Contactless Wafer Carrier Positioning With Magnetic Levitation
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Solution Overview
Problem
Existing wafer alignment methods in semiconductor manufacturing involve physical contact, leading to wear and reliability issues in wafer transport systems.
Innovation Solution
A contactless wafer positioning system using a magnetic levitation and vacuum-based wafer carrier design, incorporating an electromagnet and permanent magnet, allows for precise alignment without physical contact by repelling or attracting the wafer carrier from the chuck, and utilizing dual vacuum cavities for secure holding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If physical contact is used for wafer alignment, then alignment can be achieved, but wear and reliability issues occur in wafer transport systems
Solution Approach 1:
The patent replaces the mechanical contact-based alignment system with a magnetic field-based levitation system. The wafer carrier with permanent magnet is levitated above the wafer chuck using electromagnetic forces, eliminating all mechanical contact points that previously caused wear. The alignment is achieved through magnetic field control rather than physical friction and contact.
Solution Approach 2:
The patent introduces a magnetic field as an intermediary between the wafer carrier and the wafer chuck. The electromagnet and permanent magnet create a magnetic field that serves as the mediating force for both levitation and alignment, replacing direct mechanical contact with field-based interaction that avoids wear.
2Reliability
If magnetic levitation is used to eliminate contact, then wear is reduced, but system complexity increases due to electromagnets and vacuum cavities
Solution Approach 1:
The wafer chuck is designed with multiple functions integrated into a single component: it serves as both the support structure and contains the electromagnet for levitation, while also incorporating vacuum cavities for securing the wafer. The wafer carrier similarly integrates the permanent magnet and vacuum cavity functionality. This multi-functionality reduces the number of separate components needed.
Solution Approach 2:
The patent merges the levitation mechanism and the vacuum holding mechanism into a unified system. The electromagnet and permanent magnet are positioned within the same structural framework that contains the vacuum cavities, combining magnetic levitation and vacuum securing functions into an integrated apparatus rather than separate systems.
3Reliability
If vacuum is applied to hold wafer, carrier, and chuck together, then secure holding is achieved, but alignment adjustment becomes more difficult
Solution Approach 1:
The patent employs periodic switching between different vacuum states to facilitate alignment. The vacuum is applied and released in sequence: first applied to secure the wafer to the carrier, then selectively applied to the chuck to hold the carrier in position during alignment, and finally fully applied to lock everything in place. This periodic action allows alignment adjustments during intermediate states.
Solution Approach 2:
The vacuum system is designed to be dynamic and controllable, with independent vacuum cavities that can be pressurized or depressurized as needed. This dynamic control allows the system to transition between different holding states, enabling alignment adjustments when vacuum is reduced while maintaining secure holding when vacuum is applied.
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
Enables precise and reliable wafer alignment with reduced system wear, enhancing the precision and reliability of semiconductor processing steps like lithography and film deposition.
Implementation Method 1
the wafer carrier includes a permanent magnet. The wafer chuck includes an electromagnet... raise the wafer against a gravity direction by flowing an electrical current through the electromagnet so that the wafer carrier is repelled from the wafer chuck
Implementation Method 2
The wafer chuck includes a first vacuum cavity and a second vacuum cavity. The wafer carrier includes a third vacuum cavity... the wafer, the wafer carrier, the wafer chuck and the vacuum plate are held together by the vacuum
Data Source
AI summary
A method of wafer handling includes providing a wafer on a wafer carrier on a wafer chuck on a vacuum plate. The wafer carrier includes a permanent magnet. The wafer chuck includes an electromagnet. The wafer is raised against a gravity direction by flowing an electrical current through the electromagnet so that the wafer carrier is repelled from the wafer chuck while the wafer remains on the wafer carrier. While keeping the wafer raised, wafer alignment is adjusted by moving the wafer chuck, the wafer carrier or both. The electrical current is reduced to zero so that the wafer carrier contacts the wafer chuck. The wafer is connected to the vacuum plate via a first vacuum cavity of the wafer chuck and a third vacuum cavity of the wafer carrier. The wafer carrier is connected to the vacuum plate via the second vacuum cavity of the wafer chuck.