Flip-Chip EML Contact Layout for Heat Evacuation and High Frequency
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Solution Overview
Problem
The existing Semi-insulating Buried Heterostructure (SiBH) technology for optoelectronic devices, such as electro-absorption modulated lasers (EML), results in non-planar devices with metal contacts at different levels, leading to mechanical weakness and thermal resistivity issues due to resin encapsulation, which hampers high-frequency performance.
Innovation Solution
A one-step process for fabricating EML devices with a substrate etched to form a U-shaped groove, featuring a buried waveguide with a Distributed Feedback Grating and p-doped III-V semiconductor contact layer, where metal stripes are deposited at the same level, and H+ ions are implanted for electrical separation, eliminating the need for resin encapsulation and enhancing heat evacuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If resin encapsulation is used to avoid mechanical weakness, then mechanical strength is improved, but thermal resistivity increases and heat evacuation deteriorates
Solution Approach 1:
The invention extracts and removes the resin encapsulation layer from the device structure. By eliminating the resin layer that caused thermal resistivity, the patent achieves both mechanical strength through alternative support structures and improved heat evacuation directly to the substrate, resolving the contradiction between mechanical protection and thermal management.
Solution Approach 2:
The patent introduces metal contacts and conductive structures as intermediary elements that serve dual functions: providing mechanical support and electrical connection while simultaneously acting as thermal conduction pathways. These intermediaries replace the resin's mechanical support function while adding superior thermal management capabilities.
2Manufacturing precision
If pillars are generated for via contact to achieve metal contacts at the same level, then contact alignment is improved, but device complexity and manufacturing steps increase
Solution Approach 1:
The patent merges the contact formation process with the epitaxial growth process. Metal contacts are deposited and patterned on the same wafer face during the semiconductor fabrication sequence, eliminating the need for separate pillar formation and via etching steps. This integration achieves precise contact alignment while reducing overall device complexity and manufacturing steps.
Solution Approach 2:
The metal contacts are formed preliminarily on the wafer face before device assembly and packaging. By establishing the contact pattern early in the fabrication process on a flat surface, the patent ensures precise alignment without requiring complex post-processing steps or three-dimensional pillar structures.
3Ease of manufacture
If non-planar structure is accepted for SiBH growth, then manufacturing simplicity is maintained, but mechanical weakness and thermal management issues arise
Solution Approach 1:
The patent changes the structural parameters of the device by implementing a planar geometry with metal contacts at the same level on a flat wafer face. This parameter change maintains manufacturing simplicity through standard epitaxial growth while simultaneously improving mechanical strength and enabling better thermal management compared to non-planar structures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach suppresses mechanical weakness, reduces parasitic capacitance, and facilitates efficient heat evacuation, thereby enabling high-speed optical data transmission without thermal resistivity limitations.
Implementation Method 1
a first electrical separation (9) between the first I and second zones II consisting in a thin ribbon of implanted H+ located between the side walls and perpendicular to longitudinal axis XX
Implementation Method 2
a Distributed Feedback Grating (usually known a DFB grating) etched inside the layer of p-doped III-V semi-conductor
Implementation Method 3
an electro-absorption modulated laser (hereinafter referred to as the acronym EML) device
Data Source
Figure 1~2
Figure 3a1~3b
Figure 3c~4
AI summary
A device D composed of a laser working in a continuous wave condition (I) and an EAM (II) modulated in order to reach high frequencies without a limitation of optical power, wherein the manufacture of such a device is based on a one-step process of making a semi-insulating buried heterostructure (SIBH) where the p and n contacts 81, 82, 83) are at the same level on the same wafer face and can be easily soldered to the package of the flip-chip package FP.