A non-volatile memory has the advantage of ROM in that information stored therein is not erased even when power is not supplied and the advantage of RAM in that information can be easily input and output. Thus, the non-volatile memory is suitable for a mobile device such as a mobile phone, or the like. Examples of the non-volatile memory may include a resistive random access memory (RRAM), a magnetic random access memory (MRAM), a ferroelectric random access memory (FRAM), a phase-change random access memory (PRAM), and the like. Particularly, the resistive random access memory is one of the next-generation non-volatile memory devices with considerable competitiveness as compared with flash memory due to its features of low power, ultra-high speed, non-volatility, and simple structure.
A resistive random access memory device which has received a lot of attention as a next-generation memory device due to its high-density and low-power characteristics may increase or decrease an electric resistance using an electric signal to record information depending on a resistance state. The resistive random access memory device employs a simple device structure (metal/oxide/metal) and is configured to switch from a high resistance state unsuitable for conduction to a low resistance state suitable for conduction when an appropriate voltage/current is applied. These two resistance states are distinguished by a difference between “0” and “1” and the resistive random access memory device refers to a memory device that recognizes the resistance states. Resistive random access memory devices are classified in more detail into a phase-change access memory (PRAM) using phase change, a magnetic RAM (MRAM) using spin change, and a Resistive RAM (RRAM) using the movement of ions in a material, depending on a method of switching a resistance in a material.
The resistive random access memory device has a structure in which an upper electrode and a lower electrode are placed on a thin film and a resistance change layer formed of an oxide thin film is interposed between the upper and the lower electrodes. The memory operates by changing the resistance of the resistance change layer depending on a voltage applied to the resistance change layer.
The resistance of the resistive random access memory device is changed as a metal filament is formed and eliminated by redox reactions of metal atoms or metal ions permeating from a metal electrode into the resistance change layer depending on a voltage applied to the resistance change layer. As materials of the resistance change layer, solid electrolyte materials such as oxides or GeS have been used mainly. However, an oxide-based solid electrolyte material shows a very unstable distribution of HRS/LRS resistances and SET/RESET voltages and it is very difficult to manipulate them. Accordingly, the development of new materials of the resistance change layer is needed to solve this problem.
Korean Patent Laid-open Publication No. 2017-0049758 discloses a resistance change memory device including an organic-inorganic hybrid perovskite as a resistance change layer and a method for fabricating the same. However, RNH3MX1nX2(3-n) perovskite (R may be a C1-C3 alkyl group, a C5-C7 cycloalkyl group, or a C6-C20 aryl group, M may be a divalent metal ion, X1 and X2 may be halogen ions different from each other, and n is a real number of from 0 to 3) which has been used for a resistance change layer in a perovskite-based resistive random access memory device has low voltage and high efficiency, but a perovskite thin film itself shows low moisture and light stability and low durability. Therefore, a resistance change layer having a new structure capable of improving the stability and durability is needed.
USPTO Backgrounds
USPTO Backgrounds