Innovative Nanocomposites for Low Power Phase‐Change Memory: GeTe/C Multilayers

Abstract

Innovative nanocomposites consisting of [(GeTe)4 nm/C1 nm]10 multilayers (MLs) deposited by magnetron sputtering are integrated in phase‐change memory (PCM) test devices with a “wall structure.” Scanning transmission electron microscopy (STEM) shows that an ML structure, with crystallized GeTe layers, is kept after integration in as‐fabricated devices and also after an additional annealing of the devices at 425 °C. The programming current (RESET current) required to reach the high resistance state of [(GeTe)4 nm/C1 nm]10 ML devices decreases by 45% after annealing at 425 °C. The reduction in RESET current is 55% and the reduction in drift coefficient is about 40% in ML devices annealed at 425 °C compared to similar devices incorporating Ge2Sb2Te5. STEM imaging, coupled with nano‐beam electron diffraction and electron energy loss spectroscopy, of ML devices in the high resistance state shows that the RESET current reduction after annealing is correlated to a reduction of the amorphized volume.

Nanocomposites of chalcogenide phase-change materials: from C-doping of thin films to advanced multilayers

“…Indeed, we have recently succeeded in integrating a [GeTe 4 nm/C 1 nm] 10 ML into phase-change memory test devices and have observed a significant improvement in programming performances. 37 A reduction in the RESET current of about 55% and in drift coefficient of about 40% in ML devices annealed at 425 °C were observed in comparison with similar devices incorporating the Ge 2 Sb 2 Te 5 reference PCM. Similar trends have been observed in devices based on GST/C MLs.…”

“…The annealing conditions (15 minutes at 300°C) were chosen to mimic those encountered during integration into memory devices in our test vehicles. [37] Alternating layers of GeTe and C are observed throughout the stack between the SiO 2 substrate and the SiN capping layer, with well-defined interfaces between the GeTe and C layers. As expected from the R s curve in Fig.…”

“…Moreover, the fact that a ML nanostructure is retained after annealing at 400-450°C allows the integration of these MLs in memory devices, as we have recently shown. [37]…”

Sb2Te3/TiTe2‐Heterostructure‐Based Phase Change Memory for Fast Set Speed and Low Reset Energy

“…[16][17][18][19][20] Finally, Sb 2 Te 3 /GeTe, crystalline Sb 2 Te 3 / TiTe 2 , GeTe/C, Ge 8 Sb 92 /Ge, C/Sb, Zn 15 Sb 85 /Ga 30 Sb 70 , and Cr 7 Ge 33 Te 60 /Hf 16 Ge 6 Sb 78 are constructed using two different materials to improve performance using two different properties. [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] In this work, an amorphous Sb 2 Te 3 /TiTe 2 heterostructure was fabricated using a magnetron sputtering system at room temperature, and a PCM device was fabricated by introducing the Sb 2 Te 3 /TiTe 2 heterostructure. A PCM was fabricated by inserting several nanolayers of TiTe 2 with low thermal conductivity and high electrical conductivity inside the Sb 2 Te 3 layer with fast switching speed operation characteristics.…”

Phase‐Change and Ovonic Materials (Third Edition)

“…Thus, these results show the potential of iPCMs for applications in neuromorphic computing with high accuracy. By using a same approach than iPCM stacks employing PCM‐based heterostructures, Terebenec et al [ 3 ] demonstrated that integration in memory devices of GeTe 4nm /C 1nm multilayers (MLs) to achieve innovative PCM nanocomposites is a promising system to improve PC memory performance. Indeed, GeTe/C MLs memory devices exhibit significantly reduced programming energy compared with standard PCM devices probably due to an increase of thermal confinement within the memory cell resulting from the reduced thermal conductivity of polycrystalline GeTe/C MLs.…”