Solid-State Imaging Pixel Impurity Barrier Blooming
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional solid-state imaging apparatuses with APS structure face issues of blooming and color mixing due to signal charge overflow, where miniaturization of pixels limits effective element isolation and photodiode sensitivity is compromised.
Innovation Solution
The implementation of a semiconductor structure with a P type well and element isolation diffusion layer, featuring a fifth semiconductor region with higher impurity concentration under the third semiconductor region, forming a potential barrier to suppress signal charge overflow and improve sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the element isolation diffusion layer is made wider to suppress blooming and color mixing, then the blooming and color mixing are suppressed, but the pixel area is reduced and miniaturization is limited
Solution Approach 1:
The invention applies different impurity concentrations at different locations within the element isolation diffusion layer. The fifth semiconductor region has a higher impurity concentration than the second semiconductor region, creating a localized high-concentration zone that enhances the blocking effect against signal charge overflow without requiring the entire isolation layer to be wider. This local quality enhancement allows effective blooming suppression with minimal impact on pixel area.
Solution Approach 2:
Instead of expanding the element isolation diffusion layer in the lateral dimension (width), the invention introduces a vertical dimension solution by forming the fifth semiconductor region at a deeper level beneath the third semiconductor region. This vertical stacking approach creates a three-dimensional impurity concentration distribution that blocks signal charge overflow paths without consuming lateral pixel area, thus resolving the contradiction between isolation effectiveness and pixel miniaturization.
2Measurement precision
If the P well is deeply formed to improve photodiode sensitivity, then the sensitivity is improved, but signal charges from deep photoelectric conversion are discharged to the N type silicon substrate causing blooming
Solution Approach 1:
The invention introduces the fourth and fifth semiconductor regions as intermediary structures between the deeply formed P well (second semiconductor region) and the N type silicon substrate. These intermediary regions, particularly the fifth semiconductor region with higher impurity concentration positioned beneath the third semiconductor region, act as a blocking barrier that prevents signal charges generated in deep photoelectric conversion from reaching the substrate, thus eliminating the blooming issue while maintaining deep P well sensitivity.
Solution Approach 2:
The fifth semiconductor region with higher impurity concentration is formed in advance beneath the third semiconductor region, creating a pre-established blocking barrier before signal charge generation and overflow occurs. This preliminary action ensures that even when the P well is deeply formed for high sensitivity, the pre-positioned high-concentration region effectively intercepts and blocks any signal charges that might otherwise discharge to the substrate, preventing blooming before it can occur.
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 effectively suppresses blooming and color mixing while enhancing the sensitivity of the photodiode, maintaining effective color reproduction even with smaller pixel pitches.
Implementation Method 1
a fifth semiconductor region of the second conductivity type, and of an impurity concentration higher than that of the second semiconductor region, to form an impurity concentration profile such that the impurity concentration gradually decreases toward a surface direction is arranged under the third semiconductor region
Implementation Method 2
a photoelectric converting portion for converting an incident light into signal charges
Data Source
AI summary
A solid-state imaging apparatus capable of suppressing blooming and color mixing includes a plurality of pixels, each including a photoelectric converting portion and a transferring portion for transferring signal electrons from the photoelectric converting portion, wherein a plurality of the photoelectric converting portions is formed in a first conductivity type well region formed on the semiconductor substrate; a second conductivity type first impurity region is arranged between the adjacent photoelectric converting portions; a first conductivity type second impurity region having an impurity concentration higher than that of the well region is arranged between the first impurity region and each of the photoelectric converting portions; and a first conductivity type third impurity region having an impurity concentration higher than that of the well region and decreasing from the semiconductor substrate toward the surface direction of the apparatus between the semiconductor substrate and the first impurity region.