Special technique at PETRA III propels memory technology
New resistive switching memory modules come to prototype phase
Scientists have developed an in-operando Hard X-Ray Photoelectron Spectroscopy (HAXPES) at PETRA III as key diagnostics for transferring basic materials research insights to redox-based resistive switching memory (ReRAM) prototyping development in the field of wireless sensor network applications.
High performance materials in modern societies are often determined by the related defect physics and chemistry. These defects might have either a detrimental influence (e.g. crack formation by dislocations in the area of construction) and must be avoided or are introduced on purpose to functionalize materials (e.g. oxygen engineering for ionic transport in solid oxide fuel cells for energy). In any way, either to avoid the worst or to improve for the best, defect control is a key factor in engineering innovative materials. However, in especial non-destructive defect characterization with high sensitivity and energy resolution on the nano-scale remains one of the most daunting challenges in modern material science. A team of scientists at PETRA III has now improved a technique to characterize these effects and utilised it to investigate a new generation of memory modules which is now on its way to be built as highly integrated prototypes. Redox-based resistive switching memory, so called ReRAM, is an innovative approach towards the “universal memory” concept to greatly improve the performance of functionalized microelectronics, for example in the field of low-power wireless communication applications in telemedicine, agriculture, industry automation and environmental monitoring.
PETRA III, one of the world`s most brilliant synchrotron sources in the hard X-ray regime at DESY in Hamburg, hosts at its beamline P09 a newly developed experimental method which allows for unprecedented insights in chemical and electronic properties of functional materials, including defect characterization on the nano-scale. The Hard X-ray Photoelectron Spectroscopy (HAXPES) technique combines the high energy resolution of classical photoelectron spectroscopy with strongly enhanced information depth, allowing thus for example for non-destructive materials science studies of buried interfaces in microelectronic devices. Photoelectron spectroscopy is often used in materials science to get information about chemical composition and physical structure of a material. An incoming X-ray beam excites the material´s atoms to send out electrons. By detecting the properties of the electrons by an external detector, one can determine the inner structure of complex materials.
A team of materials scientists from the Helmholtz Forschungszentrum Jülich , the Leibniz Institute for innovative microelectronics (IHP) in Frankfurt (Oder) and DESY uses this newly established HAXPES technique to unveil the physics of ReRAM devices. Here, the non-volatile memory mechanism is controlled by electrical pulses, causing reversible resistance changes in a few nanometer thick insulator layer sandwiched between two metal electrodes. In-operando HAXPES studies at PETRA III allows to study the switching characteristics of a single memory device in various resistance states and demonstrated thus the central importance of the metal / insulator interface defect chemistry and physics (i.e. the role of oxygen vacancies) for the switching characteristics.“PETRA III is among the best positioned synchrotron light sources in the world in the emerging area of HAXPES research; and this is the reason why we consider it the best place to be for our technology-related ReRAM ambitions,” claim Regina Dittmann and Malgorzata Sowinska from FZ Jülich and IHP, respectively.
These basic research insights are currently transferred to the processing of fully integrated 4 kbit ReRAM test modules, prepared in IHP´s Silicon Bipolar CMOS prototyping research clean room by strong support from IHP´s Technology and System departments. The aim of the research team is to evaluate the performance of embedded ReRAM modules for wireless sensor networks in close collaboration with the semiconductor foundry X-FAB from Germany. These tiny, but incredibly complex microelectronics systems are becoming more and more our electronic assistants, running in the background of many daily life applications.
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