Surface measurements with ATLAS12A

1. Surface measurements with ATLAS12A Matthew Domingo, Hartmut F.-W. Sadrozinski, VitaliyFadeyevZachary Galloway,Zhijun Liang SCIPP, UCSC

2. Electrical tests of ATLAS12A mini sensorsUCSC status • Samples • ATLAS12A samples irradiated with protons at Birmingham by 27MeV protons • Samples have not been annealed yet • 8 fluences : 1e12, 5e12,1e13,1e14,1e15,2e15,5e15 Neq/cm2 • Zones : BZ3C and BZ3F • This talk focus on the following measurements • R(interstrip) • C(interstrip) • PTP • Implant sheet resistance

3. Inter-strip capacitance • C(interstrip) Measurements setups • BZ3C sensors , Measured in -10 °C , before annealed • 5 probe methods: • Middle strip connected to to LCR meters low side • First neighbor strips connected to LCR meters high side. • The Second neighbor strips grounded • 3 probe methods: • Similar to 5 probe methods • Except that the 2nd neighbor strips are not connected

4. C(interstrip) before irradiation • ATLAS07 and ATLAS12 have similar C(interstrip) • 3 probe measurement are ~15% higher wrt 5 probe methods • due to second neighbor contribution C(interstrip) [pF/cm] Frequency = 1MHz Voltage(V)

5. Inter-strip capacitance VS frequency • Measured BZ3C sensors by 3 probe method at -10 °C • We test Frequency range from 50kHz to 2MHz. • Low frequency region has a higher variance. • Frequency dependence is reduced when Frequency >500kHz Inter-strip capacitance ( pF/cm) Inter-strip capacitance ( pF/cm) Frequency [kHz] Frequency [kHz]

6. Bias Voltage dependence • Inter-strip capacitance shows a stronger voltage dependence at low frequency (i.e. 100kHz) Inter-strip capacitance ( pF/cm) Inter-strip capacitance ( pF/cm) 1MHz 100kHz Bias voltage(V) Bias voltage(V)

7. Inter-strip capacitance VS Fluence • Main result: Less impact by radiation in high frequency region • Inter-strip capacitance varied by 15% In high frequency region (>500kHz) for most of samples • One outliner varyied by 50% at Fluence =1e14. • Inter-strip capacitance In low frequency region (eg. 100kHz) is not stable • Measured by 3 probe method with 300 V reserve bias at -10 °C Inter-strip capacitance ( pF/cm) Before irradiation 100kHz 1Mhz • Fluence [Neq/cm2]

8. Inter-strip resistance • The inter-strip resistance setup as follow • BZ3C sensors • Measured at -10 °C Measure nA current for GΩlevel resistance Relative low S/N Do a careful job in grouding to reduce the noise

9. Inter-strip resistance VS Fluence (Φ) • R(interstrip) drops significantly after Φ>1e14 • Reduce from GΩlevel to MΩ level • R(interstrip) /R(bias) <10, when Φ>2e15 • ATLAS Specification R(interstrip) >10*R(bias) Before irradiation R(interstrip) /R(bias) • R(interstrip) (Ohm) • Fluence [Neq/cm2] • Fluence [Neq/cm2]

10. PTP measurements • Measure resistance of PTP structure vs. voltage on implant (DC pad) • Measure punch-through voltage after irradiation • Compare the different PTP structure • Mainly the BZ3C and BZ3F

11. BZ3C VS BZ3F • BZ3C has a smaller punch-through voltage before radiation. • After radiation, both sensors have similar punch-through voltage • BZ3F have a higher asymptotic resistance before radiation Φ=5e15 Resistance(Ohm) Resistance(Ohm) Voltage (V) Voltage (V)

12. resistance of PTP structure vs. voltage • As fluenceincrease • The resistance of PTP responses slower to voltage • punch-through voltage increased BZ3F Resistance(Ohm) Resistance(Ohm) BZ3C Voltage (V) Voltage (V)

13. punch-through voltage VS Fluence • Punch-through voltage (V) BZ3C BZ3F • Fluence [Neq/cm2]

14. Implant sheet resistance • Measurement of sheet resistance of n-implant • ATLAS specification: Implant resistance < 20 KΩ/cm • Measured resistance per strip ~ 19KΩ/cm • Uniform in all the strips • No dependence of bias voltage Implant resistance (KΩ/cm) Implant resistance (KΩ/cm) Bias voltage(V) Strip number

15. ATLAS12A VS ATLAS12A endcap • The results of ATLAS12A compared to “ATLAS12” and “ATLAS12A endcap” • See strong drop of R(interstip) with fluence increase as others sensors • R(interstip) Drop to MΩ level at Φ>2e15 in this result and Prague result (ATLAS12A EC) • R(interstip) Drop to MΩ level at Φ>1e15 in Lancaster measurement(ATLAS12A) • See need to see higher frequencies for C(interstip) measurements • At 100kHz, see larger Variation (>100%) • Larger than Lancaster result (ATLAS12A) (20%) and Prague result (ATLAS12A EC)“ (~50%) • At 1MHz, See similar variation (20%) with fluence as other measurements • “ATLAS12A endcap” results by Prague group: • https://indico.cern.ch/event/312262/contribution/6/material/slides/0.pdf • ATLAS12 results by Lancaster: • https://indico.cern.ch/event/292247/contribution/12/material/slides/1.pdf

16. Summary • ATLAS12A mini sensors irradiated by protons are measured. • Inter-strip capacitance in irradiated samples • Increased by one order of magnitude at low frequency (100k) • Increased by 10~20 % at high frequency • ATLAS Specification < 0.8 pF/cm at 100kHz • does not meet the specification at 100kHz When fluences >1e13 • Very close to meet the Specification (0.8 pF/cm) at 1MHz • May revise the specification • if the S/N is still large once we know ABCN130 performance • Inter-strip resistance • ATLAS Specification R_INT>10*R(bias) • Accorinding to Specification interstrip resistance is not sufficient after fluences >2e15 Neq/cm2 • After Φ>5e15, R_INT is about 0.3MOhm • Still larger than the amplifier's input impedance (kOhm) • PTP • There is no defined acceptance criterion in ATLAS Specification • BZ3C and BZ3F samples are measured. • PTP performances are acceptable at all fluences • Implant resistance • 19KΩ/cm, meet ATLAS specification (< 20 KΩ/cm)

17. Next steps • Test BNL gamma radiated sensors • Compare protons radiation VS gamma radiation damage • Starting on laser-based dynamic PTP study • Aim to report the results in next meeting • Will work on sensors performance after annealing,

18. Backup R(bias) • Fluence [Neq/cm2]

19. resistance of PTP structure vs. voltage • As fluenceincrease • The resistance of PTP responses slower to voltage • punch-through voltage increased

20. Backup: Bias Voltage dependence • Inter-strip capacitance shows a stronger voltage dependence at low frequency (i.e. 100kHz) Inter-strip capacitance ( pF/cm) Inter-strip capacitance ( pF/cm) 1MHz 100kHz Bias voltage(V) Bias voltage(V)