Fabrication of a monolithically integrated multiple wavelength Fabry-Perot filter array using transparent etch stop layers for accurate wavelength determination

In this paper we describe a method of fabricating a Fabry-Perot filter array consisting of four distinct wavelengths using a stopping layer, which in turn is discriminately measured. Precise control of the oxide thickness is demonstrated by using reflectance to measure center wavelengths (CWL) between 645nm-822nm with full width half maximum (FWHM) values of 15 nm. These parameters are used to confirm good narrow band filter characteristics. The physical and chemical properties of an oxide layer converted from a silicon-carbon-nitride (SiCN) etch stop layer (ESL) is reported for both as-deposited and the resultant oxidized film. The filter array can be fabricated directly on top of silicon photo diodes, to form a complete multi-wavelength sensor system. Fabricating a multi-wavelength filter array using etch-stop layers can provide better thickness control and across wafer uniformity compared to a timed-etch approach.