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A new version of the CLARO8 ASIC has been designed in AMS 0.35 μm CMOS technology, based on radiation hardened by design cells, and extensively tested. Results on the complete radiation hardness characterization are presented. more...

Radiation hardness tests of the CLARO8 ASIC, designed in AMS 0.35micron CMOS technology for the upgrade of the CERN LHCb RICH detectors, are presented, including measurements of total- ionizing dose and single event effects. more...

An 8-channel front-end ASIC has been designed in 0.35 micron CMOS technology for the upgrade of the LHCb RICH detectors at CERN. The chip allows fast single-photon counting up to 40 MHz, with a peaking time of 5 ns and a power consumption of about 1 mW per channel. Results of the characterisation of the first version of the chip are presented, including measurements in the lab with a dedicated test system. Radiation hardness tests are described as well, including measurements of total-ionising dose and single event effects. more...

We report on the electrical behavior of termination structures for silicon diodes irradiated with high-energy particles. In particular, the analysis is focused on samples featuring an all-P-type (APT) termination structure that has already been proved to yield excellent long-term stability performance. The radiation hardness of these structures is compared to that of more common reference devices. In order to characterize various radiation conditions, tests were performed using protons, neutrons, and high-energy electrons with different fluences up to values causing substrate type inversion. We verified that the APT samples remain functional in all the considered situations, their operational limit being comparable to that of the other devices. more...

Single photon avalanche diodes (SPADs) have been recently studied as photodetectors for applications in space missions. In this presentation we report the results of radiation hardness test on large area SPAD (actual results refer to SPADs having 500 mu m diameter). Dark counts rate as low as few kHz at -10 degrees C has been obtained for the 500 mu m devices, before irradiation. We performed bulk damage and total dose radiation tests with protons and gamma-rays in order to evaluate their radiation hardness properties and their suitability for application in a Low Earth Orbit (LEO) space mission. With this aim SPAD devices have been irradiated using up to 20 krad total dose with gamma-rays and 5 krad with protons. The test performed show that large area SPADs are very sensitive to proton doses as low as 2 x 10(8) (1 MeV eq) n/cm(2) with a significant increase in dark counts rate (DCR) as well as in the manifestation of the "random telegraph signal" effect. Annealing studies at room temperature (RT) and at 80 degrees C have been carried out, showing a high decrease of DCR after 24-48 h at RT. Lower protons doses in the range 1-10 x 10(7) (1 MeV eq) n/cm(2) result in a lower increase of DCR suggesting that the large-area SPADs tested in this study are well suitable for application in low-inclination LEO, particularly useful for gamma-ray astrophysics. (c) 2013 Elsevier B.V. All rights reserved. more...

Radiation hardness of planar detectors processed from pre-irradiated and thermo-annealed n-type FZ silicon substrates, and standard FZ as a reference, was studied. The high purity n-Si wafers with carrier concentration 4.8×10 11 cm −3 were pre-irradiated in Kiev's nuclear research reactor by fast neutrons to fluence of about 10 16 neutrons/cm 2 and thermo-annealed at a temperature of about 850 °C. Silicon diodes were fabricated from standard and pre-irradiated silicon substrates by IRST (Italy). All diodes were subsequently irradiated by fast neutrons at Kiev and Ljubljana nuclear reactors. The dependence of the effective doping concentration as a function of fluence ( N eff =f ( Φ )) was measured for reference and pre-irradiated diodes. Pre-irradiation of silicon improves the radiation hardness by decreasing the acceptor introduction rate ( β ), thus mitigating the depletion voltage ( V dep ) increase. In particular, β in reference samples is about 0.017 cm −1 , and for pre-irradiated samples is about 0.008 cm −1 . Therefore, the method of preliminary irradiation can be useful to increase the radiation hardness of silicon devices to be used as sensors or detectors in harsh radiation environments. more...

Radiation hardness of silicon detectors based on thin epitaxial layer on Czochralski (CZ) substrate for the LHC upgrade (Super-LHC) was studied. No type inversion was observed after irradiation by 24 GeV/c protons up to the fluence of 1016 p/cm2 due to overcompensating donor generation. After long-term annealing (corresponding to 500 days at room temperature) proton irradiated devices show a decrease of the effective doping concentration and then undergo type inversion. Measurements confirm that thin epitaxial devices on CZ substrate could be used for innermost layers of vertex detectors in future experiments at the Super-LHC. more...

