Resistive Switching Metal Oxide Memory via Metal Silicide Electrode
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Solution Overview
Problem
Conventional nonvolatile memory technologies face challenges in scaling as device dimensions shrink, particularly in producing metal-deficient nickel oxide films with sub-stoichiometric compositions for resistive switching applications, which are desirable for their high resistance and low density.
Innovation Solution
The formation of nonvolatile memory elements with resistive-switching metal oxide layers is achieved by depositing a silicon-containing layer and a metal-containing layer on an integrated circuit substrate, where the metal-containing layer is oxidized to form a metal silicide layer, increasing metal deficiency in the metal oxide, resulting in highly metal-deficient, super sub-stoichiometric films with lower densities and higher resistivities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional sputtering techniques are used to form nickel oxide films, then films with sub-stoichiometric compositions (Ni0.8O to Ni0.95O) can be produced, but the film densities are high (80% or more of stoichiometric density) and resistivities are low (less than 10 ohm-cm)
Solution Approach 1:
The patent changes the composition parameter by forming super sub-stoichiometric nickel oxide films with nickel content below Ni0.8O through controlled metal deficiency. This is achieved by depositing a nickel-containing layer and then selectively removing metal during oxidation or through controlled reduction processes, resulting in films with densities less than 80% of stoichiometric nickel oxide and resistivities greater than 10 ohm-cm, which exhibit superior resistive switching characteristics
Solution Approach 2:
The patent creates a composite structure by forming a metal-deficient nickel oxide layer on top of a metal silicide layer (such as NiSi). The metal silicide layer serves as a conductive electrode and also acts as a source of metal during subsequent processing. This composite approach allows the nickel oxide to achieve super sub-stoichiometric composition while maintaining structural integrity and enabling reliable resistive switching behavior
2Productivity
If device dimensions are reduced for scaling, then higher integration density is achieved, but traditional nonvolatile memory fabrication techniques face challenges in producing sufficiently metal-deficient films
Solution Approach 1:
The patent performs preliminary action by depositing the metal-containing layer and metal silicide layer before forming the final nickel oxide film. The metal silicide layer is prepared in advance as a metal reservoir that can supply metal during subsequent oxidation or annealing processes. This preliminary preparation enables precise control of the final nickel oxide composition to achieve super sub-stoichiometric ratios even in scaled-down devices with smaller dimensions
Solution Approach 2:
The patent introduces a metal silicide layer as an intermediary between the substrate and the nickel oxide layer. This intermediary layer serves multiple functions: it provides a conductive base, acts as a metal source during processing, and enables the formation of highly metal-deficient nickel oxide. The intermediary approach allows precise composition control in scaled devices by decoupling the deposition process from the final composition achievement
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 enables the production of nonvolatile memory elements with resistive-switching metal oxides that exhibit bistable behavior, suitable for digital data storage, with improved resistance states and increased metal deficiency, addressing the limitations of traditional fabrication techniques.
Implementation Method 1
The metal-containing layer may be oxidized to form the resistive-switching metal oxide layer. Suitable oxidation techniques that may be used to form the metal oxide layer include ion implantation of oxygen ions, thermal oxidation (e.g., using rapid thermal oxidation techniques, laser-induced thermal oxidation, or furnace oxidation), and plasma oxidation.
Implementation Method 2
During thermal oxidation or during one or more separate heating operations, heat is applied that causes the metal in the metal-containing layer to react with the silicon in the silicon-containing layer. This reaction forms a metal silicide layer.
Implementation Method 3
One or more dopant materials such as phosphorous may be deposited with the metal-containing layer or may be added to the metal-containing layer (e.g., by ion implantation, electroless deposition, etc).
Data Source
AI summary
Nonvolatile memory elements are provided that have resistive switching metal oxides. The nonvolatile memory elements may be formed by depositing a metal-containing material on a silicon-containing material. The metal-containing material may be oxidized to form a resistive-switching metal oxide. The silicon in the silicon-containing material reacts with the metal in the metal-containing material when heat is applied. This forms a metal silicide lower electrode for the nonvolatile memory element. An upper electrode may be deposited on top of the metal oxide. Because the silicon in the silicon-containing layer reacts with some of the metal in the metal-containing layer, the resistive-switching metal oxide that is formed is metal deficient when compared to a stoichiometric metal oxide formed from the same metal.