Piezoresistive Pressure Sensor Stack for Stable Strain Detection
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Solution Overview
Problem
Conventional pressure sensors with strain detecting elements on stems face reliability issues due to the formation of amorphous layers, which can affect the delayed elasticity and change the characteristics of the strain detecting elements, leading to reduced accuracy and reliability.
Innovation Solution
A low doping layer with higher electrical resistivity than polysilicon is introduced between the insulating film and the strain detecting element, reducing the influence of delayed elasticity and minimizing the amorphous layer's impact, thereby improving the reliability of the pressure sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a membrane structure with opening is used to reduce stress concentration, then manufacturing precision can be improved, but measurement precision deteriorates due to non-uniform stress distribution
Solution Approach 1:
The patent changes the geometric parameters of the membrane by adding recesses or protrusions to create a non-uniform thickness distribution. This parameter modification allows the membrane to maintain easier manufacturability while achieving more uniform stress distribution across the diaphragm surface, thereby improving measurement precision without sacrificing manufacturing ease.
2Reliability
If stress concentration is reduced in the membrane, then reliability improves, but measurement precision deteriorates due to insufficient stress for detection
Solution Approach 1:
The patent applies local quality by creating specific regions with different thickness characteristics through recesses or protrusions. These localized structural modifications concentrate the stress in specific areas where measurement occurs, ensuring sufficient stress for detection while distributing overall stress to prevent membrane rupture, thus maintaining both reliability and measurement precision.
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 implementation of a low doping layer between the insulating film and the strain detecting element enhances the reliability of the pressure sensor by reducing changes in the strain detecting element's characteristics and improving its accuracy and durability.
Implementation Method 1
a piezoresistive element, which changes its electrical resistance in dependence on the applied stress
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A pressure sensor has a stem (10) in which a pressure introduction hole into which a pressure medium is introduced and a diaphragm (13) deformable according to the pressure of the pressure medium are formed, and a strain detecting element (30) which is arranged on the diaphragm (13) via an insulating film (20) and being configured to output a detection signal according to the deformation of the diaphragm (13). The strain detecting element (30) is configured to have a portion made of polysilicon. A low doping layer (23) having a higher electrical resistivity than polysilicon and a higher crystallinity than the insulating film is arranged between the insulating film (20) and the strain detecting element (30).