Reticle Gripper Exactly Constrained Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional reticle grippers in lithographic apparatuses often cause deformation of reticles due to forced geometric congruence and non-flatness errors, leading to overlay errors in the photolithographic process.
Innovation Solution
A reticle gripper with an exactly constrained design that fixes three points on the reticle's surface, using rigid contact point structures and vacuum pads to minimize deformation by applying forces only where necessary, thereby reducing the risk of deformation during handling and transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If forced geometric congruence is used to hold the reticle, then the reticle can be securely held by the gripper, but the reticle may be deformed due to manufacturing non-flatness errors
Solution Approach 1:
The contact points are arranged in a curved or non-planar configuration rather than forcing flat-to-flat contact. This allows the gripper to accommodate manufacturing non-flatness errors while maintaining secure holding through distributed curved surface contact, preventing deformation of the reticle.
Solution Approach 2:
The invention changes the geometric parameters of the contact interface from rigid flat surfaces to compliant or curved surfaces that can adapt to manufacturing tolerances. This parameter change allows the system to maintain both secure holding and reticle flatness by accommodating variations in the reticle surface geometry.
2Reliability
If vacuum pressure is used to force the reticle into contact with the gripper, then the reticle can be held firmly, but the reticle may be warped or bowed due to excessive holding force
Solution Approach 1:
Instead of applying vacuum pressure uniformly across the entire reticle surface, the invention applies holding force only at specific localized contact points. This local quality approach maintains firm holding while minimizing the total force applied, thereby preventing warping and bowing of the reticle.
Solution Approach 2:
The invention uses partial action by applying vacuum pressure only at the necessary contact points rather than across the entire reticle surface. This partial application of force is sufficient to secure the reticle while avoiding excessive force that would cause deformation.
3Stability of the object's composition
If the reticle is held by both the gripper and reticle stage simultaneously with vacuum pressure, then the transfer is stable, but any deformation may be locked in due to the mechanics of simultaneous holding
Solution Approach 1:
The invention uses preliminary action by pre-positioning the reticle on the reticle stage before the gripper releases it. The transfer sequence is carefully controlled so that the reticle is already stable on the stage when the gripper's holding force is reduced, preventing deformation locking during the transfer process.
Solution Approach 2:
The transfer process uses periodic action with distinct phases: first the gripper holds and positions the reticle, then the reticle is released to the stage in a controlled sequence. This periodic transfer mechanism ensures stability while avoiding simultaneous dual-point contact that could lock deformations.
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 exactly constrained design significantly reduces the risk of reticle deformation during handling and transfer, minimizing overlay errors in the photolithographic process by avoiding over-constraint and allowing for precise positioning without locking in unwanted deformations.
Implementation Method 1
vacuum pressure is used to force the reticle into contact with the gripper
Data Source
AI summary
A reticle gripper to hold a reticle of a lithographic apparatus is presented. The reticle gripper includes three gripper structures to contact the surface of the reticle. Each of the three gripper structures determines a position with respect to the reticle gripper of one of the points on the surface of the reticle.