1. Effect of Metal Overhang on Electric Field for Pixel Sensors Kavita Lalwani, Geetika Jain, Ranjeet Dalal, Kirti Ranjan & Ashutosh Bhardwaj Department of Physics & Astrophysics, University of Delhi, INDIA SIMULATION GROUP MEETING 13 January, 2015 Delhi, India SIMULATION GROUP MEETING 13 January, 2015 Delhi, India Simulation Group Meeting, 23/1/2015 1

2. Simulated Structure for pixel sensor (three Pixel) D=200um 2 x  y  z=100  200  1 um 3 3 Pixel Structure Bulk Type = Boron Bulk Density = 2  10 12 cm -3 Bulk profile=constant Aluminium=0.55um Gate SiO2=0.25um Field SiO2 = 0.7um Areafactor = NIL 2 Contact Vias Parameters Used Frontside Implant Type = Phosphorus Frontside Implant Density = 1  10 19 cm -3 Frontside Implant Profile = Gaussian, y=1.5um, x=1.05um Backside Implant Type = Boron Backside Implant Density = 1  10 19 cm -3 Backside Implant Profile = Gaussian, y=1.5um, x=1.05um Pstop density = 1  10 16 cm -3 Pstop implant profie= Gaussian, y=1.0um, x= 0.7um Configuration-Pstop, implant wide Metal overhang = 0, 4um T=253K For Non Irradiated Pixels- Qf=1e11cm -2 + 2Nit traps [1] For Irradiated Pixels- Radiation Damage Model=2bulktraps + Qf +2Nit traps [2] Q f = 2e12cm -2 Fluence = 0 (Non irradiated case), 1e15, 2e15, 5e15, 1e16cm -2 References-[1] Dissertation, “X ray Radiation damage studies and Design of a silicon pixel sensors for science at the XFEL, by Jiaguo Zhang, 2013. [2] “Simulation of Irradiated Si Detectors”, Ranjeet Dalal et al, Proceeding of Vertex 2014 2]2]

3. 2D Electric Field Profiles for Non Irradiated Pixel Sensors Configuration-Pstop, implant wide MO=0um MO=4um Maximum electric field is at the curvature of n+ strips 3 Applied reverse bias = 1000V Maximum electric field is under the MO It is expected that effect of MO would be significant for non irradiated pixel sensors N+ implant No Metal overhang P Bulk N+ implant Metal overhang P Bulk N+ implant

4. Cutline of 1um Cutline of 0.1 um Non irradiated pixel sensors MO has significant effect on maximum electric field for non-irradiated pixel sensors. There is decrease in maximum electric field for MO of 4um compared to structure without MO. Applied reverse bias = 1000V MO effect on Electric Field Gap bw pstop Implant edge Gap bw pstop implant pstop edge 4

5. 2D Electric Field Profile for Irradiated Pixel Sensors Configuration-Pstop, implant wide MO = 4um MO = 0um Maximum electric field is at the curvature of n+ strips It is expected that effect of MO would not be very significant for irradiated pixel sensors 5 Applied reverse bias =1000V fluence = 2e15cm -2 Q f =2e12cm -2 No Metal overhang n+ implant P bulk fluence = 2e15cm -2 n+ implant P bulk Metal overhang fluence = 2e15cm -2 Q f =2e12cm -2

6. Irradiated Pixel sensors Electric Field for cut line of 1 um (Configuration: Pstop, Wide implant) T= 253K, D=200um, X=100um, Nb=2e12cm-3 Configuration-Pstop, implant wide 6 Applied reverse bias= 1000V MO effect on Electric Field MO does not have significant effect on maximum electric field at fluences of 1e15, 2e15 cm -2 for irradiated pixel sensors. There is small decrease in maximum electric field at fluence of 5e15 cm -2 for MO of 4um compared to structure without MO Similar results are observed for configuration pstop, normal implant small variation in max Efield at f=5e15cm -2 Cutline of 1um Q f =2e12cm -2 f=1e15cm -2 f=2e15cm -2 f=5e15cm -2

