Update on tests with passive strucutres on CHESS

Update on tests with passive strucutres on CHESS 2 chip ATLAS Strip CMOS meeting, 20. 12. 2016 Bojan Hiti, Igor Mandić et al. Jožef Stefan Institute, Experimental Particle Physics Department (F 9) Ljubljana, Slovenia Bojan Hiti (IJS)

Bojan Hiti (IJS) CHESS 2 passive structures 16. 9. 2020 2

Samples Chips from wafer 1: standard AMS resistivity (20 Ohm-cm, n in p) Neutron fluences 0 e 14, 1 e 14, 3 e 14, 5 e 14, 1 e 15, 2 e 15 neq/cm 2 Test structures: • 3 x 3 pixel array for E-TCT (pixel size 630 x 40 μm 2) • Large array for Sr 90 measurements (1. 2 x 1. 2 mm 2) Bojan Hiti (IJS) CHESS 2 passive structures 16. 9. 2020 3

I-V characteristic I-V measured on a TCT array (3 x 3 pixels, pixel size 630 x 40 μm 2) Bojan Hiti (IJS) CHESS 2 passive structures 16. 9. 2020 4

E-TCT Charge collection profiles W 1 Preliminary! depth surface ● ● Moderate charge collection width, but increases with irradiation Low resistivity late acceptor removal Bojan Hiti (IJS) CHESS 2 passive structures 16. 9. 2020 5

Charge collection width vs. fluence Preliminary! 20 Ohm-cm : late acceptor removal, largest charge collection region at highest measured fluences Bojan Hiti (IJS) Extract value from fit CHESS 2 passive structures 16. 9. 2020 6

Neff vs. fluence Fit: Radiation introduced deep acceptors acceptor removal Preliminary! Fit results: initial resistivity: 20 Ω cm Nc/Neff ≈ 1 c = 0. 18 e 14 cm 2 Gc = 0. 02 cm-1 (fixed) Bojan Hiti (IJS) CHESS 2 passive structures 16. 9. 2020 7

Neff vs. fluence Preliminary! Removal at the highest resistivity substrate is completed below 1 e 14 neq/cm 2 and was not observed in this study should verify again Bojan Hiti (IJS) CHESS 2 passive structures 16. 9. 2020 8

Acceptor removal constant vs. doping c [cm 2] LFoundry G. Kramberger et al, 10 th Trento Meeting, Feb. 17 -19, 2015 X-FAB, neutrons AMS CHESS 1, PS protons AMS CHESS 1, neutrons AMS CHESS 2 Bojan Hiti (IJS) Blue marker – charged hadron irradiated Red marker – neutron irradiated CHESS 2 passive structures 16. 9. 2020 9

Sr 90 measurements Collected charge is less than expected from E-TCT measurements But is that really the case ? Calibration of the Q-TCT setup was carried out, discussion on next slides Bojan Hiti (IJS) CHESS 2 passive structures 16. 9. 2020 10

Q-TCT calibration 1 Sr 90 calibration procedure • using epitaxial diodes with known thickness (d = 50 and 100 μm) • after epi-layer is fully depleted extract scaling factor A = d x 100 pairs/μm / Vsig Only n-type diodes could be biased highly enough for calibration p-type breaks down at 60 V, before full depletion Bojan Hiti (IJS) CHESS 2 passive structures 16. 9. 2020 11

Q-TCT calibration 2 Results: calibration factor in the same range as used up to now A = 275 000 pairs / V, but the signals for unirradiated CHESS 2 devices are actually what we would expect only irradiated CHESS 2 devices have less charge than expected: * Depleted depth for CHESS 2 is determined from the formula: Bojan Hiti (IJS) CHESS 2 passive structures 16. 9. 2020 12

Sr 90 Comparison for different substrates Preliminary! CHESS 1 vs. CHESS 2 (std. resistivity) : trend is similar, but mean charge differs Could be due to a different wafer composition different acceptor removal Bojan Hiti (IJS) CHESS 2 passive structures 16. 9. 2020 13

Top TCT ● ● Charge from Sr 90 measurements systematically only 60 % of that expected for the depletion depth measured by E-TCT Investigate with top TCT ● IR light – 980 nm, abs. depth 100 μm no reflections from back plane W 19 5 e 14 Big array for Sr 90 (1. 2 mm x 1. 2 mm) Gaps between pixels due to metalization on top of the chip But on the large scale intensity in central pixels less than on edges ! Bojan Hiti (IJS) CHESS 2 passive structures 16. 9. 2020 14

Top TCT 2 Difference in the collected charge indicates a larger depletion depth on the edges of the Sr 90 array. Edge-like pixels also measured in Edge-TCT. This may be a reason for discrepancy between the measurements. W 19 5 e 14 Bojan Hiti (IJS) CHESS 2 passive structures 16. 9. 2020 15

