Magnetic Multi-Turn Sensor Crossings: Lithography and Field Weakening
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Solution Overview
Problem
Existing magnetic multi-turn sensors with GMR-MT technology face challenges due to non-ideal crossing structures, which can lead to distortion and nucleation events, compromising the sensor's performance.
Innovation Solution
The techniques involve forming crossings using lithography methods to minimize distortion, modifying material thickness and magnetic properties in the crossing area, and locally weakening the applied magnetic field to prevent nucleation events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If crossings are formed with rounded corners to simplify manufacturing, then ease of manufacture is improved, but manufacturing precision deteriorates causing distortion and nucleation events
Solution Approach 1:
The crossing formation process is divided into multiple lithography steps with separate mask patterns. The first lithography step forms a first pattern, the second lithography step forms a second pattern, and their alignment creates the final cross shape. This segmentation allows each step to be optimized independently while achieving precise sharp corners in the final structure.
Solution Approach 2:
Magnetic shielding material is deposited over the crossing area before final lithography patterning. This preliminary magnetic shielding action prevents unwanted nucleation events during subsequent processing steps, ensuring that domain walls are guided correctly through the crossing without spurious nucleation that would compromise sensor performance.
2Manufacturing precision
If the crossing structure is made ideal with sharp corners to prevent distortion, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The complex cross structure is formed by combining simpler first and second patterns through multiple lithography steps. Each pattern can be generated using standard lithography tools, but their precise alignment creates the complex sharp-cornered cross shape that would be difficult to achieve in a single step. This segmentation reduces the complexity of individual manufacturing operations while achieving the desired precise geometry.
3Strength
If material thickness is increased in the crossing area to strengthen the structure, then strength is improved, but magnetic properties deteriorate affecting domain wall propagation
Solution Approach 1:
The magnetic film layer has different thicknesses in different regions. The crossing area has a first thickness optimized for structural integrity and domain wall guidance, while other areas have a second thickness optimized for magnetic properties. This local variation in thickness allows each region to be optimized for its specific function without compromising the other.
Solution Approach 2:
Magnetic shielding material is introduced as an intermediary layer over the crossing area. This shielding material mediates between the structural requirements (strength) and magnetic requirements (domain wall propagation) by providing mechanical support while maintaining controlled magnetic field distribution that prevents unwanted nucleation events.
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
These techniques enhance the performance of closed-loop magnetic multi-turn sensors by reducing distortion and preventing nucleation events, thereby improving the accuracy and reliability of angular position sensing.
Implementation Method 1
forming, over a first photoresist material layer applied to the magnetic film layer, a first mask layer having a first pattern; exposing the first photoresist material layer
Implementation Method 2
crossings are included for GMR closed loop sensor topologies to guide magnetic domain walls from the inside to the outside of turns of a spiral-shaped or concentrically-looped structure
Implementation Method 3
In a magnetic sensing device employing a giant magnetoresistance (GMR) effect, crossings are included for GMR closed loop sensor topologies
Implementation Method 4
The domain wall generator generates domain walls in response to rotations of an external magnetic field, these domain walls then being injected into the magnetic strip
Data Source
AI summary
The techniques described are applicable to closed-loop magnetic multi-turn sensors including giant magnetoresistance (GMR-MT) sensors as well as tunnel magnetoresistive (TMR) multi-turn sensors. Techniques, e.g., lithography techniques, are described to form crossings so that a distortion of an ideal shape is reduced or minimized. Another aspect describes techniques to modify the material thickness and/or magnetic properties in such an area of the crossing. Yet another aspect describes techniques to locally weaken the applied field in the area of the crossing to prevent nucleation events in this area. The techniques described are applicable to closed-loop magnetic multi-turn sensors including giant magnetoresistance (GMR-MT) sensors as well as tunnel magnetoresistive (TMR) multi-turn sensors.