Mirror Device Manufacturing: Stress Relief and Contamination Control
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Solution Overview
Problem
The existing method for manufacturing mirror devices with movable portions faces issues such as residual stress in the mirror layer leading to warping, which can change due to environmental temperature or self-heating, and potential contamination from wafer fragments during the heating process after cutting, affecting the device's quality and manufacturing efficiency.
Innovation Solution
A method involving forming structural bodies on a wafer, followed by heating to relieve residual stress, measuring warp, and then cutting the wafer to separate the parts, ensuring uniform temperature and preventing contamination, while allowing for accurate measurement and improved manufacturing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the mirror layer is formed and then the wafer is cut, then the manufacturing process can proceed sequentially, but residual stress causes the mirror layer to warp and the quality varies
Solution Approach 1:
The patent applies preliminary action by performing the heating process to relieve residual stress BEFORE the dicing step. The mirror device is heated to a predetermined temperature or higher to flatten the mirror layer before the wafer is cut into individual devices. This sequence ensures that the mirror layer is flattened while the structural body maintains its integrity during heating, preventing quality variations that would occur if heating were performed after dicing.
2Productivity
If the wafer is cut before heating, then individual devices can be processed separately, but temperature uniformity during heating cannot be achieved and manufacturing efficiency decreases
Solution Approach 1:
The patent merges multiple mirror devices into a single wafer structure and processes them together during the heating step. By keeping multiple devices connected on the wafer during heating, temperature uniformity is achieved across all devices simultaneously. The dicing step is performed after heating, allowing batch processing that improves manufacturing efficiency while maintaining temperature uniformity.
3Ease of manufacture
If the wafer is cut before heating, then individual devices are separated early, but wafer fragments can adhere to the mirror layer and contaminate it
Solution Approach 1:
The patent performs the heating process before dicing to prevent contamination. By heating the entire wafer while devices are still connected, wafer fragments generated during dicing cannot adhere to the mirror layer. The mirror layer is protected from contamination by ensuring that the potentially contaminating dicing operation occurs after the heating and flattening process is complete.
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 method effectively relieves residual stress in the mirror layer, stabilizes the mirror device's shape, and enhances manufacturing efficiency by ensuring uniform temperature and preventing contamination, resulting in a higher-quality mirror device with reduced variations.
Implementation Method 1
a heating step of heating the part of each of the plurality of parts, corresponding to the movable portion, after the first forming step and the second forming step
Implementation Method 2
the residual stress present in the mirror layer to be relieved and the change in the amount of warp of the mirror layer to be suppressed during use of the mirror device
Data Source
AI summary
A method for manufacturing a mirror device is a method for manufacturing a mirror device including a structural body that includes a support portion, a movable portion, and a coupling portion, and a mirror layer provided on the movable portion. The method for manufacturing a mirror device includes: a first forming step of forming a plurality of parts on a wafer, each of the plurality of parts corresponding to the structural body; a second forming step of forming the mirror layer on a part of each of the plurality of parts, the part corresponding to the movable portion; a heating step of heating the part of each of the plurality of parts, corresponding to the movable portion, after the first forming step and the second forming step; and a cutting step of cutting the wafer to separate the plurality of parts from one another, after the heating step.