Happy Birthday Silicon Drift Detector: Celebrating the ... - MPG HLL

Happy Birthday 

Silicon Drift Detector: 

Celebrating the First 25 years* 

*a personal view 

Chiara Guazzoni 

Politecnico di Milano and INFN Sezione di Milano 

e-mail: Chiara.Guazzoni@mi.infn.it 

www: home.dei.polimi.it/guazzoni 

C. Guazzoni – 11 th European Symposium on Semiconductor Detectors – June 9, 2009 

Happy Birthday Silicon Drift Detector: Celebrating the First 25 Years…

Summary 

1983: SDD birth - sideward depletion 

1983-1986: SDD childhood 

SDDs in the early teens: opening the 

way to new generations 

SDD is 25 years old… 



Silicon detectors before the 80’s 

solid state detectors started in the 

50’s and in the same time single-crystal 

silicon became available 

– K. G. McKay, Phys. Rev. 76 (1949) 1537 

– J. W. Mayer, IRE Trans. Nucl. Sci. NS-7 

(June, 1960) 178 

practically all detectors were Lithiumdrifted 

Detectors 

– J.T. Walton, H. A. Sommer, D. E. Greiner, 

F. S. Bieser, IEEE Trans. Nucl. Sci. 25 

(Feb. 1978) 391 



The early 80’s: 

silicon detectors’ revolutionary age 

Planar tehnology introduced by J. 

Kemmer for radiation detectors 

J. Kemmer, Nucl. Instr. Meth 169 (1980) 499 

Silicon microstrip detectors 

E. Heijne et al., Nucl. Instr. Meth. , 178 

(1980) 331 

MultiElectrode Silicon Detectors 

S. R. Amendolia et al. Nucl. Instr. Meth. 

176 (1980) 457 



The early 80’s: 

silicon detectors’ revolutionary age 

Invention of CCDs and their use as vertex detectors 

Courtesy of Chris Damerell (RAL) 

Early ’70s: CCD invented as imaging devices, but 

not immediately welcome by the HEP community 

Bell Syst Tech J, 49 (1970) 49 

1984: NA32 Experiment - North Hall 

Two CCDs, active area 0.5 Mpixels total, 1 

and 2 cm beyond the target 

Bell Syst Tech J, 49 (1970) 593 



Planar pn diodes 

p+ rectifying junction (V=-80V) 

80 

n-type substrate 

-pot ent ial (V) 

60 

40 

20 

0 

1000 

800 

600 

400 

det ect or lengt h (µm) 

200 

0 

300 

0 

10 0 

200 

det ect or t hickness (µm) 

n+ ohmic contact (V=0V) 

• Detector capacitance increases with diode active area 

• Detector capacitance decreases if diode thickness is increased 



2 

opt 

1 

3 

Planar pn diodes 

⎛ C C ⎞ 

ENC = A A kTq C I ⎜ + ⎟ + 

optimum ENC [electrons] 

1000 

100 

10 

1 

6 mm 2 

pn-diode 

matching 


Happy Birthday Silicon Drift Detector: Celebrating the First 25 Years… 

τ 

opt 

= 

A 

A 

1 

2 

V 

⎛ CG 

C ⎞ 

⎜ 

d 

+ ⎟ 

Cd 

C 

⎝ 

G 

 

 

⎠ 

3 

α 

d 

th 

ωT 

I 

L 

 

FET detector 

= 

( 

2 

C ) 

G d 

2 

2 

d L 

ENC1/ 

f T 

⎜ 

T 

Cd 

C ⎟ 

G 

detector ⎝ 

 

⎠ 

FET 

matching 

microstrip 

ω α 

5 cm 2 

pn-diode 

15 mm 2 

pn-diode 

matched conditions 

triangular shaping 

no 1/f noise 

C d , detector capacitance [F] 

10 -1 

10 -2 

10 -3 

10 -4 

10 -5 

10 -6 

10 -7 

0.1 10 

-14 10 -13 10 -12 10 -11 10 -10 10 -910-8 

optimum shaping time [s] 

A 

A 

1 

3 

C 

τ 

Energy resolution 

& 

Count rate capability 

require 

capacitance minimization 

c

When the ocean is not such a 

distance… 

Schloss Elmau (2002) 



The sideward depletion 




n+ ohmic contact 

(V=0V) 

p+ rectifying junction (-V) 



• Detector volume fully depleted by “virtual contact” (point-like) 

• Full depletion achieved with only a quarter of the bias necessary for 

standard p-n diodes 



Below depletion 


Impact on anode capacitance 

At full depletion 

• At nearly full depletion the conductive 

channel at the middle of the detector 

retracts causing the capacitance to 

drop abruptly. 