We studied the response of a commercial 0.13-mum CMOS technology to high-energy (24-GeV) proton irradiation, which emulated the environment the front-end electronics of future high-energy accelerators will have to operate in, for fluences up to 1016 p/cm2 . After irradiation, large negative shifts in the threshold voltage and large drops in the maximum transconductance were observed in PMOSFETs, whereas comparatively smaller effects were present in NMOSFETs. Furthermore, both kinds of devices exhibited an increase in the drain off-current and in the gate leakage current. All the observed effects were roughly proportional to the proton fluence. For the PMOSFETs only, the amount of the degradation depended on the device channel length. The changes in the characteristics of the irradiated devices were attributed to the build-up of positive charge in the LDD spacer oxide and to the creation of defects in the gate oxide more...

In this work, we have focused our attention on MOSFETs, which are the real basic elements of all CMOS applications. We have studied the immediate and latent effects produced by heavy ion irradiation on MOSFETs with ultrathin gate oxide, even after electrical stresses subsequent to irradiation. We found that a single ion can generate a physically damaged region (PDR) localized in the Si-SiO/sub 2/ interface, which may hamper the surface channel formation. In order to generate a PDR the ion hit must be close enough to MOSFET borders, i.e., in correspondence with the STI or the LDD spacer. Consequently, if both MOSFET W and L are large enough only few ion hits may give place to a PDR, mitigating the radiation damage. Finally we have developed an original model to describe the impact of the PDR on channel conductance in the ohmic linear region. On the basis of this model, we predict a PDR size around 0.2-1 /spl mu/m. more...

The results discussed in this paper are relevant to junction field effect transistors (JFETs) and JFET-based charge sensitive amplifiers fabricated in a detector compatible process. Such structures were irradiated with 27 MeV protons to evaluate the suitability of the technology for space applications and high-energy physics experiments from the standpoint of radiation tolerance. The process investigated in this work, originally designed for the fabrication of silicon detectors to be operated in a fully depleted condition, has been tuned to embed N-channel JFETs, NMOS devices and bipolar transistors in the same high resistivity substrate. The most significant electrical parameters have been monitored after exposing the test structures to different proton fluences in order to characterize their total dose and bulk damage response. Comparison with the results from previous irradiations with /spl gamma/-rays might be helpful in shedding light on the fundamental mechanisms underlying radiation damage in JFET silicon devices. more...

Diodes manufactured on a thin and highly doped epitaxial silicon layer grown on a Czochralski silicon substrate have been irradiated by high energy lithium ions in order to investigate the effects of high bulk damage levels. This information is useful for possible developments of pixel detectors in future very high luminosity colliders because these new devices present superior radiation hardness than nowadays silicon detectors. The reverse current increase, the variation of the depletion voltage, and their annealing characteristics, as well as the charge collection properties, are presented and discussed. more...

Silicon diodes processed on standard and oxygenated silicon substrates by three different manufacturers have been irradiated by neutrons in a nuclear reactor. The leakage current density ( J D ) increase is linear with the neutron fluence. J D and its annealing curve at 80°C do not present any sizeable dependence on substrate oxygenation and/or manufacturing process. The acceptor introduction rate ( β ) of the effective substrate doping concentration ( N eff ) is independent from the oxygen concentration when standard and oxygenated devices from the same manufacturer are considered. On the contrary, β significantly varies from one manufacturer to another showing that the β dependence on the particular process can be important, overtaking the small substrate oxygenation effect. Finally, the average saturation value of the N eff reverse annealing is slightly lower for the oxygenated samples, pointing out a positive effect of the substrate oxygenation even for devices irradiated by neutrons. more...

Oxygenated and standard (not oxygenated) silicon diodes processed by CNM and IRST have been irradiated by 27 MeV protons and compared with standard devices from ST Microelectronics. As expected, the leakage current density increase rate (/spl alpha/) and its annealing do not show any significant dependence on starting material, oxygenation and/or device processing. On the contrary, oxygenation improves the radiation hardness by decreasing the acceptor introduction rate (/spl beta/) and mitigating the depletion voltage (V/sub dep/) increase, with the /spl beta/ parameter depending also on starting material and/or effects related to device processing for standard diodes. Finally, these results are included in a general review on the state of the art for silicon detector radiation hardening, confirming the good performance of the considered technologies. more...

