Tilted Micromirror for Wafer-Level Packaging Reflection Control
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Solution Overview
Problem
Existing wafer-level packaging methods for MEMS and MOEMS fail to adequately protect micromirrors from mechanical loading and reflections during separation, leading to disruptions in optical applications like image projection due to unwanted reflections at the glass interfaces.
Innovation Solution
A microsystem design where the micromirror is articulated pivotably on a frame that is permanently tilted out of the chip plane, avoiding reflections by deflecting radiation away from the cover, and a wafer-level packaging method that produces deep cavities in glass covers with high optical quality to ensure hermetic encapsulation and precise positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the micromirror is positioned parallel to the chip plane for simple manufacturing, then manufacturing precision is improved, but unwanted reflections occur at the glass interfaces disrupting optical applications
Solution Approach 1:
The micromirror is deliberately positioned at an asymmetric angle (e.g., 45 degrees) relative to the chip plane, breaking the parallel alignment. This asymmetric positioning causes incident light to be reflected away from the optical path, eliminating unwanted reflections while maintaining manufacturing feasibility through standard photolithography and bonding processes.
Solution Approach 2:
The patent converts the potentially harmful reflection effect into a beneficial directional control mechanism. By positioning the micromirror at a specific angle, the reflection that would normally be a disturbance becomes a useful feature that directs light away from the glass interface, preventing interference with the optical application.
2Manufacturing precision
If the micromirror is tilted to avoid reflections, then optical quality is improved, but the structure becomes more complex and harder to manufacture
Solution Approach 1:
The micromirror tilt angle is predetermined and built into the device structure during the manufacturing process, rather than requiring post-manufacturing adjustment. The frame or mounting structure is designed with built-in geometry that automatically positions the micromirror at the correct angle, eliminating the need for complex adjustment mechanisms while ensuring optimal optical performance.
3Reliability
If deep cavities are created in glass covers for hermetic encapsulation, then protection from environmental influences is improved, but manufacturing precision and optical quality may be compromised
Solution Approach 1:
A separate cavity structure or spacer layer is introduced as an intermediary element between the glass cover and the micromirror. This intermediary component creates the necessary deep cavity for hermetic encapsulation while maintaining a flat, optically quality surface on the glass cover itself, separating the conflicting requirements of depth and optical smoothness.
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 effectively reduces unwanted reflections, ensures high optical quality, and allows for large movement amplitudes of microscanning mirrors while maintaining the microsystem's functionality and simplicity in production.
Implementation Method 1
at least one micromirror actuator for pivoting the at least one micromirror
Data Source
AI summary
The invention relates to a microsystem having at least one micromirror (1) and at least one micromirror actuator (2) for pivoting the at least one micromirror (1) about at least one axis from a relaxed resting position, comprising a frame chip and a transparent cover (3) disposed on the frame chip, wherein the frame chip has a chip frame (10), on which the at least one micromirror (1) is articulated in an elastically pivoting manner, wherein the at least one micromirror (1) is further disposed within the chip frame (10) and in a cavity (11) that is formed between the transparent cover (3) and a carrier layer. To this end, the at least one micromirror (1) is articulated on a frame (14) pivotally about the at least one axis, the frame (14) in turn being pivotally articulated on the chip frame (10), wherein the frame (14) is permanently pivoted out of a chip plane defined by the carrier layer such that the micromirror (1) in the resting position thereof is tilted about a non-pivoting angle relative to the chip plane. The invention further relates to a method for the production of such a microsystem.