SURVEY OF RECENT RADIATION DAMGE STUDIES AT HAMBURG

Transcription

1 SURVEY OF RECENT RADIATION DAMGE STUDIES AT HAMBURG E. Fretwurst 1, D. Contarato 1, F. Hönniger 1, G. Kramberger 2 G. Lindström 1, I. Pintilie 1,3, A. Schramm 1, J. Stahl 1 1 Institute for Experimental Physics, Univ. of Hamburg 2 DESY-Hamburg 3. National Institute for Material Physics, Bucharest Material under investigation Irradiation experiments Recent results - overview Further developments

2 Material under Investigation FZ-Silicon: Wacker Siltronic <111>, n/p, 2-5 kωcm, 285±1 µm, double sided polished process CiS only standard Oxidation and DOFZ: 24,48,72 h/115 C <1>, n/p, 1-6 kωcm, 28±15 µm, double sided polished 8 different types standard Oxidation and DOFZ: 24,48,72 h/115 C Wacker Siltronic process CiS only <111>, n/p, 4-8 kωcm, 3 µm, single sided polished standard Oxidation and DOFZ: 72 h/115 C SINTEF/CiS <111>, n/p, 4-8 kωcm, 3 µm, single sided polished Oxide+DOFZ at SINTEF: standard Oxidation and DOFZ: 72 h/115 C 4 different types All other processing at CiS Cz-Silicon: Sumitomo-Sitix 2 different types EPI-Silicon: ITME <1>, n/p, > 6 Ωcm, 28 ±15 µm, double sided polished, CiS process ITME: TD-kill process, Hamburg: TD-generation at 4 C for 4 min <111>, n/p, 5 Ωcm, 5 µm on 3 µm Cz-substrate, CiS process

3 Oxygen Concentration in FZ- and Cz-Silicon Oxygen depth profile with SIMS (ITME+SIMS lab. Warsaw) SIMS profiles of O-concentration for DOFZ at 115 C and for as grown Cz-wafers - all wafers: thickness = 28 µm Oxygen profile for 24, 48, 72 h and Cz 1 Average O-concentration with IR 16 5 Cz as grown, <O> = 8.14e17 O/cm absorption 3, <C> = 1.7e15 C/cm 3 FZ 72h/115 C, <O> = 1.14e17 O/cm 3, <C> = 2.9e15 C/cm 3 FZ 48h/115 C, <O> = 9.86e16 O/cm 3, <C> = 5.8e15 C/cm 3 FZ 24h/115 1 (ITME) C, <O> = 5.68e16 O/cm 3, <C> = 3.3e15 C/cm O-concentration [cm -3 ] SIMS-PROFILES FZ AND CZ FOR RAINER depth [µm] DOFZ 24 h 48 h 72 h Cz SIMS: <[O]> IR: [O]

4 Resistivity and Impurity Profiles of EPI - Silicon Ro [ Ohmcm ] 1E+2 1E+1 1E+ 1E-1 1E depth [ µm ] EPI-layer: n-type, P doped <ρ> between -4 µm: 54.8 ± 2.1 Ωcm <ρ> after device process: 62.9 ± 2.8 Ωcm Thickness: 49.5 ± 1.6 µm Substrate: n-type, Sb doped, <111> ρ =.15 Ωcm Thickness: 32 µm 1E+19 concentration [cm -3 ] 1E+18 1E+17 1E+16 1E+15 1E+14 Oxygen Carbon Oxygen diffusion from Cz-substrate into epilayer <[O]> cm -3 in epi-layer Carbon concentration near detection limit <[C]> cm -3 depth [µm]

5 Irradiation Experiments Source StFZ DOFZ Cz EPI CERN PS: 2-24 GeV/c protons Jyvaeskylae: 1 MeV protons PSI: 19 MeV pions Legnaro: 58 MeV Li-ions Ljubljana: reactor neutrons Louvain: 3-6 MeV neutrons Trieste: 9 Mev electrons BNL: 6 Co gamma rays , 25 Numbers are maximal particle fluences in cm -2 and for 6 Co dose values in Mrad

6 Macroscopic properties Investigations Proton & neutron damage EPI devices : see G. Lindström, this workshop 9 MeV electron damage EPI, STFZ, DOFZ: see D. Contarato, this workshop 58 MeV Li-ion damage EPI +: see A. Candelori, this workshop Proton & pion damage Cz devices : this presentation Microscopic studies Annealing studies by DLTS on STFZ, DOFZ and EPI devices: see J. Stahl, this workshop Important point defects after gamma and proton irradiation investigated by TSC technique: see I. Pintilie, this workshop

