Micro-Mirror Wafer Processing Reinforcement Structure
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Solution Overview
Problem
The manufacturing of micromechanical mirror structures with piezoelectric actuation faces challenges in reducing residual stress and preventing warping or deformations, particularly during the machining of wafers, which requires careful handling and specific chemistries to avoid damage to sensitive structures.
Innovation Solution
A method for processing wafers involves forming a reinforcement structure on the rear face and using piezoelectric actuators with a specific design to minimize deformation, along with a manufacturing process that includes epitaxial growth, planarization, and selective etching to create a monolithic semiconductor structure with mechanical reinforcement, allowing for controlled oscillation without damaging the front-facing components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If machining is performed on both front and rear faces of the wafer to form reflectors and actuators, then the functional structures are created, but residual stress accumulates causing warping and deformation of the mirror
Solution Approach 1:
The manufacturing process is segmented into distinct phases: first forming reinforcement structures on the rear face, then processing the front face. This segmentation allows independent optimization of each face's processing parameters and reduces cumulative stress effects.
Solution Approach 2:
Reinforcement structures are formed on the rear face before front face processing. This preliminary action provides mechanical support that prevents warping during subsequent front face machining operations, ensuring mirror flatness is maintained throughout the process.
2Reliability
If supporting wafers and specific chemistries are used during back face machining, then damage to front face structures is prevented, but the manufacturing process becomes more complex and time-consuming
Solution Approach 1:
The reinforcement structures are formed in advance on the rear face, creating a protective framework before front face structures are processed. This preliminary reinforcement enables more aggressive and efficient machining of the front face without compromising structure integrity.
Solution Approach 2:
Reinforcement structures are strategically placed only in specific regions on the rear face where mechanical support is most needed during processing. This localized approach provides necessary support while minimizing additional material and processing requirements.
3Manufacturing precision
If reinforcement structures are formed on the rear face before front face processing, then warping and deformation are reduced, but the manufacturing process steps increase
Solution Approach 1:
The formation of reinforcement structures on the rear face is merged with the overall wafer processing workflow, utilizing the same epitaxial growth and etching equipment. This integration allows multiple functions to be achieved in a coordinated sequence, minimizing total processing time despite additional steps.
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 effectively reduces deformation and prevents damage to the micro-mirror structures during processing, ensuring precise control over the oscillating structure's movement and maintaining structural integrity.
Implementation Method 1
with piezoelectric actuation
Implementation Method 2
epitaxial growth, planarization, and selective etching to create a monolithic semiconductor structure
Data Source
Figure 1~2
Figure 3~7
Figure 8~10
AI summary
A method of processing a wafer (100) for manufacturing an oscillating structure (30), comprising the steps of: forming torsional elastic elements (56, 58); forming a mobile element (54, 60) connected to the torsional elastic elements; processing the first side of the wafer to form a mechanical reinforcement structure (112); and processing the second side of said wafer by steps of chemical etching, deposition of metal material, and/or deposition of piezoelectric material. Processing of the first side of the wafer is carried out prior to processing of the second side of the wafer so as not to damage possible sensitive structures formed on the first side of the wafer.