Substrate Holder Burl Layout for Clamping Distorted Wafers
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Solution Overview
Problem
Substrates with high distortion, such as bowl-shaped or umbrella-shaped substrates, pose challenges in clamping and patterning due to inadequate substrate holder designs, leading to difficulties in achieving uniform substrate flatness and correct patterning, especially near the edges.
Innovation Solution
A substrate holder design featuring a main body with burls and an edge seal, where the edge seal is spaced apart from the burls to create a gap that is at least 75% of the burl pitch, and the burls are divided into two groups with the second group having increased vertical stiffness to effectively clamp substrates with significant warpage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the substrate holder uses conventional burl design without spaced edge seal, then the clamping force is sufficient for flat substrates, but the substrate cannot be adequately clamped when high distortion is present
Solution Approach 1:
The substrate holder surface is segmented into multiple burls distributed across the surface, with an additional edge seal segment positioned at the periphery. This segmentation allows different regions to perform specialized functions: central burls provide general support while the edge seal specifically addresses distortion by clamping the substrate edges, enabling effective handling of both flat and distorted substrates.
Solution Approach 2:
The edge seal is positioned specifically at the periphery of the substrate holder, creating a localized clamping region. This local quality enhancement allows the edge seal to specifically address the distortion problem at substrate edges without interfering with the central support function of the burls, thereby improving adaptability to distorted substrates while maintaining overall clamping effectiveness.
2Reliability
If the edge seal is positioned close to the burls, then the device complexity is reduced, but gas flow restriction is insufficient and clamping performance degrades
Solution Approach 1:
A gap is introduced as an intermediary space between the edge seal and the burls. This gap acts as a mediator that allows the edge seal to effectively restrict gas flow and improve vacuum clamping performance without requiring direct contact with the burls, thereby maintaining functional effectiveness while managing structural complexity.
3Manufacturing precision
If the burls are made with high vertical stiffness, then the substrate flatness is improved, but the wear of burls increases during loading and unloading
Solution Approach 1:
The substrate support function is segmented between multiple burls and the edge seal. The burls can be optimized for substrate flatness with appropriate stiffness, while the edge seal handles the mechanical stresses of loading and unloading. This segmentation distributes the wear burden and allows each component to be optimized for its specific function, extending overall system life while maintaining substrate flatness.
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 proposed substrate holder design improves the clamping of bowl-shaped substrates without compromising the performance on umbrella-shaped substrates, achieving better substrate flatness and enabling accurate pattern formation across the substrate surface.
Implementation Method 1
an edge seal projecting from the main body surface and extending around the plurality of burls so as to restrict gas flow when a substrate is held by the substrate holder
Data Source
AI summary
A substrate holder including: a main body having a main body surface; a plurality of burls projecting from the main body surface and configured for supporting the substrate; and an edge seal projecting from the main body surface; wherein: the edge seal is spaced apart from the plurality of burls so as to define a gap therebetween, the gap having a width greater than or equal to about 75% of a pitch of the plurality of burls; the plurality of burls includes a first group of burls and a second group of burls surrounding the first group of burls; and wherein the stiffness in the direction perpendicular to the support plane per unit area of the second group of burls is greater than or equal to about 150% of the stiffness in the direction perpendicular to the support plane per unit area of the first group of burls.