Induced Charge Collection Research Articles

Laser Beam Induced Charge Collection for Defect Mapping and Spin State Readout in Diamond

Laser Beam Induced Charge Collection for Defect Mapping and Spin State Readout in Diamond

Study of MIPs effects on a MAPS for electron ion collider in China

The Monolithic Active Pixel Sensor (MAPS) is a good candidate for the inner tracking system of the Electron–Ion Collider in China (EicC). Hence, a MAPS with a pixel pitch of ∼30 µm is being designed. Two 130 nm CMOS processes have been proposed as candidates for this MAPS design. The first one is a commercial standard twin-well low-resistivity (<50 Ω cm−3) process, and the other one is a quadruple-well high-resistivity (>1 kΩ cm−3) process. A 3-dimensional TCAD model of the pixels has been established to evaluate the Minimum Ionizing Particles (MIPs) induced charge collection in these two processes. This paper will discuss the study of charge collection efficiency, charge collection time, and charge sharing among pixels.

Lithium source for focused ion beam implantation and analysis

We present a new Li source for focused ion beam applications. Based on an AuSi eutectic alloy, Li is added as an impurity to minimize effects from degradation when exposed to air. We show the source is stable over the course of an hour and spot sizes ≲10 nm can be achieved. The Li beam can achieve hundreds of nanometer ranges in semiconductors with minimal damage being generated along the path length. The source performance is evaluated through a high-resolution ion beam induced charge collection experiment on an Si-based detector. Further application of the source for ion beam analysis is numerically explored; the example investigated is based on probing a semiconductor heterostructure through a Rutherford backscattering experiment, where the Li beam can reveal information that is inaccessible with either low energy or high energy He projectiles used as probes.

SOI Thin Microdosimeter Detectors for Low-Energy Ions and Radiation Damage Studies

The responses of two silicon on insulator (SOI) 3-D microdosimeters developed by the Centre for Medical Radiation Physics were investigated with a range of different low energy ions, with high linear energy transfer (LET). The two microdosimeters n-SOI and p-SOI were able to measure the LET of different ions including 7Li, 12C, 16O, and 48Ti with ranges below $350~\mu \text{m}$ in silicon. No plasma effects were seen in the SOI microdosimeters when irradiated with the high LET ions. A Monte Carlo simulation using Geant4 was compared to the experimental measurements, whereby some discrepancies were observed for heavier ions at lower energies. This discrepancy can be partly attributed to uncertainties in the thickness of the energy degraders and overlayers of the devices. The microdosimetric measurements of low energy 16O ions were obtained and compared to a therapeutic 16O ion beam. The radiation hardness of the two devices was studied using the ion beam induced charge collection technique. Both types of the microdosimeters when biased had no essential changes in charge collection efficiency in the sensitive volume after irradiation with low energy ions.

A 3D lateral electrode structure for diamond based microdosimetry

A diamond based microdosimeter prototype featuring a 3D lateral electrode structure was created using laser ablation and active brazing alloys and characterised by means of ion beam induced charge collection measurements and finite element analysis, using Synopsys TCAD simulation package.

Fabrication and characterization of a co-planar detector in diamond for low energy single ion implantation

We demonstrate low energy single ion detection using a co-planar detector fabricated on a diamond substrate and characterized by ion beam induced charge collection. Histograms are taken with low fluence ion pulses illustrating quantized ion detection down to a single ion with a signal-to-noise ratio of approximately 10. We anticipate that this detection technique can serve as a basis to optimize the yield of single color centers in diamond. The ability to count ions into a diamond substrate is expected to reduce the uncertainty in the yield of color center formation by removing Poisson statistics from the implantation process.

