Immersion Dry Lithography Exposure Sequence
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Solution Overview
Problem
Current photolithography techniques face challenges in achieving high image resolution and cost-effectiveness, particularly with the limitations of radiation wavelength and the need for multiple exposures in semiconductor fabrication, as further reducing wavelength is impractical and enhanced lithography methods like immersion lithography increase costs.
Innovation Solution
A method combining high-precision immersion lithography with low-precision dry lithography for multiple exposures, allowing for balanced cost and precision by using different sequences or tools, such as using 193 nm wavelength immersion lithography followed by 193 nm or 248 nm wavelength dry lithography, to enhance image resolution and reduce manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If radiation wavelength is reduced to improve image resolution, then image resolution is improved, but it becomes impractical to continue reducing wavelength below 193 nm due to absorption by projection lenses
Solution Approach 1:
The patent changes the parameter of the optical medium from air (refractive index ≈1.0) to liquid (refractive index >1.0), which increases the numerical aperture and improves image resolution without requiring further wavelength reduction. This parameter change allows the system to overcome the absorption limitation at wavelengths below 193 nm.
2Manufacturing precision
If immersion lithography is used to improve numerical aperture and image resolution, then image resolution is significantly enhanced, but manufacturing costs become undesirable due to multiple exposures required
Solution Approach 1:
The patent segments the lithography process into multiple exposures using different techniques (immersion lithography for critical features, dry lithography for less critical features). This allows the high cost of immersion lithography to be applied only where necessary, reducing overall manufacturing costs while maintaining high image resolution for critical dimensions.
Solution Approach 2:
The patent applies different lithography methods to different regions or features on the wafer based on their criticality. Immersion lithography is used for features requiring high precision, while dry lithography is used for less critical features, optimizing the balance between image resolution and manufacturing cost.
3Manufacturing precision
If multiple exposures are performed to achieve required critical dimension uniformity and endcap performance, then manufacturing precision is improved, but manufacturing costs increase
Solution Approach 1:
The patent segments the multiple exposure process into different types of exposures (immersion and dry) with different cost structures. By strategically assigning which features receive which type of exposure, the patent achieves required critical dimension uniformity while minimizing the number of expensive immersion exposures needed, thereby reducing overall manufacturing costs.
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 improves image resolution and reduces manufacturing costs by leveraging the precision benefits of immersion lithography and the cost-effectiveness of dry lithography, making it suitable for fabricating semiconductor devices with feature sizes smaller than 56 nm.
Implementation Method 1
Since water has a refractive index of 1.4, the resulting numerical aperture of the optical system is increased by a factor of 1.4. Accordingly, image resolution may be significantly enhanced.
Data Source
AI summary
A method for producing a pattern on a substrate includes providing at least one exposure of the pattern onto a layer of the substrate by a higher-precision lithography mechanism and providing at least one exposure of the pattern onto a layer of the substrate by a lower-precision lithography mechanism. The exposures can be done in either order, and additional exposures can be included. The higher-precision lithography mechanism can be immersion lithography and the lower-precision lithography mechanism can be dry lithography.