Photomask Dummy Pattern for Light Scattering Control
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Solution Overview
Problem
Conventional photolithography processes experience dimensional biases in pattern images due to light scattering, particularly when transferring patterns of different densities, making it challenging to maintain precise critical dimensions as semiconductor devices shrink in size.
Innovation Solution
Incorporating a dummy pattern around the second pattern in the photomask with a lower pattern density and smaller line width and inter-line pitch to minimize light scattering, allowing it to not be imaged during exposure, thereby maintaining accurate transfer of the first and second patterns without the need for compensation processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional photomask patterns are used without dummy patterns, then the manufacturing process is simple, but dimensional biases occur in pattern images due to light scattering
Solution Approach 1:
A dummy pattern is introduced as an intermediary element between the first and second patterns. This dummy pattern acts as a mediator to control light scattering, preventing direct light interaction between the two patterns and thereby eliminating dimensional biases in the transferred images without requiring complex compensation processes
Solution Approach 2:
The dummy pattern is designed with specific parameters (line width and inter-line pitch) that are smaller than those of the main patterns. By changing these dimensional parameters, the dummy pattern allows light transmission in small amounts and prevents imaging, thereby controlling light scattering effects to improve dimensional accuracy
2Manufacturing precision
If compensation processes are used to correct dimensional biases, then pattern accuracy improves, but manufacturing time and costs increase
Solution Approach 1:
The dummy pattern is pre-configured in the photomask design to proactively prevent light scattering issues before exposure. This preliminary structural arrangement eliminates the need for post-exposure compensation processes, thereby maintaining high dimensional accuracy while improving manufacturing efficiency by removing additional processing steps
3Ease of manufacture
If the dummy pattern has larger line width and inter-line pitch, then it is easier to manufacture, but it scatters more light and creates image bias
Solution Approach 1:
The dummy pattern is designed with optimized parameters where line width and inter-line pitch are intentionally kept smaller than the main patterns. This parameter selection achieves the right balance: small enough to minimize light scattering and prevent imaging, but large enough to be manufacturable with standard photolithography processes
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 prevents image bias and maintains consistent critical dimensions of pattern images on the photoresist layer, reducing manufacturing time and costs by eliminating the need for conventional compensation processes.
Implementation Method 1
The dummy pattern is configured to allow light transmission in a substantially small amount so that the dummy pattern is not imaged while the first and second patterns are transferred on the photoresist layer during exposure
Implementation Method 2
The opening area 130 may cause light scattering around the second pattern area 120 of the photomask 100, which may result in the accumulation of light energy in the underlying photoresist layer
Implementation Method 3
When light strikes fine particles, the particles absorb light energy. A part of the light energy is absorbed and becomes an internal energy
Data Source
AI summary
In a photolithography process, a photoresist layer is formed on a substrate. A photomask is aligned over the substrate to transfer pattern images defined in the photomask on the substrate. The photomask includes first and second patterns of different light transmission rates, and a dummy pattern surrounding the second pattern having a light transmission rate lower than that of the first pattern. The substrate is exposed to a light radiation through the photomask. The photoresist layer then is developed to form the pattern images. The dummy pattern is dimensionally configured to allow light transmission, but in a substantially amount so that the dummy pattern is not imaged during exposure.