CSC, SPTS, Cardiff and Swansea conclude high-efficiency VCSEL manufacturing project

The Compound Semiconductor Centre Ltd (CSC) of Cardiff, Wales, UK and its partners (Orbotech company SPTS Technologies Ltd, Cardiff University and Swansea University) have successfully concluded the project ‘High Efficiency Manufacturing of Vertical Cavity Surface Emitting Lasers (VCSELs)’, which was funded by UK Government agency InnovateUK.

The project has delivered key process modules required to transition small-diameter manufacturing processes currently used for VCSELs to a high-uniformity 150mm epitaxial platform. The need for scale-up is driven by significant benefits in terms of productivity (4x more die sites in transitioning from 75mm to 150mm) and yield (a smaller ratio of edge sites to total area for larger wafer diameters) to facilitate a step change in cost reduction for VCSELs, and thus accelerate adoption in mass-market applications such as 3D imaging, proximity sensing, range-finding and light detection and ranging (LiDAR).

The work included the commissioning of a custom 150mm oxidation tool at Cardiff University’s Institute for Compound Semiconductors (ICS) which is used for a particularly challenging stage of preferential oxidation of aluminium-rich layers in the VCSEL layer structure, in order to produce a high-efficiency optical waveguide in the device. High-quality mesa dry etch processes to >5µm were developed by SPTS on GaAs/AlGaAs epitaxial structures supplied by CSC, with Swansea supporting plasma-enhanced chemical vapor deposition (PECVD) and photo process steps, to complement the oxidation process module; essential for a high-uniformity, high-reliability 150mm VCSEL fabrication platform. A robust process solution was developed, including in-situ depth targeting end-point detection capability. A benchmark of <±5% mesa depth uniformity across a full 150mm VCSEL epitaxial wafer structure was demonstrated.

The capability will form the core of a future 150mm VCSEL prototyping capacity that will be leveraged by the consortium to work on custom VCSEL development, device-scale optimization and validation of VCSEL epitaxial materials development as a core research and manufacturing competence in the emerging CSconnected compound semiconductor cluster in South Wales.

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