Back-Illumination Image Sensor Alignment Mark Formation
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Solution Overview
Problem
The existing manufacturing methods for back-side-illumination solid-state image sensors require multiple complex steps for forming alignment marks, including the use of multiple layers and extra processing steps, which increases costs and reduces efficiency.
Innovation Solution
A semiconductor device with a back-side-illumination structure that uses a single-layer trench processing mask to form an alignment mark inside the semiconductor layer, where the mark extends from the front main surface to the back main surface and is formed using a conductive or semiconductor film, potentially in the same layer as the gate electrode, to simplify the alignment process and reduce the number of steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple layers and extra processing steps are used to form alignment marks, then the alignment precision can be improved, but the manufacturing complexity and cost increase
Solution Approach 1:
The patent merges the alignment mark formation process with the existing gate electrode formation process. The same single-layer trench processing mask is used for both purposes, eliminating the need for separate multi-layer mask structures. This combining of functions reduces manufacturing complexity while maintaining alignment precision through the protruding portion design.
Solution Approach 2:
The single-layer trench processing mask serves multiple functions: it defines the gate electrode pattern and simultaneously creates the alignment mark with its protruding portion. This multi-functional approach eliminates the need for dedicated alignment mark formation steps, reducing overall process complexity while achieving both patterning and alignment objectives.
2Manufacturing precision
If multiple layers and extra processing steps are used to form alignment marks, then the alignment precision can be improved, but the manufacturing cost increases
Solution Approach 1:
The patent combines alignment mark formation with gate electrode formation into a single process step using the same trench processing mask. This eliminates the need for separate alignment mark formation steps and associated materials, directly reducing manufacturing cost while maintaining alignment precision through the integrated design.
Solution Approach 2:
The trench processing mask performs dual functions of defining the gate electrode and creating the alignment mark structure. This multi-functionality reduces the total number of processing steps and material consumption, leading to lower manufacturing costs compared to traditional separate alignment mark formation processes.
3Productivity
If a single-layer trench processing mask is used to form alignment marks, then the number of manufacturing steps is reduced, but the visual recognizability of the alignment mark may be compromised
Solution Approach 1:
The patent creates an asymmetric protruding portion on the alignment mark that extends beyond the gate electrode pattern. This asymmetric feature provides distinct visual recognition from the top surface, compensating for the single-layer simplicity. The protruding portion serves as a clear visual indicator for alignment verification while maintaining the simplified single-layer mask structure.
Solution Approach 2:
The alignment mark is extended into the third dimension by creating a protruding portion that rises from the substrate surface. This dimensional extension enhances visual recognizability without requiring additional mask layers, as the protrusion provides a clear topographic feature for alignment detection while maintaining single-layer mask simplicity.
4Productivity
If a single-layer trench processing mask is used to form alignment marks, then the manufacturing steps are reduced, but the alignment precision may be compromised
Solution Approach 1:
The asymmetric protruding portion design provides a clear reference feature for alignment that compensates for the single-layer mask simplicity. The protrusion creates a distinct visual and physical reference point that enables precise alignment verification without requiring complex multi-layer mask structures, maintaining alignment precision through geometric clarity.
Solution Approach 2:
By extending the alignment mark into the vertical dimension with a protruding portion, the patent creates a three-dimensional reference feature that enhances alignment precision. This dimensional extension provides a clear alignment reference that is easily detectable and measurable, compensating for the reduced complexity of the single-layer mask structure.
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 approach reduces the number of steps required for forming alignment marks, lowers manufacturing costs, and enhances the visual recognizability of the alignment mark, thereby improving the efficiency and cost-effectiveness of producing back-side-illumination solid-state image sensors.
Implementation Method 1
a light receiving element which performs photoelectric conversion on light incident from a back surface of the semiconductor substrate
Data Source
AI summary
Provided is a semiconductor device which allows an alignment mark used for the manufacturing of a solid-state image sensor (semiconductor device) having a back-side-illumination structure to be formed in a smaller number of steps. The semiconductor device includes a semiconductor layer having a first main surface and a second main surface opposing the first main surface, a plurality of photodiodes which are formed in the semiconductor layer and in each of which photoelectric conversion is performed, a light receiving lens disposed over the second main surface of the semiconductor layer to supply light to each of the photodiodes, and a mark for alignment formed inside the semiconductor layer. The mark for alignment is formed so as to extend from the first main surface toward the second main surface and have a protruding portion protruding from the second main surface in a direction toward where the light receiving lens is disposed.