Image Sensor Pixel Separation Layout to Prevent Leaning Defects
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Solution Overview
Problem
Current image sensors face challenges in preventing defects such as the leaning phenomenon of pixel separation patterns due to high aspect ratios, which can lead to image quality issues and increased complexity in fabrication processes.
Innovation Solution
The image sensor design incorporates a pixel separation pattern with a first separation pattern extending from one side and a second separation pattern overlapping it, along with a contact film that applies a ground or negative voltage to the filling film, and includes contact trenches that expose the separation patterns to facilitate electrical connection, thereby reducing aspect ratios and preventing defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single continuous separation pattern is used to separate pixel regions, then complete pixel separation is achieved, but the aspect ratio becomes high causing leaning phenomenon and fabrication defects
Solution Approach 1:
The continuous separation pattern is divided into multiple discrete segments (first separation pattern and second separation pattern) positioned at different depths. The first separation pattern is formed at a first depth from the first surface, and the second separation pattern is formed at a second depth from the second surface, with the second depth being greater than the first depth. This segmentation reduces the aspect ratio of each individual separation pattern while maintaining complete pixel separation when both patterns are combined.
Solution Approach 2:
The solution transitions from a single-plane separation approach to a multi-depth separation approach by forming separation patterns at different depths within the substrate. The first separation pattern extends from the first surface to the first depth, and the second separation pattern extends from the second surface to the second depth, utilizing the third dimension (depth) to distribute the separation function across multiple levels and reduce the aspect ratio of each pattern.
2Reliability
If contact trenches are formed to expose separation patterns for electrical connection, then proper electrical contact is achieved, but the fabrication process complexity increases
Solution Approach 1:
The contact trenches are formed to expose the separation patterns at appropriate depths before subsequent fabrication steps. The first contact trench exposes the first separation pattern, and the second contact trench exposes the second separation pattern, allowing electrical connections to be established at the correct positions and depths in advance of other processing steps, thereby simplifying the overall fabrication sequence.
Data Source
AI summary
An image sensor is provided. The image sensor includes a substrate including a first side on which light is incident and a second side opposite the first side; a first separation pattern extending from the second side, the first separation pattern being interposed between unit pixels in the substrate of a light-receiving region and a light-shielding region provided around the light-receiving region; a second separation pattern extending from the first side and overlapping the first separation pattern, the second separation pattern being provided in the substrate of the light-receiving region; and a contact film electrically connected to the first separation pattern, the contact film being provided in the substrate of the light-shielding region. A contact trench which extends from the first side is formed in the light-shielding region of the substrate and exposes the first separation pattern, and the contact film fills at least a part of the contact trench.