3D Dome Wafer-Level MEMS Mirror Package with Reduced Footprint
Solution Overview
Problem
Existing MEMS mirror packages for optical applications are complex, cost-intensive, and require large footprints due to the limitations of traditional package geometries, leading to issues like signal noise and reflection interference.
Innovation Solution
A 3D dome-shaped transparent cover is integrated into a wafer-level package assembly, where a transparent cover wafer is bonded to a spacer wafer, forming a dome structure over the MEMS mirror, with the center of the mirror positioned at the vertex, and the package is sealed using hermetic bonding methods like eutectic bonding or glass microwelding to minimize footprint and reduce optical interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a hemisphere-shaped transparent cover is used to minimize reflection and signal noise, then optical performance is improved, but the package footprint increases due to the required hemisphere radius
Solution Approach 1:
The patent segments the dome formation process by creating a cavity in the substrate first, then forming the transparent dome over the cavity. This segmentation allows the dome to be smaller than a full hemisphere while still achieving the optical benefits, as the cavity provides part of the volume reduction. The dome radius can be smaller than the mirror radius, reducing the footprint compared to a full hemisphere approach.
Solution Approach 2:
The patent utilizes the vertical dimension by creating a cavity that extends downward from the substrate surface. This vertical space allows the transparent dome to achieve its protective and optical functions without requiring a large horizontal footprint. The combination of vertical cavity depth and reduced dome radius achieves volume efficiency.
2Object-affected harmful factors
If a separate spacer wafer is used to create the dome structure, then optical performance is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent merges the spacer function and dome structure into a single integrated component. Instead of using a separate spacer wafer that needs to be bonded and aligned, the cavity is formed directly in the substrate and the transparent dome is formed over it, creating an integrated structure that eliminates the need for separate spacer components and reduces assembly steps.
Solution Approach 2:
The substrate serves multiple functions: it provides mechanical support, defines the cavity geometry, and serves as the base for the transparent dome. This multi-functionality eliminates the need for separate spacer components, reducing device complexity while maintaining the optical benefits of the dome structure.
3Illumination intensity
If traditional hybrid construction methods are used for packaging, then optical access is achieved, but manufacturing cost and complexity increase
Solution Approach 1:
The patent replaces complex mechanical hybrid construction with a more straightforward wafer-level processing approach. The dome is formed using thermal and pressure processes directly on the wafer, eliminating the need for complex mechanical assembly steps, precise alignments, and multiple bonding operations required by traditional hybrid construction methods.
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
The solution reduces package size, minimizes signal noise and reflection interference, and enhances processing efficiency by eliminating the need for a separate spacer wafer, thus lowering costs and improving reproducibility.
Implementation Method 1
heating the transparent cover wafer to at least a transition temperature of the transparent cover wafer at which the transparent cover wafer transitions into a viscous or rubbery state
Implementation Method 2
pressurizing the first portion of a front cavity with an overpressure; wherein heating the transparent cover wafer to a softening point of the transparent cover wafer and the overpressure causes a portion of the transparent cover wafer that is arranged over the first portion of a front cavity to bulge into a bubble
Implementation Method 3
hermetically bonding the backside of the spacer wafer to a frontside of a MEMS wafer
Data Source
AI summary
A microelectromechanical systems (MEMS) mirror package assembly includes: a MEMS wafer including a stator portion and a rotor portion that includes a MEMS mirror configured to rotate about an axis, wherein the MEMS mirror is suspended over a back cavity, wherein the MEMS wafer defines a first portion of the back cavity; a spacer wafer, wherein the backside of the spacer wafer is bonded to the frontside of the MEMS wafer, wherein the spacer wafer defines a first portion of a front cavity arranged over the MEMS mirror; a transparent cover wafer, wherein the backside of the transparent cover wafer is bonded to the frontside of the spacer wafer, wherein the transparent cover wafer includes a transparent dome structure arranged over the MEMS mirror and defining a second portion of the front cavity. The center of the MEMS mirror is arranged substantially at a vertex of the transparent dome structure.