Reduced Field Photomask for Semiconductor Yield
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Solution Overview
Problem
Conventional photomasks have inefficiencies in mask cycle time, inspection time, and yield due to their large full field sizes, which are not optimized for limited run designs like prototypes, and result in increased costs and defect densities.
Innovation Solution
A photomask with a reduced field size, defined by a width and length within specific ranges, is used to pattern semiconductor devices, allowing for a primary patterned area that avoids defects and reduces the overall process time and cost by utilizing a smaller portion of the full field, potentially filled with dummy patterns to mitigate loading effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a conventional photomask with large full field size is used, then the photomask can cover the entire wafer area, but the mask cycle time and inspection time increase significantly
Solution Approach 1:
The photomask is segmented into multiple independent fields (first field and second field) instead of using a single large field. Each field can be independently exposed and processed, allowing parallel processing that reduces overall mask cycle time while maintaining full wafer coverage capability
Solution Approach 2:
The system dynamically selects and switches between different fields (first field for initial exposure, second field for additional patterns) based on the specific manufacturing needs, allowing flexible adaptation to different design requirements and reducing unnecessary processing time
2Area of stationary object
If a conventional photomask with large full field size is used, then the photomask can cover the entire wafer area, but the inspection time increases significantly
Solution Approach 1:
The large full field area is divided into multiple smaller independent fields, which can be inspected separately and more efficiently. This segmentation reduces the time required for defect detection and inspection while maintaining the ability to cover the entire wafer area through multiple exposures
Solution Approach 2:
The system uses only the necessary portion of the full field area for each specific exposure step, rather than inspecting and processing the entire large field at once. This partial action approach reduces inspection time while still achieving complete wafer coverage through multiple targeted exposures
3Area of stationary object
If a conventional photomask with large full field size is used, then the photomask can cover the entire wafer area, but the defect density increases
Solution Approach 1:
Dividing the large full field into multiple smaller independent fields reduces the probability of defects in any single field. Statistical analysis shows that smaller fields have lower defect densities, and the segmentation allows for better defect isolation and management across the wafer
Solution Approach 2:
Each field can be optimized with local quality controls specific to its requirements. The first field and second field can have different pattern densities, exposure parameters, and defect tolerance levels, allowing tailored optimization that reduces overall defect density while maintaining full area coverage
4Loss of time
If a reduced field photomask is used, then the mask cycle time and inspection time are reduced, but the field area covered is smaller
Solution Approach 1:
Multiple reduced fields (first field and second field) are merged through sequential exposure to achieve the equivalent coverage of a large full field photomask. This combining approach maintains the time and inspection benefits of smaller fields while achieving the area coverage of conventional photomasks
Solution Approach 2:
The exposure process continues seamlessly across multiple fields, with the second field exposure following the first field exposure without interruption. This continuous action ensures complete wafer coverage is achieved while maintaining the efficiency benefits of reduced field sizes throughout the process
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
The reduced field photomask significantly reduces mask cycle time, inspection time, and defect density, leading to improved yield and cost efficiency, particularly suitable for low-volume device production, and allows for the use of less expensive mask types, while maintaining tight control over critical dimensions.
Implementation Method 1
transmitting the generated energy through the reduced field area of the photomask
Implementation Method 2
one or more layers disposed over the substrate, the one or more layers defining a full field area and a reduced field area with a primary pattern
Data Source
AI summary
A photomask used for manufacturing a semiconductor device includes a substrate; and one or more layers disposed over the substrate, the one or more layers defining a full field area and a reduced field area with a primary pattern being formed in the reduced field area, wherein the full field area is defined by a width of at least 90 mm and a length of at least 100 mm, and the reduced field area is defined by a width within the range of approximately 20-80 mm and a length within the range of approximately 20-80 mm, a center point of the primary patterned area being spaced a predetermined distance from a center point of the photomask so that the primary patterned area avoids photomask defects.