Solid-State Image Sensor Light Shielding Segmentation
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Solution Overview
Problem
Solid-state image sensors face challenges in sensitivity due to light shielding layers that block light from reaching depletion layers, leading to reduced sensitivity and potential crosstalk issues in scanners and multifunction devices.
Innovation Solution
A solid-state image sensor design featuring a light shielding layer with specific overlapping portions and impurity regions, where the length of the light shielding layer's second portion is smaller than the first portion, allowing more light to reach the depletion layers and improving sensitivity while reducing crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a light shielding layer is placed to completely cover the first impurity region for electrical isolation, then crosstalk between adjacent pixels is reduced, but sensitivity decreases because light cannot reach the depletion layer
Solution Approach 1:
The light shielding layer is segmented into multiple portions: a first portion that overlaps the first impurity region for electrical isolation, and a second portion that overlaps only the first portion of the first impurity region (not the second impurity regions) to allow light passage. This segmentation enables simultaneous achievement of electrical isolation and light transmission.
Solution Approach 2:
Different regions of the light shielding layer have different properties: the first portion provides electrical isolation (opaque to light), while the second portion allows light transmission. This local differentiation of shielding properties enables the structure to simultaneously achieve crosstalk reduction and sensitivity maintenance.
2Reliability
If the light shielding layer completely overlaps the first impurity region, then electrical isolation is improved, but the amount of light reaching depletion layers decreases
Solution Approach 1:
The light shielding layer is divided into functional segments: the first portion provides complete electrical isolation by overlapping the entire first impurity region, while the second portion is strategically positioned to overlap only the first portion (not extending over the second impurity regions), thereby allowing light to reach the depletion layers.
Solution Approach 2:
The light shielding layer applies partial shielding action - it provides complete electrical isolation where needed (first portion overlap) but intentionally leaves gaps (second portion limited length) to allow partial light transmission, achieving the minimum necessary shielding rather than complete coverage.
3Reliability
If the light shielding layer extends fully over the first impurity region, then carrier isolation is improved, but parasitic capacitance increases
Solution Approach 1:
The light shielding layer is segmented such that the second portion has a limited length in the first direction that is smaller than the length of the first portion. This segmentation reduces the overlapping area between the light shielding layer and the first impurity region, thereby reducing parasitic capacitance while maintaining carrier isolation functionality.
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 design enhances sensitivity by increasing carrier accumulation in depletion layers, reduces crosstalk, simplifies the sensor structure, and minimizes parasitic capacitance, leading to faster scanning and improved image quality.
Implementation Method 1
Carriers that have undergone photoelectric conversion can be accumulated in the depletion layer
Data Source
AI summary
A solid-state image sensor including: a first impurity region of a first conductivity type; a plurality of second impurity regions of a second conductivity type disposed in the first impurity region and arranged in a first direction; and a light shielding layer that overlaps the first impurity region and does not overlap the second impurity regions in a plan view, wherein the first impurity region has a first portion between adjacent ones of the second impurity regions, the light shielding layer has a second portion that overlaps the first portion in a plan view, and a length of the second portion in the first direction is smaller than a length of the first portion in the first direction.