1. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. 14 th International Workshop on Room Temperature Semiconductor Detectors and Associated Electronics“, 19-22 October 2004, Rome, Italy. Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors Department of Electronics Engineering and Information Science Milano - Italy Giuseppe Bertuccio Politecnico di Milano and INFN

2. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. The Front-End Electronics is made for a detector Introduction The design challenges start from the detector Silicon Carbide Detectors …a step forward for Front-end Electronic Design (useful also for other detectors…) A stimulating case…

3. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. Leakage Current Density State of the art detectors Si / GaAs 1 nA/cm 2

4. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. Leakage Current Density State of the art detectors 1000 SiC 1 pA/cm 2 Si / GaAs 1 nA/cm 2

5. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. Leakage Current Density State of the art detectors Si / GaAs 1 nA/cm 2 SiC 1 pA/cm 2 1000

6. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. SiC pixel detector: from 27 °C to 100°C 43 e - r.m.s. @ 100 °C 17 e - r.m.s. @ 27 °C Front-End limited

7. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. SiC Pixel Detectors SiC Pad detectors : J SiC = 1 – 10 pA/cm 2 Current of a pixel ? V BIAS =0V; I = 0 ± 0.1 fA I REV = 1.6 fA - 16 fA ! Area = 400 x 400  m 2 4x4 Prototype SiC pixel 400 x 400  m 2

8. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. Pixel Leakage Current SiC Pad detectors : J SiC = 1 – 10 pA/cm 2 Current of a pixel ? V BIAS =200V; I = 3.16 ± 0.3 fA V BIAS =0V; I = 0 ± 0.1 fA I REV = 2 fA - 16 fA ! Area = 400 x 400  m 2 4x4 Prototype SiC pixel 400 x 400  m 2

9. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. June 2004 : Reverse Current Map Leakage Current @ 27 °C I = 274 fA : 1 pixel I = 98 fA : 1 pixel I = 36 fA : 1 pixel I < 10 fA : 12 pixels Leakage Current @ 27 °C I = 274 fA : 1 pixel I = 98 fA : 1 pixel I = 36 fA : 1 pixel I < 10 fA : 12 pixels Leakage Current E.N.C. @ 27 °C @ 10  s I = 274 fA : 1 pixel = 5.8 e- I = 98 fA : 1 pixel = 3.5 e - I = 36 fA : 1 pixel = 2 e- I < 10 fA :12 pixels < 1 e- r.m.s. Leakage Current E.N.C. @ 27 °C @ 10  s I = 274 fA : 1 pixel = 5.8 e- I = 98 fA : 1 pixel = 3.5 e - I = 36 fA : 1 pixel = 2 e- I < 10 fA :12 pixels < 1 e- r.m.s. SiC pixel A Room Temperature Sub-electron noise Semiconductor Detector SiC pixel A Room Temperature Sub-electron noise Semiconductor Detector I < 10fA : 12 pixels 10 fA I < 10fA : 12 pixels < 1 e- r.m.s.

10. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. Is it realistic to think to a sub-electron noise room temperature Front-End Electronics ? Is it possible sub-e-noise in standard CMOS Technology ? If not, what is the ultimate noise limit ? 1, 2, 5… electrons r.m.s. ? What does set the noise limit in CMOS ? 1/f or others ? What is the power level required to achieve the ultimate noise ? Is this power compatible with a thousand channels pixel detector or it is reasonable only for few channels detectors ? Some questions…

11. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. Design toward sub-electron noise FE…

12. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. E. Gatti, V. Radeka, P.F. Manfredi, M. Sampietro, V. Re, A. Pullia, P. O’Connor, G. De Geronimo, G. Bertuccio … Front End Noise

13. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. outline The classical theory and its limits 1/f noise : models and experiments Optimisation of ENC 1/f Ultimate limit of ENC 1/f 1 / f Noise

14. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. ENC 1/f: the classical theory Assumptions - S v is independent by I - S v scales with (WL) -1 Are these assumptions always true ? Capacitive Matching Capacitive Matching

15. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. S V : Experimental data PMOS 30/2 ( AMS 0.35  m ) 10  A 1/f 30  A 100  A 300  A  S V /S V ~ 100 % ! !?

16. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. Models of 1/f noise  Hooge model :   McWhorter model  N  Unified - correlated model  N -  N : carriers numbers v : carrier velocity  Hooge model :   McWhorter model  N  Unified - correlated model  N - 

17. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome.  : Hooge model - Empirical model - Proposed by Hooge in 1969 to explain 1/f noise in homogeneous semiconductors (resistors) 1/f origin:  fluctuations due to phonon scattering

18. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome.  : McWhorter model - Based on a model proposed by McWhorter in 1957 - Fluctuation of number of free carriers Si SiO 2 qq -  N Si SiO 2  1/f origin in MOSFET  N due to charge trapping / detrapping in SiO 2

19. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. S I  vs.  model Ohmic Saturation Subthreshold  

20. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. What the experiments say…

21. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. p –MOSFET 10/10 (L min = 90 nm) Subthreshold S I I 2 Valenza et al. IEE 2004  vs.  models Subthreshold    N model (McWhorter)

22. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome.  vs.  models Saturation   Saturation S I (V GS - V T ) 3  (Hooge) model p –MOSFET 10/10 (L min = 90 nm) Valenza et al. IEE 2004

23. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome.  vs.  : experimental PMOS NMOS ST Microelectronics 0.13  m CMOS Marin et al. - IEE 2004  N - McWhorter model I  Hooge model saturation

24. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. bias region  Hooge  – McWhorter SUBTHRESHOLD --PMOS & NMOS OHMIC PMOSNMOS SATURATION PMOSNMOS  vs.  model PMOS : deeper channel → bulk effect →  NMOS: interface channel → trapping effects →  N PMOS : deeper channel → bulk effect →  NMOS: interface channel → trapping effects →  N

25. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. Implication for Front-end designs…

26. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome.  vs.  ENC optimisation Saturation   SISI SVSV SVSV I  SVSV I 

27. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. Design for  N-1/f MOSFET’s…

28. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. ENC 1/f :  model: Saturation independent by I same for equal area WL minimum for C G = C IL independent by I same for equal area WL minimum for C G = C IL

29. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. Ultimate limit of ENC 1/f 1 50 fF 3 e - 0.5 pF

30. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. Design for  - 1/f MOSFET’s…

31. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome.  model: ENC 1/f minimum for C G = C IL minimum for C G = 3 C IL minimum current (within saturation) constant current In contrast with series white noise minimisation

32. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. ENC optimisation 1/f White ENC 2 I 1/f ws I opt CGCG 1/f ws C OPT 1/3C IL 3C IL C G = 3 C IL C G = C IL /3

33. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. ENC optimisation Current [A] Gate width W [  m] ENC [electrons r.m.s. ] C IL =0.3 pF  = 10  s PMOS AMS 0.35  m  H =4.6 10 -5 C IL =0.3 pF  = 10  s PMOS AMS 0.35  m  H =4.6 10 -5 I opt = 14  A W opt = 183  m ENC min = 2.8 e - r.m.s. I opt = 14  A W opt = 183  m ENC min = 2.8 e - r.m.s. 14  A 183

34. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. Summary - Conclusions RT detectors with sub-electron noise (SiC) Ultimate limit of CMOS Front End 1/f noise models revised  McWhorter model limits  Hooge & unified models  Bias dependent 1/f noise  Bias Current / Geometry MOSFET optimisation ENC 1/f : 1 - 3 e - r.m.s. at RT for C IL 50-500fF ENC tot = 3 e - r.m.s. (C IL = 0.3pF ) experimental data based

35. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. Acknowlegments Andena Marco Caccia Stefano Maiocchi Diego Mallardi Enzo Masci Sergio Olivieri Gianluigi Thanks to:

36. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome.

37. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome.

38. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome.

39. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. Sub-electron noise Front End : is it interesting ? Intrinsic detector noise Si GaAs CdTe SiC 6464 1 keV 30 60 eV 1

40. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. Parallel noise: MOSFET Gate leakage 1 nA 90 nm Technology t ox = 1.5 nm PMOS 0.3/10 IGIG 100 nA IDID Valenza et al. IEE 2004

41. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. I D = 20  A I D = 5 mA AMS CMOS 0.35  m PMOS 300/0.4 AMS CMOS 0.35  m t ox = 7.6 nm

42. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. 1/f ENC component Current [A] Gate width W [  m] ENC [electrons r.m.s. ] C IL =0.3 pF  = 10  s PMOS AMS 0.35  m  H =4.6 10 -5 C IL =0.3 pF  = 10  s PMOS AMS 0.35  m  H =4.6 10 -5 I opt = 1  A W opt = 570  m ENC min = 1.4 e - r.m.s. I opt = 1  A W opt = 570  m ENC min = 1.4 e - r.m.s. 1  A 570

43. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. White series Current [A] Gate width W [  m] ENC [electrons r.m.s. ] C IL =0.3 pF  = 10  s PMOS AMS 0.35  m  H =4.6 10 -5 C IL =0.3 pF  = 10  s PMOS AMS 0.35  m  H =4.6 10 -5 I opt = 10 mA W opt = 60  m ENC min = 0.8 e - r.m.s. I opt = 10 mA W opt = 60  m ENC min = 0.8 e - r.m.s. 10 mA 60

44. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. Unified model : correlated  - Proposed by Mikoshiba in 1982, developed in 1987-91 - Trapping (  N) & mobility (  ) fluctuations correlation Si SiO 2  Si SiO 2 -  ± 

45. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. Magnitude N &  sc determines  N or  dominance Implemented in SPICE BSIM3 Unified model : correlated 

46. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. 120 eV FWHM 55 Fe 1 0.9 e- r.m.s. NIM A361 (1995) Floating gate amplifier - multiple non destructive readings T = - 110 °C Processing time 160  s = ( 16 readings ) x 10  s Floating gate amplifier - multiple non destructive readings T = - 110 °C Processing time 160  s = ( 16 readings ) x 10  s 

47. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. SiC properties Wide Bandgap E G =3.2 eV High saturation velocity v S = 200  m/ns High Critical Field E C = 2 MV/cm High thermal conductivity  SiC   Si

48. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. PMOS 3.5 e - 6.5 e - 1pF AMS PMOS: L min = 0.35  m ;  =126 cm 2 /Vs ; A 1 =1 AMS PMOS: L min = 0.35  m ;  =126 cm 2 /Vs ; A 1 =1 1

49. G. Bertuccio “Challenges in the Design of Front-End Electronics for Semiconductor Radiation Detectors ” 14 th International Workshop on Room Temperature Semiconductor X-Ray and Gamma-Ray detectors, October 18-21, Rome. W/L = 2000/0.5 ( STM 0.18  m process) I D : 0.25 - 0.5 - 1 mA PMOS I D : 0.25 - 0.5 - 1 mA NMOS ENC 1/f : experimental from Manghisoni et al., IEEE TNS 2002 3