Re-entrant Aperture Substrate Holder for Lithography Flatness
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Solution Overview
Problem
The increasing size of silicon substrates and demand for improved substrate flatness in lithographic apparatuses pose challenges for existing substrate holders and e-pins, leading to unflatness and reduced yield due to unsupported spans and contamination risks.
Innovation Solution
A substrate holder with re-entrant apertures and burls that reduce the unsupported span and contamination risks, featuring a substrate table with e-pins having re-entrant tip portions and an actuator system for precise control, ensuring improved flatness and handling of larger substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If multiple e-pins are used to support larger diameter substrates, then the substrate can be supported across larger areas, but the unsupported span between support points increases leading to reduced flatness
Solution Approach 1:
The aperture is segmented into multiple regions by re-entrant features that create distinct zones. Burls are positioned within these re-entrant regions to provide multiple localized support points within a single aperture structure, effectively reducing the unsupported span while maintaining coverage of large substrate areas
Solution Approach 2:
The substrate holder provides different support characteristics at different locations. Re-entrant regions concentrate support functionality at specific points where burls are positioned, creating locally optimized support zones that reduce span lengths critical for maintaining flatness, while other regions accommodate e-pin access and substrate handling
2Adaptability or versatility
If e-pins are positioned away from the center to handle larger substrates, then coverage is improved, but the structural support and flatness control deteriorate
Solution Approach 1:
Burls are nested within the re-entrant regions of the aperture structure, creating a hierarchical arrangement where support functionality is embedded within the aperture geometry itself. This nested configuration allows e-pins to be positioned peripherally for large substrate handling while burls provide centralized support within the aperture for flatness control
Solution Approach 2:
The re-entrant features add a dimensional complexity to the aperture design, creating inward-pointing geometric features that provide vertical and radial support components. This multi-dimensional aperture structure enables peripheral e-pin positioning for adaptability while maintaining central support stability through the re-entrant geometry
3Ease of manufacture
If the substrate holder uses conventional aperture design, then manufacturing is simpler, but substrate flatness and yield are reduced
Solution Approach 1:
The re-entrant features and burl positions are pre-designed into the substrate holder aperture structure during manufacturing. This preliminary configuration of support zones within the aperture geometry ensures that when substrates are loaded, the flatness-critical regions are already optimized, eliminating the need for post-manufacturing adjustments while maintaining high 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
The solution enhances substrate flatness, reduces unflatness and contamination, and increases yield by minimizing the unsupported span and optimizing the distribution of forces during substrate handling and exposure.
Implementation Method 1
The substrate must be held firmly to prevent shifts as a substrate table on which it is held is moved. It is conventional to clamp the substrate to a substrate holder using an electrostatic clamp or a vacuum clamp.
Implementation Method 2
The substrate must be held firmly to prevent shifts as a substrate table on which it is held is moved. It is conventional to clamp the substrate to a substrate holder using an electrostatic clamp or a vacuum clamp.
Data Source
AI summary
A substrate table supports a substrate holder to which a substrate is clamped for exposure. The substrate table has a plurality of e-pins spaced apart from and distributed around the center of the substrate holder to receive, and lower, a substrate onto the substrate holder prior to exposure, and to raise a substrate off the substrate holder after exposure. Tip portions of the e-pins and the corresponding apertures in the substrate holder have a shape in plan including at least one re-entrant, e.g. a cross shape.