Near-infrared sensitivity improvement by plasmonic diffraction for a silicon image sensor with deep trench isolation filled with highly reflective metal

We propose a plasmonic diffraction structure combined with deep trench isolation (DTI) filled with highly reflective metal to enhance the near-infrared (NIR) sensitivity of image sensors. The plasmonic diffraction structure has a silver grating on the light-illuminated surface of a typical silicon backside-illuminated CMOS image sensor. The structural parameters of the silver grating were investigated through simulations, and the mechanism of the NIR sensitivity enhancement was clarified. Under the quasi-resonant conditions of surface plasmon polaritons, incident NIR light effectively diffracted as a propagating light to the sensor silicon layer. The diffracted light travelled back and forth between the DTIs. The effective propagation length in silicon was extended to six times by silver-filled DTI, resulting in approximately five times improvement of the 3-mu m-thick silicon absorption at a wavelength of 940 nm. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Automated summary

A plasmonic diffraction structure combined with deep trench isolation filled with reflective metal is proposed to enhance the near-infrared sensitivity of image sensors. The silver grating on the light-illuminated surface of a CMOS image sensor was investigated to clarify the mechanism of NIR sensitivity enhancement. Incident NIR light effectively diffracted as propagating light to the sensor silicon layer under quasi-resonant conditions of surface plasmon polaritons.