Radiation Damage In Silicon Research Articles

Primary radiation damage in silicon from the viewpoint of a machine learning interatomic potential

Characterization of the primary damage is the starting point in describing and predicting the irradiation-induced damage in materials. So far, primary damage has been described by traditional interatomic potentials in molecular dynamics simulations. Here, we employ a Gaussian approximation machine-learning potential (GAP) to study the primary damage in silicon with close to ab initio precision level. We report detailed analysis of cascade simulations derived from our modified Si GAP, which has already shown its reliability for simulating radiation damage in silicon. Major differences in the picture of primary damage predicted by machine-learning potential compared to classical potentials are atomic mixing, defect state at the heat spike phase, defect clustering, and recrystallization rate. Atomic mixing is higher in the GAP description by a factor of two. GAP shows considerably higher number of coordination defects at the heat spike phase and the number of displaced atoms is noticeably greater in GAP. Surviving defects are dominantly isolated defects and small clusters, rather than large clusters, in GAP's prediction. The pattern by which the cascades are evolving is also different in GAP, having more expanded form compared to the locally compact form with classical potentials. Moreover, recovery of the generated defects at the heat spike phase take places with higher efficiency in GAP. We also provide the attributes of the new defect cluster that we had introduced in our previous study. A cluster of four defects, in which a central vacancy is surrounded by three split interstitials, where the surrounding atoms are all 4-folded bonded. The cluster shows higher occurrence in simulations with the GAP potential. The formation energy of the defect is 5.57 eV and it remains stable up to 700 K, at least for 30 ps. The Arrhenius equation predicts the lifetime of the cluster to be $0.0725\phantom{\rule{0.16em}{0ex}}\ensuremath{\mu}\mathrm{s}$ at room temperature.

Study of proton radiation effect to row hammer fault in DDR4 SDRAMs

This paper shares the effects of row hammer fault through high-energy proton radiation. The significance of row hammer fault is highlighted in terms of two different technologies in DDR4 SDRAM.Row hammer stress prevents nearby storage cells from maintaining storage data within the retention time of 64-ms. The stress is worsened by the radiation damage in silicon due to the high-energy particles.Proton-based radiation damage tests were performed with DDR4 SDRAM components from two different technologies. Experiment results showed that after proton irradiation, the number of bit errors caused by the row hammering test increased about 41% and 66% in technologies 2x-nm and 2y-nm, respectively. With 2y-nm technology, bit errors started to appear from 5K Number of Hammering (NHMR)—the equivalent of 500-μs retention time. For 2y-nm components, more than 90% of failed words had multiple failed cells, which could not be corrected by Single Error Correction and Double Error Detection (SEC-DED) codes.

Radiation damage in n-type silicon diodes after electron irradiation with energies between 1.5 MeV and 15 MeV

Radiation damage in silicon, caused by the creation of point and cluster defects due to energetic charged hadrons and neutrons, results in a serious degradation of silicon-sensor performance and limits their lifetime. So far not all the defects are understood. The work presented here focuses on the study of radiation damage by electrons of different kinetic energies, from 1.5MeV to 15MeV, in order to study the differences between point- and cluster-related defects. The introduction rate of vacancy-related point defects and of so-called clustered regions was investigated as a function of electron energy. It is shown that the ratio between cluster dominated and point defect formation increases with increasing electron energy. 1.5MeV electrons create only point defects, and the formation of cluster defects starts already at 3.5MeV. To study the defect kinetics, isothermal annealing at 80°C and isochronal annealing measurements were performed.

A systematic study on analysis-induced radiation damage in silicon during channeling Rutherford backscattering spectrometry analysis

Channeling Rutherford backscattering spectrometry (RBS) is an essential analysis technique in materials science. However, the accuracy of RBS can be significantly affected by disorders in materials induced by the analyzing ion beam even under channeling mode. We have studied RBS analysis-induced radiation damage in silicon. A 140-keV H+ ion beam was incident along 〈100〉 Si axis at room temperature to a fluence ranging from 1.6×1016cm−2 to 7.0×1016cm−2. The evolution of the aligned yields versus fluences has been examined and found to agree well with a model proposed by us.

