Samsung Electronics Co Ltd developed a memory cell technology for realizing a 3D ReRAM (resistive random-access memory) whose capacity is larger than that of NAND flash memory.
The new technology realizes a rewriting current of less than 1μA and a high nonlinearity of current-voltage properties, making it easy to prevent a current from flowing into non-selected cells. Also, Samsung confirmed that a 3D ReRAM using the new technology can be rewritten 107 times or more and that a 2-bit/cell multi-level cell can be realized by changing the conditions of current compliance.
Samsung has been engaged in the development of a 3D-structured ReRAM called "Vertical ReRAM (VRRAM)" in the aim of replacing NAND memory. The VRRAM technology enables to form stacked layers of memory cells in one process and reduce costs more than cross-point ReRAM technologies. It requires a memory cell that has a small writing current and nonlinear current-voltage properties to increase the density of memory cells by connecting many memory cells to each word line.
This time, Samsung enabled to control the density of oxygen vacancies, which determines current-voltage properties, within a desired range. And it inserted a tunnel-oxide film between the electrode and transition metal oxide film.
Through these improvements, Samsung realized the memory cell whose rewriting current is less than 1μA and current-voltage properties are nonlinear, it said.