VCSEL Array Insulating Grooves for Uniform Burn-in Current
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Solution Overview
Problem
In vertical cavity surface emitting laser arrays, ensuring uniform load currents across all elements during burn-in tests is challenging due to potential leakage through conductive semiconductor layers, which affects the accuracy and cost-effectiveness of the testing process.
Innovation Solution
A vertical cavity surface emitting laser array configuration with parallel wiring lines and insulating regions on a semiconductor substrate, where dummy pads supply load current and resistances are set to maintain uniformity, preventing leakage and ensuring consistent load conditions across all elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If surface emission elements are connected in series in the orientation that the forward directions of light-emitting element units match, then burn-in test can be performed on a wafer state, but load current leakage occurs through the conductive semiconductor layer causing non-uniform load conditions
Solution Approach 1:
The patent divides the semiconductor substrate into multiple isolated element units by introducing insulating regions. Each vertical cavity surface emitting laser element is electrically isolated from its neighbors through these insulating regions, preventing current leakage while maintaining series connection for wafer-level testing. This segmentation allows independent current control for each element column.
Solution Approach 2:
The patent introduces insulating regions as intermediary structures between adjacent laser elements and element columns. These insulating regions act as mediators that block unwanted current leakage paths through the conductive semiconductor substrate while allowing the desired series connection through controlled wiring lines. The insulating regions include both first insulating regions between elements and second insulating regions between element columns.
2Reliability
If insulating regions are introduced to prevent current leakage, then load current uniformity is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple insulating region functions into a unified structure. The first insulating regions between adjacent elements and the second insulating regions between element columns are integrated into the same insulating layer system, reducing the total number of separate insulating structures. This combining approach maintains current isolation while simplifying the overall device architecture.
Solution Approach 2:
The patent applies insulating regions selectively at specific locations where current leakage would occur, rather than uniformly across the entire substrate. The insulating regions are positioned precisely between adjacent elements and between element columns, providing localized current blocking only where needed. This approach maintains simplicity in non-critical areas while ensuring isolation where required.
Data Source
AI summary
A VCSEL array includes a base substrate, VCSEL element columns arranged in a row direction (y direction) on a front-surface side of the base substrate and parallel wiring lines that connect the VCSEL element columns in parallel with each other. Each of the VCSEL element columns includes a plurality of VCSEL elements arranged in a column direction (x direction) and a plurality of series wiring lines. The plurality of series wiring lines serially connect every two VCSEL elements that are adjacent to each other in the column direction among the plurality of VCSEL elements in such an orientation that the forward directions of the two VCSEL elements match. Insulating grooves are formed on the base substrate. The insulating grooves electrically insulate the VCSEL element columns from each other. The insulating grooves electrically insulate the VCSEL elements from each other.