Solid-State Imaging Device Counter Dope Region Crosstalk Suppression
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Solution Overview
Problem
In solid-state imaging devices, the microfabrication process leads to increased crosstalk between pixels due to the resist approximation effect, which causes impurity concentration variations and deteriorates the transfer characteristics of transfer transistors, especially as pixel density increases.
Innovation Solution
A solid-state imaging device design that includes a first semiconductor region with a deep isolating region and a counter dope region of specific impurity concentrations, along with a buried channel region and a second isolating region, to manage impurity distribution and prevent potential barriers, using different photomasks for formation to maintain transistor performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an isolating region is formed in a deep region below a semiconductor region to suppress crosstalk between pixels, then crosstalk suppression is improved, but impurity concentration rises in the semiconductor region over the isolating region due to the resist approximation effect, causing threshold value variation and transfer characteristic deterioration
Solution Approach 1:
The patent applies local quality by creating a counter dope region with specific impurity concentration distribution only in the necessary area above the isolating region. This region has higher impurity concentration localized exactly where the resist approximation effect occurs, counteracting the harmful impurity diffusion without affecting other regions. The counter dope region is formed with a gradient concentration profile that matches the resist approximation effect distribution, thereby suppressing threshold value variation and maintaining transfer characteristics while preserving the crosstalk suppression function of the deep isolating region.
2Productivity
If pixel size is reduced to increase pixel density, then productivity is improved, but the area of the semiconductor region for transistor arrangement decreases, making the resist approximation effect more significant and transfer characteristics worse
Solution Approach 1:
The patent applies parameter changes by modifying the impurity concentration distribution through the counter dope region. As pixel size decreases and the resist approximation effect becomes more significant, the counter dope region compensates by providing a tailored impurity concentration profile that counteracts the harmful effects. The impurity concentration in the counter dope region is specifically designed to offset the resist approximation effect, thereby maintaining transfer transistor threshold values and transfer characteristics even at higher pixel densities where the semiconductor region area is reduced.
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 design effectively suppresses crosstalk between pixels and maintains the transfer characteristics of transfer transistors, ensuring reliable signal transfer and image quality even at high pixel densities.
Implementation Method 1
a photoelectric conversion unit configured to accumulate electric charges generated by photoelectrically converting incident light
Data Source
AI summary
A solid-state imaging device has: a counter dope region of a first conductivity type which is formed so as to surround a drain region of a transfer transistor of the solid-state imaging device and in which impurity concentration of the first conductivity type is lower than that of the drain region; and an isolating region of a second conductivity type which is formed in a deep region below channel regions of a plurality of transistors and in which impurity concentration of the second conductivity type is higher than that of a well region, wherein a depth position of a lower surface of the counter dope region is deeper than a depth position of a lower surface of a buried channel region.