Radiation damage in silicon exposed to high-energy protons

Photoluminescence, infrared absorption, positron annihilation, and deep-level transient spectroscopy (DLTS) have been used to investigate the radiation damage produced by $24\phantom{\rule{0.3em}{0ex}}\mathrm{GeV}∕c$ protons in crystalline silicon. The irradiation doses and the concentrations of carbon and oxygen in the samples have been chosen to monitor the mobility of the damage products. Single vacancies (and self-interstitials) are introduced at the rate of $\ensuremath{\sim}1\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$, and divacancies at $0.5\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$. Stable di-interstitials are formed when two self-interstitials are displaced in one damage event, and they are mobile at room temperature. In the initial stages of annealing the evolution of the point defects can be understood mainly in terms of trapping at the impurities. However, the positron signal shows that about two orders of magnitude more vacancies are produced by the protons than are detected in the point defects. Damage clusters exist, and are largely removed by annealing at $700\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}800\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, when there is an associated loss of broad band emission between 850 and $1000\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$. The well-known $W$ center is generated by restructuring within clusters, with a range of activation energies of about $1.3\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}1.6\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$, reflecting the disordered nature of the clusters. Comparison of the formation of the $X$ centers in oxygenated and oxygen-lean samples suggests that the $J$ defect may be interstitial related rather than vacancy related. To a large extent, the damage and annealing behavior may be factorized into point defects (monitored by sharp-line optical spectra and DLTS) and cluster defects (monitored by positron annihilation and broadband luminescence). Taking this view to the limit, the generation rates for the point defects are as predicted by simply taking the damage generated by the Coulomb interaction of the protons and Si nuclei.

Radiation damage studies for the DØ silicon detector

We report on irradiation studies performed on spare production silicon detector modules for the current D Ø silicon detector. The lifetime expectations due to radiation damage effects of the existing silicon detector are reviewed. A new upgrade project was started with the goal of a complete replacement of the existing silicon detector. In that context, several investigations on the radiation hardness of new prototype silicon microstrip detectors were carried out. The irradiation on different detector types was performed with 10 MeV protons up to fluences of 10 14 p/ cm 2 at the J.R. Mcdonald Laboratory at Kansas State University. The flux calibration was carefully checked using different normalisation techniques. As a result, we observe roughly 40–50% less radiation damage in silicon for 10 MeV p exposure than it is expected by the predicted NIEL scaling.

Radiation damage in silicon studied in situ by nanocalorimetry

In situ observations of thermal processes involving nJ energies are impractical, if not impossible, with conventional differential scanning calorimetry (DSC), but the nanometric scale of recently developed nanocalorimetry systems should make such observations possible. Nanocalorimetry is based on membrane calorimeters made using nanofabrication technologies. Here we present initial results of an in situ investigation of damage dynamics in amorphous silicon (a-Si). A thin film of a-Si was deposited on the calorimeter membrane and implanted with low-energy Si ions. One-time heat releases were measured for doses ranging from 1012 to 1014ioncm−2. Subsequent calorimetry scans showed no difference with the baselines, indicating that the damage remaining is stable over the temperature of operation. The measurements were taken immediately after ion implantation in the same environment and were repeated. For doses of 1012ioncm−2 and less, the signal intensity was below the sensitivity limit. A saturation of the total heat released was observed. This saturation was correlated with previous DSC measurements and attributed to the relaxation of ion beam implanted a-Si.

The space charge relaxation behaviour of silicon diodes irradiated with 1 MeV neutrons

The current–voltage characteristic of silicon diodes irradiated with 1 MeV neutrons demonstrates an ohmic behaviour and a resistance grouped around the theoretical maximum value. These two effects suggest that radiation damage in silicon induces relaxation behaviour which results in pinning of the Fermi level at mid-gap. Several crude measures of the relaxation-like behaviour have been devised and are presented. The measures have been determined for three sets of silicon diodes (pure, high resistivity gold-doped and low resistivity gold-doped) and are discussed in relation to the activation energy and also to the two measures of radiation damage. Using these different measures it is possible to identify relaxation-like devices and also to determine the level of damage within an irradiated sample.

Non-linear effect on radiation damage of silicon by cluster ion bombardment

Due to the spatial and temporal close proximity of cluster ion bombardment on Silicon, radiation damage of Si due to cluster ions cannot be extrapolated from that of atomic ions. In this paper we overview our recent observations of radiation damage in Si by clusters of C and Au aggregates of up to 10 atoms and 4 atoms respectively. Quantification of damage is made by RBS/channeling. We observed hyper linear radiation damage depending on cluster size. We developed a theoretical interpretation of this observation using a collision cascade overlapping model.

