Post-Etch Annealing of Magnetic Layers in MRAM
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Solution Overview
Problem
Conventional magnetic annealing processes prior to patterning in MRAM device manufacturing result in damage to the multilayer stack, especially at decreasing technology nodes, leading to reduced yield and performance due to etching-induced damage, which affects the magnetoresistance ratio (MR) of the patterned cells.
Innovation Solution
A method for post-etch annealing of microelectronic workpieces involving the use of an annealing system that elevates the temperature and/or exposes the patterned layers containing magnetic material to a magnetic field, adjusting properties such as crystallization and anisotropy direction, to rectify damage caused by the etching process and enhance device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional magnetic annealing is performed prior to patterning, then the magnetic layers are properly crystallized and oriented, but the etching process subsequently causes damage to the multilayer stack reducing device yield
Solution Approach 1:
The patent inverts the conventional sequence by performing the annealing process after the etching process. Instead of annealing before patterning (conventional approach), the method anneals the patterned multilayer stack, allowing the magnetic layers to be properly crystallized and oriented after the damage-causing etching step has already been completed, thereby recovering from etch-induced damage
Solution Approach 2:
The patent applies preliminary action by performing the annealing process in advance of final device completion, specifically after patterning but before subsequent processing steps. This timing allows the magnetic properties to be optimized at the appropriate stage in the manufacturing sequence, ensuring proper crystal orientation and magnetic anisotropy are established before final device assembly
2Area of moving object
If technology nodes are decreased to achieve smaller cell dimensions, then device integration density increases, but etching-induced damage dramatically reduces device yield
Solution Approach 1:
The patent applies parameter changes by modifying the thermal and magnetic parameters of the annealing process specifically for patterned structures. The method uses elevated temperatures (e.g., 200-400°C) combined with magnetic fields to alter the crystal structure and magnetic properties of the etched layers, recovering from damage while maintaining the reduced dimensions required for high-density integration
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 post-etch annealing method improves the magnetoresistance ratio and resistance area product of patterned layers, mitigating the adverse effects of etching damage and maintaining robust device performance even at smaller cell critical dimensions.
Implementation Method 1
annealing the patterned layer containing magnetic material to transition a composition of the patterned layer containing magnetic material from a substantially amorphous phase to a substantially crystalline phase
Implementation Method 2
exposing the one or more workpieces to a magnetic field
Implementation Method 3
produce a desired anisotropy direction in or at the surface of the patterned layer containing magnetic material
Data Source
AI summary
A method for performing post-etch annealing of a workpiece in an annealing system is described. In particular, the method includes disposing one or more workpieces in an annealing system, each of the one or more workpieces having a multilayer stack of thin films that has been patterned using an etching process sequence to form an electronic device characterized by a cell critical dimension (CD), wherein the multilayer stack of thin films includes at least one patterned layer containing magnetic material. Thereafter, the patterned layer containing magnetic material on the one or more workpieces is annealed in the annealing system via an anneal process condition, wherein the anneal process condition is selected to adjust a property of the patterned layer containing magnetic material.