Mr. Jefferson Abrenica Profile

Jefferson Abrenica

at ams Sensors Asia Pte Ltd

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Publications (2)

Proceedings Article | 18 April 2021 Paper

Electrical and physical failure analysis techniques for oxide aperture delineation in high-power oxide-confined VCSEL arrays

Xiaoyan Wang, Jefferson Abrenica

Proceedings Volume 11777, 117770S (2021) https://doi.org/10.1117/12.2589056

KEYWORDS: Oxides, Vertical cavity surface emitting lasers, Failure analysis, Transmission electron microscopy, Light emitting diodes, Reliability, Oxidation, Optics manufacturing, Near field optics, Three dimensional sensing

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The demand for high-power vertical cavity surface emitting laser (VCSEL) with multiple-emitters is dramatically growing for 3D sensing application in consumable and automotive electronics. Oxide confinement technology is favorable for 2D VCSEL arrays with the advantage of small threshold current, low manufacture cost and high power conversion efficiency. Since both current and optical light is confined by the insulating oxide layer, oxide aperture delineation will be useful for VCSEL array characterization and failure analysis. In this work, electrical and physical failure analysis techniques are utilized for oxide aperture delineation for both good and dim emitters in 2D VCSEL array chip, which has been subjected to overstress test. Three different kinds of techniques, that is, near-field testing (NFT), infrared (IR) microcopy and planar-view transmission electron microscopy (PVTEM) are used to investigate the entire oxide aperture confined region, which is the essential region for VCSEL lasing. From functional view of point, NFT emission pattern below threshold current provide emission profile from each emitter, which is related with oxide aperture confinement. From physical view of point, IR and PVTEM images provide emitter structure analysis to correlate with emission pattern. For good emitter (Emitter 1), electrical near-field testing below threshold current shows circular shape, uniform emission pattern. Non-destructive IR images and destructive planar-view TEM confirm the round-shape oxide aperture. For bad emitters (Emitter 2 and Emitter 3), NFT images below threshold show the dark spot at the emission pattern. IR images is only able to provide oxide aperture shape and reveal oxidation defect. PVTEM is able to capture both dark-line defect and further oxidation failure, which correlate with the dark spot site in NFT emission pattern. This work demonstrates the effectiveness of the three techniques for oxide aperture delineation and provide good correlation between NFT emission profile and PVTEM aperture morphology. It also can link weak emission location with physical defect site in the dim emitter. These combined techniques can work together for oxide aperture delineation and fault isolation in 2D VCSEL arrays.

Proceedings Article | 1 April 2020 Presentation + Paper

3D transmission electron microscopy method development for failure analysis in VCSEL arrays

Xiaoyan Wang, Jefferson Abrenica, Patrick Koh

Proceedings Volume 11356, 1135612 (2020) https://doi.org/10.1117/12.2552350

KEYWORDS: Oxides, Vertical cavity surface emitting lasers, Transmission electron microscopy, Failure analysis, Oxidation, Reliability, Infrared imaging, Electron tomography, Copper, Array processing

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High power vertical cavity surface emitting laser (VCSEL) arrays with multiple emitters have been receiving remarkable attention currently due to their emerging applications in consumer market such as 3D sensing illumination laser source in mobile devices as well as in automotive LIDAR applications. Failure mode analysis will help provide useful information for VCSEL array design and process improvement. However, using solely general physical failure analysis techniques is insufficient. The challenge of failure mechanism study is how to locate and capture the small physical defects in the early stage since it may randomly occur in the entire active region of the emitter This work developed 3D transmission electron microscopy (TEM) method, that is, planar-view TEM together cross-section TEM, to investigate failure mode phenomenon in this kind of high power VCSEL arrays. Overstressed reliability testing intentionally create failure in VCSEL arrays where dim emitters are found. Optical microscope images can’t see any abnormality while infrared microscope can catch small ‘mouse-bite’ abnormality at oxide aperture. Planar-view TEM method is developed to isolate the target dim emitter and trim away most of the top and bottom DBR layers to keep the oxide layer and active region to thin enough where 200KV electron beam can penetrate planar-view lamella. The whole oxide aperture is achieved and scanning TEM images clearly show the ‘flower-like’ oxide blasters at oxide aperture periphery. It is from further oxidation of the oxide tip. Cross-section TEM reveal the oxide layer morphology where the further oxidation layer from oxide tip is thinner than the original oxide layer. The oxide tip further oxidation is possibly due to non-reaction steam in existence in the oxide causing the second oxidation of oxide layer during overstress test. This work demonstrate that 3D TEM method is good technique to catch small physical failure features in VCSEL arrays, which will help to analyze failure mode in high power VCSEL arrays for 3D sensing application.

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