Single-Package Bridge-Type Magnetic Field Sensor
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Solution Overview
Problem
Existing magnetic sensors face challenges such as excessive size, inadequate sensitivity, dynamic range, cost, and reliability, particularly in integration with semiconductor devices and mass production, due to yield issues in the MTJ process and backend packaging.
Innovation Solution
A single-package bridge-type magnetic field sensor is developed using MTJ or GMR sensor chips with a reference resistor and a sensing resistor, where the magnetoresistive elements are directly interconnected in series, and optionally biased by bar-shaped permanent magnets, facilitating easy integration into standard semiconductor packages for high-performance, low-cost mass production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If MTJ process and backend packaging are used to manufacture magnetic sensors, then sensitivity and size can be improved, but yield and manufacturing reliability deteriorate
Solution Approach 1:
The patent combines multiple magnetoresistive elements into a single integrated bridge sensor chip, merging the sensing elements, reference resistors, and interconnections into one unified structure. This integration eliminates the need for complex backend packaging and assembly processes, thereby improving yield while maintaining the high sensitivity enabled by MTJ technology.
Solution Approach 2:
The patent performs preliminary actions by pre-configuring the magnetoresistive elements, reference resistors, and interconnections directly on the sensor chip during fabrication. This preliminary integration of all components eliminates subsequent assembly steps and reduces packaging complexity, resolving the contradiction between achieving high sensitivity through MTJ and maintaining manufacturing yield.
2Measurement precision
If MTJ process is used to manufacture high sensitivity sensors, then sensitivity can be improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent merges all sensor components (magnetoresistive elements, reference resistors, interconnections) into a single integrated chip structure that can be fabricated using standard semiconductor processes. This integration simplifies manufacturing by eliminating the need for complex multi-step assembly and packaging operations, thereby reducing manufacturing complexity while maintaining high sensitivity.
Solution Approach 2:
The patent designs a universal bridge sensor structure that can be fabricated using standard semiconductor manufacturing processes, making the high-sensitivity MTJ technology compatible with existing fabrication infrastructure. This universality allows the same process to produce both the sensitive MTJ elements and the supporting circuitry, reducing overall manufacturing complexity.
3Measurement precision
If multiple magnetoresistive elements are combined to form bridge sensors, then sensitivity can be improved, but matching the magnetoresistive response becomes difficult
Solution Approach 1:
The patent applies local quality by placing reference resistors in close proximity to the magnetoresistive elements on the same chip. This local arrangement ensures that both the sensing elements and reference resistors experience identical environmental conditions and process variations, making their responses inherently matched without requiring complex post-fabrication adjustment.
Solution Approach 2:
The patent merges the magnetoresistive elements and reference resistors into a single integrated structure fabricated in the same process batch. This combination ensures that all components share the same fabrication history and environmental exposure, naturally achieving matched magnetoresistive responses while maintaining high sensitivity through the bridge configuration.
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 solution enables the manufacturing of linear high-performance magnetoresistive sensors that are cost-effective, suitable for mass production, and offers improved sensitivity and reliability by leveraging standard semiconductor fabrication processes.
Implementation Method 1
Magnetic tunnel junction (MTJ) sensors have the advantages of high sensitivity, small size, low cost, and low power consumption
Implementation Method 2
with bar-shaped permanent magnets between the magnetoresistive element columns in order to bias the magnetoresistive elements
Data Source
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AI summary
A magnetoresistive sensor bridge utilizing magnetic tunnel junctions is disclosed. The magnetoresistive sensor bridge is composed of one or more magnetic tunnel junction sensor chips to provide a half-bridge or full bridge sensor in a standard semiconductor package. The sensor chips may be arranged such that the pinned layers of the different chips are mutually antiparallel to each other in order to form a push-pull bridge structure. The sensor chips are then interconnected using wire bonding. The chips can be wire-bonded to various standard semiconductor leadframes and packaged in inexpensive standard semiconductor packages. The bridge design may be push-pull or referenced. In the referenced case, the on-chip reference resistors may be implemented without magnetic shielding.