X-FAB Enhances 180nm XH018 Process with New Isolation Class for Improved SPAD Integration

Key Takeaways

X-FAB introduces a new isolation class for its 180nm XH018 semiconductor process, aimed at enhancing SPAD efficiency.
The ISOMOS1 module allows for a ~25% reduction in SPAD pixel area and a ~30% increase in fill factor.
This development benefits various applications, including autonomous vehicles and AR/VR systems, by enabling high-resolution sensing in a compact design.

Innovative SPAD Developments by X-FAB

X-FAB Silicon Foundries SE, based in Tessenderlo-Ham, Belgium, has unveiled a new isolation class within its renowned 180nm XH018 semiconductor process. This advance is designed to facilitate more compact and efficient implementations of single-photon avalanche diodes (SPADs), crucial components in a variety of cutting-edge applications. By enabling tighter functional integration and higher fill factor, this innovation leads to smaller chip areas.

SPADs are instrumental in several domains, including LiDAR technology for autonomous vehicles, 3D imaging, depth sensing for augmented and virtual reality systems, quantum communication, and biomedical applications. X-FAB has already developed multiple SPAD devices using the 180nm XH018 platform, featuring active areas ranging from 10µm to 20µm. Among them is a near-infrared optimized diode designed to enhance photon detection probability (PDP).

To achieve high-resolution SPAD arrays, key factors include compact pitch and elevated fill factor. X-FAB’s newly introduced ISOMOS1 module, which operates at 25V, enables significantly more compact transistor isolation structures. This advancement negates the necessity for an additional mask layer, aligning seamlessly with X-FAB’s existing SPAD variants.

The advantages of this new isolation class are particularly noticeable when analyzing SPAD pixel layouts. For example, a standard 4×3 SPAD array with 10×10µm² optical areas experiences approximately a 25% reduction in total area, along with a 30% increase in fill factor, thanks to the new isolation class. With meticulous pixel design optimization, even greater improvements in area efficiency and sensitivity can be realized.

X-FAB’s SPAD solutions are extensively utilized in applications demanding direct time-of-flight measurements, such as smartphones, drones, and projectors. The enhancements offered by this new isolation class will directly benefit these sectors, where compact and high-resolution sensing is vital. This innovation facilitates precise depth sensing in various scenarios, including industrial distance detection and robotic applications, ensuring safety by minimizing collision risks during interactions with collaborative robots.

Heming Wei, X-FAB’s Technical Marketing Manager for Optoelectronics, stated, “The introduction of a new isolation class in XH018 marks a significant advancement for SPAD integration. It allows for tighter layouts and improved performance, paving the way for the development of more sophisticated sensing systems on our established 180-nanometer platform.”

Engineers can now access models and process design kits (PDKs), including the new ISOMOS1 module, to support the efficient evaluation and development of next-generation SPAD arrays. X-FAB will showcase these latest sensor technologies at the Sensors Converge 2025 event in Santa Clara, California, from June 24–26, at booth #847.

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