Lithographic Apparatus Beam Combiner Off-Axis Illumination
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Solution Overview
Problem
Current lithographic techniques, such as photolithography, face limitations in achieving high resolution and pattern accuracy for features below 85 nm due to the constraints of the Rayleigh criterion, particularly in printing contact holes and vias, as existing resolution enhancement techniques like attenuated or alternating phase shift masks and sub-resolution assist features are not feasible for smaller sizes.
Innovation Solution
A lithographic apparatus utilizing beam splitters and diffraction gratings to create spatially coherent radiation beams, which are then combined to form an interference pattern on the substrate, enabling off-axis illumination and improving resolution and depth of focus by capturing multiple diffraction orders, thus allowing for sharper images and smaller feature sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional photolithography with phase shift masks and sub-resolution assist features is used, then process latitude is maintained, but resolution deteriorates for features below 85 nm
Solution Approach 1:
The illumination beam is segmented into multiple spatially coherent beams by beam splitters, creating distinct diffraction orders that are subsequently recombined. This segmentation allows selective capture of multiple diffraction orders to improve resolution without sacrificing process latitude
Solution Approach 2:
The patent transitions from conventional on-axis illumination to off-axis illumination by redirecting diffraction orders through beam splitters and mirrors. This dimensional change in the illumination geometry enables capture of higher spatial frequencies while maintaining process stability
2Manufacturing precision
If the numerical aperture is increased to improve resolution, then manufacturing precision improves, but the system complexity increases
Solution Approach 1:
Beam splitters and mirrors are introduced as intermediary optical elements to redirect and recombine diffraction orders. These intermediaries enable off-axis illumination and multiple diffraction order capture without requiring direct increases in numerical aperture, thus improving resolution while managing system complexity
3Manufacturing precision
If multiple diffraction orders are captured to improve resolution, then manufacturing precision improves, but the illumination system complexity increases
Solution Approach 1:
The beam splitter system is designed to perform multiple functions: separating diffraction orders, redirecting them to different paths, and enabling their recombination at the substrate. This multi-functionality allows capture of multiple diffraction orders for improved resolution while consolidating control within a unified optical architecture
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 printing of features with half-pitches as small as 35 to 40 nm, significantly increasing the depth of focus and pattern resolution, overcoming the limitations of conventional techniques by generating complex interference patterns with improved coherence and angular edge capture.
Implementation Method 1
a first diffraction grating configured to create a first plurality of spatially coherent radiation beams; a second diffraction grating configured to receive at least a portion of the first plurality of spatially coherent radiation beams and to create, based on the first plurality of spatially coherent radiation beams, a second plurality of spatially coherent radiation beams
Implementation Method 2
a beam combiner adapted to redirect and combine at least a portion of the second plurality of spatially coherent radiation beams onto a surface of a substrate to form an interference pattern
Data Source
AI summary
A lithographic apparatus includes a first diffraction grating configured to create a first plurality of spatially coherent radiation beams and a second diffraction grating configured to receive at least a portion of the first plurality of spatially coherent radiation beams and to create, based on the first plurality of spatially coherent radiation beams, a second plurality of spatially coherent radiation beams. The apparatus also includes a beam combiner adapted to redirect and combine at least a portion of the second plurality of spatially coherent radiation beams onto a surface of a substrate to form an interference pattern.