Materials World Network-- Ultrafast Switching of Phase Change Materials: Combined Nanosecond and Nanometer Exploration

Lead Research Organisation: Lancaster University
Department Name: Physics

Abstract

Flash memory, the present industry standard for solid state memory, is dependent on charge-sensing that is becoming increasingly difficult to scale. The non-volatile Phase Change Memory (PCM) is a promising alternative, as it is based on easier to detect resistance changes for locally switchable crystalline vs. amorphous states. Such PCM cells are generally configured as a chalcogenide film or rod sandwiched between two electrodes, where the amorphous/crystalline transition is achieved by quenching or slow cooling, respectively, after current induced heating beyond the glass transition temperature.There are multiple challenges for PCM that currently preclude them from becoming a mainstream solution for non-volatile memory, in the core of these lying the switching process itself. The dynamics of nucleation and crystallization on nanoscale are also an outstanding concern, as they will define the ultimate switching speeds and are implicated in challenges with bit retention, fidelity, and fatigue. The material science of this switching process is therefore of tremendous academic and industrial interest, including characterization of local electronic and thermal properties which define the ultimate resistance change and thermal diffusion length, respectively.To address these problems, this collaborative proposal between University of Connecticut, USA and Lancaster University, UK brings substantial and symbiotic expertise, specifically in novel quantitative measurements at the necessary simultaneous nanometer and spatial scales, including sub-surface and depth profile measurements for mapping the phase transition beneath an electrode as in practical memory cells. Such combined expertise, in critical for PCM materials development fields, presently do not exist in any single lab worldwide. The project involves industrial collaboration for both material and device development as well as instrumentation for materials phase change mapping in nanoscale devices. Primary emphasis on the local electronic and dynamic properties of PCM will be centered in the US, the local thermal and subsurface measurements will be rooted in the UK, with industrial collaborators based both in US (materials and devices) and UK (characterization). Interaction will be enhanced by annual faculty visits, month-long student exchanges, and round robin experiments. Project involves significant training and outreach component including project students visiting the foreign counterpart for an entire university term, leveraging the local expertise and capabilities for joint measurements and technology transfer while also benefitting from exposure to a different educational system.The proposal aims to develop a non-destructive in-situ methodology of real-time switching process in PCM materials. It is based on high speed nanoscale probing of electrical switching process, material sensitive ultrasonic force microscopy and nanoscale thermal characterization, where collaborating institutions have world leading expertise. That will allow to relate local material properties and heat transport with mechanical and chemical defects in PCM materials and devices, material transformation and switching phenomena, as well as to investigate approaches for improving switching fatigue. This research will lead to new PCM materials and improvement of key parameters of their processing and device engineering, with superior switching speed, data retention and switching fatigue and approaches for withstanding trends of decreasing dimensions and increasing bit density of modern memory devices.

Publications

10 25 50
 
Description It was found that a switching speed of a new generation of non-volatile memory based on phase-change materials (that may eventually replace both flash memory and RAM computer memory) can be significantly improved by the modification of thermal properties of such materials. It was also found that the density of the memory elements can be optimized by selection appropriate interfaces, leading to the larger memory chips. 3D mapping of materials and devices allowed to understand the synthesis conditions of multiple solid state applications.
Exploitation Route A new methodology for studying these phase-change materials as well as general semiconductor devices may find a way for the research and engineering in these fields.
Sectors Digital/Communication/Information Technologies (including Software),Electronics,Energy,Manufacturing, including Industrial Biotechology

 
Description A spin-out company LMA Ltd has been established, based on the now awarded US patent, impact in the optoelectronics UK industry has been demonstrated, with furher international impact for the semiconductor industry is being explored. EU patent has been also granted. Significant number of industrial samples have been studied using new BEXP method including semiconductor industry, chemical materials, biomaterials.
First Year Of Impact 2014
Sector Digital/Communication/Information Technologies (including Software),Electronics,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology
Impact Types Economic

 
Description European Commission (EC)
Amount £38,000 (GBP)
Funding ID FUNPROB 
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 06/2011 
End 06/2015
 
Description FP7 QUANTIHEAT
Amount € 586,000 (EUR)
Funding ID 604668 
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 12/2013 
End 11/2017
 
Description Paul Instrument Fund
Amount £100,000 (GBP)
Organisation The Royal Society 
Sector Charity/Non Profit
Country United Kingdom
Start 12/2017 
End 11/2019
 
Description UCONN-ULANC collaboration 
Organisation University of Connecticut
Department Institute of Materials Science
Country United States 
Sector Academic/University 
PI Contribution Multiple new research direction were explored with 3 publications in the main Physics and materials science journals resulting from it and two more in the preparation.
Collaborator Contribution Provided financial support for travel to the UCONN, access to equipment on the order of $400,000, with technical support on-site.
Impact Publications:Nanothermal characterization of amorphous and crystalline phases in chalcogenide thin films with scanning thermal microscopy Bosse, J., Timofeeva, M., Tovee, P., Robinson, B., Huey, B. & Kolosov, O. 7/10/2014 In : Journal of Applied Physics. 116, 13, 8 p., 134904 Research output: Contribution to journal > Journal article Nanomechanical morphology of amorphous, transition, and crystalline domains in phase change memory thin films Bosse, J., Grishin, I., Huey, B. & Kolosov, O. 30/09/2014 In : Applied Surface Science. 314, p. 151-157 7 p. Research output: Contribution to journal > Journal article Nanoscale mapping of in situ actuating microelectromechanical systems with AFM Rivas, M., Vyas, V., Carter, A., Veronick, J., Khan, Y., Kolosov, O. V., Polcawich, R. G. & Huey, B. D. 14/02/2015 In : Journal of Materials Research. 30, 3, p. 429-441 13 p. Research output: Contribution to journal > Journal article
Start Year 2014
 
