Image Sensor Phase Modulator for Photodiode Light Uniformity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In CMOS image sensors, the misalignment of the lens layer with the color filter layer and photodiodes causes an imbalance in energy distribution of external light due to deep trench isolations, leading to light-spot shifting and channel imbalance issues.
Innovation Solution
The introduction of a phase modulator with deflectors and a covering layer having different refractive indices, which uniformly distributes external light by creating phase differences through light interference, ensuring photodiodes receive uniform light intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If deep trench isolations are used to separate photodiodes, then photodiode separation and signal isolation are improved, but light energy distribution uniformity deteriorates causing channel imbalance
Solution Approach 1:
A deflector structure with specific refractive index is introduced as an intermediary component between the color filter layer and lens layer. This deflector mediates the light path to redistribute light energy uniformly across photodiodes while maintaining the deep trench isolation structure for signal separation. The deflector acts as a optical mediator that corrects the non-uniform light distribution caused by misalignment without compromising photodiode isolation.
Solution Approach 2:
The refractive index of the deflector is specifically optimized (with the covering layer having a refractive index 0.15-0.6 higher than the deflector) to control light bending and redistribution. By changing the optical parameters (refractive index) of the deflector and covering layer, the light energy distribution is adjusted to achieve uniformity across different photodiodes while maintaining effective isolation.
2Ease of manufacture
If lens layer is misaligned with color filter layer and photodiodes, then manufacturing tolerance is improved, but light-spot position accuracy deteriorates causing channel imbalance
Solution Approach 1:
The deflector is pre-configured with specific geometric parameters (bottom width-to-pixel-dimension ratio of 1-1.8, height of 150-800 nm) and refractive index properties before final assembly. This preliminary design of the deflector structure enables it to automatically compensate for misalignment effects, allowing manufacturing with relaxed tolerances while maintaining accurate light-spot positioning on photodiodes.
Solution Approach 2:
The deflector serves as an intermediary optical element that decouples the alignment requirements between lens layer and photodiodes. By introducing this intermediate component with controlled optical properties, the system can tolerate larger misalignments in manufacturing while still achieving accurate light delivery to the intended photodiode, thus improving ease of manufacture without sacrificing position accuracy.
3Illumination intensity
If deflector dimensions are optimized for light distribution, then light uniformity is improved, but device complexity increases
Solution Approach 1:
The deflector is designed with specific local geometric characteristics (bottom width-to-pixel-dimension ratio of 1-1.8, height of 150-800 nm, and specific aspect ratios) that are optimized for light redistribution. Rather than making the entire device complex, only the deflector region has specialized geometry, while other parts of the image sensor maintain standard simple structures, thus achieving light uniformity with minimal increase in overall device complexity.
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 solution effectively addresses channel imbalance by ensuring photodiodes detect uniform light intensity, enhancing the performance of the image sensor by uniformly distributing light and reducing light-spot shifting.
Implementation Method 1
A refractive index of the covering layer is greater than a refractive index of the first deflector, and a difference value between the refractive index of the covering layer and the refractive index of the first deflector is in a range from 0.15 to 0.6
Implementation Method 2
uniformly distributes external light by creating phase differences through light interference
Data Source
AI summary
An image sensor includes a photoelectric conversion layer, a plurality of deep trench isolations, a first color filter, a first deflector, and a covering layer. The photoelectric conversion layer includes a first photodiode and a second photodiode. The deep trench isolations separate the first photodiode and the second photodiode, in which a pixel dimension is determined by a distance between two adjacent deep trench isolations. The first color filter is disposed on the first photodiode and the second photodiode. The first deflector is disposed on the first color filter. The covering layer covers and surrounds the first deflector. A refractive index of the covering layer is greater than a refractive index of the first deflector, and a difference value between the refractive index of the covering layer and the refractive index of the first deflector is in a range from 0.15 to 0.6.