Influence of the adjacent layers on the crystallization kinetics of Ge 2 Sb 2 Te 5 thin films
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Influence of the adjacent layers on the crystallization kinetics of Ge2Sb2Te5 thin films Alexey Yakubov1 · Alexey Sherchenkov1 · Alexey Babich1 · Petr Lazarenko1 · Irina Sagunova1 · Elena Kirilenko2 Received: 20 August 2019 / Accepted: 29 June 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract The influence of the adjacent layers (SiO2, Al, Ni, Ti, W, TiN, TiN/W) on the crystallization kinetics of G e2Sb2Te5 thin films was investigated using the techniques based on the application of two different methods—differential scanning calorimetry and measurements of the resistivity temperature dependences. Thin films were deposited by the magnetron sputtering. The composition of the films was determined by the Auger spectroscopy and was close to G e2Sb2Te5. X-ray diffraction was used to investigate the structure of thin films and showed that the as-deposited films were in an amorphous state, while heat treatment at 250 °C for 30 min led to the crystallization to the cubic (rock salt) phase. Effective activation energy of crystallization obtained by differential scanning calorimetry at the beginning of the crystallization was 1.8 eV and then slightly decreased to 1.7 eV at the end of the process. The values of the effective activation energy obtained from the measurements of the resistivity temperature dependences were in the range of 2.5–2.9 eV at the beginning and in the range of 2.2–3.5 eV at the end of the crystallization process. The difference in the effective activation energies of crystallization for the GST225 thin films deposited on the different sublayers is caused by the influence of the neighboring sublayers on the crystallization process. It was found that crystallization temperatures correlate with the effective activation energies and increase with their growth. Keywords Phase-change memory · Ge2Sb2Te5 · Kinetics of crystallization
Introduction Currently, the phase-change memory (PCMe) is considered to be one of the promising candidates for the next generation of nonvolatile memory devices due to the high operation speed, low power consumption, high endurance, extended scalability and compatibility with CMOS technology [1–3]. Recent investigations are directed on the development of the PCMe with the multi-level cells, which allows to store the multiple bits in the memory cell and is powerful method to increase the data density and reduce the cost per bit [4–7]. Compositions in ternary system Ge–Sb–Te (GST) are widely studied as active layers for PCMe devices, in particular Ge2Sb2Te5 (GST225), due to the high stability at room temperatures and fast crystallization rate [3, 8, 9]. * Alexey Yakubov [email protected] 1
National Research University of Electronic Technology, Bld. 1, Shokin Square, Zelenograd, Moscow, Russia 124498
Nanotechnology Institute of Microelectronics of RAS, Bld. 16A/11, Nagatinskaya street, Moscow, Russia 115487
2
The working principle of such memory is based on the reversible phase transition between the crystalline state with low resistivity and amorphous sta
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