Optical Semiconductor Structure for Stress and Eddy Current Reduction
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Solution Overview
Problem
Existing semiconductor optical modulators face issues with stress generation and eddy current loss due to differences in thermal expansion coefficients between resin bodies and metal wirings, leading to reduced reliability and impaired electro-optical response characteristics.
Innovation Solution
The optical semiconductor device incorporates a design with separated protruding portions and acute-angled protective film coverage, reducing stress and eddy current loss by minimizing the exposed area of the resin body and wiring, and using benzocyclobutene for the resin body to facilitate easier formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the protective film is formed at high temperatures, then the protective film can be properly formed, but stress is generated due to difference in linear expansion coefficients between resin body and metal wiring
Solution Approach 1:
The protective film is divided into multiple segments: a first protective film formed at high temperature covering the wiring, and a second protective film formed at lower temperature covering the resin body. This segmentation allows each film to be formed under optimal temperature conditions, preventing stress generation from thermal expansion differences between materials.
Solution Approach 2:
The formation temperature parameter is changed between different protective films. The first protective film is formed at high temperature suitable for metal wiring adhesion, while the second protective film is formed at lower temperature suitable for resin body compatibility. This parameter change resolves the conflict between proper film formation and stress prevention.
2Area of stationary object
If the wiring is positioned close to the protruding portions, then the device size is reduced, but eddy current loss increases
Solution Approach 1:
The protruding portions extend in the thickness direction (vertical dimension) rather than only in the planar direction. This dimensional change allows the wiring to be positioned horizontally close to the protruding portions for compact size, while the vertical separation and acute angle configuration reduce eddy current loss by minimizing parallel current paths.
3Reliability
If the protective film covers both the top surface and side surface, then complete protection is achieved, but stress concentration occurs at right angles
Solution Approach 1:
The corner portions of the protective film are designed with curved surfaces instead of right angles. This curvature eliminates stress concentration points that would occur at sharp corners, allowing the protective film to cover both top and side surfaces completely while distributing stress evenly throughout the structure.
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 design effectively decreases stress and eddy current loss, enhancing the reliability and electro-optical response characteristics of the semiconductor device.
Implementation Method 1
utilizing benzocyclobutene for the resin body's thermosetting property
Data Source
AI summary
An optical semiconductor device includes: an element portion provided on a principal surface of a substrate; first protruding portions provided on the principal surface; a resin body including a top surface and embedding the element portion and the first protruding portions; a wiring provided on the top surface; and a protective film covering the top surface and the wiring. The element portion includes a mesa protruding portion including a first semiconductor layer, and a mesa waveguide. The first protruding portions are separated from each other and each includes the first semiconductor layer. The wiring is provided between the first protruding portions and the element portion and includes a side surface adjacent to the first protruding portions. An angle formed by a first portion covering the side surface of the wiring and a second portion covering the top surface and connected to the first portion is acute.