Comparison of radiation damage in silicon induced by proton and neutron irradiation

The subject of radiation damage to Si detectors induced by 24-GeV/c protons and nuclear reactor neutrons has been studied. Detectors fabricated on single-crystal silicon enriched with various impurities have been tested. Significant differences in electrically active defects have been found between the various types of material. The results of the study suggest for the first time that the widely used nonionizing energy loss (NIEL) factors are insufficient for normalization of the electrically active damage in case of oxygen- and carbon-enriched silicon detectors. It has been found that a deliberate introduction of impurities into the semiconductor can affect the radiation hardness of silicon detectors.

Measurement and Modelling of the Radiation Damage of Silicon by MeV Ag Ions

AbstractDepth profiles of the radiation damage produced by 4 MeV Ag ions in Si(111) at temperatures of 210-450 K are studied by optical reflectivity depth profiling and TEM for doses between 1012 and 1015 Ag/cm2. For high implantation temperatures, the depth of maximum damage is shown to be dose dependent. Point defect diffusion is shown to result in long tails of defect depth profiles. High-temperature amorphization is observed to proceed via the formation and bridge-like coalescence of isolated amorphous volumina. The damage at the depth of the maximum in the nuclear stopping power is described as a function of dose and temperature by the Hecking model. The model parameters and a comparison with those obtained for lighter ions reflect the particular properties of heavy ion collision cascades.

Radiation Damage of Silicon and Diamond by High Energy Neutrons, Protons and α Particles

Radiation Damage of Silicon and Diamond by High Energy Neutrons, Protons and α Particles

Effects of radiation damage in silicon p - i - n photodiodes

The effects of radiation damage in two silicon p - i - n photodiodes fabricated from high resistivity material have been studied. The devices have been irradiated by 1 MeV neutrons to three different fluences up to . Current, capacitance and charge measurements were performed prior to irradiation and soon after. Our results indicate that the damage has degraded the charge-collection efficiency, that the devices have undergone type inversion from n-type to apparent p-type at fluences as low as , and that the substrate material has become somewhat `relaxation-like' after irradiation. It is suggested here that irradiated silicon is relaxation material.

Investigation of Radiation Damage in Silicon Produced by Fast Neutron Irradiation with Lifetime Measurements and Deep Level Transient Spectroscopy

Investigation of Radiation Damage in Silicon Produced by Fast Neutron Irradiation with Lifetime Measurements and Deep Level Transient Spectroscopy

Investigation of Radiation Damage in Silicon Produced by Fast Neutron Irradiation with Lifetime Measurements and Deep Level Transient Spectroscopy

Deep level transient spectroscopy (DLTS) and lifetime measurements were carried out on silicon p + nn + diodes before and after irradiation with fast neutrons at room temperature with fluences of 5.5 x 10 11 and 1.0 x 10 12 n/cm 2 . In the non-irradiated samples the observed levels satisfactorily explained the measured data of recombination and generation lifetimes in the frame of the Shock-ley-Hall-Read (SHR) theory. After irradiation the lifetime data showed discrepancies with the parameters of the existing levels, which was explained by the cluster structure of the neutron damage defects.

Minimizing radiation damage in silicon structured with low energy focused ion beams

Monocrystalline silicon has been irradiated with ion beams of different energies (60 keV down to 100 eV) with fluences from 10 10/cm 2 to 10 16/cm 2. Ga, Si, Pr and Au ion beams have been used with a spot size between 0.1 and 1 μm. Reflectivity at normal incidence at a wavelength of 785 nm and laser induced, modulated reflectivity have been applied for the characterisation of the optical and surface properties of the samples after irradiation. Sputtering and deposition have been studied by Atomic Force Microscopy (AFM). For keV energies an abrupt increase in reflectivity and modulated reflectivity has been found with the onset of the amorphisation process at fluences around 10 14 to 10 15 atoms/cm 2. Irradiation with silicon ions shows a smaller increase in reflectivity, since there is no enhanced optical absorption due to implantation of metallic ions. Irradiation at energies below 1 keV results in a three orders of magnitude lower defect production in comparison to higher energies. While AFM measurements of silicon irradiated with Au to fluences of 5 × 10 17/cm 2 still showed removal of material down to an energy of 500 eV, irradiation with Si ions produced no significant removal at any investigated energy. A minimum of crystal damage per removed substrate atom has been found for sputtering with Au and Ga at energies around 1 keV.

Luminescence centres containing two, three and four hydrogen atoms in radiation-damaged silicon

Photoluminescence measurements are reported which show that the centres responsible for the X-lines, which are created by radiation damage in silicon deliberately doped with hydrogen followed by annealing at 450°C, contain two, three or four hydrogen atoms at equivalent or inequivalent sites. The large hydrogen-deuterium isotope shifts observed are shown to be caused primarily by linear electron-phonon coupling and the anharmonicity of local vibrational modes. There is negligible interaction between different hydrogen atoms within each centre and the isotope shifts associated with different sites in a centre can have opposite signs.

