Solid-State Imaging Device Shallow Pixel Isolation
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Solution Overview
Problem
Solid-state imaging devices face issues with white spots due to stress and damage from deep STI isolation regions, which affect photodiode performance, and the formation of polysilicon residues during gate electrode fabrication, leading to short circuits and reduced sensitivity.
Innovation Solution
The implementation of shallower second isolation regions in the pixel section with the same surface height as the first isolation regions in the peripheral circuit section, reducing stress and damage to photodiodes and minimizing processing steps, while ensuring no electrode material remains on sidewalls during gate electrode fabrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If deep STI isolation regions are formed in the pixel section, then isolation effectiveness is improved, but stress and damage to photodiodes increases causing white spots
Solution Approach 1:
The patent applies different STI depths to different sections: deep STI in the peripheral circuit section for effective isolation, and shallow STI in the pixel section to minimize stress on photodiodes while maintaining sufficient isolation. This local differentiation resolves the contradiction between isolation effectiveness and photodiode protection.
2Reliability
If high insulator layers are formed in the pixel section, then isolation is improved, but polysilicon residues form on sidewalls during gate electrode fabrication
Solution Approach 1:
The patent forms low insulator layers in the pixel section and high insulator layers in the peripheral circuit section. The low insulator layers have sufficient height for isolation but do not create prominent sidewalls that would trap polysilicon residues during gate electrode fabrication, thus resolving the contradiction between isolation effectiveness and manufacturing precision.
3Adaptability or versatility
If separate formation processes are used for different STI structures, then customization for each section is improved, but number of production processes increases
Solution Approach 1:
The patent merges the formation of different STI structures into a single integrated process sequence. By forming shallow STI in the pixel section and deep STI in the peripheral circuit section within the same process flow, the patent achieves section-specific customization without increasing the total number of production processes, thus resolving the contradiction between adaptability and productivity.
Data Source
AI summary
Disclosed is a solid-state imaging device which includes a pixel section, a peripheral circuit section, a first isolation region formed with a STI structure on a semiconductor substrate in the peripheral circuit section, and a second isolation region formed with the STI structure on the semiconductor substrate in the pixel section. The portion of the second isolation region buried into the semiconductor substrate is shallower than the portion buried into the semiconductor substrate of the first isolation region, and the height of the upper face of the second isolation region is equal to that of the first isolation region. A method of producing the solid-state imaging device and an electronic device provided with the solid-state imaging devices are also disclosed.