Ion Beam Induced Charge Microscopy Research Articles

4H-SiC Schottky diode radiation hardness assessment by IBIC microscopy

We report findings on the Ion Beam Induced Charge (IBIC) characterization of a 4H-SiC Schottky barrier diode (SBD), in terms of the modification of the Charge Collection Efficiency (CCE) distribution induced by 20 MeV C ions irradiations with fluences ranging from 20 to 200 ions/μm2.The lateral IBIC microscopy with 4 MeV protons over the SBD cross section, carried out on the pristine diode evidenced the widening of the depletion layer extension as function of the applied bias and allowed the measurement of the minority carrier diffusion lengths.After the irradiation with C ions, lateral IBIC showed a significant modification of the CCE distribution, with a progressive shrinkage of the depletion layer as the fluence of the damaging C ions increases.A simple electrostatic model ruled out that the shrinkage is due to the implanted charge and ascribed the perturbation of the electrostatic landscape to radiation-induced defects with positive charge state.

IBIC microscopy – The powerful tool for testing micron – Sized sensitive volumes in segmented radiation detectors used in synchrotron microbeam radiation and hadron therapies

Ion Beam Induced Charge (IBIC) microscopy performed using highly tuned microbeams of accelerated ions with energies in the MeV range is the powerful tool for analysis of charge carrier transport properties in semiconductor devices based on semiconductor hetero-junction, metal-on-semiconductor and semiconductor-on-insulator configurations. Here we present two cases of recent applications of the IBIC microscopy in the field of medical radiation physics. The reduced-rate ion microbeams with energies in the MeV range and sub-micrometer spot-sizes have been used for the investigations of the charge collection efficiency (CCE) in sensitive volumes of segmented radiation detectors in order to measure the spatial distribution and uniformity of CCE in different polarization conditions. This information allows the determination of the charge carrier transport properties in selected substructures of a particular device and to quantify its ability to accurately determine the energy deposited by incident ionizing radiation - two fundamental requirements of any microdosimeter or detector of ionizing radiation.

The establishment and performance of IBIC microscopy at Fudan University

The ion beam induced charge (IBIC) microscopy was developed in the early 1990’s as a means of imaging device depletion regions and dislocations in semiconductor wafers. To better understand the operation performance of the micro-electronic devices and semiconductor radiation detectors, the IBIC microscopy was established on the microprobe system at Fudan University. A customized target holder was designed, on which the CdZnTe detector is fixed with adhesive tape.In this work, the device performance of a CdZnTe detector was evaluated using the established IBIC technique and we primarily choose the appropriate bias voltage and have successfully used the frontal IBIC to evaluate the quality of one CdZnTe detector. What’s more, the regions of the crystal defect and ion beam-induced radiation damage can be localized accurately.

Study on the bias-dependent effects of proton-induced damage in CdZnTe radiation detectors using ion beam induced charge microscopy

The influence of damage induced by 2MeV protons on CdZnTe radiation detectors is investigated using ion beam induced charge (IBIC) microscopy. Charge collection efficiency (CCE) in irradiated region is found to be degraded above a fluence of 3.3×1011p/cm2 and the energy spectrum is severely deteriorated with increasing fluence. Moreover, CCE maps obtained under the applied biases from 50V to 400V suggests that local radiation damage results in significant degradation of CCE uniformity, especially under low bias, i. e., 50V and 100V. The CCE nonuniformity induced by local radiation damage, however, can be greatly improved by increasing the detector applied bias. This bias-dependent effect of 2MeV proton-induced radiation damage in CdZnTe detectors is attributed to the interaction of electron cloud and radiation-induced displacement defects.

