CMOS Compatible Metasurface for Frequency Selective Infrared Emission

Anthony Lefebvre CEA, LETI, MINATEC Campus, Grenoble, France Laboratoire Charles Fabry, Institut d'Optique, CNRS, Palaiseau, France Daniele Costantini Laboratoire Charles Fabry, Institut d'Optique, CNRS, Palaiseau, France Ioana Doyen Laboratoire Charles Fabry, Institut d'Optique, CNRS, Palaiseau, France Quentin Lévesque Laboratoire Charles Fabry, Institut d'Optique, CNRS, Palaiseau, France Emerick Lorent CEA, LETI, MINATEC Campus, Grenoble, France Jacolin David CEA, LETI, MINATEC Campus, Grenoble, France Jean-Jacques Greffet Laboratoire Charles Fabry, Institut d'Optique, CNRS, Palaiseau, France Salim Boutami CEA, LETI, MINATEC Campus, Grenoble, France Henri Benisty Laboratoire Charles Fabry, Institut d'Optique, CNRS, Palaiseau, France

Compact and cheap infrared sources are needed for many applications such as gas detection. Incandescent sources are generally used although their efficiency is very low. It can be increased by means of metasurfaces that emit in a limited bandwidth and in a limited solid angle. Here, we report the simulation and fabrication of fully CMOS compatible Metal Insulator Metal (MIM) mid-infrared resonators on 200 mm silicon wafers. These MIMs use tungsten (W) as metal, instead of noble metals such as gold which have better optical properties but would be contaminant in CMOS foundries. The devices consist in a 200 nm thick Silicon nitride (SiN) layer sandwiched between 100 nm thick tungsten (W) patches on the top side and a uniform 100 nm thick tungsten layer on the bottom side. The ~800 nm large patches were defined by deep UV lithography. We show here that these materials and their fabrication techniques result in low-cost mass production of MIM devices.

Technically, the influence of patch sizes, periodicities, or shapes of MIMs are studied. More complex designs are also tested, among which bi- and tri-resonant (for frequency sorting) MIMs. The MIM mode is known to resonate at a specific wavelength, depending on its geometry, and to generally be rather angle independent. We demonstrate the possibility to limit the resonance to a chosen range of angles around normal, by adjusting the periodicity of the patches and modifying the critical coupling condition. Further angular selectivity can be reached using 3^rd order MIMs, whose behavior will be enlightened at the conference, based on ongoing in-depth analysis. Characterizations were made on a FTIR with both reflectivity and emissivity setups, allowing us to investigate materials` behavior up to typical emitter temperatures.

The ongoing work now focuses on implementing such devices on suspended micromembranes in order to design efficient radiation sources in the mid-infrared.

a) Illustration of the MIM structure; b) 200 mm silicon wafer with MIMs. Each die is 5x5 mm2 and consists of a specific kind of MIMs; c) Comparison of simulated and experimental emissivity close to the normal, here at the CO2 absorption line.

anthony.lefebvre@cea.fr