Talbot Imaging Mask for Large Depth of Focus Grating Printing
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Solution Overview
Problem
Current photolithographic techniques, such as Talbot imaging, face challenges in achieving a large depth of focus for high-resolution grating patterns, especially when printing on non-flat substrates or thick photoresist layers, and require complex equipment for substrate displacement during exposure.
Innovation Solution
A method involving a mask with linear features twice the desired pattern period, using monochromatic light with a range of angles of incidence to create Talbot image planes, allowing integration of intensity distributions over angles, eliminating the need for substrate displacement during exposure and enabling the use of laser sources for improved pattern printing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If Talbot imaging is used to print high-resolution grating patterns, then manufacturing precision is improved, but depth of focus becomes very narrow
Solution Approach 1:
The patent introduces a scanning mechanism that dynamically moves the substrate relative to the mask during exposure. This dynamic movement allows the substrate to traverse through multiple Talbot image planes, effectively integrating the exposure over a larger depth range and thereby extending the depth of focus while maintaining high-resolution pattern transfer.
Solution Approach 2:
The scanning process employs periodic motion where the substrate is moved through the Talbot image planes at a controlled rate. This periodic scanning action ensures that each point on the substrate receives exposure from multiple Talbot planes, achieving both high resolution and extended depth of focus through time-integrated exposure.
2Reliability
If substrate displacement during exposure is implemented to extend depth of focus, then depth of focus is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex multi-axis substrate positioning systems with a simpler single-axis scanning mechanism. By using only one degree of freedom for substrate movement, the system achieves extended depth of focus without requiring the complex equipment needed for multi-dimensional positioning and alignment.
Solution Approach 2:
The patent changes the exposure parameter from static to dynamic by introducing controlled substrate motion. This parameter change allows the system to achieve extended depth of focus through temporal integration of exposure rather than through complex spatial positioning, thereby reducing device complexity.
3Manufacturing precision
If conventional imaging systems are used for high-resolution patterning, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts and eliminates the conventional imaging system (lenses, mirrors, and associated alignment mechanisms) from the lithographic apparatus. By using direct Talbot imaging where the mask pattern self-images at specific distances, the system achieves high-resolution patterning without the complex optical imaging train, thereby reducing device complexity while maintaining precision.
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 achieves high-resolution, large-depth-of-focus grating patterns on substrates without the complexity and drawbacks of existing Talbot techniques, facilitating efficient printing on large substrates with improved edge quality and reduced system complexity.
Implementation Method 1
a mask bearing a mask pattern of linear features that are parallel to a first direction; illuminating the mask pattern with the light with a range of angles of incidence that lie substantially in a plane parallel to said first direction, so that the light of each angle of illumination transmitted by the mask forms Talbot image planes
Implementation Method 2
exposes the photosensitive layer to an angle-dependent transversal intensity distribution, whereby an integration of said distribution over the range of angles prints the desired pattern
Data Source
AI summary
An apparatus and a method for printing a desired pattern into a photosensitive layer. A mask bears a pattern of linear mask features parallel to a first direction. The layer is arranged parallel to and separated from the mask. Substantially monochromatic light is generated and the mask pattern is illuminated with the light over a range of angles of incidence in a plane parallel to the first direction, at substantially a single angle in an orthogonal plane of incidence and so that the light of each angle of incidence transmitted by the mask forms a light-field component at the layer. The integration of the components prints the desired pattern. The range of angles is selected so that the integration of the components is substantially equivalent to an average of the range of transversal intensity distributions formed between Talbot image planes by light at one of the angles of incidence.