Capacitive Pressure Sensor With Ti Electrodes
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Solution Overview
Problem
MEMS pressure sensors face challenges due to significant non-linearity induced by large deflections and temperature differences, which affect the accuracy and repeatability of pressure readings across various applications.
Innovation Solution
A semiconductor device with a capacitive pressure sensor integrated on a CMOS circuit, featuring aluminum-free electrodes composed of titanium (Ti) and titanium nitride (TiN) layers, and a suspended tensile membrane, fabricated using standard CMOS techniques to reduce topography and eliminate viscoelastic issues associated with aluminum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If aluminum is used in the electrode composition, then the fabrication process is simplified, but viscoelastic issues and topography problems occur that reduce measurement precision
Solution Approach 1:
The patent changes the material composition parameter of the electrode from aluminum to titanium-based materials (Ti, TiN, TiSiN). This material substitution eliminates the viscoelastic properties that cause measurement drift and topography issues, while maintaining compatibility with standard CMOS fabrication processes. The titanium-based electrode provides dimensional stability and eliminates the harmful viscoelastic behavior of aluminum, thereby improving pressure reading accuracy without significantly complicating the fabrication process.
2Device complexity
If standard CMOS techniques are used for fabrication, then manufacturing complexity is reduced, but control over electrode composition and properties is limited
Solution Approach 1:
The patent employs composite material structures consisting of multiple titanium-based layers (Ti, TiN, TiSiN) that can be deposited using standard CMOS techniques. These composite electrode structures provide both the simplicity of standard CMOS fabrication and the precision of controlled material properties. The multi-layer titanium-based composite eliminates aluminum's viscoelastic issues while maintaining compatibility with existing manufacturing processes, achieving both low complexity and high precision.
3Adaptability or versatility
If large deflections are allowed in the membrane, then the pressure sensing range is increased, but non-linearity increases that reduces measurement precision
Solution Approach 1:
The patent changes the mechanical properties parameter of the electrode material from aluminum to titanium-based materials. Titanium and its compounds have superior mechanical properties including higher elastic modulus and better dimensional stability. These parameter changes allow the membrane to undergo larger deflections for extended pressure sensing range while maintaining linearity and reducing non-linear effects, thereby improving measurement precision across a broader pressure range.
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 enhances the accuracy and repeatability of pressure readings by reducing non-linearity and temperature-related errors, improving the sensitivity and stability of the pressure sensor over a range of temperatures and pressures.
Implementation Method 1
capacitive pressure sensor includes first and second electrodes separated from one another by a cavity
Data Source
AI summary
A capacitive sensor is disclosed. In an embodiment a semiconductor device includes a die including a capacitive pressure sensor integrated on a CMOS circuit, wherein the capacitive pressure sensor includes a first electrode and a second electrode separated from one another by a cavity, the second electrode including a suspended tensile membrane, and wherein the first electrode is composed of one or more aluminum-free layers containing Ti.