Semiconductor Optical Device Electrode Adhesion
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Solution Overview
Problem
The adhesion strength between the pad electrode and the resin layer in semiconductor optical devices is weakened during the wire bonding process, leading to potential peeling off of the pad electrode, and the height difference between the resin layer and the inorganic insulating film causes electrode disconnection.
Innovation Solution
Incorporating an inorganic insulating film, such as SiN, between the pad electrode and the resin layer to enhance adhesion and eliminate the height step, while ensuring it does not overlap with the mesa stripe structure to avoid stress and maintain reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an inorganic insulating film is interposed between the pad electrode and the resin layer to enhance adhesion, then the adhesion strength is improved, but the manufacturing complexity increases due to additional patterning and etching steps
Solution Approach 1:
An inorganic insulating film is introduced as an intermediary layer between the pad electrode and the resin layer. This intermediate layer serves as an adhesion promoter, preventing peeling of the pad electrode during wire bonding while maintaining electrical insulation properties.
Solution Approach 2:
The inorganic insulating film is formed on the resin layer surface before the pad electrode is deposited. This preliminary formation of the adhesion-promoting layer ensures that when the pad electrode is subsequently formed, it has strong adhesion to the underlying structure, preventing peeling during later wire bonding operations.
2Manufacturing precision
If photoresist is used to etch the resin layer, then the resin layer can be patterned, but the photoresist becomes smaller during etching causing exposure of the inorganic insulating film and creating height steps
Solution Approach 1:
Instead of using photoresist that shrinks in the planar dimension during etching, the patent uses an inorganic insulating film that is formed to extend beyond the pattern boundaries. This film then serves as an etch mask, allowing the resin layer to be etched to the same level without creating height steps, as the mask material does not shrink during the process.
3Strength
If the inorganic insulating film extends continuously under the electrode, then adhesion is improved, but stress may accumulate if it overlaps with the mesa stripe structure
Solution Approach 1:
The inorganic insulating film is selectively positioned to extend continuously under the pad electrode for adhesion enhancement, while deliberately avoiding overlap with the mesa stripe structure. This local differentiation ensures strong adhesion where needed while preventing stress accumulation in critical optical regions.
Data Source
AI summary
A semiconductor optical device may include a semiconductor substrate; a mesa stripe structure that extends in a stripe shape in a first direction on the semiconductor substrate and includes a contact layer on a top layer; an adjacent layer on the semiconductor substrate and adjacent to the mesa stripe structure in a second direction orthogonal to the first direction; a passivation film that covers at least a part of the adjacent layer; a resin layer on the passivation film; an electrode that is electrically connected to the contact layer and extends continuously from the contact layer to the resin layer; and an inorganic insulating film that extends continuously from the resin layer to the passivation film under the electrode, is spaced apart from the mesa stripe structure, and is completely interposed between the electrode and the resin layer.