MEMS Sensor Single-Crystal Silicon Film Etching Process
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Solution Overview
Problem
Current methods for manufacturing MEMS sensors, particularly those using single-crystal silicon wafers, face challenges in achieving uniform thickness of pressure-sensitive films and require additional expensive equipment, leading to increased costs and decreased efficiency.
Innovation Solution
A method involving Deep Reactive Ion Etching (DRIE) and epitaxial growth processes to form trenches and meshwork silicon films on single-crystal silicon wafers, allowing for the formation of uniform single-crystal silicon films that can be used to fabricate MEMS sensors without the need for additional apparatus like potentiostats or clip tools.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If time controlling method is used to etch single-crystal silicon wafer from bottom side via alkaline liquor, then pressure-sensitive silicon film can be formed, but thickness uniformity between inside and outside films cannot be achieved
Solution Approach 1:
The patent inverts the conventional etching approach by etching from the top surface instead of the bottom side. The single-crystal silicon wafer is etched from the top to form a through-hole and a suspended membrane structure, allowing the pressure-sensitive film to be formed on the top surface with uniform thickness controlled by the etching depth and pattern, eliminating the thickness non-uniformity problem of bottom-side etching
Solution Approach 2:
The patent applies preliminary action by first forming a sacrificial layer and then using it as a mask during the etching process. The sacrificial layer is deposited beforehand to define the etching pattern and protect specific areas, ensuring uniform thickness of the pressure-sensitive film while maintaining manufacturing efficiency through pre-planned process steps
2Manufacturing precision
If highly doped silicon film is used to control thickness of pressure-sensitive silicon film, then thickness can be controlled, but piezoresistances cannot be fabricated on the film
Solution Approach 1:
The patent segments the manufacturing process into distinct stages: first forming the pressure-sensitive film with controlled thickness through etching, then separately fabricating the piezoresistances on this film. This segmentation allows the film to have both precise thickness control and the ability to support piezoresistance fabrication, as the film structure is created independently before adding the functional piezoresistance elements
3Ease of manufacture
If electrochemical etching is used to achieve lowly doped silicon film for piezoresistances, then piezoresistances can be fabricated, but additional expensive apparatus and complex processes are required
Solution Approach 1:
The patent extracts the electrochemical etching step and replaces it with conventional photolithography and etching processes. Instead of using expensive potentiostats and specialized clip tools for electrochemical etching, the invention uses standard semiconductor manufacturing equipment to form the pressure-sensitive film and piezoresistances, thereby reducing apparatus complexity and cost while maintaining the ability to fabricate piezoresistances on lowly doped silicon film
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 method enables the production of MEMS sensors with controlled thickness and improved uniformity, reducing manufacturing costs and enhancing efficiency by eliminating the need for expensive equipment and complex processes.
Implementation Method 1
etching the single-crystal silicon wafer from the mask diagram via a Deep Reactive Ion Etching (DRIE) process
Implementation Method 2
expanding a single-crystal silicon film based on the meshwork silicon film via an epitaxial growth process
Data Source
AI summary
A method for manufacturing a MEMS sensor and a thin film thereof includes steps of etching a top surface of a single-crystal silicon wafer in combination of a deposition process, an isotropic DRIE process, a wet etching process and a back etching process in order to form a pressure-sensitive single-crystal silicon film, a cantilever beam, a mass block, a front chamber, a back chamber and trenches connecting the front and the back chambers. The single-crystal silicon film is prevented from etching so that the thickness thereof can be well controlled. The method of the present invention can be used to replace the traditional method which forms the back chamber and the pressure-sensitive single-crystal silicon film from the bottom surface of the silicon wafer.