Segmented Electrostatic Clamp for Substrate Focal Plane Alignment
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Solution Overview
Problem
Lithographic apparatuses suffer from optical aberrations and non-flat substrates, leading to reduced pattern projection quality due to misalignment of projection surfaces with the focal plane.
Innovation Solution
An electrostatic clamp with a clamp body and a planar electrode arrangement featuring independently-addressable electrodes separated by an insulating layer, generating an attractive electrostatic field to secure objects, such as substrates, onto burls, allowing for controlled deformations to align with the projection system's focal plane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a lithographic apparatus uses electromagnetic radiation with a specific wavelength to project patterns, then the minimum feature size on the substrate is determined, but optical aberrations and non-flat substrates cause projection surfaces to be out of the focal surface, reducing pattern projection quality
Solution Approach 1:
The clamp uses independently addressable electrodes that can dynamically adjust the shape of the substrate or patterning device by applying electrostatic forces. This allows real-time correction of flatness defects and adaptation to compensate for optical aberrations, ensuring the projection surface remains in the focal surface throughout the exposure process
Solution Approach 2:
The system changes the physical state of the substrate or patterning device by applying controlled electrostatic forces through the electrode arrangement. This causes measurable deformation of the projection surface, transforming it from a non-flat state to a corrected flat state that aligns with the focal surface, thereby improving pattern projection quality
2Adaptability or versatility
If multiple independently-addressable electrodes are provided in a planar arrangement separated in the direction normal to the plane, then multiple electrodes can be positioned adjacent to each other for generating attractive electrostatic fields, but the electrode structure becomes more complex with insulating layers and separators
Solution Approach 1:
Instead of arranging multiple electrodes side-by-side in the plane, the invention stacks electrodes in the direction normal to the plane. This vertical stacking allows multiple independently addressable electrodes to occupy the same footprint area, increasing electrode density and adaptability while reducing the planar footprint and overall device complexity
Solution Approach 2:
The electrode structure uses nested layers where electrodes are positioned at different heights (normal to the plane) and separated by insulating layers. Each electrode is effectively nested within the vertical stack, allowing independent addressing while sharing the same lateral space, thereby achieving high versatility without proportionally increasing device complexity
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 electrostatic clamp effectively mitigates optical aberrations and flatness defects by inducing deformations that correct substrate positioning, enhancing pattern projection quality and alignment with the projection system's focus.
Implementation Method 1
the at least two independently-addressable electrodes are configured for generating an attractive electrostatic field for securing an object onto the plurality of burls
Implementation Method 2
inducing deformations that correct substrate positioning, enhancing pattern projection quality and alignment with the projection system's focus
Data Source
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AI summary
The present disclosure relates to an electrostatic clamp for a lithographic apparatus comprising a clamp body; a generally planar electrode arrangement comprising: a plurality of electrodes, arranged in a plurality of segments; and one or more connecting layers, configured to allow individual address of the plurality of electrodes; a plurality of burls projecting from the clamp body; and one or more demultiplexers in electrical communication with the one or more connecting layers, wherein the one or more demultiplexers are configured to sequentially address selections of the plurality of electrodes with a voltage source, thereby providing voltages to the selected electrodes.