Title METHOD AND APPARATUS FOR ION BEAM POLISHING 
Description )A method for forming a polished facet between an edge and a face of a sample, involves removing a first portion of the sample by directing an ion beam onto the edge adjacent the first portion along an ion beam axis to leave the polished facet. The ion beam axis lies on an ion beam plane oriented at a glancing incident angle, preferably from 1° to 30°, to a sample plane defined by and parallel to the first face. The ion beam is directed to flow from the edge towards the first face. Also disclosed is a sample preparation apparatus comprising a chamber adapted for evacuation with a sample holder adapted to hold a sample comprising a first face bounded by an edge, and an ion gun arranged to direct an ion beam along an ion beam axis towards the sample. The sample holder is configurable to position the sample relative to the ion beam such that a first portion of the sample is removable by the ion beam to leave a polished facet between the edge and the first face of said sample. The sample holder is configured to hold the sample whereby the ion beam axis lies on an ion beam plane oriented at an incident angle from 1° to 30° to a sample plane defined by and parallel to the first face of the sample. 
IP Reference WO2011101613 
Protection Patent application published
Year Protection Granted 2015
Licensed Yes
Impact Spin-off of Lancaster Materials Analysis in 2014.
 
Title METHOD AND APPARATUS FOR ION BEAM POLISHING US patent 9082587B2 
Description A method for forming a polished facet between an edge and a face of a sample, involves removing a first portion of the sample by directing an ion beam onto the edge adjacent the first portion along an ion beam axis to leave the polished facet. The ion beam axis lies on an ion beam plane oriented at a glancing incident angle, preferably from 1° to 30°, to a sample plane defined by and parallel to the first face. The ion beam is directed to flow from the edge towards the first face. Also disclosed is a sample preparation apparatus comprising a chamber adapted for evacuation with a sample holder adapted to hold a sample comprising a first face bounded by an edge, and an ion gun arranged to direct an ion beam along an ion beam axis towards the sample. The sample holder is configurable to position the sample relative to the ion beam such that a first portion of the sample is removable by the ion beam to leave a polished facet between the edge and the first face of said sample. The sample holder is configured to hold the sample whereby the ion beam axis lies on an ion beam plane oriented at an incident angle from 1° to 30° to a sample plane defined by and parallel to the first face of the sample. 
IP Reference WO2011101613 
Protection Patent granted
Year Protection Granted 2015
Licensed Commercial In Confidence
Impact A method for forming a polished facet between an edge and a face of a sample, involves removing a first portion of the sample by directing an ion beam onto the edge adjacent the first portion along an ion beam axis to leave the polished facet. The ion beam axis lies on an ion beam plane oriented at a glancing incident angle, preferably from 1° to 30°, to a sample plane defined by and parallel to the first face. The ion beam is directed to flow from the edge towards the first face. Also disclosed is a sample preparation apparatus comprising a chamber adapted for evacuation with a sample holder adapted to hold a sample comprising a first face bounded by an edge, and an ion gun arranged to direct an ion beam along an ion beam axis towards the sample. The sample holder is configurable to position the sample relative to the ion beam such that a first portion of the sample is removable by the ion beam to leave a polished facet between the edge and the first face of said sample. The sample holder is configured to hold the sample whereby the ion beam axis lies on an ion beam plane oriented at an incident angle from 1° to 30° to a sample plane defined by and parallel to the first face of the sample.
 
Title Method for ion beam polishing and polishing sample European Patent EP 2537017B1 
Description The present invention relates to a method for the preparation of samples having polished surfaces or facets suitable for the application of high resolution microscopy techniques such as electron microscopy, scanning probe microscopy and the like. In particular it relates to a method for forming highly flat and smooth cross-sections through device structures immediately adjoining a sample surface, to allow high resolution analysis of such device structures. For instance the invention relates to formation of facets on samples having epitaxial layers, multilayer structures, semiconductor thin films and the like where the structures and layers have sub-micrometre scale dimensions. When studying such device structures, it is desirable to achieve polished surfaces or facets with a roughness of the order of 1nm (root mean square peak-to-trough height) or better. 
IP Reference WO2011101613 
Protection Patent granted
Year Protection Granted 2016
Licensed Commercial In Confidence
Impact The invention allowed to establish a new business for theLancaster University spin-off Lancaster Materials Analysis and research collaboration with several industrial partners in UK, EU and USA.
 
Company Name Lancaster Materials Analysis 
Description Services to the industry and implementation of IP based on Lancaster patent US9082587 
Year Established 2014 
Impact Demonstrated potential for replacing TEM and SEM methods by less expensive in the characterization of semiconductor and optoelectronic structures
Website http://www.lancaster.ac.uk/news/articles/2014/novel-materials-analysis-technique-promises-to-reduce-...