MRAM Top Electrode Cap Structure for Oxidation Resistance
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Solution Overview
Problem
Magnetoresistive random-access memory (MRAM) cells face issues with oxidation of top electrodes due to environmental exposure, leading to increased contact resistance and reduced yield, as existing capping layers may not effectively prevent oxidation, especially when oxygen bypasses the capping layer and re-oxidizes the top electrode.
Innovation Solution
An enhanced top electrode cap structure is introduced, comprising a getter layer with a high oxygen absorption capacity, such as titanium, and an oxygen-resistant layer like titanium nitride, which cooperatively protect the top electrode from oxidation by trapping errant oxygen and resisting further oxidation, thereby reducing the risk of oxidation-related performance issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional capping layer is used to protect the top electrode, then the structure is simple, but oxidation of the top electrode occurs leading to increased contact resistance and reduced yield
Solution Approach 1:
The cap structure is divided into multiple functional layers: a diffusion barrier layer (e.g., titanium nitride) and a capping layer (e.g., silicon nitride or silicon oxide). This segmentation allows each layer to perform its specific function - the diffusion barrier prevents oxygen diffusion while the capping layer provides physical protection, together achieving superior oxidation resistance without excessive complexity
Solution Approach 2:
The invention uses composite material structures combining different materials with complementary properties. The diffusion barrier layer (titanium nitride) provides oxygen blocking properties, while the capping layer (silicon nitride/oxide) provides environmental protection. This composite approach achieves enhanced oxidation resistance that neither material could provide alone
2Ease of manufacture
If the top electrode is exposed to environment, then manufacturing is easier, but oxidation occurs increasing contact resistance
Solution Approach 1:
The diffusion barrier layer is formed on the top electrode surface before subsequent processing steps. This preliminary protective action ensures that the electrode is already protected against oxidation before it is exposed to the environment during manufacturing and operation, allowing easy accessibility while preventing harmful oxidation
3Device complexity
If oxygen is allowed to reach the top electrode, then the structure is simpler, but contact resistance increases due to oxidation
Solution Approach 1:
The diffusion barrier layer acts as an intermediary between the top electrode and oxygen. This intermediate layer (titanium nitride) specifically blocks oxygen diffusion while maintaining electrical conductivity, preventing oxidation without requiring complex multi-layer structures, thus achieving low contact resistance with moderate structural complexity
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 enhanced cap structure effectively prevents oxidation of the top electrode, maintaining low contact resistance and high yield by trapping oxygen and resisting further oxidation, thus ensuring stable operation of the MRAM cells.
Implementation Method 1
a getter layer with a high oxygen absorption capacity, such as titanium
Implementation Method 2
an oxygen-resistant layer like titanium nitride, which cooperatively protect the top electrode from oxidation by trapping errant oxygen and resisting further oxidation
Data Source
AI summary
The present application relates to a method for forming a top-electrode cap structure on a memory cell. In some embodiments, a method for forming a top-electrode cap structure on a memory cell. The method includes providing a memory cell comprising a top electrode, a bottom electrode, and a resistive memory element sandwiched between the top and bottom electrodes. An etch is performed into an interlayer dielectric (ILD) layer covering the memory cell to form a via opening exposing the top electrode of the memory cell. A getter layer is then formed to line the via opening, and further, over and abutting the top electrode of the memory cell. An oxygen-resistant layer is formed over and abutting the getter layer.