High Energy Hadrons Fluence Measurements in the LHC during 2015, 2016 and 2017 Proton Physics Operations.

In order to reduce the risk of failure for the electronic equipment installed in the underground areas of LHC, every year the Radiation Monitors (RadMons) are used to measure the High Energy Hadrons (HEH) fluence in the tunnel and in the shielded areas. In the framework of the Radiation to Electronics Project (R2E), this work discusses the measurements for the proton physics operations in 2015, 2016 and 2017

Single-Event Radiation Effects in Silicon Carbide Power MOSFETs

In this research, the radiation induced single event effects (SEE) observed in silicon carbide (SiC) power MOSFETs have been studied. Heavy ions, terrestrial neutrons and protons were selected as radiation environments to be investigated, as representative of space, avionics and high-energy accelerator applications. SEE tests and electrical analysis were performed in order to identify the modes and mechanisms of failure, and to assess the reliability of commercial SiC MOSFET technologies. The research initially focused on the non-catastrophic SEEs induced by heavy-ion irradiation, which represent a significant risk for the part reliability in space applications. The broad-beam and microbeam results pave the way to the understanding of the degradation mechanism, named single event leakage current (SELC). Two types of degradation are described in this work, involving different parts of the SiC MOSFET structure depending on the applied voltage during the operation. At low bias the SELC is observed in the region under the gate oxide, whereas for voltages over a certain threshold a second mechanism involving the p-n junction is newly added. Heavy-ion latent damage effects were also studied through radiation tests and scanning electron microscopy (SEM) analysis of the damaged site. Two mechanisms were observed, involving the gate oxide and the SiC crystal lattice. Finally, the heavy-ion SEEs are summarised as function of the operational bias and linear energy transfer (LET). The second part of this work focused on SiC MOSFET reliability when exposed to proton and terrestrial-neutron environments. Accelerated single event burnout tests were performed using devices with different architectures. Electrical analysis of the damaged devices was carried out to investigate the failure mechanism. The results provide useful information about the reliability of the commercial SiC MOSFET technologies for avionic and high-energy accelerator applications. This project was carried out in the framework of a collaboration between the Physics Department at the University of Jyväskylä, the radiation to electronics (R2E) project at the European Council for Nuclear Research (CERN), and the Advanced Power Semiconductor (APS) Laboratory at ETH Zürich. Keywords: silicon carbide, power MOSFETs, radiation effects, Single Event Effects, SELC, SEB, SEGR, latent damageTässä työssä on tutkittu yksittäisten hiukkasten aiheuttamia säteilyilmiöitä piikarbidista (SiC) valmistetuissa MOSFET-tehotransistoreissa. Tutkimukseen valitut säteilytyypit sisälsivät raskaita hiukkasia, neutroneja sekä protoneja. Näitä hiukkasia tavataan tyypillisesti avaruus-, ilmailu- sekä kiihdytinsovelluksien toimintaympäristöissä. Säteilytestaukset ja sähköiset karakterisoinnit suoritettiin, jotta vauriomekanismien eri moodit saatiin selville, sekä kaupallisten SiC MOSFET-teknologioiden luotettavuus arvioitua. Ensisijaisesti tutkimus keskittyi raskaiden hiukkasten ei-katastrofaalisiin säteilyilmiöihin, jotka luovat merkittävän riskin komponenttien luotettavuudelle ja sen arvioimiselle avaruussovelluksissa. Fokusoituja (ns. mikrosuihkuja) sekä laaja-alaisia suihkuja käyttämällä on mahdollista paremmin ymmärtää SELC-vauriomekanismia (engl. Single Event Leakage Current). Tässä työssä kuvataan kahdenlaista SELC-vauriotyyppiä, mitkä kohdistuvat fyysisesti transistorin eri osiin riippuen käytetystä biasjännitteestä. Matalammilla jännitteillä SELC havaitaan hilaoksidin alueella, kun taas korkeammilla jännitteillä vaurio havaitaan transistorin runkodiodin alueella. Työssä tutkittiin myös raskaiden hiukkasten aiheuttamia piileviä (latentteja) vaurioita kuvantamalla vauriokohtia elektronimikroskoopin avulla. Latentteja vauriotyyppejäkin havaitaan kahdenlaisia, joihin liittyvät alueet komponentin sisällä ovat hilaoksidi sekä SiC substraatti. Yllä mainituista tuloksista on mahdollista määrittää raskaiden hiukkasten SEE-ilmiöiden eri alueet käyttöjännitteen sekä hiukkasen energiajätön funktiona. Työn toisessa osassa keskityttiin SiC MOSFETien luotettavuuteen protoni- ja neutronisäteily-ympäristöissa. Kiihdytettyjä SEB-testejä (engl. Single Event Burnout) käyttäen eri komponenttiarkkitehtuureja tutkittiin. Saadut tulokset antavat hyödyllistä tietoa kaupallisten SiC MOSFET teknologioiden luotettavuudesta ilmailu- sekä kiihdytinsovelluksissa. Tämä projekti tehtiin yhteistyössä Jyväskylän yliopiston fysiikan laitoksen, CERN:n R2E-projektin (Radiation to Electronics), sekä ETH Zürichin APS (Advanced Power Semiconductor) laboratorion kanssa. Avainsanat: piikarbidi, teho-MOSFET, säteilynvaikutukset, SEE, SELC, SEB, SEGR, latentit vaurio

