MTJ Top Electrode Nitrified Metal Oxidation
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Solution Overview
Problem
The fabrication of magnetic tunnel junction (MTJ) devices faces challenges due to oxidation issues during processing, which narrow the process window and increase series resistance, particularly in the top contact opening stage, due to wafer topography and etch uniformity problems.
Innovation Solution
Incorporating conductive nitrified metals like tantalum nitride (TaN) or titanium nitride (TiN) in the top electrode layer and MTJ cap layer to reduce oxidation, thereby expanding the process integration and process window.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional top electrode layer and MTJ cap layer materials are used, then the fabrication process can be simplified, but oxidation occurs during processing which increases series resistance and narrows the process window
Solution Approach 1:
The patent changes the material composition parameter of the top electrode layer and MTJ cap layer by incorporating nitrified metals (TiN, TaN) alongside traditional metals (Ta, W, Cu). This compositional parameter change fundamentally alters the oxidation resistance property, enabling the layers to withstand processing conditions without excessive oxidation while maintaining electrical conductivity.
Solution Approach 2:
The patent employs composite material structures where the top electrode layer and MTJ cap layer are formed as multi-layer composites containing both nitrified metal layers and traditional metal layers. The nitrified metal component provides oxidation resistance while the traditional metal component provides conductivity, creating a composite that simultaneously addresses both requirements.
2Manufacturing precision
If pre-sputter clear process is increased to remove top oxidation layer, then oxidation removal is improved, but more loss of top layer of MTJ layers at center region occurs which reduces process margins
Solution Approach 1:
The patent converts the harmful effect of oxidation into a beneficial outcome by using nitrified metals that form stable, conductive oxide layers or resist oxidation entirely. Instead of needing aggressive removal processes that cause material loss, the nitrified metal layers either prevent oxidation or form oxides that are easier to manage, thereby eliminating the need for excessive pre-sputter clearing while preventing top layer loss.
3Adaptability or versatility
If advanced low-k film stack restrictions are applied, then device integration is improved, but pre-clean and pre-sputter process is limited further reducing MTJ process window
Solution Approach 1:
The patent changes the material parameter of the top electrode and cap layer to nitrified metals, which fundamentally alters the oxidation behavior. This parameter change decouples the process requirements, allowing advanced low-k film stack restrictions to be maintained while eliminating the need for aggressive pre-clean and pre-sputter processes, thereby preserving the MTJ process window despite integration constraints.
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 use of nitrified metals in the top electrode and cap layers reduces oxidation, enhancing the process window and improving device performance by lowering electrical resistance and increasing yield in MTJ device fabrication.
Implementation Method 1
The nitrified metal is conductive and exhibits less oxidation than traditional top electrode layer and MTJ cap layer materials
Data Source
AI summary
A magnetic tunnel junction (MTJ) device and fabrication method is disclosed. In a particular embodiment, a method of forming a magnetic tunnel junction (MTJ) device includes forming an MTJ cap layer on an MTJ structure and forming a top electrode layer over the MTJ cap layer. The top electrode layer includes a first nitrified metal.