Even though low voltage MOSFETs are fairly intrinsically robust to SEB, the high current pulses that arise in certain charge generating mechanisms may lead to circuit malfunction. In this work, for the first time, the current pulses induced by ion impacts in new generation commercial power MOSFETs are characterized by a statistical analysis. This approach allows us to evidence the existence, in these devices, of two different charge generation mechanisms. Furthermore, the capability to easily quantify these phenomena provides useful information for the design of circuits using these MOSFETs. The pulse shape and the total charge generated by the impact of an energetic ion are studied in relation to the energy and species of the ion and the applied voltage between drain and source. more...

Two silicon microstrip detectors, one fabricated from a standard and the second from a highly oxygenated substrate, were non-uniformly irradiated by 24 GeV protons to fluences ranging between 2.3 and 6.3×10 14 cm −2 . Charge collection efficiency measurements, performed by pulsing the detectors with a 1060 μ m wavelength laser, show that the beneficial effect of the oxygenation remains, although reduced with respect to that observed by C – V measurements on diodes fabricated with the detectors. more...

The CMS experiment at the LHC will comprise a large silicon strip tracker. This article highlights some of the results obtained in the R&D studies for the optimization of its silicon sensors. Measurements of the capacitances and of the high voltage stability of the devices are presented before and after irradiation to the dose expected after the full lifetime of the tracker. more...

Interstrip and backplane capacitances on silicon microstrip detectors with p+ strip on n substrate of 320 μm thickness were measured for pitches between 60 and 240 μm and width over pitch ratios between 0.13 and 0.5. Parametrisations of capacitance w.r.t. pitch and width were compared with data. The detectors were measured before and after being irradiated to a fluence of 4×10 14 protons / cm 2 of 24 GeV /c momentum. The effect of the crystal orientation of the silicon has been found to have a relevant influence on the surface radiation damage, favouring the choice of a 〈1 0 0〉 substrate. Working at high bias (up to 500 V in CMS) might be critical for the stability of detector, for a small width over pitch ratio. The influence of having a metal strip larger than the p+ implant has been studied and found to enhance the stability. more...

For the construction of the silicon microstrip detectors for the Tracker of the CMS experiment, two different substrate choices were investigated: A high-resistivity (6 k cm) substrate with (111) crystalorientation and a low-resistivity (2k cm) one with (100) crystalorientation. The interstrip and backplane capacitances were measured before and after the exposure to radiation in a range of strip pitches from 60 μm to 240 μm and for values of the width-over-pitch ratio between 0.1 and 0.5. more...

A large use of silicon microstrip detectors is foreseen for the intermediate part of the CMS tracker. A specific research and development program has been carried out with the aim of finding design layouts and technological solutions for allowing silicon microstrip detectors to be reliably used on a high radiation level environment. As a result of this work single sided, AC-coupled, polysilicon biased, 300 μ m thick, p + on n substrate detectors were chosen. Irradiation tests have been performed on prototypes up to fluence 2×10 14 n/cm 2 . The detector performances do not significantly change if the detectors are biased well above the depletion voltage. S / N is reduced by less than 20%, still enough to insure a good efficiency and space resolution. Multiguard structures has been developed in order to reach high voltage operation (above 500 V). more...

We report HSPICE simulation results of the signal propagation due to a minimum ionizing particle along the strips of single-sided microstrip detectors connected to the PreShape 32 read-out electronics. The capacitive detector parameter values have been determined as a function of the width/pitch ratio by using measured and calculated data which are available in literature. The strip load capacitance, i.e. the capacitance at the read-out electronics input due to the detector has been calculated by using HSPICE simulations. Different read-out configurations have been investigated. more...

We have investigated the degradation of tunnel oxides due to Fowler–Nordheim electron injection from polysilicon gate. Tested devices are n-MOSFET normally used for Flash EPROM applications with four different technologies for the tunnel oxide layer. Stresses have been performed at different source and drain bias conditions for a total injected charge up to 1 C/cm 2 . The oxide characteristics and degradation have been determined comparing the MOSFET threshold voltage and transconductance peak for as received devices and after each stress step. more...

