Self-Aligned Dielectric Spacers for Cross-Point MRAM Reliability
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Solution Overview
Problem
Existing magnetoresistive random access memory (MRAM) technologies face challenges in efficiently forming self-aligned dielectric spacers in cross-point arrays, which affect the reliability and performance of magnetoresistive memory devices.
Innovation Solution
A method is developed to form a cross-point magnetoresistive memory array with self-aligned dielectric spacers by forming first electrically conductive lines, selector material layers, and magnetic-tunnel-junction-level material layers, followed by patterning and deposition of dielectric spacer material layers, and etching to create a two-dimensional array of magnetic tunnel junctions surrounded by tubular dielectric spacers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional methods are used to form dielectric spacers in cross-point MRAM arrays, then the manufacturing process is simpler, but the alignment precision and reliability of the memory device deteriorate
Solution Approach 1:
The patent applies preliminary action by forming the dielectric spacer material layer conformally over the MTJ pillar structures before patterning. This preliminary deposition ensures that the spacers are already in place and properly aligned before subsequent etching and fabrication steps, thereby achieving precise alignment without requiring complex post-alignment processes.
Solution Approach 2:
The patent employs self-service through self-aligned fabrication where the dielectric spacers automatically align with the MTJ pillar structures through conformal deposition. The spacer formation process uses the MTJ pillars themselves as the alignment reference, eliminating the need for separate alignment steps and achieving high precision automatically.
2Reliability
If self-aligned dielectric spacers are formed using the disclosed method, then the reliability of MRAM devices is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent replaces mechanical alignment systems with a chemical/conformal deposition system. Instead of using mechanical positioning or photolithographic alignment methods, the dielectric spacers are formed through conformal chemical vapor deposition or atomic layer deposition, where the chemistry of the deposition process ensures uniform coverage and automatic alignment with the underlying MTJ structures.
3Stability of the object's composition
If tubular dielectric spacers are formed around MTJ pillar structures, then the stability of magnetization switching is improved, but the device structure becomes more complex
Solution Approach 1:
The patent applies the nested doll principle by forming tubular dielectric spacers that completely surround the MTJ pillar structures. The MTJ pillars are nested within the dielectric spacer tubes, creating a protected core-shell structure where the dielectric material provides stability and protection to the magnetic tunnel junction while maintaining a relatively simple overall fabrication approach.
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
This approach enhances the reliability and performance of MRAM devices by ensuring precise alignment of dielectric spacers, improving the stability and efficiency of magnetization switching in the memory cells.
Implementation Method 1
Spin-transfer torque (STT) refers to an effect in which the orientation of a magnetic layer in a magnetic tunnel junction or spin valve is modified by a spin-polarized current. When the spin-polarized current flows through a free layer of a magnetic tunnel junction or a spin valve, the electrons in the spin-polarized current can transfer at least some of their angular momentum to the free layer, thereby producing a torque on the magnetization of the free layer.
Implementation Method 2
A resistance differential of a magnetic tunnel junction between different magnetization states of the free layer can be employed to store data within the magnetoresistive random access memory (MRAM) cell depending if the magnetization of the free layer is parallel or antiparallel to the magnetization of the polarizer layer
Data Source
AI summary
Selector material layers are formed over the first electrically conductive lines, and magnetic tunnel junction material layers are formed over the selector material layers. The magnetic tunnel junction material layers are patterned into a two-dimensional array of magnetic tunnel junction (MTJ) pillar structures. A dielectric spacer material layer is deposited over the two-dimensional array of MTJ pillar structures. The dielectric spacer material layer and the selector material layers are anisotropically etched. Patterned portions of the selector material layers include a two-dimensional array of selector-containing pillar structures. Second electrically conductive lines are formed over the two-dimensional array of MTJ pillar structures.