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

Electrical tests of ATLAS12A mini sensors UCSC 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 2

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 2 nd neighbor strips are not connected 3

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 Voltage(V) Frequency = 1MHz 4 C(interstrip) [pF/cm]

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 Frequency [kHz] Inter-strip capacitance ( pF/cm) 5 Frequency [kHz]

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

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) Fluence [Neq/cm2] 100kHz 1Mhz Before irradiation 7

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

Inter-strip resistance VS Fluence ( Φ ) R(interstrip) drops significantly after Φ >1e14 ◦ Reduce from G Ω level to M Ω level ◦ R(interstrip) /R(bias) 2e15 ◦ ATLAS Specification R(interstrip) >10*R(bias) R(interstrip) (Ohm) 9 Before irradiation R(interstrip) /R(bias) Fluence [Neq/cm2] Fluence [Neq/cm2]

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 10

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 11 before radiation Φ= 5e15 Resistance(Ohm) Voltage (V) Resistance(Ohm)

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

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

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

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 M Ω level at Φ >2e15 in this result and Prague result (ATLAS12A EC) R(interstip) Drop to M Ω 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: ATLAS12 results by Lancaster: ◦ 15

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/cm 2 ◦ 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 19K Ω /cm, meet ATLAS specification ( < 20 K Ω /cm) 16

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, 17

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

resistance of PTP structure vs. voltage 19 As fluence increase ◦ The resistance of PTP responses slower to voltage ◦ punch-through voltage increased

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