Workshop on the Applications of Compton Camera - Baia delle Zagare, 5-7 settembre 2002.

Front-end electronics for silicon detectors

F. Corsi, C. Marzocca, G. Matarrese

Work in progress within the Bari group

Workshop on the Applications of Compton Camera - Baia delle Zagare, 5-7 settembre 2002.

ISS specs and directions

• Develop a solid state 64 pixel probe for -ray imaging.

• Energy of the photon : 140 keV.• Event rate: 4 kHz.• Probe area: 22mm x 22mm.• Spatial res.: <2 mm.

Workshop on the Applications of Compton Camera - Baia delle Zagare, 5-7 settembre 2002.

Si detectors

• Avalanche photo detectors;– good energy res. : ENC/M; – a portion of the leak. curr is increased by M;– high sensitivity of M to Vsupply and to T

(2.5% /°C): diff. bias requirements;– poor linearity for charge measurement appl.

Workshop on the Applications of Compton Camera - Baia delle Zagare, 5-7 settembre 2002.

Si detectors

• Silicon drift detectors;– good energy res. (low anode cap.); – good linearity (depending on det. design);– suitable for probe application;– leakage current (cooling);– double face processing.

Workshop on the Applications of Compton Camera - Baia delle Zagare, 5-7 settembre 2002.

Si detectors

• PIN diodes;– acceptable energy res. (dep. on Ileak and CD.); – exc. linearity;– low fab. cost;– active pixels;– simple readout scheme.

Workshop on the Applications of Compton Camera - Baia delle Zagare, 5-7 settembre 2002.

Si detectors: ENC vs sh. time (Fiorini)

(ENC/M)

Workshop on the Applications of Compton Camera - Baia delle Zagare, 5-7 settembre 2002.

1st DESIGN of PIN + JFET structure (1999):PIN Diode Area = 0.32 mm2 ; JFET’s W/L = 200/12 m. Tethrode, or double-gate JFET configuration: two separate front-gate / back-gate (p-well) contacts.

0.9

mm

Workshop on the Applications of Compton Camera - Baia delle Zagare, 5-7 settembre 2002.

2nd DESIGN of PIN + JFET structure:Size = 1800 x 900 m2 , Diode Area = 0.8 mm2, W/L=100/6

Smaller JFET cap + integrated feed-back and injection capacitors + p-stop floating ring (to reduce parasitic guard ring Cap)

Workshop on the Applications of Compton Camera - Baia delle Zagare, 5-7 settembre 2002.

other layout of PIN + JFET structures:1800 x 900 m2 , Diode Area = 0.8 mm2, W/L=100/4

Workshop on the Applications of Compton Camera - Baia delle Zagare, 5-7 settembre 2002.

Character. of PIN diodes by IRST

• eff. act. area.: 3mm2;

• peak wav.: 550nm;• resp. @ 550nm: 0.37A/W;• Quantum eff. @ 550nm: >80%;• Ileak < 50pA;

• CD=1pF;• Cut-off freq.:110 MHz.

Workshop on the Applications of Compton Camera - Baia delle Zagare, 5-7 settembre 2002.

Provis. design assumptions

• PIN diodes (active area+interc.);• Segmented scint.: 5000 vis.ph/ ph;• 2000 - to - 4000 el./ ph/det. pix.;• FE ARCH.: CSA+SH.+LATCH.- DISC.;• ENC <150 e- r.m.s. (Ileak=50pA,

CD+Cbond=1.2 pF);

Workshop on the Applications of Compton Camera - Baia delle Zagare, 5-7 settembre 2002.

Front-End structure

2 thresh. latcheddiscr.

.gm

CC

d i

f

o

Shaper

2nd Ord.

Test Input

Analogue Front-End

CSA_out Shaper_outDetector

C

C

Delay

line

to fast-or circuitry

from trigger circuitry

Workshop on the Applications of Compton Camera - Baia delle Zagare, 5-7 settembre 2002.

Probe architecture

1st lev.2nd lev.

to PC

to PC

Read-out clock:

fck=160kHz

Trigger from fast OR circuitry

Workshop on the Applications of Compton Camera - Baia delle Zagare, 5-7 settembre 2002.

Probl. in deep sub-. tech.

• Stat. fluctuations of the FE performances.• Mismatch problems beween circuit replicas

(both intra-chip and inter-chip) at extr. low currents.

• Need of a robust design of the circuitry against process par. fluctuations.

Workshop on the Applications of Compton Camera - Baia delle Zagare, 5-7 settembre 2002.

CSA solutions• Adaptive Ileak canc. (Krummenacker);

VDD

RB

VDD

Irif

Ip

0

Workshop on the Applications of Compton Camera - Baia delle Zagare, 5-7 settembre 2002.

• Adaptive P-Z canc. (Rehak et al.)

Iin Ct

Cf

Mf

Vfp

Mx

Cx

Cy

My Mz

Cz

VoutRyz

Vyz

preamplifier shaper

CSA solutions (cont’d)

Workshop on the Applications of Compton Camera - Baia delle Zagare, 5-7 settembre 2002.

• Adaptive Vfp bias

Workshop on the Applications of Compton Camera - Baia delle Zagare, 5-7 settembre 2002.

• Adaptive Vfp bias

Workshop on the Applications of Compton Camera - Baia delle Zagare, 5-7 settembre 2002.

Some exp. result on the adaptive P-Z CSA

• CSA in 0.8 m CMOS for SDD (spectroscopy)

External shaper

Internal shaper (adaptive pole-zero canc.)

Workshop on the Applications of Compton Camera - Baia delle Zagare, 5-7 settembre 2002.

Provisional conclusions and workplan

• Preliminary experiments with A250 (Amptek) FE;

• use of the adaptive P-Z CSA;• design and fab. of first prototypes of CSA

in deep submicron CMOS;• electr. and stat. characterization of prot’s.