Digital Imaging

CMOS and CCD image sensor design and optimization

Overview

As image sensor pixel technologies approach pixel diameters of 1 micron, there has been continued, ongoing work at transitioning from older and less cost-effective technologies like CCD imaging to manufacturing technologies like CMOS processing which are capable of decreasing per unit manufacturing costs while increasing production volumes.  Along the way, CMOS image sensors have had to overcome technical challenges to be able to produce images of sufficient quality, color depth and resolution sufficient for demanding consumer and commercial applications.

With the goal of producing CMOS imagers capable of capturing an incident light signal, and efficiently routing that signal through sophisticated multilayer structures manufactured with standard fabrication processes, rigorous optical simulation that accounts for optical absorption, scattering, and diffraction from sub-wavelength features (like metallic interconnects for the readout electronics, or the curved dielectric surfaces of which the microlens array is constructed) is required.  Current CMOS image sensor architectures employ sophisticated materials from which the color filters are manufactured that must be accurately accounted for by advanced material modeling capabilities within commercial-grade optical simulation tools.  Whether one is interested in analyzing the benefits of front-side versus backside illumination as it relates to light absorbed within the photodiode, quantifying the role of optical or electronic cross-talk, optimizing the microlens shift for oblique angles of incidence, or exploring the impact of adding a light guide to the layer structure, a high performance optical simulator free from approximations is required to accurately and efficiently assess new design concepts.

 

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"Diffraction effects due to decreasing pixel sizes substantially affect photon collection and invalidate a ray tracing model. A more fundamental description is required, and we chose FDTD Solutions from Lumerical."
- F. Hirigoyen, STMicroelectronics

Featured Publications Showcasing Lumerical's Products

F. Hirigoyen, A. Crocherie, J. M. Vaillant, and Y. Cazaux, "FDTD-based optical simulations methodology for CMOS image sensors pixels architecture and process optimization" Proc. SPIE 6816, 681609 (2008) http://dx.doi.org/10.1117/12.766391
S. Tanev, J. Pond, P. Paddon, and V. Tuchin, "FDTD simulation of optical phase contrast microscope imaging", Proc. SPIE, 6991, 69912D (2008). http://dx.doi.org/10.1117/12.781514
J. Vaillant, A. Crocherie, F. Hirigoyen, A. Cadien, and J. Pond, "Uniform illumination and rigorous electromagnetic simulations applied to CMOS image sensors," Opt. Express 15, 5494-5503 (2007) http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-15-9-5494
Axel Crocherie, Pierre Boulenc, Jérôme Vaillant, Flavien Hirigoyen, Didier Hérault, Clément Tavernier, "From photons to electrons: a complete 3D simulation flow for CMOS image sensor," http://www.imagesensors.org/Past%20Workshops/2009%20Workshop/2009%20Papers/036_paper_crocherie_st_modelling.pdf
Fudi Zhang, Jianqi Zhang, Cui Yang, Xiang Zhang, "Performance Simulation and Architecture Optimization for CMOS Image Sensor Pixels Scaling Down to 1.0 ?m," I.E.E.E. transactions on electron devices, 57 (4), 788-794 (2010).
Flavien Hirigoyen, Jérôme Vaillant, Emilie Huss, Frederic Barbier, Jens Prima, François Roy, Didier Hérault, "1.1?m Backside Imager vs. Frontside Imager: an optics-dedicated FDTD approach,"http://www.imagesensors.org/Past%20Workshops/2009%20Workshop/2009%20Papers/011_paper_hirigoyen_st_bsi_fsi_optics.pdf
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Customer Showcase

ST Microelectronics

“"Diffraction effects due to decreasing pixel sizes substantially affect photon collection and invalidate a ray tracing model. A more fundamental description is required, and we chose FDTD Solutions from Lumerical."- F. Hirigoyen, STMicroelectronics