MEMS Cover Caps with Loop-Shaped Through-Holes for Cantilever Protection
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Solution Overview
Problem
Existing methods for manufacturing micro-electromechanical system (MEMS) devices using film encapsulating techniques are complex and prone to damage of cantilevers due to stress from sacrificial layers, leading to high manufacturing costs and fragility during dicing and packaging.
Innovation Solution
A method involving forming a sacrificial layer with loop-shaped through-holes on a device wafer, creating cover caps that extend into these holes to enclose the active units, and removing the sacrificial layer through device through-holes, thereby reducing stress on cantilevers and improving mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If film encapsulating techniques are used to protect cantilevers, then cantilever protection is improved, but the manufacturing process becomes complex and cantilevers may be damaged due to stress from sacrificial layers
Solution Approach 1:
The patent divides the encapsulation structure into multiple segments: a first encapsulation layer formed through deposition, and a second encapsulation layer formed through electroplating. This segmentation allows each layer to serve specific functions - the first layer provides initial protection while the second layer adds mechanical strength without requiring complex sacrificial layer processes.
Solution Approach 2:
The patent extracts and eliminates the sacrificial layer from the manufacturing process entirely. Instead of using a sacrificial layer that requires formation, encapsulation, hole creation, and removal, the invention uses a direct dual-layer encapsulation approach that simplifies the process while maintaining cantilever protection.
2Ease of manufacture
If deposition techniques are used to form encapsulation layers, then the encapsulation process is simplified, but the layers are thin and likely to collapse during dicing or packaging
Solution Approach 1:
The patent creates a composite encapsulation structure combining two different materials and formation methods: a deposition-formed first encapsulation layer and an electroplating-formed second encapsulation layer. This composite structure leverages the advantages of both methods - the simplicity of deposition and the mechanical strength of electroplating - to achieve both ease of manufacture and high mechanical strength.
Solution Approach 2:
The patent changes the formation parameters and methods of the encapsulation layers. Instead of using a single deposition process, it employs electroplating for the second layer, which allows for greater thickness and mechanical strength while maintaining processability. This parameter change from deposition-only to deposition-plus-electroplating resolves the contradiction between simplicity and strength.
Data Source
AI summary
A method for making micro-electromechanical system devices includes: (a) forming a sacrificial layer on a device wafer; (b) forming a plurality of loop-shaped through-holes in the sacrificial layer so as to form the sacrificial layer into a plurality of enclosed portions; (c) forming a plurality of cover caps on the sacrificial layer such that the cover caps respectively enclose the enclosed portions of the sacrificial layer; (d) forming a device through-hole in each of active units of the device wafer so as to form an active part suspended in each of the active units; and (e) removing the enclosed portions of the sacrificial layer through the device through-holes in the active units of the device wafer.