Dual Sacrificial Layers for MEMS Switch Contact Gap Control
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Solution Overview
Problem
Existing methods for manufacturing MEMS switches on semiconductor substrates face challenges in precisely controlling the shape and depth of sacrificial layer recesses, leading to variations in contact gap sizes, poor planarization, and carbon-based contamination, which affect the performance and lifespan of the switches.
Innovation Solution
The use of dual sacrificial layers, where a first sacrificial layer is patterned and then exposed by a second sacrificial layer to define a recess, allowing for consistent molding of the actuation member, reducing variations in contact gap sizes and minimizing contamination through precise control of the sacrificial layer materials and removal processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single sacrificial layer is used to define the contact gap, then the manufacturing process is simple, but the contact gap size varies significantly and planarization is poor
Solution Approach 1:
The single sacrificial layer is divided into two separate sacrificial layers: a first sacrificial layer that defines the contact gap size and a second sacrificial layer that provides planarization. This segmentation allows each layer to be optimized for its specific function, resolving the contradiction between manufacturing simplicity and contact gap precision.
Solution Approach 2:
The solution adds a vertical dimension to the manufacturing process by stacking two sacrificial layers at different heights. The first sacrificial layer is positioned at the substrate level to define the contact gap, while the second sacrificial layer is positioned above it to provide planarization. This dimensional approach enables simultaneous achievement of precision and ease of manufacture.
2Ease of manufacture
If a single sacrificial layer is used, then the process is straightforward, but the contact area planarization is insufficient leading to high contact resistance
Solution Approach 1:
The sacrificial structure is segmented into two functional layers: the first sacrificial layer (polysilicon) defines the contact gap geometry, while the second sacrificial layer (spin-on-glass) provides the planarization surface. This segmentation directly addresses the planarization deficiency without complicating the overall process.
Solution Approach 2:
The second sacrificial layer acts as an intermediary planarization layer between the actuation member and the contact area. It fills in the recesses created by the first sacrificial layer's recess, providing a flat surface that ensures good contact and low contact resistance.
3Ease of manufacture
If a polymer-based sacrificial layer is used, then the sacrificial layer is easy to remove, but carbon-based contaminants are left on the contact areas
Solution Approach 1:
The sacrificial layers are segmented by material type: the first sacrificial layer uses polysilicon which can be removed without leaving carbon contaminants, while the second sacrificial layer uses polymer-based spin-on-glass for ease of removal. This material segmentation allows each layer to be optimized for its removal characteristics without contamination concerns.
Solution Approach 2:
Different material qualities are applied to different locations and functions: polysilicon is used where contamination must be avoided (first sacrificial layer defining contact gap), while polymer is used where ease of removal is prioritized (second sacrificial layer for planarization). This local quality differentiation resolves the contradiction between removability and contamination.
4Manufacturing precision
If the recess in the sacrificial layer is not sufficiently planar, then the contact area formed has poor planarization, but achieving better planarization requires more complex processing
Solution Approach 1:
The planarization function is segmented from the contact gap definition function and assigned to a separate second sacrificial layer. This allows the first sacrificial layer to focus on defining the contact gap geometry while the second layer专门 handles planarization, achieving good contact area flatness without requiring complex single-layer processing.
Solution Approach 2:
The second sacrificial layer is applied preliminarily to fill and planarize the surface before the actuation member is formed. This preliminary planarization action ensures that the contact area will be properly flattened without requiring additional complex processing steps after actuation member formation.
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 results in MEMS switches with reduced variations in contact gap sizes, improved planarization, and lower contamination, leading to increased performance and extended lifespan by ensuring consistent and clean contact areas.
Implementation Method 1
a potential is applied to the actuator plate 32 which creates an electromagnetic field. The electromagnetic field exerts a force on the actuation member 14, moving it toward the substrate 12
Implementation Method 2
The actuation member 14 is formed over the sacrificial layer 34
Data Source
AI summary
The present Disclosure provides for fabrication devices and methods for manufacturing a micro-electromechanical system (MEMS) switch on a substrate. The MEMS fabrication device may have a first and second sacrificial layer that form the mold of an actuation member. The actuation member is formed over the first and second sacrificial layers to manufacture a MEMS switch from the MEMS fabrication device.