Optical Device Rib Formation for Accurate Movable Structure Etching
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Solution Overview
Problem
Existing methods for manufacturing optical devices with rib portions struggle to achieve accuracy in forming these features, leading to deformation and precision issues in the movable and elastic support portions.
Innovation Solution
A method involving a semiconductor substrate with a first and second semiconductor layer and an insulating layer, where a first resist layer is used to etch the substrate, followed by a second resist layer to form the rib portion, ensuring the rib portion is thinner than the base and allowing for precise formation through two-stage etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single-stage etching method is used to form the rib portion, then the manufacturing process is simpler and faster, but the manufacturing precision and accuracy of the rib portion cannot be achieved
Solution Approach 1:
The etching process is segmented into two distinct stages: a first etching step that creates a depression with a bottom surface, and a second etching step that forms the final rib portion. This segmentation allows each step to be optimized for its specific purpose, with the first step removing bulk material and the second step precisely forming the rib structure with required thickness and shape.
Solution Approach 2:
The first etching step performs a preliminary action by creating a depression structure that defines the boundary and bottom surface for the rib portion. This preliminary structure serves as a foundation for the second etching step, enabling precise formation of the rib portion with controlled thickness without requiring the entire rib to be formed in a single complex operation.
2Strength
If the rib portion is made thicker to suppress deformation, then the structural strength is improved, but the rib portion may protrude and damage the optical function unit during movement or transportation
Solution Approach 1:
The rib portion is designed with non-uniform thickness distribution, being thicker at the base where structural strength is needed and gradually thinner toward the tip. This local quality variation allows the rib to provide maximum strength at critical locations while avoiding excessive protrusion that could damage the optical function unit during movement or transportation.
Solution Approach 2:
The thickness parameter of the rib portion is precisely controlled through the two-stage etching process, creating a thickness gradient from base to tip. This parameter change optimizes the balance between structural strength (requiring sufficient thickness) and compatibility with the optical function unit (requiring limited protrusion), achieving both requirements simultaneously.
3Shape
If the first semiconductor layer is etched completely through to form the rib portion, then the rib structure is well-defined, but the base structure loses structural integrity and strength
Solution Approach 1:
The first etching step removes the first semiconductor layer partially (to the intermediate portion) rather than completely, creating a depression that exposes the second semiconductor layer. This partial action is sufficient to define the rib boundary and bottom surface while preserving the base structure's structural integrity and strength.
Solution Approach 2:
The second semiconductor layer acts as an intermediary that forms the bottom surface of the depression and provides a stopping point for the first etching step. This intermediary layer allows precise definition of the rib portion shape and thickness while preventing complete removal of the first semiconductor layer, thereby maintaining base structure strength.
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 enables accurate formation of rib portions, suppressing deformation and protrusion, and ensuring the rib portions do not damage the optical function unit during movement or transportation, while maintaining the desired thickness for optimal performance.
Implementation Method 1
forming a first resist layer in a region corresponding to the base on a surface of the first semiconductor layer
Implementation Method 2
forming a depression in the first semiconductor layer by etching the first semiconductor layer up to an intermediate portion in a thickness direction
Implementation Method 3
forming a second resist layer in a region corresponding to the rib portion on a bottom surface of the depression, a side surface of the depression, and the surface of the first semiconductor layer
Implementation Method 4
forming the rib portion by etching the first semiconductor layer until reaching the insulating layer using the second resist layer as a mask
Data Source
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AI summary
A method for manufacturing an optical device includes: a first step of preparing a semiconductor substrate that includes a portion corresponding to a base, a movable unit, and an elastic support portion; a second step of forming a first resist layer in a region corresponding to the base on a surface of a first semiconductor layer which is opposite to an insulating layer; a third step of forming a depression in the first semiconductor layer by etching the first semiconductor layer up to an intermediate portion in a thickness direction using the first resist layer as a mask; a fourth step of forming a second resist layer in a region corresponding to a rib portion on a bottom surface of the depression, a side surface of the depression, and the surface of the first semiconductor layer which is opposite to the insulating layer; and a fifth step of forming the rib portion by etching the first semiconductor layer until reaching the insulating layer using the second resist layer as a mask.