Imprint Lithography Alignment via Composite Diffraction Grating
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Solution Overview
Problem
In lithography, achieving precise alignment of patterns on a substrate with an imprint template is challenging, especially when dealing with small feature sizes, as existing methods are costly and limited by radiation wavelength or numerical aperture, leading to potential electrical connectivity issues in integrated circuits.
Innovation Solution
A method and apparatus using a composite diffraction grating formed by alignment gratings on the substrate and imprint template, employing radiation at multiple wavelengths to determine and maintain the separation and position of these gratings during lateral movement, allowing for precise alignment without the limitations of traditional lithography.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If photolithography is used to reduce feature size, then resolution is improved, but cost increases significantly
Solution Approach 1:
The patent replaces optical lithography systems with mechanical imprint lithography. Instead of using complex optical projection systems with high numerical aperture lenses and specific wavelength radiation sources, the invention uses a physical stamp or template that mechanically transfers the pattern directly onto the substrate. This substitution of mechanical imprinting for optical projection dramatically reduces the cost while achieving comparable or superior resolution, as the resolution is now limited only by the manufacturing precision of the stamp rather than by diffraction limits of light.
2Measurement precision
If alignment apparatus is used to align patterns, then alignment accuracy is improved, but device complexity increases
Solution Approach 1:
The patent merges the alignment function with the imprinting process itself. Alignment marks are incorporated directly into the stamp and substrate designs, allowing alignment to be performed optically during the imprinting operation. The alignment gratings on both the stamp and substrate form a composite diffraction grating that enables precise measurement of lateral position and separation. This integration eliminates the need for separate, complex alignment apparatus while maintaining high alignment accuracy through the use of diffraction-based measurements.
3Ease of operation
If single wavelength radiation is used for alignment, then measurement simplicity is improved, but alignment precision deteriorates
Solution Approach 1:
The patent changes the wavelength parameter of the radiation used for alignment measurements. By using radiation with a wavelength that is sufficiently long relative to the pitch of the alignment gratings, the invention ensures that significant amounts of radiation in the first diffraction order do not propagate between the alignment gratings. This wavelength selection enables precise measurement of the separation between the substrate alignment grating and the imprint template alignment grating, as the diffraction pattern becomes highly sensitive to changes in separation distance while remaining relatively insensitive to lateral position shifts.
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
Enables accurate and cost-effective alignment of patterns on a substrate relative to an imprint template, ensuring proper electrical connections in integrated circuits by utilizing the diffraction properties of radiation at different wavelengths to maintain constant separation and position, thus overcoming the limitations of feature size and wavelength constraints.
Implementation Method 1
positioning the substrate adjacent to the imprint template such that an alignment grating on the substrate and an alignment grating on the imprint template form a composite diffraction grating; directing the alignment radiation beam at the composite diffraction grating; detecting radiation diffracted from the composite grating
Data Source
AI summary
A method of determining the location of a lithographic substrate relative to an imprint template is disclosed. The method includes positioning the substrate adjacent to the imprint template such that an alignment grating on the substrate and an alignment grating on the imprint template form a composite diffraction grating, directing alignment radiation beam comprising radiation at a first wavelength and radiation at a second wavelength, the second wavelength being longer than the first wavelength, at the composite diffraction grating, detecting radiation diffracted from the composite grating during relative lateral movement between the imprint template and the substrate, using the detected radiation at the second wavelength to obtain information regarding a separation between the substrate alignment grating and the imprint template alignment grating, and using the detected radiation at the first wavelength to obtain information regarding the lateral position of the substrate alignment grating relative to the imprint template alignment grating.