Floating Wafer Chuck Edge Gripper Flexure Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing wafer handling techniques face challenges in maintaining a flat wafer surface during inspection, as edge grippers can exacerbate warping and deformation, leading to undesirable slope issues, especially during spinning, and are ineffective in flattening wafers with complex warp shapes.
Innovation Solution
A chuck system with gas flow openings and edge grippers featuring pivoting fingers, flexures, and actuators that minimize vertical deformation and provide a stable air-vacuum film to float the wafer, allowing for precise contact and spinning without surface damage, using materials like perfluoroelastomer and polyether ether ketone for contact pads and aluminum or steel for structural components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If edge grippers are used to hold the wafer, then the wafer can be secured for handling and spinning, but the wafer surface slope increases due to deformation and warping
Solution Approach 1:
The edge gripper is divided into multiple independent fingers (typically three) that can contact the wafer at different locations around the edge. This segmentation allows the gripper to distribute holding forces more evenly and adapt to various wafer warp shapes, reducing localized deformation and maintaining surface flatness while securing the wafer for handling and spinning operations
Solution Approach 2:
The edge gripper incorporates flexures that enable the fingers to dynamically adjust their position and orientation in response to wafer warping. This dynamic adaptation allows the gripper to maintain contact with the wafer edge while accommodating complex warp shapes, preventing the transmission of excessive forces that would exacerbate surface slope and deformation
2Speed
If conventional edge grippers are used during wafer spinning, then the wafer can be rotated at high speeds, but the wafer slope and deformation are exacerbated
Solution Approach 1:
The gripper design changes the mechanical parameters of contact by using flexures with specific stiffness characteristics. These flexures are engineered to provide appropriate compliance during spinning, allowing the gripper to maintain holding force while accommodating centrifugal forces and wafer deformation, thereby enabling high-speed spinning without exacerbating surface slope
3Reliability
If edge grippers with rigid contact are used, then the wafer can be held firmly, but complex warp shapes cannot be flattened
Solution Approach 1:
The flexure-based design enables the gripper fingers to dynamically adapt to complex warp shapes while maintaining firm holding. The flexures provide the necessary compliance to contact the wafer at the correct locations and angles, allowing the gripper to effectively flatten various warp configurations while securing the wafer firmly for processing
Solution Approach 2:
Each finger of the edge gripper can independently adjust its local contact characteristics to match the specific warp conditions at that location. This local adaptation capability allows the gripper to handle diverse warp shapes effectively, applying appropriate forces to flatten complex warps while maintaining overall wafer security
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 solution effectively reduces wafer jitter and maintains a flat surface, enabling reliable inspection and spinning up to 6,000 rpm without surface contamination or excessive deformation, even for non-flat wafers, by using a matrix of vacuum and pressure nozzles and edge grippers with flexures to hold the wafer edge.
Implementation Method 1
The chuck has a surface with a plurality of gas flow openings configured to provide a flow of gas
Implementation Method 2
The flexure is configured to flex toward and away from the chuck in the vertical direction
Implementation Method 3
A wafer is floated above a chuck on an air-vacuum film between a surface of the chuck and the wafer
Data Source
AI summary
Edge grippers are disposed around an outer edge of a chuck. Each of the edge grippers includes a finger configured to pivot around a point; a contact pad configured to contact the wafer; and a flexure disposed between the contact pad and the finger. The flexure is configured to flex toward and away from the chuck. The chuck can use a matrix of vacuum and pressure nozzles designed to keep a wafer floating above the chuck. The edge grippers can hold the wafer at the edge while minimizing deformation of the wafer or without affecting z-jitter of the wafer.