Valeria Speziali

Review of the development of diamond radiation sensors

Abstract Diamond radiation sensors produced by chemical vapour deposition are studied for the application as tracking detectors in high luminosity experiments. Sensors with a charge collection distance up to 250 μm have been manufactured. Their radiation hardness has been studied with pions, proton and neutrons up to fluences of 1.9×10 15 π cm −2 , 5×10 15 p cm −2 and 1.35×10 15 n cm −2 , respectively. Diamond micro-strip detectors with 50 μm pitch have been exposed in a high-energy test beam in order to investigate their charge collection properties. The measured spatial resolution using a centre-of-gravity position finding algorithm corresponds to the digital resolution for this strip pitch. First results from a strip tracker with a 2×4 cm 2 surface area are reported as well as the performance of a diamond tracker read out by radiation-hard electronics with 25 ns shaping time. Diamond pixel sensors have been prepared to match the geometries of the recently available read-out chip prototypes for ATLAS and CMS. Beam test results are shown from a diamond detector bump-bonded to an ATLAS prototype read-out. They demonstrate a 98% bump-bonding efficiency and a digital resolution in both dimensions.

Radiation hardness studies of CVD diamond detectors

Abstract The inherent properties of diamond make it an ideal material for tracking detectors especially in the high rate, high radiation environments of future colliders such as the LHC. In order to survive in this environment, detectors must be radiation hard. We have constructed charged particle detectors using high quality CVD diamond and performed radiation hardness tests on them. The signal response of diamond detectors to ionizing particles is measured before and after irradiation. Diamond detectors have been exposed to 60 Co photons at Argonne National Laboratory, 300 MeV/ c pions at PSI, 500 MeV protons at TRIUMF and 5 MeV alpha particles at Los Alamos National Laboratory. The results show that CVD diamond is an extremely radiation hard material well suited for particle detector production.

Evolution in the criteria that underlie the design of a monolithic preamplifier system for microstrip detectors

Abstract Several steps through which the design of a monolithic preamplifier system for microstrip detectors has passed, are critically analyzed. From the very initial MOSFET version, several measures were gradually taken with the purpose of reducing noise. The latest design criteria aim at realizing a preamplifier system which, besides outstanding noise performances, features also a suitable degree of radiation tolerance.

Impact of Lateral Isolation Oxides on Radiation-Induced Noise Degradation in CMOS Technologies in the 100-nm Regime

Degradation mechanisms associated to lateral isolation oxides are discussed to account for total ionizing dose effects on the noise performance of 90 nm and 130 nm CMOS devices and for their dependence on geometry and operating conditions. In NMOSFETs with a conventional open layout, after irradiation the parasitic transistor at the device edges turns on and contributes to the total device noise. The paper provides a model to help understanding the impact of this radiation-induced noise contribution on white and 1/f noise terms. The different behavior of NMOSFETs in the two examined technology nodes is analyzed in this framework, and design criteria to reduce noise degradation in irradiated devices are discussed.

Recent results from the RD42 Diamond Detector Collaboration

Abstract Diamond, as the hardest material known, has an extremely high binding energy suggesting that it will be a radiation hard material. Given that it is also a semiconductor, one is led to believe that diamond might perform well as a high resolution semiconductor tracking detector in very hostile radiation environments in which more conventional detectors would fail. In this paper we, the RD42 Diamond Detector Collaboration, review the progress that we have made in the development of chemical vapor deposition (CVD) diamond as a detector material, its radiation hardness, and the performance we have achieved with diamond tracking detectors.

Radiation hardness perspectives for the design of analog detector readout circuits in the 0.18-/spl mu/m CMOS generation

This paper presents a study of the ionizing radiation tolerance of analog parameters of 0.18-/spl mu/m CMOS transistors, in view of the application to the design of front-end integrated circuits for detectors in high-energy physics experiments. Static, signal, and noise performances of devices with various gate dimensions were monitored before and after irradiation up to a 300-kGy(Si) total dose of /sup 60/Co /spl gamma/-rays. Different device biasing conditions under irradiation were used, and the relevant results are discussed. A comparison with previous CMOS generations is carried out to evaluate the impact of device scaling on the radiation sensitivity.

Total ionizing dose effects on the noise performances of a 0.13 /spl mu/m CMOS technology

This paper presents a study of the ionizing radiation tolerance of 0.13 /spl mu/m CMOS transistors, in view of the application to the design of rad-hard analog integrated circuits. Static, signal and noise parameters of the devices were monitored before and after irradiation with /sup 60/Co /spl gamma/-rays at a 10 Mrad total ionizing dose. The effects on key parameters such as threshold voltage shift and 1/f noise are studied and compared with the behavior under irradiation of devices in previous CMOS generations.

Survey of noise performances and scaling effects in deep submicrometer CMOS devices from different foundries

Submicrometer CMOS technologies provide well-established solutions to the implementation of low-noise front-end electronics for a wide range of detector applications. Since commercial CMOS processes maintain a steady trend in device scaling, it is essential to monitor the impact of these technological advances on the noise parameters of the devices. In this paper we present the results of an extensive analysis carried out on CMOS transistors fabricated in 0.35, 0.25, and 0.18 mum technologies from different foundries. This allows us to evaluate the behavior of 1/f and channel thermal noise parameters with different gate oxide thickness and minimum channel length and to give an estimate of their process-to-process spread. The experimental analysis is focused on actual device operating conditions in monolithic detector readout systems. This means that moderate or weak inversion are often the only relevant regions for front-end devices. To account for different detector requirements, the noise behavior of devices with different geometries and input capacitance was investigated. The large set of data gathered from the measurements provides a powerful tool to model noise parameters and establish front-end design criteria in deep submicrometer CMOS processes

Monolithic preamplifier employing epitaxial n-channel JFETS

Abstract This paper reports the results obtained in the research program oriented to the realisation of a monolithic preamplifier for calorimetry applications at high luminosity colliders. The main purpose of the program is to arrive at a monolithic realisation with a performance as close as possible to that of discrete preamplifiers. The junction field-effect transistors employed in discrete preamplifiers have an epitaxial channel and a very heavily doped gate diffused onto it. They present the best noise and radiation tolerance characteristics. The first step in the program implementation was, accordingly, the search for a process able to make the integration of epitaxial-channel JFETs on a monolithic substrate possible. The integration has been accomplished on the basis of a buried-layer approach to device isolation. Individual JFETs and a complete preamplifier employing only n -channel JFETs have been realised. The characterisation of the individual devices has shown that their behaviour in terms of small signal and noise parameters is very close to that of their discrete equivalents. This result, along with the very good noise performance of the preamplifier, seems to point out that the buried layer process has fulfilled the task for which it was developed.

Short channel, CMOS-compatible JFET in low noise applications☆

Abstract An N-channel JFET with 1.6 μm gate length has been realised in the CMOS-compatible technology. Such a device is intended as the basic front-end element in the development of new low noise circuits of large bandwidth. This paper presents the results of a full device characterisation concerning small signal behaviour, noise spectral densities and noise sensitivities to absorbed radiation. The performances of some monolithic circuits employing the short channel JFET as an input element, among them preamplifiers tailored to different detector capacitances, an entire analog processor for microstrip detectors and a multichannel preamplifier system are discussed.