7 High Resistivity Cz-Silicon 19 MeV Pions CERN-SCENARIO EXPERIMENT 8 CERN scenario experiment - 19 MeV pions CERN scenario experiment - 19 MeV pions V dep [V] Cz-TD killed Cz-TD generated CE-standard FZ CF-DOFZ 24 h/115 o C N eff [cm -3 ] I rev [A] Cz-TD killed Cz-TD generated CE-standard FZ CF-DOFZ 24 h/115 o C Φ π [cm 2 ] No type inversion for both Cz materials introd. rate of donors > introd. rate of acceptors at high fluences N eff (Φ) = N eff, exp(-c Φ) + β eff Φ, β eff = β donor - β acceptor Cz TD killed: β eff = cm -1 Cz TD generated: β eff = cm Φ π [cm 2 ] Same I rev increase for all materials <α pion > = (3.9 ±.17) 1-17 A/cm

8 Current Pulse Shape Measurements - Cz Silicon pion irradiation injection of short laser light pulses (67 nm), V bias = 4 V Electron transport Hole transport 14 CIS-1-CZ (TD killed), p + -illumination 12 CIS-1-CZ (TD killed), n + -illumination 15 9 current [arb. units] 7 35 Φ pions = 6 x 1 14 Φ pions = 4 x 1 14 Φ pions = 2 x 1 14 Φ pions = 1 x time [ns] current [arb. units] 6 3 Φ pions = 6 x 1 14 Φ pions = 4 x 1 14 Φ pions = 2 x 1 14 Φ pions = 1 x time [ns] Slope of electron pulse always negative electric field decreasing from front to rear side: bulk remains n-type Slope at low fluence positive bulk is n-type Change of slope sign at high fluence due to strong hole trapping

9 High Resistivity Cz-Silicon CERN-SCENARIO EXPERIMENT Comparison with standard FZ-,, DOFZ-silicon V dep [V] CZ <1>, TD killed STFZ <111> DOFZ <111>, 72 h 115 C proton fluence [1 14 cm -2 ] N eff [1 12 cm -3 ] I(V dep ) [µa] Cz <1>, TD killed STFZ <111> DOFZ <111>, 72 h 115 C proton fluence [1 14 cm -2 ] Cz silicon: no inversion in full Φ range β eff = cm -1 STFZ: inverted above Φ=1*1 14 cm -2 β eff = cm -1 DOFZ: inverted above Φ=1*1 14 cm -2 β eff = cm -1 Same I rev increase for all materials <α proton > = (2.9 ±.3) 1-17 A/cm

10 High Resistivity Cz-Silicon Annealing at 8 C U dep [V] CZ<1> 8 C annealing = 5,62 x 1 14 cm -2 = 3,73 x 1 14 cm -2 = 1,89 x 1 14 cm -2 = 1,3 x 1 14 cm -2 = 7,44 x 1 13 cm -2 = 3,78 x 1 13 cm -2 plateau Annealing of Vdep resp. Neff strongly different from that of STFZ or DOFZ Plateau region cannot be described by Hamburg model Short term annealing region: all devices are not inverted t [min] Long term annealing region: for high fluences (>1 14 p/cm²) type inversion occurs Parameterization (excluding plateau region): N eff (Φ,t) = N A (Φ,t) + N C (Φ) + {N Y,1 (Φ,t) + N Y,2 (Φ,t)} short term annealing + stable damage + long term (reverse) annealing

11 High Resistivity Cz-Silicon Reverse annealing amplitudes N Y,inf [1 12 cm -3 ] annealing at 8 C reverse annealing CZ<1> N Y,inf,ges N Y,inf,1 N Y,inf, [1 14 cm -2 ] Two components: N Y,1 amplitude saturates for Φ > 2*1 14 cm -2 N Y,2 linear in Φ Sum N Y,1 + N Y,2 behaves similar to DOFZ

12 High Resistivity Cz-Silicon Reverse annealing time constants at 8 C, comparison with STFZ and DOFZ τ Y [min] DOFZ<111> 24 h RT StFZ<111> 24 h RT StFZ [1 14 cm -2 ] Two components in Cz: for both 2-nd order reaction τ Y,2 = 14 min τ Y,1 = 21 min both values independent of fluence STFZ: one component, 1-st order reaction, τ Y independent of fluence DOFZ: one component, 2-nd order reaction, τ Y linear increase versus fluence

