MEMS Cavity Etching via Two-Stage Process
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Solution Overview
Problem
Existing methods for forming micro-electro-mechanical system (MEMS) devices are inadequate in fully removing by-products during the etching process, leading to performance issues due to residual unwanted materials and voids in the structures.
Innovation Solution
A two-stage etching process is employed, with a first stage having constant etching time and gas flow rate, transitioning to a second stage with increased etching time and gas flow rate, ensuring complete removal of by-products and improving etching quality, along with a dry plasma cleaning process to prevent solvent residue and maintain vacuum conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single-stage etching process is used, then the fabrication time is shorter, but by-products are not fully removed leading to performance issues
Solution Approach 1:
The etching process is divided into two distinct stages: a first stage with initial etching parameters and a second stage with modified parameters (increased etching time and gas flow rate). This segmentation allows thorough removal of by-products in the second stage while maintaining overall process efficiency, resolving the contradiction between etching quality and fabrication time.
Solution Approach 2:
The etching process employs periodic action through multiple etching cycles, where each cycle includes alternating periods of etching and cleaning. This periodic approach ensures complete removal of by-products accumulated during etching, improving etching quality without requiring a single excessively long continuous etching step.
2Manufacturing precision
If increased etching time and gas flow rate are used, then by-products are completely removed, but the process complexity increases
Solution Approach 1:
The patent applies parameter changes by systematically modifying etching time and gas flow rate between the first and second stages. The second stage uses increased etching time and gas flow rate specifically targeted at removing by-products, achieving complete by-product removal through controlled parameter adjustments rather than complex process additions.
3Ease of manufacture
If wet cleaning process is used to remove photoresist, then photoresist is effectively removed, but solvent residue contaminates the cavity
Solution Approach 1:
The patent replaces the wet cleaning process with a dry plasma cleaning process. This substitution eliminates the use of liquid solvents that would contaminate the vacuum cavity, while still achieving effective photoresist removal through plasma chemistry, thereby removing the harmful solvent residue factor.
Solution Approach 2:
The dry plasma cleaning process operates in a vacuum environment, creating an inert atmosphere that prevents solvent contamination of the cavity. This inert environment allows effective photoresist removal without introducing harmful solvent residues that would occur with wet cleaning methods.
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 enhances the performance of MEMS devices by ensuring thorough removal of by-products, reducing voids, and maintaining vacuum conditions, thereby improving structural integrity and reducing fabrication costs and time.
Implementation Method 1
The second substrate is etched to by an etching process to form a hole through the second substrate, and the hole is connected to the cavity
Implementation Method 2
a dry plasma cleaning process to prevent solvent residue and maintain vacuum conditions
Data Source
AI summary
A method for forming a micro-electro-mechanical system (MEMS) device structure is provided. The method includes forming a second substrate over a first substrate, and a cavity is formed between the first substrate and the second substrate. The method includes forming a hole through the second substrate using an etching process, and the hole is connected to the cavity. The etching process includes a plurality of etching cycles, and each of the etching cycles includes an etching step, and the etching step has a first stage and a second stage. The etching time of each of the etching steps during the second stage is gradually increased as the number of etching cycles is increased.