• At higher bias voltages the remaining capacitance is the lowest 

capacitance between the n+ contact and the p+ electrodes. 



n+ ohmic contact 

(V=0V) 





Capacitance value has been decoupled from detector active area 

How to bring electrons toward the anode? 



1983: the inception of SDDs 

“DPF Workshop on Collider 

Detectors: Present capabilities 

and Future Possibilities”, Lawrence 

Berkley Lab., CA, Feb 28 – March 

4, 1983: 

The concept of a 

solid state drift chamber 

2 nd Pisa Meeting on Advanced 

Detectors, Grosseto, Italy, June 

3-7, 1983: 

Semiconductor Drift Chamber – 

an application of a novel 

transport scheme 



V=0V 

Silicon Drift Detector 

-LV -HV 

Central drift region… 


+ 

+ 

+ 

Near the anode… 

-LV p 

-HV p 

•p+ junctions divided in strips with increasing potential on both sides nearly 

uniform drift field parallel to the surface 

•signal electrons focused in the center of the wafer transported at constant 

velocity towards the readout anode 

•1-D position sensing with only 1 readout channel through drift time 

•small anode capacitance low-noise measurement of time and amplitude 



1984: Patent filed… 



First measurements (BNL, 1985) 

Signal for different drift distances 

different drift fields 

425 V/cm 

130 V/cm 

E d =265 V/cm 

265 V/cm 

210 V/cm 

400 ns 

105 V/cm 

105 V/cm 

80 V/cm 

185 V/cm 

67 V/cm 

200 ns/div 

Light pulser 22000e 



Multianode Silicon Drift Detectors 

-LV 

-HV 

# n 

# n-1 

# n+1 

# n+2 


• granularity of the anodes 

provides lateral interaction 

coordinate 

• drift time measurement gives 

position along drift coordinate 

with high resolution: 

• ~2µm in lab, 

• ~10 µm in test beam 

• ~20 µm in experiments 

• external trigger required for 

2D position sensing 

-LV p 

-HV p 



SDDs in High Energy Physics 

NA45 - CERES 

@ CERN’s LEP (1992-2000) 

STAR 

@ BNL RHIC (install Feb.01) 

ALICE 

@ CERN’s LHC 

Wafer: 1 st ver.: 3” Silicon, 

280 µm thick 

2 nd ver.: 4” Silicon 

Active area: 32 cm 2 /55 cm 2 

360 collecting anodes 

Foundry: BNL/Sintef 

Wafer: 4” (NTD) Silicon, 

3 kΩcm resistivity, 

280 µm thick 

Active area: 6.3 × 6.3 cm 2 

2 × 240 collecting anodes 

Foundry: Sintef 

Wafer: 5” (NTD) Silicon, 

3 kΩcm resistivity, 

300 µm thick 

Active area: 7.02 × 7.53 cm 2 

512 collecting anodes 

Foundry: Canberra 



1989: Integration of the JFET 

R#2 

Anode 

G 

D 

S 

IGR 

R#1 



SDDs for high res. spectroscopy 

• continuous p+ back contact 

acting as entrance window 

• cylindrical geometry with 

anode in the center 

• transistor located in the 

center of the detector. 

• drift field azimuthally symmetric 

• electrons produced anywhere 

within detector active area are 

collected at the central anode 

• detector capacitance ≅ 100 fF 




• Anode capacitance: ~200 fF 

• Energy resolution: ΔE FWHM = 125 eV 

(equivalent to ENC=4 el. r.m.s.) @ 200kcps 

• Count rate capability: up to 10 6 cps 

• Peak/Background ≈ 10.000 : 1 

• Quantum efficiency: > 90% @ 0.3-10 keV 

(Boron line detection) 

• Rad. hardness: > 10 14 Mo K photons 

• Operating temperature: T ≈ - 10 o C 

Courtesy of PNSensor GmbH 

Courtesy of PNSensor GmbH 

with pulset reset PA thanks to 

on-chip reset diode 




Commercially available classic cylindrical SDDs with 

sensitive area of 5, 10 and 20 and 30 mm2 up to 1cm 2 

SDD 5 mm² 

chip 5 x 5 x 0.45 mm³ 

SDD 10 mm² 

chip 6 x 6 x 0.45 mm³ 

SDD 20 mm² 

chip 8 x 8 x 0.45 mm³ 

SDD 30 mm² 

chip 9 x 9 x 0.45 mm³ 

SDD 100 mm² 

chip 14 x 14 x 0.45 mm³ 



Droplet SDDs: novel evolution 

Anode 

• Anode + on-chip JFET outside 

detector active area improvement of 

the peak-to-background ratio. 

