Design, simulation and characterization of thin silicon microstrip detectors

COFIN 2005 Dalla Betta DIT-PRJ-06-012

Status NOT active project
DISI role Partner
Project type Research Project
Dimension National
Acquisition date 2005-12-23
Start date 2006-01-30
End date 2008-01-30

Project details

Project astract The aim of this research program is to fabricate a monolithic active pixel sensor (MAPS) based on a triple-well commercial CMOS process and to develop the technology for the fabrication of thin silicon strip detectors. The MAPS will be readout digitally and connected to an associative memory board to demonstrate triggering capability. These devices represent some of the building blocks<br/>that could improve the performance of pixel and strip silicon detectors for future particle physics experiments at low and medium energy, such as a Super B Factory and the Linear Collider, where momentum resolution, amount of material, and rate capability are of paramount importance.<br/><br/>The proponents have successfully realized in the past (PRIN 1999 and 2001) silicon strip detectors with integrated electronics, and, more recently (PRIN 2003), monolithic pixel cells based on ST 0.13um CMOS triple-well technology, with fully integrated on-pixel preamplifier, shaper, discriminator and latch. The proponents also have extensive experience in the design, construction, and operation of secondary vertex trigger systems based on associative memories.<br/><br/>In this program the proponents plan to pursue two lines of research:<br/>1) fabricate small (16x16) MAPS matrices based on commercial CMOS triple-well technology, optimizing the elementary cell both in terms of geometry and electrical response, evaluating different potentially suitable commercial technologies (ST and IBM), and developing a matrix readout architecture suited for interfacing to an existing associative memory system.<br/>2) develop the technological potential for fabricating thin (50-100um) microstrip detectors, focusing on two promising techniques: a) epitaxially grown substrates, and b) locally thinned substrates. The group has a long collaboration history with ITC-Irst in Trento where the wafers will be processed.<br/><br/>The proponents plan to test the fabricated devices with IR laser and charged particles, and measure the effect of electron, photon, and hadron irradiation on their performance. 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.
Fundings 450000 €
Partners
  • DIT - UniTN
  • University of Pisa
  • University of Pavia
  • University of Bergamo
  • University of Trieste

DISI Sub-project details

Project astract The Research Unit (RU) of DIT - University of Trento will be involved only in the research line on strip detectors on thin silicon, focusing the attention on the process and design aspects for both the possible technological approaches (epitaxial substrates and FZ substrates locally thinned by means of bulk micromachining techniques). The activity will be carried out in tight cooperation with the Research Unit of Trieste as far as the detector design and characterization (electrical and functional) is concerned. Moreover, the RU will also support the activity of the Research Units of Bergamo and Pavia,<br/>providing them with experimental data and behavioral models of the detectors, to be used for the evaluation of the limits of the existing read-out chips (BTeV, VA, etc.) and for the study of the most promising technologies for the design of new chips, among them 90-nm CMOS and SiGe BiCMOS processes.<br/>The specific tasks of RU are summarized in the following.<br/>1) In cooperation with the RU of Trieste, the RU will initially work at the design and layout drawing for the detectors of the first batch, to be fabricated on epitaxial substrates of different thickness (in the range 50-100 micrometers).<br/>2) In parallel, from the beginning, the RU will contribute to the technological studies carried out at ITC-irst on substrate local thinning by TMAH, and aimed at investigating:<br/>- the extension of this thinning technique, so far used for small devices (~1cm2), to the fabrication of large area detectors;<br/>- the feasibility of this technique for double-sided detectors by means of a local thinning carried out in a symmetric way from both sides of the wafer;<br/>- the robustness of thin structures against post-process shocks (e.g., due to bonding), as required in order for these detectors to be reliably used in a tracking systems.<br/>3) During the period of fabrication of the first batch, with the aid of numerical device simulations (DESSIS software), the RU will carry out a thorough study of the performance of thin detectors as a function of the main technological parameters (substrate resistivity, oxide charge, carrier generation lifetime) and geometrical dimensions (thickness, pitch, width). At first, this simulation activity will deal with aspects that are common to both the technologies (epitaxial and locally thinned substrates); later, it will be focused mainly on those aspects peculiar to locally thinned detectors, in order to optimize the design of these devices. <br/>4) When the production of first batch will be completed, the RU will carry out an extensive electrical characterization of test structure and strip detectors (on-wafer).<br/>5) On the basis of the simulation results and of the experimental results from the first batch, the RU will complete the design phase of the second batch drawing the layout of the detectors, to be fabricated on TMAH thinned substrates of different thickness (in the range 50-100 micrometers).<br/>6) On a selected set of test structures and strip detectors of the first batch, dynamic electro-optical tests will then be performed by using an IR pulsed Laser, in order to evaluate the signal amplitude, the charge collection time and the charge efficiency.<br/>7) It is also planned to irradiate detectors with high-energy electrons (at ELETTRA Synchrotron) and with neutrons, protons and Li ions at different facilities available through the CERN RD-50 Collaboration, and to repeat the electrical and functional tests on detectors irradiated up to high particle fluences. <br/>8) At each measurement stage, the results of the electrical, electro-optical and functional characterization will be compared to those predicted by DESSIS simulations.<br/>9) The above described experimental activity and the comparison with simulation results will then be carried out on the detectors and test structures of the second batch.<br/>10) Finally, a critical evaluation of the overall results will be accomplished.
Keywords Strip detectors, TMAH thinned substrates, epitaxial substrates
Fundings 68000 €
Manager Gian Franco Dalla Betta
Participating RP