Substrate Table Protrusions with Micro-Elements for Lithography
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Solution Overview
Problem
In lithographic apparatuses, substrates tend to stick to substrate tables due to adhesion and electrostatic forces after the clamping process, leading to unreliable release and potential damage, which affects production yield and substrate quality.
Innovation Solution
The substrate table features protrusions with a pattern of elastic micro elements that reduce contact area and apply forces to facilitate easy release, using materials like polymeric molecules, nano-tubes, bucky balls, or glass pearls to create a monolayer coating that minimizes sticking and maintains surface flatness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a clamping device is activated to fix the substrate to the substrate table, then the substrate fixation stability is improved, but the substrate release reliability deteriorates due to sticking effects
Solution Approach 1:
The burl surface is modified with a specific pattern of micro-elements (dimples, protrusions, or roughness features) that create localized regions with different adhesion properties. These micro-structures reduce the overall contact area and adhesion forces between the substrate and burl surface, enabling reliable release while maintaining adequate fixation during processing
Solution Approach 2:
The continuous burl surface is segmented into discrete micro-elements (an array of small protrusions or dimples). This segmentation reduces the effective contact area between substrate and burl, thereby reducing adhesion forces and preventing sticking during release while maintaining sufficient clamping force during processing
2Ease of operation
If pressurized gas is used to counteract the sticking effect, then the substrate release is facilitated, but the substrate and burls may be damaged due to substrate slipping
Solution Approach 1:
The burl surface incorporates micro-structures (dimples, protrusions, or controlled roughness) that locally modify adhesion properties. These features reduce overall contact area and adhesion forces, enabling clean release without the need for pressurized gas, thereby avoiding substrate slipping and associated damage
Solution Approach 2:
The invention converts the potentially harmful sticking effect into a beneficial controlled release mechanism by designing the burl surface with specific micro-structures. The controlled reduction in adhesion through micro-patterned surfaces allows for reliable release without the harmful side effects of gas pressurization, such as substrate slipping and wear
3Ease of operation
If the substrate is peeled from the substrate table using a knock-out pin and swing cam, then the substrate release is achieved, but substrate breakage may occur reducing production yield
Solution Approach 1:
The burl surface is equipped with micro-structures (dimples, protrusions, or roughness features) that locally reduce adhesion forces. This gradual reduction in contact area allows the substrate to release uniformly without concentrated stress points, eliminating the need for mechanical peeling actions that could cause breakage
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 solution enables reliable and controlled substrate release, reducing contamination and wear on the substrate table, thereby improving throughput and extending the lifespan of the substrate table components.
Implementation Method 1
Adhesion forces may be generated by material impurities, and roughness imperfectness of the contacting surfaces
Implementation Method 2
The top surface of at least one of the protrusions includes a plurality of elements that define a reduced contact area between the substrate and the top surface of the protrusion
Implementation Method 3
The undesired sticking effect may be counteracted by providing a pressurized gas between the bottom section of the substrate and the top section of the supporting burls
Implementation Method 4
electrostatic forces generated by residual electrostatic charges
Data Source
AI summary
A lithographic apparatus includes an illumination system constructed and arranged to condition a radiation beam, and a support constructed and arranged to support a patterning device. The patterning device is capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam. The apparatus also includes a substrate table constructed and arranged to hold a substrate, and a projection system constructed and arranged to project the patterned radiation beam onto a target portion of the substrate. The substrate table includes a chuck having a plurality of protrusions constructed and arranged to support corresponding parts of a bottom surface of a wafer. The top surface of at least one of the protrusions includes a plurality of elements that define a reduced contact area between the substrate and the top surface of the protrusion.