Variable Resistance Memory Control Circuit Voltage Thresholding
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Solution Overview
Problem
Conventional programming methods for variable resistance nonvolatile memory elements fail to reliably set resistance states, leading to held low or high resistance states that result in data errors due to incomplete resistance value changes.
Innovation Solution
A nonvolatile memory device with a control circuit that applies voltages of different polarities to change resistance states, determining whether the resistance value meets a threshold before applying specific voltages to ensure accurate state changes, preventing held states by adjusting voltage values based on resistance state conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a predetermined voltage is applied to change resistance state, then resistance state changes between high and low, but held low or held high resistance states occur causing data errors
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the voltage magnitude based on the current resistance state. When transitioning from high resistance state (HRS) to low resistance state (LRS), the voltage is set to a first magnitude; when transitioning from LRS to HRS, the voltage is set to a second magnitude different from the first. This differential voltage approach prevents held states by matching the voltage parameter to the specific transition required, ensuring reliable resistance state changes without causing data errors.
2Ease of operation
If simple voltage application method is used, then operation is easy, but held resistance states occur leading to data errors
Solution Approach 1:
The patent implements feedback by determining the current resistance state before applying the programming voltage. The control circuit assesses whether the memory element is in HRS or LRS, then selects the appropriate voltage magnitude based on this feedback. This closed-loop approach maintains ease of operation through automated state detection while ensuring reliability by preventing held states through appropriate voltage selection matched to the current resistance condition.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively inhibits held low and high resistance states, ensuring reliable data storage by controlling voltage values to achieve desired resistance states in variable resistance nonvolatile memory elements.
Implementation Method 1
a variable resistance layer a resistance state of which reversibly changes between a high resistance state and a low resistance state in which a resistance value of the variable resistance layer is smaller than the resistance value in the high resistance state, based on electrical signals having different polarities which are given between the first electrode and the second electrode
Data Source
AI summary
A nonvolatile memory device (800) includes a variable resistance nonvolatile memory element (100) and a control circuit (810). The control circuit (810) determines whether a resistance value of the nonvolatile memory element (100) in a high resistance state is equal to or greater than a predetermined threshold value. Moreover, if the resistance value of the nonvolatile memory element (100) in the high resistance state is smaller than the threshold value, the control circuit (810) applies a first voltage (VL1) to the nonvolatile memory element (100) to change a resistance state of the nonvolatile memory element (100) from the high resistance state to the low resistance state. Moreover, if the resistance value of the nonvolatile memory element (100) in the high resistance state is equal to or greater than the threshold value, the control circuit (810) applies to the nonvolatile memory element (100) a second voltage (VL2) an absolute value of which is smaller an absolute value of the first voltage (VL1) to change the resistance state of the nonvolatile memory element (100) from the high resistance state to the low resistance state.