Substrate Edge Support with Gas Cushion Deflection Compensation
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Solution Overview
Problem
Substrates, such as wafers, experience deformation and contamination during photolithography due to suction-based support methods, which can lead to structural resolution issues and non-uniformity, as well as damage to active areas from mechanical contact or particle contamination.
Innovation Solution
A method and apparatus that mechanically support the substrate at its edge while providing a dynamic non-mechanical gas cushion in the active area to compensate for deformation and prevent contamination, using a controllable nozzle to generate a radial gas flow that maintains contact force and adjusts for substrate properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the substrate is supported across the whole support surface by suction, then the substrate is securely fixed, but the active area of the substrate is damaged or contaminated by particles
Solution Approach 1:
The support surface is segmented into two distinct zones: an inner area with suction apertures for securing the substrate, and an outer peripheral area that remains free of suction apertures to avoid contaminating the active area. This spatial segmentation allows the substrate to be fixed reliably while protecting the active area from particle contamination.
Solution Approach 2:
Different regions of the support surface are given different functional qualities: the inner area has suction capability for secure fixing, while the outer peripheral area is designed to be particle-free to prevent contamination. This local differentiation of properties resolves the contradiction between secure fixing and contamination prevention.
2Object-affected harmful factors
If the substrate is supported at its peripheral edge only, then the active area is protected from contamination, but the substrate deflects or bends downward due to gravity
Solution Approach 1:
An air cushion is generated between the substrate and the mask to counterbalance the gravitational force causing downward deflection. This air pressure acts as a counterweight force that supports the substrate's weight, maintaining its flatness while the peripheral edge support protects the active area from contamination.
Solution Approach 2:
A layer of air is introduced as an intermediary between the substrate and the mask to prevent direct contact and provide upward support force. This air intermediary simultaneously prevents contamination and counteracts gravitational deflection.
3Object-affected harmful factors
If an air cushion is built-up between the substrate and mask, then contactless support is achieved, but the substrate may still deflect due to insufficient support force
Solution Approach 1:
The pressure parameters of the air cushion are optimized to provide sufficient support force. By controlling the air pressure between the substrate and mask, the system achieves contactless support while generating enough upward force to counteract gravitational deflection and maintain 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
This solution allows for controlled compensation of substrate deflection, maintains parallelity with the mask, and reduces particle contamination, enhancing process quality by avoiding mechanical contact and minimizing deflection-related issues.
Implementation Method 1
said edge portion 2 is provided with apertures 4 connected to a vacuum source V in order to provide a low pressure to the interface between the contact surface of the edge portion 2 and the edge area 7 of the substrate for fixing the substrate 6 to the chuck 1
Implementation Method 2
the apparatus of the invention, however, avoids such unwanted deflection by means of a gas cushion 9 created in the central portion of the gap between the chuck 1 and the substrate 6
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3
AI summary
The method and the apparatus prevents the deformation of a substrate, e.g. a wafer, supported with its edge area or periphery at a support or chuck, and also avoids the damage and/or contamination of the active area of the substrate. In particular, the substrate is mechanically supported at its peripheral or edge portion, namely in the non-active area of the substrate, only; an additional non-mechanical extended support is provided in the active area by means of a gas cushion. The gas cushion is generated by means of a controllable nozzle or purge for a distinct and controlled compensation of the downward deflection of the substrate (Fig. 1).