Radiation hardness of single crystal CVD diamond detector tested with MeV energy ions

The spectroscopic properties of a commercial high purity single crystal diamond detector (1mm2 area, 500μm thickness) have been studied using focused ion beams (H, He and C ions) in the MeV energy range. A measured relative energy resolution of 1.3% (FWHM=25keV) for the detection of 2MeV protons demonstrated a good spectroscopic performance of the CVD diamond device, which makes it useful for the detection of light ions or atoms. To test the radiation hardness of the diamond detector, it was selectively irradiated with a 6.5MeV focused carbon beam up to a fluence of 1011 ions/cm2. Reliable measurement of the ion fluence was accomplished by means of the microprobe single ion technique IBIC (ion beam induced charge). After irradiations that produced selectively damaged regions in the diamond detector, low current mode IBIC microscopy has been performed to measure the degradation of the charge collection efficiency (CCE). In order to get a better understanding of the detector performance after irradiation, different ions with the end of a range smaller, equal and larger than the extend of the damaged layer were used as IBIC probes. The same experimental procedure of irradiation and IBIC microscopy has been performed on a detector grade silicon PIN diode in order to directly compare the radiation hardness of diamond and silicon. The presented results show that the single crystal CVD diamond is less radiation hard for the spectroscopy of short range heavy ions compared to the high resistivity silicon, which is contrary to the results obtained for diamond detectors exposed to the high energy particles.

A review of ion beam induced charge microscopy

Since its development in the early 1990’s, ion beam induced charge (IBIC) microscopy has found widespread applications in many microprobe laboratories for the analysis of microelectronic devices, dislocations, semiconductor radiation detectors, semi-insulating materials, high power transistors, charge-coupled arrays, solar cells, light emitting diodes, and in conjunction with Single Event Upset imaging. Several modalities of the techniques have been developed, such as lateral IBIC and time-resolved IBIC. The theoretical model of IBIC generation and collection has developed from a one-dimensional model of charge drift and diffusion to a detailed model of the motion of ion charge carriers in semiconductors and insulators. This paper reviews the current state-of-the-art of IBIC theory and applications.

Ion beam induced charge microscopy studies of power diodes

Ion beam induced charge microscopy (IBIC microscopy) has been established recently as ananalytical tool for the characterization of various types of semiconductor devices. In thispaper the potential of IBIC microscopy for the analysis of deeply buried structures of highpower devices under biases of more than 2 kV is discussed. Such data are useful inthe design process of high power devices because excessive fields at device edgeregions or within protection elements (e.g. field ring structures) can be avoided.Since charge collection efficiency within depleted pn junctions is typically 100% for IBIC analysis, the contrastdue to E-field variations within the large depletion regions of high power devices is limited. Here wewill introduce a new approach for enhancing this contrast by using the temporalinformation from the IBIC signals gained with a transient IBIC set-up. Simulations andexperimental data will be compared to evaluate the suitability of the new approach. Thedevice used here is a high voltage diode with a field ring structure which was analysedusing a 2 MeV proton beam.

IBIC analysis of high-power devices

The technique of ion beam induced charge microscopy (IBIC microscopy) has been used for several years to analyse integrated circuits, radiation detectors and solar cells [H. Schöne, D.N. Jamieson, MRS Bull. 25 (2000) 14]. In this work, results from a first attempt to investigate high-power devices with this technique are reported. It is demonstrated that IBIC analysis allows the characterisation of layers of different doping types located several tens of microns below the sample surface with an ion beam energy of 2 MeV. The devices investigated are high-power light-triggered thyristors [M. Ruff, H.-J. Schulze, U. Kellner, IEEE (ED) 46 (1999) 1768; F.-J. Niedernostheide, H.-J. Schulze, J. Dorn, U. Kellner-Werdehausen, D. Westerholt, in: Proceedings of the 12th International Symposium on Power Semiconductors and IC's, ISPSD'2000, Toulouse, France, 2000, p. 267].

