Stacked Image Sensor Layout for Accurate Optical Black Reference
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing photoelectric conversion apparatuses face issues with excess charge mixing in the optical black region, leading to inaccurate black level reference signals, particularly in laminated configurations where peripheral circuits are not mounted, affecting the detection of black level reference values.
Innovation Solution
Incorporating a drain portion in the outer periphery region to drain excess charges, along with a light-blocking layer that shields the well region and pad portions, and using a separation region to prevent short-circuiting, ensuring accurate detection of black level reference values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If OB pixels are placed in the end portion of the substrate, then the structure is simplified and manufacturing is easier, but signal charges generated in the periphery of the OB region are mixed in the OB region causing black level reference signals to fluctuate
Solution Approach 1:
A light-blocking layer is introduced as an intermediary element between the effective pixel region and the OB region. This light-blocking layer prevents signal charges generated in the periphery of the OB region from being mixed into the OB region, thereby maintaining the accuracy of black level reference signals while allowing OB pixels to be positioned at the end portion of the substrate for manufacturing simplicity.
2Reliability
If charge draining pixels are disposed between the effective pixel region and OB region, then signal charges leaking from the effective pixel region are drained, but signal charges generated in the periphery of the OB region still mix in the OB region
Solution Approach 1:
The light-blocking layer serves as a mediator that addresses the limitation of charge draining pixels. While charge draining pixels handle signal charges leaking from the effective pixel region, the light-blocking layer additionally prevents signal charges generated in the periphery of the OB region from entering the OB region, thereby ensuring black level reference signal accuracy.
Solution Approach 2:
The patent segments the photoelectric conversion apparatus into distinct functional regions: an effective pixel region for image capture, an OB region for black level reference, and a light-blocking layer separating them. This segmentation allows each region to perform its specific function independently, preventing charge mixing while maintaining overall system reliability.
3Device complexity
If the periphery of the OB region is used for signal processing circuits, then device integration is improved, but excess charge generation in the periphery mixes in the OB region affecting black level detection
Solution Approach 1:
The light-blocking layer acts as a protective intermediary that allows signal processing circuits to be integrated in the periphery of the OB region without compromising black level detection accuracy. By blocking light from reaching the periphery region where circuits are located, it prevents excess charge generation that would otherwise mix into the OB region.
Solution Approach 2:
The patent resolves the spatial conflict between circuit integration and OB region purity by utilizing the vertical dimension. The light-blocking layer is positioned above or below the periphery region in the vertical stacking direction, allowing circuits to occupy the periphery area while the light-blocking layer prevents charge mixing from that region into the OB region.
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 prevents excess charge mixing in the optical black region, enabling precise detection of black level reference signals and improving the accuracy of pixel values in laminated photoelectric conversion apparatuses.
Implementation Method 1
a light-blocking layer that shields the well region and pad portions
Implementation Method 2
Inclining a drain portion in the outer periphery region to drain excess charges
Implementation Method 3
each including a plurality of photoelectric conversion units
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A photoelectric conversion apparatus includes a first substrate having a first semiconductor device layer including a plurality of photoelectric conversion units and a well, and a second substrate having a second semiconductor device layer including a circuit configured to process signals obtained by the plurality of photoelectric conversion units, wherein the first and second substrates are laminated together, wherein the first semiconductor device layer includes an effective pixel region, an optical black pixel region, and an outer periphery region, wherein, in a planar view, a light-blocking layer overlaps the optical black pixel region, wherein the outer periphery region has a charge draining region including a semiconductor region of the same conductivity type as a signal charge, and wherein a fixed potential is supplied to the charge draining region.