Photoelectric Conversion Wiring Shield Layout Against FD Fluctuation
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Solution Overview
Problem
The existing photoelectric conversion apparatuses face a yield decrease due to potential fluctuations affecting the floating diffusion (FD) caused by conductive lines, which can lead to short circuits during the manufacturing process, especially when metal conductive lines are recessed or dished during planarization, resulting in reduced layout flexibility and increased risk of shorts.
Innovation Solution
A photoelectric conversion apparatus with a shielding portion made of metal, arranged in the second wiring layer to overlap the first conductive line, and a second conductive line in the third wiring layer, both with insulation portions to reduce capacitive coupling and potential fluctuations, while maintaining layout flexibility and preventing recess formation during chemical mechanical polishing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal conductive line is used as a shield to reduce potential fluctuation influence on the floating diffusion, then the shielding effectiveness is improved, but the metal conductive line portion may be recessed by scratch or dishing during planarization process, causing short circuits and yield decrease
Solution Approach 1:
The shielding portion is divided into multiple segments separated by insulation portions, forming a pattern such as grid, mesh, or stripes. This segmentation prevents continuous metal surfaces that are prone to scratching and dishing during CMP, while maintaining shielding effectiveness through distributed capacitance coupling reduction.
Solution Approach 2:
Insulation portions are introduced between metal conductive lines to act as intermediaries. These insulation portions prevent direct contact and capacitance coupling between adjacent metal lines, reducing the risk of short circuits while maintaining the shielding function against potential fluctuations.
2Reliability
If metal conductive lines are used for shielding, then the shielding function is achieved, but the layout flexibility is reduced due to the risk of short circuits from recess formation
Solution Approach 1:
By segmenting the shielding structure into discrete metal portions separated by insulation, the design allows greater flexibility in routing and placement without the continuous metal path constraints. This enables better adaptation to various layout configurations while maintaining shielding effectiveness.
Solution Approach 2:
The insulation portions are strategically placed at specific locations where capacitance coupling is most problematic, allowing shielding to be optimized locally without requiring comprehensive metal coverage throughout the entire layout, thus improving overall layout flexibility.
3Reliability
If a continuous metal shielding structure is used, then the shielding effectiveness is maximized, but the risk of short circuits during damascene process increases due to recess filling
Solution Approach 1:
The continuous metal structure is segmented into discrete portions separated by insulation. This prevents the formation of large recesses that would be filled with metal during damascene, eliminating the root cause of short circuits while preserving the distributed shielding effect against potential fluctuations.
Solution Approach 2:
The insulation portions are extracted and placed between metal conductive lines to remove the problematic continuous metal structure. This extraction eliminates the capacitance coupling paths that lead to short circuits during subsequent processing while maintaining the essential shielding function.
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 reduces the influence of potential fluctuations on the FD, minimizing the risk of short circuits and yield decreases by incorporating insulation portions in the shielding pattern, thereby enhancing manufacturing yield and preventing recess formation during CMP processes.
Implementation Method 1
a shielding portion made of metal and arranged in the second wiring layer such that at least one portion of the shielding portion overlaps the first conductive line in a plan view
Implementation Method 2
a photoelectric conversion unit configured to generate a signal electric charge based on incident light
Data Source
AI summary
A photoelectric conversion apparatus includes a first conductive line that is arranged in a first wiring layer and connects a floating diffusion to a gate of an amplification transistor, a shielding portion that is made of metal and provided in a second wiring layer which is an upper layer of the first wiring layer such that at least one portion of the shielding portion overlaps the first conductive line in a plan view, and a second conductive line that is arranged on a third wiring layer which is an upper layer of the second wiring layer such that at least one portion of the second conductive line overlaps the first conductive line in the plan view. The shielding portion includes a plurality of insulation portions in the plan view.