T-Shaped MRAM Bottom Electrode for Etchless Sub-60 Nm MTJ Isolation
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Solution Overview
Problem
Existing MRAM device fabrication methods cause chemical damage and conductive material re-deposition on MTJ sidewalls due to reactive ion etching, leading to performance issues in sub-60 nm devices.
Innovation Solution
A method involving high angle ion beam etching is used to create a T-shaped bottom electrode, allowing MTJ patterns to be formed without plasma etching, thereby avoiding chemical damage and conductive metal re-deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If reactive ion etching (RIE) is used to pattern MTJ cells, then precise patterning and separation of MTJ cells is achieved, but chemical damage and conductive material re-deposition on MTJ sidewalls occurs, lowering device performance
Solution Approach 1:
The patent extracts and removes the harmful chemical etching process from the fabrication sequence. By using physical vapor deposition (PVD) to form the bottom electrode pattern instead of chemical etching, the source of sidewall damage is eliminated while maintaining patterning capability through a different physical mechanism.
Solution Approach 2:
The patent replaces the chemical-mechanical RIE process with a purely physical PVD-based approach. The bottom electrode is patterned through physical deposition and selective removal methods, substituting chemical reactions with physical processes that do not cause sidewall damage or re-deposition.
2Object-affected harmful factors
If ion beam etching (IBE) is used to avoid chemical damage, then sidewall damage is reduced, but conductive materials are re-deposited into the tunnel barrier, resulting in shorted devices
Solution Approach 1:
The patent extracts the problematic IBE step from the process flow. Instead of using IBE to pattern the bottom electrode, the invention uses PVD deposition combined with selective removal, eliminating the re-deposition mechanism entirely while achieving the same patterning objective.
Solution Approach 2:
The patent substitutes the ion beam physical etching process with a physical vapor deposition process. By forming the bottom electrode pattern through controlled PVD deposition and selective removal, the method avoids both chemical damage and re-deposition issues inherent in IBE.
3Length of moving object
If conventional etching processes are used to form sub-60 nm MTJ structures, then device miniaturization is achieved, but manufacturing complexity and process steps increase
Solution Approach 1:
The patent merges the bottom electrode formation and patterning steps into a single PVD-based process sequence. By combining deposition, patterning, and electrode formation into an integrated workflow without requiring separate etching steps, the method reduces overall process complexity while achieving sub-60 nm dimensions.
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 method enables the formation of electrically isolated MTJ patterns on a T-shaped bottom electrode, improving MRAM device performance by preventing sidewall damage and re-deposition, suitable for sub-60 nm devices.
Implementation Method 1
pure physical etching techniques such as ion beam etching (IBE) have been applied to etch the MTJ stack
Implementation Method 2
conductive materials in the MTJ and bottom electrode can be re-deposited into the tunnel barrier
Data Source
AI summary
A first conductive layer is patterned and trimmed to form a sub 30 nm conductive via on a first bottom electrode. The conductive via is encapsulated with a first dielectric layer and planarized to expose a top surface of the conductive via. A second conductive layer is deposited over the first dielectric layer and the conductive via. The second conductive layer is patterned to form a sub 60 nm second conductive layer wherein the conductive via and second conductive layer together form a T-shaped second bottom electrode. MTJ stacks are deposited on the T-shaped second bottom electrode and on the first bottom electrode wherein the MTJ stacks are discontinuous. A second dielectric layer is deposited over the MTJ stacks and planarized to expose a top surface of the MTJ stack on the T-shaped second bottom electrode. A top electrode contacts the MTJ stack on the T-shaped second bottom electrode plug.