Forming method of performing forming on variable resistance nonvolatile memory element, and variable resistance nonvolatile memory device

Abstract

In forming, an automatic forming circuit (210) included in a nonvolatile memory device (200) causes a constant current IL to flow in a selected memory cell having a considerably high initial resistance. When the forming generates a filament path in the memory cell and thereby a resistance value is decreased, a potential of a node NBL and a potential of a node Nin are also decreased. If the potentials become lower than that of a reference voltage Vref, an output NO of a difference amplifier (303) for detecting forming success is activated, and a forming success signal Vfp is activated after a delay time depending on the number n of flip flops FF1 to FFn and a clock signal CLK. Thereby, a switch transistor (301) is in a non-conducting state and the forming on a variable resistance element is automatically terminated.

Description

technical field [0001] The present invention relates to a method for forming (initializing) a variable resistance nonvolatile memory element whose resistance value is reversibly changed in response to an electric signal to stably change resistance, and a variable resistance nonvolatile memory having that function device. Background technique [0002] In recent years, variable resistance nonvolatile memory devices (hereinafter also simply referred to as "Non-volatile memory device".) research and development. The so-called variable resistance element refers to an element that has the property that the resistance value changes reversibly according to an electric signal, and can store data corresponding to the resistance value in a non-volatile manner. [0003] As a nonvolatile memory device using a variable resistance element, a nonvolatile memory device in which so-called 1T1R type memory cells are arranged in a matrix is ​​generally known. A MOS transistor and a variable ...

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Problems solved by technology

[0045] However, the above-mentioned conventional resistance variable semiconductor memory device has a problem that the formation voltage is not uniform for each resistance variable element constituting the memory cell array, or that the initial voltage applied to the resistance to transition to the state where the resistance change starts is The formation voltage of the change element becomes higher

In addition, although it will be described in detail later, it is clear that there is another problem in the formation method according to the related invention for solving such a problem that the cell current in the low-resistance state decreases (that is, the low resistance of the resistance variable element Insufficient resistance value in the state becomes low)

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