Tiltable MEMS Mirror Wafer Bonding With Antireflective Cap Alignment
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Solution Overview
Problem
The manufacturing process of microelectromechanical devices with a tiltable structure is complex and prone to alignment issues due to the separate production and post-manufacture bonding of the protective cap, leading to potential operational defects and safety concerns from spurious reflections.
Innovation Solution
A manufacturing process that integrates the formation of a protective cap with an antireflective surface within the same factory, aligning it with the tiltable structure during wafer bonding, and using semiconductor materials for the cap to absorb or diffuse light, ensuring precise alignment and improved safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the protective cap is produced separately and bonded post-manufacture, then the manufacturing process is more flexible, but alignment precision deteriorates leading to operational defects
Solution Approach 1:
The patent merges the protective cap production with the tiltable structure manufacturing by forming both components in the same wafer using integrated semiconductor fabrication processes. This eliminates separate bonding operations and ensures precise alignment through wafer-level integration, resolving the contradiction between manufacturing flexibility and alignment precision.
Solution Approach 2:
The protective cap structure is formed preliminarily within the wafer before final device completion. By pre-forming the cap with integrated circuit features and bonding pads in the same wafer substrate, the alignment is established during fabrication rather than requiring post-manufacture bonding, thus achieving high precision while maintaining process efficiency.
2Ease of manufacture
If conventional materials are used for the protective cap, then manufacturing is simpler, but spurious reflections occur causing safety concerns
Solution Approach 1:
The patent changes the optical parameters of the protective cap by incorporating an antireflective coating with specific refractive index properties. This coating is applied during wafer fabrication and has optimized optical characteristics that minimize spurious reflections across the operational wavelength range, eliminating safety concerns while maintaining manufacturing simplicity through integrated processing.
Solution Approach 2:
The protective cap is formed as a composite structure combining the base wafer material with an antireflective coating layer. This composite material configuration provides both the mechanical protection function and the optical performance required to eliminate spurious reflections, achieving dual functionality without complicating the manufacturing process.
3Adaptability or versatility
If the protective cap is bonded separately, then device assembly is more flexible, but manufacturing complexity increases due to multiple bonding steps
Solution Approach 1:
The patent combines multiple manufacturing operations into a single integrated wafer fabrication process. The protective cap, tiltable structure, and supporting body are all formed in the same wafer using compatible semiconductor processing steps, eliminating multiple bonding operations and reducing overall manufacturing complexity while maintaining assembly flexibility through monolithic integration.
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 process enhances manufacturing efficiency, prevents alignment defects, and reduces spurious reflections, ensuring optimal optical performance and user safety in devices like augmented-reality and virtual-reality viewers.
Implementation Method 1
using semiconductor materials for the cap to absorb or diffuse light, ensuring precise alignment and improved safety
Implementation Method 2
using semiconductor materials for the cap to absorb or diffuse light
Implementation Method 3
piezoelectric actuation systems are increasingly used
Data Source
AI summary
A method for manufacturing an optical microelectromechanical device, includes forming, in a first wafer of semiconductor material having a first surface and a second surface, a suspended mirror structure, a fixed structure surrounding the suspended mirror structure, elastic supporting elements extending between the fixed structure and the suspended mirror structure, and an actuation structure coupled to the suspended mirror structure. The method continues with forming, in a second wafer, a chamber delimited by a bottom wall having a through opening, and bonding the second wafer to the first surface of the first wafer and bonding a third wafer to the second surface of the first wafer so that the chamber overlies the actuation structure, and the through opening is aligned to the suspended mirror structure, thus forming a device composite wafer. The device composite wafer is diced to form an optical microelectromechanical device.