Analysis of high-power devices using proton beam induced currents

Ion beam induced charge microscopy (IBIC microscopy), a new technique which utilizes a focused beam of high energy (several MeV) protons, has been used to analyse various semiconductor structures, e.g. microelectronic circuits, radiation detectors, solar cells and CVD diamond thin films [1, 2]. Here we report the first attempt to investigate high power devices with this technique. It is demonstrated that IBIC analysis allows the characterisation of layers of different doping types located several tenths of microns below the sample surface using an ion beam energy of 2 MeV. The devices investigated are high-power light-triggered thyristors.

A comparison between the use of EBIC and IBIC microscopy for semiconductor defect analysis

The use of 3 MeV protons for ion beam induced charge (IBIC) and 15 keV electrons for electron beam induced current (EBIC) microscopy to image MeV proton induced defects in silicon are compared here. It is shown that IBIC is considerably more sensitive to the detection of very deep defects because of the greater range of 3 MeV protons compared with 15 keV electrons. An analysis based on the different ranges of the two charged particles is used to calculate the difference in defect contrast, and good quantitative agreement is shown with measured contrast values.

Simulation of pulse height spectra in ion beam induced charge microscopy of polycrystalline silicon

This article describes computer simulations of the charge pulse height spectra that are obtained by irradiating selected regions of a polycrystalline silicon solar cell by a 2 MeV He+microbeam. The spectra are calculated in terms of the energy loss function of the ions and the distribution of the charge collection probability at a grain boundary, and illustrate the effect of the interface recombination velocity of the grain boundary and the bulk diffusion length. The simulations are compared with some experimental spectra to demonstrate the applicability of the theory. The method can be extended to the analysis of other semiconductor defects or more complex devices.

Recent results in ion beam induced charge microscopy: Unconnected junction contrast and an assessment of single contact IBIC

The recent development of Ion Beam Induced Charge Microscopy (IBIC) promises to deliver a powerful imaging tool for the analysis of active regions in microelectronics devices. The high penetration power (47 μm for 2 MeV protons in Si) allows direct high resolution access to buried structures, a feature not available to the well established EBIC (Electron Beam Induced Current) technique. As multi-level designs become more prevalent this deep penetration is a significant advantage. We report several results: firstly, that contrast is present in IBIC images from junctions that are not directly connected to the preamplifier. The contrast from unconnected junctions vanishes if these junctions are short circuited. Secondly, we discuss the degradation of IBIC images under prolonged irradiation for protons and He + ions. Finally, we discuss the feasibility of single connection IBIC imaging. We demonstrate that IBIC imaging is possible with only one connection to the device substrate.

Unconnected junction contrast in ion beam induced charge microscopy

A new contrast mechanism in ion beam induced charge imaging in semiconductors is reported. Junctions not directly connected to the charge collection preamplifier were found to give rise to significant charge collection signals. Imaging with these signals is carried out, thus enabling the mapping of junctions not directly connected to the charge collection amplifier.

Ion beam induced charge microscopy for the analysis of integrated circuits

Ion beam induced charge (IBIC) microscopy provides a means of imaging the depletion layers of working microelectronic devices beneath their thick metallizaion and passivation layers. The concept of IBIC microscopy is outline, its advantages over optical and electron microscopy techniques are outlined, its advantages over optical ad electron micorscopy techniques are described, and examples of images are presented. One particular application is as a way of identifying device components that are susceptible to having their logic state altered by cosmic rays when used in satellites, for example.

Optimization of ion-beam induced charge microscopy for the analysis of integrated circuits

The conditions necessary for obtaining both the maximum topographical image contrast and the maximum insensitivity to ion induced damage using ion-beam induced charge microscopy are presented and interpreted in terms of existing energy loss and damage theory. Ion-beam induced charge images and pulse-height spectra which are measured from a Sandia SA3002 memory device using MeV H+, H+2, and 4He+ ions with a range of incident energies are used to characterize these optimum experimental conditions. It is shown that ions which are stopped within the device depletion layers generate charge pulses which are much less sensitive to ion induced damage than longer range ions which are stopped in the device substrate.