Heavy-Ion-Induced Defects in Degraded SiC Power MOSFETs

Cathodoluminescence spectroscopy is used to investigate the formation of point- and extended defects in SiC power MOSFETs exposed to heavy-ions. Devices showing single event leakage current (SELC) effects are analysed and compared to pristine samples. Common luminescence peaks of defect centers localized in the thermal-SiO2 are identified, together with peaks at the characteristic wavelength of extended defects.peerReviewe

TID, ΦHEH and ΦThN measurements along the SPS accelerator and the adjacent Tunnel Access Areas

In this document, the measurements of Total Ionizing Dose, High Energy Hadron fluence and Thermal Neutron fluence are presented for some areas of the Super Proton Synchrotron, cumulated during 2017 and 2018. The investigation aims at characterizing the radiation field that might affect some sensitive equipment installed by the Beam Instrumentation group (BE/BI). The areas investigated are the arcs and tunnel access areas TA1, TA2 and TA6

Investigation of Electrically Active Defects in SiC Power Diodes Caused by Heavy Ion Irradiation

Deep-level transient spectroscopy (DLTS) and minority carrier transient spectroscopy (MCTS) are used to investigate electrically active defects in commercial silicon carbide (SiC) Schottky power diodes after heavy-ion microbeam irradiation at different voltages. The DLTS and MCTS spectra of pristine samples are analyzed and compared to devices showing or not signatures of single event leakage current (SELC) degradation. An additional peak labeled 'C' with an activation energy of 0.17 eV below the conduction band edge is observed in the DLTS spectra of a sample degraded with SELC.ISSN:0018-9499ISSN:1558-157

High-Energy Proton and Atmospheric-Neutron Irradiations of SiC Power MOSFETs: SEB Study and Impact on Channel and Drift Resistances

Accelerated single event burnout (SEB) tests with 200 MeV protons and atmospheric neutrons were performed for commercial silicon carbide (SiC) power MOSFETs with different architectures (i.e., planar gate, asymmetric trench, and symmetric trench). The average electric fields over the depletion layer width and the electric field distributions are reported for the tested conditions and compared for the three architectures, confirming the necessity of a lower de-rating for the trench design to protect from SEB, compared to planar ones. In addition to the epitaxial layer design, the influence of other design parameters on the SEB threshold is discussed. Finally, to investigate the presence of precursor damage in the pre-SEB region, a methodology is presented and used to study the radiation-induced degradation of the channel and drift resistances of devices that survived the SEB tests.ISSN:0018-9499ISSN:1558-157

Radiation Levels at the LHC: 2012, 2015 and 2016 Proton Physics Operations in View of HL-LHC requirements

The variety of beam losses produced in the Large Hadron Collider (LHC) creates a mixed and complex radiation field. During 2012, 2015 and 2016, Beam Loss Monitors and RadMons were used to monitor the inte-grated dose and the High Energy Hadrons fluence in order to anticipate the electronics degradation and inves-tigate the cause of failures. The annual radiation levels are compared; highlighting the mechanisms in the pro-duction of beam losses and the impact of the different squeeze and crossing angle. In addition, the increase of beam-gas interaction is discussed comparing operations at 25 ns and 50 ns bunch spacing. A strategy is presented to allow for a continuous respective evaluation during the upcoming LHC and future High Luminosity LHC (HL-LHC) operations

Current Transport Mechanism for Heavy-Ion Degraded SiC MOSFETs

High sensitivity of SiC power MOSFETs has been observed under heavy ion irradiation, leading to permanent increase of drain and gate leakage currents. Electrical postirradiation analysis confirmed the degradation of the gate oxide and the blocking capability of the devices. At low drain bias, the leakage path forms between drain and gate, while at higher bias the heavy ion induced leakage path is mostly from drain to source. An electrical model is proposed to explain the current transport mechanism for heavy-ion degraded SiC power MOSFETs.peerReviewe

Current Transport Mechanism for Heavy-Ion Degraded SiC MOSFETs

ISSN:0018-9499ISSN:1558-157

Isotopic Enriched and Natural SiC Junction Barrier Schottky Diodes under Heavy Ion Irradiation.

The radiation tolerance of isotopic enriched and natural silicon carbide junction barrier Schottky diodes are compared under heavy ion irradiation. Both types of devices experience leakage current degradation as well as single event burnout events. The results were comparable, although the data may indicate a marginally lower thresholds for the isotopic enriched devices at lower LET. Slightly higher reverse bias threshold values for leakage current degradation was also observed compared to previously published work.peerReviewe