N-implant Shield for Piezo-resistor Sensor
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Solution Overview
Problem
Piezoresistive pressure sensors face sensitivity drift due to external electric fields and surface charges, which existing shielding methods fail to adequately address without increasing membrane thickness and inducing mechanical stress.
Innovation Solution
A doped shield with opposite doping type to the piezo-resistors is embedded in the flexible structure, providing electrical contact and extending beyond the piezo-resistors to reduce floating charges and maintain sensitivity without thickness increase, using implantation instead of deposition to minimize stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a shielding layer is deposited on top of the membrane, then protection against external electric fields and surface charges is improved, but mechanical stress is induced and membrane sensitivity is reduced
Solution Approach 1:
The patent changes the fundamental parameter of shield formation from physical deposition to ion implantation. This allows the shield to be created within the membrane material itself rather than as a separate layer, avoiding the mechanical stress and sensitivity loss associated with deposited shielding layers while still providing protection against external electric fields and surface charges
Solution Approach 2:
The patent replaces the mechanical deposition process with an ion implantation process. Instead of physically depositing material that creates stress, ions are implanted to create a doped region that provides electrical shielding without mechanical stress, thus preserving membrane sensitivity
2Object-affected harmful factors
If shielding material is deposited on the membrane, then protection against EM interference is improved, but membrane thickness increases and sensitivity is reduced
Solution Approach 1:
The patent embeds the shielding function within the existing membrane structure through ion implantation. The shield is nested inside the membrane material as a doped region rather than being added as an external layer, so the membrane thickness remains unchanged while still providing EM interference protection
Solution Approach 2:
The patent changes the state of the shield from being an external deposited layer to being an internal doped region created by ion implantation. This parameter change allows the shield to provide protection without increasing membrane thickness, as the shield is formed within the existing material volume
3Object-affected harmful factors
If a complex processing route with multiple steps is used, then shielding effectiveness is improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges the shield formation process with the existing ion implantation steps used for creating piezoresistors. By combining these functions into a single implantation process, the manufacturing complexity is reduced while still achieving effective shielding, eliminating the need for separate deposition and isolation steps
Solution Approach 2:
The ion implantation process is made multi-functional, serving both to create the piezoresistors and to form the shielding region. This universal approach reduces manufacturing complexity by using a single process step to achieve multiple objectives that would traditionally require separate processing steps
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 solution achieves low residual stress and output drift with maintained sensitivity, reducing the risk of device breakdown and chemical degradation, while being compatible with harsh environments.
Implementation Method 1
at least part of the sheet is implanted with dopant atoms of a second type, forming a shield... the doped first region and the doped second region form a depletion layer between each other, which shields the piezo-resistors from disturbances
Implementation Method 2
at least part of the sheet is implanted with dopant atoms of a second type, forming a shield
Data Source
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AI summary
The present invention relates to a piezo-resistor-based sensor, and a method to fabricate such sensor. The sensor comprises at least a sensing element provided on a flexible structure, such as a membrane or cantilever or the like, the sensing element comprising at least one piezo-resistor comprising at least a first region of the flexible structure doped with dopant atoms of a first type. The flexible structure furthermore comprises a second doped region within it, at least partially overlapping the first doped region, thereby forming a shield for shielding the sensing element from external electrical field interference, wherein dopant atoms of the second doped region are of a second type opposite to the type of dopant atoms of the first doped region, for generating a charge depletion layer within the flexible structure at the overlapping region between the first doped region and the second doped region.