EUV Lithography Multi-Exposure Mask Alignment
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Solution Overview
Problem
Conventional EUV lithographic apparatuses face limitations in achieving smaller critical dimensions due to constraints in wavelength, numerical aperture, and demagnification, which hinder the miniaturization of integrated circuits and other devices.
Innovation Solution
The development of an EUV lithographic apparatus with a demagnification of at least 5x and a numerical aperture of at least 0.4, allowing for multiple exposures with a single mask to achieve patterned areas smaller than conventional exposures, and a control system to move the mask and substrate table for precise alignment and exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional EUV lithographic apparatus with limited demagnification and numerical aperture is used, then existing lithographic processes are maintained, but the minimum printable feature size cannot be reduced further
Solution Approach 1:
The patent divides the exposure process into multiple sequential exposures using a single mask. The mask is exposed at different positions on the substrate table in multiple steps, allowing the creation of patterned areas that are smaller than conventional single-exposure fields. This segmentation of the exposure process enables reduced feature sizes without requiring complex changes to the lithographic apparatus itself.
Solution Approach 2:
The patent introduces a new dimensional approach by utilizing multiple exposure positions and orientations. Instead of relying solely on increasing numerical aperture or decreasing wavelength, the invention uses multi-position exposure sequences that effectively reduce the printed feature size by distributing the patterning process across multiple discrete exposure events at different locations on the substrate.
2Manufacturing precision
If multiple exposures are performed to achieve smaller patterned areas, then feature size is reduced, but exposure time and process complexity increase
Solution Approach 1:
The patent performs preliminary positioning and alignment of the mask and substrate table before each exposure step. By pre-positioning the components and using alignment marks, the system minimizes the time required for each exposure step. The control system coordinates mask and substrate table movements in advance, reducing idle time and ensuring that each of the multiple exposures can be performed efficiently with minimal setup overhead.
Solution Approach 2:
The patent maintains continuous useful action by overlapping exposure fields and using a single mask throughout the process. The mask remains in the lithographic apparatus for all exposures, eliminating mask change time. The substrate table is moved continuously between exposure positions, and exposure fields are arranged to minimize non-productive movement time, ensuring that the useful exposure action is maximized relative to total process time.
3Ease of manufacture
If a single mask is used for multiple exposures, then mask cost is reduced, but precise alignment between exposures becomes more difficult
Solution Approach 1:
The patent employs feedback mechanisms through alignment marks that are detected by the control system. The control system monitors the positions of alignment marks on the substrate and uses this information to adjust mask and substrate table positions for subsequent exposures. This feedback loop ensures that each exposure is precisely aligned with previous exposures, maintaining measurement precision despite multiple exposure steps.
Solution Approach 2:
The patent uses alignment marks as reference copies that are replicated across different exposure fields. These marks serve as fiducial references that allow the control system to accurately determine the position and orientation of each exposure field relative to others. By copying the same alignment mark pattern across multiple fields, the system achieves precise registration without requiring complex measurement systems.
Data Source
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AI summary
A method of exposing a patterned area on a substrate using an EUV lithographic apparatus having a demagnification of about 5x and a numerical aperture of about 0.4 is disclosed. The method comprises exposing a first portion of the patterned area on the substrate using a first exposure, the first portion dimensions are significantly less than the dimensions of a conventional exposure, and exposing one or more additional portions of the patterned area on the substrate using one or more additional exposures, the additional portions having dimensions which are significantly less than the dimensions of a conventional exposure. The method further comprises repeating the above to expose a second patterned area on the substrate, the second patterned area being provided with the same pattern as the first patterned area, wherein a distance between centre points of the first and second patterned areas corresponds with a dimension of a conventional exposure.