The main DC and AC characteristics of AC-coupled polysilicon-biased silicon microstrip detectors have been measured in order to determine the set of SPICE parameters of these devices based on a RC network. For this purpose each strip has been divided in 200 unit cells and simulations with 5 and 9 strips have been performed. The model is capable of calculating the interstrip and coupling impedance and phase angle in good agreement with experimental results up to a frequency of 1 MHz. The electrical propagation of a current signal simulating the charge pulse of a ionising particle along the strips has been studied. The role of the input characteristics of the read-out electronics on the detector output signals has been addressed. The signal propagation has been studied also for anomalous working conditions of the detector, such as a strip with a break in the Al film, or disconnected from the read-out electronics. > more...

We study the possibility to use Single Photon Avalanche Diodes (SPADs) optically coupled to scintillating fibers as a novel type of gamma-ray detector for space applications. SPADs are silicon devices operating under polarization conditions above the junction breakdown voltage (typical overvoltage of 5V), for which a single photon interacting in the active region is sufficient to trigger a self sustainable avalanche discharge. SPADs can thus be used for the detection of very low light levels with an absolute timing accuracy of about 30 ps for single photon detection, without spectroscopic capabilities. In this presentation we report the preliminary results on large area SPAD (actual results refers to SPADs having 200 µm diameter, with the aim to grow up to 500 µm SPADs) coupled to scintillating fibers as the basic module for a particle tracker for space application. Dark counts rate as low as few tens of kHz at room temperature, lowering down to few kHz at −10°C have been obtained for the 200 µm devices, in accordance with the basic requirements for the proposed application. Similar instruments based on silicon photomultiplier (SiPM) readout have already been studied, but none based on SPAD has been realized up to now. Moreover, since very few information is available on SPADs for the use in a space environment, we performed bulk damage and total dose radiation tests with protons and gamma-rays in order to evaluate their radiation hardness properties and their suitability for application in a Low Earth Orbit (LEO) space mission. With this aim the SPAD devices have be irradiated using up to 20 krad total dose with gamma-rays and 5 krad with protons. more...

Radiation hardness of particle detectors based on thick epitaxial silicon layer (150 μm)has been studied in terms of operating voltage, leakage current and charge collection efficiency. The operability of such devices has been confirmed after irradiation with the fast hadrons beyond the equivalent 1 MeV neutrons fluence values of 1015cm−2. more...

The Fermilab Silicon Strip Readout (FSSR) chip is a 128-channel, mixed signal circuit, which was designed for processing the signals from the microstrip detectors of the BTeV experiment at the Tevatron collider. The design was carried out in a 0.25 mum CMOS technology, whose intrinsic radiation hardness is supposed to satisfy the application requirements. Such features were further improved by using radiation tolerant layout techniques. A prototype chip, including several variants of the analog front-end electronics and different test structures, has been exposed to 27 MeV protons. A second version of the chip (referred to as FSSR2), where some modifications were implemented with respect to the previous one, has been irradiated with gamma-rays from a 60Co source. This paper is devoted to presenting the results of the radiation hardness tests and assessing the suitability of the chip for operation in extremely harsh environments. more...

The envisaged upgrade of the Large Hadron Collider (LHC) at CERN towards the Super-LHC (SLHC) with a 10 times increased luminosity of 1035 cm-2 s-1 will present severe challenges for the tracking detectors of the SLHC experiments. Unprecedented high radiation levels and track densities and a reduced bunch crossing time in the order of 10 ns as well as the need for cost effective detectors have called for an intensive R&D program. The CERN RD50 collaboration ''Development of Radiation Hard Semiconductor Devices for Very High Luminosity Colliders'' is working on the development of semiconductor sensors matching the requirements of the SLHC. Sensors based on defect engineered silicon like Czochralski, epitaxial and oxygen enriched silicon have been developed. With 3D, Semi- 3D and thin detectors new detector concepts have been evaluated and a study on the use of standard and oxygen enriched p-type silicon detectors revealed a promising approach for radiation tolerant cost effective devices. These and other most recent advancements of the RD50 collaboration are presented. more...

The XAA1.2 is a custom ASIC chip for space applications built using a 0.8 μ m complementary metal oxide semiconductor technology on epitaxial layer. It has been selected as the front-end electronics chip of the SuperAGILE experiment on board the AGILE space mission, although it is not specifically designed as a radiation hard device. To study the XAA1.2 sensitivity to Single Event Effects and Total Dose Effects we irradiate this chip at the SIRAD facility of the Laboratori Nazionali INFN of Legnaro. In this paper we describe the experimental set-up and the measurements. We then discuss how the results can be scaled to the cosmic rays environment in a low-Earth orbit. more...