7. MO has small effect on maximum electric field at fluence of 1e16cm -2 7 Applied reverse bias =1000V Irradiated Pixel sensors small change in max Efield at f=1e16cm -2 implant pstop edge Gap bw pstop Implant edge Cutline of 1um 2D Electric Field Profile, MO=4um (fluence =1e16cm -2 ) Q f =2e12cm -2 fluence = 1e16cm -2 Metal overhang P bulk Q f =2e12cm -2 n+ implant

8. 8 Fluences (cm -2 )MO=0umMO=4umMO=0umMO=4um f=0 (Non irradiated case) 1.72  10 5 1.33  10 5 1.81  10 5 9.82  10 4 f=1e15 1.14  10 5 1.09  10 5 f=2e15 1.97  10 5 1.94  10 5 1.35  10 5 1.43  10 5 f=5e15 2.67  10 5 2.55  10 5 1.46  10 5 1.64  10 5 f=1e16 3.09  10 5 2.93  10 5 1.78  10 5 1.76  10 5 Cutline=1um Configuration- Pstop, implant wide Cutline=0.1um Comparison of Maximum Electric Field (Non Irradiated vs Irradiated Pixel Sensors) Applied reverse bias = 1000V Electric field unit V/cm

9. 9 Summary Electric field simulations are performed to study the effect of metal overhang for both non irradiated as well irradiated pixel sensors. -For Non irradiated pixel senors MO has a significant effect on maximum electric field - For irradiated pixel senors MO does not have significant effect on maximum electric field at fluences of 1e15, 2e15 cm -2 There is small decrease in maximum electric field at fluence of 5e15 cm -2 and 1e16cm -2 for MO of 4um compared to structure without MO Similar results are observed for configuration pstop, normal implant Future Plan Study the effect of various design parameters like pstop depth, pstop concentration, effective doping concentration etc on electric field profiles for non irradiated and irradiated pixel sensors Study the design optimization for the pixel structures- 1) X (width)=50um & depth =200um 2)X (width) = 25um & depth = 200um

10. 10 Thank you

11. Back-up Slides 11

12. 12 Electric Field in Bulk Irradiated pixel sensors at f=1e15cm-2 Non Irr Non Irradiated pixel sensors at QF=1e11cm-2 + interface trap

13. Conf-Pstop, Implant Wide (cutline of 1.0um) MO Effect on Electric Field at different fluences for Irradiated Strip sensors 13 Fluence = 1e15cm -2 Fluence = 2e15cm -2 Fluence = 5e15cm -2 Fluence = 1e16cm -2

14. 14 MO Effect on Electric Field at different fluences for Irradiated Strip sensors Conf-Pstop, Implant Wide (cutline of 0.1um) f=1e15cm-2 2 f=2e15cm-2 2 f=5e15cm-2 2 f=1e16cm-2 2

15. 15 Leakage Current Plot for irradiated sensors

16. 16 Net Doping, f= 1e16, MO=4um

17. Non Irradiated Pixel Sensors QF=1e11cm-2 Incorporated following two interface traps Interface trap levels Density(cm-3)  (e) and  (h) 0.60eV (e-level)0.6e111e-15, 1e-15 0.39eV (h-level)0.4e111e-15, 1e-15 17

18. Irradiated Pixel Sensors 18  Fixed interface charge density (QF) =2e12cm-2  Incorporated following two interface traps Interface trap levels Density(cm-3)  (e) and  (h) 0.60eV (e-level)12e111e-15, 1e-15 0.39eV (h-level) 8e111e-15, 1e-15 trap levelsDensity(cm-3) at f=1e15,2e15,5e15cm-2  (e) and  (h) 0.51eV (e-level) 4e15, 8e15,2e162e-14, 2.6e-14 0.48eV (h-level) 3e15,6e15,1.5e162e-14, 2e-14  Bulk Damage Model