Photoelectric Conversion Isolation Structure for Fine Pixel Sensitivity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The miniaturization of photoelectric conversion devices poses challenges in achieving a fine isolation structure between elements while maintaining effective isolation and maximizing light-receiving areas, as the aspect ratio of grooves increases, making it difficult to achieve both fine widths and sufficient depth for efficient light detection.
Innovation Solution
The implementation of first and second isolation portions extending from opposite planes of a semiconductor layer, with specific lengths and materials, such as borosilicate glass and polysilicon, to create a fine isolation structure that allows for effective electrical isolation and increased light-receiving areas, while also serving as etching stoppers during manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pixel size is miniaturized to increase the number of photoelectric conversion elements, then the integration density is improved, but the aspect ratio of isolation grooves increases making it difficult to achieve both fine widths and sufficient depth
Solution Approach 1:
The isolation structure is divided into multiple segments: a first isolation portion extending from the first surface and a second isolation portion extending from the second surface. These segments work together to provide complete isolation while allowing each segment to be formed with more manageable dimensions, avoiding the need for a single deep groove that would be difficult to manufacture in miniaturized pixels.
Solution Approach 2:
The isolation approach transitions from a single-dimensional deep groove to a two-dimensional approach by forming isolation portions from both the first surface and the second surface of the semiconductor substrate. This dimensional change allows the isolation structure to achieve sufficient depth while maintaining fine width control in each individual isolation portion.
2Area of stationary object
If the isolation groove width is reduced to increase light-receiving area, then the light-receiving area is improved, but the isolation performance between adjacent elements deteriorates
Solution Approach 1:
The isolation function is segmented between multiple isolation portions formed from opposite surfaces. Each isolation portion can be narrower while collectively providing sufficient isolation, as the combined effect of multiple segments achieves the required electrical isolation between adjacent photoelectric conversion elements.
Solution Approach 2:
Isolation is achieved by approaching from two opposite surfaces rather than one, allowing the isolation portions to meet or overlap in the middle. This enables the use of narrower isolation portions that maximize light-receiving area while maintaining effective isolation through the combined depth from both surfaces.
3Reliability
If the isolation groove depth is increased to improve isolation performance, then the isolation performance is improved, but the manufacturing complexity increases due to higher aspect ratio
Solution Approach 1:
The deep isolation structure is segmented into two shallower portions formed from opposite surfaces. Each portion has a lower aspect ratio that is easier to manufacture with standard etching processes, while the combined structure achieves the required total depth and isolation performance.
Solution Approach 2:
The manufacturing approach changes from forming one deep groove to forming two shallower grooves from opposite surfaces. This dimensional approach reduces the aspect ratio of individual etching operations, simplifying the manufacturing process while achieving the same total isolation depth.
4Ease of manufacture
If the isolation portion material is optimized for etching stopper function, then the manufacturing ease is improved, but the light-receiving area may be reduced due to material absorption
Solution Approach 1:
Different materials are used in different regions: borosilicate glass is used in the first isolation portion where etching stopper function is critical, while polysilicon is used in the second isolation portion where light absorption is less problematic. This local optimization allows each region to have properties suited to its specific function.
Solution Approach 2:
The isolation structure uses a composite of different materials (borosilicate glass and polysilicon) in different portions. This composite approach allows the structure to simultaneously achieve etching stopper function in critical regions while minimizing light absorption in regions where light reception is important.
Data Source
AI summary
A photoelectric conversion device has an isolation structure. First and second isolation portions are provided between first and second photoelectric conversion elements. The first isolation portion extends from a first plane of a semiconductor layer to a position corresponding to at least a quarter of a length from the first plane to a second plane of the semiconductor layer. The second isolation portion extends from the second plane of the semiconductor layer to a position corresponding to at least a quarter of the length from the first plane to the second plane.