Characterisation of Silicon Diode Arrays for Dosimetry in External Beam Radiation Therapy

Modern stereotactic radiation therapy modalities utilize small beams and large dose gradients to deliver radiation in few fractions, reducing the possibility to correct for mistakes during the treatment process. Therefore, in order to ensure best possible treatment for the patient, quality assurance for such treatments necessitates a stable, linear, and sensitive radiation detector with high spatial resolution and radiation hardness. In this work, two silicon detector arrays with high spatial resolution have been characterized by 6 MV and 18 MV medical LINAC irradiation, and 5.5 MeV He2+ heavy ion microprobe. A maximum discrepancy of 0.6 mm in field size has been found when comparing to two-dimensional radiochromic film dose profile, and charge collection efficiency obtained by means of ion beam induced charge collection (IBICC) is 66% when operating the array in photovoltaic mode. Radiation damage study by photons and photoneutrons is presented.

Characterization of a Large Area Thinned Silicon Microdosimeter for Space and Particle Therapy

The tissue-equivalent proportional counter is the gold standard detector in microdosimetry. The energy deposited in its volume is equal to that of a single cell through the use of low pressure tissue-equivalent gas. To overcome its bulky gas-flow ensemble, high operating voltage and poor spatial resolution, a 20 μm-thick silicon microdosimeter with 9600 micron-sized sensitive volumes has been developed. Presented are the results from its initial characterization including electrical properties and charge collection characteristics obtained using induced charge collection techniques at ANSTO, Australia, and the ESRF, France. In addition, the results from a 290 MeV/u C-12 irradiation at HIMAC, NIRS, Japan, are presented.

Effect of body biasing on single-event induced charge collection in deep N-well technology

As the device size decreases, the soft error induced by space ions is becoming a great concern for the reliability of integrated circuits (ICs). At present, the body biasing technique is widely used in highly scaled technologies. In the paper, using the three-dimensional technology computer-aided design (TCAD) simulation, we analyze the effect of the body biasing on the single-event charge collection in deep N-well technology. Our simulation results show that the body biasing mainly affects the behavior of the source, and the effect of body biasing on the charge collection for the nMOSFET and pMOSFET is quite different. For the nMOSFET, the RBB will increase the charge collection, while the FBB will reduce the charge collection. For the pMOSFET, the effect of RBB on the SET pulse width is small, while the FBB has an adverse effect. Moreover, the differenceof the effect of body biasing on the charge collection is compared in deep N-well and twin well.

Characterization of an Alternative Diamond Based Microdosimeter Prototype

A diamond microdosimeter prototype with sensitive volumes separated through laser milled trenches is characterized. It is proposed that this design will offer a new and alternative means of creating a diamond based microdosimeter. The device has been characterized by means of ion beam induced charge collection (IBIC) measurements. In this work, it is shown that laser milled trenches have a significant effect upon the lateral confinement of charge collection essentially creating a pixelated diamond detector. Specifics of the results and an update on the current status of the project are presented.

3-D simulation of angled strike heavy-ion induced charge collection in silicon–germanium heterojunction bipolar transistors

This paper presents 3-D simulation of angled strike heavy-ion induced charge collection in domestic silicon–germanium heterojunction bipolar transistors (SiGe HBTs). 3D damaged model of SiGe HBTs single-event effects (SEE) is built by TCAD simulation tools to research ions angled strike dependence. We select several different strike angles at variously typical ions strike positions. The charge collection mechanism for each terminal is identified based on analysis of the device structure and simulation results. Charge collection induced by angled strike ions presents a complex situation. Whether the location of device ions enters, as long as ions track through the sensitive volume, it will cause vast charge collection. The amount of charge collection of SiGe HBT is not only related to length of ions track in sensitive volume, but also influenced by STI and distance between ions track and electrodes. The simulation model is useful to research the practical applications of SiGe HBTs in space, and provides a theoretical basis for the further radiation hardening.

