CMOS Gas Sensor Platinum Electrodes Tungsten Heater
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Solution Overview
Problem
Existing gas sensors with metal oxide sensing materials face issues with signal stability due to electrode material drift and thermal insulation challenges, particularly at high temperatures.
Innovation Solution
A gas sensor design incorporating a silicon substrate with integrated CMOS circuitry, platinum electrodes, and a tungsten heater, along with a heat spreading structure, to maintain high signal stability and temperature homogeneity, utilizing a manufacturing process that includes Damascene and sputtering techniques for precise structure formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tungsten or aluminum electrodes are used, then manufacturing cost is reduced, but signal stability deteriorates due to electrode drift
Solution Approach 1:
The patent changes the material parameter of the electrodes from conventional materials (tungsten, aluminum) to platinum, which has superior chemical inertness and stability at high temperatures. This material substitution resolves the contradiction by prioritizing signal stability over manufacturing cost, as platinum electrodes do not drift and maintain reliable measurements throughout the sensor's operational lifetime.
2Power
If heater cross section is increased, then heating power is improved, but device size and voltage requirements increase
Solution Approach 1:
The patent changes the material parameter of the heater from conventional materials to tungsten, which has exceptionally high electrical conductivity and melting point. This enables the heater to generate sufficient heating power (300-600°C) through a small cross-sectional area, resolving the contradiction by achieving high power density without increasing device size or voltage requirements.
3Loss of energy
If membrane thickness is reduced for better thermal insulation, then thermal insulation is improved, but mechanical strength deteriorates
Solution Approach 1:
The patent employs a composite membrane structure combining multiple materials with different properties. The membrane includes thermally insulating layers (such as silicon dioxide or silicon nitride) combined with mechanically strengthening layers, creating a composite structure that simultaneously achieves excellent thermal insulation and sufficient mechanical strength to support the sensing material and withstand operational stresses.
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 provides a highly stable gas sensor with reduced drift and improved temperature uniformity, enabling reliable operation at high temperatures and low voltage, suitable for mobile applications.
Implementation Method 1
a heater of a material that comprises at least 90% of tungsten is arranged in or on the membrane at the location of the patch of sensing material
Implementation Method 2
electrodes are arranged on the membrane and are in electrical contact with the patch of sensing material in order to measure a signal indicative of the sensing material's electrical conductivity
Data Source
Figure 1~3
Figure 4~7
AI summary
A CMOS gas sensor comprises a membrane (13) extending over an opening (12) of a silicon substrate (1). A patch (2) of sensing material is arranged on the membrane (13) and in contact with electrodes (3) of platinum. A heater (5) of tungsten is located in or on the membrane (13) at the location of the patch (2) of metal-oxide sensing material. Combining platinum electrodes (3) with a tungsten heater (5) on top of a CMOS structure provides a gas sensor of high reliability and stability.