Amorphous Conductive Cap Layers for RRAM Anode Protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional resistive random access memory (RRAM) elements face issues with anode oxidation due to environmental oxygen, leading to increased resistance or loss of conductive connection, and existing cap layers like TiN or TaN have grain boundaries that allow contaminants to penetrate, compromising their compatibility with CMOS fabrication processes.
Innovation Solution
The use of amorphous conductive cap layers with compositions like MxSeyQz or amorphous silicide, which are formed using reactive sputtering, and the incorporation of interrupting layers with different grain structures to prevent vertical alignment of grain boundaries, ensuring the cap layers remain amorphous and contamination-resistant during high-temperature anneals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cap layers (TiN or TaN) are used to prevent anode oxidation, then the anode is protected from oxidation, but grain boundaries form that allow oxygen and contaminants to penetrate through to the anode
Solution Approach 1:
The patent changes the structural parameter of the cap layer from crystalline (with grain boundaries) to amorphous (without grain boundaries). This parameter change eliminates the harmful grain boundary pathways while maintaining the protective function against oxidation, resolving the contradiction between protection and contamination prevention
Solution Approach 2:
The patent employs composite cap layer structures, such as combining amorphous materials with specific compositions (MxSeyQz where M is early transition metal, Se is semiconductor/semimetal, Q is nitrogen/oxygen) to achieve both oxidation protection and contamination blocking, eliminating the need for continuous crystalline grain boundary structures
2Object-affected harmful factors
If amorphous cap layers are used to prevent contaminant penetration, then grain boundary pathways are eliminated, but the materials must withstand high-temperature anneals of at least 400°C during CMOS fabrication
Solution Approach 1:
The patent selects amorphous materials with specific compositional parameters (MxSeyQz stoichiometry) that maintain structural stability at high temperatures. The amorphous phase itself acts as a thermal barrier that prevents crystallization and grain boundary formation even during 400°C+ annealing processes, simultaneously achieving contamination prevention and thermal stability
Solution Approach 2:
The patent uses amorphous materials that can be formed through reactive sputtering processes compatible with CMOS fabrication. These materials are designed to remain stable throughout the fabrication process, effectively 'surviving' the high-temperature anneals without degrading or forming harmful structures
3Ease of manufacture
If conventional RRAM elements are fabricated with standard anode materials, then the elements can be manufactured, but the anode oxidizes in oxygen-containing environments increasing resistance or preventing conductive connections
Solution Approach 1:
The amorphous cap layer serves as an intermediary protective barrier between the anode and the oxygen-containing environment. This intermediate layer prevents direct interaction between oxygen and the anode material, maintaining conductive connections while allowing the element to be manufactured using standard processes
Solution Approach 2:
The cap layer is applied in advance to prevent oxidation before it can occur. By establishing this protective barrier during fabrication, the anode is pre-protected against oxidation in oxygen-containing environments, ensuring reliable conductive connections are maintained throughout operation
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 proposed solution effectively prevents anode oxidation and contamination, maintaining the integrity of RRAM elements during CMOS fabrication processes, ensuring reliable conductive connections and compatibility with existing fabrication processes.
Implementation Method 1
Some conventional anode materials will oxidize when subject to an environment containing oxygen, such as air. Oxidation of an anode can increase its resistance or even prevent a conductive connection from being made to the memory element.
Implementation Method 2
The use of amorphous conductive cap layers with compositions like MxSeyQz or amorphous silicide, which are formed using reactive sputtering
Implementation Method 3
the incorporation of interrupting layers with different grain structures to prevent vertical alignment of grain boundaries, ensuring the cap layers remain amorphous and contamination-resistant
Implementation Method 4
ensuring the cap layers remain amorphous and contamination-resistant during high-temperature anneals
Implementation Method 5
Such grain boundaries can allow oxygen and/or other contaminants from an atmosphere to penetrate down to material of the anode layer
Data Source
AI summary
A memory element can include a first electrode; at least one switching layer formed over the first electrode; a second electrode layer; and at least one conductive cap layer formed over the second electrode layer having substantially no grain boundaries extending through to the second electrode layer; wherein the at least one switching layer is programmable between different impedance states by application of electric fields via that first and second electrode. Methods of forming such memory elements are also disclosed.