Charge Collection in n-SOI Planar Microdosimeters

An n-SOI microdosimeter which has been proposed as a device for predicting the occurrence of single event effects in semiconductor electronics in the high-energy, mixed heavy ion space radiation environment has been investigated to better understand the charge collection geometry and charge collection mechanisms. Ion beam induced charge collection studies using 20 MeV 12C ions, 5.5 MeV 4He ions, and 2 MeV H ions were carried out, and the effects of different bias conditions, angles of ion incidence, and coincidence analysis were observed to understand the sensitive volume geometry. The energy response of the n-SOI microdosimeter has been observed to exhibit an over-response of 56%, 113%, and 23% for the above ions compared to expected energy depositions calculated using SRIM 2008. No relationship between particle LET AU: Please provide spelling for “LET” and the enhance energy response was apparent. A comparison of experimentally measured and simulated spectra suggest a cylindrical charge collection geometry despite the physical rectangular parallelepiped geometry of the p-i-n diode. This was supported by observing the response of the microdosimeter to ions at oblique ion incidence. A simplified model of diffusion charge collection found that diffusion charge collection contributes to the low-energy tail observed in experimental spectra, but does not account for the observed enhanced energy response. This supports the current theory that the enhanced energy response is a result of a displacement current produced when charge carriers in the substrate induce charge in the SOI layer due to the parasitic capacitance of the buried SiO2 insulating layer.

3D simulation of heavy ion induced charge collection of single event effects in SiGe heterojunction bipolar transistor

In this paper, we establish a three-dimensional numerical simulation model for SiGe heterojunction bipolar transistor by the technology computer aided design simulations. In the simulation we investigate the charge collection mechanism by heavy ion radiation in SiGe HBT technology. The results show that the charge collected by the terminals is a strong function of the ion striking position. The sensitive area of charge collection for each terminal is identified based on the analyses of the device structure and simulation results. For a normal strike within and around the area of the collector/substrate junction, most of the electrons and holes are collected by the collector and substrate terminals, respectively. For an ion strike between the shallow trench edges surrounding the emitter, the base collects a large quantity of charge, while the emitter collects a negligible quantity of charge.

A time-resolved IBICC experiment using the IEEM of the SIRAD facility

The Ion Electron Emission Microscope (IEEM) of the SIRAD irradiation facility at LNL (Legnaro, Italy) has been used to perform an Ion Beam Induced Charge Collection (IBICC) type experiment irradiating a power MOSFET device with 223 MeV 79Br ions. The ion-induced drain current pulse signals at different bias conditions were correlated with the ion impacts reconstructed by the IEEM to disentangle, with micrometric resolution, regions of the device with different sensitivity to the impinging ions.

Direct Comparison of Charge Collection in SOI Devices From Single-Photon and Two-Photon Laser Testing Techniques

The amounts of charge collection by single-photon absorption (SPA) and by two-photon absorption (TPA) laser testing techniques have been directly compared using specially made SOI diodes. For SPA measurements and some TPA measurements, the back substrates of the diodes were removed by etching with XeF2. With the back substrates removed, the amount of TPA induced charge collection can be correlated to the amount of SPA induced charge collection. There are significant differences, however, in the amount of TPA induced charge collection for diodes with and without substrates. For the SOI diodes of this study, this difference appears to arise from several contributions, including nonlinear-optical losses and distortions that occur as the pulse propagates through the substrate, as well as displacement currents that occur only when the back substrate is present. These results illustrate the complexity of interpreting TPA and SPA single-event upset measurements.

Study of variations of the carrier recombination and charge transport parameters during proton irradiation of silicon pin diode structures

Techniques for the remote and in situ control of carrier recombination and drift parameters during proton irradiation are presented. The measurement and evaluation of the carrier recombination and drift-diffusion characteristics are based on simultaneous analysis of microwave probed photoconductivity transients and of the induced charge collection current transients in diodes with applied electric field during the proton exposure.

