WODEAN workshop, Vilnius University 02/03-June-2007

1. Macroscopic Effects in n-MCz Diodes after Neutron Irradiation Depletion Voltage and Reverse Current G. Lindstroem a, E. Fretwurst a, F. Hönniger a, A. Junkes a, K. Koch a and I. Pintilie a,b a Institute for Exp. Physics, University of Hamburgb National Institute for Materials Physics NIMP, Bucharest WODEAN workshop, Vilnius University 02/03-June-2007

2. Outline: • Properties of used diodes • Effective doping • Reverse current • Conclusions WODEAN workshop, Vilnius University 02/03-June-2007

3. Diode properties Used material: WODEAN n-MCZ (OKMETIC), P-doped 900 Wcm, Neff = 4.8E+12 cm-3 Diode processing: CiS Erfurt, thinned to d = 95 mm rear contact: P-implanted: Neff = 4.8E+12 cm-3P-diffused: Neff = 7.7E+12 cm-3(TD generation during thermal process) O and C concentration:[O] = 5E+17 cm-3(outdiffusion below 10 mm) [C] < 3E+15 cm-3(detection limit) WODEAN workshop, Vilnius University 02/03-June-2007

4. Effective doping concentrationDependence on F and annealing-General Reminder- High resistivity FZ silicon: Annealing function –“Hamburg model“ 300 mm diodes not usable up to 1E+16 n/cm²full depletion voltage exceeds 10 KV! Cure: use of lower resistivity and thin diodes,hence 100 mm and <1kWcm Short term: beneficial annealingLong term: reverse annealingtime constants depending on temperature!Tann = 80C: 100 to 1000 min (rev.anneal) Tann = RT: 1 to 10 years WODEAN workshop, Vilnius University 02/03-June-2007

5. Annealing function for n-MCz 100 mm diodes DN = Neff,0-Neff(F,t) = Na(F,tann) + NC0(1-exp(-cF)) + gC·F + NY(F,tann) Na: beneficial annealingNC: stable damage, NC0(1-exp(-cF)): donor removal (NC0 = Neff,0) gCF: acceptor generationNY: reverse annealing (increase of neg. space charge during annealing) NY DNmin≈ NC WODEAN workshop, Vilnius University 02/03-June-2007

6. Annealing time constants All values measured for Tanneal = 80 °C, no real difference to known results from other Si-diodes (FZ, epi) WODEAN workshop, Vilnius University 02/03-June-2007

7. Annealing time constants All values measured for Tanneal = 80 °C, no real difference to results from MCz with standard processAnnealing behaviour not affected by thermal donors! WODEAN workshop, Vilnius University 02/03-June-2007

8. Beneficial annealing amplitude Saturation fit for Na(F) misleadingAt F=3E+15 n/cm²: tirrad = 25 min, Tirrad = 70-80 °Chence strong self annealing during annealing!Linear fit for F≤ 1E+15 n/cm² reliablega = 1.2E-2 cm-1 WODEAN workshop, Vilnius University 02/03-June-2007

9. Stable damage component NC Remember: NC = NC0(1-exp(-cF)) + gCFNC0 = Neff,0 if only P-doping donor removal by formation of E-center (VP)! Rear side P-implanted: NC0 = 5E+12/cm³ ≈ Neff,0: ok☺Rear side P-diffused: NC0 similar to P-implanted: P-donors removedThermal donor concentration = 2E+12/cm³, stays constant during annealingdonor removal rate c ≈ 1E-14 cm², NC0*c ≈ 5E-2 cm-1: ok☺acceptor introduction rate = 9E-3cm-1: about 2x larger than for thin FZ, epi! WODEAN workshop, Vilnius University 02/03-June-2007

10. Comparison of Neff(F) at DNmin measured in thin diodes For tanneal = 8 min at 80 °C n-MCz WODEAN workshop, Vilnius University 02/03-June-2007

11. Side remark (not WODEAN): Comparison between 50 mm n-type and p-type epi diodes after n-irradiation n-type epi: P-donor removal (small F) + BD donor generation (large F)p-type epi: B-acceptor removal (small F) + acceptor generation (large F) WODEAN workshop, Vilnius University 02/03-June-2007

12. Reverse annealing amplitude NY Assumed annealing function: 1st and 2nd order for best fitNY = sum of both amplitudes reliable!Saturation fit with acceptor introduction rate for small F: gY0 = 5E-2 cm-1in agreement with other materials WODEAN workshop, Vilnius University 02/03-June-2007

13. Reverse current Annealing function for a in comparison to p-epi Linear fit for IFD/Vol as fct. of F Shape of annealing function does not differ significantly from other known results (see RD50 talk E. Fretwurst) Linear fit for IFD/Vol = a·F gives a = 4.1E-17Acm-1which is the generally accepted value Results are in general agreement with known datasome deviations of annealing function (as for all thin diodes) from the old fit (M. Moll) WODEAN workshop, Vilnius University 02/03-June-2007

14. Conclusions • general behaviour of n-MCz diodes as known for other material although [O] = 5E+17 cm-2 is large • thermal donors generated in n-MCz before irradiation are not affected by radiation damage • Complete donor removal observed with rate constant c ≈ 1E-14 cm² • Acceptor introduction rate gC = 9E-3 cm-1 about 2 x larger than for other known materials • Reverse current in accordance with other data a = 4.1E-17 Acm-1 WODEAN workshop, Vilnius University 02/03-June-2007

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22. Hydrogenation of Silicon – First Attempts Implantation of 710 keV D, R = 7 mm WODEAN workshop, Vilnius University 02/03-June-2007