VCSEL Array Electrode Layout for High-Bias Isolation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing matrix addressable VCSEL arrays face reliability issues due to the overlap of metal layers and significant substrate thickness, which leads to current leakage and difficulty in isolating cathode traces, especially when high bias voltages are applied.
Innovation Solution
The VCSEL array design separates the first metal layer from the second metal layer, with the first metal layer being formed on an opposite side of the epitaxial region, reducing the distance between the metal layer and the bottom mirrors, allowing for non-overlapping metal layers and improved isolation using wafer bonding or deep etching techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal layers are overlapped in conventional VCSEL array design, then device integration is achieved, but current leakage occurs and reliability deteriorates under high bias voltages
Solution Approach 1:
The patent transitions from a planar overlapping metal layer configuration to a three-dimensional stacked configuration where metal layers are separated vertically by the epitaxial region. This dimensional reorganization eliminates the harmful overlap while maintaining electrical connectivity through controlled vias, thereby preventing current leakage and improving reliability under high bias conditions.
Solution Approach 2:
The patent divides the metal interconnect structure into separate, non-overlapping layers that are spatially segmented through the epitaxial region. This segmentation isolates the metal traces to prevent direct contact and current leakage, while still achieving the necessary electrical connections through controlled access points, thus resolving the reliability issue.
2Temperature
If substrate thickness is reduced to improve heat dissipation, then thermal management improves, but mechanical strength and isolation capability deteriorate
Solution Approach 1:
The patent employs a composite structure where a thin substrate is reinforced with embedded support elements or a strengthened substrate layer. This composite approach allows the substrate to remain thin for effective heat dissipation while the reinforcing elements provide the necessary mechanical strength and isolation capability, resolving the contradiction between thermal management and structural integrity.
3Reliability
If deep vias or wide trenches are used to isolate cathode traces, then isolation effectiveness improves, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent extracts the isolation function from complex deep via or wide trench structures and implements it through the natural separation provided by the epitaxial region itself. By utilizing the epitaxial growth process to create inherently isolated metal layer configurations, the patent achieves effective cathode trace isolation without requiring additional complex isolation structures, thereby reducing device complexity and manufacturing difficulty.
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 design enhances the reliability of the VCSEL array by reducing current leakage and improving the isolation of metal traces, enabling efficient operation with high bias voltages without the need for deep vias or wide trenches.
Implementation Method 1
A vertical-emitting device, such as a bottom-emitting or top-emitting VCSEL, is a laser in which a laser beam is emitted in a direction perpendicular to a surface of a substrate
Implementation Method 2
The epitaxial region may include, for example, a pair of reflectors (e.g., a pair of distributed Bragg reflectors (DBRs))
Data Source
AI summary
A vertical-cavity surface-emitting laser (VCSEL) array may include a substrate, a wafer bonding layer over the substrate, and a first metal layer on or within the wafer bonding layer. The first metal layer may include a plurality of first electrodes. The VCSEL array may include an epitaxial region over the first metal layer and the wafer bonding layer. The epitaxial region may be bonded to the wafer bonding layer. The VCSEL array may include a second metal layer over the epitaxial region. The second metal layer may include a plurality of second electrodes. The plurality of first electrodes and the plurality of second electrodes may form a plurality of matrix addressable subarrays of the VCSEL array, where each matrix addressable subarray of the plurality of matrix addressable subarrays includes one or more emitters.