X-Fab Rolls Out Process For Single-Photon Avalanche Diodes
The 180nm foundry process will enable a new class of SPAD devices
By Mark LaPedus
Belgium’s X-Fab Silicon Foundries has expanded its 180nm process offerings, rolling out a technology that will enable a new class of single-photon avalanche diode (SPAD) devices.
X-Fab, a specialty foundry vendor, has released a new isolation class module technology, which is designed to enable more compact and efficient SPAD devices. The isolation technology, called the ISOMOS1 module, is part of the company’s 180nm XH018 process. XH018 is a modular 180nm sensor and high-voltage technology for use in automotive and other applications.
Photodetectors are devices that detect light. A SPAD “defines a class of photodetectors able to detect low intensity signals (down to the single photon) and to measure the time of the photon arrival with high temporal resolution (few tens of picoseconds),” according to MEETOPTICS, a supplier of photonics products.
SPADs are critical components used in various applications, such as 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 10µm to 20µm. This includes a near-infrared optimized diode for elevated photon detection probability (PDP) performance.
X-Fab’s new isolation technology will enable next-generation SPAD devices. The process enables a tighter functional integration, improved pixel density, and higher fill factor–resulting in smaller chip area. The company’s new ISOMOS1, a 25V isolation class module, allows for more compact transistor isolation structures, eliminating the need for an additional mask layer.
The benefits of this enhancement are evident when comparing SPAD pixel layouts. In a typical 4 x 3 SPAD array with 10 x 10µm² optical areas, the adoption of the new isolation class module enables a ~25% reduction in total area and boosts fill factor by ~30% compared to the previously available isolation class technologies. With an optimized pixel design, even greater gains in area efficiency and detection sensitivity are achievable.
The new isolation class technology opens up opportunities for a broader range of SPAD-based systems requiring low-noise, high-speed single-photon detection within a compact footprint. The isolation solution is targeted for applications that require direct time-of-flight, such as smartphones, drones and projectors. It enables accurate depth sensing in multiple scenarios.
Heming Wei, X-Fab’s technical marketing manager, said: “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.