X-FAB expands 180nm process with new SPAD isolation class
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X-FAB Silicon Foundries SE has released a new isolation class within its 180nm XH018 semiconductor process, which supports more compact and efficient single-photon avalanche diode (SPAD) implementations.
The new isolation class enables tighter functional integration, improved pixel density, and higher fill factor, resulting in a smaller chip area. SPADs are critical components in a wide range of emerging applications, including LiDAR for autonomous vehicles, 3D imaging, depth sensing in AR/VR systems, quantum communication and biomedical sensing. X-FAB already offers several SPAD devices built on its 180nm XH018 platform, with active areas ranging from 10 µm to 20 µm. This includes a near-infrared-optimised diode for enhanced photon detection probability (PDP) performance.
To enable high-resolution SPAD arrays, a compact pitch and elevated fill factor are essential. The newly released module ISOMOS1, a 25-V isolation class module, permits significantly more compact transistor isolation structures, eliminating the need for an additional mask layer and aligning perfectly with X-FAB’s other SPAD variants.
The benefits of this enhancement are evident when comparing SPAD pixel layouts. In a typical 4×3 SPAD array with 10-by-10 µm optical areas, the adoption of the new isolation class enables a reduction of approximately 25% in total area. Furthermore, it increases the fill factor by around 30% compared to the previously available isolation class. With carefully optimised pixel design, even greater improvements in area efficiency and detection sensitivity are achievable.
X-FAB SPADs are widely used in applications that require direct Time-of-Flight, such as smartphones, drones, and projectors. This new technological advancement directly benefits these applications in which high-resolution sensing with a compact footprint is essential. It enables accurate depth sensing in multiple scenarios, including industrial distance detection and robotics sensing, for example, by protecting the area around a robot and avoiding collisions when robots are working as cobots. Beyond increasing performance and integration density, the new isolation class opens up opportunities for a broader range of SPAD-based systems requiring low-noise, high-speed single-photon detection within a compact footprint.
Heming Wei, X-FAB’s Technical Marketing Manager for Optoelectronics, explains: “The introduction of a new isolation class in XH018 marks an important step forward for SPAD integration. It enables tighter layouts and better performance, while allowing for more advanced sensing systems to be developed using our proven, reliable 180-nanometer platform.”
Models and PDKs, including the new ISOMOS1 module, are now available, supporting efficient evaluation and development of next-generation SPAD arrays.
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