Gunnar Lindstroem – University of Hamburg1 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 Hamburg b National Institute for Materials Physics NIMP, Bucharest Macroscopic Effects in n-MCz Diodes after Neutron Irradiation Depletion Voltage and Reverse Current WODEAN workshop, Vilnius University 02/03-June-2007

Gunnar Lindstroem – University of Hamburg2 Outline: 1.Properties of used diodes 2.Effective doping 3.Reverse current 4.Conclusions WODEAN workshop, Vilnius University 02/03-June-2007

Gunnar Lindstroem – University of Hamburg3 Used material: WODEAN n-MCZ (OKMETIC), P-doped 900  cm, N eff = 4.8E+12 cm -3 Diode processing: CiS Erfurt, thinned to d = 95  m rear contact: P-implanted: N eff = 4.8E+12 cm -3 P-diffused: N eff = 7.7E+12 cm -3 (TD generation during thermal process) WODEAN workshop, Vilnius University 02/03-June-2007 O and C concentration: [O] = 5E+17 cm -3 (outdiffusion below 10  m) [C] < 3E+15 cm -3 (detection limit) Diode properties

Gunnar Lindstroem – University of Hamburg4 WODEAN workshop, Vilnius University 02/03-June-2007 Effective doping concentration Dependence on  and annealing -General Reminder- 300  m diodes not usable up to 1E+16 n/cm² full depletion voltage exceeds 10 KV! Cure: use of lower resistivity and thin diodes, hence 100  m and <1k  cm High resistivity FZ silicon: Annealing function –“Hamburg model“ Short term: beneficial annealing Long term: reverse annealing time constants depending on temperature! T ann = 80C: 100 to 1000 min (rev.anneal) T ann = RT: 1 to 10 years

Gunnar Lindstroem – University of Hamburg5 WODEAN workshop, Vilnius University 02/03-June-2007  N min ≈ N C NYNY Annealing function for n-MCz 100  m diodes  N = N eff,0 -N eff ( ,t) = N a ( ,t ann ) + N C0 (1-exp(-c  )) + g C ·  + N Y ( ,t ann ) N a : beneficial annealing N C : stable damage, N C0 (1-exp(-c  )): donor removal (N C0 = N eff,0 ) g C  : acceptor generation N Y : reverse annealing (increase of neg. space charge during annealing)

Gunnar Lindstroem – University of Hamburg6 WODEAN workshop, Vilnius University 02/03-June-2007 Annealing time constants All values measured for T anneal = 80 °C, no real difference to known results from other Si-diodes (FZ, epi)

Gunnar Lindstroem – University of Hamburg7 WODEAN workshop, Vilnius University 02/03-June-2007 Annealing time constants All values measured for T anneal = 80 °C, no real difference to results from MCz with standard process Annealing behaviour not affected by thermal donors!

Gunnar Lindstroem – University of Hamburg8 WODEAN workshop, Vilnius University 02/03-June-2007 Beneficial annealing amplitude Saturation fit for N a (  ) misleading At  =3E+15 n/cm²: t irrad = 25 min, T irrad = °C hence strong self annealing during annealing! Linear fit for  ≤ 1E+15 n/cm² reliable g a = 1.2E-2 cm -1

Gunnar Lindstroem – University of Hamburg9 WODEAN workshop, Vilnius University 02/03-June-2007 Stable damage component N C Remember: N C = N C0 (1-exp(-c  )) + g C   C0 = N eff,0 if only P-doping donor removal by formation of E-center (VP)! Rear side P-implanted: N C0 = 5E+12/cm³ ≈ N eff,0 : ok ☺ Rear side P-diffused: N C0 similar to P-implanted: P-donors removed Thermal donor concentration = 2E+12/cm³, stays constant during annealing donor removal rate c ≈ 1E-14 cm², N C0 *c ≈ 5E-2 cm -1 : ok ☺ acceptor introduction rate = 9E-3cm -1 : about 2x larger than for thin FZ, epi!

Gunnar Lindstroem – University of Hamburg10 WODEAN workshop, Vilnius University 02/03-June-2007 Comparison of N eff (  ) at  N min measured in thin diodes For t anneal = 8 min at 80 °C n-MCz

Gunnar Lindstroem – University of Hamburg11 WODEAN workshop, Vilnius University 02/03-June-2007 Side remark (not WODEAN): Comparison between 50  m n-type and p-type epi diodes after n-irradiation n-type epi: P-donor removal (small  ) + BD donor generation (large  ) p-type epi: B-acceptor removal (small  ) + acceptor generation (large  )

Gunnar Lindstroem – University of Hamburg12 WODEAN workshop, Vilnius University 02/03-June-2007 Reverse annealing amplitude N Y Assumed annealing function: 1 st and 2 nd order for best fit N Y = sum of both amplitudes reliable! Saturation fit with acceptor introduction rate for small  : g Y0 = 5E-2 cm-1 in agreement with other materials

Gunnar Lindstroem – University of Hamburg13 WODEAN workshop, Vilnius University 02/03-June-2007 Reverse current Annealing function for  in comparison to p-epiLinear fit for I FD /Vol as fct. of  Shape of annealing function does not differ significantly from other known results (see RD50 talk E. Fretwurst) Linear fit for I FD /Vol =  ·  gives  = 4.1E-17Acm-1 which is the generally accepted value Results are in general agreement with known data some deviations of annealing function (as for all thin diodes) from the old fit (M. Moll)

Gunnar Lindstroem – University of Hamburg14 WODEAN workshop, Vilnius University 02/03-June-2007 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 g C = 9E-3 cm -1 about 2 x larger than for other known materials Reverse current in accordance with other data  = 4.1E-17 Acm -1

Gunnar Lindstroem – University of Hamburg15 WODEAN workshop, Vilnius University 02/03-June-2007

Gunnar Lindstroem – University of Hamburg16 WODEAN workshop, Vilnius University 02/03-June-2007

Gunnar Lindstroem – University of Hamburg17 WODEAN workshop, Vilnius University 02/03-June-2007

Gunnar Lindstroem – University of Hamburg18 WODEAN workshop, Vilnius University 02/03-June-2007

Gunnar Lindstroem – University of Hamburg19 WODEAN workshop, Vilnius University 02/03-June-2007

Gunnar Lindstroem – University of Hamburg20 WODEAN workshop, Vilnius University 02/03-June-2007

Gunnar Lindstroem – University of Hamburg21 WODEAN workshop, Vilnius University 02/03-June-2007

Gunnar Lindstroem – University of Hamburg22 WODEAN workshop, Vilnius University 02/03-June-2007 Hydrogenation of Silicon – First Attempts Implantation of 710 keV D, R = 7  m