Design of Digital Circuits Using Inverse-Mode Cascode SiGe HBTs for Single Event Upset Mitigation

We report on the design and measured results of a new SiGe HBT radiation hardening by design technique called the “inverse-mode cascode” (IMC). A third-generation SiGe HBT IMC device was tested in a time resolved ion beam induced charge collection (TRIBICC) system, and was found to have over a 75% reduction in peak current transients with the use of an n-Tiedown on the IMC sub-collector node. Digital shift registers in a 1st-generation SiGe HBT technology were designed and measured under a heavy-ion beam, and shown to increase the LET threshold over standard npn only shift registers. Using the CREME96 tool, the expected orbital bit-errors/day were simulated to be approximately 70% lower with the IMC shift register. These measured results help demonstrate the efficacy of using the IMC device as a low-cost means for improving the SEE radiation hardness of SiGe HBT technology without increasing area or power.

A Comprehensive Understanding of the Efficacy of N-Ring SEE Hardening Methodologies in SiGe HBTs

We investigate the efficacy of mitigating radiation-based single event effects (SEE) within circuits incorporating SiGe heterojunction bipolar transistors (HBTs) built with an N-Ring, a transistor-level layout-based radiation hardened by design (RHBD) technique. Previous work of single-device ion-beam induced charge collection (IBICC) studies has demonstrated significant reductions in peak collector charge collection and sensitive area for charge collection; however, few circuit studies using this technique have been performed. Transient studies performed with Sandia National Laboratory's (SNL) 36 MeV 16O microbeam on voltage references built with N-Ring SiGe HBTs have shown mixed results, with reductions in the number of large voltage disruptions in addition to new sensitive areas of low-level output voltage disturbances. Similar discrepancies between device-level IBICC results and circuit measurements are found for the case of digital shift registers implemented with N-Ring SiGe HBTs irradiated in a broadbeam environment at Texas A&M's Cyclotron Institute. The error cross-section curve of the N-Ring based register is found to be larger at larger ion LETs than the standard SiGe register, which is clearly counter-intuitive. We have worked to resolve the discrepancy between the measured circuit results and the device-level IBICC measurements, by re-measuring single-device N-Ring SiGe HBTs using a time-resolved ion beam induced charge (TRIBIC) set-up that allows direct capture of nodal transients. Coupling these measurements with full 3-D TCAD simulations provides complete insight into the origin of transient currents in an N-Ring SiGe HBT. The detailed structure of these transients and their bias dependencies are discussed, together with the ramifications for the design of space-borne analog and digital circuits using SiGe HBTs.

The theory of ion beam induced charge in metal-oxide-semiconductor structures

Silicon-on-insulator circuits have been considered less sensitive to single event effects than devices made using bulk technology. However, model experiments have indicated that charge collection occurs not only from the active layer above the buried oxide (BOX) but also from the substrate below the BOX, contrary to the earlier belief. In this paper we will present an analytical model based on the Gunn theorem to describe ion induced charge collection in metal-oxide-semiconductor devices.

Measurement of charge collection profiles in irradiated silicon diodes by lateral IBIC technique

The control of the carrier lifetime profile in semiconductor power devices is of fundamental importance to optimize device parameters. With respect to traditional technologies such as diffusion of metallic impurities, light ion irradiation at low doses provides precise spatial localization of defects acting as carrier traps and recombination centres. Hence, the generation of suitable lifetime profiles obtained by controlling ion fluence and energy allows the reduction of turn-off times and switching losses in power electronic devices. In order to characterise the effects of ion irradiation on carrier lifetime profiles, we have used the ion beam induced charge collection (IBIC) technique in lateral geometry to measure charge collection efficiency (CCE) profiles in silicon p+/n/n+ diodes under different applied bias conditions before and after a frontal 6.5 MeV He++ ion implantation at a total fluence of 2 × 10 12 ions/cm 2. After the irradiation, the profile shows a clear drop of charge collection efficiency which occurs at the end of the ion range. The formalism based on Shockley–Ramo–Gunn’s theorem was applied to interpret the CCE profiles in both virgin and irradiated samples and to assess the free carrier lifetime profile modification following the radiation damage.