13 High Resistivity Cz-Silicon Stable damage N C [1 12 cm -3 ] C annealing N C CZ<1> stable damage [1 14 cm -2 ] Stable component: According to Hamburg model: N eff (Φ,t) = N eff (Φ=) - N eff (Φ,t) N C always negative since N eff (Φ,t=8 min) N C > N eff (Φ=) (donor creation > acceptor creation) effective introduction rate: g c,acceptors g c, donors = -.34 cm -1 for DOFZ: = +.66 cm -1 for STFZ: = cm -1

14 High Resistivity Cz-Silicon Trapping 1/τ eff,e [ns -1 ] DOFZ<111> StFZ <111> CZ <1> global fit Electrons 1/τ eff,h [ns -1 ] DOFZ <111> StFZ <111> CZ <1> global fit Holes [1 14 cm -2 ] [1 14 cm -2 ] Trapping probabilities for electrons and holes extracted from 67 nm laser-light induced TCT measurements Hole trapping slightly stronger than electron trapping (confirmation of G. Kramberger results) Trapping seems to be independent on material type (see simulations of CCE for EPI-devices, G. Lindström talk)

15 High Resistivity Cz-Silicon Collected charge versus bias voltage for α-particles Collected charge Q [arb. units] CZ 3 µm Before irradiation = 3,73 x 1 13 = 7,44 x 1 13 = 1,3 x 1 14 = 1,89 x 1 14 = 3,73 x 1 14 = 5,62 x Bias voltage [V] TCT measurements for α-particles: injection to p+ electrode measurements at RT integration time 6 ns α-source: 244 Cm, E α = 5.8 MeV Fluence range: cm -2 to cm -2

16 High Resistivity Cz-Silicon Charge collection efficiency CCE for α-particles CCE GeV/c protons EPI-detector CZ-detector fits [1 14 cm -2 ] Comparison of CCE between Cz- and EPI-detector Parameterization: CCE(Φ) = 1 β α Φ Cz-detector: CCE taken at V bias = 45 V collection time 4 ns β α = cm 2 EPI-detector: CCE taken at V bias = 175 V collection time.5 ns β α = cm 2

17 FURTHER DEVELOPMENTS Studies on material and process related problems in FZ-silicon Understanding of differences in radiation hardness between different material and different manufacturer Detailed studies on Cz- and EPI-silicon Improvement of process technology: Thermal donor annealing/generation, role of oxygen clusters, hydrogen, nitrogen Hydrogen can act as a catalyst in the formation of TD s Improved material and defect characterization before and after device processing Microscopic and macroscopic studies: Understanding of radiation induced generation of shallow donors (type of TD s) and deep acceptors responsible for detector performance Understanding of annealing behavior at elevated temperatures Systematic investigation on trapping at different temperatures Next steps Processing and investigation of MCz devices Processing and investigation of 25µm & 75µm thick 5 Ωcm EPI-layers on Cz-Si Processing and investigation of 5µm EPI-layer on low resistivity FZ-Si Investigation of 5µm thick high resistivity FZ-devices processed by MPI-Munich

18 High Resistivity MCz and Cz-Silicon CERN-SCENARIO EXPERIMENT Comparison with standard FZ-,, DOFZ-silicon V dep [V] CZ <1>, TD killed STFZ <111> DOFZ <111>, 72 h 115 C MCZ <1>, Helsinki N eff [1 12 cm -3 ] I(V dep ) [µa] Cz <1>, TD killed STFZ <111> DOFZ <111>, 72 h 115 C MCZ <1>, Helsinki proton fluence [1 14 cm -2 ] Cz silicon: no inversion in full Φ range β eff = cm -1 c = cm 2 MCz silicon: no inversion in full Φ range β eff = cm -1 c = cm proton fluence [1 14 cm -2 ] Same I rev increase for all materials MCz: <α proton > = (3.5 ±.2) 1-17 A/cm

19 High Resistivity MCz and Cz-Silicon Corrected current pulse shapes annealing behavior I [arb. units] min 24 min 96 min 45 min 8 C back t [ns] Low fluence regime: during full annealing cycle slope of pulse shape always positive no SCSI-inversion =3,78 x 1 13 cm -2 V bias = 3 V I [arb. units] min 24 min 96 min 45 min 8 C back =5,62 x 1 14 cm -2 V bias = 4 V t [ns] High fluence regime: annealing up to 96 min at 8 C positive slope dominant no SCSI-invers. for 45 min negative slope dominant SCSI-inversion for long term annealing