Lithography Substrate Sag Compensation via Protrusion Pressure
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Solution Overview
Problem
Lithographic processes face challenges in maintaining the flatness of thin substrates, which can warp due to minor uneven forces, affecting subsequent lithographic and metrology processes.
Innovation Solution
A support table with protrusions and a pressure device is used to suspend the substrate, with the pressure device adjusting pressure to counteract sagging caused by the substrate's material and dimensions, thereby maintaining flatness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If thin substrates are used in lithography, then productivity and pattern quality are improved, but substrate flatness deteriorates due to sagging and warping
Solution Approach 1:
The substrate support system is segmented into multiple protrusions distributed across the substrate table, with each protrusion independently supporting a portion of the substrate. This segmentation allows localized pressure application to counteract sagging while maintaining overall substrate flatness during lithographic processing.
Solution Approach 2:
Different regions of the substrate table have different support characteristics - protrusions are strategically positioned to provide localized support at critical sagging points. The pressure device applies localized force through individual protrusions, allowing non-uniform pressure distribution tailored to the specific sagging pattern of the thin substrate.
2Weight of moving object
If substrates are made thinner to reduce mass, then acceleration and positioning are improved, but mechanical strength deteriorates causing warping under minor forces
Solution Approach 1:
The pressure device generates an upward force through the protrusions that counteracts the downward gravitational force and external loads acting on the thin substrate. This counterbalancing force prevents the substrate from warping or bending, effectively compensating for its reduced mechanical strength despite the thinner design.
Solution Approach 2:
The pressure device is activated before and during the lithographic exposure process to preemptively counteract any potential sagging or warping. This preliminary support action ensures the substrate maintains its flat state throughout the entire processing sequence, preventing deformation that would occur if support were applied only after distortion begins.
3Shape
If protrusions are used to support substrates, then substrate sagging is reduced, but device complexity increases
Solution Approach 1:
The protrusions serve multiple functions simultaneously: they provide mechanical support to prevent sagging, act as pressure application points for the pressure device, and can be positioned to optimize both substrate flatness and optical access. This multi-functionality reduces the need for separate support structures, thereby limiting the increase in 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
This solution effectively reduces substrate sagging, ensuring accurate and precise lithographic and metrology processes by maintaining the required flatness within sub-micron tolerance margins.
Implementation Method 1
Sagging of the substrate when supported by the support table can be caused by the material(s) and/or dimensions of the substrate
Implementation Method 2
The pressure device is configured to adjust a pressure on a side of the substrate such that the sagging is reduced
Data Source
AI summary
A system includes a support table having one or more protrusions and a pressure device. The one or more protrusions contact and support a substrate such that the substrate is suspended with respect to the support table. Sagging of the substrate when supported by the support table is based on a material and/or dimensions of the substrate. The pressure adjusts a pressure on a side of the substrate such that the sagging is reduced.