Design and characterization of pixel detectors with integrated electronics on high resistivity silicon

COFIN 03 Dalla Betta - MAPS DIT-PRJ-04-012

Status NOT active project
DISI role Partner
Project type Research Project
Dimension National
Acquisition date 2003-10-15
Start date 2004-01-01
End date 2005-12-31
SAP code 40100656

Project details

Project astract The aim of this research program is the development of detectors for ioinizing particles and X-rays in the 10-30 keV range based on monolithic active pixels with integrated electronics (MAPS). These detectors have very interesting applications in elementary particle experiments and in medical and industrial imaging.<br/>The proponents have successfully developed in the past (PRIN 1999 and 2001) silicon strip detectors with similar goals. The need to use pixels arises when the experiment requires charge particle tracking systems with good space resolution and fast readout rate in high multiplicity events; in imaging applications, the integration of the electronics allows the construction of simpler and more reliable systems compared to other technologies.<br/>The proponents plan to realize MAPS using two different technologies:<br/>1) a fabrication process developed in the past years in collaboration with IRST in Trento, that allows the integration of JFET,MOSFET and bipolar devices on high resistivity substrate;<br/>2) a standard deep submicron CMOS process in which tiny electrodes collect, via diffusion, the small charge released in the undepleted. low resistivity substrate.<br/>This research program has the goal of integrating the analog signal processing elements (preamplifier, shaper) at the pixel level for both technologies and test the fabricated devices with IR laser, X-rays, and charged particles.<br/>The fabrication of these devices represents a goal of great interest in the field of semiconductor devices, and provides a powerful and refined instrument for the experimental study of fundamental interactions.
Keywords SILICON DETECTORS ; PIXEL DETECTORS ; FIELD EFFECT DEVICES ; INTEGRATED SENSORS ; MEDICAL AND INDUSTRIAL IMAGING ; CHARGED PARTICLES TRACKING
Fundings 438500 €
Partners
  • University of Pavia
  • University of Bergamo
  • University of Pisa
  • University of Modena e Reggio Emilia
  • University of Trieste

DISI Sub-project details

Project astract DIT will be involved in the first research line only. In radiation detectors made on<br/>high resistivity silicon, the active volume (generally fully depleted) corresponds to the entire substrate thickness, allowing for a good detection efficiency also for X-rays in the energy range 20-40 keV. This property is particularly important for those<br/>applications in the medical field (e.g., mammography), for which the detector thickness can be suitably increased up to 600-800 micrometers in order to achieve a high detection efficiency. Nevertheless, transistors with a minimum feature size in the order of few micrometers can be fabricated with this process, resulting in dynamic performance that are good enough for the read-out of tracking detectors for low rate charged particles (e.g., in astro-physics applications), yet not adequate to most of high energy physics<br/>experiments.<br/><br/>The activity will be concerned with the design, simulation, and characterization of active pixel detectors based on JFETs,<br/>MOSFETs and bipolar transistors integrated on high resistivity silicon by using the technology available at ITC-IRST and developed in cooperation with the proponents within the framework of PRIN 1999 e PRIN 2001 projects. The considered technological process is adequate to the realization of good quality detectors and transistors, but features at present only one metal level and one polysilicon level. In order to increase the design flexibility of this technology and the integration density, so as to implement compact read-out circuits matching the dimensions of the pixels (in the order of 100-200 micrometer), a second level of metal will be introduced in the technology. In this optimized technology, two batches of detectors will be fabricated: the first one will be produced on 300 micrometer thick substrates (standard thickness for radiation detectors), whereas the second one will be produced on thicker (600-800 micrometer) substrates, that are suitable for applications in the medical field such as mammography. The active pixels will include integrated transistors acting both as a detector and as the first amplification device. In particular, different solutions will be analysed, based on JFETs (triode and tetrode) and on MOSFETs, either in the source-follower or in the<br/>charge amplifier configuration. In fact, the p-well/n-substrate junction of these transistors can be used as detecting electrode and modulate the device current as a result of the voltage variations induced on it by the collected charge. Different charge reset (clear) techniques will be investigated for the pixels, this operation being required in order to avoid saturation phenomena caused by both the signal charge and the leakage current. Several pixel concepts will be implemented on silicon both as single test structures and as the basic element of 8x8 arrays, for which the signal read-out will be carried out serially, addressing one row at a time and including at each column edge a complete read-out channel (amplifier, shaper, discriminator) so as obtain a binary signal. In<br/>cooperation with the Research Units of Modena and Trieste, pixel implementations based on bipolar phototransistors as detecting element and MOSFETs/JFETs for the addressing and read-out circuitry will be considered.
Keywords SILICON PIXEL DETECTORS ; READ-OUT ELECTRONICS ; INTEGTRATED SENSORS ; FIELD-EFFECT DEVICES
Fundings 74300 €
Manager Gian Franco Dalla Betta
Participating RP