Optical Semiconductor Electrode Extension for Shorter RF Signal Paths
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Solution Overview
Problem
In multi-channel optical transmitters, the long wire path between the driver IC and optical semiconductor device degrades high-frequency characteristics, and existing flip-chip mounting methods face reliability issues, making it difficult to improve high-frequency performance without adjusting termination resistance or changing the mounting structure.
Innovation Solution
An optical semiconductor device with an extended wire pattern connected to its electrodes, allowing for a shorter connection path to a high-frequency substrate without using flip-chip mounting, thereby minimizing signal reflection and improving high-frequency characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wire connection is used to connect anode electrodes and cathode electrodes to wiring board, then connection is simple, but path length becomes long and high-frequency characteristics deteriorate
Solution Approach 1:
The patent transitions from three-dimensional wire looping to two-dimensional planar electrode extension on the chip surface. By extending electrodes in the lateral direction rather than using vertical wire connections, the path length is significantly reduced while maintaining manufacturing simplicity through standard photolithography processes.
Solution Approach 2:
The patent extracts the connection function from external wires to integrated chip electrodes. The electrode patterns are directly formed on the chip substrate during fabrication, eliminating the need for separate wire bonding or lead frame connections, thereby reducing path length and improving high-frequency characteristics.
2Length of moving object
If flip-chip mounting method is used with bumps, then path length is minimized, but reliability problems occur
Solution Approach 1:
The patent segments the connection function into two parts: extended electrodes on the chip for signal connection, and separate bonding pads for mechanical attachment. This allows wire-less electrical connection without requiring flip-chip mounting, achieving short path length with improved reliability through conventional bonding methods.
3Length of moving object
If termination resistance is adjusted for each optical module, then high-frequency characteristics improve, but adjustment work time increases
Solution Approach 1:
The patent performs preliminary action by extending the electrodes during chip fabrication to achieve optimal electrical connection length. This built-in design eliminates the need for post-assembly termination resistance adjustment, reducing adjustment time while maintaining improved high-frequency characteristics through reduced inductance and capacitance.
Data Source
AI summary
An optical semiconductor device includes an optical semiconductor chip in which at least one optical element is formed in a semiconductor substrate, and an extended wire pattern that is connected to a first electrode and a second electrode of the optical element and that extends outside the optical semiconductor chip. The first electrode and the second electrode of the optical semiconductor device are formed on the front surface side of the optical semiconductor chip, and the extended wire pattern is disposed on the front surface of the optical semiconductor chip or disposed at a position apart from the front surface.