Vacuum Sheet Fixturing for Submicron Substrate Table Bonding
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Solution Overview
Problem
Existing technologies struggle to control tribological properties and achieve sub-micrometer tolerances in substrate tables for DUV and EUV radiation systems, leading to issues such as uneven surfaces, substrate sticking, and uncorrectable wafer deformations during loading.
Innovation Solution
The use of vacuum sheet bond fixturing and flexburls on substrate tables, including a core body with burls surrounded by trenches, to achieve precise bonding and reduce wafer deformations by tuning lateral stiffness and vacuum volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the surface of the substrate table is made ultra-smooth, then the substrate can be securely held, but the surfaces may stick together making substrate disengagement difficult
Solution Approach 1:
The substrate table surface is engineered with non-uniform topology featuring burls (protrusions) and valleys (recesses) rather than a uniformly smooth surface. The burls make localized contact points with the substrate while valleys provide air gaps, creating differential surface properties that prevent sticking while maintaining secure holding at contact points.
Solution Approach 2:
The substrate table incorporates a porous-like structure with intentional voids and air gaps between the burls and substrate surface. This allows air to be trapped in the valleys, creating a cushion effect that prevents direct metal-to-metal contact and reduces sticking while maintaining vacuum holding force through the burl contact points.
2Manufacturing precision
If traditional bonding methods are used for substrate table assembly, then manufacturing is simpler, but sub-micrometer bonding tolerances cannot be achieved
Solution Approach 1:
Traditional mechanical bonding methods (screws, adhesives, mechanical fasteners) are replaced with a magnetic field-based bonding system. Magnets embedded in the substrate table create magnetic attraction forces that hold the substrate in place, enabling sub-micrometer positioning precision without the complexity of mechanical fastening systems.
Solution Approach 2:
The bonding mechanism transitions from mechanical contact-based bonding to field-based bonding by changing the physical parameter from mechanical force to magnetic force. This allows for precise control of bonding strength and positioning accuracy through magnetic field parameters rather than mechanical tolerances.
3Ease of operation
If the substrate table surface is made uneven to prevent sticking, then substrate disengagement is improved, but wafer deformations during loading become uncorrectable
Solution Approach 1:
The surface features localized burls and valleys with controlled dimensions and spacing. The burls provide localized contact points that prevent sticking while the overall surface maintains sufficient flatness through precise control of burl height and distribution, ensuring wafer deformations remain within correctable limits.
Solution Approach 2:
Rather than making the entire surface uneven, only partial regions are modified with burls and valleys. The degree of surface modification is controlled to be sufficient to prevent sticking but not excessive to cause uncorrectable wafer deformations, achieving the optimal balance through controlled partial modification.
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
Enables submicron bonding tolerances and reduces wafer load grid errors, improving substrate handling and reducing overlay errors in DUV and EUV lithographic processes.
Implementation Method 1
Vacuum sheet bond fixturing for mounting the core body to the electrostatic sheet
Implementation Method 2
an electrostatic clamp for use in EUV radiation systems
Data Source
AI summary
Systems, apparatuses, and methods are provided for manufacturing a substrate table. An example method can include forming a vacuum sheet including a plurality of vacuum connections and a plurality of recesses configured to receive a plurality of burls disposed on a core body for supporting an object such as a wafer. Optionally, at least one burl can be surrounded, partially or wholly, by a trench. The example method can further include using the vacuum sheet to mount the core body to an electrostatic sheet including a plurality of apertures configured to receive the plurality of burls. Optionally, the example method can include using the vacuum sheet to mount the core body to the electrostatic sheet such that the plurality of recesses of the vacuum sheet line up with the plurality of burls of the core body and the plurality of apertures of the electrostatic sheet.