Total Dose Dependence of Oxide Charge, Interstrip Capacitance and Breakdown Behavior of sLHC Prototype Silicon Strip Detectors and Test Structures of the SMART Collaboration H. F.-W. Sadrozinski, C. Betancourt, R. Heffern, I. Henderson, J. Pixley, A. Polyakov, M. Wilder SCIPP, UC Santa Cruz M. Boscardin, C. Piemonte, A. Pozza, S. Ronchin, N. Zorzi ITC-irs G.-F. Dalla Betta DIT, Università di Trento M. Bruzzi Dipt. Energetica, Univ. of Florence A. Macchiolo INFN Florence L. Borello, A. Messineo INFN Pisa Donato Creanza INFN Bari
Structures Investigated Type Dimension Measurements Frequency MOS Capacitor Circular Area C-V 10 kHz =3.14mm 2 Capacitance TS Length = 1.15 cm Cint-V ~ 1 MHz Pitch = 50, 100 um C-V 10 kHz Implant = 15, 25 um i-V n.a. Poly width = 10 um Metal = 23, 33 um SSD Length = 4.46 cm Cint-V ~ 1 MHz Pitch = 50, 100 um C-V 10 kHz Implant = various i-V n.a.
Wafers Investigated Wafer Wafer # Thickness P-spray Dose SSD / TS / MOS [cm -2 ] Type [um] n FZ W1254 n.a. TS, MOS 5*10 12 p FZ W084 200 TS, MOS 3*10 12 p FZ W014 200 SSD 5*10 12 p FZ W037 200 SSD 3*10 12 , p MCz W044 300 TS, MOS no passivation 5*10 12 , p MCz W253 300 TS, MOS no passivation 3*10 12 , p MCz W066 300 SSD no passivation 5*10 12 , p MCz W182 300 SSD no passivation
SSD Investigated SSD Substrate P-spray Pitch # Implant Poly Metal ( μ m) Dose strips Width Width Width [cm -2 ] . ( μ m) ( μ m) ( μ m) 3*10 12 14-5 FZ 200 50 64 15 10 27 3*10 12 14-8 FZ 200 100 32 35 30 43 5*10 12 37-5 FZ 200 50 64 15 10 27 5*10 12 37-8 FZ 200 100 32 35 30 43 3*10 12 66-8 MCz 100 32 35 30 43 5*10 12 182-5 MCz 50 64 15 10 27 5*10 12 182-8 MCz 100 32 35 30 43
Device Preparation and Irradiation UCSC 60 Co source 3.15 kRad/hr SSD (W037) vs. Test structure (W084 R 3-4) 10 9 TS Un-bonded and unbiased W084 50 um Cint for 1.16 cm [pF] 8 37.pre-rad except to shield 7 w084 50 um bonded 6 Mini-SSD bonded to shield. 5 4 3 Ratio between 2 mini-SSD and T.S. =1.2 1 0 (3 pairs vs. 1 pair) 0 20 40 60 Bias Voltage [V] T.S. Pre-rad: Shield Bonded/Not bonded (W253 210 krad) Large difference between 5 W253 L 3-4 NOT bonded 100 um shield bonded and un-bonded w253 L 5-6 bonded 100um 4 W253 L 3-4 NOT bonded 50 um W253 L 5-6 bonded 50 um W253 L 3-4 NOT bonded 50 um 3 Cint [pF] W253 L 5-6 bonded 50 um T.S. Post-rad: No difference between 2 shield bonded and un-bonded 1 0 Expect substantial annealing 0 100 200 300 400 500 600 700 Bias Voltage [V] with unbiased devices.
