Reticle Segmentation for Lithography Focus Control
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Solution Overview
Problem
Current lithographic techniques face challenges in focusing coarse wavelengths of light through finely patterned reticles, leading to reduced reticle size and die area, with solutions like 157 nm wavelength light or EUV light being impractical due to polarization-dependent refraction and diffraction issues.
Innovation Solution
The system optimizes reticle layout by placing fine-line-width patterns within a high-resolution region and coarser patterns outside, increasing coarseness with distance from the high-resolution area to compensate for focus loss, allowing larger chip fabrication without separate masks for dense cores and coarse wires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If coarse wavelengths of light (193 nm) are used for lithography, then manufacturing cost and availability are improved, but manufacturing precision deteriorates due to focusing difficulties through finely patterned reticles
Solution Approach 1:
The reticle is divided into multiple focus regions (first focus region with first numerical aperture and second focus region with second numerical aperture), allowing different portions of the reticle to be optimized for different pattern requirements. This segmentation enables the use of coarse wavelength light while maintaining precision for critical patterns.
Solution Approach 2:
Different numerical apertures are assigned to different focus regions based on local pattern requirements. The first focus region uses a first numerical aperture optimized for fine patterns, while the second focus region uses a second numerical aperture optimized for coarse patterns, thereby achieving local optimization of focus quality.
2Area of stationary object
If reticle size is increased to accommodate larger die areas, then chip size is improved, but manufacturing precision deteriorates due to increased aberrations and focus loss across the larger reticle area
Solution Approach 1:
The large reticle is segmented into multiple focus regions with different numerical apertures. By dividing the reticle area into zones optimized for different pattern densities, the system can maintain manufacturing precision across the entire large reticle area without suffering from uniform focus degradation.
Solution Approach 2:
Each focus region on the large reticle is assigned a local numerical aperture value appropriate for its specific pattern requirements. This local quality approach ensures that even as reticle area increases, each local region maintains optimal focus quality for its intended use.
3Manufacturing precision
If separate masks are used for dense cores and coarse wires, then manufacturing precision is improved, but device complexity and process steps increase
Solution Approach 1:
A single reticle is segmented into multiple focus regions that can simultaneously handle both fine and coarse patterns. This eliminates the need for separate masks for dense cores and coarse wires, as both pattern types can be exposed in one lithography step using the appropriate focus region for each pattern type.
Solution Approach 2:
The functionality of multiple separate masks (one for dense cores, one for coarse wires) is merged into a single reticle with multiple focus regions. This consolidation maintains manufacturing precision for both pattern types while reducing device complexity by eliminating the need for multiple masks and multiple exposure steps.
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 enables the fabrication of larger semiconductor chips by utilizing the entire reticle area effectively, maintaining high precision at the core while allowing coarser features at the periphery, thus overcoming focus limitations and increasing chip size without the need for additional masks.
Implementation Method 1
light passes through a photomask within a reticle and exposes a photoresist layer
Implementation Method 2
the ability to focus coarse wavelengths of light through very finely patterned reticles becomes more difficult
Data Source
AI summary
A system that fabricates a semiconductor chip. The system places patterns for components which require fine line-widths within a high resolution region of a reticle, wherein the high resolution region provides sharp focus for a given wavelength of light used by the lithography system. At the same time, the system places patterns for components which do not require fine line-widths outside of the high-resolution region of the reticle, thereby utilizing the region outside of the high-resolution region of the reticle instead of avoiding the region. Note that the coarseness for components placed outside of the high resolution region of the reticle is increased to compensate for the loss of optical focus outside of the high resolution region.