XMR Sensors High Shape Anisotropy Damascene Structuring
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional etch processes for manufacturing magnetoresistive sensors with very high shape anisotropy, such as xMR sensors, often damage sidewalls and result in non-uniform behaviors, making it difficult to achieve high manufacturing yield and accurate, narrow strip widths, which are essential for applications like multi-turn sensing.
Innovation Solution
The solution involves structuring the magnetoresistive sensor elements using a damascene or lift-off process to create the performance-relevant free-layer system without direct chemical etching, followed by a conventional etch process for the remaining stack, ensuring non-flush sides and relaxed lateral dimensions, thereby avoiding chemical modification of the magnetic field-sensitive layers and achieving uniform, narrow widths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etch processes (ion beam milling) are used to create narrow xMR strip widths, then manufacturing precision improves, but productivity deteriorates due to slow processing speed
Solution Approach 1:
The patent segments the structuring process into two distinct stages: (1) a first structuring process that defines the narrow width of the free-layer system without direct chemical etching, and (2) a second structuring process using conventional etching for the remaining stack with relaxed dimensions. This segmentation allows each process to be optimized independently, resolving the contradiction between precision and productivity.
Solution Approach 2:
The patent applies preliminary action by first structuring the free-layer system to the precise narrow width using damascene or lift-off processes before applying conventional etching to the remaining stack. This preliminary structuring establishes the critical dimensions early in the process, allowing subsequent steps to proceed faster without compromising the final precision.
2Productivity
If chemical etching processes are used to structure xMR stacks, then productivity improves, but the magnetic performance deteriorates due to sidewall damage and chemical modification
Solution Approach 1:
The patent segments the stack structuring into two parts: the free-layer system is structured without direct chemical etching to preserve magnetic performance, while the remaining stack (non-magnetic layers) is structured using conventional chemical etching processes for high productivity. This segmentation isolates the chemical etching to areas where it will not damage magnetic properties.
Solution Approach 2:
The patent applies local quality by using different structuring methods for different parts of the stack: damascene or lift-off processes for the magnetic free-layer system where precision and preservation of magnetic properties are critical, and conventional chemical etching for the remaining non-magnetic stack layers where speed is more important. Each region receives the appropriate process quality.
3Reliability
If the xMR strip width is reduced to achieve high shape anisotropy, then sensor performance for multi-turn sensing improves, but manufacturing precision becomes more difficult to maintain uniformly across wafers
Solution Approach 1:
The patent applies preliminary action by first defining the narrow free-layer system width using damascene or lift-off processes that provide excellent width control and uniformity across the wafer. This preliminary dimensioning establishes the critical narrow width (e.g., 100 nm or less) with high precision before subsequent processing steps, ensuring uniform shape anisotropy across all sensors on the wafer.
Data Source
AI summary
Embodiments relate to xMR sensors having very high shape anisotropy. Embodiments also relate to novel structuring processes of xMR stacks to achieve very high shape anisotropies without chemically affecting the performance relevant magnetic field sensitive layer system while also providing comparatively uniform structure widths over a wafer, down to about 100 nm in embodiments. Embodiments can also provide xMR stacks having side walls of the performance relevant free layer system that are smooth and/or of a defined lateral geometry which is important for achieving a homogeneous magnetic behavior over the wafer.