MEMS Cavity Fabrication Using Sacrificial Fill and Aperture Release
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Solution Overview
Problem
Existing methods for forming semiconductor structures with cavities for MEMS devices are limited in their ability to efficiently create structures with precise cavity dimensions and configurations, which are crucial for optimal performance of MEMS transducers and sensors.
Innovation Solution
A method involving the formation of cavities in a first substrate, filling them with a sacrificial material, bonding a second substrate over the first, thinning the second substrate, creating apertures through the thin layer, and removing the sacrificial material through these apertures to release the thin layer and create voids for MEMS structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If existing methods are used to form semiconductor structures with cavities, then the fabrication process can be completed, but the cavity dimensions and configurations lack precision and control
Solution Approach 1:
The method applies preliminary action by filling cavities with sacrificial material before bonding substrates, which enables precise definition of cavity dimensions and configurations. The sacrificial material serves as a template that determines the final cavity geometry, allowing precise control over cavity characteristics while maintaining a manageable fabrication process through systematic sequencing of operations.
2Manufacturing precision
If cavities are formed directly without sacrificial material, then the process is simpler, but precise cavity dimensions and configurations cannot be achieved
Solution Approach 1:
The sacrificial material acts as an intermediary element that enables precise cavity formation. By introducing this temporary material during fabrication, the method achieves precise control over cavity dimensions and configurations. The sacrificial material is subsequently removed through apertures in the thinned substrate, leaving the desired cavity structure. This intermediary approach balances manufacturing precision with ease of manufacture by using a systematic, multi-step process that is well-suited to standard semiconductor fabrication equipment and techniques.
3Ease of operation
If the second substrate is not thinned, then the structure is more robust, but apertures cannot be formed to remove sacrificial material
Solution Approach 1:
The method applies segmentation by dividing the second substrate into two functional layers: a thinned layer containing apertures for sacrificial material removal, and a remaining thicker portion that maintains structural integrity. This segmentation allows the thinned region to provide the necessary ease of operation for forming apertures and accessing cavities, while the remaining substrate portion preserves the strength and robustness needed for device operation. The bonded structure between first and second substrates further distributes mechanical loads, maintaining overall structural integrity.
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 precise formation of semiconductor structures with cavities that can be used to fabricate high-performance MEMS transducers and sensors, with improved control over cavity dimensions and configurations.
Implementation Method 1
bonding a second substrate over the first major surface of the first substrate
Data Source
AI summary
Methods of forming semiconductor structures comprising one or more cavities, which may be used in the formation of microelectromechanical system (MEMS) transducers, involve forming one or more cavities in a first substrate, providing a sacrificial material within the one or more cavities, bonding a second substrate over a surface of the first substrate, forming one or more apertures through a portion of the first substrate to the sacrificial material, and removing the sacrificial material from within the one or more cavities. Structures and devices are fabricated using such methods.