Francesco Moscatelli, Andrea Scorzoni

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INFN - Consiglio di Sezione 12/7/05

Università degli StudiUniversità degli Studi di Perugiadi Perugia

First characterizations of a minimum ionizing particle detector

based on p+n junction SiC diode

Francesco Moscatelli, Andrea ScorzoniDIEI and INFN, University of Perugia, via G. Duranti 93, 06125 Perugia, Italy

in collaborazione conCNR- IMM Sezione di Bologna, via Gobetti 101, 40129 Bologna, Italy

Dipartimento di Fisica, Polo Scientifico di Sesto Fiorentino,Via Sansone 1 Firenze Italy

Institut für Kristallzüchtung, D-12489 Berlin, Germany.

This work was supported by the INFN SiCPOS project

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Outline

• Introduction• Technological process and mask design• I/V - C/V measurements and annealing

effects• CC setup and measurements• Irradiation with 1 MeV neutrons• Conclusions and future developments

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A bit of history

• November 2003: first process. Breakdown of the wafer during the last annealing.

• June 2004: First process repeated. The process has been brought to completion. Unfortunately the surface of the wafer was everywhere p-type instead of n-type. Reason: low doping epi process at IKZ.

• Fine 2004: Second process (with new mask set).

• 2003: IV, CV, DLTS and CCE on IMM samples.

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Plan of activity - 2005

– Good quality of process verified with IV, CV and CC measurements on unirradiated devices in early 2005

– Irradiation with neutrons May 8 2005– Measurements on irradiated devices in June and July

(in progress)

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SiC Process: p+/n

Ion implantationAl+ @ 300°Cp+ doping (0.4 m) = 41019 cm-3

p- doping (0.6 m) = 51017 cm-3

Annealing 1600°C 30 min

Front:Al (350 nm) / Ti (80 nm) depositionBack: Ni

Epi (55 m) doping:

2 1014 cm-3

Annealing 1000°C in vacuum 2 min

n

n+

Annealing 430°C in nitrogen 30 min

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Mask designDiode

Diameter (m)

JTE (m)

D1 250 200

D2 400 200

D3 600 200

D4 800 200

D5 1000 200

D6 400 No

D7 150 No

S1 400 No

31 diodes in each die

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Wafer

• 4 quarters. Rows from E to N

• Columns from 4 to 9• Columns 4, 8 (no J8

and k8) and 9 show p-type layer under the Schottky contacts

4 5 6 7 8 9

E

F

G

H

I

J

K

L

M

N

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I-V measurements on p+/n diodes

• Before annealing at 430°C, 70 % of diodes have good I-V curves (considered colums 5, 6, 7 and dies J8 and K8)

• Theoretical limit for this device 6 kV

p+p-

Ti-Al

n+

n

Ni

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Reverse current: effect of annealing at room temperature

and at 430°C

0 20 40 60 80 100

1x10-12

1x10-11

1x10-10

D3C J8

Cu

rre

nt [

A]

reverse Voltage [V]

Giu29 Ann 450°C Giu21 May25 May11 Apr26 Apr13

Defects anihilate at room T. The process is accelerated at 430°C

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CV measurements

• The depletion voltage is near 220-250 V

• Epi doping not uniform (average value 21014 cm-3)

0 10 20 30 40 501E13

1E14

1E15

Do

pin

g C

on

cen

tra

tion

[cm

-3]

Depth [m]

0 200 400 600 800 1000

1x10-12

2x10-12

3x10-12

Cap

acit

ance

[V

]

Reverse bias [V]

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CC measurements and irradiation

• Reference with CC measurements without irradiation

• 7 dies for irradiation with neutrons

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CCE measurement setup

Amptek

S+PM trigger

Acquisition system

90Sr 0.1mCi

The noise of the charge collection setup is linearly proportional to the capacitance of the detector and is given by ENC=200e+4.6e/pF

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CC measurements

-3000 0 3000 6000 9000 12000

0

100

200

300

400

500

Co

unt

s

Channel (e)

measurements convolution

Landau and Gaussian

• Signal distribution (Landau) well separated from noise (Gaussian)

• At about 250 V the Landau distribution does not change full depletion

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CC vs V

• Around 200-250 V the signal saturates, in good agreement with CV results.

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Irradiation with neutrons

• Irradiation with 7 different fluences in the range 1014-1016 1 MeV neutrons/cm2 carried out May 8 in Ljubiana

• Fluences: 11014 n/cm2, 31014 n/cm2, 71014 n/cm2 , 1.51015 n/cm2, 31015 n/cm2, 71015 n/cm2, 11016 n/cm2

• We are keeping the diodes at –5°C in order to make possible the analysis of annealing effects at RT

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First IV results on irradiated devices

Before irradiation

After irradiation

• At a fluence of 31014 n/cm2 the junction disappeared. The n-type material becomes intrinsic

• The reverse and forward current are comparable

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Conclusions• p+/n junctions have been realized and electrically

characterized. Good forward and reverse characteristics have been obtained

• CC experimental results on unirradiated SiC pn junctions: 3000 e- at 200 V

• Irradiation with 7 different fluences in the range 1014-1016 1 MeV neutrons/cm2

• Preliminary results on irradiated samples

• Measurements on irradiated samples

Future developments

Francesco Moscatelli, Andrea Scorzoni

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