EPR, XRD and optical reflectivity studies of radiation damage in silicon after high energy implantation of Ni ions

(111) silicon has been implanted with 6 MeV 68 Ni ions at various temperatures in a dose range from 5 × 10 12 to 2 × 10 17 Ni cm 2 . Quantitative depth resolved optical studies on the radiation damage are compared with EPR and XRD measurements, giving direct information on existing defect species and changes of the lattice period, respectively. Results of EPR investigations support the interpretation of the dose and temperature dependence of the optically detected damage given by Lindner and te Kaat [J. Mater. Res. 3 (1988) 1238], who base themselves on the damage model of Hecking et al. [Nucl. Instr. and Meth. B 15 (1986) 760]. EPR lines of five different point defect (Si-A4, Si-P1, Si-A6, Si-B2, Si-P3) and of amorphous material are observed. The use of different experimental methods allows for a comparison of the individual sensitivities for several kinds of damage.

Silicon Detectors Highly Compensated by Neutron Induced Deep Levels for Low Energy X-RAY Detection

ABSTRACTFast neutron radiation damage in silicon results in defect levels which are predominantly acceptor-like at low fluences and may be used to compensate high resistivity ntype material to create very high effective resisitivity material. Compensated material to the order of Neff below 1011/cm3 enables depletion of diode thicknesses ≥ 1mm at reasonable biases (<100V), yielding diodes of reasonable area and capacitance<1 pF which are suitable for low noise applications such as X-ray spectrometry. Although exposure to fluences of this order will greatly increase the generation current and require cooling, most high resolution X-ray spectrometry systems are routinely operated at reduced temperature to achieve low noise operation of the front end electronics. Silicon p+ /n− /n+ implanted devices (area ≤0.25 cm2) made on high resistivity FZ silicon have been irradiated by 1 MeV neutrons to fluences of a few times 1012 n/cm2. Thick n− substrates (d=630 μm and 1000 μm) were used to achieve detector capacitances εεo/d in the range of 1 pF. After a neutron fluence of ϕn=2.9×1012 n/cm2, the total depletion of a p+/n−/n+ detector, 1040 μm thick and an area of 0.1 cm2, is reached at about V=50 Volts, with a Cd of 1 pF and a neutron induced leakage current of about 300 nA at room temperature. A total depletion of an 680 μm thick detector was reached after the fluence of 2-5×1012 n/cm2 at a voltage of 20 volts, and the capacitance of a 0.25 cm2 diode is 4.5 pF The resistivities of the compensated detector substrates are in the range of 100 K Ω-cm, and are not inverted to “p” type. The trapping of collected charge by neutron induced deep levels is modeled and simulated, and is found to be less than a few percent; with no obvious effect on peak shape. Using a resistive feedback preamplifier of modest noise contribution (225 eV), resolution of the Mn K∝ X-ray was 255 eV (FWHM) with 3 μsec shaping time constants. Other effects of uncollected charge will be discussed and comparisons between this type of detectors and Li-drift silicon detectors will be made.

Slight Radiation Damage in Silicon for Si-Based Device Processing

ABSTRACTUtilization of radiation damage by means of ion implantation to reduce parasitic capacitances in GaAs integrated circuits has become a well-established technique in the last years. Similar to GaAs, novel high-speed silicon-based devices, e.g. the Si/SiGe heterojunction bipolar transistor, are generally marked by additional short time annealing related to doping activation and a metallization annealing step in the range of 400 °C .For reproducing the external base region of such devices, Si-p+nn+ diodes were realized and investigated using I-V and C-V measurements. Slight radiation damage was achieved by Ne-implantation. Apart from enhanced leakage currents due to space charge recombination, capacitance reduction for frequencies above 50 kHz was observed even for a n-layer doping concentration as high as 1 to 2x1017 cm-3 including a 12 min 400 °C annealing step. Preliminary tests with 250 keV-Ne-ions within a dose range between 1013 and 1014 cm-2 were carried out with Schottky diodes on moderately doped n-type Si-substrate (0.3 Ωcm). For a high temperature furnace anneal at 900 °C (2 min), no capacitance reduction could be observed.Compared to previous results with Ar-implantation to obtain amorphized silicon layers, this technique allows a more easy technological handling concerning the metallization and the use of a simple photoresist pattern.