Design and Integration of Plasmonic Lenses Dedicated to Near Infrared Detection (1.064 μm) for CMOS Image Sensors

Thomas Lopez DEOS, ISAE-SUPAERO Université de Toulouse, Toulouse, France Sébastien Massenot DEOS, ISAE-SUPAERO Université de Toulouse, Toulouse, France Magali Estribeau DEOS, ISAE-SUPAERO Université de Toulouse, Toulouse, France Pierre Magnan DEOS, ISAE-SUPAERO Université de Toulouse, Toulouse, France Jean-Luc Pelouard MiNaO, LPN-CNRS, Marcoussis, France

The interest of the near infrared spectral band in imaging applications is well established, the fact that these waves are less scattered than visible light provide them a great potential of applications in the field of security and defense (vision through fog, for example). Image sensors for laser active imaging in this spectral band are mostly based on III-V materials [1]. However, there is a strong interest in using silicon-based detectors to reduce manufacturing cost. Unfortunately, silicon absorptivity and quantum efficiency are not high enough at this wavelength to compete with conventional NIR detection technology. One potential solution is to integrate light collection functions at the level of each pixel. Due to their exceptional confinement properties, plasmonic structures will be involved. They have already been studied to enhance silicon based photodetetectors performances. For instance, plasmonic color filters for CMOS image sensor applications and improving light absorption in solar cells using metal nanoparticules have been investigated. This contribution deals with the design of plasmonic lenses in order to enhance the collection of near-infrared photons in the photosensitive area for a standard CMOS imager. In order to cause the least possible disruption to the CMOS fabrication process, such structures will be deposited at the top of passivation layers (post-process integration). The first design explored is the Plasmonic Lens [2]. Nevertheless, the complex combination of nanoscale high aspect ratio slits is hardly achievable. This design can be greatly simplified releasing technological constraints: the simplified system is called Huygens Lens [3]. Numerical simulations have been performed through finite-difference time domain to optimize the structures both integrated into a pixel. Performances of both lenses are compared.

[1] J. Bentell et al., “Flip chipped INGaAs photodiode arrays for gated imaging with eye-safe lasers", Solid-State Sensors, Actuators and Microsystems Conference, 2007.
[2] P. B. Catrysse et al., “Nanoscale slit arrays as planar far-field lenses", SPIE NanoScience Engineering, International Society for Optics and Photonics, 2009.
[3] Q. Levesque et al., “Compact planar lenses based on a pinhole and an array of single mode metallic slits", Journal of the European Optical Society - Rapid publications;Oct. 2013.

thomas.lopez@isae.fr









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