Integration of nanostructured planar diffractive lenses dedicated to near infrared detection for CMOS image sensors

Abstract

This paper deals with the integration of metallic and dielectric nanostructured planar lenses into a pixel from a silicon based CMOS image sensor, for a monochromatic application at 1.064 μm. The first is a Plasmonic Lens, based on the phase delay through nanoslits, which has been found to be hardly compatible with current CMOS technology and exhibits a notable metallic absorption. The second is a dielectric Phase-Fresnel Lens integrated at the top of a pixel, it exhibits an Optical Efficiency (OE) improved by a few percent and an angle of view of 50°. The third one is a metallic diffractive lens integrated inside a pixel, which shows a better OE and an angle of view of 24°. The last two lenses exhibit a compatibility with a spectral band close to 1.064 μm.

Enhanced CMOS image sensor by flexible 3D nanocone anti-reflection film

“…The CIS performance is generally determined by the photodiode's structure, doping conditions, manufacturing process and image processing algorithm [11][12][13][14][15][16][17][18]. In recent years, much attention has been paid on optimizing the photodiode, such as the doping concentration, junction depth, junction grading, antireflective coating [10,[19][20][21][22][23][24][25], which relates to the sensitivity, dynamic range, signal to noise ratio, and the spectral response. Additionally, it is worth noting that the CIS needs to be installed with the cover glass in practical applications to protect the sensor from damage, mechanical issues, and environmental conditions such as dust and vapor [14].…”

“…The cover glass is typically taped or glued to the sensor by the manufacturer and it is usually integrated within the vision system or camera directly as-is. However, loss of light due to the reflection in the optical path from airto-cover glass-to-air is a potentially damaging noise source, and can cause unwanted interference in very accurate vision applications [22]. For applications requiring the highest degree of accuracy, system developers will often want to remove the cover glass.…”