Imec has unveiled a groundbreaking color-splitting technology for CMOS imagers, presented at IEEE IEDM 2023. This innovation overcomes limitations of traditional color filters by utilizing vertical Si3N4 multimode waveguides on 300mm wafers, fabricated with standard back-end-of-line processing. The new method achieves sub-micron pixel resolution, surpassing the Abbe diffraction limit, by spatially separating incident light frequencies based on unique "beating" patterns within the waveguides. This approach ensures near-total photon collection (over 90% light output in the human visual range), resulting in significantly higher signal-to-noise ratio, superior color quality (Vora value > 95%), and unprecedented spatial resolution. Imec positions this cost-efficient technology as the future standard for diffraction-limited color imaging, actively seeking industry partners for full camera demonstrations across applications like smartphones, automotive, and medical endoscopy.
Summarizing Imec's Breakthrough in Color Imaging Technology
Key Announcement (December 11, 2023): Imec presented a fundamentally new color-splitting method at IEEE IEDM 2023, designed to revolutionize camera performance with sub-micron pixel resolution.
Addressing Current Limitations: Traditional CMOS imagers using Bayer color filters struggle to balance photon collection, resolution, and color accuracy, often absorbing up to 70% of incoming light and suffering from interpolation artifacts with smaller pixels. Diffraction-based splitters improved sensitivity but not resolution.
Imec's Novel Approach: The new method enables color splitting at sub-micron pixel sizes (beyond the Abbe diffraction limit) using standard 300mm back-end-of-line processing. It aims to collect nearly all photons, increase resolution with very small pixels, and render colors faithfully.
Technical Mechanism: Researchers built an array of vertical Si3N4 multimode waveguides in an SiO2 matrix. Incident photons excite symmetric and asymmetric modes within each waveguide, creating a unique "beating" pattern that spatially separates light corresponding to specific colors at the waveguide's output.
Superior Light Efficiency: The waveguides are estimated to output over 90% of incident light within the 400-700nm human perception range, significantly outperforming traditional color filters. Light is "split" and directed, rather than "filtered" and absorbed.
Cost-Effective Manufacturing: The technology's compatibility with standard 300mm processing allows for cost-efficient production, enabling further scaling of high-resolution imagers.
Performance Benefits: This results in a higher signal-to-noise ratio, enhanced color quality, unprecedented spatial resolution, and exceptional color accuracy (Vora value > 95%). The higher refractive index of the waveguides effectively shrinks photons, allowing for pixel scaling below the diffraction limit.
Future Ambition & Partnerships: Imec's ambition is for this technology to become the future standard for color imaging with diffraction-limited resolution, actively inviting industry partners for full camera demonstrations.
Target Applications: This innovation is highly relevant for numerous markets, including smartphones, automotive, and medical (e.g., endoscopy).