Expanded 180nm process with new isolation class for enhanced SPAD integration

X-FAB Silicon Foundries SE has released a new isolation class within its 180nm XH018 semiconductor process. Designed to support more compact and efficient SPAD implementations, this new isolation class allows tighter functional integration, improved pixel density, and higher fill factor – resulting in a smaller chip area.

SPADs are critical components in a broad range of emerging applications, including LiDAR for autonomous vehicles, 3D imaging, depth sensing in AR/VR systems, quantum communication and biomedical sensing. The company already offers several SPAD devices built on its 180nm XH018 platform, with active areas ranging from 10µm to 20µm. This includes a near-infrared optimised diode for elevated photon detection probability (PDP) performance.

To allow high-resolution SPAD arrays, a compact pitch and elevated fill factor are essential. The newly released module ISOMOS1, a 25V isolation class module, allows for significantly more compact transistor isolation structures, eradicating the necessity 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 4x3 SPAD array with 10x10µm² optical areas, the adoption of the new isolation class enables a ~25% reduction in total area and boosts fill factor by ~30% compared to the previously available isolation class. With carefully optimised pixel design, even greater gains in area efficiency and detection sensitivity are attainable.

The company’s SPAD solution has been widely used in applications that require direct ToF, such as smartphones, drones, and projectors. This new technological advancement directly benefits these applications in which high-resolution sensing with a compact footprint is vital. It enables accurate depth sensing in various scenarios, including industrial distance detection and robotics sensing, for example, by protecting the area around a robot and preventing collisions when robots work as cobots. Beyond increasing performance and integration density, the new isolation class opens up opportunities for a broader range of SPAD-based systems needing 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.