Two-Layer Poly-Silicon Electrodes for CCD Transfer Efficiency
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Solution Overview
Problem
High pixel density in solid-state imaging apparatuses leads to decreased transfer efficiency due to increased number of transfer stages, and shortening the distance between transfer electrodes is limited by lithography constraints, making it difficult to achieve high transfer efficiency while maintaining efficient breakdown voltage.
Innovation Solution
The apparatus employs a two or more layered structure for transfer electrodes in both vertical and horizontal CCDs, with shorter distances between adjacent electrodes in the horizontal transfer CCD and longer distances in the vertical transfer CCD, allowing for controlled oxide film thickness to optimize transfer efficiency and breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of pixels is increased to achieve high pixel density, then the imaging capability is improved, but the number of transfer stages increases causing deterioration of transfer efficiency
Solution Approach 1:
The patent transitions from a single-layer transfer electrode structure to a two-layer overlap structure, adding a vertical dimension to the electrode arrangement. This allows charge transfer across layers while maintaining efficient electric field coupling, thereby improving transfer efficiency despite increased pixel density and transfer stages.
Solution Approach 2:
The patent changes the structural parameters of transfer electrodes by creating overlapping electrodes in different layers with controlled spacing. By adjusting the overlap distance and layer separation, the electric field distribution is optimized to maintain high transfer efficiency even with increased number of transfer stages required for high pixel density.
2Reliability
If the distance between transfer electrodes is shortened to increase transfer efficiency, then the transfer efficiency is improved, but the distance cannot be reduced below the minimum length determined by lithography
Solution Approach 1:
By moving from a single-plane electrode arrangement to a three-dimensional overlapping structure, the patent achieves effective electrode spacing reduction in the horizontal plane while maintaining adequate vertical separation. This allows transfer efficiency improvement without violating lithography minimum distance constraints in the fabrication plane.
Solution Approach 2:
The transfer electrode function is segmented into multiple layers, with each layer containing partial electrode structures that overlap with adjacent layers. This segmentation allows the effective transfer distance to be reduced through vertical stacking while each individual layer can be fabricated within lithography capabilities.
3Reliability
If the distance between transfer electrodes is shortened to increase transfer efficiency, then the transfer efficiency is improved, but the breakdown voltage becomes insufficient
Solution Approach 1:
The patent resolves the conflict between short electrode spacing (for high transfer efficiency) and adequate breakdown voltage by introducing a vertical dimension. The overlapping electrodes are separated by a vertical insulating layer, allowing short horizontal spacing for efficient charge transfer while maintaining sufficient vertical distance for adequate breakdown voltage.
Solution Approach 2:
An insulating layer is introduced as an intermediary between the overlapping transfer electrodes in different layers. This intermediary structure enables the electrodes to be positioned close together horizontally for efficient charge transfer while the insulating layer provides the necessary electrical isolation to maintain adequate breakdown voltage.
4Reliability
If a two layered overlap poly-silicon structure is used to shorten distance between transfer electrodes, then the transfer efficiency is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The complex transfer electrode structure is segmented into two distinct layers, with each layer containing simplified electrode patterns. This segmentation allows each layer to be fabricated using standard processes, and the overall complex functionality is achieved through the combination and overlap of these simpler individual layers.
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 enhances transfer efficiency in horizontal CCDs and ensures efficient breakdown voltage in vertical CCDs, enabling high pixel density imaging with reduced power consumption and improved image quality.
Implementation Method 1
the first layer poly-silicon electrodes 320 are formed on a gate insulation film 410 on the semiconductor substrate 310 and oxidized for forming first oxide films 420 to insulate between layers
Implementation Method 2
a photodiode region 350 aligned photodiodes which convert light into signal charge and accumulate the signal charge
Data Source
AI summary
The present invention aims to provide a solid-state apparatus and a manufacturing method thereof, the solid-state apparatus having both high transfer efficiency in a horizontal transfer CCD and efficient breakdown voltage in a vertical transfer CCD and including a semiconductor substrate 110, first layer poly-silicon electrodes 120 and second layer poly-silicon electrodes 130 which form two layered overlap poly-silicon electrodes, an embedded channel region 140 which is formed in a surface unit of the semiconductor substrate 110 and becomes a transfer path for signal charge, and a photodiode region where photodiodes are aligned two-dimensionally, the photodiodes converting light into signal charge and accumulating the signal charge, wherein an inter-electrode distance c in the horizontal transfer CCD is shorter than an inter-electrode distance a in the vertical transfer CCD.