Object Table Clamping to Reduce Substrate Strain in Lithography
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Solution Overview
Problem
The clamping process in lithographic apparatuses often causes deformation of substrates, especially warped ones, leading to alignment issues between consecutive layers in semiconductor circuits.
Innovation Solution
An object table with an actuator arrangement that sequentially detaches and re-attaches portions of the object from the holding surface to mitigate strain caused by the holding force, using methods such as electrostatic clamping and pressurized gas to relieve stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a holding force is applied to clamp the substrate to the substrate table, then the substrate is securely held during exposure, but the substrate may deform due to the clamping force
Solution Approach 1:
The substrate table is divided into multiple independently controllable clamping zones or regions. Each zone can apply holding force separately, allowing the system to segment the clamping action and reduce localized stress that causes substrate deformation while maintaining overall substrate stability.
Solution Approach 2:
The clamping force is made dynamic and adjustable rather than static. The system can modify the magnitude and distribution of holding force in real-time based on substrate characteristics (such as warpage), enabling optimal balance between securing the substrate and preventing deformation-induced alignment errors.
2Strength
If a strong holding force is used to secure the substrate, then the substrate remains stable during the patterning process, but alignment accuracy between consecutive layers deteriorates due to substrate deformation
Solution Approach 1:
Different regions of the substrate table apply different holding forces tailored to local substrate conditions. Areas with higher warpage or susceptibility to deformation receive adjusted clamping forces, while stable regions maintain standard holding strength, thereby preventing localized deformation that would compromise alignment accuracy.
Solution Approach 2:
The system dynamically changes the parameters of the holding force (magnitude, distribution, timing) based on substrate characteristics and process requirements. By adjusting these parameters, the system maintains sufficient holding strength to secure the substrate while avoiding force levels that would cause deformation and subsequent alignment errors.
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 approach reduces substrate deformation, ensuring accurate alignment of patterns across multiple layers by minimizing strain during the clamping process.
Implementation Method 1
using methods such as electrostatic clamping and pressurized gas to relieve stress
Implementation Method 2
using methods such as electrostatic clamping and pressurized gas to relieve stress
Data Source
AI summary
An object table including: a holding surface for holding an object; and an actuator arrangement configured to exert a holding force on the object for holding the object to the holding surface, wherein the actuator arrangement is further configured to decrease a strain in the object caused by the holding force by sequentially detaching and re-attaching portions of the object from the holding surface, while the object is held to the holding surface.