Optical Efficiency Enhancement of Nanojet-Based Dielectric Double-Material Color Splitters for Image Sensor Applications.

Oksana Shramkova,Valerie Allié,Valter Drazic,Bobin Varghese,Laurent Blondé

doi:10.3390/nano11113036

Abstract

We propose a new type of color splitter, which guides a selected bandwidth of incident light towards the proper photosensitive area of the image sensor by exploiting the nanojet (NJ) beam phenomenon. Such splitting can be performed as an alternative to filtering out part of the received light on each color subpixel. We propose to split the incoming light thanks to a new type of NJ-based near-field focusing double-material element with an insert. To suppress crosstalk, we use a Deep-Trench Isolation (DTI) structure. We demonstrate that the use of a dielectric insert block allows for reduction in the size of the color splitting element. By changing the position of the DTI, the functionality of separating blue, green and red light can be improved.

Highlights

Image sensors are solid-state devices which are widely used in consumer electronic devices such as smartphones and various digital cameras
In this work we propose a new topology of a double material NJ-based color splitter with Deep-Trench Isolation (DTI) structures to suppress the crosstalk
Si3 N4 was used as material for the outer block with refractive index n2, MgF2 was the material for the insert with refractive index n3, SiNx with refractive index 2.04 was used as an antireflection layer, the DTI layers were simulated with SiO2 material

Summary

Introduction

Image sensors are solid-state devices which are widely used in consumer electronic devices such as smartphones and various digital cameras. In the past decades we have observed significant improvement in the performance of CMOS image sensors [1,2,3,4,5,6,7,8,9,10]. Increasing the resolution of these sensors leads to a decrease of the pixel size. To address the existing problems and to improve pixel performance, diverse sensor structures were proposed. It was demonstrated that to increase the light collection efficiency and to improve optical performance, an image sensor with digital-microlenses [11] can be used, with carefully designed periodic surface structures on crystalline silicon [8], or with a front inner lens located on the front side of the backside illuminated pixel [12]. The shape and material of the color filter [13,14,15,16,17,18,19,20,21,22]

Methods

Results

Conclusion