MEMS Sloped Support Hinge Grayscale Patterning
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Solution Overview
Problem
The complexity and cost of microelectromechanical system (MEMS) device fabrication are high due to the complexity of structures and the number of steps involved, necessitating a reduction in structural complexity and fabrication steps to lower costs.
Innovation Solution
The fabrication of MEMS devices with a sloped support member and a movable member spaced by a gap above a substrate, using a metallic flexible hinge with spring tips for energy recovery, and a method involving grayscale exposure patterning of sacrificial layers to form sloped hinges and spring tips, reducing the need for filled via supports and mirror voids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional fabrication methods are used to form supported structures, then the structures provide adequate support, but the fabrication process becomes complex and costly due to multiple steps including filled via supports and mirror voiding
Solution Approach 1:
The patent extracts and removes the sacrificial layer after forming the hinge structure, eliminating the need for filled via supports and mirror voids. This extraction approach simplifies the final structure by removing unnecessary supporting elements that would otherwise be required in conventional fabrication methods.
Solution Approach 2:
The patent performs preliminary actions by forming the hinge structure with temporary sacrificial support in place, then removing the sacrificial layer. This preliminary construction approach allows the hinge to be formed with proper geometry before finalizing the structure, reducing the need for subsequent complex support structures.
2Productivity
If grayscale exposure patterning is used to form sloped hinges, then the number of fabrication steps is reduced, but the manufacturing precision requirements increase
Solution Approach 1:
The patent utilizes grayscale exposure patterning which changes the exposure parameters to create varying degrees of material removal. By controlling the exposure intensity and duration, the method achieves different etch depths in a single step, forming sloped hinge structures without requiring multiple sequential patterning steps.
Solution Approach 2:
The patent replaces multiple mechanical patterning steps with a single grayscale exposure process. Instead of sequentially adding and removing material through multiple lithography and etching steps, the method uses optical energy distribution to directly create the desired three-dimensional hinge geometry in one step.
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 simplifies the fabrication process, reduces costs, and maintains the integrity of the specular polished surface in micromirror arrays by eliminating central indentations, enabling efficient and cost-effective production of MEMS devices like digital micromirror devices.
Implementation Method 1
patterning a first sacrificial layer over the substrate using a grayscale exposure pattern to provide sloped surfaces
Implementation Method 2
optionally includes spring tips for limiting and recovering energy in pivotal movement of the plate
Data Source
AI summary
A microelectromechanical (MEMS) device has a movable member supported in elevated position spaced by a sloped support structure above a substrate. The movable member may be a polished metallic plate such as a mirror of a digital micromirror device (DMD) supported by a flexible hinge above an integrated circuit wafer die region. The plate may supported centrally at a raised juncture of two upwardly oppositely directed and symmetrically converging hinge legs for pivoting about a parallel axis. The plate may also be supported at a top end of a hinge leg in cantilever fashion, for pivoting about a perpendicular axis. Optional spring tips are provided for limiting movement and recovering energy. In a described fabrication method, hinge material is deposited over a sacrificial layer that has been directly or indirectly patterned using a grayscale photoresist exposure to define sloped surfaces which provide a template for configuring the hinge and optional other components.