Image Sensor Pixel Reflective Structure for Crosstalk Reduction
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Solution Overview
Problem
Current image sensing devices face challenges in achieving high light reception efficiency and reducing optical crosstalk between pixels, particularly in edge regions of the pixel array where light incidence angles are oblique, leading to decreased efficiency and increased crosstalk.
Innovation Solution
The implementation of a pixel structure that includes a semiconductor region with a photoelectric conversion element, a microlens, and a reflective structure. The reflective structure covers a portion of the microlens to reflect incident light away from the pixel while exposing another portion to receive light, enhancing light reception efficiency and reducing crosstalk by strategically positioning the reflective structure to block light from entering adjacent pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional pixel structure is used in edge regions, then the device complexity is low, but the light reception efficiency decreases due to oblique light incidence
Solution Approach 1:
The patent applies different structures to different regions of the pixel array. Specifically, the edge pixels (fifth pixels) have a different structure from the central pixels (first to fourth pixels), with the edge pixels including a reflective structure and having a different microlens configuration to handle oblique light incidence, while central pixels use a simpler structure optimized for near-normal incidence.
Solution Approach 2:
The pixel array is segmented into different regions (central region with first to fourth pixels and edge region with fifth pixels) that have different optical structures. This segmentation allows each region to be optimized for its specific light incidence characteristics, improving overall light reception efficiency across the entire array.
2Productivity
If the microlens covers the entire semiconductor region, then light gathering is maximized, but optical crosstalk between adjacent pixels increases
Solution Approach 1:
The microlens is configured with different coverage areas for different pixel types. The microlens of the edge pixel (fifth pixel) covers only a portion of the semiconductor region rather than the entire region, creating a local quality difference that reduces optical crosstalk while maintaining sufficient light gathering for that pixel type.
Solution Approach 2:
The reflective structure, which initially might seem to block light, is actually used to redirect oblique light that would otherwise cause crosstalk into a path that directs it toward the correct pixel's semiconductor region, converting a potential harmful effect into a beneficial light directing mechanism.
3Object-generated harmful factors
If no reflective structure is used, then the pixel structure is simpler, but oblique light in edge regions causes increased optical crosstalk
Solution Approach 1:
The reflective structure is applied selectively only to edge pixels (fifth pixels) that are susceptible to oblique light incidence and resulting crosstalk, rather than being applied uniformly to all pixels. This localized application reduces overall device complexity while effectively addressing the crosstalk problem in the specific region where it occurs.
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
This configuration significantly improves light reception efficiency and reduces optical crosstalk between pixels, optimizing image sensing performance by ensuring that more incident light is directed to the semiconductor region while minimizing interference from adjacent pixels.
Implementation Method 1
a photoelectric conversion element configured to generate photocharges corresponding to intensity of incident light
Implementation Method 2
a microlens disposed over the semiconductor region to direct incident light to the semiconductor region
Implementation Method 3
a reflective structure disposed to cover a portion of the microlens to reflect incident light away from the pixel while exposing another portion to receive light
Data Source
AI summary
An image sensing device includes a lens module to converge incident light from a scene; and a pixel array located relative to the lens module to receive the converged incident light from the lens module and structured to include a plurality of pixels, each of which is structured to detect the converged incident light carrying image information of the scene, wherein the plurality of pixels in the pixel array includes a first pixel in an edge region of the pixel array, the edge region being spaced apart from an optical axis of the lens module by a predetermined distance, and wherein the first pixel includes: a semiconductor region including a photoelectric conversion element configured to generate photocharge corresponding to an intensity of the incident light detected at the fist pixel; a microlens disposed over the semiconductor region; and a reflective structure disposed to cover a portion of the first pixel.