Segmented Object Table Clamping for Low-Strain Lithography
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Solution Overview
Problem
The clamping process in lithographic apparatuses can cause deformation of substrates, particularly warped ones, leading to alignment issues between consecutive layers in semiconductor circuits.
Innovation Solution
An object table with an actuator arrangement that exerts a holding force while sequentially detaching and re-attaching portions of the object from the holding surface to mitigate strain caused by clamping.
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 holding surface is divided into multiple independently controllable holding regions. Each region can be activated or deactivated separately, allowing the system to apply holding force to only the necessary portions of the substrate while leaving other areas free, thereby reducing overall deformation while maintaining adequate holding stability.
Solution Approach 2:
The holding force is applied dynamically through sequential activation of holding regions rather than static simultaneous activation. The actuator arrangement activates holding regions in a specific sequence, adjusting the holding force over time to minimize deformation while ensuring the substrate remains securely held throughout the exposure process.
2Manufacturing precision
If the substrate is clamped onto the substrate table, then alignment during exposure is maintained, but alignment accuracy between consecutive layers deteriorates due to substrate deformation
Solution Approach 1:
By segmenting the holding surface into multiple independently controllable regions, the system can apply holding force selectively to minimize substrate deformation. This segmentation allows the substrate to maintain its shape more accurately, thereby improving alignment precision between consecutive layers during multi-layer semiconductor manufacturing.
Solution Approach 2:
The system changes the spatial distribution and temporal sequence of holding force parameters. By controlling which holding regions are activated and in what sequence, the system optimizes the holding force parameters to reduce substrate deformation while maintaining adequate holding stability, thus improving alignment accuracy.
3Reliability
If a holding force is exerted on the substrate, then the substrate remains stationary during exposure, but strain in the substrate increases causing deformation
Solution Approach 1:
The holding surface is divided into multiple independently controllable holding regions. Each region can be activated or deactivated separately, allowing the system to apply holding force to only the necessary portions of the substrate while leaving other areas free, thereby reducing overall deformation while maintaining adequate holding stability.
Solution Approach 2:
The holding regions are activated in a periodic sequence rather than all at once. This periodic activation pattern allows the substrate to adjust gradually to the holding force, reducing strain accumulation and deformation while maintaining holding stability throughout the exposure process.
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.