Ridge Electrode Layout for High-Speed Optical Semiconductor Mounting
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Solution Overview
Problem
Optical semiconductor elements with junction-down mounting face challenges in achieving high-speed operation due to large electrode areas, which result in increased parasitic capacitances and hinder speed enhancement.
Innovation Solution
The optical semiconductor element features a ridge structure with electrodes formed on ridges, utilizing solder layers to reduce electrode area and parasitic capacitance, and incorporates resin films in grooves to further minimize capacitance and inductance, allowing for junction-down mounting without the need for wire bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrodes are enlarged to accommodate solder electrodes on sub-mount, then joining reliability is improved, but parasitic capacitance increases and high-speed operation is hindered
Solution Approach 1:
The patent inverts the conventional approach by forming solder electrodes directly on the ridge structure of the optical semiconductor element itself, rather than forming large solder electrodes on a separate sub-mount. This inversion allows the electrodes to be precisely positioned on the ridge where they are needed, eliminating the requirement for large electrode areas while maintaining reliable joining.
Solution Approach 2:
The patent applies local quality by concentrating the electrode structure precisely on the ridge region where the contact layer is located. The solder electrode is formed only on the ridge top surface, creating a localized, small-area electrode that reduces parasitic capacitance while maintaining effective electrical connection at the critical interface.
2Ease of manufacture
If solder electrodes are formed on sub-mount, then joining is facilitated, but fine pattern formation is difficult and electrode area increases
Solution Approach 1:
Instead of forming solder electrodes on the sub-mount as in conventional methods, the patent inverts the approach by forming solder electrodes directly on the ridge structure of the optical semiconductor element. This allows precise pattern formation on the ridge where the electrode is needed, eliminating the sub-mount intermediate step and achieving both ease of manufacture and fine pattern precision.
Solution Approach 2:
The patent merges the electrode formation process with the ridge structure fabrication. The solder electrode is formed integrally on the ridge top surface, combining the structural support function of the ridge with the electrical connection function of the electrode, eliminating the need for separate sub-mount processing.
3Reliability
If electrodes are enlarged in accordance with solder electrode, then joining area is increased, but parasitic capacitance becomes large and high-speed operation is prevented
Solution Approach 1:
The patent applies local quality by forming the solder electrode exclusively on the ridge top surface where the contact layer is located. This localized electrode placement provides sufficient joining area at the critical interface while maintaining a very small overall electrode footprint, thereby reducing parasitic capacitance and enabling high-speed operation.
Solution Approach 2:
The patent inverts the conventional electrode placement strategy by positioning the solder electrode directly on the ridge structure rather than on a sub-mount. This inversion allows the electrode area to be minimized to only where it is functionally necessary, reducing parasitic capacitance while maintaining effective joining.
Data Source
AI summary
This optical semiconductor element includes: a substrate; a first ridge formed on the substrate and having a first first-conductivity-type cladding layer, a first core layer, a first second-conductivity-type cladding layer, and a first contact layer in this order from a lower side, with first ridge grooves provided on both lateral sides of the first ridge; and a first electrode formed in contact with the first contact layer, on the first ridge, without spreading to the first ridge grooves, the first electrode including a first solder layer.