Tapered Insulator Alignment for Back-Side Illumination Sensors
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Solution Overview
Problem
The existing alignment marks in back-side illumination (BSI) sensors, as described in Japanese Patent Application Publication No. 2011-114325, can deteriorate the manufacturing yield and quality due to misalignment errors between the upper and lower insulator portions, leading to inaccurate alignment and reduced overlay accuracy during the fabrication process.
Innovation Solution
A photoelectric converting device with a semiconductor layer featuring a tapered upper insulator portion and a lower insulator portion, where the maximum width of the upper insulator portion is larger than the lower insulator portion by at least twice the alignment error, ensuring accurate alignment even if misalignment occurs, and reducing stress around the electrode-pad formation area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional alignment mark with two insulator portions is used in BSI sensors, then the structure provides protection against short circuits and contamination, but misalignment errors between the upper and lower insulator portions deteriorate manufacturing yield and quality
Solution Approach 1:
The patent extracts the alignment function from the insulator portions by introducing a separate dedicated alignment mark structure. This separates the protective function of the insulators from the alignment function, allowing each to be optimized independently without interfering with each other's performance
Solution Approach 2:
The patent introduces a separate alignment mark as an intermediary element that facilitates precise alignment during manufacturing. This alignment mark acts as a mediator between the insulator portions and the positioning system, enabling accurate placement without requiring the insulator portions themselves to be perfectly aligned
2Manufacturing precision
If the maximum width of the upper insulator portion is made larger than the lower insulator portion by at least twice the alignment error, then alignment accuracy is improved, but device complexity increases
Solution Approach 1:
The patent applies asymmetry by making the maximum width of the upper insulator portion larger than that of the lower insulator portion. This asymmetric configuration creates a tapered structure that provides alignment tolerance, ensuring that even if misalignment occurs, the alignment accuracy is maintained within acceptable limits
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 prevents deterioration of alignment accuracy and improves the manufacturing yield and quality of BSI sensors by ensuring accurate positioning of color filters and microlenses, enhancing the effective aperture ratio and sensitivity while eliminating shading.
Implementation Method 1
The light-receiving part generates a signal charge by photoelectric conversion according to incident light
Data Source
AI summary
A photoelectric converting device including: a semiconductor layer with a front surface and a back surface, the semiconductor layer including a photoelectric conversion portion; a wire structure including an insulating film, the wire structure being disposed on the front surface of the semiconductor layer; a first insulator portion disposed in a trench provided in the semiconductor layer; and a second insulator portion disposed between the first insulator portion and the insulating film, wherein the first insulator portion has a maximum width larger than a maximum width of the second insulator portion.