Semiconductor Optical Device Resin Layering for Parasitic Capacitance Reduction
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Solution Overview
Problem
The existing semiconductor Mach-Zehnder modulators face challenges in reducing parasitic capacitance due to the formation of capacitors between metal interconnections and semiconductor conductive layers, which affects frequency characteristics, and the use of thick resin layers to mitigate this issue leads to ununiformity in electrode formation and increased parasitic capacitance on side surfaces.
Innovation Solution
A method involving the formation of a first and second resin layer on a semiconductor optical device, with a groove etched to expose the top surface of the first electrode, allowing for the placement of second and third electrodes on the side surface and top surface, respectively, while maintaining a large distance between the metal interconnection and the optical waveguide to minimize parasitic capacitance, and using an insulating layer to enhance adhesion between the resin and electrode layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a thick resin layer is disposed between the metal interconnection and the optical waveguide to reduce parasitic capacitance, then the parasitic capacitance between metal interconnection and optical waveguide is reduced, but the uniformity of electrode formation deteriorates and parasitic capacitance due to side surface electrodes is increased
Solution Approach 1:
The resin layer is divided into two distinct layers: a first resin layer covering the optical waveguide and a second resin layer covering the first resin layer. This segmentation allows each layer to serve a specific function - the first layer provides base coverage while the second layer provides the necessary thickness for capacitance reduction without compromising electrode formation uniformity.
Solution Approach 2:
Instead of increasing the thickness of a single resin layer, the solution adds a vertical dimension by stacking another resin layer on top. This transforms a one-dimensional thickness problem into a two-dimensional layered structure, achieving the desired separation distance while maintaining manufacturing precision through controlled deposition of each layer.
2Length of stationary object
If a thick resin layer is used to maintain distance between metal interconnection and optical waveguide, then parasitic capacitance is reduced, but the depth uniformity of openings for electrode formation deteriorates
Solution Approach 1:
The single thick resin layer is segmented into two thinner layers with distinct functions. The first resin layer is thin enough to allow uniform opening formation, while the second resin layer provides the additional thickness needed for capacitance reduction. This segmentation resolves the contradiction between depth uniformity and separation distance.
Solution Approach 2:
The first resin layer is formed first as a preliminary step, providing a uniform base surface. Subsequently, the second resin layer is formed on top, adding the necessary thickness. This preliminary action ensures that openings can be formed uniformly in the first layer before the second layer is added, maintaining depth uniformity while achieving the required total thickness.
3Device complexity
If the metal interconnection is positioned close to the optical waveguide, then device compactness is improved, but parasitic capacitance increases and frequency characteristics deteriorate
Solution Approach 1:
The dual resin layer structure acts as an intermediary between the metal interconnection and the optical waveguide. This intermediary layer provides the necessary separation distance to reduce parasitic capacitance while maintaining a compact device structure. The resin layers mediate the spatial relationship between the conductive elements, enabling both compactness and electrical isolation.
Data Source
AI summary
A method for producing a semiconductor optical device includes the steps of forming first and second optical waveguides; forming a first resin layer on the first and the second optical waveguides; forming an opening in the first resin layer; forming a first electrode in the opening; forming a second resin layer on the first electrode and the first resin layer; forming a groove in the second resin layer on the first electrode; forming a second electrode on the second resin layer, a side surface of the groove, and the top surface of the first electrode; and forming a third electrode on the second electrode. The second and third electrodes have a region in which the second and third electrodes pass over the second optical waveguide, and, in the region, the first and second resin layers are disposed between the second electrode and the second optical waveguide.