Magnetoresistive Stack Patterning with LELE for Dense Bit Fabrication
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Solution Overview
Problem
Existing methods for manufacturing magnetoresistive devices face challenges in achieving high feature density and precise patterning of magnetoresistive stacks, leading to potential defects and electrical shorting due to misalignment and sharp corners in the etching process.
Innovation Solution
A multi-step etching process, such as litho-etch litho-etch (LELE), is employed to pattern the magnetoresistive stack, utilizing a hardmask with different etchability profiles to minimize spacing and round sharp corners, ensuring precise formation of magnetoresistive devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single-step etching process is used to pattern the magnetoresistive stack, then the manufacturing process is simpler and faster, but the patterning precision is poor leading to misalignment and sharp corners that cause defects and electrical shorting
Solution Approach 1:
The etching process is divided into multiple sequential steps (first etching process and second etching process) with different etching conditions and selectivity ratios. The first etching process uses a first etching selectivity ratio between the first hardmask layer and the magnetoresistive stack, while the second etching process uses a second etching selectivity ratio, allowing precise control over pattern formation and corner rounding at different stages.
Solution Approach 2:
The first hardmask layer is deposited and patterned before the actual etching of the magnetoresistive stack. This preliminary patterning step establishes the initial pattern that guides subsequent etching processes, enabling precise alignment and preventing misalignment defects before they occur.
2Productivity
If the spacing between magnetoresistive devices is minimized to increase device density, then more devices can be packed in the same area, but alignment errors and sharp corners increase leading to more defects and electrical shorting
Solution Approach 1:
Different regions of the pattern are treated with different etching selectivity ratios. The first hardmask layer has a first etching selectivity ratio relative to the magnetoresistive stack, while the second hardmask layer has a second etching selectivity ratio. This local differentiation in etching behavior allows precise control over spacing and corner formation in high-density patterns, maintaining reliability even at minimal spacing.
Solution Approach 2:
The etching selectivity ratio is changed between different etching steps. The first etching process uses one selectivity ratio configuration, and the second etching process uses a different selectivity ratio configuration. This parameter change allows optimization of both spacing minimization and defect prevention at different stages of pattern formation.
3Ease of manufacture
If sharp corners are retained in the etched pattern to maintain manufacturing simplicity, then the etching process is faster, but magnetic performance deteriorates due to sharp corners affecting the magnetic fields
Solution Approach 1:
The multi-step etching process with different selectivity ratios naturally rounds the corners of the etched patterns. The first etching process creates initial patterns, and the second etching process with different selectivity further refines the corners, eliminating sharp angles and creating curved transitions that preserve magnetic performance while maintaining manufacturing feasibility.
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 enhances device density and reduces defects, improving the performance and reliability of magnetoresistive devices by minimizing spacing and eliminating sharp corners that can affect magnetic performance.
Implementation Method 1
A multi-step etching process, such as litho-etch litho-etch (LELE), is employed to pattern the magnetoresistive stack
Data Source
AI summary
A method of fabricating a magnetoresistive bit from a magnetoresistive stack includes (a) etching through at least a portion of a thickness of the surface region to create a first set of exposed areas in the form of multiple strips extending in a first direction, and (b) etching through at least a portion of a thickness of the surface region to create a second set of exposed areas in the form of multiple strips extending in a second direction. The first set of exposed areas and the second set of exposed areas may have multiple areas that overlap. The method may also include, (c) after the etching in (a) and (b), etching through at least a portion of the thickness of the magnetoresistive stack through the first set and second set of exposed areas.