Pressure Sensor Bridge Layout for Stable Piezoresistor Stress
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Solution Overview
Problem
Existing pressure detection elements face challenges in achieving accurate pressure detection due to stress distribution changes in the semiconductor substrate, which affect the output characteristics of the pressure detection signal, and stress balance films alone are insufficient in mitigating these impacts.
Innovation Solution
The pressure detection element incorporates a semiconductor substrate with a diaphragm and frame, featuring a bridge circuit with strategically positioned piezoresistors, first metal interconnects, and diffusion interconnects, where the first metal interconnects are placed outside a specific radius from the piezoresistors, and the diffusion interconnects are designed to reduce electrical resistance and stabilize stress distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If metal interconnects are placed close to piezoresistors to reduce resistance, then electrical connection efficiency improves, but stress distribution stability deteriorates
Solution Approach 1:
A diffusion interconnect layer is introduced as an intermediary between the metal interconnect and the piezoresistor. This diffusion layer acts as a stress buffer that isolates the piezoresistor from stress induced by the metal interconnect, allowing the metal interconnect to be placed closer to the piezoresistor while maintaining stress distribution stability.
Solution Approach 2:
The patent optimizes the radius parameter of the exclusion zone around each piezoresistor where metal interconnects are not permitted. By carefully controlling this radius parameter, the patent achieves a balance between minimizing interconnect resistance (by allowing metal interconnects to be as close as possible) and maintaining stress distribution stability (by keeping metal interconnects sufficiently far away).
2Measurement precision
If stress balance film is added to mitigate stress changes, then temperature compensation improves, but device complexity increases
Solution Approach 1:
The patent extracts the stress compensation function from a separate stress balance film layer and integrates it directly into the diffusion interconnect layer itself. The diffusion layer is designed to inherently provide stress compensation through its material properties and geometric configuration, eliminating the need for an additional dedicated stress balance film.
Solution Approach 2:
The diffusion interconnect layer is designed to serve multiple functions simultaneously: it provides electrical connection between the piezoresistor and metal interconnect, and it also provides stress compensation to mitigate temperature-induced stress changes. This multi-functional design eliminates the need for separate stress balance films.
3Stability of the object's composition
If diffusion interconnect is used between metal interconnect and piezoresistor, then stress distribution stability improves, but manufacturing complexity increases
Solution Approach 1:
The patent merges the diffusion interconnect formation process with the existing metal interconnect fabrication process. The diffusion layer is formed using the same diffusion furnace and photolithography steps already required for creating the metal interconnect pattern, thereby integrating multiple functions into a single manufacturing flow without adding significant process complexity.
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 configuration enhances pressure detection accuracy by stabilizing stress distribution and reducing interconnect resistance, leading to improved signal transmission and measurement precision.
Implementation Method 1
a pressure detection element configured to detect a pressure from a fluid based on a change in electrical resistance in a piezoresistor provided in a diaphragm of a semiconductor substrate
Data Source
AI summary
A pressure detection element includes a semiconductor substrate that includes a diaphragm and a frame enclosing the diaphragm in a plan view; and a bridge circuit that includes a plurality of piezoresistors disposed over the diaphragm, a first metal interconnect configured to electrically connect adjacent piezoresistors of the piezoresistors, and a diffusion interconnect disposed between each of the piezoresistors and the first metal interconnect. The first metal interconnect is disposed in a remaining region excluding a first region in the semiconductor substrate. The first region is a region of a plurality of imaginary circles having a radius of a length that is 0.5 L1 or more and less than L1 from a center of each of the piezoresistors, where L1 denotes a shortest distance between each of the piezoresistors and an outer periphery of the frame in the plan view.