Single-Chip Magnetic Field Sensor Bridge with Interleaved Shielding
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Solution Overview
Problem
Current single-chip magnetic field sensor bridges face challenges in achieving low offset, high sensitivity, and good linearity due to complex manufacturing processes, large chip size, and inefficient magnetic field distribution, leading to reduced dynamic range and increased cost.
Innovation Solution
A single-chip magnetic field sensor bridge design featuring a Wheatstone half- or quasi-bridge configuration with interleaved reference and sense element strings, optimized shielding structures, and CMOS substrate, which reduces chip size, improves linearity, and enhances sensitivity by maintaining high saturation fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If local laser annealing is used to flip pinned layer magnetization, then single-chip sensor bridge is achieved, but production cost increases and production speed decreases
Solution Approach 1:
The patent extracts the magnetization direction control from the manufacturing process by using magnetic shielding structures during deposition, eliminating the need for subsequent laser annealing steps. This allows standard semiconductor manufacturing processes to be used while still achieving opposite magnetization directions in adjacent bridge arms.
Solution Approach 2:
The magnetic shielding structures are deposited along with the sensor elements in the same manufacturing step, establishing the magnetization direction configuration before the actual sensing operation. This preliminary arrangement of magnetic fields during deposition eliminates the need for post-processing annealing steps.
2Object-affected harmful factors
If reference elements and sensing elements are spatially located far apart, then shielding structures can be implemented, but chip size increases and thermal compensation effectiveness decreases
Solution Approach 1:
The patent merges the reference elements and sensing elements into a closely integrated Wheatstone bridge configuration on the same chip, with both types of elements located in close proximity. This allows magnetic shielding to be effective while maintaining small chip size and ensuring both arms experience the same temperature conditions for effective thermal compensation.
3Measurement precision
If rectangular shield structures are used, then magnetic field concentration is achieved, but magnetic field distribution becomes nonuniform and hysteresis is produced
Solution Approach 1:
The patent uses semicircular shield structures that provide localized magnetic field concentration at the sensor element positions while maintaining smooth field distribution across the entire sensing region. The semicircular geometry concentrates flux where needed without creating the nonuniform distribution and hysteresis associated with rectangular shields.
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 design achieves low offset, high sensitivity, and improved temperature performance while reducing chip size and production costs, with a smaller chip size of 0.5mm x 0.5mm and a magnetic field gain factor between 1<A sns <100, ensuring effective magnetic field sensing.
Implementation Method 1
TMR (tunneling magnetoresistance) sensors are a new magnetoresistive sensing technology that is beginning to find use in industrial applications. This sensor technology uses tunneling magnetoresistive multilayer thin film materials for sensing the magnetic field
Implementation Method 2
Compared to other practical applications utilizing the AMR effect (anisotropic magnetoresistance) or the GMR effect (giant magnetoresistance)
Implementation Method 3
Compared to other practical applications utilizing the AMR effect (anisotropic magnetoresistance) or the GMR effect (giant magnetoresistance)
Implementation Method 4
Compared to the Hall Effect it has much better temperature stability
Implementation Method 5
using magnetic shielding to provide flux concentrators in referenced bridge sensors
Implementation Method 6
using magnetic shielding to provide flux concentrators in referenced bridge sensors
Implementation Method 7
deposited on said substrate a Wheatstone half-bridge or a Wheatstone quasi-bridge
Data Source
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Figure 5~6
AI summary
A single-chip magnetic field sensor bridge, comprising a substrate (1), a reference arm, a sensing arm, shielding structures (42), and wire bond pads (7, 8, 9, 10) is disclosed. The reference arm and the sense arm respectively comprise at least two rows/columns of reference element strings (44) and sense element strings (43) formed by electrically connecting one or more identical magnetoresistive sensing elements. The reference element strings (44) and the sense element strings (43) are alternately arranged. The magnetoresistive sensing elements are AMR, GMR or TMR sensing elements. The reference element strings (44) are provided with shielding structures (42) thereon, and the sensing element strings (43) are located in gaps (45) between two adjacent shielding structures (42). The shielding structures (42) are arrays of elongated strips composed of permalloy or another soft ferromagnetic material. The sensors can be implemented as one of three different bridge structures, called a quasi-bridge, a half-bridge, or a full-bridge. This single-chip magnetic field sensor bridge has the advantages of small size, low cost, high sensitivity, small offset, good linearity, and good temperature stability.