Variable Resistance Memory Element Sidewall Oxidation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for manufacturing nonvolatile semiconductor memory elements face challenges in achieving stable resistance changes at low voltage and high speed, with oxidation of the diode element leading to degradation of rectification and current drive capability, affecting the initial breakdown and rewriting processes.
Innovation Solution
A method involving the oxidation of the sidewall portion of the variable resistance element before patterning the diode element's top electrode, using a conductive film as a barrier to prevent oxygen diffusion and reduce the active area, along with the inclusion of materials like tantalum oxide, hafnium oxide, or zirconium oxide in the variable resistance layer for improved retention characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxidation is performed to stabilize resistance change in the variable resistance layer, then reliability of resistance change is improved, but leakage current increases and initial breakdown voltage becomes unstable
Solution Approach 1:
The variable resistance layer is divided into multiple sub-layers with different oxygen content atomic percentages (e.g., 40-60% in the first sub-layer, 60-80% in the second sub-layer). This segmentation allows each sub-layer to serve different functions: the lower oxygen content sub-layer provides stable resistance change, while the higher oxygen content sub-layer reduces leakage current and stabilizes initial breakdown voltage.
Solution Approach 2:
Different regions of the variable resistance layer are given different oxygen content atomic percentages to achieve different local properties. The first sub-layer (closer to the electrode) has lower oxygen content for stable resistance modulation, while the second sub-layer (farther from electrode) has higher oxygen content for leakage suppression and breakdown voltage stabilization.
2Reliability
If voltage is applied for initial breakdown to enable resistance change, then functionality of memory element is achieved, but distribution of voltage to parasitic resistance components increases
Solution Approach 1:
The variable resistance layer is pre-configured with specific oxygen content gradients during manufacturing (40-60% in first sub-layer, 60-80% in second sub-layer) to prepare the structure for optimal initial breakdown characteristics. This preliminary structuring ensures that when voltage is applied, the breakdown occurs at stable, predictable voltages with minimal parasitic effects.
3Object-generated harmful factors
If active area of variable resistance layer is reduced to lower leakage current, then leakage current is reduced, but current drive capability of diode element is degraded
Solution Approach 1:
The variable resistance layer uses spatially varying oxygen content to achieve different local functions: the first sub-layer with 40-60% oxygen content maintains sufficient active area for current drive capability, while the second sub-layer with 60-80% oxygen content suppresses leakage current. This local quality differentiation resolves the contradiction between leakage reduction and current drive maintenance.
Solution Approach 2:
The variable resistance layer is constructed as a composite structure with multiple sub-layers having different oxygen content atomic percentages. This composite approach combines the benefits of low-oxygen regions (stable resistance change, sufficient current drive) and high-oxygen regions (leakage suppression, breakdown voltage stability) within a single functional layer.
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
This approach reduces leakage current, lowers the initial breakdown voltage, and enhances the current drive capability of the diode element, enabling stable operation at low voltage and high speed, while preventing degradation of the diode element's characteristics.
Implementation Method 1
a variable resistance layer in which transition metal oxides of different oxygen content atomic percentage are stacked
Implementation Method 2
selectively causing the occurrence of oxidation/reduction reaction in an electrode interface which is in contact with a variable resistance layer
Implementation Method 3
using a conductive film as a barrier to prevent oxygen diffusion
Data Source
AI summary
Provided is a method for manufacturing a variable resistance nonvolatile semiconductor memory element, and a nonvolatile semiconductor memory element which make it possible to operate at a low voltage and high speed when initial breakdown is caused, and exhibit favorable diode element characteristics. The method for manufacturing the nonvolatile semiconductor memory element includes, after forming a top electrode of a variable resistance element and at least before forming a top electrode of an MSM diode element, oxidizing to insulate a portion of a variable resistance film in a region around an end face of a variable resistance layer.