Curved Lens Structure for Image Sensors
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Solution Overview
Problem
Current image sensors face challenges in maximizing quantum efficiency due to limitations in focusing light on photodiodes, particularly in the design of lens structures and color filter layers, which affect the conversion of photo energy into electrical signals.
Innovation Solution
A lens structure comprising a first curved lens layer, a second curved lens layer, and a curved color filter layer is designed to focus light on photodiodes, with the curved color filter layer having a small thickness and being disposed between or on top of the lens layers, allowing for sequential refraction of light to enhance quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional lens structure with flat or simple curved surfaces is used, then the manufacturing process is simple, but the light focusing capability is insufficient leading to low quantum efficiency
Solution Approach 1:
The patent applies curved surfaces with different radii of curvature to the lens layers. Specifically, the first lens layer has a first curved surface with a first radius of curvature, and the second lens layer has a second curved surface with a second radius of curvature different from the first. This differential curvature design enables sequential refraction of light, improving focusing capability and quantum efficiency while maintaining manufacturing feasibility through standard semiconductor fabrication processes.
2Manufacturing precision
If the color filter layer is made thick to achieve good color separation, then color filtering performance is improved, but the thickness increases reducing light transmission and quantum efficiency
Solution Approach 1:
The patent employs a curved color filter layer with a specific curvature radius rather than a flat configuration. This curvature design allows the color filter to achieve effective color separation while maintaining a thinner profile, thereby improving light transmission and quantum efficiency compared to conventional thick flat color filters.
Solution Approach 2:
The patent optimizes the thickness parameter of the color filter layer by using a curved configuration instead of a flat one. The curved geometry provides enhanced optical path length for color separation while reducing the physical thickness, thus resolving the contradiction between color separation performance and light transmission.
3Manufacturing precision
If the lens structure is designed to focus light tightly on photodiodes, then quantum efficiency is improved, but light crosstalk between adjacent pixels increases
Solution Approach 1:
The patent divides the optical system into multiple segmented lens layers, each with specific curvature radii. The first lens layer has a first radius of curvature and the second lens layer has a second radius of curvature. This segmentation allows sequential refraction that precisely controls light paths, achieving tight focusing on individual photodiodes while preventing light from adjacent pixels from interfering, thus reducing crosstalk.
4Quantity of substance
If the incident angle range is widened to capture more light, then light collection efficiency is improved, but focusing precision on photodiodes deteriorates
Solution Approach 1:
The patent utilizes curved surfaces with optimally designed radius of curvature in both lens layers to achieve an balance between wide incident angle acceptance and precise focusing. The specific curvature radii are designed to refract light from various incident angles while converging it precisely on the photodiode, thereby simultaneously improving light collection efficiency and focusing precision.
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
The proposed lens structure increases quantum efficiency by effectively focusing light on photodiodes, improving the conversion of photons into electrons and reducing light crosstalk and wide incident angles, thereby enhancing image sensing performance.
Implementation Method 1
The lens structure includes a first curved lens layer, a second curved lens layer and a curved color filter layer. The light to be focused enters the first curved lens layer from an upper surface of the first curved lens layer and exit from a lower surface of the first curved lens layer. The second curved lens layer is disposed on the upper surface of the first curved lens layer.
Data Source
AI summary
A semiconductor device and a method for fabricating the semiconductor device are provided. In the method for fabricating the semiconductor device, at first, a dielectric layer is provided. Then, trenches are formed in the dielectric layer. Thereafter, the trenches are filled with spacer material to form a spacer structure in the dielectric layer for defining pixel regions. Then, lens structures are formed on the pixel regions. Each of the lens structures includes a first curved lens layer, a second curved lens layer and a curved color filter layer. The curved color filter layer is disposed on the second curved lens layer or between the first curved lens layer and the second curved lens layer.