Semiconductor Modulator Pad Electrode Adhesion via Dielectric Underlayer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Semiconductor optical modulators, such as Mach-Zehnder type optical modulators, face challenges with pad electrode adhesion to benzocyclobutene (BCB) resin, leading to potential separation and reduced high-speed modulation efficiency.
Innovation Solution
A method for manufacturing semiconductor modulators involves forming an underlayer structure with an insulating layer on a substrate, followed by a pad electrode, to enhance adhesion, including specific etching steps and material choices like silicon oxide or nitride films, and using a benzocyclobutene resin with silicon for improved bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the pad electrode is formed directly on the benzocyclobutene (BCB) resin to achieve high-speed modulation, then the modulation speed is improved, but the adhesion between the pad electrode and the resin deteriorates causing easy separation
Solution Approach 1:
The patent introduces an underlayer structure consisting of an insulating layer and a metal layer between the pad electrode and the BCB resin. This intermediary structure serves as an adhesion promoter, providing strong bonding to both the resin and the pad electrode, thereby preventing separation while maintaining the direct contact configuration needed for high-speed modulation.
Solution Approach 2:
The underlayer structure employs a composite configuration combining insulating material (such as silicon oxide or silicon nitride) with conductive material (metal layer). This composite approach leverages the adhesive properties of the insulating layer to the resin and the conductive properties of the metal layer to the pad electrode, resolving the adhesion problem without compromising electrical performance.
2Reliability
If the pad electrode area is increased to improve electrical contact, then the adhesion is improved, but the device area and complexity increase
Solution Approach 1:
The underlayer structure provides a localized adhesion enhancement mechanism that does not require expanding the pad electrode area. The insulating and metal layers create strong bonding interfaces within a compact footprint, maintaining small device area while achieving reliable adhesion through the intermediary structure.
3Object-generated harmful factors
If the insulating layer thickness is increased to reduce leakage current, then the leakage current is reduced, but the adhesion strength and electrical performance may deteriorate
Solution Approach 1:
The patent specifies an optimal thickness range for the insulating layer (20-200 nm) that balances leakage current reduction with adhesion maintenance. This parameter optimization ensures that the insulating layer is thick enough to provide electrical isolation and reduce leakage, yet thin enough to maintain strong adhesion to the BCB resin and allow effective bonding of the metal layer.
Data Source
AI summary
A method for manufacturing a semiconductor modulator includes the steps of preparing a substrate having a main surface including first and second areas; forming a stacked semiconductor layer on the main surface; forming an optical waveguide mesa by etching the stacked semiconductor layer using a mask, the optical waveguide mesa including an optical modulation portion; applying a resin on a top surface and a side surface of the optical waveguide mesa and on the substrate; forming a first opening in the resin on the second area of the substrate; forming an underlayer structure on the second area of the substrate in contact with the substrate; and forming a pad electrode on the underlayer structure in contact with the underlayer structure through the first opening of the resin. The underlayer structure includes an insulating layer made of a dielectric material.