MRAM Spacer Scheme Preventing Bypass Current
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Solution Overview
Problem
In resistance switching random access memory (RRAM) devices, re-sputtered electrode metal can form a metal nitride layer that bypasses the resistance switching structure, leading to significant bypass current that interferes with the RRAM cell's operation.
Innovation Solution
The re-sputtered electrode metal is either encapsulated or converted into a high resistance compound to prevent the formation of a continuous metal nitride layer, thereby reducing bypass current. This is achieved through the use of an oxide, carbide, oxycarbide, oxynitride, carbonitride, or oxycarbonitride compound that does not react with the electrode metal or reacts to form a high resistance compound.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a silicon nitride spacer is deposited over the RRAM cell, then the RRAM cell structure is formed, but the re-sputtered electrode metal reacts to form a metal nitride layer that creates significant bypass current
Solution Approach 1:
An intermediary layer comprising a compound selected from oxides, carbides, oxycarbides, oxynitrides, carbonitrides, or oxycarbonitrides is introduced between the re-sputtered electrode metal and the silicon nitride spacer. This intermediary layer prevents direct reaction between the electrode metal and nitrogen, thereby preventing metal nitride formation and the associated bypass current, while still allowing the spacer to be deposited and perform its intended function.
Solution Approach 2:
The re-sputtered electrode metal, which initially causes harm by forming conductive metal nitride pathways, is converted into a beneficial element by transforming it into a high-resistance compound through reaction with the intermediary layer. This conversion maintains the metal in place (preventing further contamination) while eliminating its harmful conductive effect by creating an insulating or semi-insulating compound.
2Device complexity
If the re-sputtered electrode metal is left exposed, then the manufacturing process is simpler, but a continuous metal nitride layer forms that bypasses the resistance switching structure
Solution Approach 1:
The intermediary layer is deposited in advance, before the silicon nitride spacer deposition, to preemptively protect the re-sputtered electrode metal from reacting with nitrogen. This preliminary protective action prevents the formation of harmful metal nitride layers while maintaining a relatively simple manufacturing process that integrates seamlessly with existing deposition sequences.
3Object-generated harmful factors
If a protective layer is formed to prevent metal nitride formation, then bypass current is reduced, but the manufacturing process becomes more complex
Solution Approach 1:
The solution changes the chemical composition parameter of the protective layer from traditional materials to compounds selected from oxides, carbides, oxycarbides, oxynitrides, carbonitrides, or oxycarbonitrides. These materials offer superior chemical inertness toward nitrogen compared to conventional protective layers, providing better protection against metal nitride formation. The deposition parameters and material selection are optimized to maintain process simplicity while achieving enhanced protective functionality.
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 approach effectively prevents significant bypass current, ensuring proper operation of the RRAM cell by maintaining a high resistance state and a low resistance state with minimal interference.
Implementation Method 1
The re-sputtered electrode metal is either encapsulated or converted into a high resistance compound
Implementation Method 2
converted into a high resistance compound... through the use of an oxide, carbide, oxycarbide, oxynitride, carbonitride, or oxycarbonitride compound that does not react with the electrode metal or reacts to form a high resistance compound
Implementation Method 3
reducing bypass current... maintaining a high resistance state and a low resistance state with minimal interference
Data Source
AI summary
An MRAM cell has a bottom electrode, a metal tunneling junction, and a top electrode. The metal tunneling junction has a side surface between the bottom electrode and the top electrode. A thin layer on the side surface includes one or more compounds of a metal found in one of the electrodes. The thin layer has a lower conductance than the MTJ. The electrode metal may have been deposited on the side during MTJ patterning and subsequently been reacted to form a compound having a lower conductance than a nitride of the electrode metal. The thin layer may include an oxide deposited over the redeposited electrode metal. The thin layer may include a compound of the electrode metal deposited over the redeposited electrode metal. A silicon nitride spacer may be formed over the thin layer without forming nitrides of the electrode metal.