An option of increasing the luminosity of the Large Hadron Collider (LHC) at CERN to 10^35 cm^(- 2) s(- 1) has been envisaged to extend the physics reach of the machine. An efficient tracking down to a few centimetres from the interaction point will be required to exploit the physics potential of the upgraded LHC. As a consequence, the semiconductor detectors close to the interaction region will receive severe doses of fast hadron irradiation and the inner tracker detectors will need to survive fast hadron fluences of up to above 1016 cm 2. The CERN-RD50 project ''Development of Radiation Hard Semiconductor Devices for Very High Luminosity Colliders'' has been established in 2002 to explore detector materials and technologies that will allow to operate devices up to, or beyond, this limit. The strategies followed by RD50 to enhance the radiation tolerance include the development of new or defect engineered detector materials (SiC, GaN, Czochralski and epitaxial silicon, oxygen enriched Float Zone silicon), the improvement of present detector designs and the understanding of the microscopic defects causing the degradation of the irradiated detectors. The latest advancements within the RD50 collaboration on radiation hard semiconductor detectors will be reviewed and discussed in this work. more...

We present the first experimental data about the response of partially (PD) and fully (FD) depleted MOSFETs manufactured in a O.l mum SOI CMOS technology to heavy ion irradiation. After exposure to just a few iodine ions, several different phenomena were present. Some effects were found in all the devices we tested with good reproducibility and depended on the ion fluence; others were present from time to time, likely depending on the exact location of the ion strike and/or on the presence of pre-existing defects. Among the first category were an increase in the gate leakage current for both PD and FD devices and a reduction in the linear kink effect which is featured only by PD samples. Concerning the sporadic effects, shifts in the threshold voltage of the main and lateral parasitic transistors and reductions in maximum transconductance were found in few devices after irradiation. We related all these phenomena to the creation of defects in the gate oxide and/or charge build-up in the lateral isolation/LDD spacers. more...

We report on the design, manufacturing and first characterisation of pad diodes, test structures and microstrip detectors processed with high resistivity magnetic Czochralski (MCz) p- and n-type Si. The pre-irradiation study on newly processed microstrip detectors and test structures show a good overall quality of the processed wafers. After irradiation with 24 GeV/ c protons up to 4×10 14 cm -2 the characterisation of n-on-p and p-on-n MCz Si sensors with the C – V method show a decrease of the full depletion voltage and no space charge sign inversion. Microscopic characterisation has been performed to study the role of thermal donors in Czochralski Si. No evidence of thermal donor activation was observed in n-type MCz Si detectors if contact sintering was performed at a temperature lower than 380 °C and the final passivation oxide was omitted. more...

In the high energy physics experiments at the CERN Large Hadron Collider, the silicon detectors will suffer high radiation damage due to the large hadron (pions, protons and neutrons) fluences. It has been estimated that fluences up to 1.6 10 1-MeV equivalent neutrons/cm are expected in the 10 years of operation for the silicon strip tracker of the CMS experiment (CMS collaboration, 1998). Radiation damage causes degradation of the detector performance due to: (a) the monotonic increase of the reverse leakage current, (b) the increase of the detector depletion voltage (Vdep), after substrate space charge sign inversion due to deep acceptor generations. The ROSE Collaboration (Lindstrom et al., 2001) at CERN has widely investigated how the Vdep increase can be mitigated by introduction of impurities in the silicon substrate. Particularly, high oxygen concentrations ([O]>10 cm ) drastically reduce the Vdep increase for charged hadron (protons and pions) irradiation, whereas no such effect is observed after neutron irradiation (Lindstrom et al., 2001). In this study we present the characteristics of the bulk damage degradation induced by protons and neutrons with different energy spectra, in silicon detectors produced by various manufacturers on standard and oxygenated silicon substrates. This summary highlight the state of the art for technologies in detector radiation hardening for high energy physics applications. more...

We report on the electrical behavior of termination structures for silicon diodes irradiated with high-energy particles. In particular, the analysis is focused on samples featuring an All-P-Type (APT) termination structure, that has already been proved to yield excellent long-term stability performance. The radiation hardness of these structures is compared to that of standard devices. In order to characterise various radiation conditions, tests were performed using protons, neutrons, and high-energy electrons with different fluences up to values causing substrate type inversion. We verified that the APT samples remain functional in all the considered situations, their operational limit being comparable to that of standard devices. more...

