MEMS Wafer Recessed Surface for Photoresist Coverage
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Solution Overview
Problem
Microelectromechanical systems (MEMS) devices face challenges in achieving a hermetic seal due to exposed corners on the wafer surface, which can occur when resist material fails to cover topographic features, leading to reduced device quality and yield.
Innovation Solution
A process involving wet etching to form sidewalls and a recessed surface on the wafer, ensuring consistent photoresist coverage over corners, including the use of a recessed surface adjacent to a trench, promotes full coverage and prevents exposure, facilitating a hermetic seal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a photoresist is deposited onto a wafer surface with extreme topography, then the photoresist coverage becomes inconsistent and corners remain exposed, but adding more photoresist material increases cost and complexity
Solution Approach 1:
The method performs preliminary action by forming the recessed surface and sidewalls through wet etching before photoresist deposition. This pre-prepared topography ensures that corners are recessed below the main wafer surface, allowing photoresist to naturally flow into and completely cover all corner regions without requiring excessive photoresist material or complex application techniques.
Solution Approach 2:
The invention changes the topographic parameters of the wafer surface by creating a recessed surface with specific depth and sidewall angles. By controlling the etching depth and sidewall geometry, the surface parameters are optimized to facilitate uniform photoresist coverage, transforming the original flat or convex topography into a concave configuration that promotes complete corner coverage.
2Adaptability or versatility
If the wafer surface maintains extreme topography with deep trenches and cavities, then device functionality is achieved, but photoresist fails to cover corners leading to poor hermetic seal quality
Solution Approach 1:
The method applies local quality by creating a recessed surface specifically at corner regions and along sidewalls through selective wet etching. This localized topographic modification ensures that photoresist completely covers these critical corner areas where hermetic sealing is most vulnerable, while maintaining the extreme topography and deep trenches in other regions necessary for device functionality.
Solution Approach 2:
The invention implements preliminary anti-action by pre-forming the recessed surface and sidewalls before photoresist deposition. This preliminary structural preparation prevents the harmful effect of exposed corners by ensuring that the topography is already optimized to guide photoresist into complete corner coverage, thereby preemptively ensuring hermetic seal quality before the sealing process begins.
3Productivity
If standard photoresist deposition is used on extreme topography, then production throughput is maintained, but exposed corners reduce device yield
Solution Approach 1:
The method performs preliminary action by forming the recessed surface and sidewalls through wet etching before photoresist deposition. This pre-prepared topography ensures that corners are recessed below the main wafer surface, allowing photoresist to naturally flow into and completely cover all corner regions without requiring excessive photoresist material or complex application techniques.
Solution Approach 2:
The invention changes the topographic parameters of the wafer surface by creating a recessed surface with specific depth and sidewall angles. By controlling the etching depth and sidewall geometry, the surface parameters are optimized to facilitate uniform photoresist coverage, transforming the original flat or convex topography into a concave configuration that promotes complete corner coverage.
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 ensures consistent photoresist coverage over MEMS devices with extreme topography, enhancing seal quality, reducing yield issues, and allowing for cost-effective, high-throughput production with thinner photoresist layers.
Implementation Method 1
a wet etching procedure is used to form the sidewalls and recessed surface
Implementation Method 2
A resist material (e.g., a photoresist material) is deposited onto the wafer surface, where the photoresist fully covers one or more of the top corners of the wafer surface
Data Source
AI summary
A device includes sidewalls formed in a wafer surface, where the sidewalls descend to a recessed surface. The recessed surface generally promotes resist coverage on the wafer surface, including corners (e.g., junctions between the wafer surface and various surface topographies, such as cavities, the recessed surface, and so forth) on the wafer. In one or more implementations, a wet etching procedure is used to form the sidewalls and recessed surface. A resist material (e.g., a photoresist material) is deposited onto the wafer surface, where the photoresist fully covers one or more of the top corners of the wafer surface. In one or more implementations, the recessed surface is positioned adjacent a trench formed in the wafer to promote resist coverage on the top surface of the wafer.