• Very small collecting anode output 

capacitance about 120 fF much lower 

than conventional SDDs (larger than 

200 fF) 

Mn Kα 

Mn Kβ 



Multichannel SDDs 

12x5 mm 2 

19x5 mm 2 

= 95 mm 2 

= 60 mm 2 

4 x 15 mm 2 

= 60 mm 2 16 mm 2 each 

61x5 mm 2 = 305 mm 2 

77x7 mm 2 = 539 mm 2 

6x5 mm 2 

= 30 mm 2 

4 x 10 mm 2 

= 40 mm 2 



Patent filed…not only SDDs 

Position sensitive SDDs, 

multi-anode SDDs 

Ultra-low capacitance SDDs 

Fully depleted pn-CCDs 



Sideward Depletion Family Tree 

Silicon Drift Detector 

Fully Depleted pnCCD 

field strips 

collecting 

anodes 

back electrodes 

Controlled-Drift Detector 

DePMOS 



Sideward Depletion Family Tree 

Sideward 

Depletion 

Silicon Drift Detectors 

Fully Depleted pnCCDs 

Linear geometry 

Round-shape 

“normal” 

Frame-store 

Multi-anode SDDs 

Circular 

Multi-Linear SDDs 

Droplet SD 3 

DePMOS Arrays 

Multichannel 

Circular 

Macro-Pixels 

Controlled-Drift Detectors 

Linear 

Multiple 

Readout 



# n 

n-1 

# n+1 

# n+2 

Fully depleted pnCCDs 

φ1 

φ2 

φ3 


back side contact 

• full depletion high quantum efficiency and back side illumination 

• radiation hardness thanks to pn junctions 

• pixel sizes from 30 µm to 150 µm 

• very high charge transfer efficiency 



Fully depleted pnCCDs 

CTE>.999 



XMM – Newton launched on 10.12.1999 



1993-96: Multi-Linear SDDs 

w.r.t “classical” multi-anode linear SDDs: 

• Array of deep p-implants parallel to the drift 

direction small potential barriers able to confine the 

• Trajectory of charge cloud close to the implanted 

surface, thanks to proper biasing and low-resistivity 

epitaxial layer 



1995-97: Controlled-Drift Detectors 

deep p implants HE phosphorous 

deep n implants 

+ implant 

p field strips 

out n+1 

out n 

out n-1 

+ 

p back electrode 

HV up 

LV up 

HV dw 

E1 

LV dw 

anodes 

reset FET 

first FET 

1100 

1000 


Happy Birthday Silicon Drift Detector: Celebrating the First 25 Years… 

-potential [V] 

65 

60 

55 

50 

y, drift coordinate [ µ m] 

-potential [V] 

900 

65 

60 

55 

50 

1100 

800 

700 

600 

y, drift coordinate [ µ m] 

1000 

900 

800 

1200 

700 

1100 

1000 

900 

800 

x, lateral coordinate [ µ m] 

600 

1200 

Integration 

phase 

1100 

1000 

700 

Drift 

phase 

900 

800 

x, lateral coordinate [ µ m] 

700

Controlled-Drift Detectors 

R4 

E2 

Integration 

phase 

R1 500mV/div 

R4 2V/div 

Sept. ‘97 

400 

300 

pixel #1 pixel #2 pixel #3 pixel #4 pixel #5 pixel #6 

E6 

E4 

R4 

Drift 

phase 

drift time [ns] 

200 

R1 

1 µ s/div 

E6 

R1 500mV/div 

R4 1V/div 

100 

E2 

E4 

R1 

1 µ s/div 

0 

0 180 360 540 720 900 1080 

drift distance [ m] 

µ 



DEPMOS: DEpleted P-MOSFET 



DEPMOS: DEpleted P-MOSFET 

external 

substrate 

gate 

source drain contact 

Circular topology 

internal 

gate 


back side contact 

collecting anode = internal gate 

Linear topology 

Ping-pong topology 



From single pixel to matrix… 

‣ matrix arrangement allows to turn on transistors individually 

‣ readout of charge in place of origin 

‣ no “charge transfer loss” 

‣ no “out-of-time” events 

‣ continuous row-by-row readout (through serial or parallel readout) 

‣ followed by clear of row 

‣ no waiting (charge collection) period needed 



Conclusions 

1982-1983 revolution in detector history: modern era 

for silicon detectors started 

very large family originated from Gatti & Rehak 

original idea 

SDDs drifted out from detector labs to scientific 

and industrial applications and also to… Mars 





Happy Birthday SDD!!! 

and…go on drifting 

toward new challenging fields 

for the next decades.

Happy Birthday Silicon Drift Detector: Celebrating the ... - MPG HLL

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