Optical Movable Unit Rib Structure for Precise Two-Stage Etching
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Solution Overview
Problem
Existing methods for manufacturing optical devices with rib portions on movable units or elastic support portions struggle with accuracy, leading to deformation issues and difficulty in forming these features with precision.
Innovation Solution
A method involving a semiconductor substrate with a first and second semiconductor layer and an insulating layer, where the rib portion is formed using a two-stage etching process with resist layers, ensuring the rib portion is thinner than the base and allowing for precise formation, even with varying widths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a rib portion is provided to suppress deformation of the movable unit or elastic support portion, then the structural stability is improved, but the manufacturing precision deteriorates due to difficulty in forming the rib portion with accuracy
Solution Approach 1:
The etching process is segmented into two distinct stages: a first etching step that etches the first semiconductor layer to a first depth, and a second etching step that etches the first semiconductor layer to a second depth greater than the first depth. This segmentation allows precise control over the rib portion geometry by treating different depth ranges separately, resolving the contradiction between forming accurate rib portions and maintaining structural stability.
Solution Approach 2:
The first etching step is performed as a preliminary action before the second etching step. By pre-forming a partial rib structure with the first etching, the subsequent second etching can focus on refining the rib portion to the final desired depth and shape. This preliminary action enables more precise final formation while maintaining the structural benefits of the rib portion.
2Reliability
If the first semiconductor layer is made thinner to form the rib portion, then the rib portion protection is improved by suppressing protrusion, but the manufacturing complexity increases due to the need for two-stage etching
Solution Approach 1:
The patent applies local quality by making the first semiconductor layer thinner specifically in the region where the rib portion is formed, while other regions can maintain their original thickness. This localized thinning provides rib portion protection where needed without unnecessarily complicating the overall device structure or requiring complex global modifications.
Solution Approach 2:
The patent controls rib portion depth by varying the etching depth in the vertical dimension, creating a stepped depth structure where the first semiconductor layer is etched to different depths in different regions. This dimensional approach allows precise rib formation and protection without adding horizontal complexity to the manufacturing process.
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, thereby enhancing the controllability and protection of optical devices during movement and transportation.
Implementation Method 1
a first step of preparing the semiconductor substrate that includes a portion corresponding to the base, the movable unit, and the elastic support portion; a second step of forming a first resist layer in a region corresponding to the base on a surface of the first semiconductor layer which is opposite to the insulating layer after the first step; 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 after the second step; a fourth step of 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 which is opposite to the insulating layer after the third step; 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 after the fourth step
Data Source
AI summary
An optical device includes a support portion a movable unit and a pair of torsion bars disposed on both sides of the movable unit on a first axis. The movable unit includes a main body portion, a ring-shaped portion surrounding the main body portion when viewed from a predetermined direction perpendicular to the first axis, two connection portions connecting the main body portion and the ring-shaped portion to each other, and a rib portion provided to the main body portion. Each of the two connection portions includes two connection regions that are separated from each other by a space and the each of the two connection region connects the main body portion and the ring-shaped portion to each other. The rib portion includes four extending portions radially extending between a center of the main body portion and the four connection regions respectively when viewed from the predetermined direction.