Thermal Fluid Flow Sensor Stress-Balanced Insulating Film
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Solution Overview
Problem
Existing thermal fluid flow sensors face issues with deflection due to stress imbalances caused by microprocessing of wirings, leading to reduced detection accuracy and potential film structure destruction from abnormal heating, as the insulating film coverage is compromised, especially when using silicon nitride films with high remnant stress.
Innovation Solution
The solution involves adding a film with tensile stress to the lower layer of the sensor to compensate for the lack of tensile stress in the upper layer, ensuring that the insulating films on both layers of the heating and temperature-measuring resistive members are stacked with tensile and compressive stress films to maintain a balanced stress, preventing deflection and maintaining accurate resistance values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pitch of the line width and line spacing is narrowed to improve sensitivity, then the resistance value increases, but the coverage of the insulating film is damaged causing stress imbalance and deflection
Solution Approach 1:
The patent applies composite material structure by stacking multiple insulating films with different stress characteristics (tensile and compressive stress films) to create a balanced stress system that compensates for stress imbalances caused by microprocessing of wirings
Solution Approach 2:
The patent changes the stress parameter of the insulating film structure by introducing films with opposite stress characteristics (tensile and compressive) to balance the overall stress state and prevent deflection
2Stress or pressure
If a silicon nitride film with large remnant stress is used to provide tensile stress, then the stress compensation is enhanced, but the film becomes thinner and unevenness increases causing larger stress changes
Solution Approach 1:
The patent addresses film uniformity issues by using a composite structure of multiple insulating films that collectively provide balanced stress distribution, compensating for local unevenness in individual films
Solution Approach 2:
The patent uses compressive stress films to counterbalance the tensile stress from silicon nitride films, creating a neutralized stress system that reduces the impact of film thickness variations and unevenness
3Measurement precision
If microprocessing is performed on wirings to obtain high resistance value, then sensitivity is improved, but the insulating film coverage is damaged causing deflection and resistance value changes
Solution Approach 1:
The patent applies beforehand cushioning by pre-stacking balanced tensile and compressive stress insulating films before microprocessing, so that the stress-balanced structure compensates for subsequent stress imbalances caused by wiring etching and processing
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 approach effectively reduces surface shift and resistance fluctuations, enhancing the detection accuracy and reliability of the thermal fluid flow sensor by maintaining a stable film structure and preventing abnormal heating issues.
Implementation Method 1
insulating films formed by stacking a film having tensile stress and a film having compressive stress, the insulating films being provided to an upper layer and a lower layer of the heating resistive member and the temperature-measuring resistive member
Implementation Method 2
a heating resistive member provided in a diaphragm structure
Data Source
AI summary
A thermal fluid flow sensor having a diaphragm structure body configured by an insulating film formed by stacking a film having compressive stress and a film having tensile stress on the top and bottom of a temperature-measuring resistive element and a heater resistive element which are processed by microprocessing is provided. The insulating film at a lower layer of the heater resistive element, a temperature-measuring resistive element for heater resistive element, upstream temperature-measuring resistive elements, and downstream temperature-measuring resistive elements, has films having compressive stress (a first insulating film, a third insulating film, and a fifth insulating film) and films having tensile stress (a second insulating film and a fourth insulating film) being alternately arranged, and two layers or more of the films having tensile stress are arranged.