W. Kucewicza, A. Bulgheronib, M. Cacciab, P. Grabiecc, J. Marczewskic, H.Niemieca

a AGH-Univ. of Science and Technology, Al. Mickiewicza 30, 30-059 Krakow, Polandb Universita’ dell’Insubria, via Valleggio 11, 22100 Como, Italy

c Institute of Electron Technology, Al. Lotnikow 32/46, 02-668 Warsaw, Poland 

This R&D has been undertaken within the SUCIMA project (Silicon Ultra Fast Camera for Gamma and Beta Sources in Medical Applications), supported by European Commission within 5-th Framework Program. One of its goals is the development of a monolithic sensor optimised for medical imaging applications, especially dosimetry of radioactive sources for brachytherapy and beam monitoring for hadrontherapy.

 Keywords: silicon detector, active pixel detector, SOI technology

Development of Development of Monolithic Active Pixel Monolithic Active Pixel

Detector in SOI Detector in SOI TechnologyTechnology

Advantages of Advantages of the the SOI detectorsSOI detectors

As a monolithic device eliminates bump-bonding process and allows reduction of total sensor thickness reduction of multiple scatteringAllows using high resistive detector substrates and operation in

fully depleted region good detection efficiency, enables detection of particles with limited range in the silicon without backthinning processGives possibility to use both type of transistors in readout

channels increased flexibility of the design, design optimisation for different application

The SOI sensor may merge the advantages of the monolithic and hybrid detectors

Principle of SOI monolithic Principle of SOI monolithic detectordetector

The idea: Integration of the pixel detector and readout electronics in the wafer-bonded SOI substrate Detector support layer

High resistive (> 4 kcm,FZ)

300 m thick Conventional p+-n DC-coupled

Electronics device layer Low resistive

(9-13 cm, CZ) 1.5 m thick Standard CMOS technology

Tests with laser light and ionising Tests with laser light and ionising particles particles

W.Kucewicz SUCIMA 4

Sensitivity to laser lightGood linear response as a function of the charge generated by laser pulses (1 pulse corresponds to 3 MIP charge)

Sensitivity to beta particles Red histogram and line indicate cluster noise and its Gaussian fit, blue histogram and line indicate the signal from 90Sr beta source and its Landau fit

Sensitivity to alfa particles (short range particles)The average cluster pulse hight corrensponds to 25 MIP

Applications of the SOI detectorsApplications of the SOI detectors

SOI detectors: High charge signals corresponding to

minimum ionising particles (about 22000 e+e-), fully depleted

Attractive solutions for low energy radiation detection

Monolithic, flexibility of the readout electronics design (NMOS and PMOS in readout channel)

Possible option for vertex detectors

One of possible applications:Beam monitor in hadrontherapy

System basing on secondary electrons emission from a thin aluminium foil.

Kinetic energy of electrons = 20 keV particle range in silicon = 3 m

Detection of such electrons is possible in SOI detector without any backthinning process.

Beam monitor

Fully functional SOI detectorFully functional SOI detector in in production production

Optimised for medical imaging applications and high particle fluxOptimised for medical imaging applications and high particle flux Dimensions: 24x24 mm2, 128 x 128 = 16 384 channelsDimensions: 24x24 mm2, 128 x 128 = 16 384 channels 4 sub-segments with independent parallel analogue outputs4 sub-segments with independent parallel analogue outputs Cell dimensions: 150 Cell dimensions: 150 m x 150 m x 150 m m Signal per MIP: ~6 mV; Dynamic range: 300 MIPSignal per MIP: ~6 mV; Dynamic range: 300 MIP The basic detectors may be extended to the ladder, but with small dead area betweenThe basic detectors may be extended to the ladder, but with small dead area between

Functionally Functionally independent quarter independent quarter

of the detectorof the detector

9.6 mm

9.6 mm

Matrix of channels

Digital blocks

9.6 mm

9.6 mm

Matrix of channels

Digital blocks

66

ConclusionsConclusions

An alternative solution of a monolithic active pixel detector, which allows efficient detection in high resistive substrate, has been proposed.First small area SOI pixel sensors have been fabricated.Preliminary tests with a laser light and a radioactive source

have indicated detector sensitivity for the ionising radiation. Satisfactory results of the tests of the small readout matrices

on the SOI test structures and prototype chips are a starting point for the design of the fully functional and large area SOI sensor.The layout and readout scheme of the detector with the

active area of 2 cm x 2 cm and consisting 4 independent by operation sub-segments has been proposed .The realization of the final SOI sensor will be completed this

year.