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Observation of Ge2Sb2Te5 thin film phase transition behavior according to the number of cycles using Transmission Electron Microscope and Scanning Probe Microscope

Published online by Cambridge University Press:  01 February 2011

Hyunjung Kim ,
Sikyung Choi ,
Sukhoon Kang ,
Kyuhwan Oh  and
Soonyong Kweon
Hyunjung Kim
Affiliation:
khjung67@kaist.ac.kr, Korea Advanced Institute of Science and Technology, Dept. of Materials Science & Engineering, 373-1 Guseong-dong, Yuseong-gu, Daejeon, 305-701, Korea, Republic of, +82-42-869-4155, +82-42-869-3310
Sikyung Choi
Affiliation:
sikchoi50@kaist.ac.kr, Korea Advanced Institute of Science and Technology, Dept. of Materials Science & Engineering, 373-1 Guseong-dong, Yuseong-gu, Daejeon, 305-701, Korea, Republic of
Sukhoon Kang
Affiliation:
sangle77@snu.ac.kr, Seoul National University, School of Material Science and Engineering, San 56-1 Shillim-dong, Gwanak-gu, Seoul, 151-742, Korea, Republic of
Kyuhwan Oh
Affiliation:
kyuhwan@snu.ac.kr, Seoul National University, School of Material Science and Engineering, San 56-1 Shillim-dong, Gwanak-gu, Seoul, 151-742, Korea, Republic of
Soonyong Kweon
Affiliation:
sykweon@chungju.ac.kr, Chungju National University, Materials Science & Engineering, 123, Geomdan-ri, Iryu-myeon, Chungju, 380-702, Korea, Republic of
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Abstract

Recently, the development of information technology (IT) increases the demands of memory devices. Phase change random access memory (PRAM), based on the reversible phase change of the chalcogenide alloy, Ge2Sb2Te5, is widely regarded as a favourite candidate for the next generation memory. Because of PRAM has a simple cell structure with high scalability; it is non-volatile, has a relatively high read/write operation speed (Â50ns). The PRAM operation relies on the fact that chalcogenide-based materials can be reversible switched from an amorphous phase to a crystalline state by an external electrical current. It is important to study the electrical property with set/reset cycles, since film thickness shrinkage occurs with the phase transition.

In this work, we fabricated the 100nm amorphous Ge2Sb2Te5 thin film on TiN/Ti/Si substrate using dc-magnetron sputtering. The 50X50§2 isolated Ge2Sb2Te5 cell was lithographed by the lift-off pattern and wet etching. And TiN top electrode was deposited using pattern align process at room temperature after the SiO2 insulator CMP. Phase transition behavior with the set/reset cycle was observed using I-V measurement and transmission electron microscope (TEM) on isolated Ge2Sb2Te5 cell. The set/reset programming was operated using tungsten SPM tip which was fabricated using focused ion beam (FIB) lithography. I-V curve which was observed by the I-V probe clearly showed that the phase transition was occurred by applying the electric field through the I-V probe. The resistivity difference between amorphous and crystal state was more than 102. After the phase transition, it was also demonstrated with transmission electron microscope (TEM) analysis. For the preparation of TEM specimen of the amorphous and crystalline cell, focused ion beam (FIB) lithography was adopted.

Keywords

electrical propertiesscanning probe microscopy (SPM)transmission electron microscopy (TEM)
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 961: Symposium O – Nanostructured and Patterned Materials for Information Storage , 2006 , 0961-O03-04
Copyright
Copyright © Materials Research Society 2007

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