We present a comparative study of ionizing radiation effects in 0.18 and 0.25 /spl mu/m CMOS transistors, with the goal of evaluating the impact of device scaling in the design of low-noise rad-hard analog circuits. Device parameters were monitored before and after irradiation with 10 keV X-rays and /sup 60/Co /spl gamma/-rays and after subsequent annealing. The effects of different biasing conditions during irradiation and annealing are discussed. The results are used to point out the different radiation hardness properties of the examined technologies, belonging to different CMOS generations. more...

We have developed a SPICE model for the ohmic side of AC-coupled Si microstrip detectors with interstrip isolation via field plates. The interstrip isolation has been measured in various conditions by varying the field plate voltage. Simulations have been compared with experimental data in order to determine the values of the model parameters for different voltages applied to the field plates. The model is able to predict correctly the frequency dependence of the coupling between adjacent strips. Furthermore, we have used such model for the study of the signal propagation along the detector when a current signal is injected in a strip. Only electrical coupling is considered here, without any contribution due to charge sharing derived from carrier diffusion. For this purpose, the AC pads of the strips have been connected to a read-out electronics and the current signal has been injected into a DC pad. Good agreement between measurements and simulations has been reached for the central strip and the first neighbours. Experimental tests and computer simulations have been performed for four different strip and field plate layouts, in order to investigate how the detector geometry affects the parameters of the SPICE model and the signal propagation. more...

We report selected results of laboratory measurements and beam tests of heavily irradiated microstrip silicon detectors. The detectors were single-sided devices, produced by different manufacturers and irradiated with different sources, for several total ionizing doses and fluences up to 4 /spl times/10/sup 14/ 1-MeV-equivalent neutrons per cm/sup 2/. Strip resistance and capacitance, detector leakage currents and breakdown performance were measured before and after irradiations. Signal-to-noise ratio and detector efficiency were studied in beam tests, for different values of the detector temperature and of the read-out pitch, as a function of the detector bias voltage. The goal of these test is to optimise the design of the final prototypes for the Silicon Strip Tracker of the CMS experiment at the CERN LHC collider. more...

We have developed a SPICE model of an AC-coupled single-sided polysilicon-biased silicon microstrip detector and its associated read-out electronics. The detector SPICE model is based on a RC network, whose parameters have been determined by direct comparison with DC and AC measurements. The simulated interstrip and coupling impedance and phase angle are in good agreement with experimental results, up to a frequency of 1 MHz. The readout electronics is formed by the PreShaper 32 chip, consisting of a charge preamplifier followed by a shaping amplifier, which are the basis of its SPICE implementation. The propagation of an electrical signal, simulating the charge pulse of a ionizing particle, along strips and read-out electronics has been studied experimentally and compared to the SPICE results, in order to assess the quality of the model. A satisfactory agreement on the rising edge of the output signal has been found. Different read-out configurations have been investigated as well. more...

The effects of irradiation by 16 MeV and 27 MeV protons on standard and oxygenated silicon diodes, processed by different technologies, have been investigated. The acceptor creation rate /spl beta/, after type inversion can be lower for standard diodes than for state of the art oxygenated devices, suggesting that the role of oxygen is more complex than expected and must be folded with the technology of the fabrication process. In addition we show the inaccuracy of the /spl beta/ normalization by the non-ionizing energy loss factor not only for oxygenated diodes but also for standard non-oxygenated devices. more...

P-channel MOSFETs of a commercial 0.25 /spl mu/m CMOS technology have been irradiated by high linear energy transfer (LET) iodine (I) and low LET silicon (Si) ions up to 300 Mrad(Si) and 500 Mrad(Si), respectively. Threshold voltage variations (/spl Delta/V/sub TH/) up to -0.46 V and -0.44 V have been measured at the highest I and Si doses. Both oxide positive trapped charge (/spl Delta/V/sub OX/) and interface states (/spl Delta/V/sub IT/) contribute to /spl Delta/V/sub TH/ with a ratio /spl Delta/V/sub IT///spl Delta/V/sub OX/ /spl ap/ 1 ( 1.6 V (> 3.4 V). more...

The CMS Silicon tracker consists of 70 m 2 of microstrip sensors which design will be finalized at the end of 1999 on the basis of systematic studies of device characteristics as function of the most important parameters. A fundamental constraint comes from the fact that the detector has to be operated in a very hostile radiation environment with full efficiency. We present an overview of the current results and prospects for converging on a final set of parameters for the silicon tracker sensors. more...

