Zero-Gap Micro-Lens Array via Segmented Photolithography
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Solution Overview
Problem
Conventional methods for manufacturing micro-lenses in image sensors fail to produce zero-gap micro-lenses due to bridge formation between adjacent lenses, and existing solutions are costly and prone to process failures, requiring complex multi-step processes that still do not completely prevent bridge formation.
Innovation Solution
A method involving a semiconductor substrate with a planarization layer, where a first set of micro-lenses is formed using a chessboard photomask, hardened through surface treatment, and a second set is formed using the same photomask shifted by one pitch, eliminating bridge formation by protecting the first set from subsequent process influences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional photolithography process is used to form micro-lenses in array, then manufacturing process is simple, but bridge formation occurs between adjacent micro-lenses when gap is reduced
Solution Approach 1:
The manufacturing process is segmented into multiple sequential steps: forming first micro-lens blocks, performing surface treatment to create isolation layers, then forming second micro-lens blocks. This segmentation prevents bridge formation by isolating adjacent micro-lenses during the manufacturing process, allowing zero-gap micro-lenses to be formed without contamination or bridging issues.
Solution Approach 2:
Surface treatment is performed as a preliminary action between forming adjacent micro-lens blocks. This preliminary surface treatment creates an isolation layer on the first micro-lens blocks before the second micro-lens blocks are formed, preventing bridge formation in advance and ensuring clean separation between adjacent micro-lenses.
2Manufacturing precision
If checkerboard photomasks are used to form zero-gap micro-lenses, then manufacturing precision is improved, but cost and process complexity increase
Solution Approach 1:
Instead of using complex checkerboard photomasks, the invention segments the micro-lens array formation into multiple simple photolithography steps with standard photomasks. Each step forms a portion of the micro-lens array, and surface treatment creates isolation between them. This segmentation simplifies the photomask requirements while achieving the same zero-gap precision.
Solution Approach 2:
Surface treatment is introduced as an intermediary process between standard photolithography steps. This intermediary treatment creates isolation layers that enable precise positioning and zero-gap formation without requiring complex checkerboard photomasks, thereby reducing device complexity while maintaining manufacturing precision.
3Shape
If multiple baking processes are performed to form micro-lenses, then micro-lens shape is improved, but bridge formation occurs due to influence on previously formed micro-lenses
Solution Approach 1:
Surface treatment is performed as a preliminary action after forming each set of micro-lens blocks and before forming the next set. This preliminary surface treatment creates isolation layers that protect previously formed micro-lenses from influence during subsequent baking processes, preventing bridge formation while allowing proper micro-lens shape development.
Solution Approach 2:
Surface treatment provides preliminary anti-action by creating isolation layers that counteract the potential bridge formation effect. This preliminary protective action prevents the harmful influence from subsequent baking processes from affecting previously formed micro-lenses, ensuring reliable zero-gap micro-lens arrays.
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 simplifies the manufacturing process, reduces costs, and ensures the formation of a complete zero-gap micro-lenses array by hardening the first set of micro-lenses, preventing bridge formation and improving the surface profile and photosensitivity of image sensors.
Implementation Method 1
performing a first photolithography process to form a first set of micro-lens blocks on the planarization layer
Implementation Method 2
a baking process is performed to melt and re-shape the micro-lens blocks 32 and to form micro-lenses 36
Implementation Method 3
performing a first surface treatment to harden surfaces of the first set of micro-lenses
Data Source
AI summary
A method for manufacturing micro-lenses of image sensors includes providing a semiconductor substrate having at least a planarization layer, performing a first photolithography process to form a first set of micro-lens blocks on the planarization layer, performing a first baking process to form a first set of micro-lenses, performing a first surface treatment to harden surfaces of the first set of micro-lenses, performing a second photolithography to form a second set of micro-lens blocks on the planarization layer, and performing a second baking process to form a second set of micro-lenses.