High-energy Ion Microbeam Research Articles

Development of single-event-effects analysis system at the IMP microbeam facility

Single-event-effects (SEEs) in integrated circuits (ICs) caused by galactic single ions are the major cause of anomalies for a spacecraft. The main strategies to decrease radiation failures for spacecraft are using SEEs less-sensitive devices and design radiation hardened ICs. High energy ion microbeam is one of the powerful tools to obtain spatial information of SEEs in ICs and to guide the radiation hardening design. The microbeam facility in the Institute of Modern Physics (IMP), Chinese Academy of Science (CAS) can meet both the liner energy transfer (LET) and ion range requirements for SEEs simulation experiments on ground. In order to study SEEs characteristics of ICs at this microbeam platform, a SEEs analysis system was developed. This system can target and irradiate ICs with single ions in micrometer-scale accuracy, meanwhile it acquires multi-channel SEE signals and maps the SEE sensitive regions online. A 4-Mbit NOR Flash memory was tested with this system using 2.2GeVKr ions, the radiation sensitive peripheral circuit regions for SEEs of 1 to 0 and 0 to 1 upset, multi-bit-upset and single event latchup have been obtained.

Micromachining of silicon with a proton microbeam

In the recent years the fabrication of sensors and actuator devices on a microscopic scale and their integration with electronic devices and micro-electromechanical systems (MEMS) has become an area of considerable commercial and technological interest, with huge development potentialities. High energy ion microbeam is a suitable tool for such purposes. In this paper we present an alternative way to exploit the lithographic properties of micro ion beams based on the selective damage of silicon to produce porous silicon microstructures.We used a 2 MeV proton microbeam to irradiate definite areas of silicon samples in order to produce damaged layers localised at the end of the proton trajectories. By performing an electrochemical etching in a suitable HF solution, a porous silicon pattern, complementary to the irradiated one, is always formed. The main effect of the damage on the porous silicon formation is to reduce the velocity of formation. To interpret this, such dead layers can be seen to be more or less opaque to the migration of free holes. Consequently the patterned region can be more or less revealed according to the formation time. The procedure allows for the production of microstructures of porous silicon whose unique properties are of great interest for applications.Preliminary results obtained on silicon samples, with different doping levels (p+, p, n+) and irradiating regions with different areas (from 200×200 μm2 to 25×25 μm2) are presented in order to evaluate the most suitable range of exposure and aspect-ratio of the microstructures.

Micromachining using deep ion beam lithography

In recent years the process combining deep X-ray lithography with electroforming and micromoulding (i.e. LIGA), has become an important technique for the production of high aspect-ratio microstructures for the fabrication of micro-electromechanical systems (MEMS). The aim of this paper is to investigate the potential of high energy ion microbeams for carrying out similar micromachining, and in particular for overcoming the geometrical restrictions which are inherent in deep x-ray lithography. Using a scanned 2.0 MeV proton beam of approximately 1 micron diameter, we produced latent microstructures in high molecular weight PMMA resist. These resist microstructures were subsequently developed using a multi-component developer which is highly specific in the removal of exposed resist, while leaving unexposed or marginally exposed material unaffected. A suitable range of exposures has been established, and factors affecting the geometrical fidelity of the produced microstructure have been investigated. The relative advantages and limitations of this technique vis à vis deep X-ray lithography are discussed.

Optimization of an rf ion source for production of a high-energy ion microbeam

A unit has been designed and implemented expressly for the measurement of brightness, energy spread and mass composition of the ion beam extracted from an ion source. This unit has been used for investigation of the main ion optical characteristics of standard and modified rf ion sources. A magnet system (“mirror” type) consisting of permanent magnet and ferrite materials has been used in the modified rf ion source. The capabilities and advantages of this source are shown in this paper.

Single-event current transients induced by high energy ion microbeams

Focused high-energy ion microbeams were applied to the study of the basic mechanisms of single-event upset. Waveforms of the current transients induced by He-, C-, O- and Fe-ion strikes on silicon diodes were measured by applying extremely low beam currents of an order of 10 fA and a wide-bandwidth digitizing sampling technique. Total collected charges are evaluated from the transient currents as a function of LET (linear energy transfer), bias voltage, and doping level, and are compared with theoretical values calculated using conventional single-event models. It is found that irradiation effects on the total collected charges can be explained by the introduction of displacement atoms calculated using Coulomb potential and the Kinchin-Pease model.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Study of basic mechanisms of single event upset using high-energy microbeams

High-energy ion microbeams were applied to the study of basic mechanisms of single event upset (SEU). Current transients induced in silicon p-n junction diodes by single ion strikes of a 2 MeV helium ion microbeam were measured by using a high-speed digitizing sampling technique. Clear and reproducible current transients were obtained without any trace of pulse pileup. The influence of the radiation damage on the current transients is discussed in conjunction with the digitizing sampling method.