To obtain full charge collection the CMS silicon detectors should be able to operate at high bias voltage. We observed that multiguard structures enhance the breakdown performance of the devices on several tens of baby detectors designed for CMS. The beneficial effects of the multiguard structures still remains after the strong neutron irradiation performed to simulate the operation at the LHC. more...

The effects of irradiation by 16- and 27-MeV protons on standard and oxygenated silicon diodes, processed by different technologies, have been investigated. The acceptor creation rate /spl beta/ can be lower for standard diodes than for state-of-the art oxygenated devices, suggesting that the role of oxygen is more complex than expected and must be folded with the technology of the fabrication process. In addition, we show the inaccuracy of the /spl beta/ normalization by the nonionizing energy loss factor not only for oxygenated diodes but also for standard nonoxygenated devices. more...

Oxygenated and standard (not oxygenated) silicon diodes processed by two different manufacturers (ST Microelectronics and Micron Semiconductor) have been irradiated by low (27 MeV) and high- (24 GeV) energy protons. The leakage current density increase rate (/spl alpha/) and its annealing do not show any significant dependence on oxygenation and are the same for both manufacturers. Oxygenation improves the radiation hardness by decreasing the acceptor introduction rate (/spl beta/) and mitigating the depletion voltage (V/sub dep/) increase. Nevertheless, standard ST diodes present /spl beta/ values lower than Micron standard devices and close to oxygenated devices, whose /spl beta/s are similar for both manufacturers. The amplitude of the V/sub dep/ reverse annealing is reduced by oxygenation, which in addition delays the electrically active defect increase, at least for high-energy protons. Oxygenation is consequently the best approach for silicon substrate radiation hardening. more...

We present results obtained with full-size wedge silicon microstrip detectors bonded to APV6 (Raymond et al., Proceedings of the 3rd Workshop on Electronics for LHC Experiments, CERN/LHCC/97-60) readout chips. We used two identical modules, each consisting of two crystals bonded together. One module was irradiated with 1.7×10 14 neutrons/cm 2 . The detectors have been characterized both in the laboratory and by exposing them to a beam of minimum ionizing particles. The results obtained are a good starting point for the evaluation of the performance of the “ensemble” detector plus readout chip in a version very similar to the final production one. We detected the signal from minimum ionizing particles with a signal-to-noise ratio ranging from 9.3 for the irradiated detector up to 20.5 for the non-irradiated detector, provided the parameters of the readout chips are carefully tuned. more...

We have studied the gate leakage current after heavy ion irradiation of MOS capacitors with thin gate oxides. In 3-nm and 4-nm oxides radiation-induced soft breakdown (RSB) occurs even after ion fluences as small as 100 ion hits on the device surface. The RSB conductive paths likely reproduce the ion hit distribution: some of them can drive a substantial fraction of the whole gate leakage current. The bias applied during irradiation enhances the RSB current intensity but no critical field exists to ignite the RSB, which is observed also under flat-band. The irradiated 3-nm oxides show smaller current variations and random telegraph signal (RTS) noise than the 4-nm oxides, owing to the higher current driven in fresh devices by direct tunneling conduction. The RTS noise increases with the radiation dose; it can be described successfully neither by a Levy nor by a Gaussian distribution. In 6.5-nm and 10-mn thick oxides the defect clusters generated by heavy ion irradiation can produce RSB and RILC (radiation induced leakage current), which have not been observed after low LET irradiation or electrical stresses. more...

We have investigated the degradation of MOS structure due to high energy electron irradiation as a function of radiation dose and gate bias applied during the irradiation. Devices have been characterized by current–voltage measurements, in order to study charge accumulation also at the gate interface. Three types of oxide charge have been observed: the unstable positive charge, due to trapped holes induced by the electron irradiation; the negative charge in the oxide bulk, deriving from capture of electrons injected during electrical measurements in radiation generated traps; and border traps, at both oxide interfaces. more...

The new silicon tracker layout (V4) is presented. The system aspects of the construction are discussed together with the expected tracking performance. Because of the high radiation environment in which the detectors will operate, particular care has been devoted to the study of the characteristics of heavily irradiated detectors. This includes studies on performance (charge collection, cluster size, resolution, efficiency) as a function of the bias voltage, integrated fluence, incidence angle and temperature. more...