Top TCT 3 Similar behavior observed also on the sample W 19 3 e 14 Bojan Hiti (IJS) CHESS 2 passive structures 16. 9. 2020 16

Summary ● Completed measurements of charge collection on passive structures on CHESS 2 ● ● ● E-TCT: ● ● ● Mean collected charge at least 1000 electrons for any substrate and fluence Systematic discrepancy between E-TCT and Sr 90 in collected vs. expected charge ● ● Behavior of different wafers as expected from previous studies with different substrates Acceptor removal affects depleted depth after irradiation Sr 90 ● ● 4 wafer resistivities 20 – 2000 Ohm-cm, each wafer 6 neutron fluences up to 2 e 15 n/cm 2 E-TCT and Sr 90 Indications that pixels in a large array collect less charge than pixels with only few neighbors Observed only after irradiation Outlook: Tests with active analog structures AOI: Monday is the desired date for X-Fab paper submission – please corrections by then Bojan Hiti (IJS) CHESS 2 passive structures 16. 9. 2020 17

BACKUP Bojan Hiti (IJS) CHESS 2 passive structures 16. 9. 2020 18

Passive structures on CHESS 2 Red traces - metalization Bojan Hiti (IJS) CHESS 2 passive structures 16. 9. 2020 19

W 19 I-V curves Bojan Hiti (IJS) CHESS 2 passive structures 16. 9. 2020 20

Depletion depth W 19 Preliminary! ● Bojan Hiti (IJS) Sqrt functions falling monotonously with fluence CHESS 2 passive structures 16. 9. 2020 21

Sr 90 charge Preliminary! ● ● ● TCT 1 e 14: depletion zone 120 um at 100 V We still collect less charge than expected (f. e. meas. 7000 e vs. 12000 e expected) Investigate with top TCT ? Bojan Hiti (IJS) CHESS 2 passive structures 16. 9. 2020 22

Sr 90 spectra W 19 1 e 14 100 V – Noise – Signal • Relatively good separation between signal and noise • No peak around 0 in signal spectrum misalignment does not seem to be the main factor for smaller charge Bojan Hiti (IJS) CHESS 2 passive structures 3 e 14 100 V – Noise – Signal 16. 9. 2020 23

Charge profiles W 7, W 13 • Edge-TCT charge collection profile across central pixel W 7 (50 W∙cm) W 13 (200 W∙cm) • increase of width with fluence up to 1 e 15 Bojan Hiti (IJS) • not much change of profile width with fluence CHESS 2 passive structures 16. 9. 2020 24

REMINDER Depletion depth W 7, W 13 • width of charge collection profile vs. bias W 7 (50 W∙cm) W 13 (200 W∙cm) Preliminary Fit: At Ф = 0 • W 7: Neff = 2. 3 e 14 cm-3 • W 13: Neff = 6. 6 e 13 cm-3 56 W∙cm 200 W∙cm Good fit, good agreement with nominal resistivity Bojan Hiti (IJS) CHESS 2 passive structures 16. 9. 2020 25

REMINDER Sr 90 W 7, W 13 W 7 (50 W∙cm) Preliminary! W 13 (200 W∙cm) Preliminary! • large drop of collected charge (delta ≈ 1300 el) after first irradiation step to 1 e 14 n/cm 2 reduced contribution from diffusion • TCT measurements indicate depleted region > 50 μm • Expect > 5000 el. from drift • Measure 2000 el. Bojan Hiti (IJS) CHESS 2 passive structures 16. 9. 2020 26

IV-curves wafer 13 No IV curves for wafer 7 due to a bug, but 0 e 14, 1 e 15, 2 e 15 OK up to 120 V 5 e 14 up to 110 V, 3 e 14 at least up to 90 V Bojan Hiti (IJS) CHESS 2 passive structures 16. 9. 2020 27

High resistivity wafers ● After suggestion from Santa Cruz tried biasing the substrate from other pads: ● ● a&d a&b c&d c&b breakdown at 18 V breakdown at 1 V a c d Bojan Hiti (IJS) Planning also to measure IV of irradiated devices on probe station to see if there is improvement after irradiation b a – LPA nwells b – LPA substrate c – Large Pad nwells d – Large Pad substrate CHESS 2 passive structures 16. 9. 2020 28

Profiles W 19 1 e 14 Bojan Hiti (IJS) CHESS 2 passive structures 16. 9. 2020 29

Profiles W 19 3 e 14 Bojan Hiti (IJS) CHESS 2 passive structures 16. 9. 2020 30

Profiles W 19 5 e 14 Bojan Hiti (IJS) CHESS 2 passive structures 16. 9. 2020 31

Profiles W 19 1 e 15 Bojan Hiti (IJS) CHESS 2 passive structures 16. 9. 2020 32

Profiles W 19 2 e 15 Bojan Hiti (IJS) CHESS 2 passive structures 16. 9. 2020 33