W. Kucewicz a, A. A.Bulgheroni b, M. Caccia b, P. Grabiec c, J. Marczewski c, H.Niemiec a a AGH-Univ. of Science and Technology, Al. Mickiewicza 30, Krakow, Poland b Universita’ dell’Insubria, via Valleggio 11, Como, Italy c Institute of Electron Technology, Al. Lotnikow 32/46, 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 Monolithic Active Pixel Detector in SOI Technology

Advantages of the SOI detectors  As a monolithic device eliminates bump-bonding process and allows reduction of total sensor thickness  reduction of multiple scattering  Allows 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 process  Gives 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 detector The idea: Integration of the pixel detector and readout electronics in the wafer-bonded SOI substrate Detector  support layer High resistive (> 4 k  cm,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 particles W.KucewiczSUCIMA 4 Sensitivity to laser light Good 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 90 Sr 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 detectors SOI detectors: High charge signals corresponding to minimum ionising particles (about 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 detector in production Optimised for medical imaging applications and high particle flux Optimised for medical imaging applications and high particle flux Dimensions: 24x24 mm2, 128 x 128 = channels Dimensions: 24x24 mm2, 128 x 128 = channels 4 sub-segments with independent parallel analogue outputs 4 sub-segments with independent parallel analogue outputs Cell dimensions: 150  m x 150  m Cell dimensions: 150  m x 150  m Signal per MIP: ~6 mV; Dynamic range: 300 MIP Signal per MIP: ~6 mV; Dynamic range: 300 MIP The basic detectors may be extended to the ladder, but with small dead area between The basic detectors may be extended to the ladder, but with small dead area between Functionally independent quarter of the detector 6

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.