MOS Cap � Doping Density Nd, Flatband Voltage FBV, Oxide Charge Qox MOS C-V p high-dose p-spray MCz W253 T1-1 136 134 FBV = 3V Capaictance [pF] Qox = 1*10 11 132 FBV = 65 V 130 Qox = 1*10 12 128 pre-rad 126 210 kRad 124 -100 -50 0 50 100 150 Bias Voltage [V]
Flatband Voltage FBV vs. Dose FB Voltage W084 T1-2&T1-6 p FZ HPD FB Voltage W253 T1-1 & T1-7 p Mcz H DP 80 80 60 60 FB Volatge [V] FB Volatge [V] 40 40 W 253 T1-1 20 20 W084-T1-2 W 253 T1-7 W084-T1-6 0 0 0 200 400 600 800 0 200 400 600 800 Dose [kRad] Dose [kRad] FB Voltage W044 p MCz LPD FB Voltage W1254 T1-8 n FZ 150 80 W044-T1-7 60 W044-T2-4 FB Volatge [V] 100 FB Volatge [V] W044-T1-3 40 W044-T3-2 W044-T3-2 50 W044-T2-1 20 W044-T3-1 0 0 0 100 200 300 400 500 600 700 800 0 100 200 300 400 500 600 700 800 Dose [kRad] Dose [kRad]
Oxide Charge Qox vs. Dose Qox W084 T1-2 & T1-6 p FZ HPD Qox W253 T1-1 & T1-7 p Mcz HDP 2.0E+12 2.0E+12 1.5E+12 1.5E+12 Qox Qox 1.0E+12 1.0E+12 5.0E+11 5.0E+11 W253 T-1 W084 T1-2 W253 T1-7 W084 T1-6 0.0E+00 0.0E+00 0 200 400 600 800 0 200 400 600 800 Dose [kRad] Dose [kRad] Qox W044 p MCz LPD Qox W1254 T1-8 n FZ 3.0E+12 2.00E+12 W044-T1-7 1.50E+12 W044-T2-4 2.0E+12 Doping Conc W044-T1-3 Qox 1.00E+12 W044-T3-2 W044-T3-2 1.0E+12 W044-T2-1 5.00E+11 W044-T3-1 0.00E+00 0.0E+00 0 100 200 300 400 500 600 700 800 0 200 400 600 800 Dose [kRad] Dose [kRad]
Mini-SSD and Cap T.S.: Breakdown Voltage, Leakage current, Cint vs. Dose High dose p-spray breaks down much easier
Mini-SSD and Cap T.S.: Breakdown Voltage, Leakage current, Cint vs. Dose Voltage Range 1: region between col. is not fully depleted ⇒ large capacitance full dep. between columns ~ 7V Voltage Range 2: region between col. is fully depleted ⇒ depletion proceeds only towards the back (almost like a planar diode) full depletion ~200V depletion width of ~350 µ m
Mini-SSD and Cap T.S.: Breakdown Voltage, Leakage current, Cint vs. Dose 4 Current @ Depletion vs. Dose 3.5 y = 0.0068x + 0.7384 y = 0.0028x + 2.3838 3 I @ V_depletion (uA) y = 0.006x + 0.7653 2.5 2 y = 0.0026x + 1.1778 1.5 14-8 37-8 66-8 1 182-8 Linear (37-8) Linear (66-8) 0.5 Linear (182-8) Linear (14-8) 0 0 50 100 150 200 250 300 350 400 Dose (Krads) The current damage constant is independent of the wafer type, but is a factor two larger for low spray dose (wafer 14 and 66) than for high spray-dose (wafer 37 and 182).
Cint pre-rad and after saturation (4.45 cm mini-SSD, 100 µ m pitch) Wafers 14 and 37 are FZ, wafers 66 and 182 MCz. Little difference between different wafers, large dependence on the p-spray.
Cint vs. Dose(1.16 cm T.S.) p FZ high W084 TS_R1-2 50um p MCz high W253 TS L 3-4 50um 12,13,14 4 4 pre-rad12, 13, 14 70 kRad 70 kRad 12,13,14 210 kRad 140 kRad 12,13,14 3 3 305 kRad 280 kRad 12,13,14 305 kRad + 3 days Cint [pF] pre-rad( 4,5,6 Cint [pF] 2 2 1 1 0 0 0 -100 -200 -300 -400 -500 -600 -700 0 -100 -200 -300 -400 -500 -600 -700 Bias Voltage [V] Bias Voltage [V] p MCz low W044 TS L1 50um n FZ W1254 TS R 5-6 50um 4,5,6 4 4 0kRad pre-rad 140 kRad 3 3 73 kRad 270 kRad 139 kRad Cint [pF] 210 kRad Cint [pF] 2 2 285 kRad 1 1 0 0 0 100 200 300 400 500 600 700 0 -100 -200 -300 -400 -500 -600 -700 Bias Voltage [V] Bias Voltage [V] Little dependence of wafer type, i.e. MCz and FZ behave the same, but dependence on p-spray dose. Ntype increases with dose.
Conclusion Conclusion MCz and FZ behave similar, Large dependence on p-spray dose.
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