charge sharing). T. Bus, DPG 2017, Münster 6
Pipper – 2 – Test results 6000 5 V 10 V 5000 20 V 30 V 40 V 4000 3000 2000 1000 0 50 100 150 200 250 300 Hits mostly in depleted volume peak. No modification for >20V => indicator for full depletion T. Bus, DPG 2017, Münster 7
Vllt keine zeit dafür? Standard sensor Epi-layer Depleted volume 20V Pipper - 2 Depleted volume T. Bus, DPG 2017, Münster 8
Test with 90 Sr beta rays 2 220 e 1e13 n eq /cm 860e 2 5e14 n eq /cm 10000 Sr90 β -source detection eff. 109±10% 1000 1290e S/N=31.3 S/N=55.6 100 10 1 100 1000 10000 S/N (Sr-90) >15 typically > 99% MIP - efficiency T = -55° C Signal MPV (e) Avg. noise (e) S/N 10 13 n eq /cm 2 1290 23.19 55.6 5 · 10 14 n eq /cm 2 860 27.48 31.3 T. Bus, DPG 2017, Münster 9
Summary and conclusion Radiation tolerance (MIMOSA-series) This work A CMOS sensor allowing for 40V depletion voltage in Tower/Jazz 0.18µm has been built and tested. Results suggest full depletion. Laboratory tests suggest tolerance to >5 x 10 14 n eq /cm². (Remaining S/N>30 if cooled). T. Bus, DPG 2017, Münster 10
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