PDMS Antireflective Layer for Image Sensor Light Collection
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Solution Overview
Problem
Complementary metal-oxide-semiconductor (CMOS) image sensors face challenges with limited light transmission and reflection due to small angles of incident light, which affect quantum efficiency and sensitivity.
Innovation Solution
Incorporating a polydimethylsiloxane (PDMS) layer with subwavelength nanostructures, such as arrays of convex protuberances or concave recesses, formed using a porous anodic aluminum oxide template, to increase light absorption and reduce reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a conventional flat coating is used on the image sensor, then the manufacturing process is simple, but light transmission is limited and reflection occurs at small angles of incident light
Solution Approach 1:
The patent applies a porous coating layer with controlled pore sizes (subwavelength dimensions) on the image sensor surface. The porous structure increases light absorption by reducing reflection at small angles of incident light, while the pores are filled with material having appropriate refractive index to optimize optical performance without significantly complicating the manufacturing process
Solution Approach 2:
The patent modifies the optical parameters of the coating layer by controlling the pore size, material composition, and thickness to achieve optimal light transmission. The coating is designed with specific refractive index and porosity parameters to minimize reflection while maintaining manufacturability
2Use of energy by moving object
If the angle of incidence for incident light is increased, then light absorption is improved, but the sensor's sensitivity and quantum efficiency are reduced
Solution Approach 1:
The porous coating structure is designed to manipulate light paths through multiple scattering and absorption events within the pore network. This allows the coating to increase effective light absorption without requiring high angles of incidence, thereby maintaining the sensor's quantum efficiency and sensitivity while improving overall light capture
Solution Approach 2:
The coating layer uses composite material structures combining porous substrate with fill materials of appropriate refractive index. This composite approach enables optimization of both light absorption and quantum efficiency by balancing the optical properties of the coating with the sensor's detection characteristics
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances light collection and sensitivity by increasing the angle of incidence for the image sensor, thereby improving quantum efficiency and reducing glare.
Implementation Method 1
a polydimethylsiloxane antireflective layer for an image sensor. The image sensor may include a pixel array and a polydimethylsiloxane (PDMS) layer above the pixel array. A surface of the PDMS layer may include a plurality of structures each having a respective width less than a wavelength of incident light that is to be sensed by the pixel sensor
Implementation Method 2
enhances light collection and sensitivity by increasing the angle of incidence for the image sensor, thereby improving quantum efficiency and reducing glare
Data Source
AI summary
An image sensor may include a polydimethylsiloxane (PDMS) layer that is subwavelength, hydrophobic, and/or antireflective. The PDMS layer may be fabricated to include a surface having a plurality of nanostructures (e.g., an array of convex protuberances and/or an array of concave recesses). The nanostructures may be formed through the use of a porous anodic aluminum oxide (AAO) template that uses a plurality of nanopores to form the array of convex protuberances and/or the array of concave recesses. The nanostructures may each have a respective width that is less than the wavelength of incident light that is to be collected by the image sensor to increase light absorption by increasing the angle of incidence for which the image sensor is capable of collecting incident light. This may increase the quantum efficiency of the image sensor and may increase the sensitivity of the image sensor.