Image Sensor Dummy Isolation Film for Patterning Defect Prevention
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Solution Overview
Problem
The challenge in manufacturing image sensors is the difficulty in preventing defects during the patterning process due to differences in surface levels between the pixel and pad regions, which can lead to patterning failures, especially when the integration level of the image sensor increases and the size of photodiode regions decreases.
Innovation Solution
The implementation of a semiconductor substrate with a pixel element isolation film and a dummy element isolation film, where the dummy element isolation film has a wider width and greater height than the pixel element isolation film, acts as an etch stopping film to prevent dishing and ensure a flat top surface level, thereby preventing patterning failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the degree of integration of the image sensor increases, then the size of each photodiode region decreases, but process difficulty increases
Solution Approach 1:
The dummy element isolation film is formed in advance before the planarization process to prevent dishing from occurring during subsequent manufacturing steps. This preliminary structural preparation ensures that when photodiode regions are miniaturized for higher integration, the patterning process remains stable and defect-free
2Manufacturing precision
If there is a difference between upper surface levels of pixel region and pad region, then planarization is required, but patterning defects occur
Solution Approach 1:
The dummy element isolation film serves as an intermediary structure between the pixel region and pad region. It has a first end that is substantially coplanar with the first surface and a second end that extends to a higher level, acting as a transition zone that prevents dishing during planarization while maintaining reliable patterning across the entire substrate
3Stability of the object's composition
If dummy element isolation film has greater width and height, then dishing is prevented, but device complexity increases
Solution Approach 1:
The dummy element isolation film is strategically positioned only in regions where dishing would occur during planarization, such as between active pixels and in peripheral areas. The film's width and height are locally increased only where needed to maintain top surface flatness, while the overall device structure remains relatively simple
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 solution effectively prevents patterning failures by maintaining a relatively flat top surface level across the active pixel, dummy pixel, and pad regions, ensuring consistent processing and reducing defects in subsequent patterning steps.
Implementation Method 1
the dummy element isolation film acts as an etch stopping film to prevent dishing and ensure a flat top surface level
Data Source
AI summary
An image sensor includes a semiconductor substrate having a first surface and a second surface, a pixel element isolation film extending through an interior of the semiconductor substrate and defining a plurality of active pixels in the semiconductor substrate, and a dummy element isolation film extending through the interior of the semiconductor substrate and extending along at least one side of the active pixels in a plan view and defining a plurality of dummy pixels in the semiconductor substrate. The pixel element isolation film may have a first end that is substantially coplanar with the first surface and has a first width in a first direction parallel to the first surface, and the dummy element isolation film has a first end that is substantially coplanar with the first surface and has a second width that is greater than the first width of the pixel element isolation film.