CEA-Leti will present its latest research for the first time at the ECTC conference, through a paper concluding its work carried out within the European TINKER project. This EU-funded initiative aims to develop innovative manufacturing technologies for customized sensors, with a focus on autonomous vehicles.
www.leti-cea.com, May. 28, 2025 –
This research highlights an advanced 3D integration technology that combines TSVs (Through Silicon Vias) and flip-chip bonding applied to silicon photonics. It enables the design of a compact, high-performance laser scanning module.
This innovation is embedded in a 256-channel LiDAR system, specifically designed to meet the miniaturization, energy efficiency, and industrial scalability requirements of tomorrow's automotive applications.
While autonomous driving continues to generate strong interest among automakers, it still faces major technological challenges. Today, only two types of sensors are widely used in autonomous vehicles: radar and cameras. Radar is effective for long-range detection but lacks precision at short distances. Cameras, on the other hand, do not fill that gap and are limited in adverse conditions such as fog, poor weather, or night driving.
This is where LiDAR becomes essential. Thanks to its laser-based technology, it provides precise and reliable detection. A light beam is projected and, once reflected off an object, delivers information not only on distance but also on the shape of the detected object. This is a crucial step forward for improving the safety and performance of autonomous driving systems.
This type of sensor is now seen as the preferred solution by most automotive stakeholders. CEA also brings strong expertise to this field through the creation of the start-up SteerLight, which builds on compatible R&D efforts conducted at CEA-Leti.
CEA-Leti contributes its expertise from device to system by applying 3D integration and advanced packaging to a silicon photonics-based device. The goal: hybridize the LiDAR system onto a silicon interposer.
At the core of this technology is an Optical Phased Array (OPA), a true miniature laser scanning system. Light propagates through waveguides fed by a laser connected via four optical fibers. These beams are then split into 256 optical channels, enabling a precise field-of-view scan.
This scanning, covering an angle from -20° to +20°, is controlled thermally, with independent activation for each of the 256 channels. This is made possible through dedicated interconnects, routed to the backside of the substrate using TSVs.
Routing is then completed on the back side, along with the creation of compact solder bumps (tin/silver, 20 µm in diameter with a 40 µm pitch), enabling bonding to the interposer using Flip-Chip technology.
The photonic components and laser beam output are located on the front side of the device, while the signal is redirected to the back side and down to the interposer. In the future, this interposer could integrate additional components such as CMOS driver and receiver circuits, along with other subsystems.
This architecture provides significant space savings and offers great flexibility for product evolution. The integration process relies on precise interconnects to ensure reliable communication between the functional layers of the device.
This back-end hybridization and interconnect technology enables over 80% space savings compared to conventional wire bonding packaging—an important advantage for in-vehicle integration.
Thanks to the silicon interposer, other critical components such as control circuits, memory, or additional sensors can be directly embedded onto the chip.
This approach also offers significant cost-reduction potential. Unlike most current LiDAR fabrication technologies, all components here are collectively manufactured on 300 mm silicon wafers using standardized, well-established semiconductor processes.
To make autonomous vehicles a large-scale reality, a combination of three types of sensors: camera, radar, and LiDAR will be necessary. LiDAR, in particular, must be compact, energy-efficient, and cost-effective.
The technology developed at CEA-Leti meets all these requirements. It offers high integration density, controlled power consumption (approximately 20 W for emission), and compatibility with large-scale industrialization.