1. 1 Irradiation Study of n-on-P Strip Sensors K. Hara, K. Inoue, A. Mochizuki (Univ. of Tsukuba) Y. Unno, S. Terada, T. Kohriki, Y. Ikegami (KEK) K. Yamamura, K. Sato (HPK) Proton irradiation: ~1 x 10 14 to 5x10 15 1MeV n eq /cm 2 1x1 cm 2 miniature strip sensors  p-Bulk: FZ and MCz  Effect of ｐ -stop concentration and p-spray  Various p-stop structures S. Terada; KEK 26 Feb. 2007, ID week @CERN

2. 2 High resistivity ４ ” wafers available to HPK p-FZ (5~10 kΩcm, ) p-MCz (0.6~1 kΩcm, ) Strip isolation implant concentration (/cm 2 ):  p-stop only: 5x10 12, 2x10 13  p-stop (2x10 12 ) + p-splay (2x10 12 ) 1x1 cm 2 miniature sensors (of all above combinations) with 6 types of isolation structures (see next): 2 x 3 x 6 = 36 varieties Proton fluence (6 points): 1, 2, 5, 10, 20, 50x10 14 1MeV n eq /cm 2

3. 3 N-strip isolation structures IPSTP CPSTP IPSTPDFCPSTPDF AF NS 6 types:

4. 4 Proton Irradiation at Cyclotron and Radioisotope Center (CYRIC), Tohoku University Irradiation setup –Proton beamline 31-2 Energy: 70 MeV Current: 10 - 500 nA Beam spot: 4.5 mm FWHM –Samples 3 sensors/board (10 boards stack in one run) scanned over 20x44 mm 2 for uniform irradiation Took about 8 hours for 5x10 15 n eq /cm 2 with 350nA –fluence dosimetry: Al activation 27 Al(p,x) 24 Na 1x10 14 ~ 5x10 15 1 MeV-n eq /cm 2 Beam line

5. 5 I-V : isolation structures / p-implant concentrations Pre- irrad: MD more often for MCz Leakage level depends on concentration/structure but less for MCz Post- irrad: Very uniform, little dependence on concentration/structure damage constant ~ ４ x10 -17 A/cm (consistent with existing data) Pstop+PsprayPstop 5E12Pstop 2E13 5E15 2E15 5E14 @ － 20 o C FZ MCz Pre-irrad@20 o C

6. 6 C-V log C vs. log V plots (f=1kHz) Leakage current may be too much for 5E15?

7. 7 Laser CCE 1064nm laser single shot traces @1kV Current amp PT~20ns ~5mV/fC FZ MCz

8. 8 FDV (C-V and CCE) Summary CV and CCE agree more or less with each other (Difficult to evaluate 5E15) FZ reaches 600V at about 3E14, while MCz at 1E15 MCz higher than 600V at low fluence, below 5E13

9. 9 CCE Summary CCE: MCz better around 0.5 - 1x10E15 Comparable to RD50 data not fully depleted V B =1kV p-MCz: H. Hoedlmoser,RD50 workshop 06 p-DOFZ: G. Casse et al., NIMA535(2004) 362 10 16 10 13

10. 10 Conclusions and discussions Fabricated n-on-p microstrip sensors p-FZ and p-MCz wafers, with 6 types of n-strip isolation structures. p-stop implantation concentration: three values and the lowest with p-splay 1x1cm 2 miniature sensors irradiated to 70-MeV protons up to 5x10 15 1MeV n eq /cm 2 Still have micro-discharge(MD) particularly to MCz before irradiation, however, MD goes away once irradiated FDV evaluated from C-V and laser CCE measurements p-MCz: starts at ~1kV, ~400V minimum around 2x10 14 /cm 2, then increases to 600V at ~1x10 15 /cm 2 p-FZ: starts at ~150V, increases rapidly and reaches to 600V at ~3x10 14 /cm 2 Partial DV operation may be inevitable particularly to MCz at the start, unless we get higher resistivity wafer Noise studies have been under way Sensor under fabrication: 6” wafer p-FZ, p-MCz Next irradiation scheduled at the end of April, (then August, November and March)

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12. 12 Measurements of sensor characteristics N+N+ N+N+ P-bulk P-stop SiO 2 Al LCR meter A A 1.5MΩ 5V Vbias CV measurement IV measurement Isolation measurement I-V ・・・ micro discharge ? C-V/ CCE (Charge Collection Efficiency ) ・・・ evaluate full depletion voltage Isolation ・・・ evaluate electrical isolation between readout strips Al Read out CCE measurement Infrared laser ~1.5 uA if isolated, Larger if not 2200pF

13. 13 Fluence evaluation by Al activation P + Al → 24 Na + X Al (6x6cm 2 ) Al (1x1cm 2 ) on sensor Nmes : # of γ per second λ : 24 Na→γ decay rate ⊿ t : time from beam off to measurement N t : # of Al atom Γ : 24 Na→γ Branching ratio σ : cross section Eeff : SSD efficiency

14. 14 Laser CCE setup Q-switched Nd:YAG(1064nm) laser head Intensity control (Glan polarizer+ND filters) Peltier cooling block with cold N2 gas outlets (-20 o C) Reference sample Amplifier box Current amp (PT=20ns) Focusing lens Laser position monitor

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